Genetic Testing for Anesthesia Allergy: Assess Surgical Risk and Prevent Malignant Hyperthermia

Many surgical procedures require General Anesthesia to ensure that patients remain unconscious and pain - free during surgery. This process is carefully managed by an Anesthesiology team, including anesthesiologists and nurse anesthetists.

Although modern anesthesia is highly safe, some patients carry genetic risks that may cause severe reactions to certain anesthetic agents. This condition is known as Malignant Hyperthermia (MH), often referred to as an “anesthesia allergy.”

The good news is that genetic testing is now available to assess this risk before surgery, enabling personalized and safer anesthesia planning.

 

What Is Malignant Hyperthermia?

Malignant Hyperthermia is a life-threatening reaction triggered by certain anesthetic agents, particularly inhalational anesthetics and the muscle relaxant Succinylcholine.

These agents cause uncontrolled calcium release in muscle cells, leading to:

      ๐  Rapid metabolism

      ๐  Sudden rise in body temperature

      ๐  Severe muscle rigidity

Key Symptoms During Surgery

      ๐  Sudden high fever (up to 40–43°C)

      ๐  Rapid heart rate and breathing

      ๐  Muscle stiffness

      ๐  Muscle breakdown (rhabdomyolysis), metabolic acidosis, and high potassium levels

      ๐  Cardiac arrhythmias

According to CPIC/PharmGKB guidelines, triggering agents include:

      ๐  Sevoflurane

      ๐  Desflurane

      ๐  Isoflurane

      ๐  Halothane

All inhalational anesthetics may trigger MH.

In contrast, intravenous anesthetics such as:

      ๐  Propofol

      ๐  Ketamine

are considered safe for patients at risk.

 

How Common Is Malignant Hyperthermia?

MH is rare, occurring in approximately 1 in 5,000 to 1 in 100,000 anesthesia cases. However, it develops rapidly and can be extremely severe.

Mortality Rates

      ๐  Before the use of Dantrolene:
Mortality rate > 80%

      ๐  Present day (early diagnosis + Dantrolene):
Mortality reduced to < 5–10%

The key difference lies in early detection and preparedness.

 

Genetic Causes of Malignant Hyperthermia

MH is a pharmacogenetic disorder caused by mutations in genes involved in muscle calcium regulation.

Key Genes Involved

      ๐  RYR1
The primary gene; responsible for ~50 - 70% of MH cases

      ๐  CACNA1S
Less common (~1%)

      ๐  STAC3
Associated with certain muscle diseases and MH risk

 

Inheritance Pattern: Why It Matters for Families

MH follows an autosomal dominant inheritance pattern, meaning:

      ๐  If one parent carries the mutation, each child has a 50% chance of inheriting it

      ๐  First-degree relatives should be evaluated

      ๐  Carriers may remain asymptomatic until exposed to triggering anesthesia

 

Current Diagnostic Methods

1. Genetic Testing

A blood test used to detect mutations in RYR1, CACNA1S, and STAC3:

      ๐  Non-invasive and convenient

      ๐  Can be performed before surgery

      ๐  Identifies patients as “MH-susceptible”

2. Muscle Testing (IVCT / CHCT)

      ๐  In Vitro Contracture Test (IVCT)

      ๐  Caffeine-Halothane Contracture Test

These are considered the gold standard for diagnosis:

      ๐  Require muscle biopsy

      ๐  Performed in specialized centers

      ๐  Used when genetic results are inconclusive or family history is strong

 

Who Should Be Tested?

According to CPIC/PharmGKB guidelines, testing is recommended for individuals who:

      ๐  Have experienced abnormal reactions during anesthesia

      ๐  Have a family history of MH

      ๐  Have muscle disorders such as Central Core Disease or Multiminicore Disease

      ๐  Have unexplained fainting or muscle breakdown

      ๐  Are planning surgery with inhalational anesthesia and have risk factors

 

How Genetic Testing Improves Surgical Safety

If a patient is identified as high-risk, the medical team can:

      ๐  Use Total Intravenous Anesthesia (TIVA) instead of inhalational agents

      ๐  Prepare Dantrolene in advance

      ๐  Inform family members for risk awareness and screening

With modern advances, mortality has dropped dramatically from over 80% to less than 5–10%, highlighting the importance of early awareness and prevention.

 

Precision Medicine: Knowing Your Risk Before It Happens

Genetic testing for anesthesia sensitivity is part of Precision Medicine, which enables healthcare providers to tailor treatment based on an individual’s genetic profile.

Although MH is rare, its severity makes preoperative risk assessment extremely valuable, especially for patients with known risk factors or those planning surgery.

 

Conclusion

Genetic testing for anesthesia sensitivity represents a critical advancement in patient safety. By identifying risks before surgery, healthcare providers can prevent life-threatening complications and deliver truly personalized care.

 

Source : Bangkok Hospital Phuket

**Translated and compiled by ArokaGO Content Team