Abstract
Purpose: Despite scant evidence describing the role of cortisol in blood pressure (BP) regulation in the neonatal population, hydrocortisone is frequently used to treat preterm infants with hypotension resistant to volume and pressor agents. Circulating cortisol exists in 2 forms: protein bound (90%) and the biologically active free form (10%). No prospective studies have examined the relationship between total cortisol and free cortisol in the preterm neonate during the first postnatal week, or the relationship between cortisol values and BP in this group of infants. The primary purpose of this study, therefore, is to characterize total and free cortisol levels over the first week of life and examine their relationship to BP values in the preterm neonate.
Methods: All infants with an estimated gestational age (EGA) ≤32 weeks were eligible for enrollment. After obtaining parental consent, blood samples were obtained 4 times during the first postnatal week (e.g. 24-36hr, 48-72hr, DOL 5 and DOL 7). Data including BP, respiratory status and fluid balance were also obtained at these times. Total and free cortisol was measured using HPLC mass spectrometry and radioimmunoassay.
Results: 35 infants of EGA 30-32 weeks were enrolled between May 2005 and January 2006. Total cortisol values ranged from 1-35μg/dl (7.6 ± 8.5[s.d]) at 24-36hr and trended down to 1-14μg/dl (4.0 ± 3.5) by DOL 7. Free cortisol values ranged from 0.02-25μg/dl (2.2 ± 5.6) at 24-36hr and also showed a downward trend by DOL 7 to 0.02-0.86μg/dl (0.17 ± 0.2). The ratio of free to total cortisol varied from 2-74% (11.8% ± 17%) at 24-36hr to 1-10% (3.9% ± 1.9%). Although there was a significant linear increase in BP over the first week (mean BP at 24-36hr, 41 ± 6.2 vs. DOL 7, 49 ± 7.6 p <. 001), there was no correlation between BP and total cortisol or free cortisol at 24-36hr, 48-72hr or DOL 7 (r = -0.05, -0.04 and -0.1 (total cortisol); -0.01, 0.06, and -0.02 (free cortisol) respectively). A moderate correlation (r = 0.45) between BP and total and free cortisol was noted on DOL 5.
Conclusions: Total cortisol, free cortisol and the percentage of free cortisol trend downward in preterm neonates with an EGA of 30-32 weeks during the first week of life, though a larger sample size will be required to detect if this trend is significant. There is no correlation between total or free cortisol with BP during this time period, making the utility of a random cortisol value to guide treatment for hypotension questionable. Whether this is also true for infants of younger gestational ages is unknown; however, we are in the process of evaluating a concurrent cohort of infants with EGA 24-29 weeks to further examine this question.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Ennis, B., Rosenfeld, C. 8 Cortisol Values do not Correlate with Blood Pressure in Preterm Neonates.. Pediatr Res 60, 491 (2006). https://doi.org/10.1203/00006450-200610000-00030
Issue Date:
DOI: https://doi.org/10.1203/00006450-200610000-00030