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PLASMA BETA ENDORPHIN CONCENTRATION IN INFANTS WITH APNEIC SPELLS

In an attempt to determine whether plasma beta endorphin (β-ED) concentrations correlate with occurrence of apnea in preterm infants, measurements were made in three groups of infants. Group 1 consisted of 11 control infants with a mean gestational age of 30.5 ± 0.8 weeks, a mean birthweight of 1650 ± 180 g, and a mean postnatal age of 1.3 ± 0.5 days. Group 2 consisted of 8 infants with a mean gestational age, birthweight and postnatal age of 30 ± 0.9 weeks, 1165 ± 90 g and 7.8 ± 1.9 days, respectively. Group 3 consisted of 8 infants with a mean gestational age, birth-weight and postnatal age of 31 ± 0.8 weeks, 1380 ± 125 g and 2.6 ± 0.9 days, respectively. Group 2 and Group 3 infants suffered varying degrees of apnea. Group 2 infants suffered clinically severe apneic spells with bradycardia and hypotension whereas Group 3 did not. β-ED was measured by a method previously published (Hindmarsh) involving Sephadex G-50 column chromatography and subsequent radioimmunoassay. The plasma endorphin concentrations were 26.9 ± 2, 68.0 ± 9.0 and 39.6 ± 2.0 pg/ml in Groups 1, 2 and 3, respectively. Significant elevation in β-ED concentration was observed in Group 2 when compared to control (Group 1) and Group 3. Elevation of plasma β-ED is observed in infants with severe apneic spells. The association of increased plasma β-ED release with severe apneic spells may suggest that these endogenous opioids play a role in the pathophysiology of apnea of prematurity.