Gerlach 2003.

Methods	Study design: parallel‐group randomized controlled trial Sample size: 48 Country: Germany Setting: secondary care hospital Dates conducted: not reported Postoperative opioid used and delivery: PCA piritramide Pain score collection: blinded interviewer Concurrent postoperative analgesics: none reported
Participants	Inclusion criteria ASA 1 or 2 undergoing lumbar spinal surgery Exclusion criteria Individuals aged over 60 years Liver disorder or renal disease Known drug or alcohol abuse Current administration of opioid analgesics Known allergies to study drugs
Interventions	Group R5 (16 participants): intravenous remifentanil 0.2 mcg/kg/min administered over a 5‐minute period before induction. After a 15‐minute break, anaesthesia was started with an infusion of 0.25 mcg/kg/min remifentanil followed by a continuous infusion of 0.25 mcg/kg/min until the end of anaesthesia. Group R20 (16 participants): intravenous remifentanil 0.05 mcg/kg/min was administered over a period of 20 minutes before induction and then same regimen as R5. Group RL (15 participants): 10 minutes after skin incision intravenous remifentanil 0.2 mcg/kg/min was administered for 5 minutes followed by an infusion of 0.5 mcg/kg/min for 50 minutes. The infusion was then reduced to 0.25 mcg/kg/min and continued until the end of anaesthesia. All groups had similar total doses of remifentanil.
Outcomes	Postoperative pain (NRS 0 to 15 at 1, 2, 3, 4, 5, 6, and 24 hours) Piritramide consumption (mg, reported at 2, 4, 6, and 24 hours) Adverse events (blood pressure (mmHg), heart rate (beats per minute), sedation (Ramsey sedation scale), intraoperative awareness (yes/no), nausea and vomiting (yes/no) at 1 hourly intervals up to 6 hours and again at 24 hours)
Notes	Funding: departmental funds Declarations of interest: not reported Authors contacted: yes, although no reply Other: postoperative pain converted to a 0‐to‐10 scale. Data extracted from graphs using computer software. R5 and R20 groups combined for main analysis. We contacted authors for further information but received no response.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No details. Quote: "participants were randomly assigned to 1 of 3 study groups"
Allocation concealment (selection bias)	Unclear risk	No mention
Blinding of participants and personnel (performance bias) All outcomes	High risk	No double‐dummy placebo used.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinded. Quote: "the assessment was performed by a single interviewer, who was unaware of the study medication"
Incomplete outcome data (attrition bias) All outcomes	Low risk	1 participant dropped out of postincision group due to protocol violation, which was unlikely to cause bias. Quote: "of the 48 patients enrolled in the study, 1 had to be excluded because the study protocol was violated: the surgery lasted less than 50 minutes, and thus the patient could not receive the complete remifentanil infusion as described for group RL"
Selective reporting (reporting bias)	Unclear risk	No protocol or trial registration
Other bias	Low risk	Longer surgery in postincision group, although this was of little clinical significance. Quote: "there were no significant differences between the groups with respect to demographic data, duration of surgery and anaesthesia and type of surgical procedure"