Zeng 2003.

Methods	RCT Setting: China Funding: departmental resources
Participants	42 ASA 1 to 2 patients, aged 37 to 70 years, with no preoperative immune or endocrine disease and scheduled for elective abdominal surgery of an expected duration < 4 hours
Interventions	Treatment groups: TEA or LEA (according to surgical site) inserted before induction and tested with 4 mL of lidocaine 2%, bupivacaine 0.33% 4 to 6 mL during surgery followed by ropivacaine 0.2% and fentanyl 2 mcg/mL as patient‐controlled analgesia (background infusion 4 mL/h; bolus 2 mL; lockout time 20 minutes) (n = 9) or bupivacaine 0.12% plus fentanyl 2 mcg/mL (same settings) (n = 8) or bupivacaine 0.12% plus morphine 0.08 mg/mL (same settings) (n = 9) for 24 hours Control group: IV morphine (n = 8) General anaesthesia with propofol, fentanyl, nitrous oxide, isoflurane and vecuronium
Outcomes	Pain scores at 24 hours after surgery (taken as at rest)
Notes	Study includes a fourth treatment group, with intraoperative bupivacaine followed by IV morphine after surgery. This group was not retained in the analysis. Owing to the small number of participants in the control group (n = 8), the 3 treatment groups were fused for analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomly divided", 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 provided
Other bias	Low risk	Groups well balanced