‘Chilling out’ the pain

October 2016 Vol. 16 (5)

This edition’s Clinically Appraised Topic (CAT) asks whether a cold spray helps to ‘chill out’ the pain of inserting IV cannula.

CLINICAL BOTTOM LINE:

Vapocoolant (cold) spray applied to the skin immediately before intravenous (IV) cannulation may produce a small, but significant, reduction in pain experienced during the procedure. Spraying made no difference to first attempt success rates of IV cannulation and was also not associated with serious adverse effects when compared with placebo or no treatment, but it can cause mild discomfort when first applied.

CLINICAL SCENARIO:

Intravenous (IV) cannulation for blood tests or treatment can be painful. Current pain relief options are not ideal. Topical anaesthetic creams take a long time to work, while injected local anaesthetic can sting and requires another needle. You have heard about using vapocoolant spray (cold spray) to produce rapid-onset anaesthesia on the skin around the cannulation site but wonder if it really helps reduce the pain of IV cannulation and if it is safe. You decide to review the evidence.

QUESTION:

Does vapocoolant spray safely reduce the pain of intravenous cannulation as compared with no treatment or placebo?

SEARCH STRATEGY:

PubMed Clinical Queries (Therapy/Broad): vapocoolants  

CITATION:

Griffith RJ, Jordan V, Herd D, Reed PW, Dalziel SR. Vapocoolants (cold spray) for pain treatment during intravenous cannulation. Cochrane Database of Systematic Reviews 2016, Issue 4. Art.No.: CD009484. DOI: 10.1002/14651858.CD009484.pub2.

STUDY SUMMARY:

A Cochrane systematic review assessing the efficacy of vapocoolants for pain treatment during intravenous cannulation. Inclusion criteria were:

Type of study: Randomised controlled trials comparing a vapocoolant with placebo or no treatment for analgesia associated with IV cannulation in adults or children. Quasi-randomised controlled studies were excluded.

Intervention: Any vapocoolant used for intravenous cannulation.

Comparison: Placebo or no treatment.

Outcomes:

Primary outcome: Pain during IV cannulation.

Secondary outcomes: Pain immediately after IV cannulation; pain at time of application of vapocoolant; first attempt success rate of IV cannulation; adverse events, and participant (or caregiver) satisfaction.

STUDY VALIDITY:

Search strategy: Eligible studies were sought via a comprehensive search strategy involving six electronic databases (CENTRAL , MEDLINE, EMBASE, LILACS, CINAHL, ISI Web of Science up to May 2015), relevant databases for ongoing trials, reference list review of all retrieved articles and hand searching abstracts of the American Society of Anesthesiologists. No date or language restrictions applied.

Review process: At least two reviewers independently examined titles/abstracts and then full text of potentially relevant studies for eligibility. Three authors independently extracted data using a standardised data extraction form, and assessed the quality of included studies. Differences in opinion were resolved by consensus.

Quality assessment: Included studies were assessed for risk of bias using the following criteria: random sequence generation, allocation concealment, blinding of participants, personnel and outcome assessor, incomplete outcome data and selective reporting.

Overall validity: A high-quality review involving randomised controlled trials of low to high risk of bias.    

CAT graphSTUDY RESULTS:

The search identified 1,884 studies after removal of duplicates. After screening titles/abstracts, 17 full text articles were assessed for eligibility, from which seven articles were excluded. The remaining nine RCTs (10 articles) were included in the review; eight RCTs (848 participants) had data suitable for quantitative meta-analysis of the primary outcome. Six studies took place in emergency departments, the other three studies involved patients undergoing planned elective procedures. Participants were adults (six studies), or children (three studies). Placebo spray was used as a comparison in five studies. Vapocoolant spray resulted in a statistically significant reduction in pain score during IV cannulation compared with control, measured using a visual pain score range of 0 to 100mm (0 = no pain and 100mm = worst possible pain).

On average, pain scores were reduced by 12.5mm (see table). Application of vapocoolant (pre-cannulation) was associated with a small increase in pain/discomfort compared with control (see table). There was no significant difference between groups for pain one minute after cannulation (one study), first attempt success rate of cannulation (six studies), adverse events (five studies), or participant/caregiver satisfaction, although patient preference/satisfaction was poorly measured in the included studies. 

COMMENTS:

  • Excluding studies of unclear or of high risk of bias did not change the results for the primary outcome. Heterogeneity was not explained by study quality, participant age (adults vs children), type of vapocoolant, or study setting and most likely reflects the varying results in the small number of trials.    
  • The reduction in pain seen with use of vapocoolant was small but probably clinically significant, at least for some people. As with most treatments, vapocoolants will work better for some than others. Adverse events from vapocoolant were minor and included a cold sensation, transient reactions of erythema at the site of spray and one report of a burning sensation.
  • This review did not compare vapocoolants with other pain relief options, but advantages of vapocoolant spray are its rapid onset, ease of application and no extra needles. 
  • These results suggest that vapocoolant spray may be a useful option to offer patients, especially those not happy with a ‘grin and bear it’ approach to managing procedural pain. 

Reviewer: Cynthia Wensley RN, MHSc. Honorary Professional Teaching Fellow, University of Auckland and PhD Candidate, Deakin University, Melbourne cwensley@deakin.edu.au 

 

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