Myasthenic Crisis



Monitoring


  • IF IN ANY DOUBT, GO SEE THE PATIENT!!!
  • Monitor respiratory parameters every few hours.
    • NIF (it should be more negative than -30 in general)
    • Vital cap (concerning when <10-12 mg/kg)
    • Other ways to assess respiratory status
      • Quality of cough
      • Ability to count out loud in one breath
    • These are partially driven by patient effort, so use these in combination. No single number or sign can substitute for a good exam and your general impression.


Time to move to the ICU?

  • If you are worried about the patient's respiratory status at all, get them to the ICU. Myasthenia gravis patients can crash quickly and without much warning!
  • Do NOT rely on the O2 sat or ABG to predict a crash. This may not change until it is too late!
  • Consider BiPAP in ICU to try to avoid need for intubation.


Work-up

  • Perform infectious work-up for every myasthenic crisis with:
    • Blood cultures
    • Urine cultures
    • CXR
  • Consider non-contrast chest CT for thymoma


Treatment

  • Acetylcholinesterase Inhibitors
    • Pyridostigmine (Mestinon and Mestinon Timespan (extended release))
      • Symptomatic treatment only.
      • Unnecessary in intubated patients; in fact, increase secretions.
      • You can provide mestinon, but not mestinon timespan, via dobhoff
      • Conversion of PO pyridostigmine:IV pyridostigmine is 30:1
  • Glycopyrrolate (Robinul) to decrease secretions
  • Steroids
    • High dose steroids can initially cause worsening! But later can help suppress immune response.
    • If already intubated, start high dose steroids (prednisone 60 mg PO qAM or solu-medrol 500 mg IV qAM)
  • IVIg
    • Used acutely in crisis or for maintenance
    • Typical load for MG
      • If old, renal insufficiency, or severe cardiac disease & hypertension: 0.5 gram/kg over 4 days
      • If young and no renal or cardiac disease: 1 gm/kg daily x 2 days
    • If the patient has known renal disease and you must use IVIg:
      • Use the lysine based Gammagard formulation
      • Avoid concurrent use of nephrotoxic medications
      • Avoid concurrent IV contrast
      • Aggressively hydrate the patient during IVIg treatments
  • Plasmapheresis
    • Used acutely in crisis or for maintenance
    • QOD x 5 treatments, and then reevaluate for need for further series
    • See AIDP section for more information on apheresis.
  • Other immunosuppressants for maintenance
    • Mycofenolate mofetil (Cellcept)
    • Azathioprine (Imuran)


Drugs to Avoid in Myasthenia Gravis



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