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Cardiac index and heart rate as prognostic indicators for mortality in septic shock: A retrospective cohort study
Chansokhon Ngan1, Xueying Zeng1, Thongher Lia2
1Department of Critical Care Medicine, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China.
Insights
Septic shock patients with low or high cardiac index (CI) face increased mortality risk. Intermediate CI levels, especially with lower heart rates (HR), are associated with better survival outcomes in the ICU.
Area of Science:
- Critical Care Medicine
- Cardiovascular Physiology
- Sepsis Research
Background:
- Septic shock is a critical condition leading to organ dysfunction and mortality.
- Cardiac index (CI) and heart rate (HR) are vital signs monitored in intensive care units (ICUs).
- Limited research exists on the combined impact of CI and HR on septic shock mortality.
Purpose of the Study:
- To investigate the relationship between different levels of cardiac index (CI) and heart rate (HR) and mortality in septic shock patients.
- To determine optimal CI and HR thresholds for predicting mortality risk.
- To explore the combined effects of CI and HR on patient outcomes.
Main Methods:
- Retrospective analysis of 1498 septic shock patients from the MIMIC-IV database.
- Sepsis and septic shock defined using Sepsis-3 criteria.
- Restricted cubic spline curves (RCS) used to assess CI-mortality relationship; Youden index for HR cut-off determination; KM curves, Cox, and logistic regression for survival analysis.
Main Results:
- A U-shaped relationship was observed between CI and mortality risk (p < 0.001).
- Intermediate CI (1.85-2.8 L/min/m²) was linked to lower mortality.
- Both low CI (HR=1.87) and high CI (HR=1.93) significantly increased mortality risk. Heart rate cutoff for mortality prediction was 93.63 bpm (AUC=0.70).
- Patients with lower HR and intermediate CI showed higher survival rates. Higher HR combined with any CI level increased mortality risk (HRs ranging from 2.91 to 5.77).
Conclusions:
- Monitoring CI and HR in septic shock patients aids in predicting prognosis and hemodynamic status.
- Healthcare providers should closely observe CI and HR trends in ICU patients with septic shock.
- The combined assessment of CI and HR may offer valuable insights into patient management and outcomes.
Background:
Septic shock is a life-threatening condition that can lead to organ dysfunction and death. In the ICU, monitoring of cardiac index (CI) and heart rate (HR) 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 HR 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 HR 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. The optimal cutoff value for predicted mortality was determined using the Youden index. Analyses of KM curves, cox regression, and logistic regression were conducted separately to determine the relationship between various CI and HR 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 within the intermediate range of 1.85-2.8 L/min/m2 were associated with a mortality hazard ratio (HR) < 1. In contrast, low CI (HR = 1.87 95% CI: 1.01-3.49) and high CI (HR = 1.93 95% CI: 1.26-2.97) had a significantly increased risk of mortality. The AUC for heart rate prediction of mortality by Youden index analysis was 0.70 95%CI:0.64-0.76 with a cut-off value of 93.63 bpm. According to the characteristics of HR and CI, patients were divided into six subgroups HR↓+CI intermediate group (n = 772), HR↓+CI↓ group (n = 126), HR↓+CI↑ group (n = 294), HR↑+CI intermediate group (n = 132), HR↑+CI↓ group (n = 24), and HR↑+CI↑ group (n = 150). The KM curves, COX regression, and logistic regression analysis showed that the survival rates the of HR↓+CI intermediate group, HR↓+CI↓ group, and HR↓+CI↑ were higher than the other groups. The risk factors of HR↑+CI intermediate group, HR↑+CI↓, and HR↑+CI↑ with ICU 28-day mortality were HR = 2.91 (95% CI: 1.39-5.97), HR = 3.67 (95% CI: 1.39-11.63), and HR = 5.77 (95% CI: 2.98-11.28), respectively.
Conclusion:
Our retrospective study shows that monitoring cardiac index and heart rate in patients with septic shock may help predict the organismal response and hemodynamic consequences, as well as the prognosis. Thus, healthcare providers should carefully monitor changes in these parameters in septic shock patients transferred to the ICU for treatment.
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