Preschool children undergoing surgery are particularly vulnerable to separation anxiety before anesthesia because they are dependent on their parents and are old enough to recognize parental absence.1–3 Furthermore, the placement of a mask on the face and the inhalation of volatile anesthetics in the absence of parents further distresses young children, sometimes to the extent of refusal of mask induction.1,2,4,5 A more anxious state preoperatively results in poor cooperation at anesthetic induction and may be associated with emergence delirium and negative behavioral change after surgery.6,7 Therefore, the transfer of children from a preoperative holding area to the operating room (OR) and the smooth induction of anesthesia without heightened anxiety may be of paramount importance in terms of minimizing perioperative distress and improving behavioral outcome.
Portable multimedia devices, such as smart phones, tablet computers, and handheld DVD players, are readily available at low cost. Age-appropriate video clips and video games are commonly used as effective distraction tools for medical and surgical procedures in children.8,9 In anesthetic practice, active distraction by a handheld video game with parental presence was found to be more effective than premedication or parental presence only for reducing anxiety and improving cooperation during mask induction in children aged 4 to 12 years.10 In younger children, whose cognitive and motor development were not advanced enough to play interactive video games, passive viewing of an animated cartoon also proved a more effective distraction than traditional storytelling, game-playing, nonprocedural talking, or humor during mask induction.11 However, previous studies did not completely control for parental presence or used parents to keep children relaxed during video distraction.9–11
Thus, we performed this study to determine whether video distraction per se is capable of alleviating preoperative anxiety and improving cooperation independent of parental presence and whether a combination of video distraction and parental presence is more effective than either intervention in preschool children during mask induction of anesthesia. The primary end point of this study was a change in anxiety level from baseline to induction. In addition, we investigated the effect of each proactive intervention on postoperative behavioral outcomes, that is, on the incidences of emergence delirium and new-onset maladaptive behavioral changes.
This prospective, randomized study was approved by the IRB of Yeungnam University Hospital in South Korea and was registered with ClinicalTrials.gov on the December 30, 2013 (NCT02027844). One hundred seventeen children aged between 2 and 7 years, ASA physical status I or II scheduled for elective minor surgery under general anesthesia were enrolled. Children with a chronic illness, developmental delay, a neuropsychiatric disease, cancer, experience of a recent stressful life event, previous anesthetic experience, sedative medication, or emergency surgery were excluded. Written informed consent was obtained from parents, and verbal assent was obtained from children older than 6 years before the day of surgery.
No participant received sedative premedication before anesthesia. After arriving in the preoperative holding area, participants were allocated to 1 of the 3 study groups: group V (distraction by watching an animated cartoon video), group P (parental presence), or group VP (video distraction plus parental presence), throughout induction of anesthesia, using a computer-generated random assignment scheme. In group V, children were allowed to select 1 animated cartoon video in a smartphone offered by the researcher or parents and started to watch it with or without parents while waiting in the preoperative holding area. Children in group V were separated from their parents in the preoperative holding area and transported to the OR. Anesthesia was induced while children continued to view the chosen video. In group P, 1 parent accompanied the child to the OR and stayed during the induction of anesthesia, and in group VP, children watched a cartoon video with their parents throughout the whole anesthesia induction process.
After arrival in the OR, children were given the choice to sit up or lie down on the operating table. All participants were introduced to the facemask, which was detached from the anesthetic circuit, before induction. The anesthesiologist explained the anesthesia induction process to children and gently asked them to breathe deeply. A pulse oximeter and electrocardiogram were used for continuous monitoring during induction. Anesthesia was induced by mask inhalation with incrementing sevoflurane up to 8% with N2O (4 L/min) and oxygen (2 L/min). The anesthesiologist carefully positioned the facemask/anesthesia circuit so as not to interfere with video watching or the parent. When a participant closed his/her eyes and failed to respond to his/her name, the video was discontinued and the parent was escorted out of the OR by a nurse. Noninvasive arterial blood pressure was measured as soon as possible. After endotracheal intubation, anesthesia was maintained by sevoflurane inhalation at an end-tidal concentration of 1.5% to 3.0% in 50% oxygen and by IV remifentanil infusion at a rate of 0.05 to 0.1 μg/kg/min during surgery. At the end of surgery, sevoflurane administration was discontinued, and after awakening with adequate spontaneous ventilation, children were tracheally extubated and transferred to the postanesthesia care unit (PACU). Heart rate, SpO2, and respiratory rate were monitored in the PACU. Parents were allowed to rejoin their children in the PACU. If a child complained of pain or exhibited signs or symptoms of pain, IV fentanyl 1 μg/kg was administered in the PACU. All clinical management decisions were made by the anesthesiologist responsible for the care of the patients.
Children’s anxiety levels throughout anesthesia induction were assessed using the modified Yale Preoperative Anxiety Scale (mYPAS) at 3 time points, that is, while waiting in the preoperative holding area (T0; baseline), on entering the OR (T1), and during mask induction (T2). mYPAS scores are obtained by summing the scores of 22 items in 5 behavioral categories: activity, state of apparent arousal, vocalization, emotional expression, and the use of parents.12 In group V, the interaction with the parent was assessed by slightly modifying the original components of the “use of parents” because of parental absence.
An mYPAS score of >30 indicates the presence of significant anxiety.12 The induction compliance checklist (ICC) was used to assess cooperation during induction.13 Both mYPAS and ICC scores were assessed by a trained observer in real time during the perioperative period. Before patients were enrolled in this study, the observer was trained in how to perform mYPAS and ICC scoring by reviewing videotapes of children at induction of anesthesia until 80% agreement with the scores allocated by a psychologist was achieved consistently, as suggested by Sadhasivam et al.14
Parental anxiety was assessed using the Korean version of Spielberger’s State-Trait Anxiety Inventory (STAI), which evaluates trait (baseline) and state (situational) anxiety.15 In the preoperative holding area, both trait and state anxiety scores were measured to investigate the effect of parental anxiety on child anxiety. State anxiety scores after induction were obtained to assess the effect of the 3 interventions on situational anxiety changes in parents.
After surgery, postoperative pain was assessed using the Children’s Hospital of Eastern Ontario Pain (CHEOP) scale.16 Emergence delirium was evaluated using the Pediatric Anesthesia Emergence Delirium (PAED) scale at 10-minute intervals for 30 minutes after arrival in the PACU.17 When the highest PAED score recorded at any time exceeded 10, emergence delirium was deemed to be present.
An investigator, unaware of group assignments, contacted parents and requested that they complete the Post-Hospitalization Behavior Questionnaire (PHBQ) at 1 and 14 days postoperatively by phone. The PHBQ contains 27 items in 6 categories: general anxiety, separation anxiety, anxiety about sleep, eating disturbance, aggression toward authority, and apathy/withdrawal.18 Negative behavioral change development after anesthesia and surgery was recorded. Both CHEOP and PAED scores and PHBQ interviews were performed by an independent observer unaware of group assignments.
Power analysis was conducted using G*Power ver. 3.1.5. An effect size of 0.31 was estimated from the variance of mean mYPAS differences between the baseline and the induction of anesthesia among the 3 groups and the square of the common SD within each group based on the results of a pilot study conducted on 27 children. The data of the pilot study were not included in data analysis in the current study. A sample size of 35 participants per group was calculated by 1-way analysis of variance (ANOVA) to yield an 80% power to detect this effect size at a set α value of 0.05 among the 3 groups. Thirty-nine participants per group were recruited to account for a 10% dropout rate due to withdrawal of consent, a change in anesthetic/surgical plan, or follow-up loss.
Statistical analysis was performed using SPSS version 19 (SPSS Inc., Chicago, IL). The Kolmogorov-Smirnov Lilliefors goodness-of-fit test was used to verify normalities of the residuals of all continuous variables. When P values of the data were >0.05, they were considered normally distributed. The normally distributed continuous variables, such as age, weight, and duration of anesthesia, were presented as the means ± SDs and were compared using the 1-way ANOVA. Statistical significance was accepted for P values <0.05. Nonnormally distributed continuous variables, such as mYPAS scores at each time point and ICC, were presented as medians and ranges and compared using the nonparametric Kruskal-Wallis test. The test was followed the Mann-Whitney U test with Bonferroni adjustment for multiple pairwise comparisons (3 comparisons) if a significant intergroup difference was found. A Bonferroni-adjusted P value <0.017 (0.05/3) was considered statistically significant. The change in mYPAS scores over time among the 3 groups was compared using the repeated measures ANOVA.
Categorical variables were analyzed using the χ2 test or the Fisher exact test. Wilson score interval without continuity correction19 was used to compare Bonferroni-adjusted 95% confidence interval for differences in proportion of participants with increased anxiety from baseline to OR entry and induction of anesthesia among interventions. Statistical significance was considered for P < 0.017 after Bonferroni adjustment for 3 comparisons (0.05/3). The McNemar test was used to compare the incidence of newly developed maladaptive behavior 1 day and 2 weeks after surgery. Correlations between mYPAS score during induction of anesthesia and PAED scores or numbers of patients exhibiting a postoperative negative behavioral change were assessed using the Pearson correlation or the Spearman rank correlation coefficients, respectively. Statistical significance was accepted for P values <0.05.
One hundred seventeen children were initially enrolled. Eleven children were excluded because of withdrawal of consent, incomplete data, or loss to follow-up (Fig. 1). Two children in group P were excluded because they viewed an animated cartoon with their parents while waiting in the preoperative holding area after random allocation. Thus, 104 participants completed the study, and they were included in the data analysis. No significant intergroup differences in demographic or surgical characteristics were observed (Table 1). Mothers predominantly accompanied children to the OR and stayed during anesthesia induction in groups P (n = 27, 81.8%) and VP (n = 26, 70.3%).
The median mYPAS scores were comparably lower than 30 at T0 (P = 0.558), and the number of children exhibiting baseline anxiety (an mYPAS score > 30) was not different among groups (Table 2, P = 0.824) before intervention. After intervention, mYPAS scores were different among the 3 groups at T1 (P = 0.002) and T2 (P = 0.012). Specifically, children in group V exhibited lower mYPAS scores compared with the other 2 groups at both T1 (P < 0.001 versus group P and P = 0.015 versus group VP) and T2 (P = 0.012 versus group P and P = 0.008 versus group VP). However, the overall changes in mYPAS scores from baseline to induction of anesthesia were not different among the 3 groups (P = 0.049). The proportion of children who increased their mYPAS scores was higher in group P compared with group V from T0 to T1 (Bonferroni-adjusted 95% confidence interval for difference 2 to 49) but was similar in all groups from T0 to T2 (Fig. 2, Table 3).
The compliance of children at mask induction was significantly different among groups (P = 0.001; Table 2). Children in group V were more cooperative during mask induction than children in the other 2 groups (P = 0.0005 versus group P and 0.001 versus group VP). ICC scores were found to be significantly correlated with mYPAS scores at each time point (P < 0.001, r = 0.338, 0.531, and 0.869 at T0, T1, and T2, respectively) and with the amount of mYPAS score change (P = 0.042, r = 0.199 from T0 to T1; P < 0.001, r = 0.702 from T0 to T2).
Parent anxiety was assessed using STAI before intervention and after completing anesthesia induction in all groups. Both trait and state anxiety scores in the preoperative holding area and changes in state and anxiety scores over the peri-induction period were not different in the 3 groups (Table 2). Parent state anxiety score changes were found to be weakly correlated with the mYPAS score changes from T0 to T2 (P = 0.025, r = 0.221) and with ICC scores at mask induction (P = 0.035, r = 0.207). However, parent trait anxiety scores were not found to affect children’s anxiety scores during the perioperative period. The majority of parents (75%) stated that they would prefer to be present during anesthesia induction in the future if their child had to undergo surgery. However, a significant intergroup difference was found in this respect (P < 0.001), and fewer parents of group V children (39.1%) favored parental presence at the induction of anesthesia for any future surgery than parents of group P (95.8%, P < 0.001) or group VP (86.2%, P < 0.001) children.
Emergence statuses were comparable except for pain scores among groups (P = 0.041). Postoperative pain scores were weakly correlated with changes in anxiety scores among children between T0 and T2 (P = 0.041, r = 0.200). Median PAED scores and incidences of significant emergence delirium were comparable in the 3 groups and were not linked to the anxiety levels of children or parents at any of the 3 time points (Table 4). Number of children who developed new-onset negative behavior over the 2 weeks after surgery were comparable in all groups. Eating disturbance (31.7%), separation anxiety (14.9%), and aggression toward authority (13.9%) were common on the first postoperative day but decreased significantly with time over the next 2 weeks (7.0%, P < 0.001, 7.0%, P = 0.02 and 8.0%, P = 0.07, respectively). The incidence of newly developed negative behavior was not found to be related to the anxiety levels of children or parents, postoperative pain scores, or the number of children who experienced emergence delirium in the PACU.
In the present study, video distraction, parental presence, or a combination of both had a similar effect on preoperative anxiety during inhaled induction of anesthesia in preschool children undergoing surgery. We found that the overall changes in anxiety levels from preoperative holding area to induction of anesthesia were not different among the 3 groups although children with video distraction had lower anxiety levels compared with those with parental presence only or their combination at entry to the OR and during induction of anesthesia.
Our results suggest that video distraction and parental presence appeared to have different anxiolytic mechanisms in the perioperative setting. Video distraction makes children oblivious to the unfamiliar OR environment and absorbs them in a familiar imaginary world, whereas parental presence simply relieves the distress associated with separation from parents. Previous studies demonstrated that the addition of viewing age-appropriate video provided greater reduction of anxiety than control or conventional distraction techniques in children accompanied by their parents during induction of general anesthesia.11,20 However, the changes in anxiety levels from holding area to anesthetic induction were similar not only between parental presence and video distraction, but also between each single intervention and combination of both interventions in the present study. This inconsistency in the results may be explained by different study designs. Allowing that parental presence and type of anesthetic induction were different. Mifflin et al.11 demonstrated that video distraction more effectively reduced preoperative anxiety compared with control during inhaled induction of anesthesia in children who had parents absent. However, Lee et al.20 demonstrated that animated cartoon distraction produced a greater reduction of anxiety compared with control or toy distraction during IV induction of anesthesia in children who had parental presence and an IV cannula in situ. In addition, both previous studies compared the change in anxiety levels from holding area to induction by subtracting holding area mYPAS from induction mYPAS to determine the anxiolytic effect of each intervention. In this study, the anxiety levels were significantly different at each time point after intervention, but the changes in anxiety levels through 3 different time points (from holding area to induction) were not different among groups. In addition, the proportions of children who had increased anxiety from baseline to induction of anesthesia were similar in all 3 groups although children had increased anxiety levels from baseline to transport in the video distraction group compared with the parental presence only group. Our findings indicate that by diverting a child’s attention, audiovisual distraction is more effective in alleviating anxiety from the stress of separation from parents, but not during induction of anesthesia, than parental presence. Also parental presence does not seem to augment the anxiolytic efficacy of video distraction in children during transport and induction of anesthesia. Thus, each intervention or a combination of both interventions may result in similar effects on preoperative anxiety in children undergoing inhaled induction of anesthesia.
The similar changes in anxiety levels from baseline to induction among the 3 interventions in the present study suggest 2 interesting possibilities. First, contrary to the general belief, separation from parents may not be the most important cause of preoperative anxiety in preschool children. Although children accompanied by their parents did not experience separation anxiety, their changes in anxiety levels until induction of anesthesia were similar to children with video distraction (parental absence) in this study. In fact, parental presence was shown to be briefly effective in reducing a child’s anxiety only at separation from parents but not at induction of anesthesia.21 Our data are consistent with previous reports that placement of a mask for anesthetic induction caused the greatest distress to children undergoing surgery.5,6,22 Next, the anxiety levels at the separation time point (transport to the OR) were lower in children with video distraction than parental presence only or a combination of both despite similar changes in anxiety levels over time. In addition, the proportion of children who had increased anxiety levels from baseline to OR entry was higher in children with parental presence than video distraction. Our data suggest that parental presence is unlikely to be a more effective intervention to reduce separation anxiety than video distraction even in preschool children at greatest risk of developing a separation anxiety reaction.3 Lee et al.20 demonstrated that, in preschool children accompanied by their parents, the cartoon distraction group showed less change in anxiety levels at separation from parents compared with a control group. In contrast, the addition of video distraction did not provide additional benefit in reducing separation anxiety in children with parental presence in this study.
Increased parental anxiety can increase child anxiety and prolong anesthetic induction by generating interactions between children and parents.23,24 We found that a change in parent situational anxiety was influenced by a change in child anxiety or compliance at anesthetic induction and vice versa. Although no significant differences in parental anxiety change were found with respect to intervention, a few parents in both groups that had a parent present (group P and VP) left the OR in tears. However, no parent in the video distraction group showed an emotional reaction at separation. In this study, the number of parents who reported their presence helped their child during transport to the OR and induction of anesthesia and would be present during the induction of anesthesia if required in the future was significantly higher in both parental presence groups than in the video distraction group. These findings suggest that parental anxiety interacts with child anxiety during induction of anesthesia and that a more objective instrument may be required to measure parental anxiety.
Although the pathogeneses of postoperative emergence delirium and negative behavioral changes remained undefined, preschool children, sevoflurane anesthesia, and high anxiety levels in the preoperative holding area and at induction of anesthesia are considered potential risk factors.6,7,22 This means that postoperative emergence delirium and negative behavioral change might be reduced by a preoperative intervention targeting anxiety reduction. The addition of active distraction with a handheld video game effectively reduced the change of anxiety from holding area to mask induction of anesthesia but did not improve postoperative behavioral change compared with children accompanied by their parents.10 In this study, emergence delirium occurring within the first 30 minutes after anesthesia occurred similarly among the 3 groups and largely resolved in 10 to 20 minutes. New-onset negative behavior occurred in 49% of children on the first day after surgery and persisted for 2 weeks after surgery in 14%.
Several limitations related to this study should be discussed. First, parental anxiety was assessed using a self-reporting rating scale. Although the state-trait anxiety inventory is a validated anxiety assessment instrument for adults, we found some discrepancies between subjective reports and objective behaviors. Second, we did not measure the baseline temperament of children using a validated behavioral assessment tool, and baseline temperament characteristics can affect the effectiveness of an anxiolytic intervention by influencing how a child will respond emotionally in a stressful situation. Third, blinding was impossible in this study because video watching and parental presence were visible to investigators and participants, and thus, observer bias may have influenced assessments of anxiety levels and compliance at induction of anesthesia. Fourth, we were unable to calculate the use of parents’ item of the mYPAS accurately because parental presence was lacking in group V. Although we matched children’s responses in group V with the components of the use of parents, this may have affected the psychometric integrity of the mYPAS. Finally, the inability to relate the anxiolytic effects of video distraction and parental presence on the short- and long-term postoperative behavioral outcomes in children may be related to sample size. We calculated sample size based on a change in anxiety levels from baseline to induction of anesthesia, the primary end point of this study, and thus, the number of children recruited may have been insufficient to detect the effects of the 3 different interventions on postoperative behavioral changes.
In conclusion, we found that video distraction, parental presence, or combination of both interventions had a similar effect on preoperative anxiety during inhaled induction of anesthesia and postoperative behavioral outcomes such as emergence delirium and new-onset negative behavioral changes in preschool children. A further large-scale study is required to determine the ability of video distraction to improve postoperative behavioral outcomes.
Name: Hyuckgoo Kim, MD.
Contribution: This author helped design and conduct the study, acquire the data, review and analyze the data, and draft and revise the manuscript.
Attestation: Hyuckgoo Kim has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Sung Mee Jung, MD.
Contribution: This author helped design and conduct the study, acquire data, analyze and interpret the data, draft and revise the manuscript, and is the corresponding author.
Attestation: Sung Mee Jung has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the archival author.
Name: Hwarim Yu, MD.
Contribution: This author helped design and conduct the study, acquire the data, and prepare the manuscript.
Attestation: Hwarim Yu has seen the original study data and approved the final manuscript.
Name: Sang-Jin Park, MD, PhD.
Contribution: This author helped design the study, analyze and interpret the data, and revise the data.
Attestation: Sang-Jin Park has seen the original study data, analyzed and interpreted the data, and approved the final manuscript.
This manuscript was handled by: James A. DiNardo, MD.
The authors thank Ji Eun Jang, Department of Statistics, Yeungnam University, for assistance with statistical analysis.
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, 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
3. Vetter TR. The epidemiology and selective identification of children at risk for preoperative anxiety reactions. Anesth Analg. 1993;77:96–9
4. Przybylo HJ, Tarbell SE, Stevenson GW. Mask fear in children presenting for anesthesia: aversion, phobia, or both? Paediatr Anaesth. 2005;15:366–70
5. Fortier MA, Del Rosario AM, Martin SR, Kain ZN. Perioperative anxiety in children. Paediatr Anaesth. 2010;20:318–22
6. Kain ZN, Caldwell-Andrews AA, Maranets I, McClain B, Gaal D, Mayes LC, Feng R, Zhang H. Preoperative anxiety and emergence delirium and postoperative maladaptive behaviors. Anesth Analg. 2004;99:1648–54
7. 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
8. Low DK, Pittaway AP. The ‘iPhone’ induction—a novel use for the Apple iPhone. Paediatr Anaesth. 2008;18:573–4
9. Burk CJ, Benjamin LT, Connelly EA. Distraction anesthesia for pediatric dermatology procedures. Pediatr Dermatol. 2007;24:419–20
10. 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
11. Mifflin KA, Hackmann T, Chorney JM. Streamed video clips to reduce anxiety in children during inhaled induction of anesthesia. Anesth Analg. 2012;115:1162–7
12. 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
13. Kain ZN, Mayes LC, Wang SM, Caramico LA, Hofstadter MB. Parental presence during induction of anesthesia versus sedative premedication: which intervention is more effective? Anesthesiology. 1998;89:1147–56
14. Sadhasivam S, Cohen LL, Hosu L, Gorman KL, Wang Y, Nick TG, Jou JF, Samol N, Szabova A, Hagerman N, Hein E, Boat A, Varughese A, Kurth CD, Willging JP, Gunter JB. Real-time assessment of perioperative behaviors in children and parents: development and validation of the perioperative adult child behavioral interaction scale. Anesth Analg. 2010;110:1109–15
15. Spielberger CD, Gorsuch RL, Lushene PR, Vagg PR, Jacobs GA Manual for the State-Trait Anxiety Inventory STAI (Form Y) (“Self-Evaluation Questionnaire”). 1983 Palo Alto, CA Consulting Psychologists Press, Inc.
16. McGrath PJ, Johnson G, Goodman JT, Schillinger J, Dunn J, Chapman J CHEOPS: A Behavioral Scale for Rating Postoperative Pain in Children. 1985 New York, NY Raven Press
17. Sikich N, Lerman J. Development and psychometric evaluation of the Pediatric Anesthesia Emergence Delirium scale. Anesthesiology. 2004;100:1138–45
18. Vernon DT, Schulman JL, Foley JM. Changes in children’s behavior after hospitalization. Some dimensions of response and their correlates. Am J Dis Child. 1966;111:581–93
19. Newcombe RG. Interval estimation for the difference between independent proportions: comparison of eleven methods. Stat Med. 1998;17:873–90
20. 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
21. Wright KD, Stewart SH, Finley GA. When are parents helpful? A randomized clinical trial of the efficacy of parental presence for pediatric anesthesia. Can J Anaesth. 2010;57:751–8
22. Kain ZN, Wang SM, Mayes LC, Caramico LA, Hofstadter MB. Distress during the induction of anesthesia and postoperative behavioral outcomes. Anesth Analg. 1999;88:1042–7
23. Kain ZN, Caldwell-Andrews AA, Maranets I, Nelson W, Mayes LC. Predicting which child-parent pair will benefit from parental presence during induction of anesthesia: a decision-making approach. Anesth Analg. 2006;102:81–4
© 2015 International Anesthesia Research Society
24. 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