Lee 2005.

Methods	Single‐centre RCT
Participants	Setting: University of Hong Kong, China Inclusion criteria: patients undergoing open colorectal surgery Exclusion criteria: patients were excluded from the study if they had known allergy to remifentanil or morphine, had abnormal preoperative renal or hepatic function, regularly took analgesics or had consumed any kind of opioid within the past 24 h, had a history of drug or alcohol abuse, were unable to use patient‐controlled analgesia, were less than 18 yr old, or had a body weight that was not within 20% of ideal Participant numbers: 60 randomly assigned; 60 analysed
Interventions	Intervention: patients received isoflurane at an end tidal concentration of 0.5 to 1.5% (according to clinical requirement), delivered with 70% nitrous oxide in oxygen. Control: patients received isoflurane at an end tidal concentration of 0.5 to 1.5% (according to clinical requirement) delivered in an oxygen‐air gas mixture and they also received an intravenous infusion of remifentanil at 0.05 to 0.5 μg/kg/min.
Outcomes	Other outcomes: Postoperative opioid consumption
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was based on computer‐generated codes."
Allocation concealment (selection bias)	Low risk	Opaque envelopes were used.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	This was not reported.
Blinding of outcome assessment (detection bias) Inhospital case fatality rate/length of stay	Unclear risk	—
Blinding of outcome assessment (detection bias) Complications	Low risk	Nurses and acute pain team members who were not involved in the study and were unaware of the patients' intraoperative randomization conducted observation and management in the postanaesthesia care unit and subsequently the ward.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data.
Selective reporting (reporting bias)	Low risk	All outcomes described in methods section reported.
Other bias	Low risk	No other potential sources of bias were detected.