Preterm infants' sympathetic arousal and associated behavioral responses to sound stimuli in the neonatal intensive care unit

PURPOSE: To evaluate the utility of skin conductance (SC) as a measure of autonomic arousal to sound stimuli in preterm infants. DESIGN: A pilot cross-sectional, correlations study. SUBJECTS: Eleven preterm infants with a mean gestational age of 31.6 weeks without anomalies or conditions associated with neurodevelopmental delay composed the sample. METHODS: On days 5-7 of life, the following infant responses were simultaneously recorded in response to naturally occurring sound stimuli in the NICU: real-time measurements of heart rate, respiratory rate, and oxygen saturations; sympathetic-mediated sweating via SC; and behavioral responses using the Newborn Individualized Developmental Care and Assessment Program naturalistic observation. Baseline sound levels (BSL, <55 dBA) and high sound levels (HSL, >65 dBA) were measured to index patterns of response during a nonhandling period preceding care. RESULTS: Mean heart rate during precare was directly associated with higher SC increases to sound stimuli (r[10] = 0.697, P=.017). The SC during HSL was significantly higher than that during BSL (P<.0001). Males demonstrated higher SC increases to sound stimuli than females (P =.030). Changes in SC induced by increases in sound intensity were associated with lower attention responses (r[10] = -0.92, P <.0001) and lower summated behavioral responses (r[10] = - 0.59, P=.054). CONCLUSION: SC provides a noninvasive, sensitive measure of sympathetic arousal that may not be apparent in behavioral cues or states, or determined by standard physiological responses alone.