Orbit Decompression & Myasthenia

What the Examiner Is Testing

This case tests your practical knowledge of myasthenia gravis pharmacology — specifically the paradoxical NMB response — combined with the competing urgency of a full stomach and optic nerve decompression. The examiner wants to see that you understand MG is not just "avoid paralytics"; it requires a nuanced titration strategy.

The Board Trap

The trap is using a standard dose of succinylcholine for RSI. MG patients are often resistant to succinylcholine because they have fewer functional nicotinic receptors — so your standard 1 mg/kg dose may give inadequate conditions. Conversely, non-depolarizing agents like vecuronium or rocuronium have exaggerated and prolonged effects. You need to adjust both.

Walk-Through: How This Case Plays Out

Examiner: The patient needs an urgent RSI for the full-stomach risk. How do you handle her MG?

Me: I would proceed with RSI but modify my NMB dosing carefully. For succinylcholine, I'd increase to 1.5-2.0 mg/kg because MG patients can be resistant to depolarizing agents. If I choose to use a non-depolarizing agent instead, I'd use rocuronium at 1.2 mg/kg but I'm prepared for a prolonged block — quantitative twitch monitoring is going on before I give anything. Sugammadex is drawn up and labeled at the bedside.

Examiner: She's intubated. How do you maintain anesthesia?

Me: I'd use a volatile-heavy technique with a high MAC concentration for maintenance — sevoflurane provides enough muscle relaxation that I can largely avoid additional NMBs intraoperatively. I won't give boluses of non-depolarizers during the case if I can help it. If I absolutely need more relaxation, I'm using the smallest effective dose and monitoring continuously with a TOF monitor.

Examiner: At the end of the case, her TOF ratio is 0.7. Can you extubate?

Me: No. 0.7 is not adequate for extubation — I need a TOF ratio above 0.9, ideally 1.0, before I consider it. In a patient with MG, residual neuromuscular blockade plus her underlying disease can cause acute respiratory failure immediately after extubation. I'll give sugammadex — 2 mg/kg for moderate block — and recheck the TOF before I pull the tube. I'm also looking for clinical signs: sustained head lift for 5 seconds, strong grip.

Examiner: She's extubated and doing well. What's your post-op plan?

Me: I'd keep her in PACU with close respiratory monitoring and a low threshold for reintubation. I'll coordinate with neurology about her pyridostigmine — she'll need to restart it as soon as she can swallow. I won't give morphine as my primary analgesic because respiratory depression is a real risk. I'd use multimodal analgesia: acetaminophen, ketorolac, and a small dose of opioid only if needed.

Key Phrases That Score Points

• "MG patients are resistant to succinylcholine — I'm dosing at 1.5-2.0 mg/kg for RSI."
• "Non-depolarizing agents are exaggerated and prolonged in MG — I'm using the minimum and monitoring with quantitative TOF."
• "TOF ratio above 0.9 before extubation — 0.7 is not good enough in a myasthenic patient."
• "Sugammadex drawn up and labeled at the bedside before I give any NMB."
• "Volatile-heavy technique reduces my need for additional neuromuscular blockade intraoperatively."

Why This Case Appears on the Boards

Neuromuscular disorders appear as secondary complications in otherwise straightforward surgical cases. This case specifically tests whether you can apply pharmacologic principles — not just memorize contraindications — and whether you understand that extubation criteria are stricter in disease states affecting neuromuscular function.