Читать книгу Manual of Equine Anesthesia and Analgesia - Группа авторов - Страница 330

 Cerebral blood flow increases with cerebral oxygen demand (especially when PaO2 decreases below 50 mmHg) and increases linearly with PaCO2 over the range 20–80 mmHg (see Figure 6.1).

 Hypothermia blunts the response to changing PaCO2.

 The response to CO2 is maintained during volatile and intravenous anesthesia.

 Normal cerebral blood flow in humans is 50 ml/100 g/minute and it has not been quantified in horses.

 Flow is greatest in neonates and declines with age, and within gray matter (80 ml/100 g/minute).

 Autoregulation maintains constant brain–blood flow over a range of mean systemic blood pressures (60–130 mmHg). Autoregulation is dependent on two processes:Vascular smooth muscle responses which occur over 30–40 seconds.Neural mediated vasodilation through cranial nerve VII.

 Arterial hypercapnia or hypoxemia, atropine, and volatile anesthesia administration may attenuate or abolish autoregulation.

Figure 6.1 The effects of arterial partial pressure of O₂ and CO₂, and perfusion pressure on cerebral blood flow.