Lab Case 14 – Interpretation

This patient has a compensated respiratory alkalosis

pH 7.65 – severe alkalaemia

pCO2 16 – primary respiratory alkalosis

Compensation :

2/5 rule or normal HCO3- 2X{(40-measured pCO2)/10}

= 24-2X{(40-16)/10} = 19.2

measured HCO3 is 19 – so compensation is complete

electrolytes normal, glucose normal

A-a gradient = 2 so no Aa gradient is present


This patient has a fully compensated acute respiratory alkalosis without A-a gradient. The electrolytes and glucose are normal. Lactate is mildly elevated. The cause is likely to be due to hyperventilation from pain or anxiety. Treatment of pain and supportive care is likely to resolve abnormalities.

Other causes of respiratory alkalosis to be excluded in this patient include salicylate toxicity and early sepsis. The blood results are not consistent with this. You would expect a metabolic acidosis.

Causes of epigastric pain in this patient?