Which of the following is the most common triggering agent for malignant hyperthermia in clinical anesthesia practice?

Explanation

## Most Common Triggering Agent in Malignant Hyperthermia **Key Point:** Desflurane is the most commonly implicated volatile anesthetic triggering malignant hyperthermia (MH) in modern anesthesia practice, followed by isoflurane and sevoflurane. Succinylcholine is the most common *depolarizing* agent trigger, but volatile anesthetics collectively are the most frequent triggers overall. ### Triggering Agents Classification | Agent Category | Triggering Agents | Non-triggering Alternatives | |---|---|---| | **Volatile anesthetics** | Desflurane, isoflurane, sevoflurane, halothane | Nitrous oxide | | **Depolarizing agents** | Succinylcholine | — | | **Non-depolarizing agents** | None | All safe (rocuronium, vecuronium, atracurium) | | **Induction agents** | None | Propofol, thiopental, etomidate all safe | | **Local anesthetics** | None | All amide and ester agents safe | **High-Yield:** In the modern era, desflurane is the most frequently encountered trigger because it is the most commonly used volatile anesthetic in operating theaters worldwide. Halothane, historically the most potent MH trigger, is now rarely used in developed countries. **Clinical Pearl:** The combination of a volatile anesthetic (especially desflurane) + succinylcholine carries the highest risk for fulminant MH crisis. Even volatile anesthetics alone can trigger MH, though the onset may be delayed. **Mnemonic — Safe Induction for MH-Susceptible Patients:** **PAVE** = Propofol, Amide local anesthetics, Volatile agents (NO — avoid), Etomidate. Non-depolarizing agents (rocuronium, vecuronium) are safe; avoid succinylcholine. ### Pathophysiology Volatile anesthetics (especially desflurane) trigger MH by: 1. Sensitizing the ryanodine receptor (RYR1) in skeletal muscle sarcoplasmic reticulum 2. Increasing intracellular Ca²⁺ release 3. Uncontrolled muscle contraction and hypermetabolism 4. Rapid rise in core temperature (hence "malignant hyperthermia") **Warning:** Temperature rise is a LATE sign of MH. Early signs include muscle rigidity, tachycardia, tachypnea, and elevated end-tidal CO₂ (ETCO₂). Do not wait for fever to diagnose MH.