A 35-year-old male patient is scheduled for elective abdominal surgery under general anesthesia. After induction with propofol and succinylcholine, the anesthesiologist observes a sustained increase in end-tidal CO₂ (ETCO₂) from 35 mmHg to 55 mmHg within 10 minutes, along with muscle rigidity and a rise in core body temperature. Which of the following is the most appropriate immediate management?

Explanation

## Malignant Hyperthermia (MH) Recognition and Management The clinical presentation describes **malignant hyperthermia (MH)**, a pharmacogenetic crisis triggered by exposure to succinylcholine and/or volatile anesthetics. ### Key Diagnostic Features: - **Sustained hypercarbia** (ETCO₂ >50 mmHg) — earliest and most sensitive sign - **Muscle rigidity** — due to sustained muscle contraction - **Hyperthermia** — late sign; core temperature rise is NOT the earliest indicator - Tachycardia, arrhythmias, cyanosis, and rhabdomyolysis may follow ### Immediate Management Protocol (MHAUS Guidelines): 1. **Stop all triggering agents immediately** (succinylcholine and volatile anesthetics) 2. **Hyperventilate with 100% O₂** to wash out volatile agent and combat hypercarbia 3. **Administer dantrolene sodium 2.5 mg/kg IV** — inhibits calcium release from sarcoplasmic reticulum, terminating the MH crisis 4. Continue dantrolene 1 mg/kg IV every 5 minutes until signs resolve or max 10 mg/kg reached 5. **Active cooling measures** (cold IV fluids, ice packs, cold peritoneal lavage) 6. **Monitor for complications**: rhabdomyolysis, hyperkalemia, acute kidney injury, DIC 7. **Post-operative ICU monitoring** for recrudescence (can occur 24–48 hours later) **Clinical Pearl:** Early recognition and prompt dantrolene administration are life-saving. Mortality has dropped from ~80% (pre-dantrolene era) to <5% with modern protocols. **High-Yield:** ETCO₂ elevation is the **earliest and most sensitive sign** of MH — more reliable than temperature in the acute phase.