Change of Cerebral Blood Flow and Autoregulation in Experimentally Induced Arteriovenous Shunt

Kim, Young

Abstract

In order to investigate a hemodynamic complication associated with the resection of a large arteriovenous malformation, we planed the following experiment. We divided the left common caroted artery and the internal jugular vein for microsurgical anastomsis between the rostral carotid and caudal jugular vessel ends : the 2 remaining wessel stumps were ligated. This created an arteriovenous shunt with afferent flow from the contralateral caroted and the basilar artery and retrograde down to the carotid-jugular anastomosis. And then, we occluded the shunt vessels at the each stage of the first and fourth week after anteriovenous shunt. Forty adult cats weighing from 2.2 to 2.4kg were used in this study The animals were devided into 4 groups : group 1(acute occlusion-1 week after shunt, n=10), group 2(staged occlusion-1 week after shunt, n=10), group 3(acute occlusion-4 week after shunt, n=10), group 4(staged occlusion-4 week after shunt, n=10) respectively. The regional cerebral blood flow(rCBF), cardiopulmonary function were measured in each animal group and also observed the response of the cerebral blood flow on induced changes of the blood pressure and the arterial bicarbonate. The arteriovenous shunt patency was evaluated by serial angiography. The results were as follows ; 1) Considerable increases in the mean arterial blood pressure(mABP) as well as bradycardia were observed in acute occlusion groups(group 1, 3). After induced hyercarbia, the increments of mABP in acute occlusion groups were less than staged occlusion groups, considerbly. 2) Significant decreases in the mean pulse rate were observed in acute occlusion groups. the mean pulse rate were the highest decrease in group 3. 3) The values of rCBF of left frontal cortex in acute occlusion groups were more greater increase than those of staged occlusion groups considerably. 4) After induced hypercarbia, considerable increases of the rCBF were demonstrated in all groups and increases of the rCBF were lowest in group 3 compared with the other groups. After induced hypercarbia, considerable increases of the rCBF were demonstrated in all groups and reductions of the rCBF were lowest in group 3 compared with the other groups. 5) After induced hypercarbia, considerable increases of the rCBF were demonstrated in all groups. The rCBFs were the highest increase in group3 and lowest increase in group 2 compared with the other groups. After induced hypotension, considerable reductions of the rCBF were demonstrated in all groups. The rCBFs were the highest reduction in group 3 and lowest reduction in group 2 compared with the other groups. It might be infered from these results that patients with large arteriovenous malformations, particulary those with cerebral steal symptoms, are at risk to develp neurologic defictis related to perfusion breakthrough if their malformed vessels are abruptly removed, and staged or gradual occlusion of feeding arteries may prevent this potentially devastating complication.