Diagnosis

Malignant hyperthermia

Etiology

Cause [rrv][fmm]

• Defect in the ryanodine receptor (inherited in autosomal dominant pattern)

• Triggered by anestethic agents: Halothane, sevoflurane, desflurane, succinylcholine

Pathophysiology [rrv]

1. Impaired reuptake of calcium by sarcoplasmic reticulum in muscles

2. Uncontrolled lasting muscle activation

3. ATP depletion --> compromised muscle membrane

4. Severe hyperthermia (core temperature > 44°C) may occur

5. Increased oxygen consumption, carbon dioxide production, worsening metabolic acidosis, heart failure, bowel ischemia, compartment syndrome, myocyte death, rhabdomyolysis myoglobinuria, acute renal failure, life-threatening hyperkalemia and disseminated intravascular coagulation

Complications [rrv]

• Brain damage

• Cardiac arrest

• Death

• Heart failure

• Internal bleeding

• Kidney failure

• Pulmonary edema

• Skeletal muscle degeneration

Epidemiology

Incidence per 100.000 [fmm]

Approach

• Blood test

• Blood gas

• Elevation of end-expired carbon dioxide

• Genetic test

• Muscle biopsy and in vitro contracture test: contracture response to halothane, caffeine, and other drugs (caffeine halothane contracture test)

Treatment

1. Immediate discontinuation of trigger agents (inhalation agents, succinylcholine) [fmm]

2. Hyperventilation to lower ETCO2

3. Dantrolene initial dose 2.5 mg/kg repeated pro re nata, upper limit 10 mg/kg, titrate to tachycardia and hypercarbia, then 1 mg/kg every 4–8 hours for 24–48 hours

4. Cooling by all routes available:

   • Nasogastric lavage

   • Ice Packs to groin, axilla, and neck

5. Treat hyperkalemia and arrhythmias (do not use calcium channel blockers)

6. Insure urine output of 2 ml/kg/hour with mannitol, furosemide, and fluids as needed

7. Monitor blood gases, electrolytes, creatine kinase, blood and urine for myoglobin, coagulation profile

8. Evaluate need for invasive monitoring and continued mechanical ventilation

9. Observe patient in Intensive Care Unit for at least 36 hours

Differential diagnoses

Becker muscular dystrophy, Cocaine toxicity, Cystinosis, Diabetic ketoacidosis, Drug side effects, Duchenne muscular dystrophy, Febrile seizure, Heatstroke, Hyperthyroidism, Muscular dystrophy, Neuroleptic malignant syndrome, Pheochromocytoma, Rhabdomyolysis, Sepsis, Thyrotoxicosis