ORIGINAL ARTICLE

Early pituitary-adrenal response and respiratory outcomes in preterm infants

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

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, Chinese University of Hong Kong

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

Objective: To assess the influence of circulating (basal) and stimulated plasma adrenocorticotrophin (ACTH) and serum cortisol on the duration of oxygen supplementation and development of chronic lung disease (CLD) in preterm, very low birthweight infants.

Methods: A total of 226 human corticotrophin releasing hormone stimulation tests were performed on 137 very low birthweight infants on days 7 and 14 in a tertiary neonatal centre.

Results: Multivariate regression analysis showed that the duration of oxygen supplementation was negatively associated with birth weight, but positively associated with alveolar-arterial oxygen gradient (A-aDO₂) on the first day and with basal serum cortisol on day 14. In addition, the multivariate classification and regression trees model indicated that the two most useful indices for predicting CLD were clinical risk index for babies (CRIB) score (> 9) and peak serum cortisol (> 740 nmol/l) on day 14. The sensitivity, specificity, positive and negative predictive values of these factors for predicting CLD were 53%, 80%, 81%, and 70% respectively.

Conclusions: The findings suggest that birth weight, severity of initial respiratory failure as reflected by the A-aDO₂ gradient, and continuing "stress" with persistent increase in serum cortisol on day 14 are significant risk factors associated with the duration of oxygen supplementation, whereas early pituitary-adrenal response (basal and peak plasma ACTH and serum cortisol on day 7) is not an independent risk factor. Although CRIB score in combination with peak serum cortisol on day 14 are useful predictors of CLD, the need to use a stimulation test and the relatively late timing of the forecast render these indices unattractive for routine clinical use.

Keywords: adrenocorticotrophin (ACTH); chronic lung disease; clinical risk index for babies (CRIB); corticotrophin releasing hormone; cortisol

Abbreviations: A-aDO₂, alveolar-arterial oxygen gradient; ACTH, adrenocorticotrophin; CART, classification and regression trees; CLD, chronic lung disease; 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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