What is the protocol for managing Malignant Hyperthermia (MH)?

Malignant Hyperthermia Management Protocol

The immediate management of malignant hyperthermia requires stopping all triggering agents, administering dantrolene 2 mg/kg IV, hyperventilating with 100% oxygen, and implementing rapid cooling measures to prevent mortality. 1, 2

Immediate Actions

• Stop all triggering agents (volatile anesthetics and succinylcholine)
• Hyperventilate with 100% O₂ at high flow (2-3 times normal minute volume)
• Declare an emergency and call for help
• Change to non-triggering anesthesia (TIVA) if anesthesia must continue
• Inform surgeon and request termination/postponement of surgery
• Disconnect vaporizer (do not waste time changing circuit/machine)

Dantrolene Administration

• Give dantrolene 2 mg/kg IV immediately (20 mg ampoules mixed with 60 ml sterile water)
• Obtain additional dantrolene from other sources (36-50 ampoules may be needed for an adult)
• Continue dantrolene infusions until cardiac and respiratory systems stabilize
• Maximum dose of 10 mg/kg may be exceeded if necessary 1, 3

Monitoring

• Continue routine anesthetic monitoring (SaO₂, ECG, NIAP, EtCO₂)
• Measure core temperature continuously
• Establish good IV access with wide-bore cannulas
• Consider inserting arterial and central venous lines, and urinary catheter
• Obtain samples for K⁺, CK, arterial blood gases, myoglobin, and glucose
• Check renal and hepatic function and coagulation
• Monitor for signs of compartment syndrome
• Continue monitoring for minimum of 24 hours in ICU/HDU 1

Treat Hyperthermia

• Administer 2000-3000 ml of chilled (4°C) 0.9% saline IV
• Apply surface cooling: wet cold sheets, fans, ice packs in axillae and groin
• Use additional cooling devices if available
• Stop cooling once temperature < 38.5°C 1, 2

Treat Hyperkalemia

• Administer 50% dextrose 50 ml with 50 IU insulin (adult dose)
• Give CaCl₂ 0.1 mmol/kg IV (approximately 7 mmol for a 70 kg adult)
• Consider dialysis if severe and refractory 1

Treat Acidosis

• Hyperventilate to normocapnea
• Administer sodium bicarbonate IV if pH < 7.2 1

Treat Arrhythmias

• Give amiodarone 300 mg for adults (3 mg/kg IV)
• Consider β-blockers (propranolol/metoprolol/esmolol) for persistent tachycardia 1

Maintain Urinary Output > 2 ml/kg/h

• Administer furosemide 0.5-1 mg/kg
• Give mannitol 1 g/kg
• Provide adequate fluid resuscitation with crystalloids 1

Post-Crisis Management

• Continue dantrolene 4-8 mg/kg/day in four divided doses for 1-3 days to prevent recurrence 3
• Monitor patient for at least 24 hours in ICU/HDU
• Consult with local Malignant Hyperthermia Investigation Unit
• Refer patient and family members for diagnostic testing (in vitro contracture testing) at a designated MH laboratory 1, 4

Important Considerations

• MH can occur even in patients who have had previous uneventful anesthesia 1, 4
• Do not delay dantrolene administration while waiting for laboratory confirmation 2
• Mortality has decreased from 80% to <5% with prompt recognition and treatment 4
• The incidence of MH reactions ranges from 1:10,000 to 1:250,000 anesthetics 4
• Masseter muscle spasm after succinylcholine may be a prodromal sign of MH 5

Remember that early recognition and immediate treatment with dantrolene are essential for reducing mortality in malignant hyperthermia crises 6, 7.