A 28-year-old male from rural Maharashtra is scheduled for emergency appendicectomy under general anesthesia. Induction is uneventful with propofol and succinylcholine. Within 2 minutes of intubation, the anesthetist notices the jaw muscles are rigid and the patient's core temperature begins to rise. Capnography shows a steep rise in end-tidal CO₂ (ETCO₂) from 35 to 65 mmHg within 5 minutes. Arterial blood gas shows pH 7.15, PaCO₂ 85 mmHg, and K⁺ 6.8 mEq/L. What is the most appropriate immediate management?

Explanation

## Diagnosis and Immediate Recognition **Key Point:** Malignant hyperthermia (MH) is a pharmacogenetic crisis triggered by exposure to succinylcholine and/or volatile anesthetics in susceptible individuals. The classic triad—muscle rigidity, hypercarbia (↑ ETCO₂), and hyperthermia—must be recognized within minutes. ## Clinical Hallmarks in This Case | Finding | Significance | |---------|-------------| | Jaw rigidity (masseter spasm) post-succinylcholine | Early sign of MH; may precede hyperthermia by minutes | | ETCO₂ spike (35 → 65 mmHg in 5 min) | Hypermetabolism and muscle rigidity; most sensitive early sign | | Rising core temperature | Late sign; hyperthermia occurs after metabolic derangement | | Hyperkalemia (K⁺ 6.8) | Rhabdomyolysis and muscle breakdown; risk of cardiac dysrhythmia | | Metabolic acidosis (pH 7.15) | Lactic acidosis from uncontrolled muscle metabolism | ## Immediate Management Algorithm ```mermaid flowchart TD A[MH suspected: rigidity + ↑ETCO₂ + ↑temp]:::urgent --> B[STOP all triggering agents]:::action B --> C[Hyperventilate 100% O₂]:::action C --> D[Administer dantrolene 2.5 mg/kg IV]:::action D --> E[Active cooling measures]:::action E --> F[Monitor core temp, K⁺, CK, urine myoglobin]:::action F --> G[Treat hyperkalemia if ECG changes]:::action G --> H[Transfer to ICU post-op]:::outcome ``` **High-Yield:** Dantrolene is the ONLY specific treatment for MH. It works by inhibiting calcium release from the sarcoplasmic reticulum, halting the hypermetabolic cascade. Dose: 2.5 mg/kg IV push, repeated every 5 minutes up to 10 mg/kg if signs persist. ## Why Each Step Matters 1. **Discontinue triggers immediately** — Succinylcholine and volatile agents perpetuate the crisis; every second counts. 2. **Hyperventilate with 100% O₂** — Reduces ETCO₂, improves oxygenation, and aids cooling via respiratory heat loss. 3. **Dantrolene sodium** — Specific antagonist; must be reconstituted (20 mg vial + 60 mL sterile water). Each vial provides 20 mg; have multiple vials ready. 4. **Active cooling** — Ice packs to groin, axillae, and neck; cold IV saline; surface cooling blankets. ## Post-Crisis Management **Clinical Pearl:** After dantrolene administration, continue monitoring for recrudescence (recurrence of signs) for at least 24 hours in ICU. Repeat dantrolene 1 mg/kg IV every 4–6 hours for 24–48 hours post-crisis. **Key Point:** Hyperkalemia (K⁺ > 6 mEq/L) with ECG changes requires: - Calcium gluconate 10 mL of 10% IV (cardiac membrane stabilization) - Insulin 10 units + dextrose 25 g IV (shift K⁺ intracellularly) - Sodium bicarbonate 1–2 mEq/kg IV (if severe acidosis) **Mnemonic:** **CHILLED** — Calcium, Hyperventilation, Insulin + dextrose, Lidocaine (for dysrhythmias), Lasix/loop diuretics, Electrolyte monitoring, Dantrolene [cite:Gupta & Sharma Anesthesia 4e Ch Malignant Hyperthermia]