Welch 1998.

Methods	RCT Approved by the institutional review committee and written informed consent obtained Setting: United States of America Funding: unspecified
Participants	59 ASA class 1 or 2 patients undergoing elective major colorectal surgery under general anaesthesia
Interventions	Treatment group: bupivacaine 0.1% and morphine 0.1 mg/mL started in PACU for an unspecified duration (n = 30) Control group: IM morphine/meperidine (n = 29) All participants received general anaesthesia
Outcomes	Time to first faeces (bowel function) Time to first flatus (ileus) Cost
Notes	No catheter‐related complications or episodes of respiratory depression were reported Study authors contacted for additional information on 26 July 2014, but did not reply
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Table of random numbers"
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
Selective reporting (reporting bias)	Low risk	All results provided
Other bias	Unclear risk	No details