Myotonic Dystrophy
Background
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Clinically & genetically heterogeneous disorder with two major forms: type 1 (DM1) & type 2 (DM2)
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Multisystem disorder characterized by skeletal muscle weakness & myotonia, cardiac conduction abnormalities, cataracts, testicular failure, hypogammaglobulinemia, & insulin resistance
Considerations
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Multisystem disease:
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Airway
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Bulbar dysfunction & risk of aspiration
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Central sleep apnea
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Respiratory:
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Restrictive lung disease (weak respiratory muscles)
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Possible pulmonary hypertension
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↓ ventilatory response to hypoxia/hypercarbia
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Cardiac:
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Cardiomyopathy
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Dysrhythmias & heart blocks
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GI:
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Delayed gastric motility
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Endocrine:
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Hypothyroid, diabetes mellitus, adrenal insufficiency
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Altered sensitivity to anesthetic agents:
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Succinylcholine contraindicated due to risks of hyperkalemia & myotonic contractures
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Sensitivity to CNS depessants (propofol, opioids, benzodiazepines, barbiturates)
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Cholinesterase inhibitors may trigger myotonic contracture, don't use neostigmine!
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Risk of perioperative myotonic crisis:
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Triggers:
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Drugs (e.g., succinylcholine, neostigmine)
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Surgical manipulation, electrocautery, nerve stimulator
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Hypothermia/shivering
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Treatment:
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Phenytoin, procainamide, quinine, IM lidocaine, ↑ volatile anesthetic
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Phenytoin/procainamide: 18mg/kg over 20 min
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Quinine 300-600mg IV
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Muscle relaxants & IV anesthetics do NOT work
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Goals/Optimization
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If elective, multidisciplinary discussion regarding plans for surgery
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Prevent aspiration, administer aspiration prophylaxis
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Avoid hemodynamic instability
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Avoid precipitants of myotonic crisis & treat if required
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Arrange appropriate disposition (need for post-operative monitoring, ventilation)
Conflicts
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Need to prevent aspiration (RSI) vs contraindication to succinylcholine & high dose rocuronium (as reversal with neostigmine contraindicated)
Pregnancy
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High risk pregnant patient: ↑ muscle weakness/myotonia, heart failure, uterine atony, postpartum hemorrhage
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Neuraxial anesthesia is preferred for labor & vaginal or cesarean delivery