A 52-year-old man with a history of myasthenia gravis is scheduled for elective cholecystectomy. Regarding muscle relaxant selection and management in this patient, all of the following are true EXCEPT:

Explanation

## Muscle Relaxants in Myasthenia Gravis ### Pathophysiology of Myasthenia Gravis **Key Point:** Myasthenia gravis (MG) is an autoimmune disorder with antibodies against nicotinic acetylcholine receptors at the neuromuscular junction, resulting in: - Reduced number of functional ACh receptors - Impaired neuromuscular transmission - Exaggerated sensitivity to both depolarising and non-depolarising agents ### Management Strategy in MG Patients Requiring Anesthesia ```mermaid flowchart TD A[MG patient requiring anesthesia]:::outcome --> B{Muscle relaxant needed?}:::decision B -->|No| C[Avoid all relaxants]:::action B -->|Yes| D{Depolarising or Non-depolarising?}:::decision D -->|Succinylcholine|E[CONTRAINDICATED]:::urgent D -->|Non-depolarising|F[Use reduced dose]:::action F --> G[Titrate with TOF monitoring]:::action G --> H[Continue anticholinesterases periop]:::action E --> I[Risk: myasthenic crisis, prolonged apnoea] ``` ### Analysis of Each Statement | Statement | Correct? | Explanation | |-----------|----------|-------------| | Succinylcholine contraindicated | ✓ YES | Unpredictable response, risk of myasthenic crisis, prolonged apnoea due to pseudocholinesterase abnormalities | | Non-depolarising agents should be **avoided entirely** | ✗ **NO** | Non-depolarising agents CAN be used but require dose reduction and careful monitoring | | Reduced dose + TOF monitoring | ✓ YES | Standard approach — titrate to effect with neuromuscular monitor | | Continue anticholinesterases periop | ✓ YES | Maintains baseline neuromuscular function; omitting them worsens blockade | ### Why Option 1 (Index 1) is INCORRECT **High-Yield:** Non-depolarising agents are **NOT absolutely contraindicated** in MG. The key is **dose reduction and careful titration**. **Clinical Pearl:** MG patients have: - Increased sensitivity to non-depolarising agents (require 30–50% dose reduction) - Exaggerated and prolonged blockade - BUT: they can still receive non-depolarising agents if monitored carefully with train-of-four **Warning:** The statement "avoid entirely" is too absolute. The correct approach is "use cautiously with reduced dose and TOF monitoring," not "avoid completely." Complete avoidance would force reliance on succinylcholine, which is actually more dangerous in MG. ### Correct Statements (Options 0, 2, 3) - **Option 0:** Succinylcholine is genuinely contraindicated in MG — risk of myasthenic crisis, prolonged apnoea - **Option 2:** Reduced dosing + train-of-four titration is the standard of care for non-depolarising agents in MG - **Option 3:** Anticholinesterases (pyridostigmine, neostigmine) should be continued perioperatively to maintain baseline neuromuscular reserve **Mnemonic:** **MG-RELAX** = **M**yasthenia **G**ravis: **R**educed dose, **E**xtra monitoring, **L**ess drug, **A**void succinylcholine, **X** (avoid complete avoidance of non-depolarisers).