Lactate Clearance and Outcome in Septic Shock Patients with Low Level of Initial Lactate

Background: Serum lactate is a potentially useful biomarker to risk-stratify patients with severe sepsis and septic shock. However, there are only a few studies on the association of serum lactate levels and prognosis in septic shock patients with initial low lactate levels. Methods: To evaluate whether initial and follow-up lactate levels associated with mortality in septic shock patients with low lactate level, we conducted a retrospective observational study of patients with septic shock, who were hospitalized through the emergency department in February−July 2008. Initial lactate level was stratified as low (<4 mmol/L) or high (≥4 mmol/L). The primary outcome was 28-day mortality and multiple logistic regression analysis was used to adjust for potential confounders in the association between lactate clearance and mortality. Results: Of 90 patients hospitalized with septic shock during the study period, 68 (76%) patients had low initial lactate. Mortality at 28 days was 18% in patients with low lactate level. In these patients, initial lactate level was not associated with mortality (p = 0.590). However, increased lactate at follow-up and lactate clearance were associated with mortality (p = 0.006, p = 0.002, respectively). In a multiple logistic regression analysis, increased mortality rate independently associated with age (OR 1.162, 95% CI 1.041−1.298) and lactate clearance (OR 0.654, 95% CI 0.498−0.859). Conclusions: In septic shock patients with a low lactate level, lactate clearance independently associated with a decreased mortality rate. Therefore, lactate clearance could be useful for predicting the outcome in these patients.