Serum lactate level upon admission to the neuro-intensive care unit and 90-day mortality: A retrospective study

The serum lactate level is a useful predictor of mortality in critically ill patients. However, little is known about the association between the serum lactate level and mortality in patients admitted to neuro-intensive care units (NCUs). The present study aimed to investigate the association between the initial lactate level and 90-day mortality in NCU patients. This retrospective observational study was conducted by reviewing the medical records of adult (age ≥18 years) patients admitted to the NCU at a single tertiary care academic hospital during 2013-2017. The initial lactate level (mmol L^-1) was defined as the serum lactate level measured within 6 h following NCU admission. The final analysis included 2737 patients, of whom 280 (10.2%) died within 90 days of NCU admission. In a receiver operating characteristic (ROC) analysis, the estimated area under the curve (AUC) for the initial lactate level in predicting overall 90-day mortality was 0.55 [95% confidence interval (CI): 0.52-0.59]. The corresponding values for neurologic and non-neurologic disease-related 90-day mortality were 0.76 (95% CI: 0.71-0.82) and 0.49 (95% CI: 0.45-0.53), respectively. In a multivariable Cox regression analysis, a 1-mmol L^-1 increase in the initial lactate level was associated with 1.17- and 1.22-fold increases in overall and neurologic disease-related 90-day mortality, respectively, but not with non-neurological disease-related 90-day mortality (P = 0.422). Elevated lactate levels were related with an increase in overall 90-day mortality among NCU patients. This association was specifically attributed to neurologic disease-related 90-day mortality.