2.4. Intervention protocols
postoperative nausea and vomiting
SDE (nalbuphine in solvent containing benzyl benzoate and sesame oil) and the vehicle solution (solvent containing benzyl benzoate and sesame oil) was prepared in an identical injection syringe within 30 minutes before injection. The research drugs were prepared by a research nurse who did not involve in the clinical care. The surgical procedure was performed under endotracheal intubation general anesthesia and controlled ventilation. Anesthesia was maintained by inhalational anesthetics (desflurane or sevoflurane) at optimal minimal alveolar concentrations and bispectral index levels. After anesthesia induction, SDE or the vehicle solution was injected into the gluteus muscles by the in-charge anesthesiologist under ultrasound guidance. Since study drugs were prepared by the research nurse, the patients, anesthesiologists, surgeons, and research team members who assessed the study outcomes were blinded to the treatment groups. Dexamethasone (5 mg) was given intravenously after induction of anesthesia and intravenous Palonosetron (0.25 mg) was administered in patients who had high risk of developing postoperative nausea and vomiting. Parecoxib (40 mg) and propacetamol (2 g) were administered intravenously at the end of the operation as the standard postoperative MMA.