Abstract
Intracranial cerebral arterial blood flow was measured in 33 patients with an electromagnetic flow meter to investigate the hemodynamic state during surgery for cerebrovascular disease. These cases were composed of 25 intracranial aneurysms, 1 arteriovenous malformation, 1 hemangioblastoma, and 6 STA-MCA anastomosis. Specially designed probes were made and an electromagnetic flow meter with the auto-zero balance system was used to facilitate measurement of the cerebral arterial blood flow. A probe with an appropriate size and sensitivity was applied to the carefully exposed cerebral artery. Blood flow could be measured in the internal carotid artery (ICA) (14 cases), M1 (7 cases) and M2 portion (3 cases) of the middle cerebral artery (MCA) and in the surperficial temporal artery (STA) after bypass surgery. The collateral potential of the circle of Willis was evaluated from the changes in MCA blood flow following test occlusion of the ICA in 2 cases. The effects of brain retraction (8 cases) and induced hypotension with ATP infusion method (8 cases) were also studied.
The mean arterial blood flow in the ICA, M1 and M2 portion of the MCA were 144 ml/min, 81 ml/min, and 28 ml/min, respectively. The anastomotic blood flow in the STA was 27 ml/min on the average. Test occlusion of the ICA demonstrated the patient's collateral capacity through the anterior and posterior communicating arteries in each case. Induced hypotension showed that the arterial blood pressure threshold of the autoregulatory response was 58 mmHg in normotensive patients. Brain retraction, ranging from 150 to 300 mmH2O (average 250 mmH2O), decreased blood flow by approximately 20 percent of the control value.
It was suggested that the specially designed probes and electromagnetic flow meter could investigate the intracranial arterial blood flow during surgery without any serious side effects. Measurements of the cerebral arterial blood flow with this method gave important clues to the management of the main cerebral arteries and to the protection of the brain from ischemic insult.
