Hyperlactatemia in ICU patients: Incidence, causes and associated mortality.

Purpose: To describe the incidence, causes and associated mortality of hyperlactatemia in critically ill patients and to evaluate the association between lactate clearance and in-hospital survival.

Methods: Retrospective cohort study of patients with hyperlactatemia admitted to the ICU. Hyperlactatemia was defined as a blood lactate concentration ≥5mmol/L and high-grade hyperlactatemia a lactate level ≥10mmol/L. Lactate clearance was calculated as the percentage of decrease in lactate concentration from the peak value.

Results: Of 10,123 patients, 1373 (13.6%) had lactate concentration ≥5mmol/L, and 434(31.6%) of them had ≥10mmol/L. The most common causes of hyperlactatemia were sepsis/septic shock and post-cardiac surgery. An association was found between lactate concentration and in-hospital mortality (p<0.001). The area under the receiver-operating-characteristics (ROC) of lactate concentration and the optimal cut off to predict mortality were 0.72 (0.70-0.75) and 8.6mmol/L, respectively. ROC analysis for lactate clearance to predict in-hospital survival showed that the best area under the curve was obtained at 12h: 0.67 (95% confidence interval 0.59-0.75).

Conclusions: Hyperlactatemia was common and associated with a high mortality in critically ill patients. Lactate clearance had limited utility for predicting in-hospital survival.