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.

This is a single-centre, pilot, prospective, randomized, open-label, parallel-group clinical study. Adult patients (>18 years) with documented cardiovascular disease (including coronary artery disease, chronic heart failure, or cerebrovascular disease) and a Revised Cardiac Risk Index (RCRI) ≥2 scheduled for elective laparoscopic abdominal surgery lasting more than 120 minutes were eligible. Key exclusion criteria included pregnancy or lactation, baseline methemoglobin >3%, known hypersensitivity to nitric oxide, chronic use of NO donors or drugs increasing methemoglobin, severe neutropenia or thrombocytopenia, severe renal failure (eGFR <30 ml/min/1.73 m²), poorly controlled diabetes, significant electrolyte disturbances, and participation in another clinical trial.

Patients were randomized in a 1:1 ratio to the intervention or control group using a sealed opaque envelope method with 40 pre-prepared envelopes opened on the morning of surgery by an anaesthesiologist not involved in treatment or data collection. In the intervention group (n=20), iNO was administered at 40 ppm using the AIT-NO-01 "Tianox" generator (RFNC-VNIIEF, Russia) via the inspiratory limb of the anaesthesia ventilator circuit, starting immediately after tracheal intubation and continuing until the end of surgery, with a median inhalation duration of 168 [145; 185] minutes. In the control group (n=20), patients received standard anaesthetic management and mechanical ventilation without iNO. All patients underwent volatile-based general anaesthesia with sevoflurane, fentanyl infusion, and rocuronium, lung-protective ventilation (tidal volume 6-8 ml/kg ideal body weight, PEEP 5-14 cmH₂O), and goal-directed haemodynamic management with norepinephrine as needed; anaesthetic depth was guided by bispectral index monitoring.

The primary endpoint was the perioperative change (Δ from baseline to 12 hours postoperatively) in plasma markers of endothelial dysfunction: total nitric oxide (NOtotal, sum of nitrites and nitrates), endothelin-1 (ET-1), and von Willebrand factor (vWF). Secondary endpoints included 12-hour postoperative levels of intestinal injury markers (intestinal fatty acid-binding protein, I-FABP; lipopolysaccharide-binding protein, LBP), serum creatinine, tissue expression of vascular cell adhesion molecule-1 (VCAM-1) and inducible nitric oxide synthase (iNOS) in colonic samples assessed by immunohistochemistry, time to first defecation, length of hospital stay, and perioperative complications and adverse events classified by the Clavien-Dindo scale. Safety assessments encompassed methemoglobin levels measured every 30 minutes, continuous monitoring of inspired NO and NO₂ concentrations, and standard cardiorespiratory monitoring.

Venous blood was drawn 1 hour before surgery and 12 hours after surgery for measurement of NOtotal, ET-1, vWF, I-FABP, LBP, and creatinine using enzyme-linked immunosorbent assays and standard biochemical methods. Immunohistochemical analysis of VCAM-1 and iNOS expression in colonic tissue (0-3 point semi-quantitative score) was performed on paraffin-embedded specimens using monoclonal antibodies and a standard HRP/DAB detection system. Statistical analyses were conducted with IBM SPSS 26.0; data were described as median [Q1; Q3] or mean±SD, comparisons between groups used t-tests or Mann-Whitney U tests as appropriate, and Wilcoxon tests for within-group changes, with p<0.05 considered statistically significant.

As a pilot study, the sample size (n=40) was chosen empirically without formal power calculation, and the follow-up period was limited to the index hospital stay; the design was open-label with only patients and outcome assessors blinded to group allocation. The protocol was approved by the Local Ethics Committee of Sechenov University (Protocol No. 27-24, November 7, 2024). The authors conclude that intraoperative iNO at 40 ppm in high-risk cardiovascular patients undergoing prolonged laparoscopic surgery is feasible and appears to stabilize endothelial function, attenuate intestinal and renal injury, and shorten hospital stay, warranting confirmation in larger, prospectively registered randomized controlled trials with extended follow-up.

Inclusion Criteria:

• Age ≥18 years.
• Documented cardiovascular disease, including at least one of the following: coronary artery disease, stable angina pectoris (II-III functional class), chronic heart failure (NYHA I-III), prior myocardial infarction, or cerebrovascular disease.
• Revised Cardiac Risk Index (RCRI) ≥2 (moderate/high perioperative risk).
• Scheduled for elective laparoscopic abdominal surgery (e.g., colorectal, gastric, hepatic resections) with expected duration >120 minutes.
• Ability to provide written informed consent.

Exclusion Criteria:

• Pregnancy or lactation.
• Baseline methemoglobin level >3%.
• Known hypersensitivity or contraindication to inhaled NO.
• Chronic intake of NO donors (e.g., nitroglycerin, isosorbide) or drugs known to increase methemoglobin (e.g., lidocaine, prilocaine, benzocaine).
• Severe neutropenia (neutrophils <500/mm³) or severe thrombocytopenia (platelets <30,000/mm³).
• Haemoglobin <7 g/dl.
• Severe renal failure (estimated GFR <30 ml/min/1.73 m²).
• Poorly controlled diabetes mellitus (HbA1c >9% or frequent hypoglycaemia).
• Significant electrolyte disorders (K⁺ <3.0 or >5.5 mmol/l; Na⁺ <125 or >155 mmol/l).
• Any acute exacerbation of chronic disease on the day of surgery.
• Need to convert to open laparotomy during surgery (exclusion from analysis).
• Requirement for extracorporeal life support or other advanced organ support not compatible with protocol procedures.
• Participation in another interventional clinical trial.
• Withdrawal of consent by the patient at any point.
• Development of an allergic or severe adverse reaction to the study intervention

The study is open-label with respect to the intervention, because iNO administration cannot be masked for the personnel delivering anaesthesia. Patients and investigators who collect and analyse clinical and laboratory data are blinded to group assignment; laboratory analyses are performed by staff unaware of treatment allocation.