The study will be performed in MiniaUniversity Hospitals, after obtaining approval from the local ethics committee. All patients will have a peripheral IV cannula 18 G inserted; standard non-invasive monitors will be applied. Patients undergoing major abdominal surgery will be divided into 2 groups to receive intrathecal morphine 300 micrograms with or without nalbuphine 1mg prior to anesthesia. General anesthesia is then given to patients.
Intrathecal morphine causes intense itching which is very bothersome. Nalbuphine antagonizes this effect when given intravenously. This trial is to find out if nalbuphine added to intrathecal morphine has an effect on morphine related pruritus while still maintaining adequate analgesia.