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  • Image not available.The weakness associated with myasthenia gravis is thought to be due to autoimmune destruction or inactivation of postsynaptic acetylcholine receptors at the neuromuscular junction, leading to a reduced number of receptors and loss of folds on 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 blocking agents (NMBAs).
  • Image not available.Patients who have myasthenia gravis are at greatest risk for postoperative respiratory failure. Disease duration of more than 6 years, concomitant pulmonary disease, a peak inspiratory pressure of < –25 cm H2O (ie, –20 cm H2O), a vital capacity < 4 mL/kg, and a pyridostigmine dose > 750 mg/d are predictive of the need for postoperative ventilation following thymectomy.
  • Image not available.Patients with the myasthenic syndrome are very sensitive to both depolarizing and nondepolarizing NMBAs.
  • Image not available.Degeneration of the respiratory muscles in patients with muscular dystrophy interferes with an effective coughing 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 has been used safely in some patients with Duchenne’s and Becker’s muscular dystrophies but is best avoided because of unpredictable responses and the risks of inducing severe hyperkalemia or triggering malignant hyperthermia.
  • Image not available.In patients with periodic paralysis, anesthetic management is directed toward preventing attacks. Careful electrocardiographic monitoring is necessary to detect attacks and arrhythmias during anesthesia.
  • Image not available.In patients with periodic paralysis, the response to NMBAs is unpredictable. Increased sensitivity to nondepolarizing NMBAs is particularly apt to be encountered in patients with hypokalemic periodic paralysis.

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Although neuromuscular disorders are relatively uncommon, patients present to the operating room with some regularity at tertiary medical centers for diagnostic studies, for treatment of complications, or for surgical management of unrelated disorders. Diminished respiratory muscle strength and enhanced sensitivity to neuromuscular blocking agents (NMBAs) predispose these patients to postoperative ventilatory failure. A basic understanding of the major disorders and their potential interaction with anesthetic agents is necessary to avoid postoperative morbidity of this nature.

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Image not available.Myasthenia gravis is characterized by weakness and easy fatigability of skeletal muscle and is classified according to whether the patient has only ocular or ocular and nonocular muscle weakness (Table 37–1). The lifetime prevalence of myasthenia gravis is anywhere between 5 and 40 per 100,000 people. The incidence is about 4–11 per million and is highest in women during their third decade; in men, it typically presents in the sixth and seventh decades. The weakness associated with myasthenia gravis is thought to be due to autoimmune destruction or inactivation of postsynaptic acetylcholine receptors at the neuromuscular junction, leading to a reduced number of receptors and loss of folds on the postsynaptic membrane. Antibodies (IgG) against the nicotinic acetylcholine receptor in neuromuscular junctions are found in 85–90% of patients with generalized myasthenia gravis and up to 50–70% of patients with ocular myasthenia. ...

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