## Malignant Hyperthermia: Triggers and Safe Agents ### Recognized MH Triggers **Key Point:** Malignant hyperthermia is triggered by two classes of anesthetic agents: depolarizing neuromuscular blockers and volatile anesthetics. #### Depolarizing Agents - **Succinylcholine** — the most potent trigger; causes sustained muscle contraction and rhabdomyolysis in susceptible individuals #### Volatile Anesthetics (All Trigger MH) - **Desflurane** — potent MH trigger - **Isoflurane** — potent MH trigger - **Sevoflurane** — potent MH trigger - **Halothane** — potent MH trigger (rarely used now) ### Safe Anesthetic Agents in MH-Susceptible Patients | Agent Class | Safe? | Notes | |---|---|---| | **Nitrous oxide** | ✓ YES | Non-triggering; commonly used in MH-safe anesthesia | | Propofol | ✓ YES | Safe induction agent | | Etomidate | ✓ YES | Safe alternative induction | | Thiopental | ✓ YES | Safe but less commonly used | | Non-depolarizing NMBs | ✓ YES | Rocuronium, vecuronium, atracurium all safe | | Local anesthetics | ✓ YES | Amide and ester types are safe | **High-Yield:** Nitrous oxide is explicitly NOT a trigger for malignant hyperthermia and is routinely used in MH-safe anesthetic protocols. ### Clinical Pearl The mnemonic for MH-safe anesthesia is **"SAFE"**: - **S**uccinylcholine — AVOID (it's a trigger) - **A**void volatile anesthetics - **F**avour propofol, nitrous oxide, opioids - **E**tomidate or other safe induction agents In practice, a safe MH anesthetic uses: propofol/etomidate induction + nitrous oxide + opioids + non-depolarizing NMBs, with avoidance of all volatile agents and succinylcholine. ### Why Nitrous Oxide is Safe Nitrous oxide does not interact with the ryanodine receptor (RYR1) or calcium-release mechanisms in skeletal muscle, making it a truly inert trigger-free agent.
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