Riwar 1991.

Methods	RCT Setting: Switzerland Funding: unspecified
Participants	Average age 66 years; scheduled for open gastrointestinal resection for colorectal carcinoma (n = 33) or diverticulosis (n = 24)
Interventions	Treatment group: lumbar epidural analgesia (L2‐L3), prior induction of anaesthesia and subsequently every 90 to 120 minutes during surgery, bupivacaine 0.25% at 6 to 12 mL/h for 48 hours after surgery (targeted sensory level T4‐T8) (n = 24) Control group: IV infusion of pentazocine 10 mg/h (n = 24) General anaesthesia with nitrous oxide, isoflurane
Outcomes	Time to first flatus Time to first faeces Anastomotic leak
Notes	Study authors contacted 23 June 2015, no reply
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"urn principle"
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
Selective reporting (reporting bias)	Low risk	All results provided
Other bias	Low risk	Groups well balanced