[Surgery of high-flow arteriovenous malformation: with special reference to normal perfusion pressure breakthrough phenomenon].

Hemodynamic changes are of importance while removing large and high-flow arteriovenous malformations (AVM), because a phenomenon called "normal perfusion pressure breakthrough" may occur. In this report, we evaluated hemodynamic changes in 14 cases of high-flow AVM with cerebral angiogram and intraoperative monitoring of cortical-surface blood flow. The criteria we used for high-flow AVM are; nidus larger than 4 cm, a few large feeders, high-flow shunt in the nidus, and reduced circulation or dilated arteries in the adjacent brain tissue. For last 2 years, we experienced 14 cases of high-flow AVM which fulfilled the criteria, and 9 of these were operated on for total removal of AVM. Of those, 2 cases evolved postoperative local edema and hemorrhage and was thought to be due to "normal perfusion pressure breakthrough." Intraoperative monitoring of cortical-surface blood flow was useful to predict occurrence of "perfusion breakthrough", because blood flow in the adjacent brain tissue increased markedly with feeder clipping. Intraoperative barbiturate protection and postoperative controlled hypotension were thought to be useful for prevention of "normal perfusion pressure breakthrough", though the details of mechanisms are unknown.