Drowning Definitions
- Nonfatal drowning
- Process of drowning interrupted
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- Fatal drowning
- Death from drowning
- Water rescue
- Submersion or immersion without evidence of respiratory impairment
- All other terms should be avoided
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Epidemiology of Drowning
- One of top two leading causes of accidental death in children
- 2/3 of deaths are age < 30
- Young children
- Inability to swim
- Surveillance
- Fencing and locks
- Pools, bathtubs
- Curiosity, play
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- Teens and adults
- Seizures
- Alcohol
- Associated trauma
- Inability to swim
- Exhaustion
- Scuba
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Drowning Overview
- Mammalian diving reflex (sudden cold water immersion)
- Bradycardia, apnea
- Shunting of blood to CNS
- Decreased metabolism
- Children > adults
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- Shock is rare in drowning
- Rule out trauma
- C-spine precautions: Diving, multiple trauma, or unknown circumstances
- Salt vs. fresh water: no effect on survival
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Drowning Survival Factors
- Primary factor is duration of immersion
- Also
- Water temperature
- Age
- Diving reflex
- Associated trauma
- Associated dysbaric problems
- Bystander CPR
- Water contamination
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Low core temperature correlates with bad outcome
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SCUBA Diving Contraindications
- Asthma
- COPD
- Seizures
- Sinus and ear disease
- Syncope
- Panic disorder
- Vertigo
- Poor training
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Diving: Laws of Physics "Fizzyology"
- Henry's Law: The amount of gas dissolved in a liquid is proportional to the partial pressure of the gas in contact with the liquid
- Dalton's Law: Partial pressure of a gas increases with increasing pressure
- Both above - Decompression Sickness and Nitrogen Narcosis
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- Boyle's Law: The volume of a gas varies inversely with the pressure
- Squeeze Syndromes and Barotrauma
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Barotrauma from Diving
- Squeeze Syndromes
- Disorders of descent (Boyle's Law)
- Barotitis Media: "Ear squeeze"
- Pain from pressure on the TM, due to inability to equalize pressure (blocked Eustachian tube)
- TM can rupture with severe vertigo, N&V
- Treatment: Nasal decongestants, maneuvers to open Eustachian tube (Valsalva, et al.)
- Other squeeze syndromes: Sinus squeeze, facemask squeeze, eye squeeze, suit squeeze, lung squeeze
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External / Inner Ear Barotrauma
- External ear barotrauma
- Due to blockage of external auditory canal by cerumen or ear plugs
- Inner ear barotrauma
- Hemorrhage or rupture of the inner ear round window with sensorineural hearing loss = labyrinthine window rupture
- Severe vertigo, N/V, tinnitus, nystagmus, ataxia
- Referral to ENT
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Pulmonary Barotrauma
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Pulmonary Over Pressurization Syndrome
- Rapid uncontrolled ascent (Boyle's Law)
- Dropped weight belt
- BC malfunction
- Panic and charge to the surface
- Expansion of unvented lung gases on ascent results in a “burst lung"
- Must exhale on ascent to "vent" the expanded gases
- Clinical presentation
- PTX, pneumomediastinum, pneumopericardium
- Hemothorax from injured lung
- Arterial gas embolism can occur
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Pulmonary Barotrauma
- Arterial gas embolism or AGE (high morbidity and mortality)
- Pulmonary overpressurization causes alveolar gas to enter systemic circulation
- Air emboli in coronary, cerebral and retinal arteries
- Sudden and dramatic symptoms often with focal neuro findings
- Presents on surfacing or within 10 minutes (unlike decompression sickness, which occurs gradually)
- ALOC is the rule and seizures are common
- Dive chamber "stat" for treatment
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Nitrogen Narcosis
- A disorder at depth from breathing compressed air which may result in drowning
- High concentrations of nitrogen are neurotoxic
- Symptoms
- Euphoria
- Confusion
- Disorientation
- Poor judgment
- Diminished motor control
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- Treatment is controlled ascent to decrease the amount of dissolved nitrogen in the brain
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Dalton's Law
↑ depth = ↑ partial pressure
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Henry's Law
More gas dissolves with higher pressure
Decompression Sickness
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- A disorder of ascent (gas comes out of solution)
- At depth, increased amounts of nitrogen dissolve in blood and tissues
- Ascending too quickly causes nitrogen bubbles to form in blood and tissues
- A spectrum of illnesses depending on location and severity
- Length and depth of dive are the primary determinants of risk
- Obesity is a risk factor (nitrogen is lipid-soluble)
- Two categories: I and II (II more serious)
- Treatment: Recompression in a chamber
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Type I Decompression Sickness
- Affects musculoskeletal, skin, lymphatics
- "The Bends" or "Caisson's Disease"
- Periarticular pain (especially elbows and shoulders) 70% of all cases
- Pruritus, erythema, skin marbling ("cutis marmorata") from venous stasis
- Intravascular nitrogen bubbles cause a wide variety of presentations
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Type II Decompression Sickness
- Central nervous system decompression sickness
- High CNS concentration of nitrogen
- Prickly sensations in the limbs
- Low back and abdominal pain
- Spinal DCS: Limb paresthesias, weakness
- Dermatome sensory distribution is common
- Incontinence, priapism
- Headache, diplopia, dysarthria, inappropriate behavior
- LOC is rare (it is common in cerebral air embolism)
- Symptoms develop gradually hours after surfacing (unlike arterial gas embolism)
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Type II Decompression Sickness
- DCS of the lungs = "The chokes"
- Decompression shock = Vasomotor DCS
- DCS involving cerebellum or inner ear = "The staggers”
- Symptoms the same as inner ear barotrauma
- Cause: Gas bubbles in inner ear or cerebellum
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All decompression syndromes develop slowly
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Miscellaneous Ascent Disorders
- Alternobaric vertigo
- Occurs on ascent
- Caused by unequal middle ear pressures
- Transient vertigo, nausea
- Barodontalgia (squeeze and reverse squeeze)
- Air trapped in a dental cavity expands on ascent, causing tooth pain
- Gastrointestinal barotrauma
- Serious problems are rare
- Eructation, flatulence, bloating, abdominal cramps
- Avoid carbonated beverages and gas-generating foods prior to diving
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Diving Injuries
- Disorders of ascent
- Pulmonary over pressurization syndrome
- Air embolism - sudden
- Decompression illness - gradual
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- Disorders of descent
- Squeeze syndromes
- Nitrogen narcosis (at depth)
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Hyperbaric Chamber
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Recompression Therapy
- Recompression is the definitive treatment for decompression sickness and arterial gas embolism
- Have a low threshold for treatment of DCS
- Delayed onset of symptoms is common
- More subtle symptoms may develop after treatment of major symptoms
- Minor symptoms may progress
- May recompress up to 14 days after symptom onset
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Recompression Therapy
- Risks associated with flying
- Commercial planes pressurized to 5,000-8,000'
- May exacerbate all symptoms of decompression sickness
- May result in new symptoms of decompression sickness for divers without any symptoms initially
- No flying for 3-7 days post-treatment of DCS-1
- No flying for 1 month post-treatment of DCS-2
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Blast Injury Classification
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- Type I: Pulse of pressure (barotrauma)
- Type II: Flying debris (penetrating trauma)
- Type III: Flying humans (deceleration impact)
- Type IV: Toxic gases, radiation, burns
Ear: TM rupture, ossicle disruption
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Lung: Pneumothorax, air emboli
GI: Hollow viscus rupture
CNS: Concussion, air emboli
Top 4 organs
Type I injuries
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High-Altitude Illness (1)
- Pathophysiology of high altitude illness
- Hypoxia-induced over perfusion and increased hydrostatic pressure with capillary leak
- Increased sympathetic activity
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High-Altitude Illness (2)
- Manifestations
- Acute Mountain Sickness (AMS)
- High Altitude Cerebral Edema (HACE)
- High Altitude Retinopathy (HAR)
- High Altitude Pulmonary Edema (HAPE)
- High Altitude Flatulent Expulsion (HAFE)
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- Factors influencing development
- Rate of ascent and final altitude
- Physiology, acclimation, hydration
- Sleeping at altitude (ventilation decreases)
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High-Altitude Illness (3)
- Risk factors
- Prior history of altitude illness
- Residence at an altitude below 900 meters
- Pre-existing cardiopulmonary conditions
- R to L cardiac shunts (listen for a heart murmur) and intrapulmonary shunts
- Pre-existing pulmonary hypertension / mitral stenosis
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- Exertion (physical fitness is not protective)
- Women and age >50 have a lower incidence
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Acute Mountain Sickness
- Common with rapid ascent to 8-10,000 feet
- Headache, nausea, fatigue, insomnia +/- Gl sx
- Worse with drugs, alcohol, sedatives, and any respiratory depressant
- Prophylaxis: Acetazolamide (carbonic anhydrase inhibitor) – actual mechanism unclear
- Renal bicarbonate diuresis and metabolic acidosis
- Increased respiratory drive
- Increased oxygenation since less sleep-related hypoventilation
- Contraindicated in sulfa allergy
- Causes paresthesias, and rarely, aplastic crisis
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- Treatment: NSAIDs, steroids, oxygen, descent
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High-Altitude Pulmonary Edema (1)
- High-altitude pulmonary edema (HAPE)
- Responsible for most altitude-related deaths
- Most commonly on the second night at altitude
- Resting tachypnea and tachycardia
- Most patients also have mountain sickness
- Fever / rales / pink sputum / normal heart size
- Non-cardiogenic heart failure
- Severe hypoxemia and respiratory alkalosis
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High-Altitude Pulmonary Edema (2)
- Treatment of HAPE
- Improve oxygenation with supplemental oxygen
- If rapid reversal does not occur (failure to increase oxygen saturation to above 90% within five minutes) descent is mandatory
- Portable hyperbaric chamber is another option
- Noninvasive ventilation may help
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- Nifedipine to treat pulmonary hypertension
- Inhaled beta-adrenergics for wheezing
- Dexamethasone is not helpful in HAPE (some recent debate exists here)
- Improve oxygenation with supplemental oxygen
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High Altitude Cerebral Edema
- A severe form of acute mountain sickness
- Usually associated with high altitude pulmonary edema
- Increased ICP, cerebral edema
- Ataxia, vomiting, confusion, seizures, coma
- Treatment
- Descent (definitive treatment)
- Steroids, mannitol
- Hyperbaric chamber (Gamow bag)
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Non-Cardiogenic Pulmonary Edema
- Environmental causes
- HAPE
- Thermal injury
- Drowning
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- Other causes
- Toxins: ASA, phenobarbital, CO, opioids
- Strangulation
- Fat emboli, amniotic fluid emboli
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Hypothermia Mechanisms of Heat Loss
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- Radiation: Majority of heat loss
- Conduction: Increases 25-fold when wet
- Convection: Wind chill, rewarming
- Evaporation: Important heat loss mechanism in hot environments
- Respiration: Small but obligate contribution
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Hypothermia Physiology (1)
- Hunter's response (CIVD)
- Cold causes vasoconstriction to preserve heat
- Then Cold Induced Vasodilatation
- Paradoxical undressing
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- Cold-induced diuresis
- Distal collecting tubule dysfunction
- Paradoxical core afterdrop (PCA)
- Warming vasodilates periphery
- Cold, lactate-rich blood returns to core
- Core pH and temperature drop
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Hypothermia Physiology (2)
- Volume resuscitate with NS
- LR is poorly metabolized by cold liver
- Cold coagulopathy: All coag factors and reactions are temperature-dependent
- Glucose: High if diabetic or CVA, low if metabolized in attempt to keep warm
- Thermogenesis: Shivering thermogenesis is lost at 26°C, leading to rapid decompensation
- Oxyhemoglobin curve shifts to the left, increasing oxygen binding of hemoglobin
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Hypothermia Definitions
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- Definition: core temp < 35 °C
- 32-35 °C: Adjustments to retain and generate heat (shivering thermogenesis)
- <32 °C: Slowdown of body functions and metabolism, decreased O2 utilization, CO2 production
- Risk factors: Extremes of age, altered sensorium for any reason, burns, trauma
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Hypothermia Clinical effects
- Pulmonary: Increased risk for aspiration
- CNS: Altered mental status, incoordination, confusion, lethargy, coma
- Renal: Cold diuresis and volume loss
- Vascular: Hyperviscosity, thrombosis, DIC
- Pancreatitis
- Bradycardia and slow A-fib with Osborn J waves
- Myocardial irritability (epinephrine, dopamine and atropine not indicated)
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EKG Consistent With Hypothermia
- Bradycardia with an idioventricular or junctional escape rhythm
- Prominent J waves in the anterior leads
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Osborn "J" Wave of Hypothermia
The name "J" wave is derived from the fact that the wave begins at the "J" point of the ST segment
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Hypothermic Cardiac Arrest
- Hypothermic arrest, core < 30 °C: Aggressive invasive rewarming measures (as indicated)
- PEA versus VFib
- Vfib, Vtach
- Bretylium (helpful if available)
- Amiodarone preferred to lidocaine
- Class III drugs which increase automaticity
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- Single shock patterns better
- Only re-shock when core rises 1-2° C
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Hypothermia External Rewarming Techniques
- Passive external rewarming measures
- Remove wet clothes
- Cover with warm blanket
- Active external rewarming
- Hot water bottles to groin and axillae
- Radiant heaters
- Bair hugger (blows hot air through perforated blankets – pictured)
- Potential problems with external rewarming: paradoxical core afterdrop and acidosis
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Hypothermia Internal Rewarming Techniques
- Active core rewarming: Core temp < 30 °C or cardiac instability evident
- Warm humidified O2
- Warmed IV fluids
- Gastric, bladder, chest or peritoneal lavage with warm NS
- Dialysis, extracorporeal bypass rewarming
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- The patient is not dead until warm and dead (core temp > 30 °C) is false... truly dead patients cannot be rewarmed
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Frostbite
- Frostbite: Local tissue freezing (irreversible)
- Frostnip: Transient freezing (reversible)
- 1st degree: Superficial, erythema, no blisters
- 2nd degree: Full thickness, edema, erythema, clear blisters
- 3rd degree: Hemorrhagic blisters, skin necrosis
- 4th degree: Extension to bone
- Early clear blebs = GOOD
- Early hemorrhagic blebs = BAD
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Frostbite
- Refreezing is VERY BAD
- Causes more damage than waiting for evacuation and definitive treatment
- ED treatment
- Rapid rewarming: Circulating water (40 °C)
- Blister management
- Clear blisters should be debrided
- Hemorrhagic blisters should be left alone
- "Frostbite in January - amputate in July"
- Conservative surgical debridement after demarcation
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Non-freezing Cold Injuries (1)
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- Trench foot / immersion foot: prolonged wet feet (urine)
- Mottled, anesthetic, pulseless foot
- Severe pain upon rewarming/reperfusion
- Hyperhidrosis and cold sensitivity are late findings
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Non-freezing Cold Injuries (2)
- Chilblains: Painful inflammatory skin lesions
- Chronic intermittent exposure to damp non-freezing temperatures
- Cutaneous symptoms 1-12 hours exposure
- Hands, ears, legs, feet
- Treatment: Rewarming, nifedipine, steroids
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This download link is referred from the post: MBBS 2021 Important Topics and Materials for 1st Year, 2nd Year, 3rd Year and Final Year
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