Malignant Hyperthermia

 

         Hypermetabolic state of skeletal muscle secondary to idiopathic block of calcium re-entry into the sarcoplasmic reticulum

         Epidemiology

1.       Carries a multifactorial genetic predisposition

2.       Incidence is 1/15,000 pediatric anesthetic administrations; 1/40,000 adult anesthetic administrations

3.       50% of cases are seen in patients who had undergone previous anesthesia without malignant hyperthermia

4.       Having any relative with a history places patient at risk

5.       Related traits include heavy musculature, Duchenne muscular dystrophy, and scoliosis

6.       Mortality is up to 30%

         Dx (early):  increasing end tital pCO2, tachycardia, arrhythmias

1.       Progresses to coagulopathy (DIC), increasing metabolic acidosis, decreasing pO2, pulmonary edema, increasing body temperature (at a rate of 1 C/5 minutes, up to 44 C), limb muscle rigidity, and rhabdomyolysis

2.       Terminal events are hypotension, bradycardia, and cardiac arrest

         Prevention:

1.       Identify patients at risk

2.       Use non-halogenated anesthetics and non-depolarizing blockers

3.       Prophylactic dantrolene 4-8 mg/kg/day for 1-2 days prior to planned anesthetic

         Intraoperative episode

1.       Discontinue causative agent and change ventilator tubing

2.       Give dantrolene 2.5 mg/kg IV.  Additional doses up to total of 10 mg/kg may be used

3.       Hyperventilate patient with 100% O2

4.       Begin surface and cavity cooling

5.       Give bicarb as needed for acidosis (1-2 meq/kg)

6.       Administer IV insulin and glucose to lower potassium released by damaged muscle

7.       Treat arrhythmias (procainamide)

8.       Volume load and give osmotic diuretics to prevent renal damage from CPK