An autosomal dominant genetic condition of the ryanodine receptor 1 (RYR1) in the long arm of chromosome 19 that causes a hyper-metabolic state triggered by inhalation anesthetics and suxamethonium. Characterized by hyperthermia and severe muscle contraction.

- Hypercarbia
- Tachypnea
- Dysrhythmias
- Tachycardia
- Maseter muscle spasm/rigidity
or fasciculation
- Increased temperature
- Sweating
- Electrolyte imbalances
- Metabolic and respiratory acidosis
- Disseminated intravascular coagulation (DIC)
- Rhabdomyelisis
- Myoglobinuria
- Elevated creatinine phosphokinase

The primary MH defect resides in the skeletal muscle at the level of calcium release from the sarcoplastic reticulum of the muscle cell. The resulting hypercalcemia leads to hypermetabolism, which in turn results in increased sympathetic activity, increased carbon dioxide production, increased oxygen consumption, and disruption of the cell membranes. Muscle tissue is unable to return to a resting state in the susceptible patient, and because of this the primary signs of MH begin to appear (AORN 2012, p. 623-625).

- stay calm
- discontinue triggering agents
- give 100% O2 at 10L/min
- call for help. get MH cart and Crash cart. Call Malignant Hyperthermia Association of the United States (MHAUS) for expert help.
- Give Dantrolene Sodium.
- start cooling measures
- assist anesthesia provider with obtaining blood samples and medications to control electrolyte imbalances
- prepare for transfer once patient is stable.

Family and health history


Genetic testing


Contraction testing