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KEY CONCEPTS
Induction of anesthesia in patients receiving long-term levodopa therapy may result in either marked hypotension or hypertension.
In patients with multiple sclerosis, increases in body temperature cause exacerbation of symptoms.
The major risk of anesthesia in patients with autonomic dysfunction is severe hypotension, compromising cerebral and coronary blood flow.
Autonomic hyperreflexia should be expected in patients with spinal cord lesions above T6 and can be precipitated by surgical manipulations.
The most important interaction between anesthetic agents and tricyclic antidepressants is an exaggerated response to both indirect-acting vasopressors and sympathetic stimulation.
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Patients with vascular and nonvascular neurological diseases or psychiatric disorders are frequently encountered by anesthesia providers. Anesthesiologists must have a basic understanding of the major neurological and psychiatric disorders and their drug therapy. Failure to recognize potential adverse anesthetic interactions may result in avoidable perioperative morbidity.
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CEREBROVASCULAR DISEASE
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Preoperative Considerations
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Patients with diagnosed cerebrovascular disease typically have a history of transient ischemic attacks (TIAs) or stroke. Patients with TIAs undergoing surgery for other indications have an increased risk of perioperative stroke. Asymptomatic carotid bruits occur in up to 4% of patients older than age 40 years, but do not necessarily indicate significant carotid artery obstruction. Fewer than 10% of patients with completely asymptomatic bruits have hemodynamically significant carotid artery lesions. An asymptomatic carotid bruit may not increase the risk of stroke following surgery, but it increases the likelihood of coexisting coronary artery disease. Moreover, the absence of a bruit does not exclude significant carotid obstruction.
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The risk of perioperative stroke increases with patient age and varies with the type of surgery. Although the overall risk of stroke associated with surgery is low, it is greater in patients undergoing cardiovascular or cerebrovascular surgery. Rates of stroke after general anesthesia and surgery range from 0.08% to 0.4%. Even in patients with known cerebrovascular disease, the risk is only 0.4% to 3.3%. Patients at greatest risk of postoperative stroke are those undergoing open heart procedures for valvular disease, coronary artery disease with ascending aortic atherosclerosis, and diseases of the thoracic aorta. Stroke following open heart surgery is usually attributed to embolism of air, clots, or atheromatous debris. In one study, 6% of patients experienced an adverse neurological outcome following cardiac surgery. Stroke following thoracic aortic surgery may be due to emboli or ischemia secondary to prolonged circulatory arrest or a clamp placed close to the origin of the carotid artery.
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The pathophysiology of postoperative strokes following noncardiovascular surgery is less clear but may involve severe sustained hypotension or hypertension. Hypotension with severe hypoperfusion can result in so-called “watershed” zone infarctions or thrombosis of cerebral arteries, whereas hypertension can result in intracerebral hemorrhage (hemorrhagic stroke). Sustained hypertension can disrupt the blood–brain barrier and promote cerebral edema. Perioperative atrial fibrillation can likewise lead to atrial clot formation and cerebral embolism. The ...