What is the treatment plan for malignant hyperthermia?

Treatment Plan for Malignant Hyperthermia

Immediately stop all triggering agents (volatile anesthetics and succinylcholine), hyperventilate with 100% oxygen at 2-3 times normal minute ventilation, and administer intravenous dantrolene starting at 2-3 mg/kg, continuing until ETCO2 falls below 6 kPa with normal minute ventilation and core temperature drops below 38.5°C. 1

Immediate Actions (First 5 Minutes)

The survival of your patient depends on the speed of these initial interventions:

• Stop all volatile anesthetics and succinylcholine immediately 1
• Remove the vaporizer from the anesthetic machine—do not waste time changing the entire circuit or machine 1
• Insert activated charcoal filters on both inspiratory and expiratory limbs of the circuit to rapidly eliminate residual volatile agents 1
• Hyperventilate with 100% oxygen at maximum flow, using 2-3 times normal minute ventilation 1
• Declare an emergency and call for help—you will need multiple people to reconstitute dantrolene 1
• Switch to total intravenous anesthesia (TIVA) if surgery must continue 1
• Inform the surgeon and request immediate termination or postponement of surgery 1

Dantrolene Administration (The Definitive Treatment)

Dantrolene is the only specific antidote for malignant hyperthermia and must be given without delay:

• Initial dose: 2-3 mg/kg IV 1, 2
• Reconstitution: Each 20 mg vial requires 60 mL of sterile water and vigorous shaking for up to 5 minutes 1, 2
• Administer each syringe as soon as it is prepared—do not wait for the complete initial dose to be ready 1
• Continue giving additional 1 mg/kg boluses until treatment goals are achieved 1
• The maximum cumulative dose of 10 mg/kg may need to be exceeded in severe cases 1, 2
• Obtain dantrolene from all available sources (pharmacy, nearby hospitals)—at least 36-50 ampoules may be needed for an adult 1

Treatment Goals for Dantrolene Titration:

• ETCO2 < 6 kPa (45 mmHg) 1
• Normal minute ventilation 1
• Core temperature < 38.5°C 1

Critical caveat: Pause dantrolene when goals are achieved, but be prepared to give more if CO2 or temperature rises again (recrudescence) 1

Active Cooling Measures

Hyperthermia enhances calcium release and worsens muscle rigidity, making aggressive cooling essential:

• Administer 2000-3000 mL of chilled (4°C) 0.9% saline IV 1
• Surface cooling: Apply wet, cold sheets, fans, and ice packs to 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

Comprehensive Monitoring

Establish invasive monitoring immediately to guide treatment:

• Continue routine monitoring: SpO2, ECG, non-invasive blood pressure, ETCO2 1
• Measure core temperature continuously 1
• Establish wide-bore IV access with at least two large-bore cannulas 1
• Insert arterial line and central venous catheter for invasive monitoring and frequent blood sampling 1
• Insert urinary catheter to monitor urine output and detect myoglobinuria 1

Laboratory monitoring (obtain immediately and repeat frequently):

• Arterial blood gases (for pH, PaCO2, PaO2) 1
• Serum potassium 1
• Creatine kinase (CK) 1
• Myoglobin (serum and urine) 1
• Glucose 1
• Renal function (creatinine, BUN) 1
• Hepatic function 1
• Coagulation studies (PT, PTT, fibrinogen, D-dimer) 1

Treatment of Metabolic Complications

Hyperkalemia Management

Life-threatening hyperkalemia can cause cardiac arrest:

• Calcium chloride 0.1 mmol/kg IV (e.g., 10 mL of 10% solution = 7 mmol for a 70 kg adult) for cardiac membrane stabilization 1
• Dextrose 50%, 50 mL with 50 units insulin IV (adult dose) to shift potassium intracellularly 1
• Dialysis may be required for refractory hyperkalemia 1

Acidosis Management

Both respiratory and metabolic acidosis must be addressed:

• Hyperventilate to normocapnia as the primary treatment for respiratory acidosis 1
• Sodium bicarbonate IV if pH < 7.2 for severe metabolic acidosis 1

Arrhythmia Management

Tachyarrhythmias are the most common cardiac manifestation:

• Amiodarone 300 mg IV (3 mg/kg) as first-line antiarrhythmic 1
• Beta-blockers (propranolol, metoprolol, or esmolol) if tachycardia persists despite other treatments 1

Myoglobinuria and Renal Protection

Anticipate myoglobinuria and prevent acute kidney injury:

• Target urine output > 2 mL/kg/h 1
• Furosemide 0.5-1 mg/kg IV to maintain diuresis 1
• Mannitol 1 g/kg IV for osmotic diuresis 1
• Crystalloid fluids (lactated Ringer's or 0.9% saline) IV for volume expansion 1
• Sodium bicarbonate to alkalinize urine (myoglobin precipitates less in alkaline urine, and there is no convincing evidence of harm) 1

Disseminated Intravascular Coagulopathy (DIC)

DIC during MH is associated with poor outcomes:

• Empirical treatment with platelets, fresh frozen plasma, and cryoprecipitate 1
• Tranexamic acid is NOT indicated in this situation 1

Compartment Syndrome Monitoring

Any patient with myoglobinuria is at risk:

• Clinical monitoring is the principal method: Assess for limb swelling, muscle softness, peripheral pulses, and peripheral oxygen saturation 1
• In awake patients, pain is the primary symptom 1
• Measure compartmental pressures if compartment syndrome is suspected 1
• Treatment is fasciotomies if compartment syndrome develops 1
• Remember: Creatine kinase levels may not peak for up to 24 hours after the MH event 1

Post-Crisis Management

Immediate Post-Operative Period

If the MH reaction is successfully treated in the operating theater:

• Surgery can be completed under IV anesthesia if no ongoing sequelae require management 1
• Keep the patient sedated until all metabolic derangements are corrected 1
• Wean from ventilatory support once metabolic parameters normalize 1

Monitoring Duration and Location

Recrudescence of MH is well-described and severity-dependent:

• If treated early without dantrolene: Monitor for at least 1 hour in post-anesthesia care unit, then transfer to postoperative ward 1
• If dantrolene was required: Monitor in high-dependency unit or ICU for at least 24 hours 1
• Never discharge within 24 hours of a suspected MH reaction 1
• Continue monitoring for compartment syndrome throughout the 24-hour period 1

Dantrolene Continuation

Post-crisis dantrolene prevents recrudescence:

• Oral dantrolene 4-8 mg/kg/day in 3-4 divided doses for 1-3 days following the crisis 2
• IV dantrolene may be used postoperatively (starting at 1 mg/kg or more) when oral administration is not practical 2

Patient and Family Counseling

Before hospital discharge, comprehensive counseling is mandatory:

• Inform the patient and family about the suspected diagnosis of MH and its implications 1
• Provide written information about the diagnosis and future anesthetic management 1
• Advise all blood relatives to be warned about MH risk and the need to mention this for any hospital admission 1
• Refer to specialized MH investigation units for diagnostic testing (in vitro contracture testing) 1
• Provide MedAlert bracelets and encourage registration with national MH registries 3

Common Pitfalls to Avoid

• Do not delay dantrolene administration while waiting for laboratory confirmation—treat on clinical suspicion 1, 4, 5
• Do not waste time changing the entire anesthetic circuit—simply remove the vaporizer and use activated charcoal filters 1
• Do not stop dantrolene at 10 mg/kg if the patient has not responded—this maximum may need to be exceeded 1, 2
• Do not use calcium channel blockers in combination with dantrolene (risk of hyperkalemia and cardiovascular collapse) 2
• Do not assume a patient is safe after initial stabilization—recrudescence can occur, requiring continued vigilance 1, 5