Calderon 2004.

Methods	RCT Approved by the ethics committee and informed consent obtained Setting: Spain Funding: unspecified
Participants	30 ASA 2 to 3 patients aged 30 to 75 years, scheduled for abdominal surgery (pancreatico‐duodenectomy or hemicolectomy) Exclusion criteria were cardiovascular disease or disease of the central nervous system, allergy to opioids or non‐steroidal anti‐inflammatory drugs, long‐term use of opioids or psychotropic drugs, history of addiction to drugs or alcohol abuse and contraindications to epidural analgesia
Interventions	Treatment group: lumbar epidural analgesia (L1‐L2 inserted before surgery), bupivacaine 0.25% 15 mL and fentanyl 1 mcg/kg 40 minutes after surgery followed by 1.5 mL/h of bupivacaine 0.25% and fentanyl 1 mcg/h for 24 hours (n = 15) Control group: morphine 0.15 mg/kg and ketorolac 30 mg IV followed by an infusion of tramadol 300 mg/24 h and ketorolac 90 mg/24 h plus morphine as rescue (n = 15) General anaesthesia with propofol, remifentanil, sevoflurane and rocuronium. Prophylaxis with ondansetron
Outcomes	Pain scores (0 to 3) at 6 hours after surgery Vomiting (first 24 hours)
Notes	Study authors contacted on 25 June 2015, sent additional data on 13 July 2015
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
Selective reporting (reporting bias)	Low risk	All results reported
Other bias	Low risk	Groups well balanced