ORIGINAL ARTICLE

An Integration of Vibration and Cold Relieves Venipuncture Pain in a Pediatric Emergency Department Amy L. Baxter, MD,*Þ Lindsey L. Cohen, PhD,þ Heather L. McElvery, RN,§ Mona Louise Lawson, PhD,|| and Carl L. von Baeyer, PhD¶

Objective: A randomized controlled trial compared a reusable device combining cold and vibration to standard care for pediatric venous access pain relief. Methods: Pediatric emergency department patients received either the cold vibration device placed 5 to 10 cm proximally throughout venipuncture or standard care control (primarily vapocoolant spray). Block randomization of patients with or without lidocaine cream already in place ensured equal allocation in both intervention groups. Pain was measured via self- and parent-report using the 0- to 10-point Faces Pain ScaleYRevised and with coded videotaped observed behaviors. Venipuncture success, use of distraction, and access times were also assessed. Results: Eighty-one 4- to 18-year-olds were randomized to the device (n = 41) or standard care (n = 40) (median age, 10.09 years; 95% confidence interval [95% CI], 8.91Y10.89). Median patient-reported pain scores with the device were lower than with standard care (j2; 95% CI, j4 to 0), as were parent-assessed pain scores (j2; 95% CI, j4 to j2). Observed distress behaviors were more common with standard care (2; 95% CI, 1Y3) than with the device (1; 95% CI, 0Y2). Venipuncture success was more likely with the device (odds ratio, 3.05; 95% CI, 1.03Y9.02). There were no device refusals. Conclusions: The combination of cold and vibration decreased venipuncture pain significantly more than standard care without compromising procedural success. A device incorporating these elements could overcome the common barriers to needle procedure pain control.

bing, or vibration near the site10; or parent coaching and distraction.2,11,12 Although there are data to support each of these individual treatments, there is no single integrated intervention to optimize pain relief. Furthermore, most current options require excessive time, cost, or staff training, which are formidable barriers to practice change,2,13 especially in busy medical settings such as the emergency department (ED).14 An easy-touse, inexpensive, rapidly effective intervention could enhance procedural pain control in EDs and other fast-paced medical environments. The purpose of this study was to compare standard pediatric ED venipuncture pain control practices to a prototype of a novel battery-powered device, Buzzy (MMJ Labs, Atlanta, Ga), combining cold, vibration, and distraction. A prior study with adult volunteers receiving venipuncture provides initial support for the effectiveness of the combination of cold and vibration,15 but a pediatric device has not been evaluated. We hypothesized that the device would provide greater pain relief than standard fast-acting interventions by children’s self-report. Our secondary aims were to evaluate parent-report and observational measures of pain for additional evidence of the effectiveness of the device and to evaluate venipuncture success.

METHODS

Key Words: venipuncture, needle pain, vibration, vapocoolant, pain

Study Design

(Pediatr Emer Care 2011;27: 1151Y1156)

This single-center, prospective randomized clinical trial was approved by the appropriate institutional review board. The trial was designed in accord with, and adheres to, the guidelines detailed in the CONSORT (Consolidated Standards of Reporting Trials) statement. Informed written consent including the primary investigator’s conflict of interest was obtained from parents; written assent was obtained for patients older than 7 years.

V

enipuncture is a frequent and significant source of children’s medical pain,1,2 reflected in consistent recommendations to provide pain relief ‘‘whenever possible.’’3 Current methods to decrease children’s needle pain include topical anesthetic creams4Y7; vapocoolant cold spray8,9; pinching, rub-

From the *Pediatric Emergency Medicine Associates; †Medical College of Georgia; ‡Department of Psychology, Georgia State University; and §Children’s Healthcare of Atlanta, Atlanta; ||Department of Mathematics and Statistics, Kennesaw State University, Kennesaw, GA; and ¶University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Disclosure: Dr Baxter invented the device and started MMJ Labs to develop and manufacture the device. This conflict of interest was disclosed to participants in the informed consent. After orientation of enrollers employed by the hospital, Dr Baxter was not present for data collection. Dr Cohen, who has no financial conflict of interest to disclose, recruited trained coders for videotape review and performed the data analysis for the study. Reprints: Amy L. Baxter, MD, Pediatric Emergency Medicine Associates LLC, PO Box 422002, Atlanta, GA 30342 (e-mail: Amy_Baxter@ PEMA-LLC.com). Funding for this study was provided to Georgia State University by the Mayday Fund, a private foundation dedicated to alleviating the incidence, degree, and consequence of human physical pain. Clinical Trials No. NCT00919100. Copyright * 2011 by Lippincott Williams & Wilkins ISSN: 0749-5161

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Setting and Participants The study was conducted at a freestanding urban/suburban ED with an annual census of 80,000 between April 1 and August 15, 2008. A convenience sample of pediatric patients requiring venous access was referred by the treating physician during hours when an ED study enroller was scheduled. Inclusion criteria were 4- to 18-year-old patients requiring blood tests or venous access. Potential participants were excluded if they did not speak English and a translator was unavailable, if there was an abrasion or break in skin where the device would be placed, if there was previous nerve damage in the affected extremity, if they were critically ill, or if they had Raynaud or sickle cell disease involving sensitivity to cold. Standing orders in the institution allow for triage nurses to place a topical anesthetic cream of 4% liposomal lidocaine (LMX4; Ferndale Labs, Ferndale, Mich) when a patient is assessed to have a 50% likelihood of requiring venipuncture. As the topical anesthetic cream can come off, can be placed by the triage nurse on an area not chosen for access by the procedure nurse, or can be placed for an inadequate or excessive amount www.pec-online.com

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of time, vapocoolant spray (PainEase; Gebauer, Cleveland, Ohio) is available at the discretion of the cannulating nurse. Vapocoolant is a compressed gas administered by caregivers for 4 to 10 seconds at a distance of approximately 12 cm that numbs by lowering skin temperatures on contact. Vapocoolant spray has been demonstrated to provide effective venipuncture pain relief for patients 6 years or older,9 although standard care at this institution is optional use for all ages. Because topical anesthetic placement occurred in triage before the clinical decision for venipuncture was made by a physician and randomization to standard care, or the device was stratified for liposomal lidocaine placement. A random-number table was used in blocks of 10 for patients with and without anesthetic cream to ensure equal representation across intervention groups. Enrollers unaware of topical anesthetic status brought ‘‘cream’’ and ‘‘no-cream’’ participant packets with group assignment concealed in opaque envelopes to the room, and sequential patient number assignment was made on the appropriate packet after informed consent. Before randomization, the enroller used a standard script to explain the pain and anxiety measures. After verbal understanding was expressed, the enroller obtained background information and assessed child and parent anxiety. At this point, subjects opened the envelope to be randomized to the device or standard care. The device is a reusable 8  5  2.5-cm handheld plastic bee containing a battery-operated vibrating motor and a mechanism to attach an ice pack underneath. It can be pressed in place or secured to a limb via a Velcro strap or tourniquet (Fig. 1). If randomized to the device, the study enroller offered the parent and child the opportunity to hold the device, turn on vibration, and practice application, with total training time limited to 3 minutes. Immediately before the first venous access attempt, the nurse or enroller attached the ice pack under the device, applied the device with a strap at the location of the tourniquet, and switched on the vibration. Nurses were then allowed to cannulate as they normally would, provided the device remained in place and vibrating throughout the attempt. Removal or turning off the device constituted an adverse event. For the standard care group, nurses were given no direction other than to use their normal practice, which might include vapocoolant or distraction at their discretion.

FIGURE 1. Location of device in relation to venipuncture. Arrow indicates site of venipuncture. Silver ice pack can be seen under the device; the motor is in the pedestal closest to the venipuncture site, the switch on the opposite end under ‘‘antennae.’’ The device may be attached with tourniquet directly or with Velcro strap placement above the tourniquet (as was used for this trial).

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The enroller videotaped the venipuncture while attempting to exclude the procedure site, assessed the success of the venous access attempt (defined as blood retrieval or cannulation achieved on the first needlestick), recorded the time required for the first venous access attempt, noted whether vapocoolant was used, and documented any distraction attempts in both groups (eg, adult telling stories or singing or the child watching television).

Measures Demographics (ie, race and mother’s age and highest grade completed) were collected via a self-report form. Triage acuity, age, weight, and chief complaint were obtained from information recorded at ED triage. Preprocedural anxiety was assessed using the anxiety scale from the Children’s Anxiety and Pain Scale (CAPS).16 The CAPS contains 2 sets of 5 drawings of children’s faces exhibiting increasing levels of anxiety and pain. The 1- to 5-point scale has been used in pediatric pain research and practice and has good psychometrics.17 The primary outcome was the child’s self-report of pain with the first venipuncture attempt using the Faces Pain ScaleY Revised (FPS-R).18 The FPS-R is a 0- to 10-point scale consisting of 6 cartoon faces that range from a neutral expression (0, ‘‘no pain’’) to a screaming face (10, ‘‘severe pain’’). The FPS-R has been validated down to age 4 years, is cited in more than 140 studies, and is deemed by reviewers as a ‘‘wellestablished measure.’’19 Parents blinded to the child’s response also rated their child’s pain using the FPS-R after the first venipuncture attempt. A secondary outcome was a count of distress behaviors observed on videotapes using codes from the Observational Scale of Behavioral Distress (OSBD).20 The OSBD is a validated and commonly used scale and has been described as a ‘‘wellestablished measure’’ of pediatric pain.17 Typically, the 11 OSBD distress responses (information seeking, cry, scream, physical restraint, verbal resistance, seeking emotional support, verbal pain, flail, verbal fear, muscular rigidity, and nervous behavior) are coded in 15-second intervals before, during, and after longer procedures to control for baseline anxiety and habituation. Other studies evaluating brief procedures such as needle pain distress have assigned a composite 1- to 11-point score.21 As baseline anxiety in our study was assessed using the CAPS and only the first attempt was evaluated, a composite OSBD score of 1 to 11 was assigned from the time of placement of tourniquet to placement of the bandage or securing the intravenous line (IV) after the first attempt. Two students not associated with the hospital or the device had been previously trained in this methodology and coded all tapes. A supervisor assessed interrater reliability on each coded behavior. After each group of 10 subjects, interrater agreements that fell below the level of excellent agreement (J = 0.80) were reviewed and discussed by both coders, with the consensus score recorded and definitions of observed behaviors refined. Both coders were blinded to study aims and hypotheses; the coders and the supervisor were not involved in other aspects of the study and had no conflict of interest. As coders could hear the sound of the device on the tapes, blinding attempts by obscuring the procedure site were not effective, and the observational ratings should not be considered blinded.

Data Analysis A previous immunization pain study in children aged 4 to 6 years found FPS-R ratings of 4.21 (SD, 1.14) versus 3.08 (SD, 1.35) when using cold spray and distraction versus EMLA21; * 2011 Lippincott Williams & Wilkins

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thus, we calculated that 33 patients in each group would detect a difference with a power of 0.95 and > of 0.05 (G*Power 3.11; Faul, Universitat Kiel, Kiel, Germany).22 Anticipating possible videotape problems and given our wider age range, we planned to enroll 40 patients in each group. Group assignment was analyzed by intention-to-treat. Categorical values are presented as the percentage of frequency with W2 comparisons or Fisher exact test when appropriate. Tests of normality indicated that both pain and anxiety were nonYnormally distributed; thus, group comparisons were conducted using the Mann-Whitney-Wilcoxon test for these results. Student t tests were used to compare normally distributed means for the demographic information.

RESULTS Preliminary Analyses Ninety-four patients were evaluated, one was ineligible because of sickle cell disease status, and 12 declined participation (Fig. 2). The final sample consisted of 81 patients aged 4 to 18 years (mean, 9.97 [SD, 3.83] years) receiving venous access. Additional demographic data are presented in Table 1. Treatment groups did not differ by sex, age, child or parent preprocedure anxiety, IV time for successful attempts or overall mean time, type of procedure, or number of patients who

Vibration and Cold Relieve Venipuncture Pain

received lidocaine cream (Table 1). Blood draws were slightly more common in the Buzzy group (6/41 vs 2/40, P = 0.26); however, there were no differences in pain or distress between cannulation and blood draw on self-report (median difference, 1; P = 0.286), parent proxy report (median difference, 0; P = 0.608), or OSBD (median difference, 0; P = 0.774). There were no adverse events (refusals of the study device) after enrollment. LMX was used for 20 (50%) of 40 standard care patients and 19 (46%) of 41 Buzzy patients. Nine of the 22 patients in the device group who did not have anesthetic cream also received vapocoolant. Of the 20 patients in the standard care group without lidocaine, all received vapocoolant except for 2 who refused the cold spray.

Primary Analyses Consistent with hypotheses, children in the device group had significantly lower pain or distress based on self-report (Table 2). As younger children often report greater pain with procedures,23 separate regression models were used to test the interaction of intervention and age on self-reported pain. Age and treatment group were entered in the first step of the regression model. At the second level, the age  condition interaction term was entered. Age and condition accounted for 14% of the variance in children’s venipuncture pain (P = 0.004). Age was a significant predictor of self-reported pain, A = j0.26,

FIGURE 2. CONSORT diagram showing the flow of participants. * 2011 Lippincott Williams & Wilkins

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TABLE 1. Continuous and Categorical Demographic and Cannulation-Related Variables by Treatment Group Treatment Group Standard Care (n = 40)

Device (n = 41)

Child age, median (95% CI) 9.91 (6.68Y11.08) 10.10 (8.91Y11.99) Child sex, % male 45 58.5 Race, % White 67.5 58.5 Black 12.5 12.2 Asian 0 2.4 Hispanic or Latino 10 22 Other 10 4.9 Mother’s age, mean (SD) 39.6 (4.85) 39.15 (6.38) Mother’s highest 4.62 (1.18) 4.28 (1.38) education, mean (SD) Child preprocedure 3 (2Y4) 2 (2Y3) anxiety, median (95% CI) Parent preprocedure 3 (3Y4) 3 (2Y4) anxiety, median (95% CI) LMX4, % used 50 46.3 Site of venous access, % Hand 60 63.4 Antecubital fossa 35 31.7 Forearm 5 2.4 Other 0 2.4 Type of venous access, (n/n) % Cannulation (38/40) 95 (35/41) 85.4 Blood draw (2/40) 5 (6/41) 14.6 CI indicates confidence interval.

P = 0.018, with younger children reporting more pain. Treatment condition predicted self-reported pain, A = 0.23, P = 0.034, but age  condition interaction did not account for a significant amount of unique variance in pain (G1%), suggesting that age does not moderate the effects of Buzzy on pain. The effects of age and condition are illustrated in Figure 3.

FIGURE 3. Mean self-report of pain intensity as a function of condition (standard care control vs Buzzy) and age (4Y9 vs 10Y17 years), showing 95% confidence intervals and cell n. One control patient (aged 6 years; caregiver pain rating, 8) did not record a pain rating.

Secondary Analyses Children in the device group had significantly lower pain by parent report and the observational scale than children in the standard care group (Table 2). The odds of success with blood retrieval or cannulation on the first attempt were 3 times more likely in the device group than in the standard care group (Table 2). In the standard care group, 21 of 40 patients had attempted distraction by parents, watching TV, and/or by a health care worker; 2 wanted to watch the IV being placed. In the device group, 29 of 41 patients had attempted distraction. There was no difference in self-reported pain for the device group or the overall sample between those who had distraction offered and those who did not.

DISCUSSION The purpose of this study was to evaluate a multifaceted intervention incorporating cold, vibration, and distraction for children’s procedural pain. Results suggested that the vibration

TABLE 2. Median Pain and Distress Differences and 95% Confidence Intervals of Dependent Variables by Treatment Group Treatment Group More than 1 venous access attempt, % Minutes to IV access, mean (SD) In successful attempts Overall time

Standard Care (n = 40)

Device (n = 41)

Odds Ratio (95% CI)

P

35

15

3.05 (1.03Y9.02)

0.040

3.57 (2.45) 7.33 (11.42)

3.12 (2.17) 5.43 (6.93)

0.44 0.37 Difference of Medians (95% CI)

Self-reported pain (FPS-R) Parent-reported child pain (FPS-R) OSBD

4 (2Y6)* 4 (2Y6)† 2 (1Y3)

2 (2Y2) 2 (0Y4)‡ 1 (0Y2)

j2 (j4 to 0) j2 (j4 to j2) j1 (j2 to 0)

0.029 0.005 0.036

Faces Pain ScaleYRevised was scored from 0 to 10; the OSBD for our study was scored from 1 to 11. *Missing 1: parent reported ‘‘8’’; enroller documented child was ‘‘too lethargic’’ and would not circle or indicate face. † Missing 2: one parent stepped out of room for procedure; one was asleep. ‡ Missing 2: one parent stepped out of room for procedure; one was on cell phone. CI indicates confidence interval.

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and cold aspects of the device effectively decreased pain compared with standard care and did not impact IV success. Potential negative repercussions of untreated pediatric needle pain include heightened distress at subsequent procedures,2 avoidance of medical care,24,25 missed vaccinations,6,26,27 and not engaging in blood donation as an adult.28Y30 Needle pain relief might address the issues of needle anxiety, facilitate the medical procedure,31 and heighten patient satisfaction.32 It is critical, however, that pain relief treatment be not only effective, but also sufficiently practical to be used in busy medical settings.2 The best studied interventions for venipuncture pain are topical anesthetics.33,34 Although relief from creams such as EMLA, LMX-4, and Ametop is well established,35 the extra step of applying the cream and the 30 to 60 minutes required for efficacy may slow ED flow. In addition, if the cream comes off or is inappropriately placed, the US $4 to $8 hospital cost per application is wasted. Cold and vibration are quick-acting options for pain relief. The Gate Control Theory36 suggests that pain is transmitted from the peripheral nervous system to the central nervous system where it is modulated by a gating system in the dorsal horn of the spinal cord. More specifically, the afferent pain-receptive nerves (A-delta fibers carrying acute pain and unmyelinated slower C fibers carrying chronic pain messages) are blocked by fast nonnoxious motion nerves (A-beta).37 Prolonged cold stimulates the C fibers and, if preceding the pain, may further block the A-delta pain signal. Another mechanism by which the cold sensation is effective is by triggering descending (or diffuse) noxious inhibitory controls, activating a supraspinal modulation raising the body’s overall pain threshold.38 Although cold spray likely functions via these mechanisms, the brevity of the cold sensation may not maximize C fiber summation blockade effects. The 15- to 30-second duration of contact for the device during cleaning and preparation for venipuncture may enhance C fiber summation and descending (or diffuse) noxious inhibitory control pain relief. The only widely used product that addresses venipuncture pain relief in seconds is vapocoolant spray. Vapocoolant spray is inexpensive at approximately US $0.50 per use, with greater efficacy in older populations more similar to the age distribution in our study. Farion et al9 found a 19-mm/100-mm reduction in pain on a colored visual analog scale for subjects with a mean age of 9.4 years, whereas Davies and Molloy39 reported similar pain relief using ethyl chloride or topical anesthetics for venipuncture in children 5 to 13 years old. In contrast, however, Costello et al40 found no improvement in pain between ethyl chloride spray, placebo, and nothing for children between 9 and 18 years. Ramsook et al8 found no difference in younger children and equivalent efficacy to placebo for children aged 6 to 12 years, with a nonsignificant improvement in children older than 12 years. Despite the modest pain relief, the combination of speed and low cost make this a popular option in ED pain relief. The device costs US $39.95 and comes with replaceable batteries and a reusable ice pack. One unit will vibrate strongly for at least 20 hours, yielding approximately 380 needle attempts per unit, or $0.09 per attempt. Subsequent costs depend on the variable price of batteries, and whether reusable or disposable ice wings (US $0.30) are used. The added step of obtaining a frozen pack may be a barrier to use; this study did not assess the effectiveness of the device by the nursing staff, or its ease of use. There were 3 significant limitations in the current investigation. First, as the device could be seen and heard on the videotapes and by the patients, subjects and coders could not be * 2011 Lippincott Williams & Wilkins

Vibration and Cold Relieve Venipuncture Pain

blinded to intervention groups. Although coders were not privy to hypotheses, they might have developed biases that influenced coding. Likewise, placebo effects of the device were not controlled using a sham device and may have contributed to the results for both patient and parent self-report. Second, despite randomization, the groups may have had small differences in type of procedure (blood draw or IV start), sex, and initial anxiety, which cumulatively could have biased results in favor of the device. As randomization occurred after subject enrollment and rating of preprocedural anxiety, systematic selection bias should have been prevented, but with small sample sizes, minor random differences can be important. A third limitation was the lack of consistency in intervention. The primary investigators were not present for data collection and instructed the enrollers only to record while nurses cannulated ‘‘as they normally do.’’ For this reason, although the intent of the design assumed nurses would use Buzzy only in the study condition, it was not clear until data collection was complete that some nurses also introduced vapocoolant in the device arm. Although vapocoolant was used in 9 of 41 device patients, this should have biased results toward the null hypothesis. In summary, a vibrating cold device containing many of the optimal components to overcome barriers to pain treatment6 proved to be an effective pediatric pain management intervention. The technology of vibration and cold is inexpensive and reusable, requires little extra time, can be implemented by the patient rather than medical staff, and may be beneficial for patients across a range of ages. Venous access is a shallow procedure, and additional research is necessary to determine whether the device might be provide pain relief for intramuscular injection, fingersticks, port access, or other more invasive procedures. Additional studies are warranted to replicate these findings, evaluate the extent of its efficacy, and explore use with other painful procedures, but these findings are promising for this new pediatric pain management tool. REFERENCES 1. Cummings EA, Reid GJ, Finley GA, et al. Prevalence and source of pain in pediatric inpatients. Pain. 1996;68(1):25Y31. 2. Leahy S, Kennedy RM, Hesselgrave J, et al. On the front lines: lessons learned in implementing multidisciplinary peripheral venous access pain-management programs in pediatric hospitals. Pediatrics. 2008;122(suppl 3):S161YS170. 3. American Academy of Pediatrics. Committee on Psychosocial Aspects of Child and Family Health; Task Force on Pain in Infants, Children, and Adolescents. The assessment and management of acute pain in infants, children, and adolescents. Pediatrics. 2001;108(3):793Y797. 4. Eichenfield LF, Funk A, Fallon-Friedlander S, et al. A clinical study to evaluate the efficacy of ELA-Max (4% liposomal lidocaine) as compared with eutectic mixture of local anesthetics cream for pain reduction of venipuncture in children. Pediatrics. 2002;109(6):1093Y1099. 5. Luhmann J, Hurt S, Shootman M, et al. A comparison of buffered lidocaine versus ELA-Max before peripheral intravenous catheter insertions in children. Pediatrics. 2004;113(3 pt 1):e217Ye220. 6. Schechter NL, Zempsky WT, Cohen LL, et al. Pain reduction during pediatric immunizations: evidence-based review and recommendations. Pediatrics. 2007;119(5):e1184Ye1198. 7. Curry SE, Finkel JC. Use of the Synera patch for local anesthesia before vascular access procedures: a randomized, double-blind, placebo-controlled study. Pain Med. 2007;8(6):497Y502. 8. Ramsook C, Kozinetz CA, Moro-Sutherland D. Efficacy of ethyl

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chloride as a local anesthetic for venipuncture and intravenous cannula insertion in a pediatric emergency department. Pediatr Emerg Care. 2001;17(5):341Y343. 9. Farion KJ, Splinter KL, Newhook K, et al. The effect of vapocoolant spray on pain due to intravenous cannulation in children: a randomized controlled trial. CMAJ. 2008;179(1):31Y36.

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24. Vika M, Raadal M, Skaret E, et al. Dental and medical injections: prevalence of self-reported problems among 18-yr-old subjects in Norway. Eur J Oral Sci. 2006;114(2):122Y127. 25. Barr RG, Young SN, Wright JH, et al. ‘‘Sucrose analgesia’’ and diphtheria-tetanus-pertussis immunizations at 2 and 4 months. J Dev Behav Pediatr. 1995;16(4):220Y225.

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13. Fein JA, Gorelick MH. The decision to use topical anesthetic for intravenous insertion in the pediatric emergency department. Acad Emerg Med. 2006;13(3):264Y268. 14. MacLean S, Obispo J, Young KD. The gap between pediatric emergency department procedural pain management treatments available and actual practice. Pediatr Emerg Care. 2007;23(2):87Y93. 15. Baxter AL, Leong T, Mathew B. External thermomechanical stimulation versus vapocoolant for adult venipuncture pain: pilot data on a novel device. Clin J Pain. 2009;25(8):705Y710. 16. Kuttner L. Management of young children’s acute pain and anxiety during invasive medical procedures. Pediatrician. 1989;16(1Y2):39Y44. 17. Cohen LL, Lemanek K, Blount RL, et al. Evidence-based assessment of pediatric pain. J Pediatr Psychol. 2008;33(9):939Y955; discussion 956Y957. 18. Hicks CL, von Baeyer CL, Spafford PA, et al. The Faces Pain ScaleYRevised: toward a common metric in pediatric pain measurement. Pain. 2001;93(2):173Y183. 19. Stinson JN, Kavanagh T, Yamada J, et al. Systematic review of the psychometric properties, interpretability and feasibility of self-report pain intensity measures for use in clinical trials in children and adolescents. Pain. 2006;125(1Y2):143Y157. 20. Jay SM, Elliott C. Behavioral observation scales for measuring children’s distress: the effects of increased methodological rigor. J Consult Clin Psychol. 1984;52(6):1106Y1107. 21. Cohen Reis E, Holubkov R. Vapocoolant spray is equally effective as EMLA cream in reducing immunization pain in school-aged children. Pediatrics. 1997;100(6):E5. 22. Faul F, Erdfelder E, Lang AG, et al. G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods. 2007;39:175Y191. 23. Maclaren JE, Cohen LL. Interventions for paediatric procedure-related pain in primary care. Paediatr Child Health. 2007;12(2):111Y116.

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