Analgesic Effects of Nefopam versus Ketamine in Patients Undergoing Knee Arthroscopy

INTERVENTION: Drug : No premedication is administered before surgery. Upon arrival in the operating room, standard monitoring is applied, including electrocardiography (ECG), pulse oximetry, and noninvasive blood pressure measurement, and vital signs are continuously monitored. Anesthesia is induced with intravenous propofol (1.5–2.0 mg/kg) and rocuronium (0.8 mg/kg), followed by endotracheal intubation approximately 3 minutes later using an endotracheal tube. After induction of general anesthesia, the study drugs are administered according to group allocation as follows: ‐ Group N: Nefopam 0.3 mg/kg is administered as an intravenous bolus, followed by continuous infusion at a rate of 65 µg/kg/h. ‐ Group K: Ketamine 0.3 mg/kg is administered as an intravenous bolus, followed by continuous infusion at a rate of 180 µg/kg/h. To maintain blinding, all study drugs are prepared in identical forms so that neither the patients nor the postoperative evaluators are aware of the group allocation. Preparation and administration of the study drugs are performed by an anesthesiologist not involved in the study. Anesthesia is maintained until the end of surgery with sevoflurane (2–3 vol%) in 50% oxygen and remifentanil (0.05–0.2 µg/kg/min), titrated to maintain a bispectral inde X(BIS) between 40 and 60. Intraoperative hypotension (systolic blood pressure < 90 mmHg) is treated with intravenous phenylephrine 50 µg, and bradycardia (heart rate < 50 beats/min) is treated with intravenous atropine 0.5 mg. At the end of surgery, sugammade Xis administered for reversal of neuromuscular blockade. The endotracheal tube is removed once spontaneous respiration and recovery of consciousness are confirmed, and the patient is transferred to the post‐anesthesia care unit. CONDITION: Diseases of the musculoskeletal system and connective tissue PRIMARY OUTCOME: pain score (numeric rating scale, NRS) SECONDARY OUTCOME: Adverse effects (dizziness, drowsiness, dry mouth, headache, etc.) Incidence of postoperative nausea and vomiting (PONV) Pain score (numeric rating scale, NRS) Sedation score (Modified Observer’s Assessment of Alertness/Sedation, MOAA/S) Time to first rescue analgesic Total consumption of rescue analgesics INCLUSION CRITERIA: i) Patients aged 20–64 years scheduled to undergo knee arthroscopic surgery (meniscectomy or synovectomy) under general anesthesia ii) American Society of Anesthesiologists (ASA) physical status I–II