To ensure a safe and bloodless operating environment during lower limb surgery, a proximal tourniquet is frequently employed. After the tourniquet is loosened, oxygen is rushed back into the ischemic tissue, releasing a flood of free oxygen radicals into the body's bloodstream. peroxidizing macromolecules in cell membranes, including polyunsaturated fatty acids and plasma lipoproteins. Aim: research on the effects of using ketamin, propofol, or a combination of both on tourniquet-induced ischemia reperfusion damage during knee surgery under spinal anathesia. Patients and Methods: Sixty patients of both sexes and ages 20-60years old took part in the study, which took place at AL Zahraa Hospital on the campus of Al Azhar University. the ketamine group (groupI) receives an infusion of 0.5 mg/kg/h of ketamine. in propofol group (group II) an intravenous dose of two mg/kg/h of propofol is given to patients Group III patients recived an infusion of 2 mg/kg of propofol in addition to 0.5 mg/kg of ketamine per hour.