Park 2012.

Methods	RCT, 2 parallel groups
Participants	Number: 42 men (n = 19) and women (n = 23) Country: Korea Surgery: laparoscopic cholecystectomy, general anaesthesia, elective Age: 18 to 60 years ASA: I or II Other inclusion criteria: none reported Exclusion criteria: body mass index > 30 kg/m2, allergy to any medications, renal or hepatic insufficiency, neurological or psychiatric disease, preoperative heart rate < 45 beats/min, antihypertensive medication with clonidine or other alpha‐2 agonist
Interventions	Dexmedetomidine 1 µg/kg as intravenous bolus over 10 minutes before induction of anaesthesia and then 0.5 µg/kg/h continuously until removal of the gall bladder (n = 21) vs Normal saline administered in the same way (n = 21) All participants: Premedication: glycopyrrolate 0.2 mg Anaesthesia and during surgery: propofol (1.0 mg/kg initially and repeated bolus of 10 mg until BIS score < 60). Rocuronium 0.6 mg/kg. Sevoflurane. Neostigmine and glycopyrrolate. If heart rate was < 40 beats/min, atropine 0.5 mg was administered to participants. Ephedrine 10 to 20 mg if systolic blood pressure < 80 mmHg. Ketorolac 30 mg and dexamethasone 8 mg after induction of anaesthesia. Beforecreation of pneumoperitoneum, 0.25% bupivacaine (3 mL) was infiltrated intracutaneously and subcutaneously at each trocar insertion site After surgery: ondansetron 4 mg in case of PONV, repeated if necessary
Outcomes	VAS pain at 6 and 24 hours PO Total amount of intravenous 'rescue' tramadol at 24 hours PO (when the patient requested analgesics or had VAS pain > 4, 30 mg of ketorolac was injected intravenously; 30 minutes later if VAS was still higher than 4, patients received tramadol 50 mg intravenous boluses. If VAS pain was still greater than 4 after another 30 minutes, 20 µg of intravenous fentanyl was administered)
Notes	The amount of propofol differed between groups with (mg, mean, SD) 83 ± 23.4 in the dexmedetomidine group vs 117 ± 33.9 in the placebo group No report described the amount of rescue fentanyl. It was reported that 2 participants in the control group and none in the intervention group needed administration of fentanyl. No report on the number of participants needing ketorolac and tramadol; only total amounts administered were reported, showing a significant difference between groups for intravenous ketorolac (mg, mean, SD) with 43.5 ± 18 in the dexmedetomidine group vs 66 ± 39.6 in the placebo group Study authors contacted for details of relevance for risk of bias assessment, without luck
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Patients were randomly allocated" Comment: Nothing else stated. Unclear how it was done
Allocation concealment (selection bias)	Unclear risk	Nothing reported
Blinding of participants and personnel (performance bias) Pain, 'rescue' analgesia, postoperative sedation	Unclear risk	Nothing reported
Blinding of participants and personnel (performance bias) PONV	Unclear risk	Not relevant
Blinding of participants and personnel (performance bias) Time to first passage of flatus or stool	Unclear risk	Not relevant
Blinding of participants and personnel (performance bias) Time to first out‐of‐bed mobilization	Unclear risk	Not relevant
Blinding of participants and personnel (performance bias) Post‐interventional complications or side effects	Unclear risk	Not relevant
Blinding of outcome assessment (detection bias) Pain, 'rescue' analgesia, postoperative sedation	Unclear risk	Quote: VAS pain was assessed "after operation by an anaesthesiologist who was not involved in the study" Comment: Nothing stated about rescue analgesia, but one might assume that the analgesia was administered by the same person assessing VAS pain. But as nothing was reported about blinding of participants, risk of bias remained unclear
Blinding of outcome assessment (detection bias) PONV	Unclear risk	Not relevant
Blinding of outcome assessment (detection bias) Time to first passage of flatus or stool	Unclear risk	Not relevant
Blinding of outcome assessment (detection bias) Time to first out‐of‐bed mobilization	Unclear risk	Not relevant
Blinding of outcome assessment (detection bias) Post‐interventional complications or side effects	Unclear risk	Not relevant
Incomplete outcome data (attrition bias) All outcomes	Low risk	No incomplete data
Selective reporting (reporting bias)	High risk	No protocol was available. Several outcomes were not prespecified but seemed to be determined post hoc, and use of antiemetics among patients with PONV was measured according to the Methods section but was not reported. Amount of rescue analgesia was not prespecified but probably was intended as an outcome pre hoc. Time points preselected for VAS pain were not exactly the same as those reported (prespecified time points 8 and 12 hours postoperatively were reported at 6 and 8 hours instead)
Other bias	Unclear risk	Insufficient information to allow a clear judgement