The behavioral pain response to heelstick in preterm neonates studied longitudinally: description, development, determinants, and components.

OBJECTIVES: Preterm infants often experience multiple painful procedures during their stay in neonatal intensive care units (NICUs). The objectives of this study were to evaluate behavioral responses to heelstick in preterm newborns, characterize developmental changes and the effects of other demographic and clinical variables on the pain response, and estimate the contributions of individual Neonatal Infant Pain Scale (NIPS) behaviors to the summary pain score.
METHODS: A longitudinal study was conducted to evaluate the behavioral responses of 35 preterm newborns to multiple heelstick procedures during their stay in the NICU. Sixty-one video recordings of blood collection by heel lance were evaluated for behavioral pain response using the NIPS. Generalized linear mixed models were calculated to address the study objectives.
RESULTS: The increases in NIPS scores from the baseline to the blood draw were highly significant (mean baseline score=3.34, mean blood draw score=5.45, p<0.001). The newborns' pain responses increased an average of 0.23 points on the NIPS scale each week (p=0.002). Lower NIPS scores during the heelstick procedure were associated with four clinical variables: younger post-menstrual age at birth, lower birthweight, mechanical ventilation, and longer length of stay in the NICU. Crying, arousal state, and facial grimace contributed more than 85% of the increase in NIPS scores during the heelstick procedure. DISCUSSION: While behavioral responses to pain are attenuated in young, severely ill preterm newborns, they can be reliably detected. The most robust pain behaviors are crying, changes in arousal state, and facial grimacing.