This prospective, randomized, double-blinded study is designed to evaluate the postoperative analgesic effect of the continuous infusion of intravenous nefopam in patients undergoing video-assisted thoracic surgery (VATS). We hypothesize that the continuous infusion of intravenous nefopam can significantly reduce postoperative opioid consumption and pain severity in patients with VATS.

Adult patients undergoing elective unilateral VATS segmentectomy or lobectomy are randomly allocated to receive continuous nefopam infusion (n=45) or not (n=45), in addition to a standard postoperative analgesic regimen comprising of IV fentanyl-based patient-controlled analgesia (PCA). At the end of induction, the nefopam group will receive intravenous nefopam 20mg mixed with 50ml of normal saline, and at the end of surgery this group will receive intravenous nefopam 60mg mixed with 50ml of normal saline at a rate of 2ml/hr. The control group will receive intravenous normal saline 50ml at the end of induction and receive intravenous normal saline 50ml at a rate of 2ml/hr.

Inclusion Criteria:

• Patients scheduled to undergo elective unilateral VATS segmentectomy or lobectomy under general anesthesia
• American Society of Anesthesiologists (ASA) physical classification I-II
• Consent to IV-patient controlled analgesia use
• Willingness and ability to sign an informed consent document

Exclusion Criteria:

• Do not understand our study
• Allergies to anesthetic or analgesic medications
• Continuous local anesthetics infiltration for postoperative pain control
• Patients who receive mechanical ventilation more than 2 hours after surgery
• Pregnancy/Breast feeder
• Medical or psychological disease that can affect the treatment response

Outcomes assessor not involved in this study will investigate the outcomes. The patient will be not informed of the infusion of nefopam by not attaching an identifiable label so that it cannot be distinguished from normal saline.