Sedation/Pain Control/Anesthesia 3: Malignant Hyperthermia Portal
Clinical Considerations
Signs
and symptoms include tachycardia, muscle stiffness, hypercapnia,
tachypnea, cardiac dysrhythmias, respiratory and metabolic acidosis,
fever, unstable/rising BP, cyanosis/mottling, and myoglobinuria.
Acute Phase Treatment
- Discontinue all volatile inhalation anesthetics and succinylcholine. Hyperventilate with 100% oxygen at high flow for at least 10 minutes.
- Administer dantrolene sodium 2 to 3 mg/kg initial bolus IV rapidly with increments up to 10 mg/kg total. Continue to administer dantrolene until signs of malignant hypertension (ie, tachycardia, rigidity, increased end-tidal CO2, and temperature elevation) are controlled. Occasionally, a total dose > 10 mg/kg may be needed. Each vial of dantrolene contains 20 mg of dantrolene and 3 grams mannitol. Mix each vial with 60 mL of sterile water for injection USP without a bacteriostatic agent.
- Administer bicarbonate to correct metabolic acidosis as guided by blood gas analysis. In the absence of blood gas analysis, administer 1 to 2 mEq/kg.
- Actively cool the hyperthermic patient. Use iced NS (not Ringer's
lactate) 15 mL/kg IV every 15 minutes for 3 doses.
- Lavage stomach, bladder, rectum, and open cavities with iced NS as appropriate.
- Cool patient’s body surface with ice and cooling blanket.
- Monitor closely since over-aggressive treatment may lead to hypothermia.
- Dysrhythmias usually respond to treatment of acidosis and hyperkalemia. If they persist or are life threatening, standard antiarrhythmic agents may be used, with the exception of calcium channel blockers, which may cause hyperkalemia and cardiovascular collapse.
- Determine and monitor end-tidal CO2 ; arterial, central, or femoral venous blood gases; serum potassium; calcium; clotting studies; and urine output.
- Hyperkalemia is common. Treat with hyperventilation, bicarbonate (1 mEq/kg), and regular insulin (10 units IV plus 50 mL 50% dextrose solution). Titrate these to potassium level. Life-threatening hyperkalemia may also be treated with calcium administration (2 to 5 mg/kg of CaCl2).
- Ensure urine output of > 2 mL/kg/hour. Consider central venous or pulmonary artery monitoring because of fluid shifts and hemodynamic instability that may occur.
- PEDS: Treat boys younger than 9 years of age who experience sudden cardiac arrest after succinylcholine in the absence of hypoxemia for acute hyperkalemia first. In this situation, administer calcium chloride along with other means to reduce serum potassium. Presume these patients have sub clinical muscular dystrophy.
Post-Acute Phase
- Observe the patient in an ICU setting for at least 24 hours since malignant hyptertension may re-occur, particularly following a fulminate case resistant to treatment.
- Administer dantrolene 1 mg/kg IV every 6 hours for 24 to 48 hours post episode. After that, administer oral dantrolene 1 mg/kg every 12 hours for 24 hours as necessary.
- Monitor ABG, CK, potassium, calcium, urine and serum myoglobin, clotting studies, and core body temperature until values return to normal (ie, every 6 hours). Monitor central temperature continuously until stable.
- Counsel the patient and family regarding malignant hyperthermia. Refer to the Malignant Hyperthermia Association of the United States.
- Fill out an adverse metabolic reaction to anesthesia (AMRA) report.