Hjortsø 1985b.

Methods	RCT Approved by the ethics committee and informed consent obtained Setting: Denmark Funding: industry
Participants	20 patients undergoing elective major abdominal surgery (bowel or gastric resection and 1 cholecystectomy)
Interventions	Treatment group: epidural anaesthesia with 1.5% etidocaine during surgery and bupivacaine 0.5% bolus for 24 hours after surgery. In addition, extradural morphine 4 mg was administered every 12 hours from 3 to 72 hours after skin incision (n = 10) Control group: systemic morphine (n = 10)
Outcomes	VAS at 24, 48 and 72 hours (average pain experienced during the preceding 24 hours) taken as at rest
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomized into two groups", 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 or epidural failure mentioned
Selective reporting (reporting bias)	Low risk	All results reported
Other bias	Low risk	Groups well balanced