Preoperative fluid removal volume in patients on dialysis undergoing cardiovascular surgery

Background In patients on dialysis who are scheduled for surgery, the volume of fluid removed preoperatively may influence intraoperative circulatory stability and can affect perioperative complications. However, no clear standards for approaches to preoperative fluid removal have been established. In this study, we investigated the association between preoperative fluid removal volume and early postoperative mortality and complications in patients undergoing dialysis who underwent cardiovascular surgery. Methods We included patients placed on dialysis who underwent cardiovascular surgery between January 1, 2012, and December 31, 2021. Their clinical data were retrieved from electronic medical records. The primary outcome was early postoperative mortality. Secondary outcomes were postoperative complications, postoperative continuous renal replacement therapy (CRRT), and duration of mechanical ventilation. Statistical comparisons were performed using the Wilcoxon rank-sum test and Fisher’s exact test. The optimal cut-off values for fluid removal volume were determined using receiver operating characteristic (ROC) analysis. The patients were classified into two groups based on their preoperative fluid removal volumes (≥ 2,000 mL or < 2,000 ml). Statistical significance was set at p < 0.05. Results In this cohort of 50 patients, the proportion of male patients and the median age were 76.0% and 69.0 years (IQR: 63–73.8), respectively. The preoperative fluid removal volume was significantly associated with early postoperative mortality (p = 0.029), postoperative complications (p = 0.042), and prolonged postoperative mechanical ventilation (p = 0.014). ROC analysis identified 2,250 mL as the optimal cut-off value (sensitivity, 83.3%; specificity, 84.1%). Patients with volumes of ≥ 2,000 mL had a significantly higher early postoperative mortality rate (p = 0.018). Greater fluid removal volumes were associated with increased early postoperative mortality in those with hypotension during preoperative dialysis (p = 0.026). Conclusions Excessive preoperative fluid removal (> 2,000 mL) is associated with increased risks of early postoperative mortality, particularly in patients with hypotension during preoperative hemodialysis. These findings highlight the importance of individualized fluid management through multidisciplinary collaboration.