Vapocoolant sprays for cannulation pain

Clinical bottom line
Four trials (741 participants) say that coolant spray works. Another four (529 participants) say it doesn't. We have insufficient information on which to base a solid judgement on sprays themselves, or how they compare with other methods..

Reference

A Moore et al. Minimising intravenous cannulation pain - a cool solution at last? BMJ 200X XX:XXX-XXX.

Systematic review

A brief systematic review of vapocoolant sprays for cannulation pain carried out in November 2008.

Results

Eight randomised trials of coolant sprays with a placebo or no-treatment control give a mixed message (Table 1). Four trials (741 participants) say that coolant spray works. Another four (529 participants) say it doesn't. It isn't easy to explain why sometimes it does, and sometimes it doesn't. As the table demonstrates, success or failure was independent of trial quality, numbers, adults or children, needle size, type of coolant, or placebo or no-treatment control.

Table 1: Randomised trials of vapocoolant sprays for cannulation pain

Reference	Participants	Design	Intervention spray	Control	Main outcome	Result (with SD or 95% CI)	Comment
Significant benefit of vapocoolant over placebo/no treatment
Hijazi et al, 2008	Adult emergency department patients requiring IV cannulation Needle size 18/20 gauge	Randomised, double blind QS=5/5 N=201	Vapocoolant	Mineral water at room temperature	Pain immediately after cannulation, self-reported 100 mm VAS	Cannulation pain: Placebo 36 mm (IQR 19 to 51) Vapocoolant 12 mm (5 to 40) No or mild pain (30 mm): Placebo 33/103 Vapocoolant 59/98	No difference in rate of successful cannulation
Farion et al, 2008	Children aged 6-12 years requiring IV cannulation Needle size 24 gauge	Randomised, double blind, QS=5/5 N=80	Vapocoolant with pentafluoropropane and tetrafluoroethan at room tempterature	Saline spray at room temperature	Pain immediately after cannulation, self-reported by children 100 mm VAS	Mean pain score: Placebo 56 mm Vapocoolant 37 mm No/minimal pain (<40 mm on 100 mm VAS) Placebo 13/40 Vapocoolant 20/40	Vapocoolant had fewer with severe pain >70 mm Successful cannulation on first attempt: Vapocolant 34/40 Placebo 25/40
Robinson et al, 2007	Emergency department patients requiring cannulation Needle size 16-21 gauge	Randomised, open QS=3/5 N=300	Ethyl chloride	No anaesthesia Entonox Intrademal lidocaine	Pain immediately after cannulation, self-reported 100 mm VAS	Mean pain scores: No treatment 20 mm (15 to 25) Ethyl chloride 11 mm (7 to 15) Lignocaine 1 mm (0 to 6 mm) Entonox 13 mm (8 to 18 mm)	Ethyl chloride and lignocaine appeared to reduce those with more severe pain
Selby & Bowles, 1995	Women needing IV cannula for general anaesthetic Needle size 20 gauge	Randomised, open QS=1/5 N=160	Ethyl chloride	No analgesia EMLA cream Intrademal lidocaine	Pain immediately after cannulation, self-reported 100 mm VAS	Mean pain scores: No treatment 24 mm (IQR 12 to 48) Ethyl chloride 4 mm (0 to 21) EMLA 17 mm (6 to 26) Lignocaine 1 mm (0 - 11)	Ethyl chloride and lignocaine better than no treatment, but lignocaine associated with slighly higher number of failed first cannulations
No significant benefit of vapocoolant over placebo/no treatment
Hartstein & Barry, 2008	Adult emergency department patients requiring IV cannulation Needle size 18/22 gauge	Randomised, open QS=3/5 N=92	Coolant	No coolant	Pain immediately after cannulation, self-reported 100 mm VAS	Mean pain scores: Coolant 27 mm (20 to 34) No treatment 28 mm (20 to 36) No or minimal pain (<40 mm): Coolant 30/48 Control 32/45	Distribution of pain scores highly skewed
Costell et al, 2006	Children aged 9-18 years requiring IV cannulation or venepuncture Needle size 22 gauge	Randomised, double blind, QS=5/5 N=127	Ethyl vinyl chloride	Isopropyl alcohol spray No spray	Pain immediately after cannulation, self-reported 100 mm VAS	Ethyl vinyl choloride 34 ± 26 mm Isopropyl alcohol 33 ± 25 mm No treatment 31 ±25 mm	No difference in ease of cannulation or percent of successful first attempts (about 80%)
Ramsook et al, 2001	Children aged 3-18 years requiring IV cannulation Needle size 22 gauge	Randomised, double blind, QS=4/5 N=222	Ethyl chloride	Isporpopyl alcohol spray	Pain immediately after cannulation, self-reported Faces pain scale	No difference for any age group. Median pain scores (0-10 scale) varied between 6/10 for younger to 2 or 3/10 for older children	No difference in success rate
Crecelius et al, 1999	Adults scheduled for dental surgery with IV cannulation Needle size 20/22 gauge	Randomised, open QS=1/5 N=88	Ethyl chloride	Distilled water spray (room temperature)	Pain immediately after cannulation, self-reported 100 mm VAS	Ethyl chloriode 13 ± 18 mm Placebo 18 ± 20 mm	No major differences in any measures of pain or anxiety

In trials of analgesics, the ability to discern analgesic effect usually depends on having enough pain there to measure it. Typically this means pain being of at least moderate intensity (usually at least 30 mm on a 100 mm visual analogue scale). That doesn't help here. With these trials, significance was not determined by whether placebo pain score was above or below 30 mm.

Bigger needles cause more pain, especially those of 16-gauge or bigger in adults. Despite needle size being generally 18-gauge or smaller in the eight trials, significant amounts of moderate or severe pain still occurred with needles smaller than 16-gauge. Cannulation pain scores with placebo ranged from 18% to 56% of maximum on average. A small number of patients with lots of pain drives up average pain scores.

Comment

We have been here before, faced with trials of modest group size, sometimes quite well done, but with results which point in different directions. In his thoughtful explanation about why most published research findings are false, Ioannides calculated that meta-analyses of small inconclusive studies were three times more likely to be false than true. The situation with coolant sprays is not quite that bad, but we have insufficient information on which to base a solid judgement on sprays themselves, or how they compare with other methods.

References

Hijazi R, Taylor D, Richardson J. Topical alkane vapocoolant spray reduces intravenous cannulation pain in emergency department patients: a randomised, double-blind, placebo-controlled trial. BMJ 2008;XX:XXX-XXX.
Farion KJ, Splinter KL, Newhook K, Gaboury I, Splinter WM. The effect of vapocoolant spray on pain due to intravenous cannulation in children: a randomized controlled trial. CMAJ 2008;179:31-6.
Robinson PA, Carr S, Pearson S, Frampton C. Lignocaine is a better analgesic than either ethyl chloride or nitrous oxide for peripheral intravenous cannulation. Emerg Med Australas 2007;19:427-32.
Selby IR, Bowles BJ. Analgesia for venous cannulation: a comparison of EMLA (5 minutes application), lignocaine, ethyl chloride, and nothing. J R Soc Med 1995;88:264-7.
Hartstein BH, Barry JD. Mitigation of pain during intravenous catheter placement using a topical skin coolant in the emergency department. Emerg Med J 2008;25:257-61.
Costello M, Ramundo M, Christopher NC, Powell KR. Ethyl vinyl chloride vapocoolant spray fails to decrease pain associated with intravenous cannulation in children. Clin Pediatr (Phila) 2006;45:628-32.
Ramsook C, Kozinetz CA, Moro-Sutherland D. Efficacy of ethyl chloride as a local anesthetic for venipuncture and intravenous cannula insertion in a pediatric emergency department. Pediatr Emerg Care 2001;17:341-3.
Crecelius C, Rouhfar L, Beirne OR. Venous cannulation and topical ethyl chloride in patients receiving nitrous oxide. Anesth Prog 1999;46:100-3.