Absolute lactate value vs relative reduction as a predictor of mortality in severe sepsis and septic shock.

ABSTRACT

PURPOSE: Lactate reduction, a common method of risk stratification, has been variably defined. Among patients with an initial lactate >4mmol/L, we compared mortality prediction between a subsequent lactate ≥4mmol/L to a <10% and <20% decrease between initial and subsequent lactate values. MATERIALS AND METHODS: We performed a single-center retrospective study of patients presenting to the emergency department with an initial lactate ≥4mmol/L and suspected infection. Patients were stratified by lactate reduction using 3 previously identified definitions (subsequent lactate ≥4mmol/L, and <10% and <20% relative decrease in lactate) and compared using multivariable logistic regression. Sensitivity and specificity were compared using McNemar test. RESULTS: A subsequent lactate ≥4mmol/L and a lactate reduction <20% were associated with increased in-hospital mortality (odds ratio [OR], 3.18; 95% confidence interval [CI], 1.24-8.16; P=.02 and OR, 3.11; 95% CI, 1.39-6.96; P=.006, respectively), whereas a lactate reduction <10% was not (OR, 1.13; 95% CI, 0.94-1.34; P=.11). A subsequent lactate ≥4mmol/L and a lactate reduction <20% were more sensitive than a lactate reduction <10% (72% vs 41%, P=.002 and 62% vs 41%, P=.008, respectively) but less specific (57% vs 76%, P<.001 and 67% vs 76%, P=.002, respectively). CONCLUSIONS: A subsequent lactate ≥4mmol/L and lactate reduction <20% were associated with increased in-hospital mortality, whereas a lactate reduction <10% was not. Sensitivity and specificity are different between these parameters.