Wiedemann 1991.

Methods	RCT Informed consent obtained Setting: Germany Funding: unspecified
Participants	28 male patients undergoing upper abdominal surgery (mainly proximal vagotomy for duodenal ulcer)
Interventions	Treatment group: thoracic epidural (T7‐T9, inserted the day before surgery through a paramedian approach) with 12 to 14 mL of 0.5% bupivacaine followed by 12 to 14 mL/h of bupivacaine (0.25% for 12 to 18 hours, then 0.125%) started before induction and continued for 48 hours (targeted sensory level T4) (n = 8) Control groups: thoracic epidural morphine 4 to 5 mg 30 minutes before induction and every 12 hours (n = 10) or IM piritramide Neuroleptanaesthesia with etomidate, succinylcholine, fentanyl, droperidol, nitrous oxide and pancuronium
Outcomes	Pain scores at rest at 6, 24 and 48 hours (scale 0 to 4)
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomly assigned", 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 mentioned No failed epidural mentioned but groups unequal (8 vs 10 and 10)
Selective reporting (reporting bias)	Low risk	All results provided
Other bias	Low risk	Groups well balanced