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INTRODUCTION

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Acute stroke is the abrupt onset, within seconds to hours, of neurologic deficits resulting from occlusion or rupture of arteries or veins that supply the central nervous system (CNS). By convention, this is a clinical definition and the radiologic–pathologic correlation is infarction. Acute strokes are classified as either hemorrhagic (15%–20%) or ischemic (80%–85%).1 Of the hemorrhagic strokes, intracerebral hemorrhage is three times more common than subarachnoid hemorrhage. Additionally, transient ischemic attacks are temporary episodes of focal neurologic deficits to the brain or retina followed by complete recovery. Also, by convention, the definition of transient ischemia attack (TIA) encompasses full recovery without imaging evidence of infarction, within 24 hours. Most TIAs last for 5 to 20 minutes and events with persistent deficits for several hours are often associated with infarction. As such, a new definition for TIA suggested that the time window for TIA be reduced to less than 6 hours.2 Awareness of these definitions is important in perioperative cerebrovascular disease as the goal of all acute stroke therapies is to recognize stroke symptoms, as well as differentiate strokes, and TIA from other acute, focal, neurologic, perioperative deficits such as focal seizures or complicated migraine, and ultimately, through rapid and aggressive interventions, convert all putative strokes into TIAs.

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"Time is brain" as regards the treatment of acute ischemic stroke.3 Jeffrey Saver quantified the ongoing damage in an acute stroke and calculated that each minute during an acute stroke, 1.9 million neurons and 14 billion synapses are lost. Furthermore, for those patients with a large vessel (i.e., carotid, middle cerebral [MCA], or basilar artery occlusion) acute ischemic stroke, 120 million neurons, 830 billion synapses, and 714 km (447 miles) of myelinated fibers are lost each hour. Thus, rapid diagnostic evaluation and intervention, whenever possible, is critical regardless of whether the patient presents from home or has an in-hospital stroke. The challenge, however, for the patient in the perioperative period is recognition of an event. Whereas acute stroke in hospitalized patients potentially offers a greater likelihood of treatment, as there is no delay in arrival to the hospital, determining the onset of stroke symptoms in the perioperative period may be difficult, as the timing of onset may be hard to define because of patient sedation, pharmacologic paralysis, or a delirious state.4 Additionally, while time of arrival to hospital is not an issue, patients who are stable and transferred out of the postoperative care unit or intensive care unit may not be seen as frequently by nursing staff and thus the time window for intervention may be lost. Finally, surgery is typically an absolute exclusion criterion for intravenous (IV) thrombolysis and alternate acute interventions may not always be possible.1

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FREQUENCY AND DISTRIBUTION OF STROKE

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The incidence of stroke in the perioperative period is low. In one series, clinic strokes occurred in 3.6% of cases within 9 days following surgery though the ...

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