Cerebrovascular Reactivity after Extra-Intracranial Anastomosis

Abstract

Anastomosis between the extracranial artery and the cerebral artery is now an important reconstructive procedure for cerebrovascular occlusive disease. However, there are still some problems which remain unsolved in the hemodynamics of the anastomotic system. Since the external carotid artery and the cerebral vessels normally possess opposite reactivities to carbon dioxide and other drugs, it is necessary, in EC-IC anastomosis, to ascertain the reactivity of the anastomozed system. In this study, chemical control of the lingo-basilar anastomotic system was investigated in dogs. Blood flow in the basilar and lingual arteries was measured by an electromagnetic flowmeter. The lingual artery was anastomosed end to side to the basilar artery which had been clipped at its origin. Blood flow of this anastomotic system was also measured electromagnetically. (a) Flow in the basilar artery: Following 7% CO2 inhalation, blood flow increased by almost 100%. Intravenous administration of epinephrine and norepinephrine (2 μg/kg) produced a rapid increase in blood flow to 77% and 71 % respectively, associated with a marked rise in systemic blood pressure. Intravenous injection ofpapaverine (2 mg/kg) increased blood flow (136%) despite of a slight fall in BP. The effect of apnea and resumption of respiration on blood flow showed a biphasic change. Acute hypertension was induced by inflation of a balloon which had been inserted into the aorta. Blood flow increased temporarily, but returned rapidly to its resting level. Autoregulation was well maintained. (b) Flow in the lingual artery: Seven percent CO2 inhalation produced a reduction of blood flow (25%). After injection of epinephrine and norepinephrine, the flow was decreased 55% and 48% respectively despite a marked rise in BP. Papaverine produced an increase in blood flow (143%). (c) Flow in the lingo-basilar anastomotic system: Alterations in blood flow following the above-mentioned procedures were well correlated with the changes in the basilar arterial flow. Thus, it may be concluded that the lingo-basilar anastomotic system is chemically controlled through responses of the cerebral vessels and not of the external carotid system.