| Summary: | Objective: To measure the relationship between lactate and mortality in hospital inpatients. Main outcomes of interest were 3-day, 30-day, and 1-year all-cause mortality. Design: Retrospective cohort study, October 2011 to September 2013. Setting: University-affiliated US Veterans Affairs Hospital. Patients: All inpatients with lactate level measured during the study period. Measurements: Analysis of peak lactate level (mmol/L) during the most recent admission for patients who died, and peak lactate level during an admission for surviving patients. Covariates including sepsis, ICU admission, code blue and rapid response calls, medical vs surgical ward, liver disease, kidney disease, and hospice status were recorded. Results: In total, 3325 inpatients were included; 564 patients had sepsis. Median lactate 1.7 mmol/L (interquartile range [IQR] 1.2-2.6). The 3-day, 30-day, and 1-year mortality were 2.5%, 10%, and 24%, respectively. A lactate level cutoff of ⩾4 mmol/L had best test characteristics (sensitivity 52.4%, specificity 91.4%) to predict increased 3-day mortality. Unadjusted risk ratio of death in 3 days for lactate ⩾4 was 10.3 (95% confidence interval [CI] 6.8-15.7). Patients with sepsis had a consistently higher risk of death compared with patients without sepsis for any given level of lactate. Adjusted odds ratio (OR) of 3-day mortality for lactate ⩾4 was 7.6 (95% CI 4.6-12.5); 30-day mortality was 2.6 (95% CI 1.9-3.6); and 1-year mortality was 1.8 (95% CI 1.4-2.6). Lactates in the normal range (<1.7) were also independently associated with 30-day and 1-year mortality. Conclusions: Lactate predicts risk of death in all patients, although patients with sepsis have a higher mortality for any given lactate level. We report the novel finding that serum lactate, including normal values, is associated with long-term mortality.
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