Background: The optimal timing of lactate measurement for septic patients in the intensive care unit (ICU) remains controversial, and whether initiating and repeating the lactate measurement earlier could make a difference for septic patients with an elevated lactate level remains unexplored.
Methods: This was a retrospective observational study that included septic patients with an initial lactate level > 2.0 mmol/L after ICU admission, and all data were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. The main exposure of interest was the early lactate measurement, which was defined as an initial lactate level measurement within 1 h after ICU admission. The primary outcome was 28-day mortality.
Results: A total of 2642 eligible subjects were enrolled, including 738 patients who had initial lactate measurements completed within 1 h (EL group) and 1904 patients who had initial lactate measurements completed more than 1 h after ICU admission (LL group). A significant beneficial effect of early lactate measurement in terms of 28-day mortality was observed: the adjusted odds ratio (OR) was 0.69 (95% CI 0.55-0.87; p = 0.001), and the mediation effect of the time to initial vasopressor administration was significant (average causal mediation effect (ACME) - 0.018; 95% CI - 0.005 approximately to - 0.036; p < 0.001). A strong relationship between delayed initial lactate measurement and risk-adjusted 28-day mortality was noted (OR 1.04; 95% CI 1.02-1.05; p < 0.001). Each hour of delay in remeasuring the lactate level was associated with an increase in 28-day mortality in the EL group (OR 1.09; 95% CI 1.04-1.15; p < 0.001). Further analysis demonstrated that repeating the measurement 3 h after the initial lactate measurement led to a significant difference.
Conclusions: Early lactate measurement is associated with a lower risk-adjusted 28-day mortality rate in septic patients with lactate levels > 2.0 mmol/L. A shorter time to the initial vasopressor administration may contribute to this relationship. Repeating the lactate measurement within 3 h after the initial measurement is appropriate for patients whose lactate levels were measured within 1 h of admission.
Keywords: 28-day mortality; Lactate measurement; Remeasurement; Septic patients.