Serum lactic acid in the evaluation of outcome in the ICU

Introduction

The purpose of this study was to determine the utility of an initial serum lactate measurement for identifying high risk of death in patients admitted to the ICU.

Methods

In a cohort study at a tertiary-care nontrauma medical–surgical ICU, we included all ICU admissions (May 2007 to February 2008) from a prospectively collected ICU database. Patients' gender, age, admission physiologic measurements, lactic acid, and APACHE IV score were noted. Outcome was acute phase death (death within 3 days of admission) and inhospital death. Outcome was stratified by the initial serum lactic acid level in three groups: low, 0.0 to 2.0; intermediate, 2.1 to 3.9; high, 4.0 mmol/l or above.

Results

Total of 882 patients were included in the study, acute phase death rates were 2.5%, in the low group, 5.1% in intermediate group and 8.1% in the high group, whereas inhospital mortality rates were 13.9%, 28.6%, and 38.7%, respectively. Acute-phase deaths and inhospital deaths increased linearly with lactate. An initial lactate ≥ 4.0 mmol/l was associated with at least a threefold higher odds ratio for both acute-phase deaths 2.8 (95% CI = 1.1 to 7.3) and inhospital mortality 3.4 (95% CI = 2.0 to 5.8).

Conclusion

An initial lactate ≥ 4.0 mmol/l substantially increases the probability of acute-phase death and inhospital mortality in critically ill patients.