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Perioperative Management of Neuromuscular Disorders

Practice Essentials

The term neuromuscular disorder encompasses a number of different disease processes, including myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD), and hypokalemic periodic paralysis. Each of these conditions has its own characteristics and specific anesthetic considerations; however, there are certain shared considerations, most notably the concern regarding perioperative respiratory complications associated with the administration of neuromuscular blocking agents.

 Key points in the management of these disorders in the perioperative setting include the following:

MG is an autoimmune disorder that leads to fatigable skeletal muscle weakness with repeated movements. Although symptoms are often mild, more severe symptoms may increase the risk of perioperative respiratory complications, including aspiration and the need for prolonged postoperative intubation and ventilation. To reduce this risk, MG patients should be medically optimized before elective surgery.

Patients with MG are unpredictably resistant to the effects of succinylcholine and unpredictably sensitive to the effects of nondepolarizing neuromuscular blocking agents. If possible, avoidance of nondepolarizing agents during general anesthesia is beneficial. If such agents are necessary, reversal with
sugammadex sodium may make postoperative ventilator support less likely to be required. Sugammadex sodium is a selective relaxant binding agent that forms a complex with the neuromuscular blockers rocuronium and vecuronium for more rapid reversal.

LEMS is an autoimmune disorder most commonly associated with small cell lung carcinoma (ie, paraneoplastic syndrome). It is characterized by skeletal muscle weakness that improves with activity. Patients with LEMS are unpredictably sensitive to the effects of both depolarizing and nondepolarizing neuromuscular blocking agents. If possible, avoidance of neuromuscular blocking agents is recommended to reduce the patient’s risk of requiring postoperative ventilator support. Therefore, the choice of neuromuscular blocking agents should be seriously considered, and these agents should be used only when absolutely necessary. 

DMD is an X-linked recessive hereditary disorder characterized by progressive muscle fiber degeneration and weakness. DMD patients are at risk for the development of restrictive lung disease, dilated cardiomyopathy, mitral regurgitation, and recurrent pulmonary infections secondary to aspiration.

A trigger-free anesthetic (ie, one free of volatile agents and
succinylcholine) may be preferable for DMD patients, in that these patients may be at increased risk for the development of
malignant hyperthermia. Succinylcholine can also cause marked transient hyperkalemia through the upregulation of extrajunctional nicotinic acetylcholine receptors.

Patients with DMD are unpredictably sensitive to the effects of nondepolarizing neuromuscular blocking agents. Avoidance of these agents is preferred if possible. If nondepolarizing agents are necessary, reversal with sugammadex may make postoperative ventilation less likely to be needed.

Hypokalemic periodic paralysis is a rare, autosomal dominant hereditary disorder characterized by transient episodes of skeletal muscle weakness/paralysis when the serum potassium level decreases. The carbonic anhydrase inhibitor 
dichlorphenamide is indicated for long-term treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants. These episodes can be precipitated by number of exacerbating factors, including but not limited to stress, hypothermia, hyperglycemia, respiratory and/or metabolic alkalosis, and infection. Avoidance of these factors perioperatively can reduce the risk of an episode.

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