Plasma beta-endorphin concentrations and analgesia-muscle relaxation in the newborn infant supported by mechanical ventilation.

We evaluated the effects of pancuronium and opiates on plasma beta-endorphin concentrations in 25 infants supported by mechanical ventilation. Infants receiving opiate were randomly assigned to receive either fentanyl or morphine. There was no change in beta-endorphin concentrations after administration of pancuronium, whereas both fentanyl and morphine reduced beta-endorphin concentrations by approximately 60%.