Share this article on:

Anesthesia Induction Using Video Glasses as a Distraction Tool for the Management of Preoperative Anxiety in Children

Kerimoglu, Beklen MD*; Neuman, Avishai MD; Paul, Jonathan BA; Stefanov, Dimitre G. PhD*; Twersky, Rebecca MD*

doi: 10.1213/ANE.0b013e3182a8c18f
Pediatric Anesthesiology: Research Report

BACKGROUND: Distraction technology suitable for the perioperative setting is readily available, but there is little evidence to show how it compares with oral midazolam in managing anxiety. Video glasses, which enable children to view and listen to cartoons and movies, may be used through the completion of inhaled induction. We compared the efficacy of oral midazolam and behavioral distraction with video glasses in managing preoperative anxiety in children.

METHODS: In this prospective, randomized study, 96 children aged 4 to 9 years undergoing outpatient surgery were recruited to one of 3 intervention groups receiving midazolam, video glasses, or both. The Modified Yale Preoperative Anxiety Scale was the primary dependent measure used to assess anxiety at baseline before intervention, 20 minutes later at transport to the operating room (OR), and during mask induction.

RESULTS: There was no significant increase in anxiety score within any group between baseline and OR transport (P = 0.21, 0.42, and 0.57 for midazolam, video glasses, and combined groups, respectively). An increase in anxiety, though not large enough to be clinically significant, was observed from baseline to induction in the midazolam and combined groups (P = 0.02 and 0.03) but not in the video glasses group (P = 0.38). Confidence intervals for pairwise comparisons in Modified Yale Preoperative Anxiety Scale changes among groups were all within a clinically significant difference of 15 units.

CONCLUSIONS: The use of video glasses and midazolam alone or in combination maintains baseline levels of anxiety at time of transport to the OR and prevents significantly increased anxiety during induction of anesthesia in children. Video glasses are not inferior to midazolam for preoperative anxiolysis and provide a safe, noninvasive, nonpharmacologic, and pleasant alternative.

From the *Department of Anesthesiology, SUNY Downstate Medical Center, Brooklyn; Department of Anesthesiology, New York Hospital Queens, Flushing; and New York College of Osteopathic Medicine of NYIT, Old Westbury, New York.

Accepted for publication July 30, 2013.

Funding: Supported by departmental funding.

The authors declare no conflicts of interest.

This report was previously presented, in part, at the American Society of Anesthesiologists Annual Meeting, Anesthesiology 2011, in Chicago, Illinois.

Reprints will not be available from the authors.

Address correspondence to Beklen Kerimoglu, MD, Department of Anesthesiology, SUNY Downstate Medical Center, 470 Clarkson Ave., Brooklyn, NY 11203. Address e-mail to bkkerimoglu@aol.com.

Between 40% and 60% of pediatric patients experience preoperative anxiety that is associated with maladaptive behavior lasting multiple weeks after surgery.1 Distress before surgery has been associated with short- and long-term consequences, including risks of emergence delirium and maladaptive postoperative behaviors such as separation anxiety and eating disorders.2–5 Oral midazolam, the most commonly used anxiolytic, carries both operational drawbacks and safety limitations. Midazolam can delay a patient’s recovery6–8 and may be contraindicated for those with moderate-to-severe obstructive sleep apnea.9

Behavioral modalities have shown anxiolytic efficacy, although few have been evaluated through direct comparison to premedication with midazolam. The use of music and childcare specialists may reduce distress through distraction.10,11 Even the style of communication used by anesthesiologists and staff may have an effect on a child’s preoperative anxiety. The same group that demonstrated that physicians and nurses can be trained to distract children have begun a randomized control trial to evaluate the impact of this training on anxiety.12 Another behavioral approach, named the ADVANCE program, revealed in 2 studies13,14 that teaching families to expose their child to a facemask and distract them on the day of surgery achieved better anxiety control than simple parental presence or midazolam.

Specialized support staff and physician or family training programs are not always available and may be prohibitively expensive. Yet distraction can still be achieved through devices that are familiar to many children today. Cognitive engagement with video games has been shown to achieve superior anxiolysis as compared with midazolam and parental presence.15 Virtual reality systems have demonstrated utility in the management of severe burn and cold pressor pain.16,17 The trend towards use of distraction technology seems to be growing globally. A group in South Korea recently found that pediatric patients have less preoperative anxiety watching cartoons on tablet and notebook computers not only compared with control subjects but also to children playing with traditional toys.18

Still, no study has used a device to completely isolate both auditory and visual senses from the perioperative environment up to and during induction of anesthesia. Video glasses are unique because they provide a portable means of viewing video on a magnified scale for a large screen experience while traveling. Their narrow dimensions enable continuous use up to and during inhaled induction. The goal of this study was to compare distraction with video glasses to premedication with midazolam by evaluating their ability to control preoperative anxiety.

Back to Top | Article Outline

METHODS

Children aged 4 to 9 years and scheduled to undergo ambulatory surgery with general anesthesia were recruited for this prospective, randomized study, which was approved by IRBs at SUNY Downstate Medical Center and its affiliate Long Island College Hospital. Written informed consent was obtained from parents and assent from children older than 6 years of age for all study participants. Patients with ASA physical status greater than II, undergoing emergency surgery, taking psychoactive medications, or with a history of severe sleep apnea, chronic illness, or cognitive dysfunction were excluded from participation.

After consent was obtained, subjects were randomized into one of 3 study groups. Blocked randomization of small group sizes (multiples of 3) was used with a sealed envelope technique under close personal control to ensure equal group sizes. Different individuals were responsible for allocation and recruitment, and the use of multiple recruiters offset the ability to predict group assignments. At intervention, patients in group M were given medication (midazolam HCl syrup, 0.3 mg/kg; Roche Laboratories, Branchburg, NJ); patients in group VG were given video glasses (Vuzix®, Vuzix Corporation, Rochester, NY) connected to a portable media player; and patients in group M + VG were given both medication and video glasses. Children randomized to groups VG and M + VG chose from a selection of age-appropriate television programs, and medication was administered at the same time that the video began for those in group M + VG. It is standard of care at our institutions where supervision is not constant to use low-dose midazolam, which provides adequate sedation of children.19,20

The modified Yale Preoperative Anxiety Scale (mYPAS) was used to measure anxiety at baseline before intervention (T1), at time of transport to the operating room (OR) 20 minutes later (T2), and during mask induction in the OR (T3). The primary dependent measure of the impact of our interventions was the change in mYPAS from T1 to T3. Transport at T2 coincided with separation from parents per standard practice at both medical centers where this study was conducted, and the change in mYPAS from baseline to T2 was of secondary interest.

The mYPAS is an observer-rated instrument, which quantifies anxiety through 5 categories, including activity, vocalizations, emotional expressivity, state of apparent arousal, and use of parents. MYPAS scores have strong inter- and intraobserver reliability as compared with other behavioral anxiety measurements.21,22 The scale has also demonstrated sensitivity, as scores increase between baseline and anesthesia induction in the absence of intervention.23 Categorical scores ranging from 1 to 4 (except vocalizations, 1–6) were assigned partial weights and added to obtain a score ranging from 23 to 100 for each of the 3 time points. Training for mYPAS scoring occurred in real time with patients at both academic centers where subjects were enrolled. Two observers were trained together for data collected in 2011, and 4 were trained together for data collected in 2009 to 2010. Each observer-in-training and the principal investigator scored the same patient alongside one another independently and discussed differences afterwards until agreement was reached. Over the course of 3 to 5 days, each observer performed trial scoring on N ≥ 25 patients and did not begin scoring patients for study inclusion until the agreement in mYPAS scores was ≤5 mYPAS points.

Heart rate was recorded as a potential secondary measure of anxiety. Nursing staff obtained heart rate in the holding area and after attachment of SPO2 and electrocardiogram monitors in the OR, and observers recorded values at T1-3 along with the mYPAS score. Video glasses were removed after mask induction (oxygen ± nitrous oxide with sevoflurane) once the child was determined to be unconscious via tactile stimulation. The same observer stayed with the given patient from intervention to video glasses removal and recorded all mYPAS and heart rate data.

Baseline characteristics among groups were compared using the ANOVA, Kruskal-Wallis, or χ2 tests. We used nonparametric statistical tests for mYPAS analysis, due to the skewed distribution of these data. The Kruskal-Wallis test was used to compare the anxiety scores at T2 and T3. When significant differences were found, the test was followed by pairwise comparison using the Mann-Whitney test, with Bonferroni adjustment for multiple testing. We used Wilcoxon signed rank test to determine whether there was a significant change in mYPAS from baseline to T2 and T3 for each intervention group separately. The Kruskal-Wallis test was used to compare the change in anxiety scores from baseline to T2 and to T3 among the intervention groups. This test detects deviations from the null hypothesis of identical distribution for this outcome across interventions. A disadvantage of the test is the limited interpretation in the case when the null hypothesis is rejected. However, a more specific interpretation is possible when the outcome has the same distribution across groups, with the exception of possible location shifts. We used a test for equal variances often referred to as Conover test,24 to test this assumption. The location shifts were estimated from baseline to T2 and T3 using the Hodges-Lehman method,25 in pairwise comparisons among treatments.

Linear mixed models were used to analyze the longitudinal data for heart rate. We used fixed effects for intervention, intervention time points, and their interaction. We used random effect for child, which accounts for the correlated observations from the same child. We tested models with different covariance structure using the likelihood ratio test, and the unstructured covariance matrix provided the best fit. Standard diagnostic checks of model adequacy were performed and satisfied. The Spearman correlation coefficient was used to test for an association between heart rate and mYPAS score at each time point.

Data for heart rate are presented as mean ± SD and as median and interquartile range for mYPAS. All statistical analysis was performed by SAS version 9.2 (SAS Inc., Cary, NC). A P value <0.05 was considered statistically significant.

We considered a clinically significant difference in mYPAS to be 15, which is consistent with recent studies using the scale.18 Using the Mann-Whitney test with nQuery Advisor 7.0 (Statistical Solutions, Saugus, MA), it was determined that a sample size of 30 patients per group was sufficient to detect a mean difference of 15 points in mYPAS, assuming a standard deviation (SD) of 19.2 with a significance level of 0.05 and a power of 80%. Data from a similar study comparing distraction with technology to midazolam15 were used to estimate the SD for the increase in mYPAS between baseline and induction by the method of Hozo et al.26

Back to Top | Article Outline

RESULTS

Ninety-six children participated in this randomized, nonblinded study between July 2009 and August 2011. Of these patients, 32 were randomized to group M, 32 to group VG, and 32 to group M + VG. Six subjects initially randomized to the study were not included in the data analysis, due to noncompliance with our protocol and because incomplete data were available, in accordance with a per protocol approach.27 Five of these patients removed the video glasses preemtively, and 1 patient expelled the midazolam syrup and refused premedication. There were no significant differences in demographic characteristics (age, gender, height, and weight) among study groups, as summarized in Table 1.

Table 1

Table 1

Back to Top | Article Outline

Modified Yale Preoperative Anxiety Scale

Since an mYPAS score above 30 indicates anxiety,22 most of the children demonstrated anxiety before intervention at T1 (59%, 66%, and 56% of those in groups M, VG, and M + VG, respectively). The difference among these percentages of patients with baseline anxiety was not significant (P = 0.7). Table 2 shows that the median mYPAS score in each group was higher than 30 at baseline.

Table 2

Table 2

There was no significant difference in anxiety among groups at T1 or T3 (Table 2). There was a significant difference at T2 (P = 0.04), with the lowest median anxiety scores recorded in the VG group (Table 2). However, no pairwise comparisons were found to be significant after Bonferroni correction for multiple testing.

The changes in mYPAS scores within intervention groups from baseline to transport and from baseline to induction are illustrated in Figs 1 and 2. There was no significant increase in anxiety scores in any group from baseline to OR transport (P =0.21, 0.42, and 0.57 for groups M, VG, and M + VG, respectively). There was also no significant difference in mYPAS increment among the 3 groups during this timeframe (P = 0.26), Table 3.

Table 3

Table 3

Figure 1

Figure 1

Figure 2

Figure 2

The primary measure of the effect of our interventions on anxiety was the change in mYPAS from baseline to induction. A significant increase in anxiety was observed from T1 to T3 in the M and M + VG groups (P = 0.02 and 0.03, respectively) but not in the VG group (P = 0.38). However, no significant difference was found among the 3 groups for the mYPAS change (P = 0.39), Table 3.

We estimated the location shift between each pair of intervention groups for the mYPAS change from baseline to induction to compare them with a clinically significant difference of 15 points. These calculations assume that the outcome has the same distribution across groups, with the exception of possible shifts. We used Conover test24 to determine the validity of this assumption with a significant result indicating that the assumption is not valid. The test was not significant (P = 0.81) for the change in mYPAS from baseline to T3, and borderline significant for the change from baseline to T2 (P = 0.05). The estimated location shifts with 95% confidence intervals (CIs) are presented in Table 4, and all were <the clinically significant difference of 15 points.

Table 4

Table 4

Back to Top | Article Outline

Heart Rate

There were no significant differences among the intervention groups when analyzed separately at each time point (Table 2). For increased precision in determining the treatment effects, we analyzed the data from the 3 time points using linear mixed models, as specified in the Methods section. The interaction term between time and treatment was not significant (P = 0.54) and was removed from the final model. The treatment effect was not significant (P = 0.99), indicating no significant differences among the groups at any time. We found that heart rate increased significantly between T1 and T2 (18.8, 95% CI, 14.0–23.6, P < 0.001) but not between T2 and T3 (2.0, 95% CI, −2.4 to 6.4, P = 0.37) for all groups combined, as illustrated in Figure 3. The overall change of heart rate from T1 to T3 was significant (20.8, 95% CI, 16.3–25.2, P < 0.001).

Figure 3

Figure 3

To assess the association between the 2 outcomes, Spearman correlation coefficients were calculated between heart rate and mYPAS at each time point. Only a weak correlation was observed between heart rate and mYPAS at T1 (r = 0.32, P = 0.002); there was no significant correlation between heart rate and mYPAS at T2 and T3 (r = 0.16, P = 0.12 and r = 0.17, P = 0.10, respectively).

Back to Top | Article Outline

DISCUSSION

The use of distraction techniques for anxiolysis is familiar to pediatric anesthesiologists. Stress can be minimized by methods as simple as challenging the child to “to blow up the balloon” or as elaborate as dressing up in clown costumes.28 However, technology that is popular among many children worldwide might offer more complete distraction and anxiety management. A recent editorial predicts that computer-aided distraction, if proven as effective as midazolam, may become a common anxiolytic tool.29

The primary goal of this study was to determine whether distraction with video glasses has anxiolytic efficacy through comparison with midazolam premedication, the current “gold standard” in treating preoperative anxiety. Most children in each intervention group demonstrated some anxiety throughout the perioperative period, with the exception of the video glasses—only group at time of transport to the OR. Our results indicate that the level of preoperative anxiety experienced by a child given midazolam or video glasses or both is the same, because there was no difference in anxiety among groups at each of the 3 time points.

Previous studies measuring the effect of interventions on preoperative anxiety have examined mYPAS changes between baseline and inhaled induction, because the latter event is associated with the greatest levels of distress.10,30 During this time period, we found modest increases in anxiety in the midazolam and the midazolam plus video glasses groups, while no significant increase was found in the video glasses only group. We cannot interpret this to mean that the video glasses group outperformed both groups with midazolam, as the increases in mYPAS were not clinically significant (<15 points). Between baseline and transport to the OR, a time point which is unique to this study, mYPAS scores did not change in any of the 3 groups, indicating that parent separation did not affect anxiety. Therefore, all 3 interventions prevented clinically significant increases in preoperative anxiety from baseline. The goal of pharmacologic or behavioral anxiolytics may be to mitigate large spikes in anxiety that could have deleterious postoperative consequences.

Although heart rate correlated with anxiety and was comparable among groups before intervention, this correlation was not observed during transport to the OR nor at induction. The increase in heart rate at the time of transport may be attributed to influences other than anxiety, such as physical movement, and heart rate is probably not an accurate secondary measure of anxiety in the preoperative setting.

The limitations of our study included lack of placebo control and potential observer bias. Because it is standard of care at our hospitals to provide preoperative anxiolysis to all children, we did not recruit subjects to a true control group that would receive neither medication nor video glasses. Studies using a behavioral assessment tool such as the mYPAS to measure anxiety are limited by observer bias. Raters could not be blinded to the intervention group because of the obvious placement of video glasses. However, observers were blind to group assignment when recording initial anxiety scores at baseline before intervention. It should also be noted that, although our observers were trained until a consistent level of agreement in anxiety scores was reached, we did not retain the data required to report their inter- and intrarater reliability. We encountered resistance from some patients and their families regarding the type of media offered. Patient recruitment may have been more extensive with a broader scope of movies and television programs catering to various languages and cultures. As we excluded those younger than 4 years of age from study participation on the premise that they would be unable to remain attentive to video glasses, our findings are not applicable to very young children experiencing preoperative anxiety. A final limitation to our approach is that postoperative markers of anxiety including emergence delirium and behavioral dysfunction were not measured.

Parents did not accompany subjects beyond the preoperative holding area in accordance with common practice in our hospitals. An evidence-based review of parental presence during induction found little anxiolytic influence of parents during transport to or within the OR31 although there are data to suggest that parental presence became more common between the 1990s and 2000s.32 Parents themselves might gain relief when their children are distracted, regardless of whether they have a calming effect. Since the conclusion of our study, it has been reported that increases in parental anxiety are mitigated when children watch audio-visual cartoons with subject matter that prepares them for the perioperative experience.33 The evaluation of other pediatric applications for video glasses might therefore benefit from a study arm for parents as well.

Lee et al.15,18 expand on previous pediatric studies of anxiolysis using modern technology such as video games and demonstrate that watching cartoons on small computers reduces preoperative anxiety. Some nuances in patient care may limit the direct comparison of our findings to this recent work. In their study, children were admitted overnight before procedures, and therefore, their observation intervals between baseline and intervention anxiety measurements were longer. Also, our current practice is to use inhaled rather than IV anesthetics for pediatric induction to avoid any distress caused by catheter placement performed in the holding area. In spite of these differences, our data reinforce that there is anxiolytic value to portable multimedia and indicate that the added audio and visual distraction provided by video glasses results in anxiety levels that are equivalent to those experienced with sedative medication.

We conclude that video glasses are not inferior to midazolam for preoperative anxiety management in children. They may be used as a safe alternative when medication is unavailable or inappropriate. The advantage that video glasses have over other distraction modalities such as handheld computers and games is that their use can be continued during induction without interfering with delivery of anesthetics via facemask. They may also be more cost effective than pharmacologic modalities; nonmedical personnel may administer video glasses, and the initial acquisition cost of the technology may amount to less than the cumulative cost of midazolam. We hypothesize that video glasses have anxiolytic utility beyond the OR. Future studies may be able to evaluate use of this modality in multilingual and culturally diverse populations, during regional anesthesia or during imaging studies where general anesthesia is not indicated.

Back to Top | Article Outline

Safety Notice

Since the completion of this study, the authors have learned that Vuzix® recommends use of their video glasses and other products in those aged at least 7 years because of the concept that younger individuals are still developing their gaze abilities. In spite of this, we found that subjects of all ages viewed the cartoons on the video glasses with ease and without complaints such as headache, blurriness, or other vision changes. Other video glasses brands, such as ezVision® (ezGear, Murray, UT) and Brookstone® (Brookstone, Merrimack, NH), do not list any age-specific precautions and provide an almost identical experience of a 50-inch virtual single screen with built-in audio ear pieces and are similarly compatible with portable media devices. We recommend that anesthesiology and surgical staff consider this information in evaluating video glasses for potential use with their pediatric patients.

Back to Top | Article Outline

DISCLOSURES

Name: Beklen Kerimoglu, MD.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Attestation: Beklen Kerimoglu has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Avishai Neuman, MD.

Contribution: This author helped design the study.

Attestation: Avishai Neuman has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Jonathan Paul, BA.

Contribution: This author helped conduct the study, analyze the data and wrote the manuscript.

Attestation: Jonathan Paul has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.

Name: Dimitre G. Stefanov, PhD.

Contribution: This author helped analyze the data and write the manuscript.

Attestation: Dimitre G. Stefanov has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Rebecca Twersky, MD.

Contribution: This author helped design the study and write the manuscript.

Attestation: Rebecca Twersky has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

This manuscript was handled by: Peter J. Davis, MD.

Back to Top | Article Outline

ACKNOWLEDGMENTS

We gratefully acknowledge the following residents and medical students who assisted in patient recruitment: Mark Haham, Jacob Hedden, Uvie Whiteru, Shimson Wiesel, Kevin George, Jiandong Wei, Tarang Safi, Yehuda Mond, Patricia Santos, and the statistical expertise of Dr. John Hartung.

Back to Top | Article Outline

REFERENCES

1. Kain ZN, Mayes LC, O’Connor TZ, Cicchetti DV. Preoperative anxiety in children. Predictors and outcomes. Arch Pediatr Adolesc Med. 1996;150:1238–45
2. Kain ZN, Mayes LC, Caldwell-Andrews AA, Karas DE, McClain BC. Preoperative anxiety, postoperative pain, and behavioral recovery in young children undergoing surgery. Pediatrics. 2006;118:651–8
3. Wang SM, Kain ZN. Preoperative anxiety and postoperative nausea and vomiting in children: is there an association? Anesth Analg. 2000;90:571–5
4. Fortier MA, Del Rosario AM, Rosenbaum A, Kain ZN. Beyond pain: predictors of postoperative maladaptive behavior change in children. Paediatr Anaesth. 2010;20:445–53
5. Kain ZN. Postoperative maladaptive behavioral changes in children: incidence, risks factors and interventions. Acta Anaesthesiol Belg. 2000;51:217–26
6. McCann ME, Kain ZN. The management of preoperative anxiety in children: an update. Anesth Analg. 2001;93:98–105
7. Viitanen H, Annila P, Viitanen M, Yli-Hankala A. Midazolam premedication delays recovery from propofol-induced sevoflurane anesthesia in children 1-3 yr. Can J Anaesth. 1999;46:766–71
8. Viitanen H, Annila P, Viitanen M, Tarkkila P. Premedication with midazolam delays recovery after ambulatory sevoflurane anesthesia in children. Anesth Analg. 1999;89:75–9
9. Seet E, Chung F. Management of sleep apnea in adults - functional algorithms for the perioperative period: continuing Professional Development. Can J Anaesth. 2010;57:849–64
10. Kain ZN, Caldwell-Andrews AA, Krivutza DM, Weinberg ME, Gaal D, Wang SM, Mayes LC. Interactive music therapy as a treatment for preoperative anxiety in children: a randomized controlled trial. Anesth Analg. 2004;98:1260–6
11. Brewer S, Gleditsch SL, Syblik D, Tietjens ME, Vacik HW. Pediatric anxiety: child life intervention in day surgery. J Pediatr Nurs. 2006;21:13–22
12. Martin SR, Chorney JM, Tan ET, Fortier MA, Blount RL, Wald SH, Shapiro NL, Strom SL, Patel S, Kain ZN. Changing healthcare providers’ behavior during pediatric inductions with an empirically based intervention. Anesthesiology. 2011;115:18–27
13. Kain ZN, Caldwell-Andrews AA, Mayes LC, Weinberg ME, Wang SM, MacLaren JE, Blount RL. Family-centered preparation for surgery improves perioperative outcomes in children: a randomized controlled trial. Anesthesiology. 2007;106:65–74
14. Fortier MA, Blount RL, Wang SM, Mayes LC, Kain ZN. Analysing a family-centred preoperative intervention programme: a dismantling approach. Br J Anaesth. 2011;106:713–8
15. Patel A, Schieble T, Davidson M, Tran MC, Schoenberg C, Delphin E, Bennett H. Distraction with a hand-held video game reduces pediatric preoperative anxiety. Paediatr Anaesth. 2006;16:1019–27
16. Hoffman HG, Chambers GT, Meyer WJ 3rd, Arceneaux LL, Russell WJ, Seibel EJ, Richards TL, Sharar SR, Patterson DR. Virtual reality as an adjunctive non-pharmacologic analgesic for acute burn pain during medical procedures. Ann Behav Med. 2011;41:183–91
17. Dahlquist LM, Weiss KE, Law EF, Sil S, Herbert LJ, Horn SB, Wohlheiter K, Ackerman CS. Effects of videogame distraction and a virtual reality type head-mounted display helmet on cold pressor pain in young elementary school-aged children. J Pediatr Psychol. 2010;35:617–25
18. Lee J, Lee J, Lim H, Son JS, Lee JR, Kim DC, Ko S. Cartoon distraction alleviates anxiety in children during induction of anesthesia. Anesth Analg. 2012;115:1168–73
19. Reed MD, Rodarte A, Blumer JL, Khoo KC, Akbari B, Pou S, Pharmd, Kearns GLPediatric Pharmacology Research Unit Network. . The single-dose pharmacokinetics of midazolam and its primary metabolite in pediatric patients after oral and intravenous administration. J Clin Pharmacol. 2001;41:1359–69
20. Coté CJ, Cohen IT, Suresh S, Rabb M, Rose JB, Weldon BC, Davis PJ, Bikhazi GB, Karl HW, Hummer KA, Hannallah RS, Khoo KC, Collins P. A comparison of three doses of a commercially prepared oral midazolam syrup in children. Anesth Analg. 2002;94:37–43
21. Kain ZN, Mayes LC, Cicchetti DV, Caramico LA, Spieker M, Nygren MM, Rimar S. Measurement tool for preoperative anxiety in young children: the yale preoperative anxiety scale. Child Neuropsychol. 1995;1:203–10
22. Kain ZN, Mayes LC, Cicchetti DV, Bagnall AL, Finley JD, Hofstadter MB. The Yale Preoperative Anxiety Scale: how does it compare with a “gold standard”? Anesth Analg. 1997;85:783–8
23. Finley GA, Stewart SH, Buffett-Jerrott S, Wright KD, Millington D. High levels of impulsivity may contraindicate midazolam premedication in children. Can J Anaesth. 2006;53:73–8
24. Conover WJ Practical Nonparametric Statistics. 19993rd ed New York, NY Wiley
25. Lehmann EL, D’Abrera HJM Nonparametrics: Statistical Methods Based on Ranks. 2006Rev. 1st ed New York, NY Springer
26. Hozo SP, Djulbegovic B, Hozo I. Estimating the mean and variance from the median, range, and the size of a sample. BMC Med Res Methodol. 2005;5:13
27. Gupta SK. Intention-to-treat concept: a review. Perspect Clin Res. 2011;2:109–12
28. Vagnoli L, Caprilli S, Robiglio A, Messeri A. Clown doctors as a treatment for preoperative anxiety in children: a randomized, prospective study. Pediatrics. 2005;116:e563–7
29. Litman RS. Allaying anxiety in children: when a funny thing happens on the way to the operating room. Anesthesiology. 2011;115:4–5
30. Kain ZN, Mayes LC, Caramico LA, Silver D, Spieker M, Nygren MM, Anderson G, Rimar S. Parental presence during induction of anesthesia. A randomized controlled trial. Anesthesiology. 1996;84:1060–7
31. Chundamala J, Wright JG, Kemp SM. An evidence-based review of parental presence during anesthesia induction and parent/child anxiety. Can J Anaesth. 2009;56:57–70
32. Kain ZN, Caldwell-Andrews AA, Krivutza DM, Weinberg ME, Wang SM, Gaal D. Trends in the practice of parental presence during induction of anesthesia and the use of preoperative sedative premedication in the United States, 1995-2002: results of a follow-up national survey. Anesth Analg. 2004;98:1252–9
33. Berghmans J, Weber F, van Akoleyen C, Utens E, Adriaenssens P, Klein J, Himpe D. Audiovisual aid viewing immediately before pediatric induction moderates the accompanying parents’ anxiety. Paediatr Anaesth. 2012;22:386–92
© 2013 International Anesthesia Research Society