Myotonic Dystrophy 

 

 

Background

 

  • Clinically & genetically heterogeneous disorder with two major forms: type 1 (DM1) & type 2 (DM2)

  • Multisystem disorder characterized by skeletal muscle weakness & myotonia, cardiac conduction abnormalities, cataracts, testicular failure, hypogammaglobulinemia, & insulin resistance

 

 

Considerations 

 

  • Multisystem disease:

    • Airway 

      • Bulbar dysfunction & risk of aspiration

      • Central sleep apnea

    • Respiratory:  

      • Restrictive lung disease (weak respiratory muscles)

      • Possible pulmonary hypertension

      • ↓ ventilatory response to hypoxia/hypercarbia

    • Cardiac:

      • Cardiomyopathy

      • Dysrhythmias & heart blocks

    • GI:

      • Delayed gastric motility

    • Endocrine:

      • Hypothyroid, diabetes mellitus, adrenal insufficiency

  • Altered sensitivity to anesthetic agents:

    • Succinylcholine contraindicated due to risks of hyperkalemia & myotonic contractures

    • Sensitivity to CNS depessants (propofol, opioids, benzodiazepines, barbiturates)

    • Cholinesterase inhibitors may trigger myotonic contracture, don't use neostigmine!

  • Risk of perioperative myotonic crisis:

    • Triggers:

      • Drugs (e.g., succinylcholine, neostigmine)

      • Surgical manipulation, electrocautery, nerve stimulator

      • Hypothermia/shivering

    • Treatment:

      • Phenytoin, procainamide, quinine, IM lidocaine, ↑ volatile anesthetic

        • Phenytoin/procainamide: 18mg/kg over 20 min

        • Quinine 300-600mg IV

      • Muscle relaxants & IV anesthetics do NOT work

 

 

Goals/Optimization  

 

  • If elective, multidisciplinary discussion regarding plans for surgery 

  • Prevent aspiration, administer aspiration prophylaxis 

  • Avoid hemodynamic instability

  • Avoid precipitants of myotonic crisis & treat if required

  • Arrange appropriate disposition (need for post-operative monitoring, ventilation)

 

 

Conflicts 

 

  • Need to prevent aspiration (RSI) vs contraindication to succinylcholine & high dose rocuronium (as reversal with neostigmine contraindicated) 

 

 

Pregnancy 

 

  • High risk pregnant patient: ↑ muscle weakness/myotonia, heart failure, uterine atony, postpartum hemorrhage

  • Neuraxial anesthesia is preferred for labor & vaginal or cesarean delivery