Dahi‐Taleghani 2014.

Study characteristics
Methods	Randomised, double‐blind, placebo control
Participants	N = 140, 100% men
Interventions	Postoperative ketamine 2 mg + morphine 2 mg via PCA
Outcomes	Pain intensity (VAS) reported at 1, 6 and 24 h postoperatively. Analgesic consumption reported at 24 h postoperatively. AEs
Surgery type	Elective orthopedic surgery for the lower limb
Group numbers after end of study (treatment/control)	70/70
Age of patient population (treatment/control)	39.1 ± 7.2 38.3 ± 7.5
Notes	The study was supported financially in part by a research grant from the Anesthesiology Research Center, Shadid Beheshti University of Medical Sciences, Tehran, Iran
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated random number table
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method not described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Only mentioned double‐blind
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Only mentioned double‐blind
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals
Selective reporting (reporting bias)	Low risk	All predefined outcomes reported
Size	Unclear risk	70 participants per treatment arm