INTRAOPERATIVE MONITORING OF SUBSTRATE DELIVERY DURING ANEURYSM AND HEMATOMA SURGERY - INITIAL EXPERIENCE IN 16 PATIENTS

The effects of proximal occlusion of the parent artery during aneurysm surgery in humans are not fully understood, although this method is w idely used. The reduction in substrate that can be tolerated by normal and subarachnoid hemorrhage (SAH)-affected brain is unknown. Therefor e, the authors measured brain oxygen tension (brain PO2), carbon dioxi de tension (brain PCO2), pH, and hemoglobin oxygen (HbO(2)) saturation before and after temporary occlusion in 12 patients with aneurysms. T he effect of removal of a traumatic intracranial hematoma on cerebral oxygenation was also studied in four severely head injured patients. A multiparameter sensor was placed in the cortex of interest and locked by means of a specially designed skull bolt. The mean arterial blood pressure, inspired O-2 fraction, and end-tidal PCO2 were analyzed. Bra in PO2 and HbO(2) saturation data were collected every 10 seconds. Des criptive and nonparametric analyses were used to analyze the data. A w ide range in baseline PO2 was seen, although a decrease from baseline in brain PO2 was found in all patients. During temporary occlusion, br ain PO2 in patients with unruptured aneurysm (seven patients) dropped significantly, from 60 +/- 31 to 27 +/- 17 mm Hg (p < 0.05). In the SA H group (five patients), the brain PO2 dropped from 106 +/- 74 to 87 /- 73 mm Hg (not significant). Removal of intracranial hematomas in fo ur severely head injured patients resulted in a significant increase i n brain PO2, from 13 +/- 9 to 34 +/- 13 mm Hg (p < 0.05). The duration of safe temporary occlusion could not be determined from this group o f patients, because none developed postoperative deterioration in thei r neurological status. However, the data indicate that this technique is useful to detect changes in substrate delivery during intraoperativ e maneuvers. This study also reemphasizes the need for emergency remov al of intracranial hematomas to improve substrate delivery in severely head injured patients.