Leal 2013.

Study characteristics
Methods	Randomised, double‐blind, placebo control
Participants	N = 40, about 83% women
Interventions	Ketamine 5 µg/kg/min infusion IV until wound closure
Outcomes	Pain intensity (NRS) reported every 30 min up to 4 h, then every 6 h up to 24 h postoperatively. Time to the first analgesic supplementation. Cumulative analgesic consumption reported at 24 h postoperatively. AEs
Surgery type	Laparoscopic cholecystectomy
Group numbers after end of study (treatment/control)	20/20
Age of patient population (treatment/control)	46 ± 12.5 45.5 ± 16.1
Notes	No mention of sponsorship or funding
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomisation achieved by drawing envelopes
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method not described
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinded personnel
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Blinded personnel
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals
Selective reporting (reporting bias)	High risk	AEs are defined and reported in 'results' section, but not predefined in 'methods' section
Size	High risk	20 participants per treatment arm