A 38-year-old woman is undergoing general anesthesia for elective thyroid surgery. After induction with propofol and intubation with succinylcholine, she develops sudden onset muscle rigidity, tachycardia (HR 130/min), hypertension (BP 160/95 mmHg), and a rise in end-tidal CO₂ (ETCO₂) from 35 to 55 mmHg within 10 minutes. Temperature is currently 37.2°C. Which of the following is the MOST appropriate immediate management?

Explanation

## Malignant Hyperthermia (MH) Crisis Recognition and Management The clinical presentation describes a **fulminant malignant hyperthermia (MH) episode**: - **Muscle rigidity** (early sign, often within minutes of triggering agent exposure) - **Tachycardia** (compensatory response to hypermetabolism) - **Hypertension** (sympathetic activation) - **Elevated ETCO₂** (pathognomonic sign — reflects hypermetabolism and muscle breakdown) - **Succinylcholine exposure** (known MH trigger) ### Immediate Management Protocol: **Key Point:** The classic triad of MH is: 1. Muscle rigidity 2. Elevated ETCO₂ 3. Tachycardia **Correct Management Steps (in order):** - **Stop all triggering agents immediately** (propofol is safe; volatile anesthetics and succinylcholine are triggers) - **Hyperventilate with 100% oxygen** (↓ volatile anesthetic washout, ↑ oxygen delivery, ↓ acidosis) - **Administer dantrolene sodium 2.5 mg/kg IV** (inhibits calcium release from sarcoplasmic reticulum, halts muscle hypermetabolism) - Activate MH protocol: cooling measures, monitor for complications (hyperkalemia, myoglobinuria, DIC) **Clinical Pearl:** ETCO₂ elevation is the **earliest and most sensitive sign** of MH — more reliable than temperature rise (which occurs late). Temperature may remain normal or near-normal in early MH. **High-Yield:** Dantrolene is the **only specific treatment** for MH. Each vial (20 mg) must be mixed with sterile water immediately before use.