Yinhe Cai ¹ Yao Zhang ¹ Ningzhi Zhou ¹ Yong Tang ¹ Haixia Zheng ¹ Hong Liu ¹ Jiahua Liang ² Rui-Xiang Zeng ³ Shengqing Song ¹ Yu Xia ^1*

• ¹ The Third Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou, China
• ² Meizhou Chinese Medicine Hospital, Meizhou, Guangdong Province, China
• ³ Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, China

Background: A systemic inflammatory response occurs after cardiac arrest (CA), resulting in brain and cardiovascular dysfunction. The red blood cell distribution width (RDW) to serum albumin ratio (RAR) is widely explored in various inflammation-related diseases. However, the predictive value of RAR for the prognosis of CA is unclear. We aimed to explore the correlation of RAR index with the 30-day and 180-day mortality risk in post-CA patients.Methods: Clinical data were extracted from the MIMIC-IV database. Based on RAR levels (<3.7, 3.7 -4.5, >4.5), enrolled patients were divided into three tertiles. Restricted cubic spline (RCS), Kaplan-Meier (K-M) survival curves, and Cox proportional hazards regression model were performed to explicate the relationship between RAR index and all-cause mortality risk. Subgroup analyses was also performed to increase stability and reliability. The receiver operator characteristic (ROC) analysis was used to assess the predictive ability of RAR index, red blood cell distribution width and serum albumin for 180-day all-cause mortality.Results: A total of 612 subjects were eligible, including 390 males, with a mean age of 64.1 years. A nonlinear relationship was shown between RAR index and 180-day all-cause mortality, with a hazard ratio (HR) >1 when RAR level more than 4.54. The K-M survival curve preliminarily showed that patients in higher tertiles (T2 and T3) of RAR index presented lower 30-day and 180-day survival rates. An elevated RAR index was significantly correlated with an increased 30-day (adjusted HR 1.08, 95%CI 1.01-1.15) and 180-day mortality (adjusted HR 1.09, 95%CI 1.03-1.16). According to the ROC curve, the RAR index outperformed the RDW and albumin in predicting all-cause 180-day mortality [0.6404 (0.5958, 0.6850) vs. 0.6226(0.5774, 0.6679) vs. 0.3841(0.3390, 0.4291)]. The RAR index on 180-day mortality was consistent across subgroups, and a significant interaction was observed among white or patients complicated with chronic pulmonary disease or without cerebrovascular disease.RAR index is an independent risk factor for 30-day and 180-day all-cause mortality in post-CA patients. The higher the RAR index, the higher the mortality. Elevated RAR index may be positively associated with adverse prognosis in post-CA patients, which can remind clinicians to quickly assess these patients.