Plasma levels of beta-endorphin and substance P in the first year of life in full-term and preterm infants

Study of Neuropeptide Substance P as A Marker of Pain in Newborn Infant

BACKGROUND: Prolonged and repeated untreated pain in newborn infant may produce a relatively permanent adverse long-term sequela. AIM: The aim of this study was to evaluate the potential role for neuropeptides substance P (SP) as neurochemical pain marker in newborn infants in order to decrease unnecessary use of analgesics and protect the developing brain. METHODS: This case-control study was conducted on 60 newborn infants. They were assigned to four groups, control preterm, sick preterm, control full term, and sick full term. All neonates were subjected to estimation of pain through neonatal infants pain score (NIPS) as well as Neuropeptide SP on the 1st and 5th day of life. The NIPS addresses five behavioral parameters (facial expression, crying, arm movement, leg movement, and state arousal) and one physiological parameter (breathing pattern). Results were further evaluated according to nature of the procedures; invasive and non-invasive procedures. RESULTS: There was a significant increase in the severity of pain score among the sick preterm and full-term infants after invasive procedures. There was a significant increase in SP in the sick preterm group than the control preterm on the 1st and 5th day of life; p were =0.003 and = 0.037, while full-term infants showed significant increase on the 5th day; p = 0.005. Furthermore, there was no significant difference in SP values between the preterm and full-term infants on the 1st and 5th day of life. SP increased significantly after invasive procedures than noninvasive procedures in the sick full-term and sick preterm infants weather in the 1st or 5th day of life. There was a significant correlation between the pain score NIPS and SP level on the 1st day of life. CONCLUSION: SP can be used as pain marker in sick preterm and full-term newborn infants. It showed increase with invasive procedures, acute and chronic pain.

Normative values of substance P and neurokinin A in neonates

BACKGROUND

Substance P (SP) and neurokinin A (NKA) are neuropeptides that have been researched as pain markers in adults, as they are involved in transmission and modulation of pain signals. There is a potential role for them as neurochemical markers of pain in neonates, but this has never previously been investigated.

AIM

To establish normative values of SP and NKA in neonates.

METHODS

Longitudinal once-daily morning blood samples were collected over two weeks from 142 neonates, gestation 23-40 weeks. Peptides were extracted, and then quantified using an in-house radioimmunoassay. Infants with presumed painful conditions were excluded.

RESULTS

SP concentrations ranged from <0.98 to 11.2 pmol/L (median 1.7 pmol/L) and NKA concentrations from <1.95 to 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 SP during the first three days, which decreased again by day 14. Median NKA showed a similar rise, but was not statistically significant. This postnatal rise and fall were more apparent in preterm infants < or = 32 weeks gestation.

CONCLUSIONS

This is the first description of normative values of SP and NKA in neonates. SP and NKA show changes with postnatal age, which are more marked in preterm infants.