Circadian rhythm of salivary cortisol in infants with congenital heart disease.

Children with congenital heart disease (CHD) have associated extracardiac co-morbidities at the time of surgery and during ongoing growth and development. Perioperative events include disrupted glucose homeostasis, capillary leak, and fluid retention. The hypothalamic-pituitary-adrenal (HPA) axis has an important role in homeostasis in that the secretion of cortisol contributes to the response to stress, glucose regulation, blood volume control, and immune regulation. We investigated the diurnal rhythm of the HPA axis in infants with CHD by measuring salivary cortisol in the morning (0600-0900 h-circadian peak) and evening (2100-2400 h-circadian nadir). Twenty-nine infants aged 12 weeks to 1 year were included: 16 with acyanotic disease (SpO₂ ≥ 90 %) and 13 with cyanotic disease (SpO2 < 90 %). Morning salivary cortisol was similar between the two groups [acyanotic 7.0 nmol/L (1.8-23.1); cyanotic 9.7 nmol/L (0.9-15.6); p = 0.68]. Evening salivary cortisol was similar between the two groups [acyanotic 0.9 nmol/L (0.2-8.5); cyanotic 1.4 nmol/L (0.5-14.9); p = 0.32]. Both cyanotic and acyanotic groups demonstrated an intact diurnal rhythm. In conclusion, chronic hypoxia secondary to cyanotic CHD does not affect the circadian rhythm of the HPA axis. By 12 weeks of age, infants with hypoxia secondary to cyanotic CHD have a normal cortisol diurnal rhythm.