In the setting of acute cyanide poisoning, it is virtually impossible to obtain a timely cyanide level to help assess toxicity. However, there are two diagnostic tests that can help confirm your diagnosis.
Anion gap metabolic acidosis with elevated lactate
Narrowing of the venous-arterial PO2 gradient
Remember cyanide halts cellular respiration meaning the cells cannot utilize oxygen. Therefore, the venous PO2 should be about the same as the arterial PO2. The cells then switch to anaerobic metabolism, thereby producing lactate.
