Xiao 2013.

Methods	RCT, 3 parallel groups
Participants	Number: 120 men (n = 53) and women (n = 67) Country: China Surgery: open abdominal surgery, general anaesthesia, elective Age: 18 to 60 years ASA: I or II Other inclusion criteria: expected duration of surgery > 45 minutes Exclusion criteria: body mass index > 28 kg/m2; metabolic diseases such as diabetes, hyperthyroidism; serious cardiovascular disease; alcohol or illicit drugs; mental illness or epilepsy
Interventions	Dexmedetomidine 1 µg/kg intravenous bolus after induction of anaesthesia plus remifentanil infusion 0.4 µg/kg/min intraoperatively (n = 40) vs Bolus of normal saline at same volume plus remifentanil infusion 0.4 µg/kg/min intraoperatively (n = 40) vs Bolus of normal saline plus remifentanil infusion 0.05 µg/kg/min intraoperatively (n = 40) All participants: Premedication: none reported Anaesthesia and during surgery: propofol 2 mg/kg, remifentanil 2 µg/kg, rocuronium 0.6 mg/kg. Sevoflurane, rocuronium injected every 40 minutes After surgery: intravenous morphine when needed, not further specified
Outcomes	Dose of 'rescue' morphine at 12 and 24 hours PO Postoperative pain measured by VAS at 12 and 24 hours Postoperative sedation measured by RSS at 12 and 24 hours
Notes	This review looked at only 2 of the 3 parallel groups in this study Amounts of intraoperative sevoflurane, remifentanil and phenylephrine did not differ significantly between the 2 groups analysed by this review. Investigators reported significant differences for these 3 drugs when compared with low‐dose remifentanil Study available only in Chinese. Qualitative data extracted by only 1 person, the translator, whereas quantitative data were extracted by the review authors from tables with no need of translation. Study authors contacted in English for additional information of relevance for risk of bias assessment, type of surgery, criteria for 'rescue' analgesia, etc, without luck
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "...random number table was used to generate random sequence..." Comment: probably done
Allocation concealment (selection bias)	Unclear risk	Nothing reported
Blinding of participants and personnel (performance bias) Pain, 'rescue' analgesia, postoperative sedation	Unclear risk	Quote: "this is a double‐blind randomized controlled trial” Comment: nothing else reported, unclear how blinding was done
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	Quote: "this is a double‐blind randomized controlled trial” Comment: nothing else reported, unclear how blinding was done
Blinding of outcome assessment (detection bias) Pain, 'rescue' analgesia, postoperative sedation	Unclear risk	Same as above
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	Quote: "this is a double‐blind randomized controlled trial” Comment: nothing else reported, unclear how blinding was done
Incomplete outcome data (attrition bias) All outcomes	Low risk	No incomplete outcome data
Selective reporting (reporting bias)	Unclear risk	All outcomes described in the Methods section were accounted for in the Results section
Other bias	Unclear risk	Incomplete information to allow a clear judgement

RCT: randomized controlled trial; ASA: American Society of Anesthesiologists Physical Status 1 to 6, where 1 = Healthy person, 2 = Mild systemic disease, 3 = Severe systemic disease, 4 = Severe systemic disease that is a constant threat to life, 5 = A moribund person who is not expected to survive without the operation, 6 = A declared brain‐dead person whose organs are being removed for donor purposes; BIS: bispectral index, a measure of electroencephalography (EEG)‐based depth of anaesthesia; PCA: patient‐controlled analgesia; VAS: visual analogue scale; PO: postoperative; SD: standard deviation; PONV: postoperative nausea and vomiting; PACU: post‐anaesthesia care unit; DEX: dexmedetomidine; RSS: Ramsey Sedation Scale 1 to 6, where 1 = Patient is anxious and agitated or restless or both; 2 = Patient is co‐operative, oriented and tranquil, 3 = Patient responds to commands only, 4 = Patient exhibits brisk response to light glabellar tap or loud auditory stimulus, 5 = Patient exhibits a sluggish response to light glabellar tap or loud auditory stimulus, 6 = Patient exhibits no response. ^aHospira is a manufacturer of dexmedetomidine