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Pediatric Anesthesiology: Original Clinical Research Report

Clinical Use of the Pictorial Baxter Retching Faces Scale for the Measurement of Postoperative Nausea in Children

Watcha, Mehernoor F. MD*,†; Lee, Andrew D. MPH†; Medellin, Eduardo BS†; Felberg, M. Toni MD*,†; Bidani, Sudha A. MD*,†

Author Information

From the *Department of Anesthesiology, Perioperative and Pain Medicine, Texas Children’s Hospital, Houston, Texas

†Department of Anesthesiology, Baylor College of Medicine, Houston, Texas.

Published ahead of print 12 October 2018.

Accepted for publication September 5, 2018.

Funding: This work was supported by internal funding from the Department of Anesthesiology, Perioperative and Pain Medicine, Texas Children’s Hospital, Houston, TX, and Baylor College of Medicine, Houston, TX.

The authors declare no conflicts of interest.

Clinical trials registration: The trial was registered before patient enrollment at clinicaltrials.gov (NCT 02421952, principal investigator: S.A.B.; date of registration: April 21, 2015).

Reprints will not be available from the authors.

Address correspondence to Mehernoor F. Watcha, MD, Department of Anesthesiology, Perioperative and Pain Medicine, Texas Children’s Hospital, 6621 Fannin St, Suite A 3300, Houston, TX 77030. Address e-mail to [email protected].

doi: 10.1213/ANE.0000000000003850
  • Free

Abstract

KEY POINTS

  • Question: What are the age limitations, reliability, and utility of the pictorial Baxter Retching Faces (BARF) scale, a validated self-report instrument to quantify nausea in children, and what is the BARF scale score associated with a child’s identification of a need for rescue antiemetic therapy?
  • Findings: The pictorial BARF scale is easy to use in the clinical setting in children ≥6 years of age, identifies those with nausea, and has a minimum clinically relevant difference of approximately 1 face, with a score >4 associated with a patient’s need for therapy and a point estimate consistent with moderate test–retest reliability.
  • Meaning: The BARF scale can be used in the clinical setting to identify children having nausea with or without vomiting, including those with nausea scores above the patient-perceived threshold for rescue antiemetic therapy.

Postoperative nausea and vomiting (PONV) occurs frequently in patients receiving general anesthesia for surgical procedures, with a higher incidence of postoperative vomiting reported in children compared to adults.1–4 In adults, the visual analog scale (VAS) is an accurate instrument to quantify the intensity of subjective symptoms such as pain and nausea,5 but its sensitivity and reliability may be limited in younger children.6–8 By default, vomiting is used as the objective clinical end point in the management of PONV in children.4 However, nausea occurs more frequently than vomiting, and failure to measure the severity of pediatric nausea may result in its undertreatment, similar to the earlier undertreatment of pediatric pain.1,3,9–11

F1
Figure 1.:
BARF scale. Script for BARF scale: “Have you thrown up or felt like you were going to throw up before? How did your tummy feel then? We call that feeling of being sick to the stomach nausea. These faces show children who feel no nausea at all, who feel a little bit nauseated, who feel even more nauseated, and these are children who have the most nausea it is possible to feel.” (Point to each face at the appropriate time.) “Which face is more like you feel right now?” Reproduced with permission from Pediatrics, Vol. 127, e1542–e1549, Copyright © 2011 by the AAP.12 BARF indicates Baxter Retching Faces.

Recently, a pictorial scale for measuring nausea, the Baxter Retching Faces (BARF) scale, has been developed (Figure 1).12 It has 6 faces with assigned scores ranging from 0 to 10 with a score difference of 2 between each face. The BARF scale has been shown to have construct, content, and convergent validity as an instrument to measure the severity of nausea in children.12 However, important psychometric properties aspects of the BARF scale were not examined in the initial validation study and need to be established before it can be used clinically in the management of postoperative and postdischarge nausea in children. The primary aims of this study were to determine these properties of the BARF scale, including (1) the lowest age at which children can use the BARF score reliably; (2) the score associated with a patient’s perceived need for antiemetic treatment; (3) the minimum change in the scores of clinical relevance; and (4) the test–retest reliability. The secondary aim was to examine the utility of the BARF scale in the clinical setting.

METHODS

This study was approved by the institutional review board of the Baylor College of Medicine (H-32386), and written informed consent was obtained from all parents/legal guardians of subjects along with age-appropriate assent of subjects. The trial was registered before patient enrollment at clinicaltrials.gov (NCT 02421952, principal investigator: S.A.B., MD; date of registration: April 21, 2015). The study design was based on the initial validation study and on previous pediatric pain studies.10,12–15 Healthy English-speaking children scheduled for elective ambulatory surgery were recruited if they were between 3 and 18 years of age and were free from major concurrent disorders including nausea and/or vomiting in the previous 24 hours. We excluded children with developmental delay, blindness, impaired cognitive, visual, hearing, or communicative skills, or undergoing procedures that may have resulted in diminished hearing or vision in the postoperative period. After obtaining consent, we instructed each child to perform a seriation task in which we presented 6 cutout shapes of different sizes and asked the subject to first choose the largest size, then the smallest, then the largest remaining size until no more shapes were left.8,16 Children who passed the seriation screening test were asked to provide baseline assessments of pain and nausea on both the VAS and a pictorial scale (Faces Pain Scale-Revised for pain and BARF for nausea).12,14 The script for the scales was standardized in keeping with previous studies, and the investigator assessed each child’s ability to understand the instructions and provide reliable responses.7,17 The order of presentation of scales was randomized to reduce the potential for an order effect, in which the patient’s response on one scale may influence the response on other scales.12 We considered a child to have reliable ability to use the BARF score if he or she fulfilled all of these criteria: (1) completion of the seriation test; (2) the investigator assessed that the child could understand the instructions provided in the script for the various scores; and (3) the child cooperated to provide baseline and postoperative scores when asked.

The choice of anesthetic techniques, monitoring and perioperative management, and drugs including preoperative anxiolytics, antiemetics for prophylaxis and rescue therapy, supplemental, and rescue analgesics, was not changed for the purposes of the study but determined by the attending anesthesiologist on the clinical needs and evidence-based institutional practices. After the children were awake and responded to commands in the postanesthesia care unit (PACU), they were asked to rate their pain and nausea using the same scales in the same order as in the preoperative area. This was repeated immediately before and 30–60 minutes after receiving rescue analgesic or antiemetic drug treatment. In addition, patients rated changes in nausea on a 5-point Likert scale as follows: (1) much worse than before; (2) a little worse than before; (3) the same as before; (4) a little better than before; or (5) much better than before. At these time points, patients were also asked if they felt a need for treatment of their nausea (response recorded as yes or no).

Patients were discharged from the PACU when they achieved institutional discharge criteria. The parents were given a diary to record the maximum nausea on the VAS and BARF scales during the first 24 postoperative hours and were asked to mail it back in a stamped envelope. One of 2 investigators (A.D.L. or E.M.) contacted each child’s caretaker by phone 24 hours after surgery to determine whether the child had any nausea or vomiting, which medications were given after discharge, and to remind the child’s caretaker to mail the diary.

Statistical Analysis

Children with higher peak nausea scores on the BARF scale in the postoperative period compared to their baseline preoperative values were considered to have postoperative nausea, with scores >6 considered to represent severe nausea.18 Emesis was defined as forceful ejection of stomach contents and included retching in which expulsive efforts occur without ejection of stomach contents. Patients with ≥3 episodes of emesis were considered to have severe vomiting.1 For the age-related ability to use the BARF scale, we grouped patients into 7 separate age groups: 3, 4, 5, 6, 7, 8 to <12 years, and ≥12 to <18 years. Data are presented as mean (standard deviation) and counts (percentages) and analyzed using SAS (SAS Institute, Cary, NC) version 9.4. For tests with paired data, comparisons were limited to the first available paired scores to avoid using scores from the same patient twice.

The statistical methodology for various specific questions in the study was based on previously published adult PONV and pediatric pain studies with a similar design.19–22 These included the following:

  1. The age-related ability to use the BARF scale was determined by constructing receiver operating characteristic (ROC) curves and calculating the area under the ROC curve and the 95% confidence interval (CI), along with sensitivity and specificity (Table 1).8,16 We determined the lowest age at or above which all children were able to use the BARF scale (ie, specificity was 100%). A 1-sided Fisher exact test was used to compare the number of children below and above this cutoff age who could or could not use the BARF scale. One-sided tests were considered acceptable because it was implausible that older children would be less able to use the BARF scale than younger children.
  2. The score on the BARF scale associated with a patient-perceived need for rescue therapy was examined by ROC curves, and the area under the curve (AUC)–ROC and 95% CIs were calculated, along with the sensitivity, specificity, and Youden index at various BARF score cutoff points. Sensitivity and specificity were considered equally important, and the cutoff point to generate the best combination of sensitivity and specificity was determined.19,22
  3. The minimum clinically relevant change in BARF and VAS scores for nausea was defined as the absolute change in paired scores for nausea in a group of children who rated their nausea to be “a little better than before” or “a little worse than before.”19,22
  4. The test–retest reliability used paired scores for which subjects stated that there was no change in nausea (Likert rating of “the same as before”). We determined the intraclass correlation coefficient (ICC) using a 2-way random-effects analysis of variance model for single rater absolute agreement (Shrout and Fleiss23 convention ICC [2, 1]).
T1
Table 1.:
Age-Related Ability to Use the BARF Scale

All tests were 2-sided unless otherwise stated, and P values of <.05 were considered statistically significant.

Sample Size.

The study had a number of aims, and the sample size was chosen so that each aim could be achieved with a minimum of 80% power at the .05 level of significance.

  1. The sample size for the age-related ability to use the BARF scale was based on a previously published study of the age-related ability to use the Faces Pain scale in which 95% of children ≥6 years of age passed the cup screening test used in our study, but only 65% of the younger children could.8 We assumed that the ability to use the BARF scale would be similar to the ability to use the Faces Pain scale. We estimated that a minimum sample size of 21 per group would be required to detect the aforementioned difference between 95% and 65% for a 1-sided α of .05 with a power of 80%.8 We set a recruitment target of 21 in each of the 7 age groups of 3, 4, 5, 6, and 7 years and for age groups 8 to <12 years and ≥12 to <18 years (total = 147).
  2. We could not find published data on the change in paired BARF scores in children who rated their nausea as a little better or a little worse for sample size calculations for the minimum clinically relevant difference in BARF scores. We therefore based the sample size on data in an adult study of the minimum clinically relevant difference in VAS scores for nausea.18 Assuming a mean difference of 0.47 with a standard deviation of 0.93 (based on this study), a sample size of 34 would be required for the desired α (.05) and power (80%).
  3. For the test–retest reliability, it was calculated that a minimum sample size of 48 subjects who rated their nausea as unchanged at 2 time points would produce a 2-sided 95% CI with a width of 0.3 when the estimated intraclass correlation was 0.7.24

RESULTS

A total of 330 patients were assessed for eligibility, with 102 judged ineligible and 20 who declined to participate (Figure 2). The remaining 208 were screened for the ability to use the VAS and BARF scales. Thirteen children failed the seriation task, and 2 who completed this task were uncooperative for baseline BARF and VAS assessments (Table 1). These 15 subjects were judged unable to use the scales and were excluded from analysis of end points other than the age-related ability to use the BARF score. Data from the remaining subjects were used to determine the end points of the minimum clinically relevant difference in scores and the test–retest reliability, after excluding patients for reasons provided in Figure 2.

F2
Figure 2.:
Patient flow diagram. PACU indicates postanesthesia care unit; VAS, visual analog scale.

All children ≥6 years of age were judged able to use the BARF scale and did provide these scores for both baseline and postoperative time periods, while 15 of 76 (19.7%; 95% CI, 11.5%–30.5%) <6 years of age were judged unable to use the scale because they failed the screening serration test, did not understand instructions, or did not cooperate to provide baseline scores (Table 1). Another 2 subjects <6 years of age provided baseline scores but developed pain or emergence-related maladaptive behavior in the PACU and were uncooperative in providing postoperative scores. A total of 17 of 76 (22.4%; 95% CI, 13.6%–33.4%) children <6 years of age were therefore considered unable to use the BARF scale.

The AUC of the ROC for age-related ability to use the BARF scale was 0.903 (95% CI, 0.86–0.95). Specificity increased with age until it reached 100% at 6 years of age (Table 1). Although some children <6 years of age could provide BARF scores, reliable and consistent ability to use these instruments was very significantly greater in those ≥6 years of age (132/132 [100%] vs 59/76 [77.6%] for children ≥6 and <6 years of age, respectively, Fisher exact test, P < .001).

The ROC curve for BARF scores and a patient-perceived need for antiemetic therapy had an AUC of 0.858 (95% CI, 0.733–0.983). A cutoff point of 4 on the BARF scale had a sensitivity of 0.80 (95% CI, 0.44–0.96) and specificity of 0.85 (95% CI, 0.79–0.90), with a Youden index of 0.66 for the perceived need for antiemetic therapy. In comparison, a cutoff score of 6 had decreased sensitivity to 0.40 (95% CI, 0.14–0.73), an increased specificity to 0.93 (95% CI, 0.88%–0.96%), and a Youden index of 0.33. A cutoff score of ≥2 had a higher sensitivity of 0.9 (95% CI, 0.54–0.99) but a lower specificity of 0.67 (95% CI, 0.59–0.73), and a Youden index of 0.57. We conclude that the threshold scores of 4 have the best-combined level of sensitivity and specificity for clinical purposes.

The minimum clinically relevant change in 34 paired observations of the BARF score in 34 children who rated their nausea as a little better than before or a little worse than before was 1.47 (SD = 1.86, 95% CI, 0.84–2.1). This is approximately 1 face difference.

In 41 subjects who rated their nausea as same as before, the ICC (2, 1) for test–retest reliability was 0.56 (95% CI, 0.34–0.73).

We also examined the incidence of PONV and postdischarge nausea or vomiting (PDNV) in the subjects (Tables 2 and 3). In the PACU, postoperative nausea or emesis occurred in 62 (32.1%) patients; both symptoms occurred in 6 (3.1%). Of the 60 (31.1%) patients with nausea, severe nausea (score >6) was noted in 13 (6.7%); 2 reporting severe nausea also had vomiting. Emesis occurred in 8 (4.1%) with severe emesis in 2 (1%). Rescue antiemetics were administered to 16 (8.3%), including both cases with severe emesis. However, rescue antiemetics were administered to only 2 of 11 (18.2%) children who had severe nausea without emesis (Figure 3).

T2
Table 2.:
Number of Patients With Nausea, Emesis, Severe Nausea, Severe Emesis, and Number Receiving Rescue Antiemetics in the PACU
F3
Figure 3.:
Number (percentage) of patients who received rescue antiemetic therapy in the PACU for severe nausea and/or severe vomiting. PACU indicates postanesthesia care unit.
T3
Table 3.:
The Incidence of Postdischarge Nausea, Emesis, Severe Nausea, Severe Emesis, and Number Receiving Rescue Antiemetics in Subjects Who Returned the Diary

Only 99 of 192 (52.1%) diaries were returned by parents (Table 3). The incidence of PDNV was 39 (39.4%), with nausea scores above baseline preoperative values reported in 34 (34.3%), emesis in 16 (16.2%), and rescue antiemetics given to 8 (8.1%). Severe nausea was noted in 15 (15.2%) and severe vomiting in 3 (3.03%). Only 21 of the 39 (53.8%) patients who reported PDNV symptoms had these symptoms while in the PACU. Similarly, 19 of 34 (55.8%) patients with any postdischarge nausea had nausea in the PACU, while only 2 of 16 (12.5%) with postdischarge emesis had vomiting in the PACU. Seven of the 16 (43.8%) patients with severe postdischarge nausea had some nausea in the PACU with 2 (12.5%) having severe nausea.

DISCUSSION

This study has shown that the pictorial BARF instrument can be used by children ≥6 years of age to quantify their nausea and that the minimum clinically relevant change in the subjective symptom was 1.47 (approximately 1 face). Pictorial presentation of scale items may increase item comprehensibility, sustain the child’s attention, and provide better responses than verbal or numeric scales.25 The BARF scale is inexpensive, simple to reproduce for clinical use, easily understood, and quickly completed by children ≥6 years of age. However, as with all instruments, the BARF scale needs to be administered by trained personnel in a standardized fashion.25,26 The pictorial BARF and Faces Pain Scale-Revised scales have been successfully used in our study in the stressful situation of a child undergoing surgery and may also be useful in other clinical situations including children receiving chemotherapy and those with gastrointestinal symptoms.

Our study findings have a number of clinical implications. We have shown that children feel that they should receive antiemetics if they have a BARF score >4, which is in keeping with the critical threshold of 4 on the VAS scale that would trigger rescue antiemetic therapy in adults.19,27,28 However, it is not a common practice to measure nausea in children or to make decisions on treating even severe pediatric postoperative nausea unless it is accompanied by emesis.4 In contrast, large-scale adult studies have shown that rescue antiemetics are given more often for managing nausea than for emesis.1,5,27 For example, in a recent multicenter study, rescue antiemetics were administered to 518 of 1147 (45.2%) high-risk adults although, only 294 (25.6%) had vomiting.28 Dewinter et al5 reported that after a 2 or 3 drug prophylactic regimen for PONV in adults, 15% required rescue antiemetics, although only 3% had emesis, indicating that the remaining patients received it for intractable nausea. In our study, <20% of children with severe nausea without emesis received rescue antiemetics, while all children with severe vomiting in the PACU did. Adults may be more likely to make spontaneous requests for rescue antiemetics after surgery, while children may be unaware that they can request medications or are reluctant to make such requests out of fears of needle pain from injections.

In our pediatric study, experienced PACU nurses administered rescue antiemetics to fewer children than those who rated their nausea at or above the threshold level for patient-perceived need for therapy. Similar differences in patient and health care provider assessments of the need for rescue medications have been reported for other subjective symptoms such as pain.26 Additional studies are required to test the hypothesis that measuring the severity of pediatric nausea and treating the condition before vomiting occurs will improve the postoperative experience and quality of recovery.

Our study also showed that as in adults, PDNV can occur in patients who did not develop these symptoms in the immediate recovery phase in the PACU.1,2 While it is routine practice to discharge pediatric ambulatory surgery patients with a prescription for analgesics, it is not routine to supply all patients with antiemetics for use after discharge. Parental failure to contact physicians for antiemetic therapy may explain why some patients with severe nausea or vomiting after discharge did not receive antiemetics. However, half of the patients in our study did not return the diaries and it is reasonable to assume many of them would not have PDNV, leading to a considerable wastage of drugs if all patients were discharged with a supply of antiemetics.

This study has a number of limitations including the failure of almost half the subjects to return diaries. One of the other limitations is that this was a single-center study performed in English-speaking subjects undergoing ambulatory surgery. The BARF scale requires validation in other languages and patient populations from different medical centers to demonstrate generalizability of the scale. We have also shown that children who rate their nausea as above the threshold for patient-perceived need for rescue antiemetic therapy do not always receive medications even when they are receiving care from experienced pediatric PACU nurses. We did not determine the threshold BARF scores associated with a nurse-perceived need for rescue antiemetics.

Another limitation of the study was that the point estimate for the ICC suggested only moderate agreement for the test–retest reliability with a wide 95% CI. This may reflect the fact that we had fewer patients rating their nausea as unchanged at 2 time points in the PACU than required by the sample size calculations for test–retest reliability. This may be because many subjects received postoperative opioids, which are known to be associated with nausea. It may be necessary to study test–retest reliability in a pediatric patient population not likely to receive opioids after anesthesia (eg, nonpainful magnetic resonance imaging or other radiological procedures).

Kapur29 in an editorial published 27 years ago called PONV the “big little problem” of anesthesia, suggesting that although patients and parents consider this as one of the most undesirable outcomes of surgery, anesthesiologists pay less attention to this complication compared to providing pain relief. Pediatric patients have more frequent postoperative vomiting than adults, and our study has shown that the incidence of PONV and PDNV is higher than the incidence of postoperative vomiting alone. Current practices of limiting rescue therapy to those children with vomiting may result in undertreatment of distressing symptoms of nausea in the pediatric population. It is therefore possible that the big little problem may be even bigger in the littler patients.

In summary, this study has shown that the pictorial BARF scale can be used in clinical practice to measure the severity of postoperative and postdischarge nausea. We concluded that (1) the lowest age associated with consistently reliable use was 6 years; (2) scores ≥4 were associated with patient-perceived need for antiemetics; (3) the minimum clinically relevant difference was approximately 1 face; and (4) the ICC point estimate for test–retest reliability suggested moderate agreement but with wide 95% CI.

ACKNOWLEDGMENTS

We thank the nurses and physicians at Texas Children’s Hospital for their help in conducting and completing the study. We are grateful to the children and their parents/guardians for participating in the study. We also acknowledge and thank Teniola Shittu, Department of Anesthesiology, Perioperative and Pain Medicine Surgery, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, for advice regarding the statistical analysis.

DISCLOSURES

Name: Mehernoor F. Watcha, MD.

Contribution: This author helped design the study, supervise the patient recruitment, collect and analyze the data, write the manuscript, and approve the final version.

Name: Andrew D. Lee, MPH.

Contribution: This author helped recruit the patients for the study, collect and analyze the data, write the manuscript, and approve the final version.

Name: Eduardo Medellin, BS.

Contribution: This author helped recruit the patients for the study, collect and analyze the data, write the manuscript, and approve the final version.

Name: M. Toni Felberg, MD.

Contribution: This author helped supervise the patient recruitment, collect the data, write the manuscript, and approve the final version.

Name: Sudha A. Bidani, MD.

Contribution: This author helped supervise the patient recruitment, collect the data, write the manuscript, and approve the final version.

This manuscript was handled by: James A. DiNardo, MD, FAAP.

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