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 i.m. 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 d 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.

中文翻译：

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产前地塞米松和高血糖对早产胎羊心血管适应性窒息的影响

产前糖皮质激素可改善早产儿的预后，但与高血糖症有关，高血糖症可加剧缺氧缺血性损伤。尚不清楚产前糖皮质激素或高血糖如何调节胎儿对严重窒息的心血管适应性。在这项研究中，早产胎羊接受生理盐水或12 mg孕产妇地塞米松治疗，然后4小时后完全脐带闭塞（UCO）25分钟。UCO在4小时后接受了另一批胎儿的滴定葡萄糖输注，以控制高血糖对地塞米松心血管作用的影响。UCO后胎儿研究了7天。孕妇地塞米松与胎儿高血糖（p <0.001），动脉压升高（p <0.001）和股骨减少（p <0）有关。005）和UCO前的颈动脉（p <0.05）血管电导。UCO与心动过缓，股血管收缩和短暂性高血压有关。在UCO的前5分钟内，地塞米松-窒息组的胎儿血压高于生理盐水-窒息（p <0.001）。但是，动脉压的相对升高与盐水窒息没有区别。盐水组和地塞米松-窒息组的胎儿心率和股血管电导率均降至最低点。持续进行UCO期间，地塞米松不影响股血管张力或动脉压的逐步下降。相比之下，输注葡萄糖对UCO的反应没有影响。综上所述，