Risk factors for mortality in patients with low lactate level and septic shock

Background: According to the new definition of septic shock, vasopressor therapy and hyperlactatemia are essential for diagnosis. However, there is controversy regarding the cutoff value for lactate, and prognostic factors in patients with septic shock and hypolactatemia. This study evaluated the prognostic significance of the cutoff value for lactate level in septic shock patients. Methods: The retrospective observational cohort study enrolled 1043 patients aged ≥18 years who meet the revised definition of septic shock. Clinical outcomes of patients with hyperlactatemia were compared with hypolactatemia. Results: Of the 1022 eligible patients, 369 had an arterial lactate level ≤2 mmol/L. More patients in the high lactate group had poor prognosis than in the low lactate group. A high Sequential Organ Failure Assessment score (SOFA) score group was significant (p < 0.001) in predicting lactate levels. On the subgroup analysis of risk factors affecting mortality in the low lactate group, high Acute Physiology And Chronic Health Evaluation Ⅱ (APACHEⅡ) score (p = 0.003), high C-reactive protein (p = 0.034), and chronic heart failure (p = 0.001) were independently associated with 28-day mortality. Conclusion: Arterial lactate is a very reliable diagnostic and prognostic predictor of septic shock. However, despite low arterial lactate, patients with a high APACHEⅡ score, high C-reactive protein levels, and chronic heart failure had a poorer prognosis.