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Treatment of an Acute MH Crisis
If you suspect an MH crisis in a patient under a triggering anesthesia, follow these steps to manage the MH crisis. Click on each step to view detailed information. Caution: This protocol may not apply to every patient and may require modification depending on specific needs of each patient.
- Look for signs and symptoms
- Call for help and discontinue trigger
- Administer dantrolene
- Administer bicarbonate
- Administer anti-arrhythmic agents if needed - but not calcium channel blockers
- Monitor other variables
- Treat hyperkalemia if needed
- Monitor fluid shifts and and urine output
1. Look for signs and symptoms
Look for signs and symptoms of an MH reaction:
- hypercarbia
- tachypnoea
- tachycardia
- cardiac arrhythmias
- rigidity
- cyanosis/mottling
- unstable or increasing blood pressure
- fever
- respiratory and metabolic acidosis
- myoglobinuria
2. Call for help and discontinue trigger
Call for help! Immediately discontinue all volatile inhalation anesthetics and succinylcholine. Hyperventilate with 100% oxygen at high gas flows, at least 10 L/min. A clean circuit should be used if possible, without delaying other important treatment.
3. Administer dantrolene
Immediately begin dantrolene sodium 2.5 mg/kg. Rapidly administer the initial bolus intravenously with supplemental increments up to 10mg/kg. A central venous line is preferred in order to avoid peripheral venous thrombosis. Each vial of dantrolene contains 20 mg dantrolene and 3 g mannitol. One vial should be mixed with 60 mL of sterile water for injection (USP). Continue to administer dantrolene until signs of MH (e.g. hypercarbia, rigidity, tachycardia and fever) are controlled. Occasionally more than 10 mg/kg dantrolene total dose may be needed, but clinical reassessment is suggested.
4. Administer bicarbonate
Administer bicarbonate to correct metabolic acidosis as guided by blood gas analysis. In the absence of blood gas analysis, 1-2 mEq/kg should be administered.
5. Administer anti-arrhythmic agents if needed
Arrhythmias will usually respond to treatment of acidosis and hyperkalemia. If they persist or are life-theatening, standard anti-arrhythmic agents may be used. If dantrolene has been administered, do not use calcium channel blockers as they can interact to produce fatal hyperkalemia and cardiovascular collapse.
6. Monitor other variables
Determine, monitor and treat:
- end tidal CO2
- arterial, central or femoral venous blood gases
- serum potassium
- calcium
- CK
- serum and urine myoglobin
- blood cultures
- thyroid function studies
- clotting studies
- urine output
Respiratory and renal failure and disseminated intravascular coagulation may need appropriate supportive measures.
7. Treat hyperkalemia if needed
Hyperkalemia is common and should be treated with hyperventilation, bicarbonate and intravenous glucose and insulin (e.g. 10 units regular insulin in 50 mL 50% glucose titrated to potassium level). Life-threatening arrhythmias from hyperkalemia should be treated with IV calcium (10-30 mg/kg of IV calcium chloride).
8. Monitor fluid shifts and and urine output
Ensure urine output of greater than 2 mL/kg/hr by hydration and/or administration of mannitol or furosemide. Remember that each vial of dantrolene contains 3 grams of mannitol. Consider central venous or pulmonary arterial monitoring because fluid shifts may result in hemodynamic instability.
