Summary
Neuromuscular and collagen vascular diseases comprise a wide array of disorders that bear a broad range of implications for anesthetic management throughout the perioperative period. Thorough preanesthetic evaluation is essential, with focus on the airway, pulmonary, and cardiovascular systems paramount, in addition to close attention to anticipated special positioning needs intraoperatively. Specific anesthetic medications may be contraindicated in some conditions, and a number of these patients may require perioperative glucocorticoid supplementation due to chronic steroid use. Some patients are susceptible to postoperative cardiopulmonary compromise and may require increased or extended postoperative monitoring.
Introduction
Neuromuscular and collagen vascular diseases comprise a wide array of disorders that bear a broad range of implications for anesthetic management throughout the perioperative period. Thorough preanesthetic evaluation is essential, with focus on the airway, pulmonary, and cardiovascular systems paramount, in addition to close attention to anticipated special positioning needs intraoperatively. Specific anesthetic medications may be contraindicated in some conditions, and a number of these patients may require perioperative glucocorticoid supplementation due to chronic steroid use. Some patients are susceptible to postoperative cardiopulmonary compromise and may require increased or extended postoperative monitoring.
Tables 21.1 and 21.2 summarize the principal perioperative anesthetic considerations of neuromuscular and collagen vascular diseases.
Table 21.1 Neuromuscular diseases of importance to anesthesia providers, with principal features and considerations
| Disease | Physical and diagnostic findings | Preoperative considerations | Intraoperative/anesthetic considerations | Postoperative considerations |
|---|---|---|---|---|
| Myasthenia gravis (MG) |
|
|
|
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| Lambert–Eaton myasthenic syndrome (LEMS) |
|
|
|
|
| Guillain–Barré syndrome (GBS) |
|
|
|
|
| Muscular dystrophies and congenital myopathies; Duchenne and Becker muscular dystrophies |
|
|
|
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| Mitochondrial myopathy |
|
|
|
|
PFT, pulmonary function test; GI, gastrointestinal; IVIG, intravenous immunoglobulin; BP, blood pressure; HR, heart rate; CHF, congestive heart failure; NPO, nil per os.
Table 21.2 Collagen vascular diseases of importance to anesthesia providers, with principal features and considerations
| Disease | Physical and diagnostic findings | Preoperative considerations | Intraoperative/anesthetic considerations | Postoperative considerations |
|---|---|---|---|---|
|
|
|
|
|
| Systemic lupus erythematosus (SLE) |
|
|
|
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| Systemic sclerosis (SSc) |
|
|
|
|
| Dermatomyositis (DM) and polymyositis (PM) |
|
|
|
PFTs, pulmonary function tests; IV, intravenous; ICU, intensive care unit.
Neuromuscular Diseases
Myasthenia Gravis
Myasthenia gravis (MG) is an autoimmune disorder that results from antibody formation against either acetylcholine receptors (75% of cases) or related macromolecules known as muscle-specific kinase or lipoprotein receptor-related protein (remaining cases). The antibodies result in complement-mediated degradation of the target receptors or proteins, leading to impaired neuromuscular transmission in striated muscle [Reference Cata, Lasala and Williams1]. Women are more often affected in young adulthood, whereas men are more likely affected in later decades. Patients with MG may have generalized or localized weakness that typically improves with rest, and in >50% of patients, there are ocular or other bulbar findings such as diplopia and ptosis [Reference Turakhia, Barrick and Berman2]. Although several classification schemes have been devised over the years, currently, the model of the Myasthenia Gravis Foundation of America that recognizes five groups according to the severity of symptoms is widely employed [Reference Cata, Lasala and Williams1].
Physostigmine, a cholinesterase inhibitor in the same drug class as neostigmine, is the primary medical treatment as it acts to increase the concentration of acetylcholine at the neuromuscular junction (NMJ). Due to their effects in attenuating the immune response, corticosteroids may also be employed. Immunosuppressants (e.g., azathioprine, methotrexate, etanercept) are required in some patients, and in the setting of acute disease, patients may require intravenous (IV) immunoglobulins or plasma exchange. Thymectomy, either thoracoscopic or via median sternotomy, is often provided [Reference Turakhia, Barrick and Berman2].
Anesthetic Considerations
Preoperative evaluation should focus on the extent of muscle weakness, particularly involving the bulbar and respiratory muscles, and optimization of medical therapy. The presence of thymoma or thymic hyperplasia and resultant tracheal compression (“mediastinal mass”) should be assessed with CT or MRI. Patients may have cardiac conduction disturbances and signs of autonomic instability, including blood pressure lability and gastroparesis. Patients should be assessed for evidence of other autoimmune and endocrine disorders, including thyroid dysfunction, rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE) [Reference Cata, Lasala and Williams1]. Pyridostigmine should be continued in the perioperative period, including intravenous (IV) administration intraoperatively. Due to high first-pass extraction of orally administered pyridostigmine, a conversion ratio of IV to oral doses of 1:30 is recommended [Reference Turakhia, Barrick and Berman2]. Patients who have been receiving chronic glucocorticoid therapy should receive “stress dose” steroid coverage perioperatively.
Anesthetic management considerations include use of regional anesthetic techniques whenever the nature of the surgical procedure allows, and for general anesthesia, avoidance of neuromuscular blocking agents when practical. Succinylcholine is generally avoided as patients with MG are thought to be relatively resistant to its effects and pyridostigmine would be expected to prolong its duration of action. When nondepolarizing muscle relaxants are required, conventional practice is to employ reduced doses and either no or lengthened redosing intervals. Sugammadex has generally proven successful in reversing nondepolarizing relaxant (rocuronium and vecuronium only) effects in patients with MG, although one case report demonstrated perceived failure of sugammadex to antagonize rocuronium blockade [Reference deBoer, Shields and Booij3, Reference Dos Santos Fernandes, Saraiva Ximenes and Ibanhes Nunes4]. Other medications, such as potent inhalation anesthetics and various antimicrobials, that are known to interfere with neuromuscular function (e.g., ciprofloxacin, erythromycin, aminoglycosides) should be avoided when possible. Total intravenous anesthetic techniques that employ continuous infusions of propofol and short-acting opioids, such as remifentanil, may be ideal [Reference Blichfeldt-Lauridsen and Hansen5].
Postoperatively, patients may require mechanical ventilation and, if extubated, should be monitored for respiratory insufficiency for an extended period. Both myasthenic and cholinergic crises may be encountered postoperatively.
Lambert–Eaton (Myasthenic) Syndrome
Lambert–Eaton syndrome is a rare immune-mediated disease associated with antibodies against the presynaptic calcium channel at the NMJ. It is associated with malignancy in many cases [Reference Turakhia, Barrick and Berman2]. Patients often complain of weakness, which can be mistaken for MG. Of note, patients with Lambert–Eaton syndrome do not respond to anticholinesterases or steroids but do improve with repeated activity [Reference Weingarten, Araka and Mogenson6]. The pathophysiology of Lambert–Eaton syndrome involves a presynaptic defect that interferes with the release of acetylcholine. Patients are particularly sensitive to all neuromuscular blocking agents, and these should be avoided if possible [Reference Katz and Murphy7, Reference Schoser, Eymard and Datt8].
Anesthetic Considerations
Patients with Lambert–Eaton syndrome are sensitive to the effects of both depolarizing and nondepolarizing neuromuscular blockers (NDNMBs). Recovery of neuromuscular function should be closely monitored. The most common and serious perioperative complications are respiratory in nature and some patients might require postoperative mechanical ventilation.
Guillain–Barré Syndrome
Guillain–Barré syndrome (GBS) is an autoimmune disease that is thought to be triggered by viral or bacterial infection [Reference Hughes and Cornblath9]. The infectious agent produces a substance that resembles a host neural component and causes the formation of autoantibodies that attack the host peripheral nervous system. Patients with GBS have antibodies against gangliosides in the peripheral nerves. Most patients with GBS have a history of respiratory or gastrointestinal illness or infection within 4 weeks of the appearance of neurological symptoms [Reference Hughes and Cornblath9, Reference Hocker, Nagarajan and Rubin10]. GBS is characterized by weakness that occurs in an ascending pattern, beginning in the lower extremities and progressing more cephalad. Paresthesias may precede skeletal muscle weakness in some patients.
Anesthetic Considerations
Autonomic nervous system dysfunction may occur with GBS, and stimulation (e.g., direct laryngoscopy, positioning, tracheal intubation, etc.) may lead to drastic and wide changes in heart rate and blood pressure [Reference Jones, Wilmshurst and Sykes11]. Succinylcholine should be avoided in patients with GBS due to the risk of hyperkalemia. Intermediate-acting NDNMBs, such as rocuronium, have been used safely in patients with GBS. The most serious threat to GBS patients is respiratory insufficiency and the need for mechanical ventilation postoperatively.
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