Reviewed By: Pramod Kerkar, MD, FFARCSI

Is Malignant Hyperthermia Rare?

Malignant hyperthermia is a rare condition that arises when a patient receives general anesthesia, which is used for surgeries and other invasive procedures. It is an inherited disorder with more than 80 genetic defects being associated with this condition. This rare condition can also be triggered by the muscle relaxant known as succinylcholine which is a part of general anesthesia. It is normally used to cause skeletal muscle relaxation during surgical procedures so as to allow for tracheal intubation or mechanical ventilation. Exposure to the general anesthetics or succinylcholine, the muscle relaxant, leads to severe reactions which can be fatal if immediate treatment is not administered. The condition is rare since it affects at least one person in every five thousand people (1:5,000) or one person in every fifty thousand to one hundred thousand individuals (1:50,000-10,000).

When Does Malignant Hyperthermia Occur?

Prior to exposure of general anesthetics or succinylcholine, a patient exhibits no symptoms of malignant hyperthermia. Therefore, the condition only develops if someone is exposed to these drugs, which are used during surgical procedures. The reaction to these drugs can occur from inhalation in their gaseous form, or when they’re given intravenously or in tablet form. Regardless of how they are administered, provided that a patient has this genetic disorder, they will have a negative reaction towards the anesthetic medications. Malignant hyperthermia is characterized by muscle rigidity, high fever, acidosis (increased acidity in the body), high metabolism and calcium homeostasis in skeletal muscles. Other than that, a patient can also experience tachycardia, hypercapnia and fast heartbeat rate.

Who Can Get Malignant Hyperthermia?

It is difficult to identify who has the genetic disorder of malignant hyperthermia as patients’ exhibits no symptoms until they’ve been exposed to anesthetics. Therefore, patients with malignant hyperthermia susceptibility are those who have abnormalities in their genetic composition which causes them to have severe reactions to general anesthesia and succinylcholine. It could be anyone; a child, male or female patient. If a parent, child or sibling has the condition, then there is a 50% probability that you are susceptible to the condition as well. If the patient is a close relative such as an uncle, aunt, cousins, grandparent or grandchildren, the probability of developing the condition decreases to 25%. In terms of gender, males are more likely to develop malignant hyperthermia compared to females.

Important Facts About Malignant Hyperthermia

Malignant hyperthermia is as a result of an autosomal dominant gene which can either be inherited or be as a result of gene mutation. These gene has been identified as the type 1 ryanodine receptor (RYR1), which is a calcium release channel gene. The RYR1 gene accounts for about 50% of cases of malignant hyperthermia, whereas 1% is as a result of the CACNA1S gene. There are at least six forms of malignant hyperthermia, which are established depending on the gene resulting in the reactive response to general anesthetics. Other disorders associated with malignant hyperthermia are central core disease (CCD), hemaline rod myopathy, multiminicore disease (MMD), exertional rhabdomyolysis (ER), and exertional heat illness (EHI). Malignant hyperthermia (MH), is also known as malignant hyperpyrexia.

Some of the major anesthetics which can instigate a malignant hyperthermia reaction include; desflurane, isoflurane, sevoflurane and the muscle relaxant succinylcholine. The drugs are used to block the sensation of pain and in place of succinylcholine, its purpose is to temporarily paralyze the patient for surgical procedures.

Conclusion

People who have a severe reactive response to general anesthetics and succinylcholine are said to be malignant hyperthermia susceptible. As long as a patient is not exposed to the specific medications which trigger the condition, he/she can live their entire life without experiencing any problems. Genetic testing can be done to identify whether a patient is susceptible to malignant hyperthermia if the disorder runs in the family, so as to be on the safe side. A patient with this rare genetic disorder needs immediate medical response in case they experience any episodic reaction to anesthetic or muscle relaxant succinylcholine.

Pramod Kerkar

Written, Edited or Reviewed By:

, MD,FFARCSI

Pain Assist Inc.

Last Modified On: November 15, 2018

This article does not provide medical advice. See disclaimer

Sign Up for Our Newsletter

We'll help you live each day to the healthiest