Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Open randomized: no details
Allocation concealment (selection bias)	Unclear risk	Unclear
Blinding of participants and personnel (performance bias)	High risk	Open study
Blinding of outcome assessment (detection bias)	Unclear risk	ST depression verified by a blinded assessor
Incomplete outcome data (attrition bias)	High risk	Failure to proceed to surgery as planned led to withdrawal. Two participants in LEA discontinued because of severe pruritus: One received bupivacaine‐fentanyl and the other IV PCA with meperidine at 30 hours. Naloxone for one participant in each group
Selective reporting (reporting bias)	High risk	Not in intention‐to‐treat (see above). Presence/absence of complications related to the anaesthetic techniques not reported
Other bias	Unclear risk	Higher blood loss (1610 mL vs 1017 mL) and longer surgical time (227 minutes vs 188 minutes) for IVPCA group