Lipszyc 1991.

Methods	Randomized controlled trial comparing clonidine versus placebo.
Participants	40 people undergoing vascular (carotid artery) surgery. Age: not reported. Sex: not reported. Exclusion criteria: not reported.
Interventions	Clonidine 4 μg/kg orally 90 min before surgery. Placebo was given using matched oral tablets.
Outcomes	Myocardial ischaemia (ST depression > 0.1 mV for > 1 min).
Notes	Published as an abstract. Funding: not discussed. Declaration of interest: not stated.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Not described as randomized trial.
Allocation concealment (selection bias)	High risk	Not discussed.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Authors described study as 'double‐blind.' Reported use of placebo in control arm. No other details reported.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not discussed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All data reported.
Selective reporting (reporting bias)	Low risk	Outcomes reported were concordant with methods.
Other bias	Unclear risk	Study published as abstract and not formally peer reviewed.