Malignant hyperthermia very rare, say anaesthetists

October 10, 2017

Malignant hyperthermia very rare, say anaesthetists

Parents can be reassured that their children are at very low risk of suffering a malignant hyperthermia reaction to an anaesthetic, says specialist anaesthetist Dr Terasa Bulger. “And should they happen to suffer such a reaction, then there is a highly effective antidote drug available to assist,” she says.

A member of the Australian and New Zealand College of Anaesthetists (ANZCA), Dr Terasa Bulger works at Palmerston North Hospital and is head of the national unit for malignant hyperthermia. She makes her comments in light of the reported case of a Christchurch child who suffered brain damage in what may have been a malignant hyperthermia reaction.

“Malignant hyperthermia is an extremely rare reaction to commonly used anaesthetic drugs where the body produces too much heat, which can lead to damage of the organs.

“However, it occurs in only one of 10,000-50,000 general anaesthetics and the antidote drug dantrolene has dramatically decreased malignant hyperthermia mortality,” Dr Bulger explains.

“Before dantrolene was available, the mortality rate for a person suffering a malignant hyperthermia reaction was 60-70 per cent. Now, it is less than one per cent.

“All locations where the triggering anaesthetic drugs are administered must have dantrolene available,” Dr Bulger says.

“Anaesthetists undergo regular training and drills to practise responding to a malignant hyperthermia crisis. When someone is known to be at risk of developing malignant hyperthermia, there are safe alternative anaesthetic drugs that can be used.

“It is possible to diagnose whether a person might be at risk of malignant hyperthermia. However, this involves an invasive muscle biopsy test. Genetic (blood) testing is available, but it is very complex with over 50 possible mutations associated with malignant hyperthermia on three different genes.

“This makes it impractical to conduct population-based screening for this risk factor,” she says.

“Malignant hyperthermia is passed on through the family. It affects males and females equally, and can occur in every ethnicity. In New Zealand, there are more Maori than Pakeha with the disease, owing to a very large Maori family with malignant hyperthermia. A person with malignant hyperthermia has a 50 per cent chance of passing that risk on to each child that they have.

“Malignant hyperthermia can also occur in patients with no family history of the disorder when a spontaneous genetic mutation arises in that person, though this is very uncommon.

“People susceptible to malignant hyperthermia appear completely normal until they are exposed to the triggering anaesthetic drugs. The most important factors in keeping patients safe from malignant hyperthermia are the ready availability of dantrolene and the excellent training of anaesthetists in responding to the crisis.

“Patients from affected families will usually be aware of the family history and safe alternative drugs can be administered,” Dr Bulger says.

ANZCA is responsible for setting standards of clinical practice as well as for the training, examination and specialist accreditation of anaesthetists and pain medicine specialists in New Zealand and Australia.

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