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Three Part Question

In [patients requiring local anaesthetic infiltration] is [warmed local anaesthetic rather than room temperature local anaesthetic] on infiltration [less painful]?

Clinical Scenario

A 40 year old male sustains a 2 cm laceration to his left forearm. There is no tendon/neurovascular damage. Would warmed local anaethetic or room-temperature local anaesthetic be less painful on infiltrating the wound prior to suturing?

Search Strategy

Medline 1966-12/06 using the OVID interface (limited to Humans and English Language).
{[lignocaine.mp. or exp Lidocaine or lidocaine.mp. or exp Lidocaine or bupivacaine.mp. or exp Bupivacaine or prilocaine.mp. or exp Prilocaine or marcaine.mp. or $caine.mp. or exp Anesthetics, Local or exp Anesthesia, Local or local.mp.] AND [warm.mp. or exp Heat or heat.mp. or hot$.mp. or temperature$.mp. or exp Temperature or exp Body Temperature] AND [pain$.mp. or exp Pain or exp Pain Measurement]}

Search Outcome

758 papers found, of which only 11 were relevant.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Jones JS, Plzak C, Wynn BN, Martin S. 1998 USA	40 adult healthy volunteers (18 years and older) – intradermal injections of bupivucaine.	Double-blinded, randomised study	100mm visual analogue score (subjects were instructed to consider pain from needle-stick as the mid-point of the VAS)	Pain from warmed buffered bupivucaine was significantly lower than room temp buffered (p=0.003; 12.1mm difference, 95% CI 6.9-16.4).	Small sample (40) No comment on gender. All adults (no children). Only 0.5mL injected. Atraumatic (no wound). Unclear randomisation method. No control on infiltration rate, and on time-interval between needle-stick and infiltration.
Colaric KB; Overton DT; Moore K. 1998 USA	20 adult healthy volunteers – intradermal injections of lignocaine. Also looked at effect of buffering pH as well as temp. Four solutions were studied: 1. room temp unbuffered 1%lignocaine 2. warmed 37°C unbuffered 3. room temp buffered 4. warmed 37°C buffered	Double-blinded, randomised, prospective trial	200mm visual analogue score (subjects were instructed to consider pain from needle-stick as the mid-point of the VAS)	Mean pain score for warmed and buffered lignocaine was significantly lower than all the other solutions (p<0.0005 for solutions 1 and 2, and p<0.005 for solution 3).	Small sample (20 patients receiving 4 injections in each of 4 different occasions). No comment on age/gender. Only 1mL injected. Atraumatic (no wound).
Fialkov JA, McDougall EP. 1996 Canada	26 adults (16 women, 10 men): 6 patients with two skin lesions for excision, and 20 healthy volunteers (injected into both forearms). Subcutaneous injections of equal volumes (ranging from 3-6mLs at a rate of 0.05mL/sec) of 1% Lignocaine with 1:100,000 epinephrine.	Double-blinded randomised trial.	Verbal scoring (0 to 10) to avoid the variable of using the dominant arm immediately after the injection.	The mean difference in pain score between the room temperature and warmed solutions was +1.5 (p<0.0001).	Small sample (26). All adults (no children). Atraumatic (no wound). Variable volumes of solutions injected (3-6mLs); although volumes were equal in each subject. No control on time-interval between needle-stick and infiltration.
Martin S, Jones JS, Wynn BN. 1996 USA	40 adult healthy volunteers (18 years and older) – subcutaneous injections of lignoacaine.	Double-blinded, randomised study	100mm visual analogue scale + subject's assessment: which is more painful (subjects were instructed to consider pain from needle-stick as the mid-point of the VAS)	20 subjects (50%) reported that 20°C buffered lignocaine was more painful and 17 (42.5%) reported that the 37°C solution was more painful (p=0.74).	Small sample (40) No comment on gender. All adults (no children). Only 1mL injected. Atraumatic (no wound). No control on time-interval between needle-stick and infiltration.
Waldbillig DK, Quinn JV, Stiell IG, Wells GA. 1995 Canada	20 adult healthy volunteers (1st year medical students, 10 males and 10 females, ranging from 21 to 32 years) – digital nerve block of middle finger with lignocaine.	Double-blind, randomised, controlled, crossover trial.	100mm visual analogue scale.	13 felt less pain with warmed, 6 felt less pain with room temp, and 1 perceived no difference.	Small sample (20 x 2) All adults (no children). Atraumatic (no wound).
Bartfield JM, Crisafulli KM, Raccio-Robak N, Salluzzo RF. 1995 USA	Part I: 10 healthy adults received intradermal injections of warmed plain and room-temperature buffered 1% lignocaine. Part II: 24 healthy volunteers received intradermal injections of warmed buffered and room-temperature buffered 1% lignocaine.	Two-part randomised, double-blinded clnical trial.	100mm visual analogue scale.	Part I: Pain scores were significantly higher for warmed as compared to room-temperature buffered lignocaine (28 ±22mm, p<0.01).	Small sample (10 and 24). All adults (no children). No comment on gender. Only 0.5mL injected. Atraumatic (no wound). No comparison between room-temperature plain and warmed plain lignocaine. No control on time-interval between needle-stick and infiltration.
Brogan GX Jr, Giarrusso E, Hollander JE, Cassara G, Maranga MC, Thode HC. 1995 USA	45 patients older than 13 years old (mean 30 +/- 10), 80% men similar wounds in length, depth, and location. Also looked at effect of buffering pH as well as temp. Each wound had two margins/sides. Each margin was injected with a different solution of lignoacine and patients were divided into five groups according to solutions injected and order of injection.	Single-blinded, randomised prospective study.	Visual analogue scale.	Both warmed and buffered lignocaine had significantly less pain on infiltration. Mean pain scores:	Single-blinded. Small sample (45) Mostly men. All adults (no children). Amount of injection not determined (?variable). Injection performed by two different investigators who were not blinded. No mentioning of site, size, or depth of wound (despite mentioning that these were similar in all subjects).
Mader TJ, Playe SJ, Garb JL. 1994 USA	32 adult healthy volunteers (age 21 to 45 years) – subcutaneous injections of lignocaine. Each volunteer had 4 injections with plain, warm, buffered, and warm-buffered.	Double-Blinded, randomised, controlled study.	15cm visual analogue scale.	The mean pain score for warm-buffered lignocaine was significantly lower than plain (p=0.0001), warm (p=0.0005) and buffered (p=0.0028) solutions; suggesting a synergistic effect of warming and buffering.	Small sample (32) All adults (no children). No comment on gender. No clear randomisation of order of injections. Only 0.5mL injected. Atraumatic (no wound). No control on time-interval between needle-stick and infiltration.
Davidson JA, Boom SJ. 1992 UK	40 medical and paramedical staff (healthy volunteers) – subcutaneous injections of lignocaine.	Double-blinded, randomised, crossover study.	100mm visual analogue scale + subject's assessment: which is more painful. Subjects were instructed to exclude pain from needle.	25 (89%, 95% CI 72-98) thought that lignocaine at 20°C was more painful.	Small sample (40) Age 26 to 59 (no children) + mostly men (33 out of 40). Only 1mL injected. Atraumatic (no wound). Unclear randomisation method.
Bainbridge LC. 1991 UK	40 adult patients attending for local anaesthetic procedures on the cheeks and chin (4mls of 1% lignocaine with 1:200,000 adrenaline was used) – subcutaneous injections.	Single-blinded, randomised, controlled study.	15cm visual analogue scale (subjects were instructed to consider pain from needle-stick as the mid-point of the VAS).	Patients perceived significantly less pain (p<0.005) when injected with local anaesthetic at body temperature.	Single-blinded. Small sample (45 injections). No comment on age/gender. Atraumatic (no wound, used for excision of facial lesion). Paired comparison is not possible because patients received only one of the solutions.
Ram D, Hermida LB, Peretz B. 2002 Israel	44 children (age 7.9 ± 2.2 years), 21 girls and 23 boys; were given 1.8mLs of 2% Lignocaine with 1:100,000 epinephrine at a rate of 1mL per minute; on two separate ocasions. The injections were for dental procedures (palatal or mandibular blocks). Topical anaethetic gel (5% Lignocaine) was applied to the site of injection one minute prior to injection.	Single-blinded randomised trial.	Objective using the modified Behavior Pain Scale - BPS (Taddio et al), Wong-Baker FACES Pain Rating Scale - FPS, and 100mm visual analogue scale - VAS.	No statistically significant difference between warmed and room-temperature solutions was found using any of the measurment tools.	Small sample (44). Single-blinded. The use of topical local anaesthetic may obscure any potential difference (especially that VAS scores were 0 in 29 instances). Atraumatic dental procedure.

Comment(s)

Eight papers were double-blinded and three were single-blinded. All were randomised trials. All had small sample sizes ranging from twenty to forty-five patients. Apart from two, all studied healthy volunteers; the two studied infiltration of traumatic wounds, and infiltration of facial lesions prior to excision. Six studied subcutaneous infiltration, three studied intradermal infiltration, one studied dental procedures and one studied digital nerve blocks. All studied lignocaine except one studying bupivacaine. The most relevant paper to wound closure in the Emergency Department was one that studied pain on infiltrating traumatic wounds. It had the largest sample (forty-five patients), and concluded that warming reduced pain on infiltration (p<0.05). It was however single-blinded, and did not determine the exact site or size of the wounds. Five more double-blinded studies (on healthy volunteers) supported the result that warming reduces pain. Two papers showed that warming and buffering have a synergistic effect in reducing infiltration pain. Another paper however concluded that only buffering reduces pain, and that warming a buffered solution does not reduce the pain any further. Only one paper included children. It however looked at pain of local anaesthetic injections in dental procedures, and a topical local anaesthetic was used prior to injections. It concluded that warming did not reduce the pain of infiltration.

Clinical Bottom Line

The overall evidence suggests that warming local anaesthetics, either alone or in combination with buffering, significantly reduces pain of local infiltration. Warming the local anaesthetic using commercially available warmers is a simple, inexpensive, and practical way of reducing the pain of local anaesthetic infiltration in the A&E environment.

References

1. Jones JS, Plzak C, Wynn BN, Martin S. Effect of temperature and pH adjustment of bupivacaine for intradermal anesthesia. American Journal of Emergency Medicine 1998 Mar;16(2):117-20
2. Colaric KB, Overton DT, Moore K. Pain reduction in lidocaine administration through buffering and warming. American Journal of Emergency Medicine 1998 Jul;16(4):353-6
3. Fialkov JA, McDougall EP. Warmed local anesthetic reduces pain of infiltration. Annals of Plastic Surgery 1996 Jan;36(1):11-3
4. Martin S, Jones JS, Wynn BN. Does warming local anesthetic reduce the pain of subcutaneous injection? American Journal of Emergency Medicine 1996 Jan;14(1):10-2
5. Waldbillig DK, Quinn JV, Stiell IG, Wells GA. Randomized double-blind controlled trial comparing room-temperature and heated lidocaine for digital nerve block. Annals of Emergency Medicine 1995 Dec;26(6):677-81
6. Bartfield JM, Crisafulli KM, Raccio-Robak N, Salluzzo RF. The effects of warming and buffering on pain of infiltration of lidocaine. Academic Emergency Medicine 1995 Apr;2(4):254-8
7. Brogan GX Jr, Giarrusso E, Hollander JE, Cassara G, Maranga MC, Thode HC. Comparison of plain, warmed, and buffered lidocaine for anesthesia of traumatic wounds. Annals of Emergency Medicine 1995 Aug;26(2):121-5
8. Mader TJ, Playe SJ, Garb JL. Reducing the pain of local anesthetic infiltration: warming and buffering have a synergistic effect. Annals of Emergency Medicine 1994 Mar;23(3):550-4
9. Davidson JA, Boom SJ. Warming lignocaine to reduce pain associated with injection. BMJ 1992 Sep 12;305(6854):617-8
10. Bainbridge LC. Comparison of room temperature and body temperature local anaesthetic solutions. British Journal of Plastic Surgery 1991 Feb-Mar;44(2):147-8
11. Ram D, Hermida LB, Peretz B. A comparison of warmed and room-temperature anesthetic for local anesthesia in children. Pediatric Dentistry 2002 Jul-Aug;24(4):333-6