Ninety patients were randomly assigned to receive morphine intrathecally either 0.2 mg ( Group I , ITM 0.2 mg , n = 30 ) , 0.5 mg ( Group II , ITM 0.5 mg , n = 30 ) , or 1 mg ( Group III , ITM 1 mg , n = 30 ) dissolved in 5 mL physiological saline before general anesthesia .