Stroke can be a devastating sequela of the perioperative period. Patients who suffer a stroke during or after noncardiac, nonneurologic surgery have an eightfold increased risk of mortality (1). Patients who suffer a stroke during or after cardiac or major vascular surgery have a mortality rate of up to 38% (2). The morbidity associated with perioperative stroke is equally, if not more staggering. Twenty-two percent of patients who have a cerebrovascular insult, perioperatively or otherwise, will have some sort of deficit 5 years later (3). Fortunately, the incidence of perioperative stroke is relatively low (0.05% to 0.7%) in nonneurosurgical, noncardiac patients (1,4,5). However, the high mortality and burden of morbidity associated with these events makes it imperative that at-risk patients are identified preoperatively so that risk-reduction steps may be taken.

Historically, three risk factors for perioperative stroke have been identified:

Other risk factors are shown in Table 5.1.

Patients with preexisting cerebrovascular disease are at a greater risk for perioperative stroke. With an aging population and advances in stroke treatment, patients who have suffered a cerebrovascular event increasingly present for unrelated surgery. How long to wait between an acute cerebrovascular event and unrelated elective surgery is uncertain. Cerebral autoregulation can be altered following an ischemic event, and it is unclear how long it takes for regulatory mechanisms to normalize. Smaller studies have shown no clear correlation between the temporal relationship of a stroke and increased risk in the perioperative period (7). Larger studies suggest higher risk of adverse events in patients undergoing surgery within 9 months of a stroke (8). The balance between safety concerns and the requirement for surgery is best managed with collaboration of the neurologist, surgeon, anesthesiologist, and the patient (9).

The type of surgery is considered when risk-stratifying patients, as various surgeries are associated with differing incidence of stroke. Cardiac surgery, especially valve repair or replacement, carries the highest risk of perioperative stroke. Table 5.2 lists surgeries and their associated incidence of stroke.

Preanesthetic evaluation of patients with cerebrovascular disease focuses on the cause and timing of any previous strokes or TIAs. Symptoms at the time of the event and any residual deficits such as weakness, dysarthria, and vision changes are noted. An echocardiogram, if not previously done, should be obtained to evaluate for cardioembolic sources, arrhythmias, intracardiac shunts, or valvular pathology. Any previously obtained imaging of the head and neck, including any carotid studies, should also be reviewed. Physical examination includes a basic neurologic examination with careful documentation of any deficits. Auscultation and palpation of the carotid arteries is performed to evaluate for bruits. The presence of a bruit in the setting of neurologic symptoms warrants further evaluation.

Patients with symptomatic carotid disease, or those with a history of stroke or TIA with flow-limiting carotid stenosis as a causative contributor, should avoid unrelated elective surgery until the carotid disease is addressed (see Chapter 5.2). A majority of guidelines recommend intervention such as endovascular stenting or open endarterectomy to restore flow prior to unrelated elective surgery (11). Many of these guidelines are based upon studies with patients initially enrolled decades ago. However, vast improvements in medical management have been made in that time period. These advances are not accounted for in many guidelines, and CEA or angioplasty and stenting continue to be the standard for those with symptomatic carotid disease. Recent evidence suggests that endovascular treatment may have a higher risk of adverse events when compared to endarterectomy (12), although this approach may still be preferable to an open approach for numerous other reasons.

A unique subset of patients with cerebrovascular disease are those with Moyamoya. Moyamoya is a rare vasculopathy in which patients have a progressive narrowing of their distal internal carotid arteries and/or the proximal branching vessels leading to significant stenosis or complete occlusion. The formation of many fine collateral vessels around the stenotic lesion leads to a unique appearance on imaging prompting the disease’s name. Pathophysiology and causation of the disease remain elusive. A minority of cases are associated with other systemic pathology, such as sickle cell or neurofibromatosis, and termed “Moyamoya syndrome” (13). A majority of patients present with TIA symptoms or overt ischemic stroke, although hemorrhagic stroke from rupture of the weak collateral vessels can occur (13). These patients may have preexisting deficits such as aphasia or hemiparesis. Treatments such as antiplatelet agents and surgical revascularization are aimed at reducing rates of future stroke, although success in this regard has proven to be modest (14,15).

Patients with preexisting cerebrovascular disease are often placed on an anticoagulation regimen for risk reduction. The AHA recommends patients with a history of noncardioembolic stroke be placed on an antiplatelet drug to mitigate risk of recurrence (16). Antiplatelet agents have equivalent efficacy when compared to vitamin K antagonists but with fewer side effects (16). Aspirin remains the most common agent; however, other antiplatelet agents are increasingly being used. The combination of aspirin and other antiplatelet agents for stroke risk mitigation has a higher risk of bleeding complications than aspirin alone (16). Similarly, the addition of a vitamin K antagonist to an antiplatelet agent may have added risk without added efficacy in comparison to a single antiplatelet agent. Observational studies suggest that antiplatelet agents may be protective against perioperative stroke when patients undergo cardiac surgery (17,18), but there is little evidence of such protection for noncardiac
surgery. The POISE-2 trial suggests there are no beneficial effects of antiplatelet agents for stroke prevention in patients undergoing nonneurologic, noncardiac surgery, and there may be an increased risk of bleeding (19). A discussion with the prescribing provider and surgeon before surgery regarding risks and benefits of continuing antiplatelet agents and anticoagulants in the perioperative setting is ideal but not always feasible. Patients undergoing procedures with a low risk of bleeding, such as minor dental, dermatologic, or ophthalmologic procedures or endoscopies, may safely continue their antithrombotic agents in the perioperative period. Procedures considered moderate or high risk—most notably cardiac, thoracic, intra-abdominal, or neurosurgical procedures—will likely require cessation of antithrombotic agents to mitigate risk of periprocedural bleeding. Cessation with or without bridging with LMWH or UFH should take into account the individual patient’s risk for incurring thromboembolism. Those with a CHA₂DS₂VASc score of >2, a stroke/TIA or VTE within the previous 3 months, or those with genetic predisposition to thromboembolism are considered higher risk (20). Ultimately, the risk of thromboembolism needs to be weighed against the risk of periprocedural bleeding. As the antithrombotic effects of many of these agents are prolonged, the decision to stop an agent may need to be made several days prior to the scheduled procedure. See Chapters 18.2 and 18.3 for further discussion of perioperative anticoagulant use.

The discovery of a previously undocumented carotid bruit on a preanesthetic physical examination is not uncommon. The presence of a bruit does not necessarily indicate that a patient has significant flow-limiting carotid lesions (as few as 40% do) but should certainly prompt the examiner to perform a more focused history. The patient may not realize or report neurologic symptoms; a detailed history and examination may uncover unrealized indicators of pathology. If a patient is truly asymptomatic and has no history of TIA or stroke, then the risk of perioperative stroke is fairly low and the case can proceed without further workup (1). The Framingham study indicated that the risk of stroke in patients with asymptomatic carotid stenosis, even if hemodynamically significant, is 1% to 2% annually, and there is little to no evidence indicating that patients with asymptomatic carotid stenosis are at a greater risk for perioperative stroke when having noncardiac, nonneurologic surgery (2). Pre-existing cerebrovascular disease (including stenosis of one or both carotid arteries) has been shown to be a significant risk factor for perioperative stroke in patients having cardiac surgery (3).

Atheromatous plaques are focal thickenings of the intima consisting of a variety of constituents including fat-laden immune cells, debris, and connective tissue. A core of free lipid droplets and foam cells is surrounded by a thin, smooth muscle cap. Infiltration of the lesion by immune cells from circulating blood occurs constantly, and the activation of these immune cells, with resultant release of proinflammatory cytokines, may play an important role in the natural history of plaque growth and rupture. Erosion of the endothelium or rupture of the cap exposes the prothrombotic material to circulating platelets and leads to thrombosis, which is now widely accepted as the main cause of distal ischemia.

Classically, at least since the 1995 asymptomatic carotid atherosclerosis study (4) and the 2004 European Asymptomatic Carotid Surgery Trial (5), the degree of carotid stenosis has driven the recommendation for surgical intervention based on these studies’ findings of statistically significant improvements in outcomes after CEA in patients with a certain degree of asymptomatic stenosis when compared to medical management. Numerous studies of varying degrees of quality have since been published in contrast or in agreement with this management algorithm. Proponents of medical management of asymptomatic carotid stenosis point out that the introduction and implementation of new drugs have decreased the incidence of stroke and that the risk of perioperative stroke is higher than the risk of annual stroke while being medically managed. Conversely, proponents of prophylactic CEA for asymptomatic, but significant, carotid stenosis argue that 30-day stroke risk after CEA is declining with improved surgical methodology. Additional large-scale trials are needed if updates to current recommendations are to occur. Until then, the management of patients with asymptomatic carotid disease will likely remain controversial.

Ultimately, the type of planned surgery dictates if a provider should investigate the presence or degree of carotid stenosis if a bruit is discovered. Patients having cardiac or vascular surgery are at greatest risk of perioperative stroke in the presence of significant carotid disease and may benefit from further evaluation before elective surgery. Further workup may be warranted if the surgery is expected to have large hemodynamic variability, if the head and neck are to be manipulated to a great extent, or if positioning may compromise cerebral blood flow (e.g., sitting position).

Bruits associated with symptomatic carotid disease need to be investigated. Numerous imaging modalities can elucidate the degree of stenosis and the amount of hemodynamic significance associated with stenotic plaques. Carotid arteriography remains the gold standard in evaluation of stenotic lesions but is invasive and not without risk. Advances in technique and equipment have made carotid ultrasound with Doppler imaging an acceptable first-line study despite questionable accuracy in determining degree of stenosis and inability to image intracranial circulation. See Chapter 5.1 for more information on patients with cerebrovascular disease.

The incidence of cerebral aneurysms is 3.2% in adults worldwide. Only 0.25% of these will have a rupture in the future (1). Unruptured aneurysms are usually found incidentally in patients presenting with symptoms other than hemorrhage. In ruptured aneurysms, which result in a subarachnoid hemorrhage (SAH), 80% of patients complain of the worst headache of their life. Other signs of SAH include nausea, vomiting, photophobia, neck pain, and loss of consciousness. Up to 10% to 43% of patients will have a sentinel headache, days to weeks before rupture (2,3). SAH has significant morbidity with a mortality rate of 20% to 40%. About half of SAH survivors have a significant reduction in health-related quality of life (4). SAH during pregnancy most commonly occurs in the postpartum period and is less likely to be caused by aneurysms, when compared to nonparturients (5).

The goals of treatment are to prevent rupture and subsequent hemorrhage or re-hemorrhage in ruptured aneurysms. This can be accomplished by microvascular clipping or endovascular coiling. Many studies show that endovascular coiling, when compared to surgery, reduces procedural morbidity and mortality in unruptured aneurysms but also has a higher recurrence rate (1,6,7,8). The complete obliteration rate of coiling is much lower when compared to clipping. Endovascular management is more difficult in patients with aberrant anatomy (3). Ruptured aneurysms can be treated by either approach, but endovascular coiling tends to be the primary therapy. This is especially true for elderly patients and poor-grade SAH.

Cerebral AVM consist of a tangle of abnormal vessels, referred to as a nidus, connecting the high-pressure arterial system to the low-pressure venous system. AVM is the most common etiology of intracranial hemorrhage in young patients and a typical presentation includes hemorrhage (50%), seizures, and neurologic deficits. The risk of ruptured AVM is approximately 2% to 4% per year (9). Treatment approaches to AVM include surgical removal, endovascular embolization, and stereotactic radiosurgery, all depending on the location, size, and whether or not there is a hemorrhagic presentation (10).

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies which attack the postsynaptic acetylcholine receptor at the neuromuscular junction. The incidence and prevalence of MG has increased, doubling in the past decade, likely the result
of improvements in epidemiologic methodology, overall patient care, and increased life expectancy (1). Patients usually present with proximal muscle weakness, which is alleviated by rest and exacerbated by activity. Up to 60% of patients present with diplopia, ptosis, or both (2). Bulbar muscles may be impaired and result in dysphagia or dysarthria. Table 5.3 shows the accepted classification based on the severity of the disease and clinical presentation of MG.

There are medical and surgical treatment options for MG. Pyridostigmine, which is a cholinesterase inhibitor, is considered first-line therapy. If patients continue to be symptomatic, glucocorticoids are added to the medical regimen. Immunosuppressive agents (azathioprine, mycophenolate mofetil, methotrexate, cyclosporine, and rituximab) are used when patients do not respond to current therapy, if glucocorticoid doses are excessive, or patients are unable to tolerate side effects of current regimen. Immunosuppressive agents are considered as an earlier intervention for patients with diabetes mellitus, osteoporosis, ischemic heart disease, or patients with continued significant bulbar and muscle weakness. In patients with severe bulbar and respiratory compromise, intravenous immunoglobulin (IVIG) is recommended. Plasma exchange is preferred if the risk factors (renal insufficiency, thrombotic events, and IgA deficiency) associated with anaphylaxis and IVIG are a concern (3). IVIG has comparable efficacy and duration of effect to plasma exchange (4). Thymectomy is a surgical option for patients with thymomas who are younger than 45 years old and have positive serum anti-AchR antibody. However, the benefit of this surgery is controversial in patients with nonthymomatous ocular MG (2,3).

Myasthenic patients with muscle weakness and respiratory insufficiency may be experiencing a myasthenic crisis (an exacerbation of the disease) or a cholinergic crisis (caused by cholinesterase inhibitor overdose). In a cholinergic crisis, autonomic symptoms, such as bronchospasm, sialorrhea, bronchorrhea, and diarrhea, may be present in addition to muscle weakness. Administering a single small dose of edrophonium can help distinguish myasthenic crisis from cholinergic crisis. Symptoms will show improvement in patients with myasthenic crisis, whereas symptoms will worsen in patients with cholinergic crisis (5).

Amyotrophic lateral sclerosis (ALS) is a progressive and incurable disease characterized by degeneration, dysfunction, and eventual paralysis of upper and lower motor neurons. It is sometimes referred to by the eponym Lou Gehrig disease, for the New York Yankees baseball player who succumbed to ALS at the age of 37. The underlying etiology of ALS is not clear (1). While most cases are sporadic, 5% to 10% are familial. The diagnosis is made clinically by evaluating for upper and lower motor neuron dysfunction in multiple motor groups (see Table 5.6) (2,3).

The signs and symptoms at onset and the patterns of disease progression are variable. The median time of survival after diagnosis is 3 to 5 years. Death typically results from ventilatory failure due to neuromuscular weakness. Riluzole is the only medication approved for disease modification, rather than palliation of symptoms. Its exact mechanism of action is debated, but clinical trials show modest improvement of survival time.

Patients with ALS are best served by a multidisciplinary team (neurology, pulmonology, palliative care, nutrition, social work, and physical, occupational, respiratory, and speech therapy) experienced in ALS care (4). This is also true when planning for a surgical procedure. Preoperative assessment of the ALS patient begins with characterization of the surgical plan. Advancing disease may require palliative procedures such as placement of feeding tubes or tracheotomy. Surgery may be tangentially related to the disease (long bone fracture after a fall) or not disease related (appendectomy). Context allows the anesthesiologist to prioritize further evaluation or consultation and discuss the risks and benefits of the anesthetic options. Elective and semielective procedures should be scheduled as early in the disease process as possible. Progressive muscular weakness increases risk for aspiration and can cause exquisite sensitivity to the respiratory depressants utilized perioperatively.

The history focuses on disease trajectory, current and previous physical status, ventilatory reserve, signs and symptoms of nocturnal hypoventilation, and aspiration risks. The patient is assessed for ALS-plus syndrome where the stereotypical upper and lower motor neuron findings coexist with parkinsonism, progressive supranuclear palsy, and (importantly) autonomic instability and dysfunction (5). Evaluation of the airway assesses and documents oral aperture, jaw mobility, and range of motion of the neck. Inability to elevate the palate or protrude the tongue affects the Mallampati score. Masseter spasticity can lead to severe trismus. Muscular laxity may lead to recurrent temporomandibular dislocations. Longstanding weakness of the neck extensors can lead to anterocollis, and spasticity can cause torticollis.

Ideally, individuals with ALS will have serial ventilatory assessments, starting at the time of diagnosis. ALS specialists typically monitor patients with pulmonary function tests and tests of neuromuscular strength, including upright and supine forced vital capacity (FVC) and maximum inspiratory and expiratory pressures. An FVC <50% of predicted is a marker for early ventilatory failure and need for chronic support (6). Updated studies should be done if there has been a significant change in symptoms. If indicated, the patient should be initiated on noninvasive positive pressure ventilation (NIPPV) before surgery. Patients with coexisting cardiac disease who are now physically limited need optimization of medical regimens. It is highly unlikely that additional testing is indicated given patients’ prognosis and typical life expectancy.

Preoperative laboratory work is guided by the patient’s comorbidities. An electrolyte panel and assessment of renal function is reasonable if the patient has severely impaired swallowing, weight loss, and is at risk for dehydration. Creatine phosphokinase is typically elevated due to chronic muscle wasting and should not raise concerns for myocardial injury.

Having trusted family members or friends present for the preoperative visit is useful for many reasons. Patients with advanced disease (or bulbar-predominant presentation) may have reduced verbal ability due to oropharyngeal weakness or dysarthria. Some individuals utilize writing pads or electronic devices for communication but many have self-developed shorthand codes (blinking, tapping), which close confidants are skillful at interpreting. Additionally, while traditional teaching describes
ALS as a pure motor disorder, cognitive changes are common. Many individuals with ALS demonstrate frontotemporal executive dysfunction, and a small percentage will develop frontotemporal dementia (7). Patients with ALS often have strong preferences about end-of-life care, intubation, and resuscitation. Involving family in complex discussions is ideal. Engaging the patient and his or her medical power of attorney in a dynamic discussion about mechanical ventilation when sedation and general anesthesia are under consideration is an essential part of the preoperative visit.