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 p ressure (CPP), cerebral blood flow, and brain energy failure is unpred ictable throughout the development of acute intracranial hypertension. The purpose of the present study was to correlate intracranial pressu re with cerebral blood flow velocities and brain energy metabolism in adult rabbits. The acute intracranial hypertension was achieved by pre ssure transmission. Transcranial Doppler waveforms were obtained from the basilar artery for monitoring cerebral blood flow velocities. P-31 -Magnetic resonance spectroscopy was used to assess brain energy metab olism. The diastolic blood flow velocity began to decrease significant ly (34.5%) when the intracranial pressure was equal to half the diasto lic arterial pressure for a CPP of 36 +/- 18 mmHg. Circulatory cerebra l resistances increased significantly (55%) for the same value of CPP. Diastolic frequency was near zero when intracranial pressure approach ed diastolic arterial pressure (51 +/- 12 mmHg), corresponding to a CP P of 30 +/- 15 mmHg. At the same time, only a tendency for brain energ y metabolism to decrease was observed. Consequently, transcranial Dopp ler sonography could be proposed for the follow-up of intracranial hyp ertension. Magnetic resonance spectroscopy could help to monitor these patients and could be especially proposed in case of high intracrania l pressure (near diastolic arterial pressure). The joint use of these two methods would help in making appropriate therapeutic decision in h umans.