Nathanson 1996.

Methods	Randomized controlled trial
Participants	Age (years, mean (range)): Lidocaine group (L) = 57 (19 to 75), alfentanil group (A) = 55 (18 to ‐72), placebo group (P) = 53.5 (3 to 74) Gender (M:F): Lidocaine group = 18:12, alfentanil group = 14:15, placebo group = 17:13 Inclusion criteria: age 18 years to 75 years old, elective surgery Exclusion criteria: a history of chronic pain syndromes, thrombophlebitis, neurological disease, and analgesic administration at the time of the study Recruitment: 89 adult patients randomly assigned (30, 29, 30 in group L, A, P respectively) Setting: United Kingdom
Interventions	Admixture Patients were randomly allocated to one of three groups Group L (lidocaine; n = 30) received 2 ml of normal saline followed 30 sec later by premixed propofol 180 mg (18 ml) and lidocaine 40 mg (2 ml of lidocaine 2%) Group A (alfentanil; n = 29) received pretreatment with alfentanil 1 mg followed 30 sec later by propofol and normal saline (propofol 180 mg mixed with 2 ml normal saline) Group P (placebo; n = 30) receive 2 ml normal saline followed 30 sec later by propofol and normal saline (as for Group A)
Outcomes	Pain intensity assessed on 4‐point scale 0 = no pain 1 = mild pain 2 = moderate pain 3 = severe pain Outcomes reported and used Incidence of high‐intensity pain Incidence of pain Outcomes sought but not reported Adverse effects 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	Unclear risk	N/A
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