Usefulness of the serum lactate concentration for predicting mortality in acute beta-blocker poisoning

Abstract

Context. Serum lactate measured in the emergency department was recently assessed as an excellent prognosticator of drug-overdose fatality, with the optimal lactate cutoff point being 3.0 mmol/L. However, lactate's role has never been specifically studied in beta-blocker poisonings. Objective. We aimed to evaluate the ability of lactate concentrations to predict outcome (survival versus death) in beta-blocker poisoning. Methods. We conducted an 8-year retrospective study for all symptomatic beta-blocker poisonings admitted to our toxicological intensive care unit (ICU). Serum lactate concentrations were measured in 110 patients and final outcomes of survival or death recorded. Results. Lactate concentrations were 1.79 mmol/L [0.8–5.6] (median, 10–90% percentiles) and peak values of 1.9 mmol/L [0.9–9.5] (p < 0.0001). Nine patients (8%) died in the ICU. Admission serum lactate concentrations differed significantly between survivors and fatalities (p = 0.0008). Four patients (44% of the non-survivors) died in the ICU despite lactate concentrations lower than 3.0 mmol/L. The diagnostic characteristics of the 3.0 mmol/L selected lactate cutoff point were 55% sensitivity and 80% specificity. Conclusion. Serum lactate elevation in beta-blocker poisoning is relatively mild on admission despite the presence of significant cardiovascular symptoms. Even if raised in severe poisonings and alone correlate well with prognosis, lactate concentration is not an absolute predictor of beta-blocker-overdose fatality.