Cardiorespiratory depression and plasma beta-endorphin levels in low-birth-weight infants during the first day of life.

Twenty-nine premature infants were studied to determine whether neonatal asphyxia, apnea, and low blood pressure in the first day of life are associated with elevated plasma beta-endorphin concentrations. Plasma beta-endorphin levels were determined at 0.5 to 2, 4 to 6, and 18 to 24 hours of life, using radioimmunoassay. Premature infants with moderate or severe asphyxia (n = 19) had higher levels at 0.5 to 2 hours of age (32.1 +/- 6.7 vs 16.4 +/- 7.4 pmol/L) and significantly higher levels at 4 to 6 hours of age (50.4 +/- 10.0 vs 22.9 +/- 9.2 pmol/L) compared with the ten nonasphyxiated premature infants. A significant elevation in levels at age 0.5 to 2 hours (39.4 +/- 9.9 vs 17.7 +/- 4.4 pmol/L) and age 4 to 6 hours (59.3 +/- 13.8 vs 27.1 +/- 17.1 pmol/L) was observed in premature infants with low blood pressure or impaired perfusion (n = 12) who required the administration of volume expanders. No differences were observed in premature infants with and without apnea. It may be speculated that the increased endogenous release of beta-endorphins in response to perinatal asphyxia may play a role in the pathogenesis of shock observed in the first day of life.