Ulinastatin attenuates perioperative nitric oxide surge and postoperative delirium in cardiac surgery: a prospective cohort study with molecular docking and experimental validation

BACKGROUND: Postoperative delirium (POD) after cardiac surgery correlates with endothelial dysfunction, but the role of dynamic nitric oxide (NO) changes remains unquantified. This study investigates whether perioperative NO fluctuations predict POD and the potential mechanism of ulinastatin in regulating NO. METHODS: This integrated study combined clinical investigation, in vitro experiments, and network toxicology-guided molecular docking. We prospectively enrolled 264 adults undergoing elective cardiac surgery, measuring plasma NO preoperatively, immediately post-surgery, and 24 hours post-surgery. In vitro, we assessed ulinastatin's efficacy in attenuating hypoxia/inflammation-induced NO overproduction and preserving endothelial barrier integrity. Network toxicology and molecular docking identified ulinastatin-NO regulatory targets. RESULTS: Among 264 patients, 60 (22.7%) developed POD. Preoperative NO levels did not differ significantly between POD and non-POD groups, but significantly higher NO levels were observed in POD patients both immediately and 24 hours post-surgery. A greater increase in NO from pre- to immediately post-surgery was independently associated with POD (adjusted OR, 1.03; 95% CI, 1.01-1.05, P = 0.016), and changes from immediate to 24-hour post-surgery were associated with in-hospital mortality (OR, 1.06; 95% CI, 1.00-1.13; P = 0.042). Subgroup analyses revealed significant interactions with ulinastatin administration, operative duration, and cardiopulmonary bypass. In vitro, ulinastatin dose-dependently attenuated NO overproduction and preserved endothelial barrier integrity in both POD plasma and oxygen-glucose deprivation models. Network toxicology prioritized 92 core targets mediating NO-induced neurovascular injury, with molecular docking confirming ulinastatin's high-affinity binding to PTGS2, MMP3, ACE, CTSD, F2, and SIRT1, supporting its mechanistic link to POD regulation. CONCLUSIONS: Dynamic perioperative NO surges independently predict POD and postoperative mortality in cardiac surgery. Ulinastatin mitigates this risk by suppressing pathological NO elevation and preserving endothelial integrity, supporting a biomarker-guided neuroprotection strategy.