Find the Adequate Dose of Nalbuphine for Laparoscopic Cholecystectomy

Nalbuphine is a FDA approved noncontrolled drug of opioid. And it had been applied for post operative pain for different surgeries, claiming that less nausea and vomiting with the same analgesic effect when comparing with morphine. However, several studies concerning post pain management usually used nalbuphine 0.15‐0.3 mg/kg for laparoscopic cholecystectomy. If the analgesic effect of nalbuphine is similar with morphine, less nalbuphine injection could reduce the side effects of opioid. The investigators will randomize patients into three groups of different initial nalbuphine dose for post laparoscopic cholecystectomy surgical pain, and set patient control analgesia machine with nalbuphine for further pain management. If the pain or side effects of opioid were intolerable, the investigators will change pain medications into NSAIDs or other adequate medications to comfort the patient. The primary outcome were numerical rating pain score and consumption of nalbuphine. The secondary outcomes were nausea, vomiting, pruritus and satisfactory score, and if any other medications use.