Rapid Sequence Intubation in Myasthenia Gravis
Direct Recommendation
Use propofol for induction and rocuronium at 50-75% dose reduction (0.3-0.45 mg/kg instead of standard 1.2 mg/kg) with mandatory quantitative neuromuscular monitoring, continue pyridostigmine on the day of surgery including the morning dose, and have sugammadex immediately available for reversal. 1, 2, 3
Induction Agent Selection
Propofol is the recommended induction agent for RSI in myasthenia gravis patients due to its short duration of action, which allows rapid respiratory assessment post-intubation, though be prepared to manage potential hypotension. 1
- Propofol does not directly affect neuromuscular transmission and provides predictable sedation. 3
- Alternative approach: Some centers have successfully performed RSI using propofol combined with remifentanil and lidocaine without any neuromuscular blocking agent, though this is less conventional. 4
Neuromuscular Blocking Agent Selection and Dosing
Agent Choice
Rocuronium, atracurium, or cisatracurium are acceptable choices, with benzylisoquinoline agents (atracurium/cisatracurium) preferred if the patient has renal or hepatic impairment. 1, 2, 3
- Benzylisoquinoline agents undergo organ-independent elimination via Hofmann degradation, making them more predictable in patients with organ dysfunction. 1, 3
- Rocuronium is acceptable but requires sugammadex availability for reversal. 1, 3
Critical Dose Reduction
Reduce the standard dose by 50-75% due to heightened sensitivity from reduced functional acetylcholine receptors at the neuromuscular junction. 1, 2, 3
- For rocuronium: use 0.3-0.45 mg/kg instead of the standard 1.2 mg/kg. 1, 5
- For atracurium/cisatracurium: reduce initial dose by 50-75%. 1, 3
- The degree of dose reduction correlates directly with disease severity—more severe MG requires greater reductions. 1, 2
Avoid Succinylcholine
Do not use succinylcholine as MG patients demonstrate paradoxical resistance requiring higher doses (up to 2-3 times normal) due to receptor down-regulation, which defeats the purpose of rapid onset. 1, 3
Mandatory Neuromuscular Monitoring
Quantitative train-of-four (TOF) monitoring is absolutely mandatory when any muscle relaxant is used in MG patients (Level I evidence). 1, 2
Pre-Administration Baseline
- Measure baseline TOF ratio before administering any neuromuscular blocking agent. 1, 2
- If baseline TOF <0.9, sensitivity to non-depolarizing agents is significantly greater and doses must be reduced even further than the standard 50-75% reduction. 1, 2
Post-Administration Monitoring
- Continuous TOF monitoring throughout the procedure is essential to guide additional dosing and assess readiness for reversal. 1, 2
- Ensure TOF ratio >0.9 before extubation to confirm complete reversal of neuromuscular blockade. 1, 3
Pyridostigmine Management
Continue pyridostigmine on the day of surgery, including the morning dose. 1, 2, 3
Evidence Supporting Continuation
- Discontinuing pyridostigmine on the day of surgery increases the risk of respiratory distress and predisposes patients to respiratory discomfort. 1, 3, 6
- Patients who received their morning dose of pyridostigmine showed relative resistance to vecuronium (requiring higher doses) but had better baseline respiratory function. 6
- Patients who omitted the morning dose experienced quicker onset of neuromuscular blockade but 43% complained of respiratory discomfort while waiting for surgery. 6
Dosing Equivalents
- 30 mg oral pyridostigmine = 1 mg IV pyridostigmine = 0.75 mg neostigmine IM. 3
- Exception: For patients already intubated in myasthenic crisis, discontinue or withhold pyridostigmine. 3
Reversal Strategy
Sugammadex is the strongly recommended reversal agent for rocuronium-induced neuromuscular blockade in MG patients, not neostigmine. 1, 3
Why Sugammadex Over Neostigmine
- Sugammadex provides rapid and predictable reversal without interfering with long-term anticholinesterase treatment. 1, 3
- Neostigmine may interfere with chronic pyridostigmine therapy and is less predictable in MG patients. 3
- The risks of residual neuromuscular blockade are significantly increased in MG, making reliable reversal critical. 3
Clinical Importance
- A case report documented a 232-minute duration of paralysis after standard-dose rocuronium (1.2 mg/kg) in an MG patient, which was only reversed after sugammadex administration. 7
- Have sugammadex immediately available before inducing any MG patient requiring neuromuscular blockade. 1, 3
Critical Drug Interactions and Contraindications
Absolute Contraindications
Never administer IV magnesium—it is absolutely contraindicated as it potentiates neuromuscular blockade and can precipitate respiratory failure. 3, 5
Drugs That Potentiate Neuromuscular Blockade
Avoid or use extreme caution with agents that worsen neuromuscular transmission: 3, 5
- Aminoglycosides and fluoroquinolones (worsen neuromuscular transmission). 1, 3
- Inhalation anesthetics (enflurane, isoflurane, sevoflurane—though these are safe for maintenance, they do potentiate blockade). 3, 5
- Local anesthetics, procainamide, quinidine, and lithium. 3, 5
Alternative Approach: Avoiding Neuromuscular Blockade
If clinically feasible, consider RSI without neuromuscular blocking agents using a combination of propofol, remifentanil, and lidocaine with cricoid pressure. 4
- This approach has been successfully used in a 14-year-old MG patient requiring emergency surgery with a full stomach. 4
- Volatile anesthetics alone may provide sufficient muscle relaxation to avoid neuromuscular blocking agents entirely. 3, 8
- Regional anesthesia (spinal, epidural, or peripheral nerve blocks) is an excellent alternative when surgically appropriate, completely avoiding the risks of neuromuscular blockade. 1, 8
Common Pitfalls to Avoid
- Never use standard NMBA doses—always reduce by 50-75%. 1, 3 A case report showed that full-dose rocuronium led to 232 minutes of paralysis. 7
- Never assume normal respiratory function based on lack of dyspnea symptoms—objective pulmonary function testing is mandatory preoperatively. 3
- Never discontinue pyridostigmine preoperatively unless the patient is already intubated in myasthenic crisis. 1, 3, 6
- Never mix rocuronium with alkaline solutions (e.g., barbiturates) in the same syringe due to incompatibility. 5
- Be aware that the duration of neuromuscular blockade may be profoundly prolonged—up to 4 hours with standard dosing. 7
Post-Intubation Monitoring
- Continuous SpO₂ monitoring and, whenever possible, blood or end-tidal CO₂ monitoring. 3
- Monitor for signs of myasthenic crisis requiring immediate intervention. 3
- Extended monitoring (up to 2 hours) is necessary if opioid reversal with naloxone is required, as naloxone's half-life (30-45 minutes) is shorter than fentanyl's duration of effect. 3