A clinical study of the parameters and effects of temporary arterial occlusion in the management of intracranial aneurysms.

Temporary occlusion of intracranial arteries has emerged as a valuable technical adjunct in the management of intracranial aneurysms. The current study considered 121 patients (from a group of 234 consecutive aneurysm patients treated during a 2-yr period) who underwent elective temporary arterial occlusion. Twenty-one patients were excluded from further study because of an intraoperative rupture of an aneurysm, the elective sacrifice of afferent or efferent vessels, or the performance of an extracranial-intracranial arterial bypass graft; the remaining 100 patients underwent elective temporary occlusion under a standard neuroanesthetic regimen, including etomidate-induced burst suppression, normotension, normovolemia, and normothermia. In the postoperative period, radiographic evidence of ischemic brain injury in the distribution of the arteries occluded was selected as the end point for the failure of occlusion tolerance. The parameters evaluated with respect to this end point included the duration and nature of the temporary arterial occlusion, the number of the occlusive episodes, the specific vascular territory occluded, patient age, neurological status, presence of subarachnoid hemorrhage, vasospasm, and aneurysm size. Several parameters were found to be related to the postoperative development of ischemic injury. Patients more than 61 years of age and those in poor neurological condition (Hunt and Hess Grades III to IV) did not tolerate temporary occlusion as well as patients who were younger and in better condition. Patients occluded for less than 14 minutes routinely tolerated the iatrogenic ischemia; the 95% confidence level for the toleration of occlusion without the development of infarction occurred at 19 minutes. All patients occluded for more than 31 minutes had both clinical and radiographic evidence of cerebral infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral arterial diameters during changes in blood pressure and carbon dioxide during craniotomy.

Forty-five measurements of diameters of 12 human cerebral arteries were performed during 10 craniotomies under moderate changes in mean blood pressure and end tidal CO2. The mean change in blood pressure was 30 +/- 16 mm Hg (standard deviation) and that of end tidal CO2 was 14 +/- 6 mm Hg (standard deviation). These changes were induced with nitroprusside, phenylephrine, and adjustment of ventilator rate. Measurements were made through the operating microscope focused at the highest power, with meticulous attention to constant angle and distance from the artery. The mean diameter change in the large cerebral arteries (carotid, middle cerebral artery, vertebral artery) was less than 4%, but the smaller arteries (anterior cerebral artery, M2 segment of middle cerebral artery) showed diameter changes as large as 29% and 21% to end tidal CO2 and blood pressure changes, respectively. These data suggest that at the time of craniotomy, diameters of the large cerebral vessels do not significantly change during moderate variations in blood pressure and CO2, but that larger changes may occur in smaller vessels. This constancy of diameter suggests that the transcranial Doppler velocities obtained during intraoperative monitoring of craniotomies may closely reflect blood flow through the insonated artery.