Various factors related to the pathophysiology of perioperative stroke can be used to guide the prevention of perioperative stroke. First, and perhaps most importantly, anesthesiologists and surgeons should be aware of a prior history of the occurrence of cerebral ischemia. If a prior history exists, appropriate preoperative evaluation should be performed, including CT, angiography, ultrasound, and other tests related to intracranial circulation. This information can be used to determine whether to proceed with anesthesia or to adjust anesthetic management methods to address these risk factors for stroke. An assessment of cerebrovascular reserve capacity should be considered in the decision-making process. Those patients with carotid or intracranial atherosclerosis should be considered to have impaired cerebrovascular reserve, as should patients with a history of transient cerebral ischemia. All patients with intracranial edema should be considered to have impaired cerebrovascular reserve. All patients judged to have impaired cerebrovascular reserve require special attention from the anesthesiologist to ensure that the physiologic stresses that cause stroke are avoided, even though they are tolerated in the daily management of healthy patients. Such examples include hemoglobin below 10 g% or a mean arterial pressure lower than the basal value at wakefulness. The use of additional monitoring methods, such as EEG monitoring, evoked potentials, or transcranial Doppler to intraoperatively monitor blood flow, should be considered reasonable, although there are no prospective studies demonstrating that these monitors can affect prognosis. Arrhythmias, particularly atrial fibrillation, make patients particularly at high risk for perioperative stroke, possibly due to the negative synergistic effect of such arrhythmias and hypercoagulable states. The possibility that patients with perioperative atrial fibrillation may have thrombus and may form intraoperative emboli should be considered with caution. Newly developed atrial fibrillation in the perioperative period must be rapidly reversed, and every effort should be made to rapidly convert to sinus rhythm. Perioperative intracranial hemorrhage is most likely to be associated with hypertension among the individual risk factors. Therefore, patients with a preoperative history of cerebral aneurysm or hypertension (potentially already tolerated) should be managed aggressively. Intracranial hemorrhage may also be associated with perioperative hypertension. In craniotomy, a systolic blood pressure greater than 160 mm Hg is considered to be associated with postoperative intracranial hemorrhage,43 and is considered a reasonable threshold to prevent intracranial hemorrhage in this setting. Similar studies are not available for nonneurosurgical procedures, but it is appropriate to follow this guideline in other situations.