Characteristics and predictors of ICU-mortality in critically ill patients with hyperlactatemia requiring CRRT: A retrospective cohort study

Background: Hyperlactatemia is a common complication in critically ill patients with high morbidity and mortality. Hyperlactatemia patients who require continuous renal replacement therapy (CRRT) constitute a subgroup with increased mortality risk. The clinical significance of serum lactate in these patients was not well understood and clearance of lactate using CRRT shown no survival benefits. The aim of this study is to investigate the incidence and non-lactate risk factors for ICU mortality in hyperlactatemia patients who underwent CRRT.

Method: Hyperlactatemia patients with a serum lactate level >2 μmol/L who underwent CRRT between January, 2014 and May, 2021 were retrospectively investigated. Demographic characteristics and clinical data were collected from the electronic medical record system. The primary endpoint was predictors for ICU mortality which were identified by using multivariate logistic regression analysis.

Results: A total of 178 eligible patients were finally included with a mean age of 56.6 ± 17.9 years and a median APACHE II score of 18 (IQR (14-22)). The multivariate regression results showed that male gender (OR 0.55 (95%CI 0.27-1.12), p = 0.1), mechanical ventilation (OR 2.60 (95%CI 1.27-5.34), p = 0.008), history of hypertension (OR 2.40 (95%CI 1.12-5.14), p = 0.02), SOFA score (OR 1.16 (95%CI 1.05-1.28), p = 0.002), AST (OR 1.0005 (95%CI 0.99-1.001), p = 0.08), and PT (OR 1.08 (95%CI 0.99-1.17), p = 0.06) were independently associated with ICU mortality. After adjusting for age, illness severity (APACHE II score), and serum lactate level, the statistical significances of SOFA score (OR 1.16 (95%CI 1.04-1.29), p = 0.005), hypertension (OR 2.25 (95%CI 1.02-4.95), p = 0.04), and mechanical ventilation (OR 2.54 (95%CI 1.22-5.25), p = 0.01) were not affected. The overall ICU mortality was 58.4% (104/178).

Conclusion: The hyperlactatemia patients who underwent CRRT were at increased ICU mortality. Gender, AST, PT, SOFA score, history of hypertension, and mechanical ventilation were independent predictors for ICU mortality. Future studies with prospectively design, large sample size, and subgroup analyses are warranted to validate these findings.