© Shutterstock 

Malignant hyperthermia explained -

Malignant hyperthermia (MH) is a rare type of clinical syndrome that occurs in response to particular medications used during general anesthesia.

© Shutterstock 

A genetic disorder -

MH is an inherited genetic disorder triggered by certain anesthetics and/or the drug succinylcholine (a muscle relaxant).

© Shutterstock 

Routine surgery -

The reaction is most often experienced in individuals undergoing routine surgery. It can also occur in the early postoperative period.

© Shutterstock 

How does MH occur? -

In susceptible individuals, the medications induce the release of stored calcium ions within skeletal muscle cells. This results in a massive metabolic reaction upon exposure to the triggering agents.

© Shutterstock 

Symptoms -

The resulting increase in calcium concentrations within the cells cause the skeletal muscle fibers to contract.

© Shutterstock 

Other signs of MH -

Additional symptoms of MH include body temperatures of up to 41°C (107°F). Body temperature elevation is a dramatic but often late sign of MH.

© Shutterstock 

Muscle rigidity -

Muscle rigidity is commonplace during the onset of MH.

© Shutterstock 

Heart rate -

A fast heart rate, or tachycardia, is also indicative of malignant hyperthermia.

© Shutterstock 

Additional indicators -

Other signs of MH include acidosis (acid buildup), tachypnea (rapid breathing), and hyperkalemia (elevated blood potassium).

© Shutterstock

Progression of MH -

The progression of the syndrome may be rapid and dramatic. Or its advance maybe slower and not become manifest until after several hours of anesthesia.

© Shutterstock 

Potentially fatal -

MH can induce system-wide organ failure. In some instances, the syndrome is fatal. 

© Shutterstock 

A serious condition -

Indeed, malignant hyperthermia can cause death. That's why it must be treated rapidly in order to avoid a fatal outcome.

© Shutterstock 

What are the triggers? -

All inhalation anesthetics except nitrous oxide are triggers for MH. According to the Malignant Hyperthermia Association of the United States (MHAUS), the known triggers of MH are: inhaled general anesthetics, halothane, desflurane, enflurane, ether, isoflurane, sevoflurane, and the previously mentioned succinylcholine.

© Shutterstock 

Malignant hyperthermia gene -

Why are some people so susceptible to these drugs? In most cases, the gene that puts you at risk of malignant hyperthermia is inherited. Genetic testing can reveal whether you have an affected gene.

© Shutterstock 

Genetic testing -

The gene change (mutation) that makes you susceptible to malignant hyperthermia is identified using genetic testing. If you have an affected gene, this genetic disorder is called malignant hyperthermia susceptibility (MHS).

© Shutterstock 

Muscle biopsy -

An alternative method of susceptibility testing is a muscle biopsy, also known as a contracture test. This procedure involves the surgical removal of a small piece of muscle tissue for lab analysis. Results are ascertained by the specimen being exposed to triggering chemicals for malignant hyperthermia to determine how the muscle contracts.

© Shutterstock 

Family genes -

If you or someone in your family has MHS or you think you may be at risk of malignant hyperthermia, it's imperative to inform your healthcare provider and anesthesiologist before you get anesthesia.

© Shutterstock 

Information an anesthesiologist needs -

Imparting this vital information before going under the knife allows an anesthesiologist to select drugs that do not trigger malignant hyperthermia, and which may be used as part of your anesthesia.

© Shutterstock 

Treatment of MH -

If triggered during an operation, an immediate response is needed to stop the rapid progressive series of chain reactions typical of MH. Healthcare facilities that use known triggering agents must be fully prepared to treat it.

© Shutterstock 

Use of medications -

Medications used in response to malignant hyperthermia include dantrolene. It's administered to treat the reaction by stopping the release of calcium into muscles.

© Shutterstock 

Oxygen feed -

Oxygen may be fed to a patient suffering from MH reactions. This can be through a face mask or more likely given through a tube placed in the windpipe (trachea).

© Shutterstock 

Extra fluids -

Extra fluids may be given through an intravenous line, including chilled fluids to help reduce body temperature.

© Shutterstock 

Supportive care -

A patient recovering from MH may require a few extra days on an intensive care ward so that their temperature, blood pressure, heart rate, breathing, and response to treatment can be carefully monitored.

© Shutterstock 

Malignant hyperthermia complications -

Over and above the dangers of the condition itself, if not treated promptly, MH can result in major complications. One of these is rhabdomyolysis, a rare condition that causes muscles cells to break down.

© Shutterstock 

Renal problems -

Kidney damage or failure is another potential side effect of malignant hyperthermia.

© Shutterstock 

Blood clot -

Possible complications from MH extend to problems with blood clotting and/or excessive bleeding.

© Shutterstock 

Mortality rate -

Prognosis is poor if malignant hyperthermia is not aggressively dealt with. When MH was first recognized as a complication of anesthesia, the mortality rate was 70-80%, notes the National Library of Medicine.

© Shutterstock 

Morbidity rate -

The morbidity rate of MH in the United States is currently 34.8%. This figure emphasizes the need for continuing education of anesthesiologists on the most effective way to diagnose and treat the condition.

© Shutterstock 

Excellent prognosis -

The good news is that nowadays, with early detection of an MH episode using capnography (a procedure that helps to identify situations that can lead to hypoxia), prompt use of the drug dantrolene, and the introduction of diagnostic testing, the mortality rate is estimated to be less than 5%.

Sources: (National Library of Medicine) (National Organization for Rare Diseases) (U.S. Pharmacist) (MHAUS) (Mayo Clinic)

See also: Common medication mistakes you should avoid

© Shutterstock