What is malignant hyperthermia?

Malignant hyperthermia (MH) is a rare, potentially life threatening condition that usually occurs during surgery. Susceptibility to malignant hyperthermia is genetic1, and around 1 in every 3,000 people is susceptible to MH2.

What causes malignant hyperthermia?

Patients who are susceptible to MH have a ‘faulty’ receptor in their muscle cells which reacts abnormally in response to certain anaesthetics and muscle relaxants. The anaesthetic triggers the receptor to open when it should not, leading to an increase in the release of calcium into muscle cells. This increase in calcium causes their muscle cells to contract, raising the body’s temperature and initiating an MH crisis1.

What happens during a malignant hyperthermia crisis?

During a MH crisis the patient’s muscles begin to contract abnormally. To provide the muscles with the extra energy needed for these contractions, the patient’s body has to work harder. This means more oxygen is required. Subsequently, his/her heart rate increases and more carbon dioxide is produced. Patients may also begin to sweat a lot, their blood pressure rises and their muscles may become rigid. Later on, the patient may also have a rapid rise in his/her core body temperature (hyperthermia)1,3,4.

What is the treatment for malignant hyperthermia?

Once MH has been identified, the anaesthesiologist administers appropriate treatment as soon as possible. Anaesthesia changes to alternative, non‑triggering anaesthetics (before the termination/postponement of surgery). The patient is continuously monitored, while measures are taken to treat the symptoms of the MH crisis. These include providing oxygen, administering fluids, and cooling the patient with wet, cold sheets, fans, and ice packs. The patient is monitored for at least 24 hrs after completion of surgery as MH can recur after an initial MH crisis3,4.

The current licensed treatment for MH is dantrolene sodium IV. Since the introduction of dantrolene sodium IV in 1980, survival rates of MH have increased from 20–30% to approximately 95%4.

The family of a patient susceptible to MH can be offered testing, which consists of an in vitro muscle contracture test using muscle biopsy1,4. For further information about MH and its treatment, please talk to your doctor or pharmacist.