Song 2016.

Methods	Study design: randomized controlled trial (2 arms) Study duration: 2006 to 2009 Study setting: hospital, single centre, China
Participants	Adults undergoing elective supratentorial craniotomy (n = 60) Inclusion criteria ASA I to III adults undergoing above surgery Exclusion criteria History of ischaemic heart disease or conduction defects Pulmonary disease Hepatic disease Renal impairment Cognitive defect Long‐tern use of beta blockers, angiotension‐converting enzyme inhibitors, analgesics, sedatives or antidepressants Allergy to study drugs Mean age, range (years) 39 (18 to 60) Numbers allocated to each arm Group intervention (n = 30) Group control (n = 30) Male gender Group intervention: 17/25 (participants analysed) Group control: 15/27 (participants analysed)
Interventions	Technique and timing Intravenous infusion of dexmedetomidine 0.5 mcg/kg/hr for 10 minutes before induction of anaesthesia, then 0.2 to 0.5 mcg/kg/hr until skin closure versus placebo Dosage As above
Outcomes	Not clear from the report, which outcomes were primary and which were secondary Postoperative pain using the NRS – numerical rating scale (measured at 1, 2 ,4, 6, 8, 12 and 24 hours) Sedation – Ramsey Scale – up to 24 hours postoperatively Morphine consumption – up to 23 hours postoperatively Respiratory depression Hypotension Bradycardia
Notes	Funding None
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random number table
Allocation concealment (selection bias)	Low risk	Quote: ''an anaesthesia nurse prepared the syringe according to the computer‐generated random number and was the only person who knew whether the active drug or placebo was administered''.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: ''an anaesthesia nurse prepared the syringe according to the computer‐generated random number and was the only person who knew whether the active drug or placebo was administered''.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not clear if the anaesthesia nurse who prepared the study drugs was involved in assessing outcomes or not
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	3 participants (1 in the intervention group and 2 in the control group) did not receive their allocated treatments as their surgery was cancelled. 5 participants were lost to follow‐up after receiving their allocated treatments as they were not extubated after surgery (4 in the invention group and 1 in the control group). An intention‐to‐treat analysis was not performed.
Selective reporting (reporting bias)	Unclear risk	The lack of clarity regarding outcome priorities makes it difficult to exclude reporting bias.
Other bias	Unclear risk	Small study