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Postoperative pain control is required after major abdominal surgery, including laparoscopic colorectal surgery. Intravenous oxycodone is widely used for postoperative acute pain control mainly in Europe. The aim of this study is to evaluate the optimal dose of intravenous oxycodone for pain control after laparoscopic colorectal surgery in Korean.

Oxycodone is known to be effective in pain control and has less sedative effect than morphine does. It has been described that distribution of cytochrome P450, which is associated with metabolism of oxycodone, differed between the races. Proper dose of intravenous oxycodone after major abdominal surgery has not been well defined in Korean. The purpose of this study is to evaluate the optimal dose of intravenous oxycodone for pain control after laparoscopic colorectal surgery in Korean based on pain score and side effects.

Inclusion Criteria:

• American Society of Anesthesiologists class 1,2
• Expected surgical time between 2 - 6 hours
• Scheduled for laparoscopic colorectal surgery

Exclusion Criteria:

• Severe dysfunction of liver, heart, kidney, or lung
• Cannot understand numeric rating scale of pain
• Known or suspected allergy to oxycodone
• Previous history of postoperative nausea or vomiting
• Medication of antidepressants
• Postoperative long-term ICU care or prolonged mechanical ventilatory support
• Chronic pain
• Drug abuser
• Hypersensitivity reaction to aspirin or NSAIDs
• Refuse to enroll