Malignant Hyperthermia

Overview

Malignant hyperthermia is a severe reaction triggered by certain anesthesia drugs, characterized by dangerously high body temperature, muscle rigidity, rapid heartbeat, and other symptoms. It can be life-threatening without immediate intervention. The condition, known as malignant hyperthermia susceptibility (MHS), is often inherited but can also occur due to spontaneous genetic mutations. Genetic testing can identify individuals with the predisposing gene.

Treatment for malignant hyperthermia involves administering medications like dantrolene, utilizing cooling methods such as ice packs, and providing supportive care. Prompt recognition and intervention are essential in managing this condition and preventing potentially fatal complications.

Symptoms

In most cases, indications of susceptibility to malignant hyperthermia remain absent until exposure to specific anesthesia drugs. Manifestations of malignant hyperthermia can vary, occurring during anesthesia or shortly after surgery recovery. These signs may include:

• Accelerated heart rate
• Irregular heart rhythm
• Rapid, shallow breathing with issues related to low oxygen and high carbon dioxide levels
• Patchy, irregular skin color (mottled skin)
• Severe muscle rigidity or spasms
• Dangerously elevated body temperature
• Excessive sweating

Individuals predisposed to malignant hyperthermia may experience reactions following strenuous physical activity in high heat or humidity, during viral illnesses, or while taking statin medications. Even if no serious reaction manifests initially with certain anesthesia drugs, the susceptibility persists for future exposures, necessitating the use of alternative anesthesia medications to avoid triggering adverse reactions.

For individuals with a family history of malignant hyperthermia, informing doctors and anesthesia specialists (anesthesiologists) is crucial when anesthesia is required. This ensures the consideration of alternative drugs to mitigate the risk associated with malignant hyperthermia.

Causes

Malignant hyperthermia susceptibility (MHS) is a genetic disorder primarily caused by mutations in genes such as RYR1, CACNA1S, and STAC3, although other genes may also be involved. This condition increases the risk of experiencing malignant hyperthermia, a potentially life-threatening reaction triggered by certain anesthesia drugs. While MHS is typically inherited, with one parent passing on the affected gene, in some cases, the mutation arises spontaneously without any familial history. Exposed individuals may face complications if they carry these genetic variants, highlighting the importance of understanding one’s genetic predisposition in medical settings involving anesthesia.

Risk factors

The likelihood of inheriting the genetic disorder MHS is elevated when there is a family history of the condition. Key points regarding risk factors include: 

• Inheritance pattern: MHS follows an autosomal dominant pattern, requiring the inheritance of a single altered gene from a parent to be affected. If one of your parents carries the gene change causing MHS, your probability of having MHS is 50%. 
• Family history influence: Having other relatives with MHS increases your likelihood of having the disorder. 

Additional risk factors for malignant hyperthermia include: 

• History of suspected events: Your risk is heightened if you or a close relative has a history of events suspected to be malignant hyperthermia during anesthesia. 
• Rhabdomyolysis: Increased risk is associated with a history of rhabdomyolysis (muscle tissue breakdown), which can be triggered by intense exercise in extreme heat and humidity or when taking a statin drug. 
• Certain muscle diseases: The risk is elevated if you or a close relative has specific muscle diseases and disorders resulting from inherited gene changes.