Endothelial Dysfunction and Nitric Oxyde During Laparoscopic Surgery

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 c…