Background: Little is known about the effects of clustered nursing care on hypothalamic pituitary axis (HPA) responses in preterm infants in the neonatal intensive care unit.
Aims: To examine facial responses, adrenocorticotropic hormone (ACTH) and cortisol levels, and the relationship between ACTH and cortisol in preterm infants in two gestational age groups (extremely low gestational age [ELGA: < or =28 weeks]; very low gestational age [VLGA: 29-31 weeks]) under basal conditions and in response to routine nursing procedures.
Study design: Within subjects' cross-over design in random order.
Subjects: Ninety preterm infants with no postnatal steroid exposure were studied at 32+/-1 weeks postconceptional age.
Outcome measures: Facial actions, ACTH and cortisol levels were measured after a 30 minute rest period and in response to routine clustered nursing care (CC). Changes in facial actions were analyzed using repeated measures ANOVA. MANOVA or Mann-Whitney U tests were used to determine differences in ACTH and cortisol between gestational age groups. Spearman rank correlations were used to examine relationships between perinatal variables and facial, ACTH and cortisol levels.
Results: All infants had significantly increased facial responses to CC (p=0.001). Infants having experienced higher numbers of skin breaking procedures 24 h before basal assessment had higher basal cortisol levels (r=0.30, p=0.01). In response to CC, ELGA infants showed no correlation between ACTH and cortisol levels; VLGA infants showed a strong, positive correlation (r=0.62, p=0.02).
Conclusion: The pattern of relationship between ACTH and cortisol differs depending on gestational age at birth in response to clustered nursing care. Prior pain alters responsiveness and HPA dysregulation is apparent in ELGA infants.