Falsely elevated point-of-care lactate measurement after ingestion of ethylene glycol

Abstract

Background: A patient presented with severe acidosis and a point-of-care lactate measurement of 42 mmol/L. Mesenteric ischemia was suspected, with a potential need for laparotomy; however, plasma lactate measurements were below 4 mmol/L. Ethylene glycol ingestion was subsequently diagnosed. We therefore wished to determine why discrepancies in lactate measurements occur and whether this "lactate gap" could be clinically useful. Methods: We phlebotomized blood, added various concentrations of metabolites of ethylene glycol, and tested the resulting samples with the 5 most common lactate analyzers. Results: With the Radiometer 700 point-of-care analyzer, glycolate addition resulted in an artifactual, massive lactate elevation, even at low glycolate concentrations. Another major ethylene glycol metabolite, glyoxylate (but not oxalate or formate), caused similar elevations. The i-STAT and Bayer point-of-care analyzers and the Beckman and Vitros laboratory analyzers reported minimal lactate elevations. Lactate gap was determined by comparing the Radiometer result with the corresponding result from any of the other analyzers. Interpretation: We demonstrated how inappropriate laparotomy or delayed therapy might occur if clinicians are unaware of this phenomenon or have access to only a single analyzer. We also showed that lactate gap can be exploited to expedite treatment, diagnose late ethylene-glycol ingestion and terminate dialysis. By comparing lactate results from the iSTAT or Bayer devices with that from the Radiometer, ethylene-glycol ingestion can be diagnosed at the point of care. This can expedite diagnosis and treatment by hours, compared with waiting for laboratory results for plasma ethylene glycol. © 2007 Canadian Medical Association or its licensors.