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Cry and facial behavior during induced pain in neonates Grunau, Ruth Veronica Elizabeth


Pain behavior of neonates was compared across sleep/waking states and sex. From Gate-Control Theory (Melzack and Wall, 1982) it was hypothesized that pain behavior would vary depending on the ongoing functional state of the infant, in contrast with Specificity Theory (Mountcastle, 1980), from which one would expect neonatal pain expression to be solely a function of degree of tissue damage. The findings of facial action variation across sleep/waking state was interpreted as consistent with Gate-Control Theory. Awake alert infants responded with the most facial activity, which supported Brazelton's (1973) view that infants in this state are most receptive to environmental stimulation. Fundamental frequency of cry was not related to sleep/waking state. This suggested that findings from the cry literature on pain cry as a reflection of nervous system "stress", in unwell newborns, do not generalize directly to healthy infants under varying degrees of stress as a function of state. Sex differences were apparent in speed of response, with boys showing shorter time to cry and facial action following heel-lance. Issues raised by the study include the importance of using measurement techniques which are independent of pre-conceived categories of affective response, and the surprising degree of responsivity of the neonate to ongoing events. Exploratory analyses suggested obstetric factors were related to overall facial action. Caution was expressed in this interpretation due to the great complexity of the inter-relationships of medical, physiological and maternal variables which go far beyond the scope of this study. It was concluded that obstetric features such as mode of delivery should be considered in sample selection for neonatal pain studies, in contrast to current practise which has been to assume healthy newborns form an homogeneous population. It was clear from these findings that the issues are multifaceted, and the optimal way to proceed with research in the area of neonatal pain is with an interdisciplinary team format.

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