A normal (or negative) anion gap does NOT rule out salicylate toxicity

3 out of 5 stars Salicylate toxicity in the absence of anion gap metabolic acidosis. Bauer S, Darracq MA. Am J Emerg Med  2016 Jul;34(7):1328.e1-3 Reference Moderate-to-severe salicylate toxicity typically presents with a combined metabolic acidosis and respiratory alkalosis. Often, the arterial blood gas shows a pH quite near the normal 7.4, but with decreased pCO2 and decreased bicarbonate. However, occasional case reports have shown that in these cases the anion cap may, rarely, but normal or even negative. This seems to be related to specific electrodes that measure chloride level loosing selectivity as they age, and mistaking the salicylate ion for chloride. This artifactual hyperchloremia lowers or abolishes the anion gap. No need to go into the details of this case, which again illustrates this phenomenon. The key take-home lesson: If you suspect salicylate toxicity in a patient with a metabolic acidosis, the absence of an elevated anion gap does not rule-out the diagnosis. Related posts: Pearl: falsely normalized anion gap in salicylate overdose Salicylate toxicity can present with a normal anion-gap metabolic acidosis  
Source: The Poison Review - Category: Toxicology Authors: Tags: Medical anion gap aspirin poisoning laboratory error salicylate toxicity Source Type: news