You are a medical student on attachment in ICU. The arterial blood gas (ABG) machine in A&E is currently broken so staff are coming up from A&E to use your machine. You read one set of results as follows:

pH: 7.2
pCO2: 5kPa
pO2: 12 kPa
HCO3-: 18

Which of the following clinical scenarios best fits the ABG results presented above?

A) Aspirin overdose.
B) Opiate overdose.
C) COPD.
D) Panic attack.
E) Pneumonia.



The answer is A. The ABG results above show a metabolic acidosis, which can be caused by 1) ingestion of acid [such as aspirin overdose] 2) accumulation of endogenousn acid [such as DKA] 3) Loss of alkali [such as diarrhoea] and 4) Failure to eliminate acid as in renal failure.

B and C would give a respiratory overdose.
D and E would give a respiratory alkalosis.