Mallinder 2000.

Methods	RCT Approved by the ethics committee and written informed consent obtained Setting: United Kingdom Funding: industry
Participants	40 ASA 1 to 3 patients scheduled for elective colorectal surgery
Interventions	Treatment group: LEA (L2‐L3 or L3‐L4) with bupivacaine 0.25% during surgery (n = 12) Control group: IV morphine (n = 20) General anaesthesia for all participants
Outcomes	Anastomotic leak Hospital LOS
Notes
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	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	High risk	Technical monitoring difficulties meant that complete data were collected on only 32 participants (12 epidural and 20 morphine).
Selective reporting (reporting bias)	Low risk	All results reported
Other bias	Unclear risk	Trend towards longer operating time (143 (54) vs 130 (45) minutes) and greater blood loss (1045 (753) vs 785 (887) mL) in the morphine group, but this did not reach significance Not in intention‐to‐treat