Suspected myasthenic crisis (adult)
Known or suspected myasthenia gravis (MG) with rapid worsening of breathing, swallowing or speech. Admit. Involve neurology early. Adults only: for children, get paediatric neurology advice.
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Myasthenia Gravis Crisis Management
Myasthenia Gravis Crisis Management: Suspected myasthenic crisis (adult) → Ventilatory or bulbar failure now? → Failure: intubate early (planned, not cr...
Pathway Overview
15 steps
Algorithm Steps
15 total
01Start 02Decision Ventilatory or bulbar failure now?
Yes if PaCO2 is rising, the patient is tiring, cannot clear secretions or is aspirating. Warning values: FVC below 20 mL/kg, MIP weaker than -30 cmH2O, MEP below 40 cmH2O. Bedside numbers can mislead (facial weakness gives a poor seal), so act on the trend and the clinical picture. SpO2 falls late.
- Warning values: FVC below 20 mL/kg; MIP (NIF) weaker than -30 cmH2O (for example -20); MEP below 40 cmH2O
- Signs: dyspnoea, accessory muscle use, paradoxical breathing, weak cough, cannot count to 20 in one breath
- Bulbar signs: dysphagia, nasal speech, nasal regurgitation, pooled secretions, weak jaw or tongue
- Get arterial or venous blood gas; repeat measures often
- If Yes
03Action Failure: intubate early (planned, not crash)
Ventilatory or bulbar failure: intubate and ventilate in ICU. Do not delay intubation for a non-invasive ventilation (NIV) trial when PaCO2 is rising or bulbar weakness is severe.
- Non-depolarising blockers (rocuronium, vecuronium): MG patients are very sensitive; use a reduced dose and monitor train-of-four
- Suxamethonium (succinylcholine): MG patients are resistant; the response is unpredictable
- If rocuronium is used, have sugammadex available
- Expect prolonged ventilation; prevent atelectasis (physiotherapy, suction, PEEP)
04Action Pyridostigmine: stop while ventilated
Ventilated: stop pyridostigmine (it increases secretions and airway plugging). Restart before weaning. Not ventilated: do not raise the dose to treat crisis; neurologist to decide.
- Excess dose can cause cholinergic crisis: weakness with salivation, sweating, cramps, diarrhoea, bradycardia
- Restart at the usual or a lower dose before weaning
- MuSK antibody MG: often poor response and more side effects
05Warning Stop or avoid drugs that worsen MG
Avoid if a safer choice exists. If one is essential, give it with close respiratory monitoring. Serious infection: do not delay antibiotics; use a safer class that covers the infection. Use with caution: statins, iodinated contrast, phenytoin.
- Antibiotics: aminoglycosides, fluoroquinolones, macrolides (such as azithromycin), telithromycin
- Magnesium sulfate (also in pre-eclampsia), beta-blockers, procainamide, quinine, quinidine
- Immune checkpoint inhibitors, D-penicillamine, botulinum toxin, chloroquine, hydroxychloroquine
06Action Find and treat the trigger; exclude mimics
Infection is the most common trigger. If MG is not confirmed, consider Guillain-Barre syndrome, botulism, Lambert-Eaton syndrome and brainstem stroke.
- Infection: cultures and chest X-ray; treat promptly (aspiration pneumonia is common)
- Recent new drug, missed or reduced immunotherapy, recent surgery, steroid start
- Immune checkpoint inhibitor: check troponin, CK and ECG for myocarditis and myositis; involve oncology
- Check potassium, magnesium and phosphate; replace if low (low levels worsen weakness)
- Too much pyridostigmine (cholinergic crisis): see previous step
07Warning Before PLEX or IVIG: check contraindications
PLEX and IVIG are about equally effective. Choose by comorbidity and access.
- Sepsis or haemodynamic instability: do not use PLEX; use IVIG
- Renal failure, high thrombosis risk, or IgA deficiency with anti-IgA antibodies: avoid IVIG; use PLEX
- Pregnancy: obstetric input; PLEX or IVIG can be used; no magnesium sulfate
08Decision PLEX available now and safe?
Yes if plasma exchange can start without delay and there is no sepsis or haemodynamic instability. PLEX may work a little faster and is preferred in MuSK antibody MG.
- If Yes
09Action PLEX available and safe: plasma exchange
Onset usually within days. Not in sepsis or haemodynamic instability. ACE inhibitor in the last 24-30 hours: tell the apheresis team (risk of flushing and hypotension with albumin); withhold it before PLEX when possible. If IVIG is also needed, give PLEX first (PLEX removes IVIG).
- 1-1.5 plasma volumes per exchange; albumin replacement
- 3-6 exchanges over 10-14 days, daily or alternate days
- Peripheral venous access if possible; a central line adds risk
- Watch for hypotension, line infection and bleeding
10Action Corticosteroids: start once PLEX or IVIG is under way
Steroids can cause early worsening (steroid dip). Start them with PLEX or IVIG running and breathing monitored. Checkpoint inhibitor MG: give high-dose steroids early. Diabetes: expect high glucose.
- Adult: prednisolone or prednisone 30-50 mg once daily, orally or by nasogastric tube, with PLEX or IVIG; neurologist sets the dose
- Checkpoint inhibitor MG: troponin, CK and ECG; oncology and cardiology input
- Monitor glucose and blood pressure; look for infection
- If high doses continue: gastric, bone and Pneumocystis (PJP) prophylaxis per local policy
11Decision Improving after about 1 week?
Judge by bulbar, neck and limb strength, FVC and MIP, and ventilator needs.
- If Yes
12Outcome Improving: wean and plan long-term care
Wean when strength improves (for example FVC above 15 mL/kg). Restart pyridostigmine before weaning. After a crisis, intensify long-term immunotherapy. Consider thymectomy when indicated.
If No13Outcome No improvement after 1 week: refractory crisis, escalate
Neuromuscular specialist to lead. Options: a further course (PLEX then IVIG), very high-dose IV methylprednisolone, or newer agents (rituximab for MuSK antibody MG, complement or FcRn inhibitors). TGA indications and access vary. Complement inhibitors need meningococcal vaccination or antibiotic cover. Plan for prolonged ventilation or tracheostomy.
If No14Action PLEX unavailable or unsafe: IVIG
Onset usually within 1 week. Avoid or take great care in renal failure, high thrombosis risk, and IgA deficiency with anti-IgA antibodies. Australia: myasthenic crisis is an approved indication (BloodSTAR authorisation, neurologist diagnosis); do not delay treatment: ask the blood bank for urgent supply.
- Adult: 2 g/kg total per course (maximum), in divided doses over 2-5 days
- Use the National Blood Authority dose calculator for the dose
- Renal or thrombosis risk: keep hydrated, lowest practicable infusion rate, check creatinine
- Watch for thrombosis, acute kidney injury, fluid overload, haemolysis, aseptic meningitis
- Path rejoins step 10Shared downstream outcome
If No15Action No failure yet: impending crisis, monitor in ICU or HDU
Crisis can follow within hours to days. Keep in ICU or HDU where intubation is available. Hypercapnia or severe bulbar weakness: intubate; do not trial NIV.
- Repeat FVC, MIP and bedside tests often (for example every 2-4 hours) and after any change
- Intubate if PaCO2 rises, breathing work or rate increases, or the patient aspirates
- NIV (BiPAP) may avoid intubation only if PaCO2 is 45 mmHg or less and bulbar function protects the airway
- Swallow unsafe: nil by mouth, head up 30-45 degrees, aspiration precautions
- Path rejoins step 04Shared downstream outcome
Guideline Source
International consensus guidance for management of myasthenia gravis (MGFA Task Force): 2016 executive summary, with 2020 update
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- Adults only; not for juvenile or neonatal MG
- Decisions on intubation, PLEX or IVIG and steroids need neurology and ICU input; bedside respiratory numbers do not reliably predict failure
- Doses are for adults with normal renal function; IVIG and PLEX need local authorisation and access
- Newer agents (complement and FcRn inhibitors) are covered only as specialist options
Contraindicated Populations
Children and adolescents (juvenile MG): paediatric neurology advicePregnancy: obstetric input; no magnesium sulfateImmune checkpoint inhibitor MG: oncology and cardiology input (myocarditis screen)
Applicable Regions
AUUSEUglobal
AU: IVIG needs BloodSTAR authorisation under the National Blood Authority Ig Criteria v3.2 (myasthenic crisis: 1-2 g/kg in 2-5 divided doses; diagnosis by a neurologist). Eculizumab is not TGA-indicated for MG (PNH, aHUS, NMOSD only). TGA-registered as add-on therapy for adult AChR antibody-positive generalised MG: ravulizumab, zilucoplan and efgartigimod; rozanolixizumab also for MuSK antibody-positive MG. These are specialist long-term options, not first-line crisis treatment.
EU: Similar recommendations; access to PLEX varies by centre.
US: IVIG and PLEX are about equally effective; choice depends on comorbidity and availability.
Version 2Next review: 2027-09-30
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Frequently Asked Questions
What is the Myasthenia Gravis Crisis Management?
The Myasthenia Gravis Crisis Management is a emergency clinical algorithm for Neurology. It provides a structured decision tree to guide clinical decision-making, based on International consensus guidance for management of myasthenia gravis (MGFA Task Force): 2016 executive summary, with 2020 update.
What guideline is the Myasthenia Gravis Crisis Management based on?
This algorithm is based on International consensus guidance for management of myasthenia gravis (MGFA Task Force): 2016 executive summary, with 2020 update (DOI: 10.1212/WNL.0000000000002790).
What are the limitations of the Myasthenia Gravis Crisis Management?
Known limitations include: Adults only; not for juvenile or neonatal MG; Decisions on intubation, PLEX or IVIG and steroids need neurology and ICU input; bedside respiratory numbers do not reliably predict failure; Doses are for adults with normal renal function; IVIG and PLEX need local authorisation and access; Newer agents (complement and FcRn inhibitors) are covered only as specialist options. Individual patient factors may require deviation from these recommendations.
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