Abstract
The purpose of this study was to determine if baseline oxygen pressure (PO2), carbon dioxide pressure (PCO2), and pH in brain tissue adjacent to an arteriovenous malformation (AVM) is different from meas-ures in control patients. In addition, PO2, PCO2, and pH changes were measured during the course of AVM resection. Two groups were studied. Group 1(n=8) were non-ischemic patients scheduled for cerebral aneurysm clipping. Group 2(n=13) were patients undergoing neurosurgery for AVM resec-tion. Following craniotomy, the dura was retracted and a PO2, PCO2, pH sensor inserted into non-ischemic brain tissue in Group 1. In Group 2, the sensor was inserted into tissue adjacent to the AVM. Following equilibration, tissue gases and pH were measured during steady state anesthetic conditions in Group 1 and during AVM resection in Group 2. The results show that under baseline conditions be-fore the start of surgery, tissue PO2, was decreased in AVM compared to control patients but PCO2 and pH were not changed. During AVM resection, PO2, increased, PCO2 decreased, and pH increased com-pared to baseline measures. These parameters did not change in control patients over a similar time period. The results suggest that chronic cerebrovascular adaptation occur in AVM patients with decreased tissue perfusion pressure as an adjustment for decreased oxygen delivery. During AVM resec-tion, this adaptation produces a hyperemic environment with relative tissue hyperoxia, hypocapnia, and alkalosis which is not corrected by the end of surgery.
