AbuRahma 2010.

Study characteristics
Methods	Method of randomisation: unknown Concealment: sealed envelopes that were opened just before surgery Blinding: not reported Cross‐overs: none (ITT analysis) Exclusions during trial: none Loss to follow‐up: none
Participants	USA 200 participants, 200 operations Routine shunting: 98 operations Selective shunting: 102 operations Age: 45 to 89 years, mean 68 years Gender: 48% male, 52% female Comparability: age, gender, vascular risk factors similar between 2 groups More asymptomatic ipsilateral arteries in routine shunting group: 58% versus 53% Contralateral artery stenosis (mean %) routine shunting group: 38%; selective shunting group: 40%
Interventions	Treatment: selective shunting group; shunt selected if systolic stump pressure < 40 mmHg Control: routine shunting group All operations under general anaesthetic; unknown patching rate
Outcomes	TIA, stroke, combined stroke/TIA, death, bleeding, myocardial infarction, congestive heart failure, asymptomatic carotid thrombosis, recurrent laryngeal injury, all complications, number of shunted arteries
Notes	Exclusion: none Follow‐up: 30 days
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "200 CEA patients were randomised into" However, the randomised method was unknown.
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was done using sealed envelopes that were open just before surgery".
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up in either group
Selective reporting (reporting bias)	Unclear risk	Study authors did not report prespecified outcome.
Other bias	Low risk	No other potential biases