Major bleeding is defined according to International Society on Thrombosis and Haemostasis (ISTH) criteria as any of the following within 30 days post-surgery:
Fatal bleeding; OR Symptomatic bleeding in a critical area or organ (e.g., intracranial, intraspinal, intraocular, retroperitoneal, pericardial, non-operated joint, or intramuscular with compartment syndrome); OR Extrasurgical site bleeding causing ≥20 g/L hemoglobin drop or requiring ≥2 units of blood transfusion within 24-48 hours; OR Surgical site bleeding requiring re-intervention or causing delayed mobilization, prolonged hospitalization, or deep wound infection; OR Unexpected/prolonged surgical site bleeding causing hemodynamic instability with ≥20 g/L hemoglobin drop or transfusion of ≥2 units within 24 hours.