ESPE Abstracts

Background: Newborns admitted to the intensive care unit (ICU) are exposed to multiple painful and stressful procedures. It is postulated that high pain exposure in the first weeks of life can have a long-lasting impact on the hypothalamic-pituitary-adrenal (HPA) axis. Assessment of the salivary cortisol (SC) is a useful method for non-invasive monitoring of baseline activity and stress response of HPA axis.

Objective: Analysis of differences in morning concentrations of SC and its stress response between term and preterm children. Evaluation of HPA hyperreactivity to neutral stimulus in newborns hospitalized in ICU.

Methods: Infants hospitalized in ICU were assessed for the study. Preterm neonates were enrolled after completion of 35 weeks of postmenstrual age (PMA). Saliva samples for assessment of morning cortisol concentrations were obtained between 6 and 9 a.m. before routine nursing procedures and at least 60 minutes after feeding. To investigate infants stress response additional saliva samples were collected 20 minutes after 2 types of procedures: nappy change (neutral) and blood sampling (painful). Each procedure was analyzed on the different day.

Results: The study group consisted of 25 (38.46%) term and 40 (61.54%) preterm neonates. Term and preterm infants did not differ in the morning SC (2.27 (1.5-5.25) ng/ml v.s. 2.72 (1.87-5.14) ng/ml, P = 0.4). The significant increase of SC after vein puncture was observed both in term (1.75 (1.25-3.72) ng/ml v.s. 6.06 (3.45-8.02) ng/ml, P = 0.002) and premature newborns (2.57 (1.55-3.61) ng/ml v.s. 5.35 (2.59-7.13) ng/ml, P < 0.001). There was no difference in SC increase after vein puncture between the analyzed subgroups (P = 0.22). In premature children SC has increased also after nappy change (1.9 (1.45-3.68) ng/ml v.s. 2.84 (1.86-5.6) ng/ml, P = 0.002).

Conclusion: Median concentrations of morning SC did not differ between term and preterm infants > 35 weeks of PMA. Prematurity did not affect the response of HPA axis to painful procedure, however, significant increase of SC after neutral stimulus may suggest inadequate hyperreactivity of HPA axis in preterm infants.