ORIGINAL ARTICLE

Transient adrenocortical insufficiency of prematurity and systemic hypotension in very low birthweight infants

P C Ng¹, C H Lee¹, C W K Lam², K C Ma¹, T F Fok¹, I H S Chan², E Wong³

¹ Department of Paediatrics, Prince of Wales Hospital, Chinese University of Hong Kong
² Department of Chemical Pathology, Prince of Wales Hospital
³ Centre for Clinical Trials and Epidemiological Research, Prince of Wales Hospital

Correspondence to:
Correspondence to:
Professor Ng
Department of Paediatrics, Level 6, Clinical Sciences Building, Prince of Wales Hospital, Shatin, NT, Hong Kong; pakcheungng{at}cuhk.edu.hk

Objectives: A proportion of preterm, very low birthweight (VLBW, < 1500 g) infants may show inadequate adrenal response to stress in the immediate postnatal period. The human corticotrophin releasing hormone (hCRH) stimulation test was used to: (a) determine the relation between pituitary-adrenal response and systemic blood pressure in these infants; (b) characterise the endocrinological features of transient adrenocortical insufficiency of prematurity (TAP).

Study design: A total of 226 hCRH tests were performed on 137 VLBW infants on day 7 and 14 of life in a tertiary neonatal centre.

Results: Basal, peak, and incremental rise in serum cortisol (Cort_0–30) on day 7 were associated significantly with the lowest systolic, mean, and diastolic blood pressures recorded during the first two weeks of life (r > 0.25, p < 0.005). These cortisol concentrations also correlated significantly but negatively with the maximum and total cumulative dose of dopamine (r > -0.22, p < 0.02), dobutamine (r > -0.18, p < 0.04), and adrenaline (r > -0.26, p < 0.004), total volume of crystalloid (r > -0.22, p < 0.02), and duration of inotrope treatment (r > -0.25, p < 0.006). Multivariate regression analysis of significant factors showed that the lowest systolic, mean, and diastolic blood pressures remained independently associated with serum cortisol (basal, peak, and Cort_0–30) on day 7. Hypotensive infants requiring inotropes (group 2) were significantly less mature and more sick than infants with normal blood pressure (group 1). The areas under the ACTH response curves were significantly greater in group 2 than in group 1, on both day 7 (p = 0.004) and day 14 (p = 0.004). In contrast, the area under the cortisol response curve was significantly greater in group 1 than in group 2 on day 7 (p = 0.001), but there was no significant difference between the two groups on day 14. In addition, serum cortisol at the 50th centile in hypotensive infants had high specificity and positive predictive value (0.80–0.93 and 0.81–0.89 respectively) for predicting early neonatal hypotension.

Conclusions: This study characterises the fundamental endocrinological features of TAP: normal or exaggerated pituitary response; adrenocortical insufficiency; good recovery of adrenal function by day 14 of postnatal life. The results also provide the centiles of serum cortisol for hypotensive patients and infants with normal blood pressure, and show a significant relation between serum cortisol and blood pressure in VLBW infants.

Keywords: adrenocorticotrophin (ACTH); corticotrophin releasing hormone; cortisol; hypotension; preterm infants

Abbreviations: ACTH, adrenocorticotrophin; hCRH, corticotrophin releasing hormone; HFOV, high frequency oscillatory ventilation; HPA, hypothalamic-pituitary-adrenal; IPPV, intermittent positive pressure ventilation; TAP, transient adrenocortical insufficiency of prematurity; VLBW, very low birthweight

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