Association between hemoglobin-to-red blood cell distribution width ratio and mortality in critically Ill patients with aortic dissection: A retrospective cohort study from MIMIC-IV database

This study aims to reveal the correlation between the hemoglobin-to-red cell distribution width ratio (HRR) and mortality among the patients with aortic dissection (AD). We identified critically ill patients with AD in MIMIC-IV database. The optimal cutoff value of HRR was calculated through ROC curve analysis conducted by using the maximum Youden index for the prediction of survival status. The primary outcome was 30-day mortality, with 90-day and 365-day all-cause mortality as secondary outcomes. The Cox proportional hazard regression models were utilized to analyze the association between baseline HRR and mortality. Restricted cubic splines analysis was utilized to determine the relationship curve between mortality and the HRR level and examine the threshold saturation effect. We further applied Kaplan-Meier survival curve analysis to examine the consistency of these correlations. The interaction test was used to identify subgroups with differences. A total of 540 patients were included, the optimal cutoff value of the HRR was determined as 5.2 and the 30-day, 90-day, and 365-day all-cause mortality rates were 11.3%, 14.8%, and 20%, respectively. Multivariate Cox proportional hazards analysis revealed that the HRR was independently associated with mortality at 30 days (hazard ratio [HR] [95% confidence interval (CI)] 0.82 (0.69-0.98), P = .025), 90 days (HR [95% CI] 0.81 [0.7-0.93], P = .004), and 365 days (HR [95% CI] 0.83 [0.74-0.94], P = .003). Restricted cubic splines regression showed a positive linear association between the HRR and 90-day mortality risk, whereas a curvilinear relationship among 30-day and 365-day mortality. Kaplan-Meier survival curves further confirmed the significant survival disparities across HRR groups. Furthermore, subgroup analysis showed that there was an interaction between HRR and age in all-cause mortality. Low HRR is associated with increased all-cause mortality at 30, 90, and 365 days in critically ill AD patients, highlighting its potential as a prognostic indicator for risk stratification, particularly in elderly patients.