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Atropine prevents increases in brain blood flow during hypertension in newborn piglets
Insights
Hypertension in newborn piglets increased cerebral blood flow, potentially contributing to intraventricular hemorrhage. Atropine prevented this increase during induced hypertension, suggesting a protective mechanism against cerebral hyperperfusion.
Area of Science:
- Neonatal Physiology
- Cerebrovascular Regulation
- Perinatal Medicine
Background:
- Hypertension is linked to intraventricular hemorrhage in preterm infants.
- Understanding cerebral blood flow (BBF) regulation during hypertension is crucial for neonatal care.
Purpose of the Study:
- To investigate the impact of induced hypertension on total and regional brain blood flow in newborn piglets.
- To assess the role of atropine in modulating cerebral circulatory responses to hypertension.
Main Methods:
- Mean arterial blood pressure (MABP) and BBF were measured in newborn piglets.
- Hypertension was induced using metaraminol bitartrate (Aramine), with or without atropine pretreatment.
- Cerebral vascular resistance (CVR) was calculated, and regional BBF was analyzed.
Main Results:
- In piglets without atropine, induced hypertension significantly increased MABP and total BBF, particularly to the cerebrum and cerebellar cortex.
- Cerebral vascular resistance initially increased then decreased post-hypertension, while BBF remained elevated.
- Atropine pretreatment prevented the increase in BBF during hypertension, despite a greater rise in MABP, and maintained vascular resistance.
Conclusions:
- Hypertension can lead to increased cerebral blood flow in newborns, with regional variations.
- Atropine mitigates hypertension-induced increases in cerebral blood flow in piglets.
- These findings have implications for managing hypertension and preventing intraventricular hemorrhage in neonates.
Abstract:
Cerebral hyperperfusion associated with hypertension, may play an important role in the pathogenesis of intraventricular hemorrhage in preterm infants. To examine the effect of hypertension on changes in total and regional brain blood flow (BBF), we increased the mean arterial blood pressure (MABP) in nine awake newborn piglets by an infusion of 0.7 mg/kg of metaraminol bitartrate (Aramine) (group I) and studied cerebral circulatory changes. In order to prevent the Aramine-associated bradycardia, we pretreated nine other piglets with atropine, which produced a higher level of hypertension (group II). MABP and BBF were measured and cerebral vascular resistance (CVR) was calculated during baseline, the Aramine infusion, and twice at decreasing MABP following the discontinuation of the Aramine infusion. In group I, the significant increase in MABP from 68 +/- 3 to 100 +/- 3 mm Hg (mean +/- SEM) during the Aramine infusion resulted in a significant increase in BBF (98 +/- 9 to 118 +/- 11 ml X min-1 X 100 g-1). MABP decreased significantly (although remained significantly above baseline levels), when Aramine was discontinued; however, total BBF remained elevated. CVR increased during the Aramine infusion, but decreased significant (versus the Aramine-infused state) in the post-Aramine period. Regional BBF increased significantly to the cerebrum and cerebellar cortex, but remained unchanged to the other regions including the brain stem. In group II, the Aramine infusion resulted in a significantly greater increase in MABP, a sustained increase in vascular resistance, and no increase in total BBF. Thus, atropine prevents increased BBF during hypertension in the newborn piglet.