Influence of repeated painful procedures on prefrontal cortical pain responses in newborns

Aim: We examined whether previous experience of repeated skin punctures altered the correlation between prefrontal cortical pain responses and Premature Infant Pain Profile (PIPP) scores, compared with infants who had no experience of skin puncture. Methods: Eighty infants at 37-42 weeks of gestational age were observed during clinically required blood sampling: full-term infants with no experience of painful skin-breaking procedures before data collection (controls; n = 30), full-term infants with the experience of painful skin-breaking procedures (n = 20) and preterm infants with the experience of painful skin-breaking procedures (n = 30). Results: We found no significant differences in PIPP scores among groups. In controls, prefrontal activation in both hemispheres correlated with facial expression score of the PIPP (r = 0.53 for right prefrontal area; r = 0.37 for left prefrontal area) and the total score. In full-term infants with the experience of pain, there was no correlation between cortical activation and clinical pain scores. In preterm infants, prefrontal activation in both hemispheres correlated with the physiological component of the PIPP score (r = 0.36 for right prefrontal area; r = 0.41 for left prefrontal area). Conclusion: Our findings may be useful in considering the effects of cumulative painful experience on emotion and stress in neonates.