Study drugs and evaluation of PONV

The study drugs comprised a syringe containing 50 ml of dexmedetomidine (2 µg/ml) or normal saline and a syringe containing 1 ml of dexamethasone (5 mg/ml) or normal saline. An anesthesiologist unaware of group assignment administered 1 ml of dexamethasone or normal saline 30 minutes before the end of skin closure followed by infusion of 0.25 ml/kg of dexmedetomidine 0.5 μg/kg or normal saline over 10 minutes. The study drugs were prepared by an independent researcher, while the investigators responsible for evaluating the results of the study were blinded to the group assignment.

The incidence of vomiting, use of rescue antiemetics, and analgesic requirements were recorded at 0 to 1 hours after surgery in the postanesthetic care unit (PACU). The severity of nausea was evaluated using an 11-point numerical rating scale (NRS) (0 = no symptoms; 10 = worst symptoms imaginable). Ramosetron 0.3 mg was administered to patients with nausea >5 points on the NRS or to those who requested an antiemetic. Pain score was also assessed using an 11-point NRS. Intravenous fentanyl 50 μg was administered to patients who reported pain >5 points on the NRS. Mean arterial pressure (MAP), heart rate (HR), and Ramsay sedation score (1 = agitated, anxious, or restless; 2 = oriented, cooperated, and tranquil; 3 = responsive to verbal commands only; 4 = asleep, brisk response to a loud auditory stimulus or a light glabella tap; 5 = sluggish response to a glabella tap or loud auditory stimulus; 6 = no response to a loud auditory stimulus or a light glabella tap) were recorded. Over-sedation was defined as a Ramsay sedation score > 4. Shivering was recorded by nursing staff unaware of group allocations when patients experienced fasciculation or tremor in more than one muscle group without voluntary limb activity.

At 6 and 24 hours after surgery, the incidence and severity of PONV were assessed using the Rhodes Index of nausea, vomiting, and retching (Table 1).¹⁵

Rhodes Index of nausea, vomiting, and retching at 6 to 24 hours after surgery.