Rutberg 1984.

Methods	RCT Approved by the ethics committee and informed consent obtained Setting: Sweden Funding: governmental (plus a contribution from the industry)
Participants	24 female patients undergoing cholecystectomy
Interventions	Treatment group: TEA (T9‐T10 or T10‐T11) with bupivacaine 0.5% before surgery and 0.25% to 0.375%, 5 to 8 mL to maintain segmental blockade from T4 to L3 (n = 8) for 24 hours Control group: epidural morphine 4 mg in 7 mL of saline, repeated every 10 hours (n = 8), and postoperative IV morphine 2.5 mg as required (n = 8) General anaesthesia for all participants
Outcomes	VAS scores at 6 and 24 hours (not clearly mentioned, taken as at rest)
Notes	Study includes a third group referred to as "control" group and not retained for the purpose of this meta‐analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomly allocated", no details
Allocation concealment (selection bias)	Unclear risk	Not mentioned
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	No loss to follow‐up and no epidural failure mentioned
Selective reporting (reporting bias)	Low risk	All results provided
Other bias	Low risk	Groups well balanced