How should myasthenia gravis be managed preoperatively, including medication adjustments, immunotherapy, and anesthesia precautions?

Preoperative Management of Myasthenia Gravis

Continue pyridostigmine on the day of surgery, optimize disease control preoperatively with corticosteroids or immunotherapy if needed, assess respiratory function with pulmonary function tests (negative inspiratory force and vital capacity), avoid medications that worsen myasthenia, and plan for reduced-dose non-depolarizing muscle relaxants with sugammadex reversal.

Medication Management

Continue Anticholinesterase Therapy

• Pyridostigmine should be continued on the day of surgery 1, 2
• Typical dosing: 30-120 mg PO three to four times daily based on symptoms 1
• Abrupt cessation risks precipitating myasthenic crisis

Optimize Immunosuppression Preoperatively

For patients with moderate to severe disease (MGFA class II or higher):

• Corticosteroids (prednisone 0.5-1.5 mg/kg daily) may be initiated or optimized weeks before elective surgery 1
• Consider 3-4 week steroid course with gradual taper based on symptom improvement 1

Controversial: Preoperative Immunotherapy

The evidence for routine preoperative IVIg or plasmapheresis is mixed and does not support universal use 3:

• Older retrospective studies favored plasmapheresis, but recent randomized trials show no significant benefit in well-controlled patients 3
• Reserve IVIg (2 g/kg over 5 days) or plasmapheresis for high-risk patients only 1, 3
• Both interventions carry notable risks and costs without proven routine benefit 3

Preoperative Assessment

Respiratory Function Evaluation (Critical)

Mandatory preoperative testing 1, 4:

• Negative inspiratory force (NIF)
• Vital capacity (VC)
• These predict postoperative respiratory complications and need for prolonged ventilation

Risk Stratification

Identify high-risk features for postoperative myasthenic crisis 3:

• Bulbar involvement (dysphagia, facial weakness)
• Reduced pulmonary function tests
• Prior myasthenic crisis
• Rapidly progressive symptoms
• MGFA severity class III-V

Use validated prediction models (Leuzzi or Kanai scores) to guide intensity of perioperative monitoring 3

Laboratory Workup

• AChR antibodies and antistriated muscle antibodies 1, 4
• If AChR negative: muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4) antibodies 1
• CPK, aldolase, ESR, CRP to evaluate for concurrent myositis 1
• Troponin and ECG if respiratory insufficiency or elevated CPK (rule out myocarditis) 1

Neurology Consultation

Mandatory for all grades of myasthenia undergoing surgery 1, 4

Medication Avoidance (Critical Safety Issue)

Strictly avoid medications that worsen myasthenia 4, 1, 4:

• β-blockers
• IV magnesium
• Fluoroquinolones
• Aminoglycosides
• Macrolide antibiotics

Additional contraindications 5:

• Methocarbamol (interferes with pyridostigmine effects)
• Use caution with benzodiazepines and opioids (respiratory depression risk) 2, 6

Anesthesia Planning

Muscle Relaxant Strategy

Non-depolarizing agents require 50-75% dose reduction 7:

• Myasthenic patients show increased sensitivity and prolonged duration of action 7
• Atracurium or cisatracurium preferred (organ-independent elimination) 7
• Rocuronium acceptable if sugammadex available for reversal 2

Avoid suxamethonium in chronic motor deficit or up-regulation of nicotinic receptors 7

Neuromuscular Monitoring

Mandatory intraoperative monitoring 7:

• Train-of-four (TOF) ratio monitoring essential
• Pre-induction TOF ratio <0.9 predicts greater sensitivity to muscle relaxants 7
• Adjust dosing based on real-time monitoring to avoid overdosing 7

Reversal Agent

Sugammadex is strongly preferred over neostigmine 7, 8:

• Neostigmine may interfere with chronic pyridostigmine therapy 7
• Sugammadex provides reliable, rapid reversal without anticholinergic effects 7, 8
• Dose: standard dosing based on depth of blockade

Regional Anesthesia

Strongly consider regional techniques when feasible 8, 9:

• Peripheral nerve blocks for adjunct pain control 8
• Reduces opioid requirements and respiratory depression risk
• Avoids muscle relaxant exposure entirely

Perioperative Care Considerations

Pain Management

• Limit opioids and sedatives due to respiratory depression risk 8, 2
• Prioritize multimodal analgesia with regional blocks 8
• Acetaminophen and NSAIDs as appropriate

Extubation Criteria

Absolutely no residual curarization before extubation 8:

• TOF ratio ≥0.9 mandatory
• Adequate spontaneous breathing parameters
• Negative inspiratory force and vital capacity within acceptable range
• Consider delayed extubation in high-risk patients

Postoperative Monitoring

• Not all patients require routine ICU admission 8
• Base ICU admission on preoperative risk stratification 3
• High-risk patients (bulbar symptoms, poor PFTs, prior crisis) warrant intensive monitoring 1
• Frequent pulmonary function assessment in first 24-48 hours 1

Common Pitfalls to Avoid

1. Stopping pyridostigmine preoperatively - Continue through day of surgery
2. Using standard doses of muscle relaxants - Reduce by 50-75%
3. Reversal with neostigmine - Use sugammadex instead
4. Administering contraindicated antibiotics - Check all perioperative medications
5. Inadequate preoperative respiratory assessment - PFTs are mandatory, not optional
6. Routine use of IVIg/plasmapheresis - Reserve for high-risk patients only based on validated risk scores