Aygun 2004.

Methods	RCT Approved by the ethics committee and informed consent obtained Setting: Turkey Funding: unspecified
Participants	80 ASA 1 and 2 patients aged 18 to 60 years undergoing elective lower abdominal surgery
Interventions	Treatment group: LEA (catheter inserted 3 to 4 cm) with ropivacaine 0.125% plus fentanyl 2 mcg/mL for 24 hours (Gr 4; n = 20) Control groups: IV tramadol for 24 hours (Gr 1; n = 20) General anaesthesia for all participants
Outcomes	VAS at 6 and 24 hours (unclear, therefore taken as at rest). A value of 0.001 has been entered as SD when the SD was reported as 0
Notes	Study also includes 2 groups that were not retained: 1 group with epidurally injected tramadol and 1 group with IV fentanyl infusion
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"randomly allocated", 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	High risk	See above
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