What is the management of malignant hyperthermia?

Management of Malignant Hyperthermia

Immediately stop all triggering agents (volatile anesthetics and succinylcholine), hyperventilate with 100% oxygen at 2-3 times normal minute volume, and administer dantrolene 2 mg/kg IV as the cornerstone of treatment—this sequence of actions is critical for patient survival. 1

Immediate Actions (First Minutes)

Stop all trigger agents immediately and declare an emergency while calling for help. 1 The trigger agents that must be discontinued are all volatile (inhalation) anesthetic agents and succinylcholine. 1

Hyperventilate with 100% oxygen at high flow using a minute volume 2-3 times normal to eliminate volatile anesthetics and address hypercarbia. 1, 2

Change to non-trigger anesthesia (TIVA) and disconnect the vaporizer—do not waste valuable time changing the entire circuit or anesthetic machine. 1, 2

Inform the surgeon and request immediate termination or postponement of surgery. 1, 2

Dantrolene Administration (The Definitive Treatment)

Administer dantrolene 2 mg/kg IV immediately (each 20 mg ampoule is mixed with 60 ml sterile water). 1, 2 This is the specific antidote and cornerstone of MH treatment. 3, 4

Obtain additional dantrolene urgently from pharmacy or nearby hospitals—at least 36-50 ampoules may be needed for an adult patient. 1, 2

Repeat dantrolene infusions until cardiac and respiratory systems stabilize. 1, 2 The maximum dose of 10 mg/kg may need to be exceeded in severe cases. 1

Comprehensive Monitoring

Establish robust IV access with wide-bore cannulas for aggressive fluid resuscitation and medication administration. 1, 2

Continue routine anesthetic monitoring (SpO2, ECG, NIBP, end-tidal CO2) and measure core temperature continuously. 1, 2

Consider invasive monitoring with arterial and central venous lines, plus urinary catheter for close hemodynamic monitoring and urine output tracking. 1

Obtain laboratory samples for potassium, creatine kinase (CK), arterial blood gases, myoglobin, glucose, renal and hepatic function, and coagulation studies. 1

Check for compartment syndrome as muscle breakdown can lead to this complication. 1

Treat Specific Complications

Hyperthermia

• Administer 2000-3000 ml of chilled (4°C) 0.9% saline IV for internal cooling. 1
• Apply surface cooling with wet cold sheets, fans, and ice packs in axillae and groin. 1, 2
• Stop cooling once temperature drops below 38.5°C to avoid overcooling. 1

Hyperkalemia

• Give dextrose 50%, 50 ml with 50 IU insulin (adult dose) to drive potassium intracellularly. 1, 2
• Administer calcium chloride 0.1 mmol/kg IV (e.g., 7 mmol = 10 ml for a 70 kg adult) for cardiac membrane stabilization. 1, 2
• Dialysis may be required in severe cases. 1

Acidosis

• Hyperventilate to normocapnia as the primary intervention. 1, 2
• Give sodium bicarbonate IV if pH < 7.2 for severe metabolic acidosis. 1, 2

Arrhythmias

• Administer amiodarone 300 mg (3 mg/kg IV) for an adult as first-line antiarrhythmic. 1, 2
• Use beta-blockers (propranolol/metoprolol/esmolol) if tachycardia persists despite other interventions. 1

Renal Protection

• Maintain urinary output > 2 ml/kg/h to prevent myoglobin-induced renal failure. 1
• Administer furosemide 0.5-1 mg/kg and mannitol 1 g/kg as needed. 1
• Give crystalloid fluids (lactated Ringer's solution or 0.9% saline) IV aggressively. 1

Post-Crisis Management

Monitor the patient for a minimum of 24 hours in ICU, HDU, or recovery unit due to risk of recrudescence. 1, 2, 4 The risk of dying from MH has increased when vigilance is not maintained in the post-crisis period. 4

Continue dantrolene for a short period after the crisis to prevent recurrence. 3

Refer the patient and family members to a regional or national Malignant Hyperthermia Investigation Unit for diagnostic testing using in vitro contracture testing (IVCT) at a designated MH laboratory. 1, 2, 4

Critical Pitfalls to Avoid

Do not delay dantrolene administration while pursuing alternative diagnoses—early treatment with dantrolene is essential for reducing mortality. 3, 4 The European Malignant Hyperthermia Group emphasizes that early recognition and immediate treatment are essential for patient survival. 2

Do not assume safety based on prior uneventful anesthesia—any patient may develop MH during or shortly after anesthesia with trigger agents, even with previous uncomplicated exposures. 1

Do not underestimate dantrolene requirements—ensure adequate supplies are immediately available, as large quantities may be needed. 1, 2