Koo 2006.

Methods	Double‐blind randomized controlled trial
Participants	Age (years, mean ± SD): Group S = 40.8 ± 11.2, Group L = 41.3 ± 9.9, Group K10 = 40.3 ± 11.3, Group K50 =45 ± 10.5, Group K100 = 39.5 ± 11.7, Group KP 43.4 ± 11.8, Group Pre 37.3 ± 11.8, Group M = 40.4 ± 11.4 Gender (M:F): Group S = 11:19, Group L = 5:25, Group K10 = 13:17, Group K50 = 10:20, Group K100 = 12:18, Group KP = 13:17, Group Pre = 18:12, Group M = 22:8 Inclusion criteria: age 19 years to 59 years old, ASA I‐II, elective surgery Exclusion criteria: patients taking sedatives or analgesics, and those with allergic, neurologic, or cardiovascular disease Recruitment: 240 adult patients randomly assigned (30 in each group) Setting: Korea
Interventions	Pretreatment alone Randomly allocated into eight groups; five groups during the first part of the study and three groups during the second part In Part 1, patients received pretreatment saline 2 ml (Group S) 2% lidocaine 2 ml (40 mg) (Group L) ketamine 10 mcg/kg (Group K10) ketamine 50 mcg/kg (Group K50) ketamine 100 mcg/kg (Group K100), respectively, immediately followed by propofol 2.5 mg/kg In Part 2, ketamine (100 mcg/kg) was administered 3 min before propofol (Group Pre) ketamine (100 mcg/kg) mixed with propofol solution and administered immediately after 2 ml saline (Group KP) ketamine (100 mcg/kg) administered just before injection of propofol in patients premedicated with midazolam (7.5 mg orally) 90 min before arrival in the operating room (Group M)
Outcomes	Pain intensity assessed on 4‐point scale 0 = no pain 1 = mild pain 2 = moderate pain 3 = severe pain associated with grimacing, withdrawal movement of forearm, or both Outcomes reported and used Incidence of high‐intensity pain Incidence of pain Adverse effects Outcomes sought but not reported Patient satisfaction
Notes	Period of the study: dates not reported.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	N/A
Allocation concealment (selection bias)	Unclear risk	N/A
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"All syringes of test solution were prepared by a doctor not involved in induction of anaesthesia and covered so that the investigator who assessed the patient response was unaware of the nature of the solution."
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"An anaesthesiologist blinded to the study group monitored each patient’s pain score at 5 sec intervals. All syringes of test solution were prepared by a doctor not involved in induction of anaesthesia and covered so that the investigator who assessed the patient response was unaware of the nature of the solution."
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals
Selective reporting (reporting bias)	Unclear risk	N/A
Other bias	Low risk	The study appears to be free of other sources of bias