Impact of Nitric Oxide Metabolites On Early Perioperative Biochemical Changes and Postoperative Complications in High-BMI Patients Undergoing On-Pump CABG: an Exploratory Observational Cohort Study

PURPOSE: Perioperative metabolic and inflammatory changes in patients with elevated body mass index (BMI) undergoing cardiac surgery are critical but incompletely understood, despite their impact on postoperative outcomes. Nitric oxide (NO) metabolites, particularly nitrites and nitrates, are potential early markers of kidney injury and early postoperative inflammatory marker response. This study evaluates perioperative changes in the plasma nitrite/nitrate ratio, selected biochemical variables and intraoperative haemodynamic parameters in overweight and obese patients undergoing on-pump coronary artery bypass grafting (CABG), and examines their association with early postoperative complications. METHODS: In the exploratory observational cohort study, overweight and obese adult patients undergoing on-pump CABG with standard anaesthesia were followed using serial perioperative blood sampling at six perioperative time points (T1-T6), including periods before and after cardiopulmonary bypass (CPB) and the early postoperative phase. Assessed parameters included blood gases, osmolality, NO metabolites, lactate, glucose, creatinine, and inflammatory markers: CRP, leukocyte count. Mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were analysed to provide clinical context. RESULTS: Overweight and obese patients showed no significant differences in baseline or perioperative characteristics. The nitrite/nitrate ratio increased significantly before CPB compared with pre-anaesthesia values (T2 vs. T1, p < 0.001) and remained elevated 10 min after aortic cross-clamping (AoX) (T3 vs. T1, p < 0.01), followed by rapid normalization after clamp release. Significant perioperative changes were also observed in pH, pO₂ and pCO₂, with increased lactate and glucose concentrations and decreased osmolality 10 min after AoX (T3 vs. T1, p < 0.001). These shifts coincided with reduced MAP, SBP, and DBP, and a delayed HR increase (all time points vs. T1, p < 0.001). Exploratory tree-based analyses identified the nitrite/nitrate ratio and aortic cross-clamp duration as variables associated with early postoperative creatinine and CRP levels, respectively. CONCLUSION: The plasma nitrite/nitrate ratio and AoX duration are associated with early postoperative creatinine increase and inflammatory marker response, respectively, in overweight and obese patients undergoing on-pump CABG.