부산대학교 도서관

Both substance P (SP) and neurokinin A (NKA) have been postulated to be involved in persistent pain in adult studies, but never previously researched in newborn infants. Methods of sample handling and analysis were developed to accommodate neonatal microsamples.  Sample extraction was found to be essential, as were speed of sample collection and the use of polypropylene materials during sample handing. The clinical study enrolled 174 infants of different gestational ages, who had serial measurements of SP, NKA, and cortisol performed in plasma and saliva samples. Plasma SP concentrations in neonates ranged from 0.0-11.2 pmol/L (median 1.7 pmol/L) and NKA concentrations from 1.8-74.6 pmol/L (median 6.0 pmol/L). Gestation and birth weight had no significant correlation with peptide concentrations. Postnatally, there was a gradual rise in median plasma SP and NKA during the first three days which decreased again by days 7 to 14. Perinatal factors such as labour, the mode of delivery, and epidural analgesia affected NKA but not SP concentrations. With regard to either pain or assisted ventilation, plasma SP concentrations did not appear to be a useful marker of persistent pain or distress.  Conversely, plasma NKA concentrations showed significant changes with ventilation, which were further modulated by the use of analgesia. Cortisol responses in the same group of infants demonstrated significant changes with ventilation, but not with the administration of analgesia. This suggests that although cortisol is a useful indicator of overall stress, NKA might be more specific for pain. There was a weak correlation between plasma SP and NKA. Plasma SP did not correlate with plasma cortisol or other physiological measures of pain used in this study.