What is malignant hyperthermia?

Malignant hyperthermia (MH) is a genetic disorder that is rare but potentially can affect anyone. It is a mild to severe and potentially fatal reaction to particular drugs that are often used during surgery1,2. This reaction occurs in response to some anaesthetic gases which are used to block the sensation of pain during surgical procedures. It is characterized by otherwise unexplained changes of patient’s breathing gases, heart rate and later on of increase in body temperature1,3.

How common is malignant hyperthermia?

MH is a genetic disorder; 1 in every 2,000-3,000 people is susceptible to malignant hyperthermia1,2. It occurs in 1 of 10,000 anaesthetic procedures4. Males are 2,5-4,5 times more likely to develop MH than females1.

What causes malignant hyperthermia?

MH is an inherited disorder of skeletal muscle cells1. In most cases, MH is caused by the use of certain anaesthetics and muscle relaxants in those who are susceptible3. Patients susceptible to MH have a faulty muscle receptor that activates muscle contraction2. In an MH crisis, the medications lead the receptor to open too long with the effect of an ongoing muscle activation1. Thus the patient’s body temperature rises rapidly1.

How do I know if I am susceptible to malignant hyperthermia?

As almost all individuals with malignant hyperthermia susceptibility (MHS) have no symptoms during daily life, specific testing is needed to diagnose MHS5. The standard test for MHS diagnosis is the in vitro contracture test (IVCT) using muscle biopsy. Another alternative to the invasive contracture test is a molecular genetic test. Both tests require specialized testing centres and are offered to following patients:

  • patients who have undergone a suspected MH crisis (in order to prevent future MH episodes and to screen family members who also may be affected by this genetic disorder) 1
  • patients with history of MH in their families (in order to confirm or exclude an MHS)1
  • patients with specific predisposing factors (e. g. like some muscular diseases or specific enzyme levels)1
  • If you belong to one of the described patient groups, please talk to your doctor.

What happens during a malignant hyperthermia crisis?

During an MH crisis the patient’s muscles begin to contract abnormally. In order to provide the muscles with extra energy needed for these contractions, the patient’s body has to work harder. According to this, the demand for oxygen is higher. The body tries to supply more oxygen by increasing the heart rate. Subsequently, more CO2 is produced. In addition to that, patients may also begin to sweat a lot, their blood pressure rises and their muscles (especially chewing muscles) may become rigid. Later on, the patient may also have a rapid rise in core body temperature (hyperthermia)1,3,5. However, the symptoms of MH are highly variable, and range from mild episodes to severe crisis1.

What is the treatment for malignant hyperthermia?

The essential of MH treatment is the early recognition of symptoms and the immediate discontinuation of trigger agents5. The anaesthesiologist replaces the anaesthetics with alternative, non-triggering anaesthetics and administers drugs to combat the underlying processes1. The patient is continuously monitored during surgery, while supportive measures are taken to prevent accompanying complications. These include providing oxygen, administering fluids, and cooling the patient with wet, cold sheets, fans and ice packs5.