This single-centre, pilot, prospective, randomized, open-label clinical trial evaluated the effect of intraoperative inhaled nitric oxide (iNO) on endothelial function, intestinal and renal injury biomarkers, and early clinical outcomes in high-risk cardiovascular patients undergoing prolonged laparoscopic abdominal surgery (\>120 minutes). Forty adults with cardiovascular disease and an RCRI ≥2 were randomized 1:1 to receive either iNO at 40 ppm via the ventilator circuit from post-intubation to the end of surgery or standard anaesthetic management without iNO. The primary endpoint was the 12-hour postoperative change in endothelial dysfunction markers (total nitric oxide, endothelin-1, von Willebrand factor); secondary endpoints included markers of intestinal and renal injury (I-FABP, LBP, creatinine), tissue expression of VCAM-1 and iNOS, postoperative complications, gastrointestinal recovery, and hospital length of stay.