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Who gets MH and why?

MH is hereditary; therefore it is passed on through the family. It occurs equally in males and females and the gene changes that cause it are found in every ethnic group. Someone at risk of MH has a 50-50 chance of passing on the risk to their children.

Is MH common?

An MH reaction during anaesthesia is a rare event, occurring in 1 in 30,000- 200,000 general anaesthetics.

Is there a cure for MH?

There is no cure for MH; if you are at risk of MH, the management involves avoiding the triggering agents during anaesthesia.

I was tested negative for MH but can MH skip generations?

No, if you are negative, your children and their children are all negative.

I have been told a relative has MH, what should I do?
Please read more about MH in our section for patients and relatives. This section includes a downloadable form which you should complete and take to your GP as soon as possible. If you have a close family relative with MH it is likely you will be referred for further tests.
I have had an uneventful anaesthetic in the past, does this mean I do not have MH?
No. Triggering anaesthetics do not necessarily cause an MH crisis every time someone at risk is given them. We know of one patient who had 13 uneventful anaesthetics before they had an MH reaction.
Where can I be screened for MH?

St James’s University Hospital in Leeds, a world-leading centre for MH, is the only centre in the UK where testing can be carried out. This is because muscle samples need to be taken to the MH laboratory in Leeds within 15 minutes of the muscle biopsy, in order for the tests to be reliable. It is currently not possible to have this test at other hospitals in the UK.

For information and a map of St James’s Hospital, please click here

What does MH testing involve?

There are two types of test to confirm MH. These are:

  1. Genetic screening (blood test)
  2. Muscle biopsy

Your GP, or consultant, will be able to advise you on the most appropriate type of screening for your particular case. However, the majority of people with suspected MH are referred for biopsy testing at the specialist unit in Leeds. Read more on testing for MH here.

It is really important that anyone who has a suspected MH undergoes genetic screening. This is because it could be a life-threatening condition for a patient’s relatives as well as themselves. The more we research and learn about existing MH patients, the more likely we will help future sufferers.

Can I have a biopsy test if I am pregnant?

No, testing for Malignant Hyperthermia is not available to pregnant women as the only method of excluding Malignant Hyperthermia risk is through in-vitro contracture testing of muscle strips excised at open biopsy. This procedure is not suitable for the pregnant woman because it places a risk to the pregnancy and also because of the potential for hormonal effects on the muscle interfering with the validity of the test itself.

Should I be worried about future anaesthetics if I have MH or am at risk of MH?

No. It is important to realise that operations can be performed safely and effectively for patients at risk of MH. All anaesthetists in the UK and most developed countries are aware of this condition. However, in order to anaesthetise you safely anaesthetic equipment needs to be specially prepared and a more experienced anaesthetist will often be called as some anaesthetists are less familiar with the alternative anaesthetics.

Although the condition may be documented in your notes, it is important for you to inform the anaesthetist of your MH status before any operation. We advise that you keep your MH warning card in your wallet or purse and wear a warning disc in case you are brought into hospital unconscious after an accident or through illness.

What do I do if I need an operation in the future but I have been tested negative for MH?

If you are negative, you can receive anaesthesia without any special precautions.

Can I work in an operating theatre if I have MH?

There is an international consensus that, providing standard  COSHH ( Control of substances hazardous to health) regulations are followed , MH susceptible individuals are not at risk of developing MH through occupational exposure in the operating theatre, post anaesthesia care unit or intensive care unit. We now recognise MH is a time weighted dose-dependent  phenomenon.  In other words in order for MH to be triggered the MH susceptible individual must be exposed to a certain quantity of anaesthetic. Triggering could therefore occur after a short period of exposure to a high concentration of triggering anaesthetic or a longer duration exposure to a lower concentration of anaesthetic. The dose required to trigger MH is considerably more than the exposure limits permitted by COSHH regulations. We also have the reassurance of knowing that theatre personnel with MH susceptibility have spent their whole careers without untoward events-many working in the days when scavenging or removal of the anaesthetic gases was not as good as it is currently.


It is theoretically possible that chronic exposure to relatively low anaesthetic concentrations could cause some instability of muscle membranes in an MH individual and this might be asymptomatic or produce muscle aches or cramps. This would likely be associated with a rise in the serum creatine kinase concentration.  It should be noted that some MH susceptible patients develop muscle aches and/or cramps associated with a rise in serum creatine kinase levels during the course of every day life.  Before an MH susceptible individual starts working in an operating theatre environment we advise that a series of baseline creatine kinase concentration measurements are made. This can be done by taking three such measurements over a one week period when the individual is undertaking similar activities in terms of physical exertion that they would otherwise be taking in the operating theatre environment. If there are subsequently any concerns about chronic exposure to anaesthetic gases, creatine kinase concentrations can be measured and compared to the baseline levels.

Can I travel abroad if I have MH?

Most developed countries have well trained anaesthetists and the necessary anaesthetic drugs and equipment required to manage patients at risk of MH. In less developed countries safe anaesthesia for patients at risk of MH cannot be guaranteed. Hospitals in these countries are also unlikely to be able to afford to stock Dantrolene, which is the antidote to MH that is used to treat an MH reaction.

The UKMHR can provide foreign translations and a list of foreign MH experts for use when travelling abroad. Please contact us by email: or Phone: 0113 20 65270

Can I still have a local anaesthetic at the dentist, or an epidural if I have MH?

Yes. All local anaesthetics are safe to use. However, it is still important to inform those treating you that you are at risk of MH.

I have been told I have malignant hyperpyrexia, is this the same condition?

Yes, malignant hyperpyrexia is an old name for malignant hyperthermia.

Sign up to the UKMH Registry

If you have been diagnosed with MH or have a relative who has been diagnosed with MH, please please read our patient information leaflet. You can sign up for the Registry by using this form.

Alternatively, please contact us on 0113 206 5270 (during working hours) and we will be pleased to advise you further.

Ways to help

We would be very pleased to hear from anyone affected by MH, who would like to help. Previous patients have helped in many ways including:

Fundraising to help our research
Joining our Patient Liaison Group
Reviewing patient information documents

If this is something you would be interested in please contact us here

Patient Helpline:

Tel: 0113 20 65270
(during office hours)

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