Schulze 1988.

Methods	RCT Approved by the ethics committee and informed consent obtained Setting: Denmark Funding: industry (in part)
Participants	24 patients undergoing elective open cholecystectomy Exclusion criteria were signs of cardiopulmonary, endocrinological, renal hepatic or immunological disease or infection within 1 week
Interventions	Treatment group: thoracic epidural analgesia with plain bupivacaine 0.5% for 24 hours, then 0.25% for another 24 hours (T4‐L1) and epidural morphine 4 mg every 8 hours thereafter for 96 hours plus systemic indomethacin 100 mg every 8 hours for 96 hours (n = 12) Control group: intermittent nicomorphine (10 to 15 mg) and acetaminophen (1 G) on request (n = 12) General anaesthesia for all participants
Outcomes	Pain at rest and on coughing at 6, 24 and 48 hours: "The patients in the opioids group had significantly more pain during the postoperative course (P < 0.001)"
Notes	Data not extractable. Study authors contacted on 3 June 2016. Replied that data are no longer available
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomized"
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	3 participants requiring bile duct exploration were excluded
Selective reporting (reporting bias)	Low risk	All results reported
Other bias	Unclear risk	Groups well balanced Not in intention‐to‐treat