What is the appropriate treatment for a patient suspected of having malignant hyperthermia?

Malignant Hyperthermia Treatment

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 a rapid push—this is the life-saving intervention that must not be delayed. 1

Immediate Actions (First 5 Minutes)

The moment you suspect malignant hyperthermia, execute these steps simultaneously:

• Stop all volatile anesthetics (sevoflurane, desflurane, isoflurane, halothane) and succinylcholine immediately 1, 2
• Hyperventilate aggressively with 100% oxygen at high flow—use 2-3 times the normal minute volume to blow off CO2 1
• Declare an emergency and call for all available help 1
• Switch to total intravenous anesthesia (TIVA) with propofol 1, 2
• Disconnect the vaporizer from the circuit—do not waste precious time changing the entire breathing circuit or anesthetic machine during the crisis 1
• Inform the surgeon and request immediate termination or postponement of surgery 1

Dantrolene Administration (The Definitive Treatment)

Dantrolene is the only specific treatment for malignant hyperthermia and must be given immediately:

• Initial dose: 2 mg/kg IV as a continuous rapid push 1, 3
• Continue administering dantrolene until symptoms subside—repeat boluses as needed 1, 3
• Maximum dose is 10 mg/kg, but this may need to be exceeded in severe cases 1, 3
• Prepare 36-50 vials (20 mg each) for an adult patient—each vial must be mixed with 60 mL of sterile water 1, 4, 3
• Obtain additional dantrolene from pharmacy or nearby hospitals immediately, as you will likely need more than initially available 1

Critical pitfall: The FDA label states to start at a minimum of 1 mg/kg 3, but the European Malignant Hyperthermia Group guidelines recommend 2 mg/kg 1, which is the more aggressive and appropriate initial dose given the life-threatening nature of this crisis.

Comprehensive Monitoring

Establish invasive monitoring while dantrolene is being administered:

• Continue routine monitoring: pulse oximetry, ECG, non-invasive blood pressure, end-tidal CO2 1
• Measure core temperature continuously 1, 5
• Establish large-bore IV access with wide-bore cannulas 1, 4
• Insert arterial line and central venous catheter for continuous hemodynamic monitoring 1, 4
• Place urinary catheter to monitor output 1
• Obtain laboratory samples: potassium, creatine kinase, arterial blood gases, myoglobin, glucose, renal function, hepatic function, coagulation studies 1
• Check for compartment syndrome signs, particularly in the extremities 1, 4

Active Cooling Measures

Begin aggressive cooling if temperature is elevated:

• Infuse 2000-3000 mL of chilled (4°C) 0.9% saline intravenously 1
• Apply surface cooling: wet cold sheets, fans, ice packs in axillae and groin 1
• Use any available cooling devices (cooling blankets, intravascular cooling catheters) 1
• Stop cooling once temperature drops below 38.5°C to avoid overcooling 1

Treat Life-Threatening Complications

Hyperkalemia Management

• Administer dextrose 50% (50 mL) with 50 units of insulin IV for adults 1
• Give calcium chloride 0.1 mmol/kg IV (e.g., 7 mmol = 10 mL for a 70 kg adult) 1
• Prepare for dialysis if hyperkalemia is refractory 1

Metabolic Acidosis Management

• Hyperventilate to normocapnia as the primary intervention 1
• Administer sodium bicarbonate IV only if pH drops below 7.2 1

Cardiac Arrhythmia Management

• Give amiodarone 300 mg IV (3 mg/kg) for adults as first-line antiarrhythmic 1
• Use beta-blockers (propranolol, metoprolol, or esmolol) if tachycardia persists despite other interventions 1, 4
• Avoid calcium channel blockers as they may interfere with dantrolene and worsen hyperkalemia 4

Renal Protection

Maintain aggressive urine output to prevent myoglobin-induced renal failure:

• Target urinary output >2 mL/kg/hour 1
• Administer furosemide 0.5-1 mg/kg 1
• Give mannitol 1 g/kg 1
• Infuse crystalloids (lactated Ringer's or 0.9% saline) liberally 1

Post-Crisis Management

Monitor the patient for a minimum of 24 hours in an ICU, high-dependency unit, or recovery unit 1, 5, as recrudescence can occur:

• Continue dantrolene 1 mg/kg IV every 4-6 hours or as needed if signs recur 3
• Transition to oral dantrolene 4-8 mg/kg/day in divided doses for 1-3 days after the crisis to prevent recurrence 3
• Watch for late complications: rhabdomyolysis, acute kidney injury, disseminated intravascular coagulation, compartment syndrome 1, 5

Critical Pitfalls to Avoid

• Do not delay dantrolene administration while waiting for diagnostic confirmation—clinical suspicion is sufficient to begin treatment 4, 5, 6
• Do not assume previous uneventful anesthetics rule out malignant hyperthermia—patients can have multiple normal exposures before developing a crisis 1, 2
• Do not use acidic solutions (5% dextrose, 0.9% saline with additives) to reconstitute dantrolene—only use sterile water 3
• Do not transfer reconstituted dantrolene to large glass bottles—use plastic bags only, as precipitation occurs in some glass containers 3

Follow-Up and Family Counseling

• Refer the patient and family members to a regional or national Malignant Hyperthermia Investigation Unit for in vitro contracture testing (IVCT) and genetic testing 1
• Document the episode thoroughly and ensure the patient receives a medical alert bracelet 5
• Counsel family members that this is an inherited disorder requiring screening and trigger-free anesthesia for all future procedures 2