Don’t Wait for Send-Out Labs! Falsely Elevated Lactate Level in a Case of Ethylene Glycol Poisoning

Introduction: Ethylene glycol (EG) poisoning is one of the fatal causes of high anion gap metabolic acidosis (HAGMA). Early diagnosis and treatment are crucial in reducing morbidity and mortality. Delayed EG blood level results can delay diagnosis, resulting in worse outcomes for the patient. Here, we present a case of EG poisoning that was saved by a lab error.


Description: A 57-year-old woman with a history of depression and alcohol use disorder presented to the ED after being found unconscious. The daughter was not sure if the patient had taken any substances before the incident. In the ED, the patient was lethargic, requiring intubation for airway protection. The patient’s hemodynamics were stable, but her blood work was significant for severe HAGMA with an undetectable bicarbonate level and a lactate of 9.0. The Beta-hydroxybutyrate and the Ammonia levels were 0.08 and 548, respectively. A point-of-care (POC) blood gas showed a pH of 6.78, CO2 of 23, bicarbonate of 1 and lactate of 31. The Ceribell device was negative for active seizures. The toxicology workup was unremarkable, with EG blood tests pending, expected to result in 3-4 days, as it is a send-out lab. A decision was made to proceed with hemodialysis (HD) for severe acidosis and hyperammonemia. The repeat labs showed improvement of the ammonia level to 82, but persistent acidosis with a pH of 7.0 and lactate of 31 on the POC blood gas and 10.2 on the laboratory blood work. In the setting of persistent HAGMA with a significant “lactate gap”, a decision was made to start Fomepizole for treatment of possible EG poisoning. Repeat ABG a few hours later showed pH of 7.53 and bicarbonate of 25.7. On the next day, the patient’s daughter was able to find a suicide note, left by her mother, admitting the ingestion of antifreeze. The patient eventually was successfully extubated, weaned from HD, and discharged to a rehab facility.


Discussion: “Lactate gap” is a reported lab error in the setting of EG poisoning. Due to a similar structure, EG metabolites, glycolate and glyoxylate, are misinterpreted as lactate by many POC blood gas analyzers. This creates a gap between POC and Laboratory analyzers’ lactate levels. Using this gap, in the proper setting, can help to early diagnosis and treatment of EG poisoning, which improves the patients’ outcome.