O'Hara 1997.

Methods	Double‐blind randomized controlled trial
Participants	Age (years, mean ± SD): Placebo group = 44.0 ± 13.4, Lidocaine group = 40.0 ± 12.5, NTG group = 37.9 ± 16.2, NTG+Lidocaine group = 46.4 ± 15.6 Gender (M:F): Placebo group = 11:20, Lidocaine group = 14:17, NTG group = 22:9, NTG + lidocaine group = 13:18 Inclusion criteria: ASA I‐III, elective ambulatory surgery Exclusion criteria: N/A Recruitment: 124 adult patients randomly assigned (31 in each group) Setting: USA
Interventions	Admixture Nitroglycerin or placebo ointments were applied to the back of the hand over the skin area overlying the IV catheter tip. Lidocaine was or was not added to the propofol solution: placebo ointment and plain propofol placebo ointment and propofol premixed with 1% lidocaine 2 ml nitroglycerin ointment 7.5 mg and plain propofol nitroglycerin ointment 7.5 mg and propofol premixed with 1% lidocaine 2 ml
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