Myasthenia Gravis Crisis Management

Algorithm Steps

1. ▶

   Start

   Suspected Myasthenic Crisis

   Patient with MG presenting with worsening weakness or respiratory compromise

   1. ◆

      Decision

      Respiratory Assessment

      Check FVC, NIF, and clinical signs

      • FVC <20 mL/kg = ICU admission
      • FVC <15 mL/kg = consider intubation
      • NIF < -30 cmH2O = respiratory weakness
      • Dyspnea, weak cough, paradoxical breathing
      • Unable to count to 20 in one breath
      1. ●

         Action

         Elective Intubation

         Early intubation preferred over emergent

         • Avoid succinylcholine (unpredictable response)
         • Reduce non-depolarizing NMB dose by 50%
         • Consider awake fiberoptic if bulbar weakness
         • Plan for difficult weaning
         1. ●

            Action

            Identify Crisis Trigger

            Search for precipitating factors

            • Infection (most common - 40%)
            • Medication changes/non-compliance
            • Surgery or anesthesia
            • Drugs: aminoglycosides, β-blockers, fluoroquinolones
            • Taper of immunosuppression
            1. ⚠

               Warning

               ⚠️ Avoid These Medications

               Can precipitate or worsen crisis

               • Aminoglycosides, fluoroquinolones, macrolides
               • Beta-blockers
               • Magnesium sulfate
               • Neuromuscular blocking agents
               • Statins, IV contrast (iodinated)
            2. ◆

               Decision

               Select Immunomodulatory Treatment

               IVIG vs Plasma Exchange (PLEX)

               • Both equally effective (Class I evidence)
               • PLEX: faster response (2-3 sessions)
               • IVIG: response in 2-3 weeks
               • Choose based on availability and urgency
               1. ●

                  Action

                  IVIG

                  Intravenous Immunoglobulin

                  • 2 g/kg total dose over 2-5 days
                  • Pre-treat: acetaminophen, diphenhydramine
                  • Monitor for aseptic meningitis, renal failure
                  • Contraindicated: IgA deficiency
                  1. ●

                     Action

                     Manage Cholinesterase Inhibitors

                     Consider holding pyridostigmine in crisis

                     • May hold during intubation (secretions)
                     • Risk of cholinergic crisis if excessive
                     • Restart at lower dose when improving
                     • 60 mg PO q4-6h typical maintenance
                     1. ●

                        Action

                        Corticosteroids

                        Initiate with caution in crisis

                        • Can cause transient worsening first 2 weeks
                        • Start low and titrate: prednisone 10-20 mg/day
                        • Or high-dose after IVIG/PLEX initiated
                        • Target: 1 mg/kg/day (max 100 mg)
                        1. ✓

                           Outcome

                           Clinical Improvement

                           Wean vent support, transfer from ICU

                           • Continue immunotherapy
                           • Optimize long-term immunosuppression
                           • Consider thymectomy if indicated
                        2. ⚠

                           Warning

                           Refractory Crisis

                           Consider additional interventions

                           • Repeat IVIG or PLEX
                           • Rituximab or eculizumab
                           • Prolonged mechanical ventilation
                           • Neuromuscular specialist consultation
               2. ●

                  Action

                  Plasma Exchange (PLEX)

                  Plasmapheresis

                  • 5 exchanges over 7-10 days
                  • 1.0-1.5 plasma volumes per exchange
                  • Requires central venous access
                  • Avoid in hemodynamic instability, sepsis
                  • Improvement by 2nd-3rd session
      2. ●

         Action

         ICU Monitoring

         Serial respiratory assessments

         • Check FVC/NIF every 2-4 hours
         • Continuous pulse oximetry
         • Aspiration precautions
         • HOB elevated 30-45°