Association of Serial Postoperative CASUS Scores with In-Hospital Mortality Among Patients with Prolonged Mechanical Ventilation After Open-Heart Surgery: A Retrospective Cohort Study

Objective: To evaluate the association between serial cardiac surgery score (CASUS) measurements and in-hospital mortality, and to assess the day-specific discrimination of these measurements among patients requiring prolonged mechanical ventilation after open-heart surgery.Methods: This single-center retrospective cohort screened 1,255 adults who underwent open-heart surgery with cardiopulmonary bypass (CPB).Of the 118 patients ventilated for more than 24 hours, 55 lacked the data required for the postoperative day 1 CASUS calculation, leaving 63 patients for analysis.CASUS was assessed on postoperative days 1-5 using linear mixed-effects models, receiver operating characteristic analysis, and logistic regression analysis.Results: Twenty-one patients survived, and 42 died in hospital.CASUS availability decreased from 63 on day 1 to 59 on day 5 because four non-survivors died before subsequent measurements could be obtained.The group-byday interaction was significant (p<0.001).Day 4 and day 5 scores were higher among non-survivors (Welch's t-test, p=0.011 and p<0.001, respectively).Day 5 CASUS showed moderate discrimination [area under the curve 0.729, 95% confidence interval (CI) 0.602-0.856;p=0.004].At a cut-off >8.5, sensitivity was 55.3% and specificity was 90.5%.Among 59 complete cases, day-5 CASUS was associated with in-hospital mortality after adjustment for age, CPB duration, and EuroSCORE II (adjusted odds ratio 1.245, 95% CI 1.076-1.439;p=0.003).Conclusion: Day 5 CASUS was associated with mortality and showed moderate discrimination in this selected cohort, but it represented a late severity marker rather than an early prognostic tool.External validation is required.