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KEY CONCEPTS

KEY CONCEPTS

  • Image not available. Weakness associated with myasthenia gravis is due to autoimmune destruction or inactivation of postsynaptic acetylcholine receptors at the neuromuscular junction, leading to reduced numbers of receptors and degradation of their function, and to complement-mediated damage to the postsynaptic membrane.

  • Image not available. Patients who have myasthenia gravis with respiratory muscle or bulbar involvement are at increased risk for pulmonary aspiration.

  • Image not available. Many patients with myasthenia gravis are exquisitely sensitive to nondepolarizing neuromuscular blockers (NMBs).

  • Image not available. Patients who have myasthenia gravis are at risk for postoperative respiratory failure. Disease duration of more than 6 years, concomitant pulmonary disease, a peak inspiratory pressure of less than –25 cm H2O (ie, –20 cm H2O), a vital capacity less than 4 mL/kg, and a pyridostigmine dose greater than 750 mg/d are predictive of the need for postoperative ventilation following thymectomy.

  • Image not available. Patients with Lambert–Eaton myasthenic syndrome and other paraneoplastic neuromuscular syndromes are very sensitive to both depolarizing and nondepolarizing NMBs.

  • Image not available. Respiratory muscle degeneration in patients with muscular dystrophy interferes with an effective cough mechanism and leads to retention of secretions and frequent pulmonary infections.

  • Image not available. Degeneration of cardiac muscle in patients with muscular dystrophy is also common, but results in dilated or hypertrophic cardiomyopathy in only 10% of patients.

  • Image not available. Succinylcholine should be avoided in patients with Duchenne or Becker muscular dystrophies because of unpredictable response and the risk of inducing severe hyperkalemia or triggering malignant hyperthermia.

  • Image not available. Anesthetic management in patients with periodic paralysis is directed toward preventing attacks. Perioperative management must include frequent determinations of plasma potassium concentration and correction of abnormal values, with careful electrocardiographic monitoring to detect arrhythmias.

  • Image not available. In patients with periodic paralysis, the response to NMBs is unpredictable, and neuromuscular function should be carefully monitored during their use. Increased sensitivity to nondepolarizing NMBs is particularly apt to be encountered in patients with hypokalemic periodic paralysis.

Neuromuscular diseases are disorders that adversely affect muscle function either primarily or via nerve or neuromuscular junction abnormalities. They include myasthenia gravis; Lambert–Eaton syndrome; amyotrophic lateral sclerosis (ALS, or Lou Gehrig disease); Becker, Duchenne, facioscapulohumeral, and myotonic muscular dystrophies; Charcot–Marie–Tooth disease; polymyositis; and a large number of other pathological conditions. Although relatively uncommon, patients with these diseases will present to the operating room and to non–operating room procedure areas for diagnostic studies, treatment of complications, or procedural management of related or unrelated disorders, and may also be evaluated and managed by anesthesia providers in the emergency department, intensive care unit, and on hospital wards. Overall debility, with diminished respiratory muscle strength and increased sensitivity to neuromuscular blockers (NMBs), predisposes these patients to postoperative ventilatory failure and pulmonary aspiration, and may slow their post-procedure recovery because of difficulty with ambulation and increased risk of falling. Cardiac involvement may include cardiomyopathy or dysrhythmias. A basic understanding of the major disorders and their potential interaction with anesthetic agents is necessary to minimize the risk of perioperative morbidity. In addition, inherited or acquired neuromuscular pathology must be considered in ...

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