Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomly assigned: no details
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias)	High risk	Unlikely
Blinding of outcome assessment (detection bias)	Unclear risk	Not reported
Incomplete outcome data (attrition bias)	Low risk	No failed block reported
Selective reporting (reporting bias)	High risk	Data for mortality provided for both groups. Presence/absence of complications related to the anaesthetic techniques not reported
Other bias	Low risk	Groups said to be well balanced for age, ASA physical status and coexisting diseases