Abstract
In the performance of STA-MCA bypass operation for obstructive cerebrovascular disease, it is important to have knowledge of the hemodynamics at the time of surgery and to check the reactivity of anastomotic channel following operation. In EC-IC anastomosis, since an external carotid artery and the cerebral vessels which normally possess opposite reactivity to carbondioxide and other drugs, it is important to ascertain whether the flow through the anastomotic site is not governed by neurogenic control of an external carotid artery and determine the state of the anastomotic channel reactivity, but such means have not yet been fully developed. To elucidate these points, the authors performed the following studies. Experimental brain ischemia was mede and performed EC-IC anastomosis and subjected the anastomosed vessels to various load tests to detemine vascular reactivity.
Measured blood pressure and blood flow during STA-MCA anastomosis procedures in clinical cases and subjected patients to the same load test.
(1) Lingual-basilar anastomosis in dogs was performed after applying a clip to the proximal side of the basilar artery. Blood flow in lingual artery, basilar artery and anastomotic artery were measured respectively using an electromagnetic flow meter. The changes in blood flow following inhalation of CO2 and administration of papaverine hydrochrolide, epinephrine and norepinephrine were recorded and the reactivity to apnea and elevation in blood pressure was also studied. The results revealed that the anastomosed vessels were controlled by the intracranial vesel reactivity.
(2) The mean blood pressure of the cortical branch of the middle cerebral artery in 13 cases measured during surgery prior to anastomosis was 38mmHg, which became 76mmHg after anastomosis. Those with value in excess of 30mmHg prior to surgery showed EP to he effective, while those with hypertension and completed stroke failed to show much clinical benefit. The STA mean blood flow volume as determined by electromagnetic flow meter immediately after anastomosis was 27.1ml/min.
(3) anastomosed channel reactivity was studied using a Doppler flow meter in 10 out of 32 cases who had undergone STA-MCA anastomosis. In cases with TIA and RIND who had shown definite improvement of neurological symptoms also showed good reaction to loads of CO2inhalation, hyperventilation, but reactivity was decreased in completed stroke. The former is considered to reflect the reactivity of the anastomosed channel flow within intracranial small vessels, while in the latter as the vessels are supplying a territory which is in an irreversible state, although the state of blood flow in the STA is good, the reactivity of the small intracranial vessels was found to be poor.
It is considered that in the follow up patients who have undergone anastomosis, confirmation only by the fact that there is good blood via the STA by angiography is inadequate, and the study should be made to determine whether the bypass is functioning and reactive properly.
