Intracranial volume--pressure relationships during experimental brain compression in primates. 2. Effect of induced changes in systemic arterial pressure and cerebral blood flow.

In eight anaesthetized, ventilated adult baboons, the intracranial volume-pressure response was examined at differing levels of raised intracranial pressure during induced changes in systemic arterial pressure and cerebral blood flow. The volume-pressure response is defined as the change in ventricular fluid pressure caused by a volume addition of 0·05 ml to the lateral ventricle. At normal intracranial pressure, the volume-pressure response was unchanged by alterations in systemic arterial pressure and cerebral blood flow. At raised intracranial pressure, however, systemic arterial hypertension rendered the intracranial contents more sensitive to the effects of an addition to the ventricular volume as shown by an increased volume-pressure response. When intracranial pressure was increased, there was a significant linear correlation between the volume-pressure response and both arterial pressure and cerebral blood flow. The clinical implication of this phenomenon is that arterial hypertension in patients with increased intracranial pressure is likely to have a deleterious effect by increasing brain tightness.