Intraoperative High-Volume Diuresis During Off-Pump Coronary Artery Bypass Grafting: Risk Factors and Clinical Impact

Background: Intraoperative high-volume diuresis is a common but under-recognized phenomenon during off-pump coronary artery bypass grafting (OPCABG). Its clinical correlates and implications for perioperative management remain incompletely characterized. Methods: This single-center retrospective cohort study included 1274 adults undergoing elective OPCABG between January and August 2025. High-volume diuresis was defined as urine output ≥ 5 mL·kg^-1·h^-1. Multivariable logistic regression was used to identify factors independently associated with intraoperative high-volume diuresis. Model discrimination was assessed using the area under the receiver operating characteristic curve (AUC). Results: High-volume diuresis occurred in 39.6% of patients. Older age, hypertension and greater intraoperative fluid infusion were independently associated with high-volume diuresis, whereas preoperative diuretic and greater cumulative exposure to systolic blood pressure < 100 mmHg were inversely associated with diuresis. The multivariable model demonstrated acceptable discrimination (AUC = 0.756). Postoperative outcomes, including acute kidney injury, duration of mechanical ventilation, intensive care unit stay, and hospital length of stay, did not differ between groups. Conclusions: Intraoperative high-volume diuresis during OPCABG reflects complex physiological and hemodynamic responses and can be anticipated based on preoperative and intraoperative factors. These findings support a more individualized interpretation of urine output and perioperative management strategies in OPCABG.