Is elevated plasma lactate a useful marker in the evaluation of pure carbon monoxide poisoning?

Objective: To examine whether CO poisoning induces a significant increase in plasma lactate concentration. Design and setting: Prospective observational clinical study in the emergency department and intensive care unit in a university-affiliated teaching hospital. Patients: 146 pure CO poisonings resulting from dysfunction of gas cookers or water heaters. Measurements and results: Patients were classified into four neurological impairment groups: 37% were severely, 8% moderately, and 45% mildly intoxicated, while 1% were asymptomatic. We found only very mild increases in plasma lactate concentration (median 2.30 mmol/l) which, however, was significantly correlated with the severity of neurological impairment and blood CO concentration (1.41 mmol/l, Spearman's test r=0.3). Conclusions: Plasma lactate is mildly elevated in pure CO-exposed patients. This mild increase and the extensive overlap between the groups of neurological impairment severity do not suggest the usefulness of systematic plasma lactate measurement in pure CO poisoning.