Myotonic dystrophy, intraop mgt

Clinical - Neuromuscular Diseases and Disorders

Myotonic dystrophy (dystrophia myotonica, DM) is a muscular disorder characterized by prolonged contraction and muscle relaxation, progressive muscle weakness, and wasting.  Intraoperative management should aim to avoid triggering myotonia and should take into account that DM patients are at increased risk for the following:

  • Cardiac conduction abnormalities
  • Aspiration
  • Hypersensitivity to anesthetic agents
  • Metabolic abnormalities, including hyperkalemia and hyperglycemia

Specific intraoperative anesthetic considerations with regards to general anesthesia and DM are discussed below.

InductionDM patients have weak pharyngeal musculature and are therefore at greater risk of aspiration.   Ideally, a rapid sequence induction without neuromuscular blockade should be performed.  Avoid succinylcholine; it may induce exaggerated contracture, masseter spasm, laryngospasm, or severe hyperkalemia.  If neuromuscular relaxation is necessary, use shorter-acting agents, such as rocuronium or cis-atracurium.

Maintenance – intravenous or inhalational agents are appropriate; DM patients are no more susceptible to malignant hyperthermia than the general population.  The patient will require deeper anesthesia for akinesia if neuromuscular relaxant is not used.

Emergence – avoid paralytic reversal; neostigmine may exacerbate myotonia.  Prolonged emergence can be expected due to hypersensitivity to anesthetic agents.  Strict extubation criteria should be employed, given the patient’s increased risk of aspiration.  

Environment – hypothermia and shivering can induce myotonia.  Thus, normothermia should be maintained with warm IV fluids and a forced warm air blanket if necessary.

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