The Impact of Cardiac Index on Mortality in Patients with Septic Shock: A retrospective study from the MIMIC-IV Database

Abstract Background Septic shock is a life-threatening condition that can lead to organ dysfunction and death. In the ICU, monitoring of cardiac index (CI) is commonly used to guide management and predict outcomes in septic shock patients. However, there is a lack of research on the association between CI and the risk of mortality in this patient population. Therefore, the aim of this study was to investigate the relationship between different levels of CI and mortality in septic shock patients. Methods Data analysis was obtained from the MIMIC-IV version 2.0 database. Sepsis and septic shock were primarily defined by sepsis-3, the third international consensus on sepsis and septic shock. CI was computed using cardiac output (CO) and body surface area (BSA). To evaluate the incidence of CI with respect to each endpoint (7-, 14-, 21-, and 28-day mortality), a restricted cubic spline curve function (RCS) was used. Analyses of KM curves, cox regression, and logistic regression were conducted separately to determine the relationship between various CI and 28-day mortality. Results This study included 1498 patients with septic shock. A U-shaped relationship between CI levels and risk of mortality in septic shock was found by RCS analysis (p < 0.001). CI levels in the range of 1.85–2.8 L/min/m 2 were associated with a mortality hazard ratio (HR) < 1. In contrast, low CI and high CI levels had a significantly increased risk of mortality. According to the characteristics of CI, patients were divided into three groups low CI group (CI < 1.85 L/min/m 2 ,n = 150), CI normal group (CI:1.85–2.80 L/min/m 2 , n = 904), and the high group(CI > 2.80 L/min/m 2 ,n = 444). The KM curves, COX regression, and logistic regression analysis showed that the survival rate the of CI normal group was higher than the other groups. The risk factors of the low CI group, and high CI with ICU 28-day mortality were HR = 1.87 (95% CI: 1.01–3.49), and HR = 1.93 (95% CI: 1.26–2.97), respectively. Conclusion This study found that a cardiac index (CI) of 1.85–2.80 L/min/m 2 was associated with the lowest risk of mortality in patients with septic shock. CIs that were lower or higher than this range were associated with an increased risk of mortality.