Lactate-to-Albumin Ratio as an Independent Predictor of 28-Day ICU Mortality in Patients with Hypertension: A Retrospective Cohort Study

Background: This study aims to explore the association between the lactate-to-albumin ratio (LAR) and the risk of mortality in critically ill patients with hypertension. Methods: This is a retrospective cohort study utilizing data from the Medical Information Mart for Intensive Care IV (MIMIC-IV, v3.1) database. Participants were categorized into tertiles based on LAR levels (low: <0.46, intermediate: 0.46–0.81, high: >0.81). The primary outcome was 28-day mortality. Kaplan-Meier curves were used to compare survival probabilities among patients in different LAR tertiles. Multivariable COX proportional hazards regression analysis and restricted cubic spline (RCS) regression were employed to assess the association between LAR levels and mortality in hypertensive patients. Additionally, subgroup and mediation analyses were conducted. Results: A total of 4,504 patients were included in this study. Kaplan-Meier survival curves revealed that hypertensive patients in the highest LAR tertile had the highest mortality rate (log-rank test, P < 0.001). Multivariable COX regression analysis demonstrated that higher LAR levels were independently associated with an increased risk of 28-day mortality (HR: 1.240, 95% CI: 1.138–1.351, P < 0.001). Compared to the lowest LAR tertile, patients in the highest LAR tertile had a significantly increased 28-day mortality risk (HR = 1.229, 95% CI: 1.035–1.459, P = 0.019). In the fully adjusted model (Model 5), the highest LAR tertile was independently associated with a 22.9% increased mortality risk (HR = 1.229, 95% CI: 1.035–1.459, P = 0.019) compared to the lowest tertile. Restricted cubic spline (RCS) regression indicated a non-linear relationship between LAR levels and mortality risk in the unadjusted model (non-linear P-value = 0.026). Subgroup analysis further identified interactions between BMI, antihypertensive therapy, and mortality in hypertensive patients. Finally, mediation analysis suggested that SOFA and SAPS II scores partially mediated the association between LAR and ICU survival time. Conclusion: LAR demonstrates utility as a prognostic marker for 28-day mortality in critically ill hypertensive patients, particularly in those with obesity or untreated hypertension.