Association between the intraoperative fluid balance during cardiac surgery and postoperative sequential organ failure assessment score: a post hoc analysis of the BROTHER study, a retrospective multicenter cohort study.

Although intraoperative intravenous fluids are commonly administered to reverse intraoperative hypotension during cardiac surgery, the appropriate volume remains unclear. This study aimed to evaluate the relationship between the intraoperative fluid balance and sequential organ failure assessment (SOFA) score in patients undergoing cardiac surgery to determine the impact of intraoperative intravenous fluids on their organs. This was a post hoc analysis using data from a multicenter, retrospective, observational study across 14 intensive care units (ICUs) in Japan. Adult patients admitted to ICUs after elective coronary artery bypass grafting or valve surgery from January 1 to December 31, 2018 were enrolled. We compared patients with intraoperative fluid balance < 20 ml/kg to those with fluid balance ≥ 20 ml/kg and conducted a multiple regression analysis for the SOFA score within 24 h of ICU admission. Of the 1567 included patients, 870 met the eligibility criteria. A total of 725 patients (83%) had an intraoperative fluid balance of ≥ 20 ml/kg. In the univariate analysis, the SOFA score (interquartile range) was 7 (6-8) and 7 (6-9) in the intraoperative fluid balance < 20 ml/kg and ≥ 20 ml/kg groups, respectively (p = 0.017). Multiple regression analysis showed a positive association between intraoperative fluid balance and SOFA score within 24 h of ICU admission [standardized coefficient 0.0065 (95% confidence interval 0.0036-0.0095), p < 0.001]. Intraoperative fluid balance in patients undergoing cardiac surgery was significantly associated with higher SOFA scores within 24 h of ICU admission.