Blood lactate concentration and lactate gap

A discrepancy between a raised blood lactate concentration on a point-of-care blood gas analyser and laboratory measurement of blood lactate concentration is termed a ‘lactate gap’ and is indicative of ethylene glycol exposure. In ethylene glycol poisoning, blood lactate concentration may be falsely raised on some point-of-care blood gas analysers due to interference on the enzymatic assay by the toxic acid metabolites, glycolate and glyoxylate. The laboratory analysis of blood lactate concentration meanwhile may be normal, depending on the assay used.

If this lactate gap is observed in a patient with altered conscious state, it should raise the suspicion of ethylene glycol poisoning; however, the absence of a lactate gap does not exclude ethylene glycol poisoning. Observation of a lactate gap may precede the development of severe metabolic acidosis.