Malignant hyperthermia is a potential side effect or complication that may arise in patients who have received general anesthesia. This adverse event typically occurs during surgery and other invasive procedures. Treatment aims to provide relief and prevent any worsening symptoms.

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Malignant hyperthermia is a hereditary condition that affects about 1 in 100,000 adults and 1 in 30,000 children. The National Organization for Rare Disorders (NORD) notes that acute malignant hyperthermia affects all ethnic groups, with a mean age of 21–23 years. However, it is difficult to estimate incidence rates, as it is challenging for clinicians to define mild malignant hyperthermia events.

Without prompt treatment, malignant hyperthermia can be life threatening. Health experts believe this may be due to alterations in the RYR1 gene, which is responsible for muscular function. Treatment includes medications and supportive care.

In this article, we will explore the various treatment options for malignant hypothermia.

Malignant hyperthermia describes a severe reaction to specific anesthetic agents. Symptoms may include rapid heart rate, high temperature, muscle spasms, and hyperkalemia. If a person develops symptoms of malignant hyperthermia while under anesthesia, the doctor will try to end the surgery and discontinue the triggering agent.

The doctor or anesthesiologist will then administer intravenous (IV) Dantrolene. They will likely try to administer the drug via continuous rapid IV push as soon as they notice a reaction. They can also use Dantrolene preperatively or postoperatively to help prevent signs of malignant hyperthermia in susceptible individuals.


Dantrolene is a type of muscle relaxant that works by stopping some electrical impulses traveling within muscles. Specifically, it interacts with the ryanodine receptor 1 and lowers the amount of calcium present in skeletal muscle. This helps reduce muscle rigidity and restore body temperature.

The Malignant Hyperthermia Association of the United States (MHAUS) recommends that all facilities administering agents that could trigger malignant hyperthermia should always have Dantrolene.

Examples of malignant hyperthermia-triggering anesthetic agents include the paralytic drug succinylcholine as well as the following anesthetic gases:

  • isoflurane
  • desflurane
  • sevoflurane
  • halothane

Risks or side effects

Some common side effects of using Dantrolene may include:

To treat the unusually high body temperature associated with malignant hyperthermia, a healthcare professional will recommend the following:

  • Oxygen: A healthcare professional will give oxygen through a face mask or tube if a person has breathing difficulty or their arterial blood oxygen is below average. Oxygen therapy can help restore normal oxygen levels following lung distress due to malignant hyperthermia.
  • Body cooling aids: Using cooling blankets over and under the patient and applying ice packs can help reduce normal body heat. This is effective if the body temperature is higher than 101°F, or 38.5°C. Health experts recommend that ice may be a better cooling aid.
  • Medications for cardiac arrhythmia: A healthcare professional may administer medications to reduce the frequency of episodes and stabilize normal electrical conduction. Health experts recommend that clinicians avoid administering beta-blockers with Dantrolene due to its cardiac depressant effects.
  • IV Fluids: If a person has moderate to severe dehydration, IV fluids can help replace body fluids and other important nutrients. Examples of IV fluids include dextrose solution, saline, and lactated Ringer’s solution.
  • Calling a malignant hyperthermia helpline: The MHAUS recommends that all healthcare professionals in the United States call the malignant hyperthermia hotline at 800-644-9737. Those outside the United States can call 001-209-417-3722.

A person with malignant hyperthermia usually requires hospitalization. During this period, the doctor will monitor their vital signs, such as their oxygen level, heart rate, blood pressure, temperature, and response to treatment. The healthcare team will continue administering supportive care until a person’s vital signs are within normal range.

People may experience different symptoms of malignant hyperthermia. A person may develop symptoms during or after surgery, as well as during the recovery period.

The doctor will administer treatment immediately if a person develops symptoms under anesthesia. Some common symptoms of malignant hyperthermia include:

  • rigid muscles or muscular spasms
  • bleeding
  • dark or brown urine
  • fast heart rate, also known as tachycardia
  • cardiac arrest
  • difficulty breathing
  • high body temperature
  • rapid breathing, also known as tachypnea
  • unusual skin coloration
  • hyperkalemia

Evidence indicates that a person may not have an episode with every exposure to a triggering agent. Symptoms may depend on genetic predisposition, the dose of the triggering agent, and the duration of exposure.

Evidence suggests that many people susceptible to malignant hyperthermia are unaware until their exposure to a triggering anesthetic agent.

People experiencing malignant hyperthermia have favorable outlooks if medical professionals identify symptoms and administer treatment immediately. With prompt treatment, a person can recover from malignant hyperthermia without potential life threatening outcomes.

If a person has a family history of malignant hyperthermia, health experts consider them susceptible. For such individuals, the MHAUS recommends alternative anesthetic agents, such as:

Malignant hyperthermia refers to a reaction to specific anesthetic agents that doctors may administer during surgery. Possible symptoms include fever, fast heart rate, breathing difficulty, and muscle spasms.

Treatment for malignant hyperthermia aims to provide relief and prevent any worsening symptoms. Treatment typically includes administering the muscle relaxant Dantrolene, with supportive care such as oxygen therapy, cooling aids, and IV fluids.

Many people with malignant hyperthermia experience favorable outcomes when doctors immediately recognize the condition and administer prompt treatment. If a person has a family history of malignant hyperthermia, they should discuss it with a doctor prior to receiving anesthesia. The healthcare professional will then administer anesthesia that is safe to use for a person susceptible to malignant hyperthermia.