Download MBBS (Bachelor of Medicine and Bachelor of Surgery) Latest ABG and Acid Base Disorders Lecture PPT
Applications of ABG
To document respiratory failure and assess its severity.
To monitor patients on ventilators and assist in
weaning.
To assess acid base imbalance in critical illness.
To assess response to therapeutic interventions and
mechanical ventilation
ABG EQUIPMENT
Blood gas analyzers use electrodes to determine pH,
partial pressure of carbon dioxide and partial pressure of
oxygen in the blood.
It consist of three electrodes measuring pH, pCO2 and pO2
at 37 degree
It may also measure electrolytes like sodium, potassium
and chloride.
From these outputs, internal computers calculate oxygen
saturation, base excess and bicarbonate level.
Case Study
1. Sheela aged 19 years brought to casuality at 11 AM with
dizziness, tingling of fingers, sweating, breathing heavily and
nausea. O/E: Hyperventilation, carpopedal spasm was found.
Laboratory data:
pH
7.55
Pco2
20 mm Hg
HCO3
24 mmoles/l
1. What kind of acid-base disorder is this girl suffering from?
Explain.
2. What are the common causes of this kind of disorder?
3. Give the compensatory mechanism available in the body to
correct this sort of acid-base imbalance.
1. Respiratory alkalosis (uncompensated)
Tingling of fingers and carpopedal spasm is due to
reduction in ionized calcium caused by increased
binding of calcium to albumin in alkaline pH of ECF.
2. Common cause of respiratory alkalosis is functional
hyperventilation due to anxiety disorders.
It also occurs in cases where the respiratory center in
medulla is over stimulated as in encephalitis,
intracranial surgery, salicylate poisoning and chronic
liver disease
3. In respiratory alkalosis, there is loss of CO2 leading to
decrease in pCO2 and increase in bicarbonate to
carbonic acid ratio.
In an attempt to return the pH towards normal, kidney
excrete more bicarbonate in urine so that bicarbonate
-carbonic acid ratio is brought back to normal
2. Ramakrishnan, 60 years old, a known smoker
attended casuality with exacerbation of bronchial
asthma. The acid base analysis report is given below.
Give your interpretation.
Laboratory data:
pH
7.04
Pco2
90 mm Hg
HCO3
24 meq/L
Respiratory acidosis
Asthma attack are characterized by episodes of airway
obstruction leading to retention of CO2, leading to
increase pCO2,decreased bicarbonate to carbonic acid
ratio.
Renal compensatory mechanisms tend to retain
bicarbonate in the blood which in turn help to raise the
bicarbonate-carbonic acid in order to attain 20:1 ratio so
that normal pH is restored.
Generally respiratory acidosis is caused by disorders that
interfere with respiratory activity- pneumonia, asthma,
pulmonary edema,COPD
Morphine and barbiturate poisoning cause of depression
of respiratory centre leading to respiratory acidosis.
A woman complaining of intractable vomiting suspected of
suffering from pyloric stenosis receiving treatment showed
following acid base data on day 1 and day 2.
Laboratory data on day 1:
pH
7.6
pCO2
40 mm Hg
HCO3
35 meq/L
Laboratory data on data 2 :
pH
7.55
pCO2
45 mm Hg
HCO3
28 meq/L
Kumaran,58 year old peon in a private firm has been suffering from DM for the past 20
years. He was taking irregular treatment for DM. One day he was brought to the
casuality in a stuperosed state. O/E: Fruity odor in breath, Kussmaul's type of breathing
+
Laboratory data
Urine Rothera's Test ? Positive
Plasma Glucose- 450 mg/dl
ABG analysis report
pH
7.2
pCO2
40 mm Hg
HCO3
15 meq/L
Na
140 mmol/L
K
4 mmol/L
Cl
102 mmol/L
1. What is the problem diagnosis? Explain.
2. Calculate the anion gap from given laboratory data?
3. What is the value of normal anion gap?
This post was last modified on 30 November 2021