ADRENOCORTICAL FUNCTION IN THE VERY-LOW-BIRTH-WEIGHT INFANT - IMPROVED TESTING SENSITIVITY AND ASSOCIATION WITH NEONATAL OUTCOME

Objective: To evaluate adrenocortical function in ill preterm infants and investigate potential relationships between plasma cortisol concen trations and major neonatal outcomes. Study design: Randomized trial o f adrenocorticotropic hormone ((1-24)ACTH) stimulation testing, follow ed by a chart review. Setting Two level III neonatal intensive care un its, Sacramento, Calif. Participants: Sixty-seven very low birth weigh t infants, born at 32 weeks of gestation or earlier weighing 1500 gm o r less, who had endotracheal intubation and indwelling arterial access . Results: Most infants (76%) had baseline cortisol concentrations <41 4 nmol/L (15.0 mu g/dl), and of those, only 36% responded to stimulati on with (1-24)ACTH, 0.1 mu g/kg. Raising the (1-24)ACTH dose to 0.2 mu g/kg resulted in a response rate of 67% (p = 0.09) but decreased the sensitivity of the test. An elevated mean 11-deoxycortisol/cortisol ra tio indicated that decreased 11 beta-hydroxylase activity may limit co rtisol production in some infants. Infants with baseline cortisol conc entrations less than 414 nmol/L (15.0 mu g/dl) were more likely to hav e chronic lung disease (p <0.002) and less likely to have severe intra ventricular hemorrhage (p <0.02). Response to (1-24)ACTH was ndt assoc iated with a detectable difference in outcome. Conclusion: Many very l ow birth weight infants have low cortisol and ACTH concentrations and are unable to mount a cortisol response to physiologic doses (0.1 mu g /kg) of (1-24)ACTH. These findings suggest that delayed maturation of adrenal response may result in physiologically inadequate cortisol con centrations in stressed very low birth weight infants. This delayed ma turation may contribute to the development of chronic lung disease.