Concurrent changes in intracranial pressure, cerebral blood flow velocity, and brain energy metabolism in rabbits with acute intracranial hypertension.

The relationship between intracranial pressure or cerebral perfusion pressure (CPP), cerebral blood flow, and brain energy failure is unpredictable throughout the development of acute intracranial hypertension. The purpose of the present study was to correlate intracranial pressure with cerebral blood flow velocities and brain energy metabolism in adult rabbits. The acute intracranial hypertension was achieved by pressure transmission. Transcranial Doppler wave-forms were obtained from the basilar artery for monitoring cerebral blood flow velocities. 31P-Magnetic resonance spectroscopy was used to assess brain energy metabolism. The diastolic blood flow velocity began to decrease significantly (34.5%) when the intracranial pressure was equal to half the diastolic arterial pressure for a CPP of 36 +/- 18 mmHg. Circulatory cerebral resistances increased significantly (55%) for the same value of CPP. Diastolic frequency was near zero when intracranial pressure approached diastolic arterial pressure (51 +/- 12 mmHg), corresponding to a CPP of 30 +/- 15 mmHg. At the same time, only a tendency for brain energy metabolism to decrease was observed. Consequently, transcranial Doppler sonography could be proposed for the follow-up of intracranial hypertension. Magnetic resonance spectroscopy could help to monitor these patients and could be especially proposed in case of high intracranial pressure (near diastolic arterial pressure). The joint use of these two methods would help in making appropriate therapeutic decision in humans.