Association between serum lactate, lactate clearance rate, and 30-day mortality among patients undergoing mechanical ventilation: A retrospective cohort study of MIMIC-III database

Serum lactate has been used as a prognostic indicator in intensive care unit patients, and however, the single lactate value may not be enough to reflect changes during illness conditions. Herein, this study aims to explore the association between serum lactate and lactate clearance rate and 30-day mortality in patients undergoing mechanical ventilation (MV). Demographic and clinical data of 2628 adults were extracted from the medical information mart for intensive care-III clinical database in this retrospective cohort study. The lactate clearance rate was calculated using the serum lactate at the beginning of MV (T0), and serum lactate at the12 hours after MV beginning (T1). Univariate and multivariate Cox regression analyses were used to screen covariates, and explore the association between serum lactate and lactate clearance rate and 30-day mortality. We also explored these associations in different T0 serum lactate level subgroups. The evaluation indexes were hazard ratios (HRs) and 95% CIs. In addition, receiver operator characteristic (ROC) curve with area under the curve (AUC) was used to reflect the predictive performance of serum lactate and lactate clearance rate on 30-day mortality. A total of 827 (31.47%) mechanically ventilated patients died within 30 days. After adjusting for covariates, elevated T0 (HR = 1.04, 95%CI: [1.02-1.07]) and T1 (HR = 1.07, 95%CI: [1.04-1.10]) serum lactate was both associated with an increased risk of 30-day mortality, while higher lactate clearance rate was negatively associated with the risk of 30-day mortality (HR = 0.64, 95%CI: [0.50-0.81]). Among patients with T0 lactate >= 2 mmol/L, T1 serum lactate >= 4 mmol/L was associated with an increased risk of 30-day mortality, while lactate clearance rate >= 50 was associated with a decreased risk (all P < .05). Moreover, T1 serum lactate had a potential predictive value on 30-day mortality with an AUC of 0.605. Serum lactate and lactate clearance rate were both associated with 30-day mortality in patients undergoing MV. Our results may provide some references for further studies to explore the roles of serum lactate and lactate clearance rate in prognoses of critical patients.