Compromised cerebral blood flow reactivity is a predictor of stroke in patients with symptomatic carotid artery occlusive disease.

PURPOSE: The purpose of this study was to determine whether the hemodynamic consequences of extracranial carotid disease correlate with the risk of subsequent cerebral infarction. METHODS: In 95 patients with symptoms who had greater than or equal to 70% stenosis (31 patients) or who had occlusion (64 patients) of the ipsilateral carotid artery, cerebral blood flow was measured by the stable xenon/computed tomography technique both at baseline and after vasodilatory challenge with intravenous acetazolamide. Patients were stratified into group 1, 43 patients with no more than a 5% decrease in flow in any vascular territory, and group 2, 52 patients with greater than a 5% decrease in one or more vascular territories after an acetazolamide challenge. RESULTS: In group 2, 15 (28.9%) of 52 patients had a new stroke, but only one (2.3%) of 43 patients in group 1 did (p = 0.0005). Of patients with total carotid occlusion 10 (26%) of 38 in group 2 and none (0%) of 26 in group 1 had a new stroke (p = 0.003). Of patients with greater than or equal to 70% stenosis, five (36%) of 14 in group 2 and only one (6%) of 17 in group 1 had a stroke (p = 0.067). CONCLUSION: The loss of cerebral reactivity in patients with symptoms who had greater than or equal to 70% carotid stenosis or occlusion is an important predictor of impending cerebral infarction.

Stroke risk after abrupt internal carotid artery sacrifice: accuracy of preoperative assessment with balloon test occlusion and stable xenon-enhanced CT.

PURPOSE: To evaluate stable xenon-enhanced CT cerebral blood flow with balloon test occlusion as a predictor of stroke risk in internal carotid artery sacrifice. METHODS: Abrupt internal carotid artery occlusion was performed by surgical or endovascular means below the origin of the ophthalmic artery in 31 normotensive patients who were assessed preoperatively by a 15-minute clinical balloon test occlusion followed by an internal carotid artery-occluded xenon CT cerebral blood flow study. RESULTS: One patient, who passed the clinical test occlusion but exhibited regions of cerebral blood flow less than 30 mL/100 g per minute on the occlusion xenon CT cerebral blood flow study went on to have a fatal stroke corresponding exactly to the region of reduced blood flow. Thirty patients passed both components of the preoperative stroke-risk assessment. Neuroimaging demonstrated possible flow-related infarctions, which subsequently developed in three patients. Two patients were asymptomatic, and one patient was left with a mild residual hemiparesis. CONCLUSIONS: Our protocol provided a statistically significant reduction in subsequent infarction rate and infarction-related death rate when compared with a control group of normotensive abrupt internal carotid artery occlusion patients who did not undergo any preoperative stroke-risk assessment (reported in the literature). The estimated false-negative rate for our preoperative assessment protocol ranged from 3.3% to 10% depending on the assessment of the cause of the three potentially flow-related infarctions. Although life-threatening major vascular territory infarctions have been avoided, our protocol is less sensitive to changes predicting smaller, often minimally symptomatic, vascular border zone infarctions and does not predict postoperative thromboembolic strokes.

An aggressive approach to massive middle cerebral artery infarction.

OBJECTIVE: We report favorable outcome after surgical decompression, or strokectomy, guided by xenon-enhanced computed tomographic studies of cerebral blood flow in the setting of potentially fatal swelling from massive cerebral infarction. DESIGN: Retrospective analysis with 3 months to 3 years of follow-up. SETTING: University of Pittsburgh (Pa) Medical Center, a tertiary care university referral center. PATIENTS: Four patients, aged 14 to 46 years, presented with focal neurologic deficits appropriate for a massive middle cerebral artery infarction (two dominant and two nondominant). In spite of medical therapy, all patients deteriorated to at least a decreased level of consciousness. INTERVENTION: Using xenon-enhanced computed tomographic studies of cerebral blood flow in three patients, areas of severely ischemic (blood flow, < 5 mL/100 g per minute), nonviable brain were identified and resected. OUTCOME MEASURE: Outcome was measured by survival and ability to perform activities of daily living. RESULTS: Postoperatively, all patients recovered rapidly (< 6 hours) to the level of function at admission and were able to perform the activities of daily living with minimal or no assistance. CONCLUSION: Despite deficits appropriate to the area of infarction, prompt management of life-threatening postinfarction swelling by surgical decompression can yield favorable outcome.

Autoregulation remains intact during stable xenon inhalation in the baboon.

To test the possible effect of 32% end-tidal Xe concentration upon autoregulation, 5 baboons, Papio anubis/cynocephalus, were anesthetized/paralyzed with propranolol 0.02, diazepam 0.1, morphine sulfate 0.1, and pancuronium 0.2 (mg/(h.kg)). The animals were subjected to a servocontrolled blood infusion-withdrawal program to control central aortic blood pressure (CAP). PaCO2 was held to 30 to 35 torr, with individual variation less than 3 torr by control of ventilation and by including CO2 in the Xe/O2 mixture. Three to six CBF measurements were made in each subject over the above range. In four animals the CAP was varied between 18 and 150 torr, with corresponding CBF measurements. The CAP range was extended to 196 torr in the 5th animal by IV administration of phenylephrine. Significant lowering of global blood flow did not occur above 40 torr mean CAP. While regulated flow persists to about 150 torr at the high end, there is a breakaway between 150 and 190 torr where flow increased 90%. A 4th order polynomial fit of the data has the characteristic appearance of the familiar autoregulation curve. We conclude that autoregulation is preserved even in the presence of FIXe of 32% in the breathing mixture.

A new method to predict safe resection of the internal carotid artery.

A patent internal carotid artery (ICA) is essential in most patients. Management of skull base lesions often requires translocation, balloon embolization, or resection of this vessel. Preoperative tests to assess the availability of collateral flow have not been uniformly accurate. A new test that significantly increases the safety of surgical removal of the ICA is described. One hundred thirty-six patients were studied with temporary balloon occlusion (TBO) of the ICA and determination of stable xenon-enhanced computed tomography cerebral blood flow (Xe/CT CBF) measurements. Eleven patients failed TBO and were determined to be at very high risk of stroke with loss of the ICA. Ninety-six of the patients were predicted to be at minimal risk with permanent loss of the ICA by Xe/CT CBF studies. Twenty-one patients in this group had either permanent balloon occlusion (PBO) or surgical resection of the ICA with no permanent neurologic sequelae. Our studies show that the combination of preoperative TBO and Xe/CT CBF studies significantly increases the safety of ICA resection.