A 24-year-old graduate student was brought to the emergency department in a coma

Question

A 24-year-old graduate student was brought to the emergency department in a comatose state after being found unconscious in his room. A bottle of secobarbital was there on his bed stand. He did not respond to painful stimuli, his respiration was barely perceptible, and his pulse was weak. Blood gases were drawn and yielded the following results:

   pH       7.10

   pCO2       70 mm Hg

   pO2       58 mmHg

   HCO3       20 mmol/L

   O2Hb       80% (reference range, 95%)

What is the patient’s acid-base status? (Acidemia or alkalemia? Metabolic or respiratory?) How do you know?

What caused the profound hypoventilation?

Once the respiratory component returns to normal, what will be the patient’s expected acid-base status?

Explanation / Answer

1. i. since the pH is < 7.35 i.e. 7.10 the patient acid bas status is acidosis or acidemia(normal=7.35-7.45).

and the paco2 is > 45 mmHg i.e. it is respiratory (normal= 35-45mmHg) therefore the patient is suffering from respiratory acidosis.

ii. the normal pH range is 7.35–7.45 (H+ 35–45nmol/L) so if the ph decreased from 7.35 it results in acidosis or acidemia whereas is the ph increased from 7.45 it results in alkalosis or alkaliemia

similarly normal paco2 range is 35–45mmHg (4.7–6.0kPa) so if the paco2 level decreased from 35 it results in metablic whereas is the paco2 level increased from 45 it results in respiratory

2. the cause of the frpfound hypoventilation is reduced arterial oxygen saturation i.e o2 hb is 80%. the normal arterial oxygen saturation is around 95-100%. this causes reduction oxygen carrying capacity of hemoglobin thereby resulting in hypoxia.

3. if the patients respiration can be normal (no hypoventilation) that means the paco2 returns to normal but the ph is < 7.35. still there will be acidosis. that means the amount of dissolved co2 will be more

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