Comparison of music and vapocoolant spray in reducing the pain of venous cannulation in children age 6-12: a randomized clinical trial

This was a randomized clinical trial with a cross-over design. The study aimed to compare the effect of music and vapocoolant spray in the reduction of pain of venous cannulation. Thirty-six children with thalassemia were recruited. In the first blood transfusion, their pain was measured as control and then they were assigned randomly into 2 arms. The primary outcome was the pain experienced during the venous cannulation which was measured using a Visual Analogue Scale. We followed the CONSORT guidelines for reporting randomized controlled trials.

The study samples were selected from children with thalassemia who attended to Thalassemia Center in Bam, Iran for blood transfusion, from October to December 2020. They needed several blood transfusions with at least 2 weeks’ intervals. The inclusion criteria were age 6-12 years, being conscious, the ability to communicate in Persian, and the ability to respond to the visual scale of pain. Exclusion criteria were inability to respond to pain assessment scales, use of pain reliefs before or during the procedure, and not having consent to participate in the study. The minimum sample size was calculated using the following formula \(\mathrm{n}=\frac{2{\left({\mathrm{Z}}_{\left(1-\upalpha /2\right)}+{\mathrm{Z}}_{1-\upbeta}\right)}^2{\upsigma}^2}{{\mathrm{d}}^2}\) and with the following: 1-α/2 = 1.96, 1-β = 1.64, σ = 31.9, and d = 30, and the calculated minimum sample size was 30. With a 20% drop-out rate, 36 children were recruited in the study. The convenience sampling method was used. Children were randomly assigned to one of the two arms, with a blocking design. Six blocks were defined (ABC, ACB, BAC, BCA, CAB, and CBA) and a number between 1 and 6 were assigned to each block. By rolling dice, the sequence of blocks was determined. Children with even numbers were allocated to arm A and Children with odd numbers were allocated to arm B. The first author and the statistician were not present in the patient enrollment and assignment (allocation was concealed), and the corresponding author was not involved in data analysis. Due to the nature of the intervention blinding was not possible. Cannulation was conducted by the same nurse for all subjects and pain measurement was conducted by two members of the research team who were not present at blocking concealment, and analysis.

We used a cross-over design and all samples received both interventions along with a control measurement. The first author explained the purpose of the research and procedures to children and their parents. Parents and children were informed that venous cannulation will be based on the center routine. Also, the pain relief methods would only be applied with their consent. Children and their parents also received a full description of the used pain relief methods and how levels of pain would be measured. After full disclosure to children and their parents about sampling, pain relief methods, and measurement, written informed consent was obtained. For all children, the same size of catheters (22-gauge) made by the same producer was used. All cannulations were conducted by the same trained nurse with the same procedure in the brachial vein. The nurse who conducted the venous cannulation was working in the center and she was not a member of the research team.

Because there was no routine method of pain relief in the center at the time of sampling, the first venous cannulation was conducted without any treatment and its pain was measured as the control. After control measurement study subjects were randomly assigned to two arms that received both interventions with different sequences within 4 weeks. The allocation and intervention processes are presented in Fig. 1. In the recruitment 36 children entered the study and control measurement was conducted for them. In the next transfusion session children in two arms (A and B) received the study intervention. In both arms one child was withdrawn due to the disinterest of parents, then both arms had 17 subjects in the second measurement. Arm (A) lost 2 children and arm (B) lost 1 child in the third session. In the end, 31 children completed all three measurements and their data was analyzed with ANOVA.

Subjects in arm A, received vapocoolant spray and music before the venous cannulation in the second and third blood transfusion, respectively. Subjects in arm B received the opposite sequence. Vapocoolant spray was applied from a 25 cm distance for 5 s and the cannulation was performed instantly [3]. Music intervention was conducted a follows: they listened to the music of choice of children before the cannulation through the headphones. Pieces of music were played for 30 min before the cannulation and the procedure was performed immediately.

The pain was the primary outcome of the study. The pain of venous cannulation was assessed using a Visual Analogue Scale (VAS). VAS is a validated scale whose usefulness in the measurement of the pain of pediatric patients is confirmed. It has one item which is scored from 0 to 6. Higher scores indicate a higher level of pain. The scale has good reliability and it was used in several studies [3]. Two raters separately observed each subject during and after the cannulation. The interrater reliability was high (r = 0.87). The mean of two scores is reported as the score of VAS.

The data was entered into SPSS Version 16. The pain scores were reported as mean ± SD. The Shapiro-Wilk test was used to test for normality of VAS scores (p > 0.05). The change in pain scores was tested by ANOVA and Tukey post-hoc test between three measurements. The level of significance was set at p < 0.05 in all tests.

The main limitation of the current study was the small sample size which may cause lower generalizability of the results. The small sample size was due to the crossover design. With a sample size of 30, we can claim that vapocoolant spray has a significant effect that could reduce the pain by over 30 mm. Music was not as effective as vapocoolant spray. Larger sample size is needed to reject the effectiveness of music on the pain of venous cannulation. Sampling from children with thalassemia also reduces the generalizability to healthy children. Children with thalassemia have the experience of regular venous cannulation before the study which can affect their experience and pain reporting. Another limitation of this study was the lack of blindness. Because of the nature of interventions, blinding was not possible.