Download MBBS ABG and Acid Base Disorders Lecture PPT

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To monitor patients on ventilators and assist in

weaning.

To assess acid base imbalance in critical illness.

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To assess response to therapeutic interventions and

mechanical ventilation
ABG EQUIPMENT

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Blood gas analyzers use electrodes to determine pH,

partial pressure of carbon dioxide and partial pressure of

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oxygen in the blood.

It consist of three electrodes measuring pH, pCO2 and pO2

at 37 degree

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It may also measure electrolytes like sodium, potassium

and chloride.

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From these outputs, internal computers calculate oxygen

saturation, base excess and bicarbonate level.

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Case Study

1. Sheela aged 19 years brought to casuality at 11 AM with

dizziness, tingling of fingers, sweating, breathing heavily and

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nausea. O/E: Hyperventilation, carpopedal spasm was found.

Laboratory data:
pH

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7.55

Pco2

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20 mm Hg

HCO3

24 mmoles/l

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1. What kind of acid-base disorder is this girl suffering from?

Explain.

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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.

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1. Respiratory alkalosis (uncompensated)
Tingling of fingers and carpopedal spasm is due to

reduction in ionized calcium caused by increased

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binding of calcium to albumin in alkaline pH of ECF.

2. Common cause of respiratory alkalosis is functional

hyperventilation due to anxiety disorders.

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It also occurs in cases where the respiratory center in

medulla is over stimulated as in encephalitis,

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intracranial surgery, salicylate poisoning and chronic

liver disease
3. In respiratory alkalosis, there is loss of CO2 leading to

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decrease in pCO2 and increase in bicarbonate to

carbonic acid ratio.

In an attempt to return the pH towards normal, kidney

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excrete more bicarbonate in urine so that bicarbonate

-carbonic acid ratio is brought back to normal
2. Ramakrishnan, 60 years old, a known smoker

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attended casuality with exacerbation of bronchial

asthma. The acid base analysis report is given below.

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Give your interpretation.

Laboratory data:
pH

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7.04

Pco2

90 mm Hg

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HCO3

24 meq/L
Respiratory acidosis

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Asthma attack are characterized by episodes of airway

obstruction leading to retention of CO2, leading to

increase pCO2,decreased bicarbonate to carbonic acid

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ratio.

Renal compensatory mechanisms tend to retain

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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.

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Generally respiratory acidosis is caused by disorders that

interfere with respiratory activity- pneumonia, asthma,

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pulmonary edema,COPD

Morphine and barbiturate poisoning cause of depression

of respiratory centre leading to respiratory acidosis.

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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.

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Laboratory data on day 1:
pH

7.6

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pCO2

40 mm Hg

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HCO3

35 meq/L

Laboratory data on data 2 :

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pH

7.55

pCO2

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45 mm Hg

HCO3

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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

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casuality in a stuperosed state. O/E: Fruity odor in breath, Kussmaul's type of breathing

+

Laboratory data

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Urine Rothera's Test ? Positive
Plasma Glucose- 450 mg/dl
ABG analysis report
pH

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7.2

pCO2

40 mm Hg

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HCO3

15 meq/L

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Na



140 mmol/L

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K

4 mmol/L

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Cl

102 mmol/L

1. What is the problem diagnosis? Explain.

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2. Calculate the anion gap from given laboratory data?
3. What is the value of normal anion gap?