Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomized: no details
Allocation concealment (selection bias)	Unclear risk	Unclear
Blinding of participants and personnel (performance bias)	High risk	Unlikely
Blinding of outcome assessment (detection bias)	Unclear risk	Independent anaesthetist
Incomplete outcome data (attrition bias)	Low risk	Data provided for all participants
Selective reporting (reporting bias)	High risk	One failed epidural kept in intention‐to‐treat. Presence/absence of complications related to the anaesthetic techniques not reported
Other bias	High risk	Groups well balanced for age, ASA physical status and preoperative coexisting diseases except chronic airways disease (five/25 vs 16/25 for control and TEA, respectively).