A 42-year-old woman is undergoing general anesthesia for elective laparoscopic cholecystectomy. After induction with propofol and succinylcholine, the anesthesiologist observes sustained muscle contractions followed by flaccid paralysis. The patient's temperature begins to rise, and end-tidal CO₂ increases rapidly. Which of the following is the MOST appropriate immediate management?

Explanation

## Malignant Hyperthermia (MH) Recognition and Management The clinical presentation described—sustained muscle contractions (fasciculations) followed by flaccid paralysis, rapid rise in end-tidal CO₂, and increasing temperature—is pathognomonic for **malignant hyperthermia**, a pharmacogenetic crisis triggered by succinylcholine and/or volatile anesthetics. ### Key Point: **Early signs of MH (in order of appearance):** 1. Elevated end-tidal CO₂ (earliest and most sensitive sign) 2. Sustained muscle rigidity/fasciculations 3. Tachycardia 4. Temperature rise (late sign) ### Immediate Management Protocol: - **Stop all triggering agents** (succinylcholine and volatile anesthetics immediately) - **Hyperventilate with 100% oxygen** to wash out volatile anesthetic and manage hypercarbia - **Administer dantrolene sodium 2.5 mg/kg IV** (initial dose; repeat every 5 minutes up to 10 mg/kg if needed) - Dantrolene blocks calcium release from sarcoplasmic reticulum, preventing sustained muscle contraction and heat generation - Continue surgery if possible; if not, proceed with safe anesthesia (TIVA with propofol, opioids, non-depolarizing agents) - Active cooling measures (cold IV fluids, ice packs, cold peritoneal lavage) - Monitor for complications: rhabdomyolysis, myoglobinuria, hyperkalemia, DIC ### High-Yield: Dantrolene is the **only specific treatment** for MH. It must be prepared rapidly (each 20 mg vial requires 60 mL sterile water without bacteriostatic agents). Early recognition and prompt dantrolene administration dramatically improve outcomes and reduce mortality from >50% to <5%.