Association of red cell distribution width with mortality in cardiac arrest patients: a retrospective analysis based on the MIMIC-IV database

Abstract Background There is a scarcity of studies that covers the relationship between the red cell distribution width (RDW) and the prognosis of cardiac arrest (CA) patients. Moreover, the prognostic value of the changes in RDW during intensive care unit (ICU) hospitalization for CA patients is not investigated. This study focuses on the correlation between RDW measures at ICU admission and RDW changes during ICU hospitalization and the prognosis of CA patients. Methods A retrospective cohort study is used to collect clinical characteristics of CA patients (>18years) that are on their first admission to ICU with RDW data measured from the Medical Information Mart for Intensive Care-IV database. The primary outcomes are 30- and 90-day all-cause mortality. A multivariate Cox regression model is applied to test whether the RDW represents an independent risk factor that affects the all-cause mortality of these patients. Meanwhile, the dose-response relationship between the RDW and the mortality is described by the restricted cubic spine (RCS). Results A total of 1138 adult CA patients are included in this study. Compared to the survivor group, non-survivors show higher level of RDW. The Kaplan-Meier survival curve indicates that the cumulative survival rate of CA patients at 30 and 90 days decreases gradually as the RDW on ICU admission increases (log-rank test, χ 1 2 =46.460,χ 2 2 =47.210, both p-values<0.001), and rising RDW during ICU hospitalization (ΔRDW>=0.4%) is associated with decreased the 30 and 90 days cumulative survival rates (χ 1 2 =23.700,χ 2 2 =25.390, both p-values<0.001). The multivariate Cox regression analysis shows that increasing RDW at ICU admission (≥13.89%) and rising RDW during ICU hospitalization (ΔRDW>=0.4%) are independent risk factors for death at 30- and 90-day on CA patients. RCS illustrates that there is a non-linear relationship between the RDW on ICU admission and the increased risk of mortality of CA patients at 30 (χ 1 2 =11.990, p-value=0.007) and 90 days (χ 2 2 =12.340, p-value=0.006). Conclusions Elevated RDW levels on ICU admission and rising RDW during ICU hospitalization are powerful predictors of all-cause mortality for CA patients at 30 and 90 days, and they can be used as potential clinical biomarkers to predict the bad prognosis of these patients.