Brain tissue oxygenation in patients with cerebral occlusive disease and arteriovenous malformations

It is not clear if ventilation with oxygen increases brain tissue oxygenpressure (PO2) during ischaemia. We have measured brain tissue PO2, carbondioxide pressure (PCO2) and pH during baseline anaesthesia and oxygenventilation in non-ischaemic control patients (n = 9), patients withcerebral occlusive disease (n = 11) and patients with arteriovenousmalformations (AVM, n = 12). The same anaesthetic treatment was given toall groups and anaesthesia was constant during the study. Arterialpressure, brain temperature and arterial blood-gas tensions were similarbetween groups. Under baseline conditions, brain tissue PO2 was mean 4.2(SD 1.4) kPa in the controls and was 70% lower in patients with ischaemiaand AVM. Patients with occlusive disease also had elevated tissue PCO2 andacidosis. During oxygen ventilation, PO2 increased to 7.5 (2.9) kPa incontrols and this was 50% greater than the increase in the ischaemia andAVM patients. The results showed that baseline tissue oxygenation andincreases in PO2 during hyperoxia were attenuated in patients withischaemia or AVM.