Lactate, lactate clearance and outcome after cardiac arrest: a post-hoc analysis of the TTM-Trial

Background: Admission lactate and lactate clearance are implemented for risk stratification in sepsis and trauma. In out-of-hospital cardiac arrest, results regarding outcome and lactate are conflicting. Methods: This is a post-hoc analysis of the Target Temperature Management trial in which 950 unconscious patents after out-of-hospital cardiac arrest were randomized to a temperature intervention of 33°C or 36°C. Serial lactate samples during the first 36 hours were collected. Admission lactate, 12-hour lactate, and the clearance of lactate within 12 hours after admission were analyzed and the association with 30-day mortality assessed. Results: Samples from 877 patients were analyzed. In univariate logistic regression analysis, the odds ratio for death by day 30 for each mmol/L was 1.12 (1.08-1.16) for admission lactate, P <.01, 1.21 (1.12-1.31) for 12-hour lactate, P <.01, and 1.003 (1.00-1.01) for each percentage point increase in 12-hour lactate clearance, P =.03. Only admission lactate and 12-hour lactate levels remained significant after adjusting for known predictors of outcome. The area under the receiver operating characteristic curve was 0.65 (0.61-0.69), P <.001, 0.61 (0.57-0.65), P <.001, and 0.53 (0.49-0.57), P =.15 for admission lactate, 12-hour lactate, and 12-hour lactate clearance, respectively. Conclusions: Admission lactate and 12-hour lactate values were independently associated with 30-day mortality after out-of-hospital cardiac arrest while 12-hour lactate clearance was not. The clinical value of lactate as the sole predictor of outcome after out-of-hospital cardiac arrest is, however, limited.