Differences Related to Age, Gender, and Previous Surgery
The relationships between underlying patient factors— including sex, age, and previous surgical experience—and pain scores related to the other outcomes (i.e., PNM, PR, PS) are presented in Table 2. Females, children who had no previous surgical experience, and those who were older reported satisfaction (somewhat to very satisfied) at higher pain scores than did other children.
This study is the first to evaluate the relationship between NRS pain scores and several verbal outcome measures in children. These data demonstrate that 0 to 10 NRS scores in children are, in general, reliably associated with the child's PNM, perceived PR, and PS with treatment, supporting use of the NRS as a measure of pain intensity in clinical and research settings. Importantly, the large overlap in scores associated with these outcomes, and the number of false negatives and positives, suggest that application of cutoff scores for individual treatment decisions is inappropriate for children.
The notion of using pain score thresholds for treatment or rescue decisions has been suggested in clinical and research settings,23,24 yet previous studies have demonstrated significant variability in individual thresholds.5,6,13 Blumstein and Moore described poor sensitivity and specificity for the VAS in predicting the need for analgesia for adults in the emergency room.5 Gauthier et al. showed a significant overlap in scores related to the child's perceptions of pain severity and thresholds for needing medicine.13 The variability between reported pain scores and individual treatment thresholds in these studies reflects the complexity of the pain experience for children and adults. The need for analgesia is likely dependent on many factors, including perceptions of medicine,13 importance of side effects,25,26 and individual pain temperament or sensitivity.27,28 Although the NRS had a general ability to detect the PNM in the present study sample, the number of false positives and negatives suggests that application of absolute cut-points to treatment decisions for individual patients is inappropriate.
Previous studies have shown that, in general, mean pain score changes of 9 to 13 mm on the VAS or ±1 on the NRS represent the minimum change reflecting the patient's perception of “more” or “less” pain.4,7–9,12,14,29 Powell et al. reported the MCSD on the VAS as 10 mm (CI 7 to12) for children in the emergency room.14 The present study, similar to previous reports, found that a 1-point decrease or increase in NRS score was associated with perceptions of feeling “a little better” or “little worse,” respectively, and that a larger change (median = 2) was needed to impart perceived PR when baseline scores were higher (i.e., >5). This later finding is particularly important when calculating sample sizes and interpreting findings in clinical pain trials. Lastly, as was previously reported,12,30 there were a significant number of children whose perception (feeling better or worse) was in the opposite direction of the change in score, highlighting the complexity of pain assessment for the individual child.
The wide overlap in NRS scores in relation to satisfaction and dissatisfaction further emphasize the complexity of evaluating pain outcomes. Several studies in adults have demonstrated only poor-to-fair relationships between global satisfaction measures and pain intensity.10,11,31–33 Similar to our findings, previous data depict a skewed distribution of satisfaction data, with most patients rating treatments as excellent or good, even those with moderate to severe pain.34,35 Importantly, the relationship between satisfaction and pain intensity may differ on the basis of the timing of assessment postoperatively,11,22 and phrasing of the satisfaction question.10 The present study compared a given pain score and PS with overall treatment at that time, and assessments occurred only during the first 24 hours after surgery. Further study is needed to evaluate the impact of time on this relationship in children. Lastly, although the survey question was phrased to assess satisfaction with treatment, other moderating factors, such as side effects, may have influenced the child's response. Despite ongoing questions related to the relevancy of satisfaction measures, they remain among the recommended outcome measures for acute and chronic pain trials.2
Age, gender, and previous experience modified the relationship between NRS scores and PS but not PNM or PR in this sample. Older children, females, and those without previous experience reported satisfaction at higher NRS scores than did others. These findings reflect potential differences in coping ability, expectations, or anxiety. Indeed, previous investigators have demonstrated a higher pain threshold and differences in coping techniques used by older children during experimental pain situations.36 Others have described long-lasting effects of early (i.e., infancy) injury on somatosensory processing,37 as well as the effect of anxiety and conditioned fear on pain thresholds.38,39 The relationship between gender and perceptions of pain are less clear, given confounding findings in previous studies.13,29,31, 36,40–42 Further study is necessary to better characterize the potential modifying effects of age, gender, and other factors on the pain experience in children.
Because these data were collected at 1 institution in English-speaking children only, the ability to generalize to other pediatric populations may be limited. The method of surveying children may have posed several limitations. Repeat observations were conducted 1 to 2 hours after the initial assessment, which may have influenced the child's perceived PR. The fact that previous reports of the MCSD in pain scores in adults and children have yielded similar findings to ours, however, provides some external validity to our data. Other factors—such as analgesics used, their side effects, anxiety, parental presence, or unknowns—may have modified the child's perceptions. However, the purpose of this study was to determine the clinical meaning of pain scores in a real postoperative setting, and as such, the setting with all of its confounders was highly relevant. Further qualitative study is necessary to better explore the effects of other factors. Lastly, this study may have been underpowered to detect threshold differences in the subgroups.
This study provides new data to describe the relationship between NRS scores and the child's PNM, PR, and PS with treatment. Although findings support the use of the NRS in children ages 7 to 16 years for research and clinical practice, the notable variability between pain scores and other outcomes highlight the importance of individualizing pain assessment, and treatment.
Name: Terri Voepel-Lewis, MS, RN.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: Terri Voepel-Lewis 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: Constance N. Burke, BSN, RN.
Contribution: This author helped conduct the study.
Attestation: Constance N. Burke has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Nicole Jeffreys, MD.
Contribution: This author helped conduct the study.
Attestation: Nicole Jeffreys has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Shobha Malviya, MD.
Contribution: This author helped conduct the study and write the manuscript.
Attestation: Shobha Malviya reviewed the analysis of the data and approved the final manuscript.
Name: Alan R. Tait, PhD.
Contribution: This author helped analyze the data and write the manuscript.
Attestation: Alan R. Tait has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
The authors gratefully acknowledge the contributions of the following persons: Deepa Bhat, Elsa Pechlivanidis, Jennifer Hemberg, Lauren Perlin, and Caela Hesano.
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