What Is the First Sign of Malignant Hyperthermia?

 If not treated right away, MH can lead to fatal complications.
If not treated right away, MH can lead to fatal complications.

Malignant hyperthermia (MH) may present clinically either in the operating room (OR) or soon after surgery in the early postoperative period. Usually, there are no signs or symptoms of malignant hyperthermia susceptibility (MHS) until the person is exposed to certain drugs used for anesthesia. In rare cases, people at risk of MH may develop signs of MH after intense physical activity in excessive heat and/or humidity, viral infections, or statin medication (cholesterol medication).

The signs and symptoms of MH can vary in patients; they include:

  • Extremely high body temperature, which can be dangerous
  • Severe muscle rigidity
  • Muscle spasms
  • Rapid and shallow breathing leading to an increase in carbon dioxide levels and a decrease in oxygen levels in the body 
  • Tachycardia (increased heart rate)
  • Irregular and abnormal heart rhythm
  • Excessive sweating
  • Mottled skin (patchy and irregular color of the skin)

How is malignant hyperthermia caused?

Malignant hyperthermia susceptibility (MHS) is caused because of a genetic mutation (genetic defect). The genetic defect is usually not inherited and usually the result of random gene mutation. Mutations of different genes can cause MHS. The most commonly affected gene in MHS is the RYR1 gene; other genes that may be affected are CACNA1S and STAC3.

What happens if malignant hyperthermia is not treated?

If not treated right away, malignant hyperthermia (MH) can lead to serious and fatal complications such as:

  • Brain damage
  • Rhabdomyolysis (muscles can break down and release its contents into the blood)
  • Kidney failure
  • Clotting and bleeding problems 
  • Severe muscle rigidity 
  • Death

How is malignant hyperthermia treated?

Malignant hyperthermia (MH) is required to be treated right away to avoid life-threatening complications. With appropriate treatment, MH resolves in a few days. 

Treatment of MH involves:

  • Halting the procedure and offending anesthesia agent as soon as possible
  • Medication: A medication called Dantrium (dantrolene) inhibits the release of calcium into the muscle, which reduces muscle spasms and rigidity. Medications to correct the body's metabolic imbalance are usually administered.
  • Oxygen: Oxygen therapy is required to increase oxygen levels in the body and reduce carbon dioxide levels.
  • Measures to reduce body temperature: Ice packs, cooling blankets, cold air, and a fan with cool mist and administering chilled intravenous (IV) fluids can help reduce body temperature.
  • IV fluids: Extra fluids would usually be administered intravenously.
  • Close monitoring: The patient is usually admitted for around two days in the intensive care unit (ICU) or longer till their condition improves and the vitals and lab tests (to assess muscle and kidney damage) are normal.

How can malignant hyperthermia be prevented?

If a person is suspected to have malignant hyperthermia (MH), based on family history or medical history, the doctor would use anesthetic medications that don’t cause MH, avoid prescribing triggering medications, and advise certain lifestyle modifications such as avoiding exercising in intense heat or humidity.


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