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Effects of antenatal dexamethasone and hyperglycemia on cardiovascular adaptation to asphyxia in preterm fetal sheep

Authors :
Simerdeep K Dhillon
Alistair J. Gunn
Laura Bennet
Tomoaki Ikeda
Shoichi Magawa
Christopher A. Lear
Yoshiki Maeda
Joanne O. Davidson
Victoria J King
Benjamin A Lear
Source :
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology. 319:R653-R665
Publication Year :
2020
Publisher :
American Physiological Society, 2020.

Abstract

Antenatal glucocorticoids improve outcomes among premature infants but are associated with hyperglycemia, which can exacerbate hypoxic-ischemic injury. It is still unclear how antenatal glucocorticoids or hyperglycemia modulate fetal cardiovascular adaptations to severe asphyxia. In this study, preterm fetal sheep received either saline or 12 mg im maternal dexamethasone, followed 4 h later by complete umbilical cord occlusion (UCO) for 25 min. An additional cohort of fetuses received titrated glucose infusions followed 4 h later by UCO to control for the possibility that hyperglycemia contributed to the cardiovascular effects of dexamethasone. Fetuses were studied for 7 days after UCO. Maternal dexamethasone was associated with fetal hyperglycemia ( P < 0.001), increased arterial pressure ( P < 0.001), and reduced femoral ( P < 0.005) and carotid ( P < 0.05) vascular conductance before UCO. UCO was associated with bradycardia, femoral vasoconstriction, and transient hypertension. For the first 5 min of UCO, fetal blood pressure in the dexamethasone-asphyxia group was greater than saline-asphyxia ( P < 0.001). However, the relative increase in arterial pressure was not different from saline-asphyxia. Fetal heart rate and femoral vascular conductance fell to similar nadirs in both saline and dexamethasone-asphyxia groups. Dexamethasone did not affect the progressive decline in femoral vascular tone or arterial pressure during continuing UCO. By contrast, there were no effects of glucose infusions on the response to UCO. In summary, maternal dexamethasone but not fetal hyperglycemia increased fetal arterial pressure before and for the first 5 min of prolonged UCO but did not augment the cardiovascular adaptations to acute asphyxia.

Details

ISSN :
15221490 and 03636119
Volume :
319
Database :
OpenAIRE
Journal :
American Journal of Physiology-Regulatory, Integrative and Comparative Physiology
Accession number :
edsair.doi.dedup.....4df241edc5f4eb031256e62caca9c23f
Full Text :
https://doi.org/10.1152/ajpregu.00216.2020