Physiologic correlates of comfort in healthy children

Pain assessment is particularly challenging when children are unable or unwilling to provide a self-report. Although clinicians frequently use vital signs as an adjunct to pain assessment, little evidence exists to support this practice. The purpose of this study was to explore the ability of selected physiologic variables (peripheral skin temperature, heart rate, skin conductance activity [SCA], respiratory rate, electromyogram [EMG] of the frontalis and right forearm muscles, and systolic and diastolic blood pressure [BP]) to detect changes in children's autonomic arousal from baseline. A one-group, repeated measures, randomized crossover design guided the study. Chosen from a convenience sample, 100 healthy children (ages 8-17 years) served as their own controls while undergoing two levels of intervention: cold pressor pain and guided imagery. Although most physiologic responses showed changes in the expected direction, EMG, SCA, and heart rate decreased slightly during cold pressor. Few significant intercorrelations were demonstrated among the physiologic variables. SCA, forehead EMG, respiratory rate, systolic and diastolic BP detected significant changes in arousal across measures. Notably, heart rate failed to detect changes for any of the measures. Results emphasize the need for caution in interpreting heart rate as an index of comfort. Further research is needed to examine the effects of clinical pain on physiologic indices and to further examine age and sex influences. To be relevant for assessment of acute established pain, physiologic variables must also be tested for their sensitivity beyond the immediate period of autonomic arousal.