What is the role of Intravenous Immunoglobulin (IVIG) as bridging therapy in patients with myasthenia gravis undergoing thymectomy?

IVIG Bridging Therapy for Myasthenia Gravis Undergoing Thymectomy

Direct Recommendation

In well-controlled myasthenia gravis patients undergoing thymectomy, preoperative IVIG bridging therapy is not necessary and can be safely omitted. 1

Evidence-Based Approach

For Well-Controlled Patients (Minimal Manifestations)

• Omit preoperative IVIG in patients with well-controlled myasthenia gravis who have minimal manifestations before surgery 1
• A prospective, randomized, double-blind trial (Class I evidence) demonstrated no significant difference in myasthenic crisis rates between IVIG and placebo groups when patients had well-controlled disease 1
• Only 1 of 47 patients (in the placebo group) developed myasthenic crisis requiring non-invasive ventilation, with no reintubation needed 1

Preoperative Assessment Requirements

Before deciding to omit IVIG, confirm the following:

• Respiratory function: Measure negative inspiratory force (NIF) and vital capacity (VC) 2
• Risk stratification using the "20/30/40" rule: Patients are at high risk if vital capacity <20 mL/kg, maximum inspiratory pressure <30 cm H₂O, or maximum expiratory pressure <40 cm H₂O 2
• Antibody status: Check acetylcholine receptor (AChR) and muscle-specific tyrosine kinase (MuSK) antibody levels 2
• Cardiac evaluation: Consider ECG and echocardiogram if respiratory failure or elevated CPK levels are present 2
• Serum antiacetylcholine receptor antibody levels should be measured in all patients suspected of having thymomas, even those without symptoms, to avoid respiratory failure during surgery 3

When IVIG IS Indicated

Administer preoperative IVIG in the following high-risk scenarios:

• Patients with poorly controlled myasthenia gravis or active exacerbation 2
• Patients meeting the "20/30/40" rule criteria for respiratory compromise 2
• Patients with dysphagia, notable weight loss, severe weakness 3
• Patients with history of myasthenic crisis who are not currently well-controlled 2

IVIG Dosing Protocol

When IVIG is indicated:

• Standard dose: 2 g/kg divided over 5 days (0.4 g/kg/day) 2
• Alternative regimen: 1 g/kg/day for 2 consecutive days 4
• Timing: Administer 10-30 days before thymectomy, ideally performing surgery within 2 weeks after IVIG treatment to minimize perioperative complications 5
• Onset of action: Improvement begins 1-9 days after starting injection (mean 3.33 days), reaching maximum effect in 3-19 days (mean 6.50 days) 5

IVIG vs Plasma Exchange

IVIG is preferred over plasma exchange for preoperative preparation:

• Shorter intubation period (statistically significant, p=0.01) 4
• Shorter duration of surgery (statistically significant, p=0.05) 4
• Safer in specific populations: patients with hypotension or autonomic instability, children, elderly patients (>65 years), and those with sepsis 6
• Easier to administer and more widely available than plasma exchange 3
• Comparable efficacy to plasma exchange with fewer complications 6

Important Caveats

• Check serum IgA levels before administering IVIG; IgA deficiency may lead to severe anaphylaxis, requiring IVIG preparations with reduced IgA levels 3
• Medical control of myasthenia gravis should be achieved before any surgical procedure 3
• Continue anticholinesterase medications (pyridostigmine) perioperatively unless contraindicated 3
• Monitor closely for signs of myasthenic crisis postoperatively, including respiratory failure 2

Postoperative Considerations

• Patients at risk for prolonged mechanical ventilation include those unable to lift arms from bed at 1 week after intubation and those with axonal subtype or unexcitable nerves on electrophysiology 3
• Consider early tracheostomy in high-risk patients 3