Table 1

Characteristics of included studies

Reference	Country	Study design	Study setting	Participants	Intervention	Control	Follow-up duration	Primary outcome measure	Secondary outcome measures
Vahidi et al 32	Iran	Double-blind parallel RCT	Emergency department of tertiary referral centre	n=40 (20 intervention, 20 control)	Lidocaine: lidocaine solution (2 mg/kg) intravenous over 5 min	Morphine solution (0.1 mg/kg) intravenous over 5 min	Assessed before, 15 and 30 min after initiation of infusion	VAS (0–10)	None
Morris-Stiff et al 35	Wales, UK	Prospective observational study (pilot study)	Outpatients under vascular surgery team	n=20 (consecutive patients) 17 completed study	Gabapentin: 300 mg daily, titrated to 300 mg three times a day within 3 days Increased to 600 mg three times a day as indicated	None	Assessed at baseline, 4, 7, 14, 28 days or until surgical intervention or death	VAS (0–10)	Night pain score, opioid requirements
Aurilio et al 36	Italy	Open-label randomised trial	Surgical outpatients in a tertiary referral centre	n=86 (44 intervention, 42 control)	Buprenorphine (35 µg/hour) patch+epidural infusion of ropivacaine/morphine (200 mg+2 mg)	Placebo patch+epidural infusion of ropivacaine/morphine (200 mg+2 mg)	4 weeks with twice weekly contact by researcher	VAS (0–100)	Short-Form McGill Pain Questionnaire, sleep quality, morphine requirements, patient satisfaction, psychobehavioural evaluation (Hamilton Scale)
Aurilio et al 28	Italy	Open-label randomised trial	Patients under vascular surgery awaiting surgery	n=43 (22 intervention, 21 control)	Buprenorphine (35 µg/hour) patch+epidural 100 mL of ropivacaine (2 mg/mL) and 2 mg of morphine at 4 mL/hour	Epidural 100 mL of ropivacaine (2 mg/mL) and 2 mg of morphine at 4 mL/hour rate	30-day observation period	VAS (0–100)	Hours of sleep, adjustment of spinal dose of morphine
Mitchell and Fallon33	Scotland, UK	Double-blind placebo controlled RCT	Patients under the care of vascular surgery	n=35 (20 male, 15 female) 7 withdrew so final analysis: 16 intervention, 12 placebo	Ketamine: intravenous ketamine 0.6 mg/kg in 0.9% saline over 4 hours	Intravenous placebo (0.9% saline) over 4 hours	Assessed at entry to study, prior to infusion, 24 hours after infusion and on average 5 days postinfusion	Brief Pain Inventory	Opioid requirements, presence of allodynia/hyperpathia/hyperalgesia
Persson et al 34	Sweden	Crossover, double-blind RCT	All referred from vascular surgery	n=8	Ketamine: racemic ketamine hydrochloride 0.15, 0.3, 0.45 mg/kg intravenous over 5 min	Morphine-hydrochloride 10 mg intravenous over 5 min	VAS scores at 2.5, 5, 10, 20, 30, 40, 50 and 60 min	VAS (0–10)	None

RCT, randomised controlled trial; VAS, visual analogue scale.