Pang 1998.

Methods	Double‐blind randomized controlled trial
Participants	Age (years, mean ± SD): Group A = 45.6 ± 18.0, Group B = 37.5 ± 13.6, Group C = 40.9 ± 13.4, Group D = 49.1 ± 18.6, Group E = 39.6 ± 19.0 Gender (M:F): Group A = 20:15, Group B = 19:16, Group C = 18:17, Group D = 11:24, Group E = 20:15 Inclusion criteria: age 41.5 ± 17.6 years, ASA I‐II, elective surgery Exclusion criteria: patients with communication difficulties Recruitment: 175 adult patients randomly assigned (35 in each group) Setting: Taiwan
Interventions	Pretreatment with venous occlusion Group A received fentanyl 150 mcg, Group B received morphine 4 mg, Group C received meperidine 40 mg, Group D received 2% lidocaine 3 ml (60 mg), and Group E received 3 ml normal saline and served as the control group followed by propofol 100 mg
Outcomes	Pain intensity assessed on 11‐point scale (VAS) with 0 being no pain and 10 being most excruciating pain Outcomes reported and used Incidence of pain Outcomes sought but not reported Incidence of high‐intensity pain Adverse effects Patient satisfaction Outcomes reported but not used Mean and percentile range of pain intensity
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	"The drug was randomly prepared in an unlabeled syringe for pretreatment and handed to the anaesthesiologist who was blind to the identity of the drug."
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	N/A
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