Cardiac Index and Heart Rate as Prognostic Indicators for Short-Term Outcomes in Septic Shock: A Retrospective Cohort Study from the MIMIC-IV database

Septic shock is a life-threatening condition associated with high mortality rates. Monitoring cardiac index (CI) and heart rate (HR) in the intensive care unit (ICU) is crucial for managing septic shock and predicting outcomes. However, the relationship between CI, HR, and mortality risk in septic shock patients remains unclear. This study aimed to investigate the association between different levels of CI and HR and mortality in septic shock patients. Using data from the MIMIC-IV version 2.0 database, sepsis and septic shock were defined according to sepsis-3 criteria. CI was calculated using cardiac output and body surface area. Restricted cubic spline curve analysis was employed to evaluate the incidence of CI in relation to 7-, 14-, 21-, and 28-day mortality. The optimal cutoff for predicted mortality was determined using the Youden index. Kaplan-Meier curves, Cox regression, and logistic regression were used to assess the association between CI, HR, and 28-day mortality. Among 1498 septic shock patients, a U-shaped relationship between CI levels and mortality risk was observed (p < 0.001). CI levels between 1.85–2.8 L/min/m2 were associated with a mortality hazard ratio (HR) < 1, while low CI (HR = 1.87, 95% CI: 1.01–3.49) and high CI (HR = 1.93, 95% CI: 1.26–2.97) were associated with increased mortality risk. The area under the curve (AUC) for HR predicting mortality was 0.70 (95% CI: 0.64–0.76) with a cutoff value of 93.63 bpm. Patients were divided into six subgroups based on HR and CI characteristics, and survival analysis showed higher survival rates in the HR↓+CI normal group, HR↓+CI↓ group, and HR↓+CI↑ group. In conclusion, our retrospective study suggests that monitoring CI and HR in septic shock patients can provide insights into the organismal response, hemodynamic consequences, and prognosis. Healthcare providers should closely monitor changes in these parameters in septic shock patients admitted to the ICU for effective management and treatment.