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Cerebrovascular autoregulation during fetal development in sheep
S Helou1, R C Koehler, C A Gleason
1Department of Pediatrics, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287.
The American Journal of Physiology
|March 11, 1994
Summary
Fetal sheep at 92 days gestation show poor cerebrovascular autoregulation, with impaired ability to maintain cerebral blood flow during reduced cerebral perfusion pressure. By 132 days gestation, autoregulation is evident, suggesting development near term.
Area of Science:
- Perinatal physiology
- Neuroscience
- Developmental biology
Background:
- Limited data exist on fetal cerebrovascular autoregulation development.
- Understanding this process is crucial for assessing fetal brain vulnerability.
Purpose of the Study:
- To test if cerebrovascular autoregulation is absent in mid-gestation and near-term fetal sheep.
- To investigate the relationship between cerebral perfusion pressure and cerebral blood flow in developing fetuses.
Main Methods:
- Chronic catheter implantation in fetal sheep for measuring cerebral blood flow (CBF) via microspheres.
- Stepwise reduction of cerebral perfusion pressure (CPP) using artificial cerebrospinal fluid infusion.
- Assessment of cerebrovascular resistance (CVR) and CBF at different CPP levels in fetuses at 92 and 132 days gestation.
Main Results:
- In 92-day fetuses, CBF decreased significantly with reduced CPP, and CVR showed no overall significant change.
- In 132-day fetuses, CBF remained stable despite reduced CPP, indicating a decrease in CVR.
- No significant changes in arterial blood gases were observed in either group at reduced CPP.
Conclusions:
- Cerebrovascular autoregulation is underdeveloped at 92 days gestation (0.63 term) in fetal sheep.
- Autoregulatory capacity is present near term (132 days gestation).
- Poor autoregulation in premature fetuses may increase the risk of brain injury.