Lee 2008.

Study characteristics
Methods	Randomised, double‐blind, placebo control
Participants	N = 32, about 55% women
Interventions	Pre‐incisional ketamine 0.15 mg/kg bolus IV
Outcomes	Pain intensity (NRS) reported on arrival to PACU and at 5, 10, 15 and 30 min, then at 5 and 24 h postoperatively. Analgesic consumption (either ketorolac or tramadol) reported as additional count per day
Surgery type	Laparoscopic cholecystectomy
Group numbers after end of study (treatment/control)	16/15
Age of patient population (treatment/control)	40.7 ± 7.8 43.8 ± 10.8
Notes	Article in Korean. No mention of sponsorship or funding
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Study authors do not describe randomisation
Allocation concealment (selection bias)	Unclear risk	Allocation concealment method not described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Blinding not described, only stated "double blind" in the title
Blinding of outcome assessment (detection bias) All outcomes	Low risk	A blinded investigator assessed postoperative pain scores
Incomplete outcome data (attrition bias) All outcomes	Low risk	3% was withdrawn
Selective reporting (reporting bias)	Unclear risk	The study protocol was not available
Size	High risk	16 and 15 participants per treatment arm