The purpose of this study was to describe the physiological and behavioral responses of the preterm neonate to the acute pain stimulus of a heel stick. The specific aim was to compare responses of the preterm neonate to a nociceptive versus a non-nociceptive stimulus. A true experimental, repeated measures, cross-over design was used to test the hypothesis that preterm neonates undergoing heel warming/heel stick would have higher mean heart rates, respiratory rates, arterial blood pressures, lower mean SpO$\sb2$ values, and a differing pattern of behavioral states, when compared to those receiving heel warming only. Gestational age was included as a covariate in the design.
A convenience sample of 58 preterm neonates was obtained from two urban, level III, neonatal intensive care units in a major metropolitan area. All subjects were 30-37 weeks gestational age, less than 96 hours of age, and, based on mothers' report, free from narcotics prenatally and postnatally. Neonates were randomly assigned to groups which differed in order of treatment.
The neonates were videotaped while receiving two treatments: a 5-minute heel warming/heel stick for a blood draw, and a 5-minute heel warming only treatment. Observations were at baseline and three two-minute observation periods after each treatment. Physiological data were collected electronically. Behavioral states were scored using the Assessment of Preterm Infant Behavior State System Subscale.
Analysis showed a significant difference between the two treatments for heart rate (F = 8.36, p =.0008) and SpO$\sb2$ (F = 21.0, p =.0001). There was no effect for order of treatment. Gestational age did not impact the physiological outcome variables. State behaviors demonstrated different patterns between treatments in the first observation period. However, with age controlled, only infants in the 33-34 week age group had significant differences in patterns of state behavior. Severity of illness did not affect any of the dependent variables. Interrater reliability was excellent. Recommendations include the use of multidimensional pain assessment instruments in the clinical arena and aggressive pain identification and management.