Low central venous oxygen saturation on critical care unit admission is associated with higher in-hospital mortality in critically ill patients with acute myocardial infarction.

BACKGROUND: Acute myocardial infarction (AMI) remains a major contributor to global morbidity and mortality, necessitating early risk stratification in critically ill ventilated patients. Central venous oxygen saturation (ScvO2) reflects systemic oxygen balance and guides hemodynamic therapy. However, current AMI risk models do not incorporate ScvO2 or similar parameters, and the association of critical care unit (CCU) admission ScvO2 with in-hospital mortality remains poorly characterized specifically in critically ill AMI patients requiring mechanical ventilation. This knowledge gap limits ScvO2's evidence-based use. Therefore, this study aims to evaluate the independent association between ScvO2 at CCU admission and in-hospital mortality in this population. METHODS: We conducted a post hoc analysis of a prospective cohort of critically ill AMI patients admitted to the CCU between August 2021 and January 2022. Inclusion criteria were age ≥18 years, confirmed AMI, and mechanical ventilation requirement. Baseline variables were collected at CCU admission. ScvO2 was measured via central venous catheterization using calibrated blood gas analyzers. The primary endpoint was in-hospital mortality. Covariates related to ScvO2 and in-hospital mortality were identified using a directed acyclic graph, and highly collinear variables were removed using the variance inflation factor. Multivariable logistic regression and restricted cubic spline analysis were used to examine the independent association between ScvO2 and mortality. Subgroup analyses were performed to further explore the relationship. RESULTS: A total of 179 patients were enrolled, with a median age of 60 years, 70.95% being male, and an in-hospital mortality rate of 26.26%. After full adjustment for time to reperfusion, left ventricular ejection fraction, tricuspid annular plane systolic excursion, arterial oxygen saturation, C-reactive protein, albumin, anterior wall myocardial infarction, frailty score at admission, Sequential Organ Failure Assessment (SOFA) score at admission, intra-aortic balloon pump and use of vasopressors or inotropes, each 1% increase in ScvO2 was associated with a 5% lower mortality risk [odds ratio (OR) =0.95, 95% confidence interval (CI): 0.91-0.98, P=0.004]. When analyzed by tertiles, patients in the highest ScvO2 tertile (tertile 3) demonstrated an 82% lower mortality risk compared to the lowest tertile (tertile 1) (OR =0.18, 95% CI: 0.06-0.55, P=0.003), while tertile 2 patients showed no statistically significant difference versus tertile 1 (OR =1.02, 95% CI: 0.41-2.25, P=0.97), with a significant P for trend of 0.004. Subgroup analyses confirmed the consistent association across different patient characteristics. CONCLUSIONS: In critically ill ventilated AMI patients undergoing ScvO2 monitoring, lower ScvO2 at CCU admission is associated with higher in-hospital mortality. As an early and easily obtained parameter, ScvO2 may facilitate risk stratification and identify high-risk patients needing closer monitoring and timely intervention.