Hyperlactatemia in critically ill patients with acute kidney injury treated with renal replacement therapy in the intensive care unit

Background Hyperlactatemia is common in intensive care unit (ICU) patients. The aim of our retrospective observational study was to analyse the impact of serum lactate on admission on mortality in patients with acute kidney injury (AKI) treated with renal replacement therapy (RRT). Methods During the study period of 4 years, 2939 patients were admitted to the ICU, 503 patients were diagnosed with AKI and 209 of them required RRT. After excluding patients on chronic dialysis and with known malignant disease, we retrospectively analysed 154 patients. Hyperlactatemia was defined as a serum lactate concentration above 4 mmol/L on admission to the ICU. Results The mean age of patients was 62.8 years, and 69.5% were men. The mean Charlson Comorbidity Index (CCI) on admission to the ICU was 3.7 and fifty-six (36.4%) patients had acute hyperlactatemia. All included patients had AKI stage 3 and were treated with RRT, 125 (81.2%) with continuous RRT and 29 (18.8%) with intermittent hemodialysis. The mean length of stay in the ICU was 15.7 ± 13 days and 118 (76.6%) patients died during the 60-day observation period. A Kaplan-Meier survival analysis showed that the survival rate was statistically significantly lower in the group of patients with hyperlactatemia (log-rank; p = 0.032). The univariate Cox regression analysis showed that serum lactate on admission to the ICU significantly predict 60-day survival (HR 1.075; 95%CI 1.015–1.140; p = 0.014). In the multivariate Cox regression analysis, which included age, gender, diabetes, hypertension, chronic kidney disease, estimated glomerular filtration rate, serum lactate, CCI and C-reactive protein, only age (HR 1.031; 95%CI 1.007–1.056; p = 0.011) and serum lactate (HR 1.067; 95%CI 1.004–1.134; p = 0.035) were independent predictors of mortality. Conclusion Our study underscores the independent association between hyperlactatemia of more than 4 mmol/L on admission to the ICU and increased 60-day mortality in patients with AKI treated with RRT. These findings, which have significant implications for the management and prognosis of critically ill patients with AKI, provide a new understanding of the role of serum lactate in patient outcomes. Trial registration: Name of the registry: ClinicalTrials.gov Trial registration number: NCT06565403 Date of registration, followed by the words 'Retrospectively registered' : August, 19,2024 URL of trial registry record: https://clinicaltrials.gov/study/NCT06565403