Management and Treatment of Malignant Hyperthermia
The cornerstone of malignant hyperthermia management is immediate discontinuation of trigger agents, hyperventilation with 100% oxygen, and prompt administration of dantrolene 2 mg/kg IV as the specific antidote. 1, 2
Immediate Actions
- Stop all trigger agents (volatile anesthetics and succinylcholine) immediately 1, 2
- Hyperventilate with 100% oxygen at high flow (2-3 times normal minute volume) 1, 2
- Declare an emergency and call for help 1
- Change to non-trigger anesthesia (TIVA - Total Intravenous Anesthesia) 1
- Inform the surgeon and request termination/postponement of surgery 1
- Disconnect the vaporizer without wasting time changing the circuit/anesthetic machine 1
Dantrolene Administration
- Administer dantrolene 2 mg/kg IV (20 mg ampoules mixed with 60 ml sterile water) 1, 3
- Obtain additional dantrolene from other sources (pharmacy/nearby hospitals) - at least 36-50 ampoules may be needed for an adult patient 1
- Repeat dantrolene infusions until cardiac and respiratory systems stabilize 1
- Maximum dose of 10 mg/kg may need to be exceeded in severe cases 1, 3
Monitoring and Supportive Care
- Continue routine anesthetic monitoring (SaO₂, ECG, NIAP, E'CO₂) 1
- Measure core temperature continuously 1
- Establish good IV access with wide-bore cannulas 1
- Consider inserting arterial and central venous lines, and a urinary catheter 1
- Obtain samples for measurement of K⁺, CK, arterial blood gases, myoglobin, and glucose 1
- Check renal and hepatic function and coagulation 1
- Monitor for signs of compartment syndrome 1
- Monitor the patient for a minimum of 24 hours in ICU/HDU 1, 2
Treatment of Specific Complications
Hyperthermia Management
- Administer 2000-3000 ml of chilled (4°C) 0.9% saline IV 1
- Apply surface cooling: wet cold sheets, fans, and ice packs in axillae and groin 1
- Use other cooling devices if available 1
- Stop cooling once temperature drops below 38.5°C 1
Hyperkalemia Management
- Administer 50 ml of 50% dextrose with 50 IU insulin (adult dose) 1
- Give CaCl₂ 0.1 mmol/kg IV (approximately 7 mmol = 10 ml for a 70 kg adult) 1
- Consider dialysis in severe cases 1
Acidosis Management
Cardiac Arrhythmia Management
- Administer amiodarone 300 mg for adults (3 mg/kg IV) 1
- Consider β-blockers (propranolol/metoprolol/esmolol) if tachycardia persists 1
Maintain Adequate Urine Output (>2 ml/kg/h)
- Administer furosemide 0.5-1 mg/kg 1
- Give mannitol 1 g/kg 1
- Provide crystalloid fluids (lactated Ringer's or 0.9% saline) IV 1
Post-Crisis Management
- Continue dantrolene for 24-48 hours post-crisis to prevent recurrence 3
- Administer oral dantrolene 4-8 mg/kg/day in four divided doses for 1-3 days following the crisis 3
- Consult with a Malignant Hyperthermia Investigation Unit about the case 1
- Refer patients suspected of being MH-susceptible for diagnostic testing using in vitro contracture testing (IVCT) 1, 2
- Inform family members about potential genetic risk and need for testing 1
Common Pitfalls and Caveats
- Do not waste time changing the anesthetic circuit or machine - simply disconnect the vaporizer and hyperventilate with 100% oxygen 1
- Recognize that MH can occur even in patients who have previously had uneventful general anesthesia 1
- Early signs may include masseter spasm after succinylcholine use, unexplained tachycardia, and rising end-tidal CO₂ despite increased ventilation 1, 4
- Pediatric patients with neuromuscular disorders may have increased risk of MH, even without family history 5
- Dantrolene availability is critical - mortality increases dramatically without prompt administration 2, 6
- Mortality from MH has decreased from 80% thirty years ago to <5% with proper recognition and treatment 4, 7
The European Malignant Hyperthermia Group guidelines emphasize that early recognition and immediate treatment are essential for patient survival, with stopping trigger agents and administering dantrolene being the critical first steps in management 1, 2.