Download MBBS Anesthesia Mnemonic Short Book

Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Anesthesia Mnemonic Short Book

I.
ANESTHETIC EQUIPMENT & MONITORS

HISTORY OF ANESTHESIA
? Dioscorides ? used the term anesthesia
? Oliver Wendell Holmes ? 1846 ? termed anaesthesiology
? William T. G. Morton (The father of modern anaesthesia) ? October 16, 1846 (World Ether day)
demonstrated general anesthetic effects of ether.
? Carl Koller-1884- introduced cocaine as an ophthalmic anesthetic
? Niemann-1860- introduced cocaine as a local anesthetic
? Joseph Priestley ? produced Nitrous oxide- 1772
? Horace Walls: demonstrated use of Nitrous oxide for tooth extraction-1844
? On December 21, 1846, Robert Liston performed first surgical operation under ether anesthesia
? W. E. Clarke in 1841 administered anesthesia for a dental extraction [not made widely noted]
? August Bier- 1898-first spinal anesthesia/ father of spinal anesthesia
? Simpson: first to use chloroform
? John Lundy first used IV anesthetic thiopentone -1934
? Ferdinand Cathelin ? 1901 ? caudal epidural anesthesia
? Fidel Pages ? 1921 ? Lumbar epidural anesthesia
? Alexander Wood-1855 ? invented needle & syringe
? Harold Griffith- 1942 ? used curare
? Lofgren-1943- introduced Lidocaine
? John Lundy & Ralph waters: coined 'balanced anesthesia'
? Ketamine: first used by Domino & Corsen
? Succinyl choline: synthesized by Bovet
? First Boyle's machine: Edmund Gaske Boyle in 1917
? First endotracheal intubation: Ivan Magill
? First nasal intubation: Stanlers Rowbothon


Preoperative Physical Status Classification of Patients According to the American Society of
Anesthesiologists

Class
Definition
P1
A normal healthy patient
P2
A patient with mild systemic disease (no functional limitations)
P3
A patient with severe systemic disease (some functional limitations)
P4
A patient with severe systemic disease that is a constant threat to life (functionality incapacitated)
P5
A moribund patient who is not expected to survive without the operation
P6
A brain-dead patient whose organs are being removed for donor purposes
E
If the procedure is an emergency, the physical status is followed by "E" (for example "2E")

American Society of Anesthesiologists Physical Status Classification

ASA 1
Healthy patient without organic, biochemical, or psychiatric disease
ASA 2
A patient with mild systemic disease, e.g., mild asthma or well-controlled hypertension. No
significant impact on daily activity. Unlikely to have an impact on anesthesia and surgery
ASA 3
Significant or severe systemic disease that limits normal activity, e.g., renal failure on dialysis
or class 2 congestive heart failure. Significant impact on daily activity. Probable impact on
anesthesia and surgery
ASA 4
Severe disease that is a constant threat to life or requires intensive therapy, e.g., acute
myocardial infarction, respiratory failure requiring mechanical ventilation. Serious limitation
of daily activity. Major impact on anesthesia and surgery
ASA 5
Moribund patient who is equally likely to die in the next 24 hours with or without surgery
ASA 6
Brain-dead organ donor

---

THE ANESTHESIA MACHINE

PNEUMATIC SYSTEM

High pressure system
Intermediate pressure system
Low pressure system
? Receives gases from the
? Receives gases from the pressure regulator or
Consists of flow
cylinder at high, variable
the pipeline inlet to the anesthesia machine.
meters
pressures and reduces to
? Includes master switch, pipeline inlet
lower, constant pressures
connections, pipeline pressure indicators, piping,
? Includes hanger yokes,
gas power outlet, O2 pressure failure devices, O2
pressure indicators and
flush, additional pressure regulator & flow
pressure regulators
control valves

? The high pressure system is a cylinder, pressure regulator and yoke assembly.
? The intermediate pressure system is from yoke of assembly to flow control valve
? Low pressure system is downward from the flow control valve to common gas outlet

GAS SUPPLY
Pipeline inlets
? Oxygen, nitrous oxide, and often air are delivered to the operating room through a piping network
? The tubing is color coded and has diameter index safety system fitting that prevents incorrect hose
attachment.
Cylinder inlets
? Cylinders are attached to the machine via hanger-yoke with a pin index safety system to prevent errors.
? Cylinder pressure is usually measured by a Bourdon pressure gauge.
? A flexible tube within this gauge straightens when exposed to gas pressure, causing a gear mechanism to
move a needle pointer.
Flow Control Circuits
Pressure Regulators
? To reduce the cylinder gas pressure to 45-47 psig before it enters the flow valve.
? Oxygen is reduced to 20 psig and nitrous oxide is reduced to 38 psig.
Oxygen Supply Failure Protection Devices
? Safety devices sense oxygen pressure via a small "piloting pressure" line that may be derived from the gas
inlet or secondary regulator.
? Proportionately reduce the pressure of nitrous oxide and other gases except for air.
? They completely shut off nitrous oxide and other gas flow below a set minimum oxygen pressure (eg, 0.5
psig for nitrous oxide and 10 psig for other gases).
Flow Valves & Meters
? Gas lines proximal to flow valves are in the high-pressure circuit
? Gas lines between the flow valves and the common gas outlet are part of the low-pressure circuit
? To reduce the risk of providing a hypoxic gas mixture in case of leak, oxygen flowmeters are always
positioned downstream to all other flowmeters (nearest to the vaporizer).
Minimum Oxygen Flow
? The oxygen flow valves deliver a minimum flow of 150 mL/min.
? Some machines are designed to deliver minimum flow or low-flow anesthesia (< 1 L/min) and have minimum
oxygen flows as low as of 50 mL/min (eg, Datex-Ohmeda Aestiva/5)

Oxygen/Nitrous Oxide Ratio Controller
? Ensure a minimum oxygen concentration of 21-25%.
? Does not affect the flow of a third gas (eg, air, helium, or carbon dioxide).

---

Oxygen Analyzers
? GA should never be administered without an oxygen analyzer in the breathing circuit.
? Three types are available: polarographic (Clark electrode), galvanic (fuel cell), and paramagnetic.

DELIVERY OF MEDICAL GASES
PIN INDEX SAFETY SYSTEM [PISS]
? Inter link between the anesthesia machine and gas cylinder.
? In high pressure system [valve outlets of cylinders]
? High pressure (H) cylinders are made of Molybdenum Steel.
? Chromium is added to decrease the weight of cylinders.
? Aluminium cylinders are MRI compatible
? Gas pipes are made of seamless copper tubing

Gases
Entonox
Air
CO2 > 7.5%
Oxygen
CO2 < 7.5%
N2O
Cyclopropane
Pin index
Single central hole
1,5
1,6
2,5
2,6
3,5
3,6

Causes of failure of PISS:
? D/t multiple washers placed between the cylinder and yoke, which prevents proper engagement of the pins
and holes.
? Also ineffective if yoke pins are damaged or the cylinder is filled with the wrong gas.
DIAMETER INDEX SAFETY SYSTEM [DISS]
? In low pressure system & in outlets of central piping systems.
COLOUR CODING SYSTEM
Cylinder
Colour
N2O
Blue (Liquid form)
Cyclopropane
Orange
Oxygen
Black body with white shoulder (International code), Green (USA
code)
Thiopentone
Yellow
CO2
Grey
Entonox (O2 & N2O in equal
Blue body with blue and white shoulder
volumes)
Halothane
Amber (Purple- Red)
Air
Grey body with Black & white shoulder
N2
Black
Helium
Brown

OXYGEN DELIVERY SYSTEMS
Fixed performance masks
? Patient receives a constant inspired oxygen concentration (FiO2) despite any changes in minute
? Ventilation.
? These include:
o
Closed or semi-closed anaesthetic breathing systems with a reservoir bag, attached to
o
anaesthetic machine with pressurised gas supply.
o
Head boxes for neonates
o
High Air Flow Oxygen Enrichment (HAFOE) Devices e.g. Venturi mask, delivers an inspired
o
oxygen concentration between 24% and 40%.
? Venturi Mask
o
High flow delivery system
o
Flow rate b/w 4 - 12 L/min
o
FiO2 can be set specifically with different flow rate and air ports
o
FiO2 can be 24, 28, 31, 35, and 40%

---

o
COPD patient that requires specific oxygen concentrations to administer high FiO2
but not
o
too high such that the hypoxic drive to breath is blunted; titrate to keep saturation about 88%.

Variable performance masks/devices
? The oxygen concentration delivered depends on patient minute ventilation, peak inspiratory flow rate and
oxygen flow rate.
? Examples:
o
Nasal Prongs:
Low flow delivery system, > 6 L/min cause nasal mucosal drying
Flow rate: 1 - 6 L/min
FiO2 starts at 24% for 1L/min and increases 4% for each L/min up to 44% for 6 Lmin
Well tolerated
Use: minimal or no respiratory distress or oxygenation problem
o
Nasal cannula:
These do not increase dead space.
Deliver 100% oxygen, but because the patient also breathes room air, the oxygen
concentration ultimately delivered to the alveoli ranges from 24% to 44%.
Inspiratory oxygen concentration depends on the flow rate
No rebreathing occurs.
o
Nasal catheters, 8FG
Can be inserted into the nose as far as the pharynx
A gas flow of 150m1/kg/min gives an inspired oxygen concentration of 50% in
children less than 2 years
No rebreathing occurs.
o
Simple (Hudson) Face Mask (Rebreather)
Have a small dead space.
There is usually a small amount of rebreathing.
Low flow delivery system
Flow rate b/w 5 - 8 L/min
FiO2: 5 - 6 is 40%, 6 - 7 is 50%, 7 - 8 is 60%
Mask doesn't need tight seal
Use: as per nasal prongs but require higher concentrations
BREATHING SYSTEMS
Insufflation
? Blowing of anesthetic gases across a patient's face.
? Avoids direct connection between a breathing circuit and a patient's airway.
? Valuable during pediatric inductions with inhalation anesthetics.
? There is no rebreathing of exhaled gases if the flow is high enough.
? Disadvantage: Ventilation cannot be controlled.

Open-Drop Anesthesia
? A highly volatile anesthetic--most commonly ether or halothane--is dripped onto a gauze-covered mask
(Schimmelbusch mask) applied to the patient's face.
? The vaporization lowers mask temperature, resulting in moisture condensation and a drop in anesthetic
vapor pressure
? May be used in locations or situations in which compressed medical gases are unavailable

Draw-Over Anesthesia
? In its most basic application, air is drawn through a low-resistance vaporizer as the patient inspires.
? Patients spontaneously breathing room air and a volatile, halogenated agent (nitrous oxide is never used
with draw-over devices) often manifest an oxygen saturation (Sp02) < 90%

---

? The devices can be fitted with connections and equipment that allow intermittent positive-pressure
ventilation (IPPV) and passive scavenging, as well as continuous positive airway pressure (CPAP) and positive
end-expiratory pressure (PEEP).

Properties of Draw-Over Devices
? Portable
? Robust
? Low resistance to gas flow
? Usable with any agent
? Controllable vapor output

Semi Closed Breathing System
Mapleson System
Mapleson A / Magill system
? Efficient for spontaneous ventilation because fresh gas flow
Modified variant: LACK system
equal to minute volume is sufficient to prevent rebreathing
? Most popular & widely used.
? Poor choice during controlled ventilation.
? Enclosed Magill system is a modification that improves
efficiency.
? Coaxial Mapleson A (Lack breathing system) provides waste-gas
scavenging.
? Flow rate : about 5 L/min
Mapleson C system/ Water's system
Post operative recovery
Mapleson D system
Most efficient for controlled ventilation, since fresh gas flow forces air
away from patient and towards pressure relief valve.
Mapleson E system/Ayre's T piece
Primarily used in infants & young children. Main advantage of T piece is
system
absence of resistance to expiration, a factor of crucial importance to
children
Mapleson's F system/ Jackson- Rees
Popular in pediatric anesthesia, requires 2-3 times minute ventilation.
modification of Ayre's T piece.
Efficiency of system with spontaneous respiration: A>D&E>C>B
Efficiency of system with IPPV : D&E> B > C > A
Mapleson B & C are more efficient than Mapleson A during IPPV
Most commonly used version of Mapleson-D: Bain Coaxial system


Mapleson
Other Names
Required Fresh Gas Flows
Class
Spontaneous
Controlled
A
Magill attachment
Equal to minute ventilation (80
Very high and difficult to predict
mL/kg/min)
B
2 x minute ventilation
2-21/2 x minute ventilation
C
Waters' to-and-fro
2 x minute ventilation
2-21/2 x minute ventilation
D
Bain circuit
2-3 x minute ventilation
1-2 x minute ventilation
E
Ayre's T-piece
2-3 x minute ventilation
3 x minute ventilation (I:E =1:2)
F
Jackson-Rees'
2-3 x minute ventilation
2 x minute ventilation
modification

Fresh Gas Flow = 1.5 times minute volume for controlled ventilation and 2.5 times of minute volume for
spontaneous ventilation

---

Characteristics of Breathing Circuits

Insufflation and Open Drop
Mapleson
Circle
Complexity
Very simple
Simple
Complex
Control of anesthetic depth
Poor
Variable
Good
Ability to scavenge
Very poor
Variable
Good
Conservation of heat and humidity
No
No
Yes
Rebreathing of exhaled gases
No
No
Yes

Closed Breathing System/ Rebreathing system
? It is a circle system in which the CO2 is absorbed by soda lime and the exhaled gases can be reused.
? Eliminates exhaled CO2.
? CO2 absorbents:
Sodalime:
o 94% of Ca (OH)2 + 5% NaOH + 1% KOH + 0.2% silica + 14-19% moisture.
o Sodalime is contraindicated with chloroform & trilene (forms phosphogene, a neuro poisonous
gas)
o Disadvantages:
o Forms Carbon monoxide
o With sevoflurane, forms compound-A (penta fluoro isopropenyl fluoro methyl ether), But
sevoflurane is not contraindicated with sodalime
o Possibility of fire in breathing circuit
Baralyme:
o 80% of Ca (OH)2 + 20% BaOH + <1% KOH + moisture
Amsorb: Ca(OH)2+ CaCl2 + CaSO4 & polyvinylpyrrolidone
o Disadvantage: very costly, less CO2 absorptive capacity [CO2 absorption: soda lime> barylime>
amsorb.

NOTE: Compound-A formation occurs more with barylime than sodalime

Comparison of Soda Lime and Barium Hydroxide Lime

Soda Lime
Barium Hydroxide Lime
Mesh size
4-8
4-8
Method of hardness
Silica added
Water of crystallization
Content
Calcium hydroxide, Sodium hydroxide &
Barium hydroxide
Potassium hydroxide
Calcium hydroxide
Usual indicator dye
Ethyl violet
Ethyl violet
Absorptive capacity (liters of
14-23 [231/100gm]
9-18 [10.2 1/100gm]
CO2/100 g)

NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH (NIOSH)
? Recommends limiting the room concentration of nitrous oxide to 25 ppm and halogenated agents to 2 ppm
(0.5 ppm if nitrous oxide is also being used)
? The vacuum control valve on an active system should be adjusted to allow the evacuation of 1015 L of waste
gas per minute.

Essential Safety Features on a Modern Anesthesia Workstation.
Essential Features
Purpose
Diameter Index Safety System (DISS) with
Prevent incorrect pipeline attachments; detect
pressure gauges, filter, and check valve
failure, depletion, or fluctuation
Pin index safety system for cylinders with
Prevent incorrect cylinder attachments; provide
pressure gauges, and at least one oxygen cylinder
backup gas supply; detect depletion
Minimum oxygen/nitrous oxide ratio controller
Prevent delivery of less than 21% oxygen
device (hypoxic guard)

---

Oxygen failure safety device (shut-off or
Prevent administration of nitrous oxide or other
proportioning device)
gases when the oxygen supply fails
Oxygen must enter the common manifold
Prevent hypoxia in event of proximal gas leak
downstream to other gases
Oxygen concentration monitor and alarm
Prevent administration of hypoxic gas mixtures
Automatically enabled essential alarms and
Prevent use of the machine without essential monitors
monitors (eg, oxygen concentration)
Vaporizer interlock device
Prevent simultaneous administration of >1 volatile
agent
Capnography and anesthetic gas measurement
Guide ventilation; prevent anesthetic overdose
Oxygen flush mechanism that does not pass through
Rapidly refill or flush the breathing circuit
vaporizers
Breathing circuit pressure monitor and alarm
Prevent pulmonary barotrauma and detect
sustained positive, high peak, and negative airway
pressures
Exhaled volume monitor
Assess ventilation and prevent hypo- or
hyperventilation
Pulse oximetry, blood pressure, and ECG monitoring
Provide minimal standard monitoring
Mechanical ventilator
Control alveolar ventilation
Scavenger system
Prevent contamination with waste anesthetic gases


ASSESMENT OF AIRWAY
The 1-2-3 test:
? On opening the mouth, one should insinuate one finger in the temporo mandibular joint.
? There should be atleast two finger breadths distance between his incisors.
? There should be atleast three finger breadths distance between chin and thyroid cartilage of the patient.
MALLAMPATI TEST:
? Devised by Mallampati & Samson-Young
? Widely used & simpler classification of the pharyngeal view.
? Patient is made to sit upright, open his mouth wide and protrude his tongue.
? Failure to visualize posterior pharyngeal walls indicate difficult airway establishment.
o
Class: I- Uvula, Faucial pillars & soft palate visible.
o
Class: II- Faucial pillars & soft palate visible
o
Class: Ill- Soft palate & Hard palate visible
o
Class: IV- Only hard palate visible

Thyromental distance
? Normal thyromental distance is > 6.5 cms.
? If < 6cm ? intubation is difficult

AIRWAY MANAGEMENT

NONDEFINITIVE AIRWAY MANAGEMENT
? Foreign body removal: blind finger sweep for foreign body is acceptable in adults but is NOT acceptable i
pediatric cases.
? Maintenance of C-spine control imperative in trauma
? Maneuvers:
o
Head tilt - chin lift: NOT acceptable with possible C-spine injury
o
Jaw thrust - chin lift: acceptable with possible C-spine injury
o
Heimlick
? Oropharyngeal Airway
o
Use: temporary ventilation of unconscious patient while preparing to intubate

---

o
Not be tolerated by conscious patient b/c gag reflex and produces vomiting
o
Proper size: corner of mouth to external auditory canal
? Nasopharyngeal Airway
o
Use: temporary airway management in pt who would not tolerate an oropharyngeal airway or if it is
difficult to insert (trismus, mouth trauma, etc); less likely to induce vomiting
? Jet Insufflation (Needle Cricothroidotomy)
o
Short term oxygenation until more definitive AW can be established
? Other
o
Esophageal Obturator AW (EOA), Esophogastric Tube AW (EGTA), Pharygotracheal Lumen AW (PTLA),
Esophageal Tracheal Combitube, (ETC)
DEFINITIVE AIRWAY MANAGEMENT
? Endotracheal Intubation
o
Indications:
For supporting ventilation in patient with pathologic disease:
Upper airway obstruction,
Respiratory failure,
Loss of consciousness
For supporting ventilation during general anaesthesia (most common):
Type of surgery:
Operative site near the airway,
Thoracic or abdominal surgery,
Prone or lateral surgery,
Long period of surgery
Patient has risk of pulmonary aspiration
Difficult mask ventilation
Tracheal Tube
? Used to deliver anesthetic gases directly into the trachea and allow the most control of ventilation and
oxygenation.
? Us are most commonly made from polyvinyl chloride.
? The shape and rigidity of TTs can be altered by inserting a stylet.
? Murphy tubes have a hole (the Murphy eye) to decrease the risk of occlusion should the distal tube opening
abut the carina or trachea.
? Uncuffed tubes are usually used in children to minimize the risk of pressure injury and postintubation croup.
Airway Equipment for Pediatric Patients

Premature
Neonate
Infant
Toddler
Small
Large Child
Child
Age
0-1 month
0-1
1-12
1-3 years
3-8 years
8-12 years
month
months
Weight (kg)
0.5-3
3-5
4-10
8-16
14-30
25-50
Tracheal (ET)
2.5-3
3-3.5
3.5-4
4-4.5
4.5-5.5
5.5-6
tube (mm i.d.)
(cuffed)
ET depth (cm
6-9
9-10
10-12
12-14
14-16
16-18
at lips)
Suction
6
6
8
8
10
12
catheter (F)
Laryngoscope
00
0
1
1.5
2
3
blade
Mask size
00
0
0
1
2
3
Oral airway
000-00
00
0 (40 mm)
1 (50 mm)
2 (70 mm)
3 (80 mm)

---

Laryngeal
--
1
1
2
2.5
3
mask airway
(LMA)
Confirmation of placement:
? Is chest rising? Does reservoir bag fill?
? What is the pulsox?
? Is the tube fogging up?
? Listens over lung fields and epigastrium
? End - Tidal CO2
? CXR: tip should be 1/2 way b/w thoracic inlet and carina (at level of aortic knob)

Oral Tracheal Tube Size Guidelines
Age
Internal Diameter
Cut Length (cm)
Full-term
(m
3. m
5 )
12
in
C fa
hiln
dt
4 + [ Age/4 ]
14 + [ Age/2 ]
Adult
Female
7.0-7.5
24
Male
7.5-9.0
24

? Nasotracheal Intubation
o
Requires a spontaneously breathing patient
o
Good for pt with tightly clenched teeth, unstable C-spine injury
o
Contraindications: apneic patient, severe maxillofacial fractures, suspected basilar skull fracture (racoon
eyes, battle signs, ottorhea, rhinorhea, hemotympanum, nasal fracture)
? Surgical Cricothryoidotomy: NOT recommended for children < 12yo b/c of potential damage to the cricoid
cartilage which is the only circumferential support to the upper trachea
? Tracheostomy: time consuming but indicated for disrupted larynx or cervical trachea
OTHERS:
C-spine Immobilization
o Must protect C-spine
o Loosening of hard collar to allow for movement of the mandible will greatly facilitate visualization of the
cords with minimal cervical mobility
Assume a full stomach
o Use sellick's maneuver to occlude the esophagus and decrease aspiration
o Also helps to visualize cords
o BURP to help visualize cords: Push Back and Up with the Right Pressure
Choose a method of intubation
o Rapid Sequence Induction (RSI) is easiest and most popular method and should be used unless a difficult
airway is expected where there is suspicion that both intubation and bagvalve-mask ventilation after
paralysis may be difficult.
o Awake oral intubation: preferred method if difficult airway suspected
o Unconscious patients for whatever reason (even cardiac arrest) do NOT require pretreatment, induction, or
paralysis
NOTE:
o Gag reflex is an unreliable indicator of airway reflexes and should not be used.
o BURP MANEUVER: Manipulation of the thyroid cartilage, to improve laryngoscopic view
o SELLICK'S MANEUVER: Pressure on the cricoid ring to occlude esophagus, to decrease aspiration.
o Use the cricoid ring because it is the only complete tracheal ring.

---

LARYNGEAL MASK AIRWAY
Discovered by Dr.Archie Bain in 1980
Indications
Contraindications
? To facilitate ventilation & passage of & tube in
? Oropharyngeal abscess or mass
patient
? High risk of aspiration
? with a difficult airway
? Pregnancy
? Difficult airway management during CPR
? Pharyngeal obstruction
? Difficult intubation is anticipated
? Low pulmonary compliance
Advantage
Disadvantage
? Easy to insert
? Does not prevent aspiration
? Does not require laryngoscope & muscle relaxants
? High incidence of laryngospasm &
? Can be used in cervical injuries
bronchospasm
? Protects the larynx from pharyngeal secretions (but
not gastric regurgitation)
? Aids in ventilation during fiberoptic bronchoscopy as
well as placement of the bronchoscope.


Advantages & Disadvantages of the LMA compared with Face Mask Ventilation or Tracheal Intubation


Advantages
Disadvantages
Compared with
Hands-free operation
More invasive
face mask
Better seal in bearded patients
More risk of airway trauma
Less cumbersome in ENT surgery
Requires new skill
Often easier to maintain airway Protects
Deeper anesthesia required Requires some TMJ
against airway secretions Less facial nerve
mobility
and eye trauma Less operating room
N2O diffusion into cuff
pollution
Multiple contraindications
Compared with
Very useful in difficult intubations
Increased risk of gastrointestinal aspiration
tracheal
Less tooth and laryngeal trauma
Less safe in prone or jackknife positions
intubation
Less laryngospasm and bronchospasm Does
Limits maximum PPV
not require muscle relaxation Does not
Less secure airway
require neck mobility
Greater risk of gas leak and pollution Can cause
No risk of esophageal or endobronchial
gastric distention
intubation

ROCEDURE OF INTUBATION

? Preparation: good oxygenation, check equipment, explain to patient
? Anesthetize the airway: 4cc 4% lidocaine spray liberally with xylocaine spray just before
? Sedate the patient with
o
Midazolam 1 - 2mg
o
Fentanyl 50 - 100ug
o
Propofol
o
Ketamine
o
Thipentothal
o
Etomidate

---

TERIA FOR INTUBATION

Subjective Criteria
Objective Criteria
Airway obstruction real or impending (epiglotitis,
Oxygenation (Pa02 measures oxygenation)
burn, tumors, etc)
? PaO2 < 70 mmHg with FiO2 at least 70%
? A - a gradient > 350 mmHg (normal 15, up to 37
w/ age)
Aspiration real or impending (decreased LOC, drug
Ventilation (PCO2 measures ventilation)
OD, etc)
? PaCO2 > 60 mmHg in normal adults (not
? COPD)
? RR > 35/min in adults
? PaCO2 > 35 mmHg in status asthmaticus
Clinical respiratory failure (tachypnea, tachycardia,
Mechanics
AMU, indrawing, cyanosis, diaphoresis, decreased
? Vital capacity < 15 ml/kg (normal is 70
LOC, pulsus paradosus)
Tracheal bronchial toilet (unable to clear
secretions; COPD w/ pneumonia)
Shock not responsive to medical management w/I 30
min (resp muscles may use up to 25% of cardiac
output; septic shock is an example)
Anesthesia indications
LARYNGOSCOPY

Direct laryngoscopy:Laryngoscope is inserted into the mouth on the right side and flipped to the left to trap and
move the tongue out of the line of sight, and, depending on the type of blade used, inserted either anterior or
posterior to the epiglottis and then lifted with an upwards and forward motion.
Indirect laryngoscopy: performed whenever the provider visualizes the patient's vocal cords by fiberoptic
bronchoscopes, video laryngoscopes, fiberoptic stylets and optically-enhanced laryngoscopes.


Laryngoscope: consists of a handle (Patil-Syracuse handle) & blade
Types of blades:
Curved blade
Mac Intosh type
Used in adults
Straight blade
Miller type
Used in children & in adults with difficult airway

Size markings for laryngoscopes:
000 Small premature
00
in
P f
r a
e nt
m
ature infant
0
Neonate
1
Small child
2
Child
3
Adult
4
Large adult
5
Extra large adult


PATIENT MONITORS
Cardiac Monitoring
Central Venous Pressure Monitoring:
? Normal CVP is 6-8mm of Hg
? Monitoring of JVP / CVP is done from Rt. Internal jugular vein (valveless vein).
? Pulmonary artery catheterization is done by Swan Ganz catheter.

---

? Swan Ganz catheter measures mixed venous pressure:
o
Pressure in right atrium (0-8 mm of Hg)
o
Pressure in right ventricle (15 ? 25/0-8mm of Hg)
o
Pressure in pulmonary artery (15-25/5-15 mm Hg)
o
Pulmonary capillary wedge pressure (4 -12 mm Hg)
o
Left atrium (4-12mm Hg).
? The best indicator for tissue perfusion or cardiac output is mixed venous O2 saturation.
? Best clinical guide for cardiac output is urinary output.

Transesophageal Echocardiography:
? Most sensitive for wall motion abnormalities and to detect ischemia and air embolism during intraoperative
period.
? For detecting arrhythmias in ECG lead II is preferred.
? For detecting ischemia in ECG lead V5 is preferred.
? Inferior wall MI shows abnormality in lead II,III and aVF.

BP Monitoring:
? For invasive BP monitoring, radial artery is most preferred.
? For radial artery cannulation, Allen's test should be performed to assess the patency of ulnar artery.
? Allen's Test:
o
Hand circulation is stopped by occluding both radial and ulnar arteries.
o
The pressure over ulnar artery is released while maintaining pressure on radial artery.
o
Note the return of normal color of palm.
o
If color returns to normal in < 7 sec, then radial artery cannulation can be done.
o
If refill time is >15 sec then radial artery cannulation is contra-indicated.
o
7 ? 14 sec is borderline.

Respiratory Monitoring
Pulse Oximeter:-
? It is used to detect hypoxia in intra ? operative and post ? operative period.
? Pulse oxymeter measures percentage saturation of oxygen.
? The normal O2 saturation is 98%
? Oximetry depends on the observation that oxygenated and reduced hemoglobin differ in their absorption of
red and infrared light (Lambert?Beer law)
? Oxyhemoglobin (HbO2) absorbs more infrared light (960 nm)
? Deoxyhemoglobin absorbs more red light (660 nm) and appears blue or cyanotic to the naked eye.
? Change in light absorption during arterial pulsations is the basis of oximetric determinations.
? Following factors lead to inaccurate reading in pulse oxymeter:
o
Methemoglobin (shows 85% saturation always)
o
Carboxy hemoglobin (shows 95% saturation always, over read d/t Hb CO)
o
Fetal hemoglobin (at very high levels only)
o
Cyanide poisoning (higher values)
o
Anemia (lower values)
o
Hemoglobin S
o
Mal positioning of sensor
o
Poor peripheral pulsation
o
Skin pigmentation
o
Dyes- methylene blue, indocyanine green
o
Optical interference
o
Electrical interference
o
Nail polish & covering
? Severe Hyperbilirubinemia does not affect readings of pulseoximetry.

ETCO2 (capnography):
? The most commonly used type of capnograph plots Pco2 versus time.
? Capnography uses infrared light which is absorbed by CO2

---

Phases:

Expira
r t
a io
i n Inspiration.......

? Phase 0: inspiratory phase
? Phase I: dead space and little or no
n
o C
O2
? Phase II: mixture of alveolar and de
d a
e d space gas
? Phase III: alveolar plateau, with the
h peak representing end-expiratory (end-tidal) CO2 (PETCO2)
? Normal end-tidal PCO2 is approximat
a ely: 38 mmHg (35-45 mm Hg) or 5%
? Alpha angle is the transition from P
hase II to Phase III
? Beta angle is the transition from P
h
P a
h se III to Phase I (the start of inspiration)
? Additional phase IV (terminal upst
s roke before phase 0) may be seen in pregnancy.

Uses Of Capnography:
? Surest sign of correct intubation
? Diagnosis of malignant hyperthermia
i
? Detecting obstruction of Endotrach
c e
h al tube
? Indicates cardiac output
? Diagnoses pulmonary embolism


Persistent detection of CO2 by a capnograph is the best confirmation of tracheal place
c m
e ent of a TT (but it
cannot exclude bronchial intubatio
i n
o )
n
The earliest manifestation of bronc
n hial intubation is an increase in peak inspiratory pressure.
Blood Gas Analysis:
? The blood sample is taken from rad
a i
d a
i l artery preferably in a heparinized glass syringe
? Normal values on room temperature.
pH: 7.38 ? 7.42
Partial Pressure of air: 96 - 98 mm Hg
Partial Pressure of Coe: 35 ?45 m
m Hg
Bicarbonate: 24 ? 28 mEq / L
O2 saturation: 95 ? 98%
Base deficit: (-3 to + 3)

Neuro Muscular Monitoring
? M/c muscle used: Adductor pollicis supplied by ulnar nerve.
? Most accurate measurement for NM monitoring is orbicularis oculi supplied by facial nerve.
? Neuromuscular monitoring is done c
linically by train of 4.
o
4 stimuli are given each of 2 H
z
H with a gap of 0.Ssec between each stimuli and repe
p ated every 10-12 sec,
recording are taken.
o
Absence of Train 4 response means 75% receptors and blocked and is sufficient f
or
o most surgeries.
? Train of 4 is best utilized during maintenance phase of anesthesia.
? Succinylcholine (Depolarizing Blocker)

---

?
Tubocurarine non ? depolarizing blocker)




? Train of 4 differentiates depolarizing and non-depolarizing blockers
? Fading is property of non-depolarizing blockers.
? If a patient on succinyl choline shows fading, It is pathognomic of phase 2 block

Temperature Monitoring
? The most accurate measurement of core body temperature is provided by pulmonary artery.
? Tympanic membrane is the most accurate measure of brain temperature.
? Hypothermia is common thermal abnormality during anesthesia and temperature monitoring is mandatory.
?
Core body temperature > rectal temperature > surface temperature.
? Hypothermia is temperature < 35?C.
o
< 28 - 35?C is mild hypothermia
o
21 ? 27? C is moderate hypothermia
o
< 20? C is severe / profound hypothermia.
? Induced Hypothermia: O2 consumption and metabolic rate falls by 7% with each degree fall in temperature.
? Brain protection can be done for 10 mins at 30? C and for 60 mins at 15? C.
? Induced hypothermia protects against tissue ischemia during cardiac surgeries.

PNEUMOTACHOGRAPH
? A fixed-orifice flowmeter that can function as a spirometer.
? A parallel bundle of small-diameter tubes in chamber (Fleisch pneumotachograph) or mesh screen provides a
slight resistance to airflow.
? Pneumotachographs measure the flow according to the Venturi principle.
? Venturi principle: gas particles accelerate when their circulation zone is reduced. At the same
? time a drop in pressure occurs.
? 2 types of pneumotachographs: Fleisch and Lilly.
? The Lilly type measures the difference in pressure over before and after a membrane with known
? resistance.
? Fleisch types (more reliable) use a series of parallel capillaries.
? Wall mountable type of pneumotachograph- venturi pneumotachograph
Operating room air conditioning efficiency:
? In surgical theatres, the concentration of bacteriologically contaminated air borne particles in the operation
room averaged over any 5-min period should notexceedi80-per m3.
? Minimum of 15 changes/hour [20/hr is satisfactory]

POSITIONS
Trendelenburg's position
? Patient is supine on a bed with head end low (30-45?)
? FRC & VC decreased
? Preferred for abdominal surgery, Ryle's tube aspiration
? Increase ICP & lOP
Reverse trendelenburg
? Patient is supine on bed with head up
Fowler's position
? Head end of patient's bed is raised about 11/2 feet (46 cm)) & knee are
Sitting position
elevated
? Used for neurosurgery

---

Prone position
? Hypotension may occur
? Increased WOB, increased total lung compliane
Sim's position
? Position for PR examination
? Pt rests on left lateral side with right knee & thigh drawn well up above left
Rose position
? Tonsillectomy
Sniffing position
? Intubation (flexion at neck 5 extension at atlantooccipital joint)
Lithotomy position
? Used for gynaecolocial and urological procedure
? Maximum decrease in vital capacity
? Increased likelihood of aspiration
? Increased preload and cardiac output

Physiological Effects of Common Patient Positions.

Position
Organ System
Effects
Supine
Horizontal
Cardiac
Equalization of pressures throughout the arterial system; increased right-
sided filling and cardiac output; decreased heart rate and peripheral vascular
resistance.
Respiratory
Gravity increases perfusion of dependent (posterior) lung segments;
abdominal viscera displace diaphragm cephalad. Spontaneous ventilation
favors dependent lung segments, while controlled ventilation favors
independent (anterior) segments. Functional residual capacity decreases and
may fall below closing volume in older patients.
Trendelenburg
Cardiac
Activation of baroreceptors, generally causing decreased cardiac output,
peripheral vascular resistance, heart rate, and blood pressure.
Respiratory
Marked decreases in lung capacities from shift of abdominal viscera;
increased ventilation/perfusion mismatching and atelectasis; increased
likelihood of regurgitation.
Other
Increase in intracranial pressure and decrease in cerebral blood flow
because of cerebral venous congestion; increased intraocular pressure
in patients with glaucoma.
Reverse
Cardiac
Preload, cardiac output, and arterial pressure decrease. Baroreflexes
Trendelenburg
increase sympathetic tone, heart rate, and peripheral vascular resistance.
Respiratory
Spontaneous respiration requires less work; functional residual capacity
increases.
Other
Cerebral perfusion pressure and blood flow may decrease.
Lithotomy
Cardiac
Autotransfusion from leg vessels increases circulating blood volume and
preload; lowering legs has opposite effect. Effect on blood pressure and
cardiac output depends on volume status.
Respiratory
Decreases vital capacity; increases likelihood of aspiration.
Prone
Cardiac
Pooling of blood in extremities and compression of abdominal muscles
may decrease preload, cardiac output, and blood pressure.
Respiratory
Compression of abdomen and thorax decreases total lung compliance
and increases work of breathing.
Other
Extreme head rotation may decrease cerebral venous drainage and cerebral
blood flow.
Lateral
Cardiac
Cardiac output unchanged unless venous return obstructed (eg, kidney
decubitus
rest). Arterial blood pressure may fall as a result of decreased vascular
resistance (right side > left side).

---

Respiratory
Decreased volume of dependent lung; increased perfusion of dependent
lung. Increased ventilation of dependent lung in awake patients (no V/Q
mismatch); decreased ventilation of dependent lung in anesthetized patients
V/Q mismatch). Further decreases in dependent lung ventilation with
paralysis and an open chest.
Sitting
Cardiac
Pooling blood in lower body decreases central blood volume. Cardiac
output and arterial blood pressure fall despite rise in heart rate and
systemic vascular resistance.
Respiratory
Lung volumes and functional residual capacity increase; work of
breathing increases.
Other
Cerebral blood flow decreases.


POST ANESTHESIA DISCHARGE SCORING SYSTEM (PADSS)

Criteria
Points
Vital signs
2
Within 20% of preoperative baseline
Within 20-40% of preoperative baseline
1
> 40% of preoperative baseline
0
Activity level
Steady gait, no dizziness, at preoperative level
2
Requires assistance
1
Unable to ambulate
0
Nausea and vomiting
Minimal, treated with oral medication
2
Moderate, treated with parenteral medication
1
Continues after repeated medication
0
Pain: minimal or none, acceptable to patient, controlled with oral medication
Yes
2
No
1
Surgical bleeding
Minimal: no dressing change required
2
Moderate: up to two dressing changes
1
Severe: three or more dressing changes


VENTILATION MODES

Controlled
CMV
Fully or partially assisted
SIMV, SIPPV, A/C / PTV, PSV, SIMV + PSV, SIPPV + PSV

CONTROLLED MECHANICAL VENTILATION (CMV)
? Every breath is fully supported by the ventilator
? In classic control modes, patients were unable to breathe except at the controlled set rate
? In newer control modes, machines may act in assist-control, with a minimum set rate and all triggered
breaths above that rate also fully supported.

INTERMITTENT MECHANICAL VENTILATION (IMA)
? Patient triggered (PTV)/ Synchronous intermittent positive pressure ventilation (SIPPV)/assist control
(A/C):
o
Patient triggers a positive pressure inflation with each breath

---

? Synchronized Intermittent Mandatory Ventilation (SIMV):
o
Patient is able to trigger only a pre-set number of positive pressure inflations.

POSITIVE END EXPIRATORY PRESSURE (PEEP)
? Mechanical ventilatory maneuver of exerting a supra-atmospheric pressure in the lungs at end exhalation.
? PEEP is not a ventilator mode by itself.
? It is an adjunctive treatment that can be applied to all forms of mechanical ventilation; controlled, assisted
or spontaneous.
? Creation of a positive pressure at end exhalation increases the functional residual capacity (FRC) of the
lungs by decreasing the collapse of the small airways thus, reducing atelectasis.
? The major effect of PEEP on the lungs is to increase FRC.
? Recruitment (reexpansion) of collapsed alveoli occurs at PEEP or CPAP levels above the inflection point.
? Indications of PEEP:
o
Physiological PEEP
o
Pulmonary edema
o
Best value of PEEP is at which P02> 60mm Hg.
o
Shunt fraction is minimum & C.0 is minimally depressed
o
ARDS
o
Cardiothoracic surgery
? Significance:
o
Shifts the tidal volume to a more compliant portion of the pressure volume curve.
o
Prevents the intermittent loss of compliance during mechanical ventilation.
o
Reduces the work of breathing.
o
Capable of increasing arterial oxygenation.
? Hazards of inappropriate application of PEEP:
o
Impaired gas exchange
o
Decreased cardiac output, splanchnic and renal blood flow.

---

Key Contraindications of PEEP
? Pneumothorax without pleural catheter
? Intracranial hypertension
? Hypovolemia (unless concomitantly treated)
? Bronchopleural fistula
? Recent pulmonary resection surgery

Term
Description
Allodynia
Perception of an ordinarily nonnoxious stimulus as pain
Analgesia
Absence of pain perception
Anesthesia
Absence of all sensation
Anesthesia dolorosa
Pain in an area that lacks sensation
Dysesthesia
Unpleasant or abnormal sensation with or without a stimulus
Hypalgesia (hypoalgesia)
Diminished response to noxious stimulation (eg, pinprick)

---

Hyperalgesia
Increased response to noxious stimulation
Hyperesthesia
Increased response to mild stimulation
Hyperpathia
Presence of hyperesthesia, allodynia, and hyperalgesia usually
associated with overreaction, and persistence of the sensation after the
stimulus
Hypesthesia
Reduced cutaneous sensation (eg, light touch, pressure, or emperature)
(hypoesthesia)
Neuralgia
Pain in the distribution of a nerve or a group of nerves
Paresthesia
Abnormal sensation perceived without an apparent stimulus
Radiculopathy
Functional abnormality of one or more nerve roots
Preemptive analgesia
? Formulated by Crile.
? Involves the introduction of an analgesic regimen before the
onset of noxious stimuli, with the goal of preventing
sensitization of the nervous system to subsequent stimuli that
could amplify pain.
? Administration of long-lasting analgesics before surgery to help
to avoid the establishment of a sensitized state and result in
diminished postoperative pain.

---

II.
CLINICAL PHARMACOLOGY OF ANESTHETIC DRUGS

STAGES OF ANESTHESIA (Guedel's staging based on ether)
? Stage I: Analgesia:
o
Loss of pain sensation results from interference with sensory transmission in the Spinothalamic tract.
o
The patient is conscious and conversational.
o
Amnesia and a reduced awareness of pain occur as Stage II is approached.
? Stage II: Excitement:
o
The patient experiences delirium and possibly violent, combative behavior.
o
There is a rise and irregularity in blood pressure.
o
The respiratory rate may increase.
o
To avoid this stage of anesthesia, a short-acting barbiturate, such as thiopental, is given intravenously
before inhalation anesthesia is administered.
? Stage III: Surgical anesthesia:
o
Regular respiration and relaxation of the skeletal muscles occur in this stage.
o
Eye reflexes decrease progressively, until the eye movements cease and the pupil is fixed.
o
Surgery may proceed during this stage.
? Stage IV: Medullary paralysis:
o
Severe depression of the respiratory and vasomotor centers occurs during this stage.
o
Death can rapidly ensue unless measures are taken to maintain circulation and respiration.
CLASSIFICATION OF GENERAL ANESTHETICS
Inhalational agents
Intravenous agents
Gaseous
Volatile
Inducing agent
Slower acting
Nitrous
Alkanes:
Ethers: Ether,
Propofol
Benzodiazepines
oxide
Halothane
Enflurane,
Methohexitone
Dissociative anesthesia: Ketamine
Xenon
Desflurane,
Thiopentone
Neurolept analgesia: Fentanyl +
Isoflurane,
Etomidate
Droperidol
Sevoflurane
INHALATION ANESTHETICS
IMPORTANT FACTS:
? IDEAL GAS Obeys Charles, Boyle's & Avogadro's law
? Charles's law: at constant pressure V a T.
? Boyle's law: at constant temperature V a 1/P.
? Unitary hypothesis: all inhalation agents share a common mechanism of action at the molecular level.
? Meyer--Overton rule: Anesthetic potency of inhalation agents correlates directly with their lipid solubility.
? General anesthesia typically reduces both VO2 and VCO2 by about 15%.
? The greatest reductions are in cerebral and cardiac O2 consumption.
? Three factors affect anesthetic uptake:
Solubility in the blood
Alveolar blood flow
Difference in partial pressure between alveolar gas and venous blood.

MINIMAL ALVEOLAR CONCENTRATION
? MAC is alveolar concentration of an inhaled anesthetic that prevents movement in 50% of patients in
response to a standardized stimulus (eg:- surgical incision)
? MAC is a useful measure as it measures the potency of inhalational agents.
? 0.3 to 0.4 MAC is associated with awakening from anesthesia (MAC awake)
? There is 6% decrease in MAC per decade of age.

---

Anaesthetic
MAC (% atm)
Blood gas partition coefficient
Halothane
0.74
2.3
Enflurane
1.68
1.8
Isoflurane
1.15
1.4
Desflurane
6.0
0.42
Sevoflurane
2.05
0.69
Cyclopropane
9.2
0.44
Nitrous oxide
104
0.47
Trilene
0.2
9
Ether
1.92
12
Chloroform
0.8
8
Methoxyflurane
0.16
15

? MAC for nitrous oxide is 104%, and it must be given in a pressurized chamber due to safety considerations.

Factors Increasing MAC
Factors Decreasing MAC
Factors does not affect
MAC
? CNS metabolic activity
? CNS metabolic activity
? Thyroid disease
? CNS neurotransmission
? CNS neurotransmission
? Gender (M/F)
? CNS neurotransmitter
? CNS neurotransmitter levels
levels
? Down-regulation of CNS response
? Up-regulation of CNS
response
? Young patient
? Elderly patient
? Chronic alcohol abuse
? Acute alcohol intoxication
? Hypernatremia
? Hyponatremia
? Acute amphetamine
? Chronic amphetamine
poisoning
? Hypercalcemia, Hypokalemia
? Cocaine
? Hypo and hyperthermia
? Ephedrine
? L.A , I.V induction agents
? Opioids, Clonidine
? Anemia
? Lithium, Methyl dopa, Reserpine
? MAP < 40mm of Hg
? Pregnancy
? Hypoxia (pao2 < 40m of Hg) &
hypercarbia (paco2 > 90mg Hg)


PARTITION CO-EFFICIENT
? Measures the solubility of the gas.
? Blood gas partition coefficient: measures solubility of general anesthetic
? Oil-gas partition coefficient: measures anesthetic potency.


EFFECT OF INHALATIONAL AGENTS

Respiratory System
? All Inhalational agents are bronchodilators and depress the respiratory system.
? Maximum bronchodilation: Halothane (agent of choice in asthmatics)
? Maximum respiratory depression: Enflurane.
? Maximum blunting of ventilatory response is with halothane.

---

Cardiovascular System
? All inhalational agents decrease cardiac output except isoflurane and desflurane.
? Maximum decrease in C.O- halothane
? C.0 is best maintained by isoflurane because of reflex tachycardia.
? All inhalational agents are pulmonary vasodilators except N2O which is pulmonary vasoconstrictor
? All inhalational agents reduce mucociliary activity of airways except ether.
? Maximum inhibition of baroreceptor reflexes is with Halothane.
? All inhalational agents reduce BP except cyclopropane.
? Isoflurane is the agent of choice for controlled hypotension.
? Isoflurane is agent of choice for cardiac patients because of maintenance of C.O and minimum response on
baroreceptor reflexes.
? Maximum inhibition of myocardial contractility - Halothane.
? Halothane sensitizes the heart to arrhythmogenic action of adrenaline
? Halothane is contraindicated in patients with Pheochromocytoma

Central Nervous System
? All inhalational agents increase intracranial tension.
? Maximum increase in intracranial tension is with enflurane.
? Minimum increase in ICT is isoflurane and Desflurane < 6%
? Inhalational agent of choice for neurosurgeries is Isoflurane.

Kidneys
? Nephrotoxicity is d/t fluoride content.
? Anesthetics are fluorinated to make them non-inflammatory.
? Maximum fluoride content is seen in methoxyflurane (maximum nephrotoxicity)
? Methoxyflurane produces vasopressin resistance, polyuric renal failure
Others
? N2O can cause bone marrow suppression, Vitamin B12 deficiency and megaloblastic anemia
? All inhalational agents relaxes the uterus.
? Maximum uterine relaxation - halothane and thus halothane is agent of choice for internal version and
manual removal of placenta.
? Hyperglycemia is produced by ether, cyclopropane and desflurane.
? All inhalational agents increase intra ocular pressure
? All inhalational agents are good skeletal muscle relaxants except N2O.
? Maximim skeletal muscle relaxation is by ether
? Ether and cyclopropane are highly inflammable. Cautery should not be used with these agents.
? All inhalational agents undergo metabolism by oxidation.
? Halothane is metabolized by reduction and oxidation.

Extent of metaholism of inhalational anesthetics
? Methoxyflurane > 70% (maximum metabolism)
? Halothane
> 40%
? Enflurane
8%
? Sevoflurane
2-5%
? Isoflurane
< 2%
? Desflurane
< 0.05% (least metabolism)
? N2O does not undergo any metabolism

---

PHARMACOLOGY OF INDIVIDUAL AGENTS

NITROUS OXIDE (laughing gas)
? Has second gas effect during induction & diffusion hypoxia after discontinuation of anesthesia in recovery
phase.
? As N2O is used in high concentration (70-80%) it leads to entry of N2O in blood at a rate higher than minute
(1 lit/min) volume.
? N2O has low blood solubility. So it rapidly diffuse into alveoli & dilutes the alveolar air-Partial Pressure of O2
in alveoli is reduced i.e. diffusion hypoxia
? Diffusion hypoxia is prevented by administering 100% oxygen for 5-10 min after discontinuing N2O
? Poynting effect: Entonox (50% O2 & 50% N2O) & mixture of gases (O2 & N2O) keeps them in gaseous form.
? If another potent anesthetic eg. Halothane is added, it also will be delivered to the blood at a rate higher
than minute volume & the induction will be faster.
? N2O is a good analgesic but weak anaesthetic and poor muscle relaxant. Hence it is not a complete
anaesthetic.
? N2O has blood gas coefficient of 0.47 and has fast induction
? It has MAC value of 104; Hence Potency is low
? N2O is used as a carrier gas given in a mixture of 33% O2 and 66% N2O
? Contraindications for N2O :
o
Middle ear surgeries and tympanoplasty
o
Laparoscopic surgeries, Eye surgeries
o
Acute intestinal obstruction and volvulus
o
Microlaryngeal surgeries
o
Pneumothorax, pneumoperitonium
o
Pneumoencephalos.
? It should be avoided in patients with pulmonary hypertension
? Adverse effects: bone marrow depression (agranulocytosis, megaloblastic anemia) and even neurological
deficiencies (peripheral neuropathies and pernicious anemia).

ENTONOX
? 50-50 mixture of N2O & O2
? Cylinder is blue coloured with white shoulder
? Uses - analgesia for wound dressing, chest physiotherapy, removal of chest drains labour analgesia, & dental
surgery
? It is good analgesic (d/to N2O)

XENON
? Manufactured by fractional distillation of air
costly
? MAC 71% [more potent that NO]
? Blood gas partition coefficient
0.14 [emergence is rapid than with desflurane/propofol]
? Minimal cardiovascular & hemodynamic side effects
o
Cardio protective & Neuro protective
o
Non teratogenic
o
Not metabolized in liver/ kidney
o
No malignant hyperthermia
? Density of xenon 5.887g/dl (more than N2O & air)
o
Increases pulmonary resistance & breathing
o
Cautiously used in moderate to severe COPD, morbidly obese & premature infants

Advantages of Xenon (Xe) Anesthesia
Disadvantages of Xenon (Xe) Anesthesia
Inert (probably nontoxic with no metabolism)
High cost
Low blood solubility
Low potency (MAC = 70%)
Rapid induction and recovery
No commercially available anesthesia equipment
Environmentally friendly, Nonexplosive

---

HALOTHANE (2, bromo, 2 chloro, 1, 1, 1 trifluoroethane)
? Least expensive & least pungent.
? Potent anesthetic, no analgesia.
? Dissolve rubber and corrodes metals.
? Drager Narko test is done for halothane.
? Contains 0.01% thymol for stability.
? Decomposed by light but is stable in amber coloured bottles.
? 15-20% is metabolized.
? May persist in the liver upto 12 days & not given in same patient within 3 months (potent hepato toxic).
? Relaxes skeletal and uterine muscle & blood vessels.
? Not hepatotoxic in children and combined with its pleasant odor, suitable in children for inhalation
induction.
? Causes 5'H'
o
Malignant Hyperthermia,
o
Hepatitis (centrilobular necrosis) extremely rare (1 per 35,000 cases)
o
Hypotension
o
Hypercapnia
o
Heart rate decreases (myocardial depression)
? Decreases 10P, but ICT is increased
? Shivering & tremors common (H-shakes) in early post-operative period
? Myocardial depression of halothane is exacerbated by -blockers and calcium channel-
? blocking agents.
? The combination of halothane and aminophylline
serious ventricular arrhythmias.
Contraindications for halothane:
? Pregnancy because it increases the risk of post -partum hemorrhage
? Liver dysfunction & Previous use within 3 months: due to halothane hepatitis
? Hypovolemia & severe cardiac disease (aortic stenosis); due to negative ionotropic effect
? Pheochromocytoma & exogenous catecholamines administration as it sensitize heart to catecholamines.
Best uterine relaxant is Halothane followed by ether.
Best muscle relaxant is ether followed by halothane.

FLURANES
? Enflurane
Contraindicated in epilepsy
Increases cerebral blood flow, secretion of CSF, resistance to CSF flow & intra cranial pressure
High voltage high frequency EEG changes can progress to spike & wave pattern that culminates in frank
tonic clonic seizures.
This epileptiform activity is exacerbated by high anesthetic concentrations & hypocapnia, so
hyperventilation is not recommended to attenuate Enflurane induced intracranial hypertension.
? Isoflurane
AOC in neurosurgery
Causes coronary steal syndrome
Least effect on myocardial contractility [most cardio stable volatile agent]
? Enflurane & Halothane: myocardial depressants
? Desflurane: transient sympathetic activation, broken down to carbon monoxide by dry barium hydroxide
carbon monoxide poisoning.
? Sevoflurane
Sweet odour
Metabolized to HFIP [Hexa flour !so propyl]
Induction agent of choice in children
? Halothane and isoflurane: sensitizes the heart to circulating catecholamines (adr/NA)
? Seizures are seen in enflurane & desflurane (lesser extent)

---

HEPATOTOXICITY OF ANESTHETIC AGENTS:
? Depends on
o
Gender (Female> male)
o
Age (middle age adults)
o
Obesity
o
Enzyme induction
o
Prior anesthetic exposure
o
Genetics
? Hepatotoxicity of inhalational agents is due to TFA [Tri flour acetyl] metabolite.
? Therefore, hepatotoxicity is proportional to the percentage of metabolism.
? % metabolism: halothane (20%) > Sevoflurane (2-5%)> Enflurane (2-4%)> Isoflurane (0.2%)>desflurane
(0.02%)
? But sevoflurane does not cause hepatotoxicity because its metabolite is HFIP (not TFA)
NEPHROTOXICITY OF ANESTHETIC AGENTS:
? Methoxyflurane:
o
Most potent inhalation agent, but its high solubility and low vapor pressure limited its rate of induction
and emergence
o
Highly nephrotoxic (high fluoride content)
o
Causes polyuric (High output), vasopressin-resistant renal failure
o
Tendency of oxalate stone formation
? Prolonged use of Enflurane: Leads to significant fluoride production and nephrotoxicity.
? Though sevoflurane produces fluoride, nephrotoxicity is rare in usual therapeutic doses
? Halothane, Isoflurane Desflurane: fluoride production is negligible, Can be used in Renal failure.
? Halothane & Isoflurane decreases renal blood flow, GRF & urinary output but Desflurane do not.

TRICHLOROETHYLENE (TRILENE)
? It is potent nerve poison.
? Vth & VII th CN are most commonly involved
? Produces analgesia in distribution of 5th cranial nerve & relieves trigeminal neuralgia.
? It is not used in closed circuit (Soda lime ) because toxic product may be formed
? At 125?C or in presence of O2 as by cautery it decomposes into phosgene (COCl2) & Hcl
? Does not depress myocardium & respiration (like N2O)
? Not inflammable.
? Disadvantage : Sensitizes heart to adrenaline (Occasional dysrhythmia)
#
? Highly potent analgesic because MAC is low 17% (MAC
)
? Used for labour analgesia

ETHER
? Ether has slow induction with slow recovery and is very unpleasant.
? Induces laryngeal spasm and makes induction even slower.
? Stimulates salivary and bronchial secretions. So atropine pre medication is required.
? Highly inflammable and explosive, it should not be used when diathermy is needed in the airway
? Muscle relaxants need no to be used as ether itself produce excellent relaxation.
? Ether liberates catecholamines and tends to maintain blood pressure.
? No sensitization of myocardium to circulating catecholamines.
? It is a complete anaesthetic nearer to ideal anaesthetic.
? Ether does not affect the mucociliary action and is good bronchodilator.
? Ether has good anaesthetic, good analgesic, good skeletal muscle relaxant.
? Ether does not cause depression of myocardium but instead causes tachycardia and hypertension.
? Ether has highest instance of nausea and vomiting among inhalational agents.
? Ether causes hyperglycemia and is contraindicated in diabetes
? Guedel's 4 stages of anaesthesia were based on ether.
? Ether is safe in unskilled professionals and is very economical.

---

Preservatives
? Halothane: 0.01% thymol
? Ketamine: Benzethonium chloride
? Thiopentone: Anhydrous sodium carbonate (6%) & nitrogen gas
? Ether: propyl galate/ hydroquinone/ diphenylamine


NONVOLATILE ANESTHETIC AGENTS
PROPOFOL
Cardiovascular
Neurologic
Metabolic
? Depresses entricular
? Reduce neuronal
? The emulsion used as the vehicle for propofol
systolic function
damage by
contains soybean oil and egg lecithin and
? Vasodilatation results
depressing cerebral
supports bacterial growth; iatrogenic
from calcium channel
metabolism.
contamination leading to septic shock.
blockade.
? Decreases cerebral
? Currently available preparations contain EDTA,
? In patients undergoing
oxygen
metabisulfite, or benzyl alcohol as a
coronary artery bypass
consumption,
bacteriostatic agent.
surgery, it decreases
cerebral blood flow
? Because EDTA chelates trace metals,
mean arterial blood
and cerebral glucose
particularly zinc, serum zinc levels should be
pressure, stroke volume
use
measured daily during continuous infusions
and increases heart rate
? Hyperlipidemia may occur in infants and small
children

? Water-soluble phosphorylated prodrug: fospropofol [hydrolyzed by endothelial cell surface alkaline
phosphatases]
? Hypnotic agent associated with pleasant emergence and little hangover.
? 1% xylocaine is also given along with it to reduce pain on injection.
? Preferred agent for sedation and hypnosis and in particular for patients with altered level of consciousness.
? Anesthetic of Choice
o
Malignant hyperpyrexia
o
Day care surgery
o
Total IV anesthesia (used along with alfentanil)
? Has anti-oxidant, anti- emetic, anti convulsant, bronchodilator & anti pruritic property.
? The rapid recovery of neurologic status makes it a good sedative in ICU patients.
? Diprivan (1% formulation): contains 10% soya oil, 1.25% egg phophatide & 2.25 %glycerol.

PROPOFOL INFUSION SYNDROME-PRIS:
? Occurs if given at the rate of 4mg/kg/hour or more for 48hrs or longer.
? Lethal disorder as it interferes with mitochondrial oxidation.
? Features:
o
Acute refractory bradycardia leading to asystole
o
Metabolic acidosis
o
Rhabdomyolysis
o
Hyperlipidemia
o
Enlarged/fatty liver
o
Cardiomyopathy with acute cardiac failure, skeletal myopathy

THIOPENTONE
? Ultra short acting barbiturate used for induction.
? The duration of action of highly lipid-soluble barbiturates (thiopental, thiamylal, and
methohexital) is determined by redistribution, not metabolism or elimination.
? Although thiopental is highly protein bound (80%), its great lipid solubility and high nonionized fraction
(60%) account for maximal brain uptake within 30 s.

---

Actions:
CNS:
? Cerebro protective
? Decreases cerebral blood flow & intra cranial tension.
? Decreases cerebral O2 consumption & increases the perfusion pressure.
? Anti-analgesic (can produce hyperalgesia by reducing the threshold of pain)
? It has anticonvulsant / anti-epileptic property

Eye:
? Pupils first dilate & then constrict.
? Decrease in IOT
? Loss of eye lash reflex- sign of adequate induction
Musculo - skeletal system: Tremors, twitching, respiratory excitation including cough, hiccup
Respiratory system: Transient apnea, respiratory depression [double apnea], upper airway obstruction
Larynx: Laryngospasm & hiccups

Other Features:
? It is not a muscle relaxant.
? Has anti-thyroid properties because it has thiourilene structure.
? Ringer lactate should not be used for reconstitution as it gets precipitated with it.
? IV agent of choice for cerebral protection.
? It crosses BBB and Placental barrier

Complications:
? Induces ALA synthetase acute intermittent porphyria.
? Perivenous and IM injections cause tissue necrosis and ulcerations due to high alkalinity
? Intra-arterial injections lead to arterial spasm which is prevented by using 2.5% solution, injecting very
slowly and in incremental doses.
? Thiopentone should be avoided in asthmatics, hypotension, and shock, patients on Beta blockers,
hypokalemia, heart blocks, valvular stenosis and dystrophia myotonia.

METHOHEXITONE
? Ultra short acting barbiturate. More potent than thiopentone.
? Induces seizures and is the agent of choice for electroconvulsive therapy

ETOMIDATE
? Used to induce anesthesia.
? Hypnotic agent but lacks analgesic activity.
? Water solubility is poor, so etomidate is formulated in a propylene glycol solution.
? Induction is rapid, and the drug is short-acting.
? Only used for patients with coronary artery disease or CVS dysfunction, such as shock.
? Etomidate is hydrolyzed in the liver, no effect on the heart and circulation.
? Adverse effect: decrease in plasma cortisol and aldosterone levels due to inhibition of 11--ahydroxylase.

KETAMINE
? A short-acting, non barbiturate anesthetic
? Structural analogue of phencyclidine
? N-methyl-D-aspartate receptor (NMDA) a subtype of the glutamate receptor antagonist.
? Causes profound analgesia, dissociative anesthesia and catatonia
? Anesthesia of choice in shock.
? It is associated with emergence psychoto mimetic side effects "DISSOCIATIVE ANESTHESIA" (delirium,
illusions, hallucination) it is less common in children and pretreatment with lorazepam (drug of choice)
? Only IV anesthetic agent with both anesthetic and analgesic activity

---

It is a sympathetic stimulant
? Cardiac stimulation (sensitizes the heart to adrenaline)
Increased HR, BP, Oxygen demand & cardiac
output.
? Increases all pressure ABP, 10T, ICT
? Increased muscle tone
myalgia
? Potent bronchodilator AOC in bronchial asthma
? Upper airway reflexes are intact (beneficial in patients with either hypovolemic or cardiogenic shock as well
as in patients with asthma)
? Salivation is increased so anticholinergic (atropine )is always given in premedication
? Contraindicated in raised intracranial pressure & intracranial pathology with mass effect.
? Avoided in: CHF, coronary artery disease, hypertension, CVA & Arterial aneurysm.

FENTANYL
? More potent analgesic than morphine
? Rapid onset & rapid recovery so used for day care surgery
? Produces significant musculoskeletal rigidity (Wooden chest syndrome)
? Can be given in hepatic & renal disease
? Fentanyl "lollipop" is an effective method of producing analgesia and sedation.
? Provides rapid onset (10 min) of analgesia and sedation in children and adults
? Low molecular weight and high lipid solubility
transdermal absorption (fentanyl patch).
? Serum concentrations reach a plateau within 14-24 h of application and remain constant for 72 h.
? A high incidence of nausea and variable blood levels have limited the acceptance of fentanyl patches for
postoperative relief of pain.

ANESTHETICS CAUSING
Increased ICT
Sevoflurane, Desflurane, Isoflurane, Enflurane, Methoxyflurane, Halothane,
Ketamine, Nitrous Oxide (N2O), Althesin, Succinyl choline
Decreased ICT
Barbiturates, Cyclopropane, Droperidol, Etomidate, Lidocaine, Propofol
Increased IOT
Barbiturates, Cyclopropane, Etomidate, Succinyl Choline, Ketamine,N2O
Decreased IOT
Morphine, Thiopentone, Halothane, Hexamethonium, Trimethaphan
Increased BP
Ketamine, Pentazocine, Pancuronium
Bronchodilatation
(preferred in asthmatics)
Ketamine (most potent), Halothane, Promethazine, d-TC
Broncho spasmodic
(contraindicated in asthmatics):Ether, N2O,Thiopentone

Effects of Anesthetic Agents on Cerebral Physiology

Agent
Metabolic rate
Blood flow
Blood volume
Intracranial tension
Halothane
Isoflurane
Desflurane
Sevoflurane
Nitrous oxide
?
Barbiturates
Etomidate
Propofol
Benzodiazepines
Ketamine
Little or no effect
Opioids
Little or no effect
Lidocaine

? When combined with intravenous agents, nitrous oxide has minimal effects on CBF, CMR, and ICP.

---

PAIN ON INJECTION
? On intra arterial injection: Thiopental
? On intravenous injection
o
With Thrombophlebitis: Etomidate (80%)
o
Without Thrombophlebitis: Propofol (40%), Methohexitol (20%), Thiopental (10%)
? Incidence is greatly reduced if a large vein is used, if a small dose of lidocaine (10mg) is injected shortly
before.

ANAESTHETIC AGENTS OF CHOICE FOR VARIOUS CONDITIONS
Day care
Propofol
Ischemic heart disease
Etomidate
Congenital heart disease
-Left to right shunt
Isoflurane
-Right to left shunt
Ketamine
CH F
Ketamine
Shock
Ketamine
To produce deliberate hypotenion
Isoflurane
Asthma and COPD
Ketamine
Epilepsy
Thiopentone
For electroconvulsive therapy
Methohexitone
Thyrotoxicosis
Thiopentone
Cardiac surgery
Isoflurane
Neurosurgery
Isoflurane


? Liver disease:
o
Induction agent: Isoflurane (least effect on hepatic blood flow)
o
Relaxant: Cisatracurium, atracurium (unique nonhepatic metabolism)
? Renal Disease:
o
Induction agent: Isoflurane
o
IV anesthetics: thiopental & propofol.
o
Opioids ? Remifentanil, fentanyl, sufentanil
o
Relaxant: Cisatracurium, atracurium
? Renal Disease:
o
Induction agent: halothane, sevoflurane, ketamine
? Neurosurgery:
o
Total intravenous anesthesia (TIVA) is preferred ? propofol with opioids in anesthetic of choice.
o
Among volatiles, isoflurane is agent of choice
Anesthetic drugs contraindicated in
? Acute intermittent porphyria: Thiopentone
? Acute asthma & Acute intermittent porphyria (ATP) : Althesin (Steroidal)
? Renal failure: Methoxyflurane, Galamine, Morphine, Metocurine
? Hepatic Failure: Chloroform, Halothane

BALANCED ANESTHESIA

? Thiopental: induction
? N2O: amnesia
? Meperidine: analgesia
? Curare: muscle relaxation

---

DAYCARE / OUT PATIENT ANESTHESIA
General anesthesia
? Inducing agents: Propofol, Methohexital, Thiopentone, etomidate
? Muscle relaxant: Mivacurium (agent of choice) , Succinyl choline
? Analgesic: Alfentanyl, Remifentanyl, Fentanyl
? Volatile inhalation agent: Isoflurane, Sevo/Desflurane
? Total intravenous anesthetic technique: Propofol/ Remifentanil/ Alfentanil/ Sufentanil
? Switch technique: Induction with Propofol, maintenance with Isoflurane, Sevoflurane, change to Propofol or
Desflurane at the end for rapid emergence.

Monitored Anesthesia
? Initial sedation & anxiolysis with a Benzodiazepine (Midazolam) followed by Propofol then local anesthesia
? For breast biopsy, ophthalmic procedure & minor plastic surgery.

No Analgesia
= Halothane
Only Analgesia
= N2O
Profound Analgesia
= Ketamine
Best / Maximum analgesia
= Trilene

MUSCLE RELAXANTS

Directly acting
Neuro muscular blocking agent
Centrally acting agent
? Dantrolene
Depolarizing (Non-competitive):
Acts on cerebrospinal axis
? Quinine
? Succinyl choline/ Scoline/ Suxamethonium
without altering
? Decamethonium
consciousness
Non depolarizing (competitive):
? Benzodiazepine
? Gantacurium [Ultra-short acting]
? Mephensin
? Mivacurium [Short acting]
? GABA derivatives
? Vecuronium, Rocuronium, Atracurium,
as Baclofen
Cisatracurium [intermediate acting]
Others: Galamine, d-tubo curarine, Pancuronium,
Pipecuronium, Doxacurium

DIRECT ACTING SKELETAL MUSCLE RELAXANTS
? Dantrolene inhibits release of Ca2+ from sarcoplasmic reticulum, by inhibiting Ryanodine receptors.
? Dantrolene is DOC for malignant hyperthermia and neurolept malignant syndrome.
? S/E of Dantrolene ? Muscle weakness and hepatitis
? Quinine is used to treat nocturnal leg cramps.

NEURO MUSCULAR BLOCKING AGENT
? Maximum histamine release, contraindicated in Asthma: d-TC
? Minimum histamine release, used in Asthma: Vecuronium
? Shortest acting non-depolarizing muscle relaxant = Mivacurium
? Shortest acting depolarizing muscle relaxant = Succinyl choline
? Overall shortest acting muscle relaxant = Succinyl choline
? Longest acting Neuromuscular blocker = Pancuronium
? Most commonly used muscle relaxant = Vecuronium
? Most potent skeletal muscle relaxant = Doxacurium
? Least potent skeletal muscle relaxant = Succinyl choline
? Least potent Non-depolarising skeletal relaxant = Rocuronium
? Metabolized by pseudo cholinesterase: Succinyl choline & Mivacurium
? Muscle relaxant of choice in obstetrics & to decrease BP: d-Tubo curare (does not cross placenta)
? Muscle relaxant of choice to increase BP: Pancuronium

---

? Muscle relaxant with ganglion block: Curare, Galamine, Trimethaphan & Pancuronium
? Fastest acting non-depolarising neuromuscular blockers - Rocuronium
? Vagal & Ganglion stimulation caused by Succing choline
? Maximal vagal block & Tachycardia- Pancuronium
? Histamine release & maximal vagal blockagle- d ? Tubocuramine

Depolarizing block
Non depolarising block
Effect on single twitch height
Depression
Depression
Train of four fade
Absent
Present
Tetanic fade
Absent
Present
Post tetanic facilitation
Absent
Present
Effect of anti cholinesterase
Potentiation of block
Reversal of block
Effect of non depolarizing agent
Less blockade
More blockade
SUCCINYL CHOLINE
? The only depolarizing (noncompetitive) muscle relaxant in use.
? Rapid onset of action ( 30-60 seconds)
? Over all shortest duration of action (3-5 min) due to rapid hydrolysis by pseudo choline esterase.
? Succinylcholine is two acetylcholine molecules linked end-to-end.
? Scoline is metabolized completely into succinic acid + choline
? Dibucaine inhibits pseudo choline esterase activity.
? The percentage of inhibition of pseudo choline esterase activity is termed the dibucaine number.
? % of abnormal /normal pseudo choline esterase is determined by Dibucaine number & fluoride number.
? Under standardized test conditions, dibucaine inhibits the normal enzyme by 80% and the abnormal enzyme
by only 20%.
? Dibucaine-resistant (variant) gene, is m/c recognized abnormal pseudocholinesterase genes.
? Normal Dibucaine no = 75 ? 85.

Drugs Known to Decrease Pseudocholinesterase Activity
Description
Drug
Organophosphate use for glaucoma
Echothiophate
Cholinesterase inhibitors
Neostigmine,Pyridostigmine
Monoamine oxidase inhibitor
Phenelzine
Antineoplastic agent
Cyclophosphamide
Antiemetic/prokinetic agent
Metoclopramide
-Blocker
Esmolol
Nondepolarizing muscle relaxant
Pancuronium
Various agents
Oral contraceptives

? Scoline transiently increases muscle tone in the masseter muscles
? Causes dual or biphasic block with doses more than 500 mg [or > 6mg/kg]

Phase I Block
Features of classical depolarization block
Phase II Block
Results from desensitization of receptor to Ach. & resembles competitive / non
depolarization block and partially antagonized by anticholinesterases

---

Side effects:
? Increases muscle tone, Intraocular pressure, Intra-abdominal pressure
? Muscle fasciculation/Muscle soreness or ache
? Hyperkalemia
diastolic cardiac arrest.
? Sudden Cardiac Arrest After Intubation And Succinylcholine Hyperkalemia
? Increases temperature i.e. Malignant Hyperpyrexia

Conditions causing susceptibility to Succinylcholine-induced Hyperkalemia
?
Burns
?
Parkinson's disease , Polyneuropathy
?
Massive trauma
?
Tetanus
?
Severe intraabdominal infection
?
Prolonged total body immobilization
?
Spinal cord injury
?
Ruptured cerebral aneurysm
?
Encephalitis
?
Closed head injury
?
Stroke
?
Hemorrhagic shock with metabolic acidosis
?
Guillain-Barre syndrome
?
Myopathies (eg, Duchenne's dystrophy)

NONDEPOLARIZING MUSCLE RELAXANTS
Relaxant
Chemical
Metabolism
Primary
Histamine
Vagal Blockade
Structure
Excretion
Release
Atracurium
Benzyl-
+++
Insignificant
+
0
Cisatracurium
isoquinolone
+++
Insignificant
0
0
Mivacurium
+++
Insignificant
+
0
Doxacurium
Insignificant
Renal
0
0
Pancuronium
Steroidal
+
Renal
0
++
Pipecuronium
+
Renal
0
0
Vecuronium
+
Biliary
0
0
Rocuronium
Insignificant
Biliary
0
+

ATRACURIUM
A.
Hofmann Elimination: [depends on pH & temperature]
? Inactivated in plasma by spontaneous non enzymatic degradation & by choline esterases.
? Major metabolite - laudanosine (CNS stimulant) produce epileptiform fits.
? It's duration of action is not altered in patients with hepatic and renal in sufficiency
? Muscle relaxant of choice in renal failure, anephric patients & liver disease
B.
Histamine release leading to flushing of skin.

---

CISATRACURIUM
? Undergoes Hoffman elimination & also metabolized by kidneys.
? 4-5 times more potent than atracurium
? Laudanosine production is 5 times lesser than atracurium

PANCURONIUM
? Causes vagal blockade and releases noradrenaline.
? Produces tachycardia and hypertension.
? It is muscle relaxant of choice in shock and hypotension.
? It is metabolized by the kidney, so avoided in renal failure.

VECURONIUM
? Most commonly used muscle relaxant for routine surgery.
? Most cardio stable. It is the muscle relaxant of choice for cardiac patients.
? Contraindicated in liver disease and in biliary obstruction.
? Causes polyneuropathy on long term use.

PIPECURONIUM
? Long acting
? No vagolytic activity (or) ganglion blockade activity.

ROCURONIUM
? Earliest onset of action among non-depolarising muscle relaxant.
? Muscle relaxant of choice for pre-curarization
? Non- depolarizing muscle relaxant of choice for intubation.

ASYMMETRIC MIXED-ONIUM CHLOROFUMARATES (GANTACURIUM)
? Ultra short acting muscle relaxant.
? Degraded by two chemical mechanisms, neither of which is enzymatic:
o
Rapid formation of an apparently inactive cysteine adduction product, with cysteine replacing chlorine.
o
Slower hydrolysis of the ester bond adjacent to the chlorine substitution, presumably to inactive
hydrolysis products.

SUGAMMADEX
? Sugammadex is the first selective relaxant binding agent
? Sugammadex exerts its effect by forming very tight complexes in a 1: 1 ratio with steroidal neuromuscular
blocking agents (rocuronium > vecuronium >> pancuronium).

Tubocurarine, the first muscle relaxant used clinically, produces hypotension and tachycardia through
histamine release.
Patients allergic to iodine (eg, shellfish allergies) could exhibit hypersensitivity to metocurine preparations as
they too contain iodide.
Gallamine has potent vagolytic properties and is entirely dependent on renal function for elimination.
Rapacuronium is not used anymore because of severe bronchospasm.

DISEASES WITH ALTERED RESPONSES TO MUSCLE RELAXANTS
Disease
Response to Depolarizers
Response to Non depolarizers
Amyotrophic lateral sclerosis
Contracture
Hypersensitivity
Autoimmune disorders (SLE, polymyositis,
Hypersensitivity
Hypersensitivity
dermatomyositis)
Cerebral palsy
Slight hypersensitivity
Resistance
Hemiplegia
Hyperkalemia
Resistance on affected side
Muscular dystrophy (Duchenne type)
Hyperkalemia and malignant
Hypersensitivity
hyperthermia

---

Myasthenia gravis
Resistance and proneness to
Hypersensitivity
phase II block
Myasthenic syndrome
Hypersensitivity
Hypersensitivity
Myotonia (dystrophica, congenita,
Generalized muscular
Normal or hypersensitivity
paramyotonia)
contractions
Severe chronic infection (tetanus, botulism)
Hyperkalemia
Resistance

Sequence of muscle blockade after muscle relaxants therapy
? First muscle to be blocked: Central muscles (muscles of face) followed by jaw
pharynx larynx
respiratory muscles
peripheral muscles
? In general, larger muscles (eg, abdominal, trunk, paraspinous, diaphragm) are more resistant to
neuromuscular blockade and recover more rapidly than smaller muscles (eg, facial, foot, hand).
? The diaphragm is usually the last muscle to be paralyzed
? Recovery occurs in the reverse order.
? Muscle monitored for activity during blockade: Adductor pollicis

Reversal of Muscle Relaxation
? Depolarizing (Non- competitive) agents are not antagonized
? Non-Depolarizing (Competitive) MR are antagonized by Acetyl choline or Anti Choline EsteraseNeostigmine,
Pyridostigmine and Edrophonium.
? Atropine is given to prevent muscarinic effects.
? Recent drug: Sugammadex [sugar, gamma cyclo dextrin]
o
Causes quick & complete recovery, reverses profound neuromuscular blockade
o
Has hydrophobic cavity with hydrophilic exterior [soluble in water
traps drug in the center]
MALIGNANT HYPERTHERMIA
? Drug- or stress-induced hypermetabolic syndrome.
? Vigorous muscle contractions, an abrupt increase in temperature, subsequent cardiovascular collapse
? Uncontrolled release of Ca2+ from the sarcoplasmic reticulum due to defect in the ryanodine receptor
(RYR1) is the initiating event
? Inherited as autosomal dominant fashion, with variable penetrance & expressivity.
? Triggers: Stress, excitement, anoxia, viral infections, lymphoma, ischemia or hypoxia.

Drugs known to trigger malignant hyperthermia
Drugs safe in malignant hyperthermia
? Halothane
? Nitrous oxide
? Methoxyflurane
? Barbiturates
? Enflurane, isoflurane
? Diazepam
? Succinylcholine
? Tubocurarine
? Decamethonium
? Pancuronium, vecuronium
? Gallamine
? Opiates
? Diethyl ether, Ethylene, Ethyl chloride
? Trichloroethylene
? Ketamine
? Phencyclidine
? Cyclopropane

? Early signs: masseter muscle contracture, muscle rigidity, metabolic acidosis, sinus tachycardia,
supraventricular tachyarrhythmias, mottling or cyanosis of the skin, increased cot production, and
hypertension.
? Two signs helpful in making a prehyperthermic diagnosis
o
Increased end-tidal CO2
o
Masseter spasm
? M/C with combination of depolarizing blocking agent and anesthetic.

---

Management of Malignant Hyperthermia
? Discontinue volatile anesthetic and succinylcholine.
? Hyperventilate with 100% O2 at high flows.
? Administer sodium bicarbonate, 1-2 mEq/kg intravenously.
? Mix dantrolene sodium with sterile distilled water and administer 2.5 mg/kg iv
? Institute cooling measures (lavage, cooling blanket, cold intravenous solutions).
? Administer additional doses of dantrolene if needed.
? Treat severe hyperkalemia with dextrose, 25-50 g IV, and regular insulin, 10-20 U intravenously (adult dose).

NEUROLEPTIC MALIGNANT SYNDROME
? Rare complication of antipsychotic therapy, meperidine and metoclopramide
? Mechanism: dopamine blockade in the basal ganglia and hypothalamus and impairment of
thermoregulation.
? Muscle rigidity, hyperthermia, rhabdomyolysis, autonomic instability, altered consciousness
? Laboratory findings: increased WBC count and increased levels of creatinine phosphokinase, liver enzymes,
plasma myoglobin and myoglobinuria
? Deaths occur primarily as a result of renal failure or arrhythmias

Diagnostic criteria:
A. Developmental of severe muscle rigidity & elevated temperature associated with use of neuroleptic
medication.
B. Two or more of the following
1. Diaphoresis (sweating)
2. Dysphagia
3. Tremors
4. Tachycardia
5. Incontinence
6. Mutism
7. Change of level of consciousness from confusion to coma
8. Elevated or labile B.P
9. Leucocytosis
10. Laboratory evidence of muscle injury (e.g. elevated CPK), renal function test
C. Symptoms are not due to phencyclidine, viral encephalitis or mood disorder with catatonic features.
Treatment: Dantrolene (drug of choice) or Bromocriptine/Amantadine

LOCAL ANESTHETICS
? Interfere with the excitation process in a nerve membrane in one or more of the following ways:
? Altering the basic resting potential of the nerve membrane
? Altering the threshold potential (firing level)
? Decreasing the rate of depolarization
? Prolonging the rate of repolarization

Classification of Local Anesthetics according to Biological site and Mode of action
Type
Definition
Chemical substance
A
Acting at receptor site on external surface of nerve membrane
Biotoxins (tetrodoxins,
saxitoxins)
B
Acting at receptor site on internal surface of nerve membrane
Quaternary ammonium analogs
.
of lidocaine, Scorpion venom
C
Acting by a receptor independent physico-chemical
Benzocaine
mechanism
D
Acting by combination of receptor and receptor- independent
Most LA's (articaine, lidocaine,
mechanisms
mepivacaine, prilocaine)

---

? LA's are weak bases carrying a positive charge at the tertiary amine group at physiological pH.
? Mechanism of action: Blocks voltage gated Na+ channels from inside of cell membrane by binding to a-
subunit.
? Nerve block produced by local anesthetics is called a nondepolarizing nerve block.

Classification of Local Anesthetics based on chemical structure
ESTERS
AMIDES
Quinoline
Esters of benzoic acid
Esters of para-aminobenzoic acid
Articaine
Centbucridine
Butacaine
Chloroprocaine
Bupivacaine
Cocaine
Procaine
Dibucaine
Ethyl aminobenzoate
Propoxycaine
Etidocaine
(benzocaine)
Lidocaine
Hexylcaine
Mepivacaine
Piperocaine
Prilocaine
Tetracaine
Ropivacaine



Local anesthetic
Ester linked
Amide linked
Metabolism
By pseudocholinesterase
N-dealkylation and hydroxylation by
microsomal P-450 enzymes in the
liver.
Shorter duration (< 30
Procaine (low potency)
min)
Chlorprocaine (intermediate
potency)
Intermediate duration
-
Lidocaine, Mepivacaine, Prilocaine
& potency (30-90 min)
Long duration &
Tetracaine, Benzocaine
Bupivacaine, Ropivacaine, Dibucaine,
potency ( > 120 min)
Etidocaine

Alkalinization of local anesthetics by adding sodium bicarbonate
? Speeds onset
? Improves the quality of the block
? Prolongs blockade by increasing the amount of free base available.
? Most useful for agents such as lidocaine, mepivacaine, and chloroprocaine.
? Sodium bicarbonate is usually not added to bupivacaine, which precipitates above a pH of 6.8.
Sensitivity of nerve fibres for local anesthetics
? Small myelinated axons (Ay motor & A sensory fibers) are most susceptible to local anesthetics.
? Next in order of block are the large myelinated (A and A) fibers
? Least susceptible are the small, nonmyelinated C fibers.
? Among sensory fibres temperature (cold > heat ) > pain > touch > deep pressure > proprioception
Effects of addition of a Vasoconstrictor to Local Anesthetic
(Eg: adrenaline, Concentration: 1:50,000 to 1:200,000)
? Prolongs duration of action by decreasing their rate of removal from the local site
? Reduces systemic toxicity of LAs: rate of absorption is reduced
? Makes the injection more painful
? Provides a more bloodless field for surgery.
? Increases the chances of subsequent local tissue edema and necrosis as well as delays wound healing by
reducing oxygen supply and enhancing oxygen consumption in the affected area

---

LIGNOCAINE
? Lignocaine should not be used in patients with history of malignant hyperthermia
? Lignocaine is used for ventricular fibrillation specially after MI
? Lignocaine can produce cauda equina syndrome
? Preservative free lignocaine called as xylocard is preferred for IV injection.
? Lidocaine transdermal patch: (LIDODERM) - relief of pain associated with postherpetic neuralgia.

Lignocaine dose:
? With adrenaline: 7 mg/kg
? Without adrenaline: 4 mg/kg
Concentration of Lignocaine
? IV Regional anaesthesia 0.5%
? Nerve block
1%
? Epidural / Jelly
2%
? Topical
4%
? Spinal
5%
Lignocaine with adrenaline SHOULD NOT be used for:
? Areas with end arteries e.g. for ring block of fingers, toes, penis, pinna (absolute contraindication)
? When an inhalational agent especially halothane which sensitizes myocardium to adrenaline is used
? Myocardial ischemic patients
? Hyperthyroid patient
? Severe hypertensives
? Intravenous regional anaesthesia (Bier's block)

Anticonvulsive Blood Levels of Lidocaine:

Clinical Situation
Lidocaine Blood Level g/mL
Anticonvulsive level
0.5-4
Preseizure signs and
4.5-7
sy
T m
on p
i t
c om
--cls
onic seizure
>7.5
DOSE OF ADRENALINE:

Condition
Route of administration
Adrenaline dose
Branchial asthma
Inhalational
1 in 100
Anaphylactic shock
I.M, S.0
1 in 1000
I.V
1 in 10,000
Cardiac arrest
Intra-cardiac
1 in 10,000
With Local anaesthesia
Subcutaneous
1 in 2,00,000
Epinephrine 1:1000 contains 1 mg of epinephrine per ml. 1:1000 solution adrenaline
= ig adrenaline in 1000m1 solution

= 1000mg adrenaline per 1000mIsolution

= 1mg per ml

OTHER LOCAL ANESTHETIC AGENTS Cocaine:
? First discovered LA
? Only naturally occurring LA
? Vasoconstrictor action
? Not to be used with adrenaline d/t cardiac arrhythmias & ventricular fibrillation.

---

Prilocaine:
? Safest
? Maximum Methemoglobinemia
? O-Toludine metabolites accumulate after large doses & convert hemoglobin to methemoglobin
? Treatment of Methemoglobinemia: IV methylene blue (1-2mg/ kg of 1% solution) which reduces
methemoglobin (Fe3+) to hemoglobin (Fe2+)
? Most suitable for Bier's IV block
Bupivacaine:
? Most potent
? Best for isobaric anesthesia and regional block
? Contraindicated in regional IV anesthesia
? Long duration of action plus its differential blockade (sensory> motor) has made it a popular drug for
providing prolonged analgesia during labor or the postoperative period.
? Bupivacaine is a racemic mixture of (R) & (S) isomers while Levobupivacaine (Chirocaine) contains single (S)
stereoisomer, both containing butyl groups.
? The most common ECG finding with bupivacaine intoxication is slow idioventricular rhythm with broad QRS
complexes and eventually, electromechanical dissociation.
? Bupivacaine is the most cardiotoxic local anesthetic - should not be used for Bier's block.
? Recent recommendation for treatment of bupivacaine induced cardiotoxicity: 20% intralipid [4m1/kg
followed by 0.5m1/kg/min infusion]
? Bupivacaine is LA of choice for isobaric spinal anesthesia.
? It is most commonly used for a carpal tunnel release.
? Newer drug: Depobupivacaine- multivesicular liposomal formulation of bupivacaine with long lasting effect
(72 hours).

Procaine:
? LA of choice in malignant hyperthermia
? 15t synthetic LA
Chlorprocaine:
? When injected into the subarachnoid space or intradurally it may cause paraplegia, d/t preservative,
sodium bisulfate (now replaced with an antioxidant, a derivative of EDTA).
? Severe back pain following epidural administration.
Mepivacaine: not metabolized by neonates so C/I neonates & labour
Shortest acting LA ? Chlorprocaine
Longest acting LA ? Dibucaine > Tetracaine > Bupivacaine
All LAs are vasodilators except lignocaine (no vasogenic action) & Cocaine (vasoconstrictor)
LA used in surface anesthesia
Never used as surface anesthetic
Hexycline, Lignocaine,Dibucaine, Tetracaine
Procaine, Mepivacaine
Prilocaine, Cocaine
Bupivacaine

? Articaine (Septocaine) is a recently introduced amino amide, approved in the U.S. for dental and
periodontal procedures. It exhibits a rapid onset (1-6 minutes) and duration of action of ?1 hour.
? Benzocaine a common ingredient in local anesthetic sprays also can cause Methemoglobinemia.
? Ropivacaine: contains propyl group, made of single (S) stereoisomer
? Compared to bupivacaine, Ropivacaine is less cardiotoxic, less potent with shorter duration of action
? LA's are myotoxic (bupivacaine > lidocaine > procaine, Least with Ropivacaine), if injected directly into a
muscle

---

EMLA cream (Eutectic [easily melted] Mixture of Local Anesthetics)
? 5% emulsion containing 2.5% lidocaine and 2.5% prilocaine
? Used as an anesthetic prior to venipuncture, skin graft harvesting, laser removal of portwine stains,
lithotripsy and circumcision.
? EMLA cream should not be used on mucous membranes, broken skin, infants less than 1 month old, or
patients with a predisposition to methemoglobinemia

ADJUNCTS TO ANESTHESIA
General principles
? Stop ACEI/ ARB 24 hours before surgery.
? Stop metformin 24 hours before surgery.
? Stop sulfonylureas the night before surgery.
? Stop diuretics once the patient is NPO.
? Continue statins.
? Continue CNS-active drugs.
? Insulin may require adjustment.
? Stop OCPs and HRT four weeks before surgery, if possible.
? Stop nonselective NSAIDs two to three days before surgery, but continue COX-2 inhibitors.
? Continue outpatient dosing of corticosteroids and add a stress dose.
? Stop DMARDs and biologics one week before surgery.
? Stop herbal medicines one to two weeks before surgery.

PRE ANAESTHETIC MEDICATION
? Opioids - Morphine
? Anxiolytics ? Diazepam
? Hypnotic ? Barbiturate
? Anti cholinergics- Atropine, Hyoscine
? Neuroleptic ? chlorpromazine

ADJUNCTS FOR ANESTHESIA
? H2 blocker - Metoclopramide, Ondansetron: reduce the risk of aspiration pneumonia.
? Diphenhydramine: antimuscarinic or atropine-like activity or antiserotonergic activity (antiemetic)
? Metoclopramide increases lower esophageal sphincter tone, speeds gastric emptying, and lowers gastric
fluid volume.
? Serotonin 5-HT3 receptor blockers like Ondansetron, granisetron, dolasetron - anti emetic effects.
? Clonidine: an adjunct for epidural infusions in pain management. Most useful in neuropathic pain.
? Dexmedetomidine is a parenteral selective a2-agonist with sedative properties.
? Selective activation of carotid chemoreceptors by low doses of doxapram stimulates hypoxic drive,
producing an increase in tidal volume and a slight increase in respiratory rate.
? Patients are at risk if their gastric volume is greater than 25 mL (0.4 mL/kg) and their gastric pH is less than
2.5.

Post Anesthetic Muscular Complications
? Catatonia: Droperidol
? Muscle spasm & Rigidity: Fentanyl (opioids)
? Fasciculation, Soreness and Ache: Suxamethonium
? Increased muscle tone: Ketamine & Suxamethonium

IMPORTANT FACTS
? Post operative shivering: treated by pethidine/pentazocine.
? Intravenous meperidine (25 mg) - most effective opioid for decreasing shivering.
? Inhalational anesthetic that boils at room temperature: Desflurane
? Primary site of action of ketamine: Thalamoneocortical projection
? Abnormal spike discharges in epileptic patients: Methohexitone
? Steroid anesthetic: Althesin, Minaxolone

---

? Heid brink meter indicates: flow rate of gases
? Armoured ET tube: used in neurosurgery
? Aspiration of gastric contents: Mendelson's syndrome
? First reflex to appear during recovery from anesthesia: swallowing
? 5 % CO2 is used for creating pneumoperitoneum during laparoscopy
? A mixture of 80% helium and 20% O2 is used for tracheal obstruction.
? M/C complication in pediatric anesthesia: laryngospasm.
? M/C complication in adult patients under GA: Dysarhythmias & Hypotension
? Neurolept analgesia: Fentanyl + Droperidol
? Neurolept anesthesia: Fentanyl + Droperidol + 65% N2O + 35% O2

---

III.
REGIONAL ANESTHESIA & PAIN MANAGEMENT

Baricity of Anesthetic Agents
? Higher the dosage or site of injection, the higher the level of anesthesia obtained.
? Migration of the drug in CSF depc.t.ius on its specific gravity relative to CSF (baricity).
? A hyperbaric solution is denser (heavier) than CSF, whereas a hypobaric solution is less dense (lighter) than
CSF.
? Solutions can be made hyperbaric by adding glucose or hypobaric by adding sterile water.
? In head-down position, a hyperbaric solution spreads cephalad and a hypobaric anesthetic solution moves
caudad; and vice-versa in head-up position
? Anesthetic agents are mixed with CSF (at least 1:1) to make their solutions isobaric.
? Hyperbaric bupivacaine and tetracaine are most commonly used agents for spinal anesthesia.
? Both are relatively slow in onset (5-10 min) and have a prolonged duration (90-120 min).
? Hyperbaric spinal anesthesia is more commonly used than the hypobaric or isobaric techniques.
? The level of anesthesia is dependent on the patient's position during and immediately following the
injection.
? In the sitting position, "saddle block" can be achieved by keeping the patient sitting for 3-5 min following
injection so that only the lower lumbar nerves and sacral nerves are blocked.
INTRAVENOUS REGIONAL ANESTHESIA (BIER'S BLOCK)
? It consists of injection of LA in a vein of a tourniquet occluded limb.
? 0.5% Lidocaine is most commonly used in drug
? Mainly used for upper limb orthopedic procedures as it is most difficult to obstruct blood supply of lower
limb.

SPINAL ANESTHESIA
? The principal site of action for neuraxial blockade is the nerve root.
? Neuraxial anesthesia does not block the vagus nerve.
? The drug is injected in subarachnoid space (piamater and arachnoid membrane)
? Injection below L1 in adults and L3 in children avoids trauma to the spinal cord.
? Quincke needle is a cutting needle with end injection.
? Blunt tip (pencil-point) needles decrease the incidence of postdural puncture headache.
? Heavily myelinated, small preganglionic sympathetic fibers and pain fibers are blocked first.
? Motor fibers are blocked last.
? The level of motor block is two to four dermatomes lower than the level of sensory anesthe
? Sequence of blockade autonomic
sensory
motor
Confirmation of spinal needle: feel of two "pops".
? The first is penetration of the ligamentum flavum
? The second is penetration of the dura-arachnoid membrane.

Factors Affecting the Level of Spinal Anesthesia
Most important factors
Other factors
? Baricity of anesthetic solution
? Age, Patient height, Pregnancy
? Position of the patient during &
? Cerebrospinal fluid
? Immediately after injection
? Curvature of the spine
? Drug dosage
? Drug volume
? Site of injection
? Intra -abdominal pressure
? Needle direction

? MOA- Local anesthetic acts on spinal nerves and dorsal ganglia
? Unconsciousness, apnea, and hypotension resulting from high levels of spinal anesthesia are referred to as a
"high spinal" or "total spinal."

---

? Complications of SAB:
o
Hypotension ?M/c complication of SAB. Preventive measures are head low position to increase venous
return, fluid preloading with RL, prophylactic vasopressor, oxygen supplementation
o
Bradycardia ?M/c arrhythmia
o
Apnea
o
Cardiac arrest
o
Anaphylaxis
o
Nausea & Vomiting
o
6th cranial nerve is M/c nerve involved due to longest intracranial course.
o
Transient neurological symptoms (TNS), also called as transient radicular irritation
o
Post Dural puncture Headache (PDPH)

Post Dural Puncture Headache (PDPH)
? Presents 12-24hrs after spinal block
? Usually occipital but can also be frontal
? Increases on sitting & relieved on lying down
? Lasts for 7-10 days but may be for 3 weeks
? Cause ? Due to CSF leakage through dural rent
? Treatment:
o
Small size needle
o
Adequate hydration
o
Prone or supine position
o
Analgesic
o
Oral or I/V caffeine
o
Autologous epidural blood patch (most effective): stop further leakage of CSF by either mass effect or
coagulation

Factors that may increase the incidence of Post?spinal Puncture Headache
Age
Younger more frequent
Gender
Females > males
Needle size
Larger > smaller
Needle bevel
Less when the needle bevel is placed in the long axis of the neuraxis
Pregnancy
More when pregnant
Dural punctures (no.)
More with multiple punctures

Factors not increasing the incidence of Post?spinal Puncture Headache
Continuous spinals
Timing of ambulation

Contraindications to spinal anaesthesia

Absolute
Relative
? Raised intracranial pressure
? Aortic and mitral stenosis
? Patient refusal
? MI
? Shock: Hypotension and hypovolemia
? Heart block
? Infants and children- control of level is difficult.
? Spinal deformities
? Bleeding disorders
? Psychiatric and CNS disorders
? Patient's on anticoagulants
? Infection of the local site and
? Septicemias
? Vertebral abnormalities (kyphosis, lordosis, etc.)

---

Agents used in Spinal Anesthesia
? Bupivacaine: 0.5% in 8.25% dextrose, 0.5% plain
? Lidocaine: 2% plain, 5% in 7.5% dextrose
? Procaine: 10% plain, 2.5% in water
? Tetracaine: 0.5% in water, 0.5% in D5W

Parameter
Spinal Anesthesia
Epidural Anesthesia
Level performed
Lumbar
Any Level
Cost
Cheaper
Expensive
Onset of Effect
2- 3 minutes
15 ? 20 minutes
Duration of Effect
Lesser
Prolonged
Quality of block
Total
Patchy
Post spinal head ache
Present
Absent
Epidural hematoma
Less common
More common
Total spinal
Rare
High chances
Intravascular injection
Rare
High chances
Drug toxicity
Less common
More common
Catheter complication
Absent
Present

EPIDURAL BLOCK
? Drug is injected in the epidural space between the ligamentum flavum and the duramater.
? The standard (Tuohy needle, directional needle) epidural needle has a blunt bevel with a gentle curve of 15-
30? at the tip.
? Straight needles without a curved tip (Crawford needles): higher incidence of dural puncture but facilitate
passage of an epidural catheter.
? Methods to locate epidural space (negative pressure test)
-
Hanging drop technique
-
Loss of resistance (preferred)
-
Macintosh extradural space indicator
? Indications for Epidural Anesthesia:
o
Mainly used for controlling post ? operative pain & Chronic cancer pain
o
Painless labor
o
Can be used for all surgeries done by spinal anesthesia
? Advantages of epidural anaesthesia
o
Less hypotension
o
No postspinal headache
o
Level of block can be extended
o
Any duration of surgery can be performed

CAUDAL BLOCK (EPIDURAL SACRAL BLOCK)
? Sacral epidural anesthesia is referred to as a caudal block.
? Drug penetrates the sacrococcygeal ligament covering the sacral hiatus that is created by the unfused S4
and S5 laminae.
? Also employed for labor and postoperative analgesia.
? Mainly used in children for perineal and genitourinary surgery.
? Within the sacral canal, the anesthesia bathes the S2?S4 spinal nerve roots, including the pain fibers from
the uterine cervix and superior vagina, and the afferent fibers from the pudendal nerve.
? The entire birth canal, pelvic floor, and majority of the perineum are anesthetized
? Lower limbs are not usually affected.
? The pain fibers from the uterine body (superior to the pelvic pain line) ascend to the inferior thoracic-
superior lumbar levels; these and the fibers superior to them are not affected by the anesthetic, so the
mother is aware of her uterine contractions.
? With epidural anesthesia, no " spinal headache" occurs because the vertebral epidural space is not
continuous with the cranial extradural (epidural) space

---

PUDENDAL NERVE BLOCK
? Peripheral nerve block that provides local anesthesia over the S2-S4 dermatomes.
? Blocks the majority of the perineum and the inferior quarter of the vagina.
? Does not block pain from the superior birth canal (uterine cervix and superior vagina), so the mother is able
to feel uterine contractions.

INFILTRATION ANESTHESIA
? Lidocaine (0.5-1%), procaine (0.5-1%), and bupivacaine (0.125-0.25%).
? When used without epinephrine, up to 4.5 mg/kg of lidocaine, 7 mg/kg of procaine, or 2 mg/kg of
bupivacaine can be employed in adults.
? When epinephrine is added, these amounts can be increased by one-third.

CERVICOTHORACIC (STELLATE) BLOCK
? Used in patients with head, neck, arm and upper chest pain.
? The paratracheal technique is most commonly used.
? Confirmation of block: increase in the skin temperature of the ipsilateral arm and the onset of Horner's
syndrome.
? Complications: hematoma, pneumothorax, epidural anesthesia, brachial plexus block, hoarseness due to
blockade of the RLN and rarely, osteitis or mediastinitis following esophageal puncture.
Advantages of post operative analgesics:
? Patient comfort
? Increase mobility
? Fewer pulmonary and cardiac complications
? Reduced risk of DVT
? Less likelihood of developing neuropathic pain
? reduced cost of care
PATTERNS OF REFERRED PAIN

Location
Cutaneous Dermatome
Central diaphragm
C4
Lungs
T2--T6
Heart
T1--T4
Aorta
T1--L2
Esophagus
T3-18
Pancreas and spleen
T5--T10
Stomach, liver and gallbladder
T6--T9
Adrenals
T8--L1
Small intestine
T9--T11
Colon
T10--L1
Kidney, ovaries, and testes
T10--L1
Ureters
T10--T12
Uterus
T11--L2
Bladder and prostate
S2--S4
Urethra and rectum
S2--S4
Jannetta procedure: Microsurgical decompression of the trigeminal nerve for trigeminal neuralgia (tic douloureux).

---

IV.
PHYSIOLOGY, PATHOPHYSIOLOGY OF ANESTHETIC MANAGEMENT

Average Blood Volumes
Age
Blood Volume
Neonates
Premature
95 mL/kg
Full-term
85 mL/kg
Infants
80 mL/kg
Adults
Men
75 mL/kg
Women
65 mL/kg

Characteristics of Neonates and Infants that differentiate them from Adult Patients

Physiological
Anatomical
? Heart-rate-dependent cardiac output
? Noncompliant left ventricle
? Faster heart rate
? Residual fetal circulation
? Lower blood pressure
? Difficult venous and arterial cannulation
? Faster respiratory rate
? Large head and tongue
? Lower lung compliance
? Narrow nasal passages
? Greater chest wall compliance
? Anterior and cephalad larynx
? Lower functional residual capacity
? Long epiglottis
? Higher ratio of body surface area to body
? Short trachea and neck
weight
? Prominent adenoids and tonsils
? Higher total body water content
? Weak intercostal and diaphragmatic muscles
? High resistance to airflow
Pharmacological
? Immature hepatic biotransformation
? Decreased protein binding
? Rapid rise in FA/FI (Fractional alveolar concentration/fractional inspired concentration)
? Rapid induction and recovery
? Increased minimum alveolar concentration
? Larger volume of distribution for water-soluble drugs
? Immature neuromuscular junction
Anatomical dead space is increased
Anatomical dead space is decreased
Alveolar dead space is increased
by
by
by
? Old age
? Intubation
? IPPV
? Neck extension
? Tracheostomy
? PEEP
? Jaw protrusion
? Hyperventilation
? General anesthesia
? Bronchodilators (Atropine)
? Neck flexion
? Hypotension
? Halothane
? Bronchoconstrictors
? Lung pathologies affecting
? Increased lung volume
? Massive pleural effusion
diffusion like interstitial
? Anesthesia mask & Circuits
lung disease, Pulmonary
? IPPV
embolism, pulmonary
? PEEP
edema, ARDS
Physiological dead space is decreased by
? Supine posture
? Neck flexion
? Bronchoconstrictor

---

? Artificial airway (Eg: intubation, tracheostomy).
Induction of anesthesia consistently produces 15-20% reduction in FRC (400m1 in most patients).
M/C cause of airway obstruction in unconscious patients - tongue falling back against posterior pharynx.
FLUID MANAGEMENT & TRANSFUSION
CRYSTALLOIDS
COLLOIDS
? RL (slightly hypotonic)
? Albumin, Gelatin, Dextran, Hydroxyethyl
? NS & 5% Dextrose (isotonic)
starch, blood ? Hypertonic
? DNS & Hypertonic saline (Hypertonic)
? Intravascular half life ? 30 mins. Expands plasma
? Expands plasma volume for 2 - 4 hours
volume for less time
? For replacing blood loss 3 times the lost fluid
should be given
? Given in 1:1 ratio
? NS ? preferred over RL for hypochloremic metabolic alkalosis, brain injury (as calcium ions increase
neuronal injury), hyponatremia, to maintain BP in hypovolemia
? DNS ? best used maintenance fluid intraoperatively
? Hypertonic saline ? hyponatremia, cerebral and pulmonary edema
? Dextran ? LMW dextran improves microcirculation; can interfere with blood grouping and cross matching
? Blood - the ideal fluid to be used in hemorrhagic shock.
Composition of Crystalloid Solutions

Solution
Tonicity
Na+
CI-
K+
Ca 2+
Glucose
(mOsm/L)
(mEq/L)
(mEq/L)
(mEq/L)
(mEq/L)
(g/L)
5% dextrose in water
Hypo (253)
50
(D5W)
Normal saline (NS)
Iso (308)
154
154
D51/4 NS
Iso (355)
38.5
38.5
50
D51/2 NS
Hyper
77
77
50
(432)
D5NS
Hyper
154
154
50
(586)
Lactated Ringer's (RL)
Iso (273)
130
109
4
3
D5LR
Hyper
130
109
4
3
50
(525)
1/2NS
Hypo (154)
77
77
INTRAOPERATIVE FLUID THERAPY
? Fluid loss due to starvation: 2mL/kg/hr
? Maintenance fluid: 2mL/kg/hr
? Third space losses ? fluid accumulation in the tissues in the form of edema
4mL/kg/hr ? for surgeries with minimum dissection. e.g: Herniorrhaphy
6mL/kg/hr ? moderate dissection. e.g: Gastrojejunostomy and vagotomy
8mL/kg/hr ? heavy dissection.e.g: Whipple's procedure
? Blood loss to be replaced by compatible blood transfusion, when the hematocrit falls below 25%
OBSTETRIC ANESTHESIA
? Ephedrine: vasopressor of choice for hypotension during pregnancy
? a-adrenergic agonists (phenylephrine and metaraminol) - less fetal acidosis than ephedrine.

---

? The greatest strain on the parturient's heart occurs immediately after delivery (increase in cardiac output as
much as 80% above prelabor values)
? Caesarean section in CVS disease complicating pregnancy - mainly done for obstetric indications
? In coarctation of aorta, elective CS - to prevent rupture of the aorta or mycotic cerebral aneurysm.
? Needle for epidural block: Tuohy's needle.
? Average blood loss during vaginal delivery is 400-500 mL (800-1000 mL in cesarean section)
? Blood volume does not return to normal until 1-2 weeks after delivery.
Induction in Pediatric patients
Inhalation
Intravenous
Intramuscular
Single Breath induction
Rapid acting barbiturate or
IM Ketamine ?combat
Sevoflurane in N2O for rapid induction
Propofol followed by non
children
Classical method N2O & O2 &
depolarizing muscle relaxant (eg;
Sevoflurane / halothane is added
rocuronium, atracurium,
mivacurium) or Succinyl choline
CONTROLLED HYPOTENSION
? Elective lowering of arterial blood pressure.
? Maintaining the mean arterial pressure at the level of 50-65 mmHg.
? Reduction in baseline MAP by 30%.
? Advantages: minimization of surgical blood loss and better surgical visualization
? Methods:
o
Positioning: elevation of the surgical site
blood pressure at the wound is selectively reduced
o
Positive-pressure ventilation
o
Ganglion blockers: Trimethaphan is the drug of choice.
o
Due to their rapid onset and short duration of action, sodium nitroprusside and nitroglycerin have the
advantage of precise control.
o
Creation of a high sympathetic block with an epidural or spinal anesthetic.
o
Hypotensive anesthetics like propofol can be used clinically
? Indications: cerebral aneurysm repair, brain tumor resection, total hip arthroplasty, radical neck dissection,
radical cystectomy and other operations associated with significant blood loss.
? Contraindications: Severe anemia, hypovolemia, atherosclerotic cardiovascular disease, renal or hepatic
insufficiency, cerebrovascular disease, or uncontrolled glaucoma.

---

V.
SPECIAL PROBLEMS

CARDIOPULMONARY RESUSCITATION
THE 2010 AHA GUIDELINES FOR CPR
? Recommend a change in the BLS sequence of steps from A-B-C (Airway, Breathing, Chest compressions) to
C-A-B (Chest compressions, Airway, Breathing) for adults, children, and infants (excluding the newly born).
? Continuous quantitative waveform capnography is recommended for confirmation and monitoring of
endotracheal tube placement.
? Atropine is no longer recommended for routine use in the management of pulseless electrical activity
(PEA)/asystole.
? Increased emphasis on physiologic monitoring to optimize CPR quality.
? Adenosine is recommended as a safe and potentially effective therapy in the initial management of stable
undifferentiated regular monomorphic wide-complex tachycardia.
New Recommendations
? Hands Only CPR.
? CPR is the only treatment for sudden cardiac arrest.
? Don't stop pushing. Every interruption in chest compressions interrupts blood flow to the brain, which leads
to brain death if the blood flow stops too long.
? Defibrillation using biphasic electrical current works best.
? Bretylium is no longer recommended.
? Glucose & calcium solutions are to be avoided hypercalcemia & hyperglycemia results in neuronal
damage.
? Vasopressin has been added and amiodarone has gained new emphasis in these newest guidelines.
CHEST COMPRESSION
? At least 100 compressions per minute (30 compressions in 18 seconds)
? Chest compression to ventilation ratio is 30:2
? Sufficient force is applied to depress the sternum 4-5 cm (1 1/2 to 2 inches)
? In newborns, the depth of chest compressions should be one third of the AP diameter of the chest.
? Allow complete recoil of chest
? Switching rescuers every 2 mins


< 2 months
Infants & children
Adult
Compression
90/min
100/min
100/min
>100/min
Compression ventilation ratio
2 Rescuer: 3:1
Single rescuer: 30:2
Two rescuer: 15:2
30:2
High quality CPR:
? Minimize interruptions during compressions
? Avoid hyperventilations
? Higher the CPR - Better the surrival
? Not > 10 secs for pulse check
? EtCO2 <10 mm Hg - No ROSC
? EtCO2 <20 mm Hg ? Inefficient compression
? Tidal volume 500-600 ml
In CPR, breaths are delivered slowly with a smaller tidal volume of 700-1000m1, smaller (400-600m1) if
supplemental 0 2 is used.
A rescuer's exhaled air has an oxygen concentration of only 16-17% and contains significant CO2
Cricoid pressure (Sellick's maneuver) decreases the possibility of regurgitation and aspiration during
intubation.

---

Cardiac Massage :
? Adults: Compressions over lower third of sternum (2 fingers above xiphoid process)
? Children: Two thumbs technique for compressions
? Newborns: Two thumbs with encircled chest technique for compressions.
? Pregnant: External cardiac massage with lateral tilt..
Airway management
? Laryngoscope:
o
The most commonly used laryngoscope is Macintosh which has curved blades.
o
Position of head and neck during laryngoscopy is "Extension at atlanto occipital joint 7585 degrees and
flexion at cervical spine 15-25 degrees ? Magill position"
o
Complication ? MC injury during laryngoscopy is damage to upper incisors

? Endotracheal tubes:
o
Increases dead space in adult (by 70mL)
o
Decreases dead space in children.
o
In small children < 10 years uncuffed tube should be used but with the advent of newer cuffs, cuffed
tubes can be used even for children.
Size of endotracheal tubes:
Premature baby
2.5 mm
0 -6 Months
3 to 3.5 mm
6 Months ?1 Year
3.5 to 4 mm
Children < 6 Year
Age in years + 3.5 mm
3
> 6 years ? 15 year
Age in Years + 4.5 mm
4
Adult females
7.5 to 8 no.
Adult males
8.5 to 9 no.
? Reflex response to intubation ? tachycardia, hypertension, laryngospasm, ICT, Cortisol and
catecholamines
? Methods to inhibit reflex response ? xylocaine spray, xylocard injection, opioids, Ca Channel blockers
? RAE tube ? used for oral and dental surgeries like cleft lip and cleft palate
? Robert Shaw and Carlen tube
o
Used for thoracic surgeries or single lung ventilation.
o
To prevent spillage of pus and malignant cells during bronchopleural lavage
o
The major side effect is hypoxia due to malposition and ventilation perfusion mismatch.
o
Confirmation is done by bronchoscopy.
Indications for Nasal
Contraindications of nasal intubation
Contraindications for both oral and
intubation
nasal intubation
? Oral surgeries
? Basal skull fractures
? Laryngeal edema
? Fracture of Mandible
? CSF Rhinorrhea
? Epiglottitis
? Awake intubation
? Nasal mass
? Laryngeo ? tracheo bronchitis - In
? Prolonged intubation
? Adenoids
such pt's tracheostomy is preferred
? Any coagulopathies
Advantages of nasal over oral intubation
Blind nasal intubation is done in
? Better fixation
? Temporo ? mandibular joint ankylosis
? Less chances of extubation
? Christmas or locked jaw
? Better tolerated
? Neck contractures

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Breathing / Ventilation :
? Mouth to Mouth
? Mouth to airway ? Safar or Brook airway
? Bag and mask ? Increases aspiration, increases dead space, exhaustive
? Advanced methods ? Endotracheal tube (Best method), LMA, Combitube, Tracheostomy tube
? Automatic ventilators
Contra-Indications for Bag and Mask Ventilation :
? Full stomach
? Aspiration Risk (Pregnancy, Hiatus Hernia)
? Intestinal Obstruction
? Unconscious / Semiconscious patients
? Diaphragmatic Hernia
? Tracheo ? Esophageal fistula
? Meconium aspiration
Monitoring of CPR
? Capnography ? Most reliable, best indicator
? Palpation of Carotid pulse ? Most effective clinical indicator
? Invasive blood pressure
? Central venous oxygen saturation
VENTRICULAR FIBRILLATION OR PULSELESS
VENTRICULAR TACHYCARDIA

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Complications of CPR
? Rib fracture
? Pneumothorax, pneumomediastinum, pneumopericardium
? Injury to diaphragm, stomach, lungs, major vessels, abdominal organs.
Drugs Used in CPR
? Vasopressors - Adrenaline, Noradrenaline
? Inotropes - Dopamine, Dobutamine
? Beta Blockers
? Anticholinergics
? Vasodilators
? Anti-arrhythmics
Drugs Contraindicated in CPR :-
? Calcium ? only indications: Hypocalcemia, Hyperkalemia
? Sodium bicarbonate ? only indications: metabolic acidosis, Hyperkalemia
DEFIBRILLATION
? DC cardioversion: Rx of choice for pulseless tachycardia & ventricular fibrillation.
? Ventricular fibrillation - most common in adults who experience nontraumatic cardiac arrest.
? The time from collapse to defibrillation is the most important determinant of survival.
? Only defibrillation can reverse a ventricular fibrillation.
? Early defibrillation is most likely to improve survival
? Shock should be delivered within 3 min (? 1 min) of arrest.
? Biphasic waveforms are recommended for cardioversion.
Indications
Shocks (J)
Unstable atrial fibrillation
50-100
Unstable atrial flutter/tachycardia
30-50
Monomorphic ventricular tachycardia
100
Polymorphic ventricular tachycardia or ventricular fibrillation
120-200
BASIC LIFE SUPPORT TECHNIQUES


Infant (1-12 months)
Child (>12 months)
Adult
Breathing rate
20 breaths/min
20 breath/min
10-12 breath/min"
Pulse check
Brachial
Carotid
Carotid
Compression rate
>100/min
100/min
100/min
Compression method
Two or three fingers
Heel of one hand
Hands interlaced
Compression/ventilation 30:2
30:2
30:2
ratio
Foreign body
Back blows and chest
Heimlich maneuver
Heimlich maneuver
obstruction
thrusts

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ADVANCED LIFE SUPPORT
Components of ALS
? Cardiac monitoring
? Cardiac defibrillation
? Transcutaneous pacing
? Intravenous cannulation (IV)
? Intraosseous (10) accPss and intraosseous infusion
? Surgical cricothyrotomy
? Needle cricothyrotomy
? Needle decompression of tension pneumothorax
? Advanced medication administration through parenteral and enteral routes (IV, 10, PO, PR, ET,

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? SL, topical, and transdermal)
? Advanced Cardiac Life Support (AILS)
? Pediatric Advanced Life Support (PALS) or Pediatric Emergencies for Pre-Hospital Providers
? (PEPP)
? Pre-Hospital Trauma Life Support (PHTLS), Basic Trauma Life Support (BTLS) or International
? Trauma Life Support (ITLS)
Forms of potentially reversible causes for cardiac arrest, commonly abbreviated as "6Hs & 5Ts"
Hs
Ts
? Hypoxia:
? Tension pneumothorax
? Hypovolemia:
? Tamponade
? Hyperkalemia or hypokalemia
? Toxic and/or Therapeutic
? Hypothermia/Hyperthermia
? Thromboembolism and related
? Hydrogen ions (Acidosis)
? mechanical obstruction
? Hypoglycemia:
INVASIVE RESPIRATORY SUPPORT
Intermittent positive-pressure ventilation (IPPV) May be given with positive end-expiratory pressure (PEEP)
Continuous positive airway pressure (CPAP)
Given via endotracheal tube
Synchronized intermittent mandatory
May be given with pressure support and CPAP
ventilation (SIMV) (volume or pressure
controlled)
Pressure support ventilation (PSV)
Usually given with CPAP
'Lung-protective' ventilatory strategies to
Low tidal volume, reduced airway pressures. Used with
minimize ventilator-associated lung injury
SIMV, PEEP and prolonged inspiratory phase
High-frequency jet ventilation (HFJV)
May be useful in those with lung leak (e.g. bronchopleural
fistula)

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Extracorporeal techniques
May be useful in severe acute respiratory failure
NON-INVASIVE RESPIRATORY SUPPORT
Continuous positive airway pressure (CPAP)
Inspiratory and expiratory pressures the same
Non-invasive positive support ventilation
? CPAP
Bilevel positive airway pressure (BiPAP)
Inspiratory and expiratory pressures set separately
WEANING METHODS:
? The most useful weaning parameters are
o
Arterial blood gas tensions
o
Respiratory rate
o
Rapid shallow breathing index (RSBI).
? The most common techniques to wean a patient from the ventilator include
o
SIMV
o
Pressure support
o
Periods of spontaneous breathing alone on a T- Piece or on low levels of CPAP.
o
Noninvasive positive-pressure ventilation
? The traditional method is to allow the patient to breathe entirely spontaneously for a short time, following
which respiratory support is reinstituted.
MANAGEMENT OF PRE EXISTING DRUG THERAPIES DURING ANAESTHESIA
Oral Hypoglycemic Drugs
Omit morning dose in case of minor surgery
For major surgeries: shift to Insulin 48 hrs before surgery
OCP's
Stop 4 weeks before to decrease thromboembolism
Oral Anti-coagulants
Stop 4 days ahead of surgery & shift to LMW heparins. Heparin should
be stopped one day before surgery.
In case of emergency Vit K is given if at least 6 hrs are available.
If the surgery is to be performed immediately fresh frozen plasma is to
be given.
Unfractionated heparin
stop 6 hrs before surgery
LMWH
stop 12 hrs before surgery
Anti hypertensive drugs
Should be continued. For ACE inhibitors and ARBS's morning dose is
withheld
Anti Anginal Drugs Antithyroid
Should be continued and even morning dose is given.
Drugs, Anti Epileptic Drugs
Levodopa Anticholinesterases
Antiplatelet Drugs
Clopidogrel- stop 1 week before surgery. In emergency platelet
transfusion should be given prior to surgery.
Aspirin can be continued on the day of surgery.
Lithium
Should be stopped 48 -72 Hrs before.
Smoking
Should be ideally stopped 6-8 weeks before (complete ciliary recovery )
Antitubercular Drugs
Should be continued with monitoring of liver function test
Aminoglycosides
Has neuromuscular blocking activity so it is shift to another antibiotic
48 hrs prior to surgery
Fasting guidelines before surgical procedures
Adults
Children
? Clear fluids ? 2 hours
? Clear fluids ? 2 hours
? Semisolids ? 4 hours
? Breast milk ? 4 hours
? Solid foods ? 6hours
? Formula milk, solid foods ? 6 hours

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Indications for Central Venous Catheterization

Pulmonary artery catheterization (with coagulopathy)
External jugular vein
Hemodialysis
Internal jugular vein
Plasmapheresis
Preoperative preparation
Fluid management of ARDS (CVP monitoring)
Pulmonary artery catheterization [with pulmonary compromise or high-level
Right internal
positive end-expiratory pressure (PEEP)]
jugular vein
Emergency transvenous pacemaker
Total parenteral nutrition (TPN)
Subclavian vein
Hypovolemia, inability to perform peripheral catheterization
General purpose venous access, vasoactive agents, caustic medications, radiologic
procedures
Cardiopulmonary arrest
Femoral vein
Hypovolemia, inability to perform peripheral catheterization
Emergency airway management
Inability to lie supine
Central venous oxygen satuation monitoring
*****END*****

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