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Anaesthetics and muscular dystrophy

Sometimes you may need to have a local or general anaesthetic for a medical procedure. If you have a muscle wasting or weakening condition or a family history of a muscle wasting or weakening condition, it’s essential to let your anaesthetist know in advance so they can carry out appropriate tests and take necessary precautions.

This includes the anaesthetist understanding your medical condition and history, carrying out an assessment before the operation and providing monitoring after your operation.

How anaesthetics affects muscles

Many of the agents used in anaesthetics, such as gases and chemicals, affect both muscle and nervous tissue. For people with muscle wasting and weakening conditions, these can have a greater effect on the body. The main areas of concern are how the anaesthetic will affect the muscles in the body and how they will affect the heart. A curvature in the spine (scoliosis) can also affect the way someone responds to anaesthesia.

Anaesthetics and the heart

People with muscle wasting and weakening conditions can sometimes have issues associated with the heart. This can occur as a cardiomyopathy or a conduction disorder.

A cardiomyopathy is when the heart muscle doesn’t work effectively because the walls of the heart chambers have become thickened, stiff, or stretched. This affects the heart’s ability to pump blood.

A conduction disorder is also known as a heart block. This is when there is a problem with the electrical system that controls the rhythm and rate of the heart.

The anaesthetic vapours, such as ether and halothane, are inhaled and this can reduce the effectiveness of the heart’s muscle contractions. It can also aggravate any conduction disorder. The vapours are different from each other, with some having more effect on the heart than others.

The anaesthetist will assess your condition and how it impacts your heart before the operation. This could include assessing the level of physical activity that you can manage and an Electrocardiogram (ECG). Occasionally, a more extensive assessment is needed.

Anaesthetics and breathing

Any anaesthetic agent that affects the muscles will also affect the muscles that are used to breathe. To measure how weak the muscles are, a blood sample will be taken to measure levels of a muscle enzyme called creatine kinase (CK). An assessment will also be carried out to determine how much physical activity can be performed.

Strong analgesic or sedative medication will affect these muscles indirectly, and muscle relaxants will have a direct effect on them. As breathing may already be difficult for patients with neuromuscular conditions, these drugs should be used cautiously.

After the operation, monitoring of breathing is essential as the muscles used for swallowing may be affected. This may be why some people will need careful monitoring in a High Dependency Unit or Intensive Care Unit.

Muscle relaxants in anaesthesia

Muscle relaxant drugs should only be used if essential. This is because they can have more of an impact on people living with muscle wasting and weakening conditions compared to other people.

Suxamethonium is a muscle relaxant that should be avoided if you have a muscle wasting or weakening condition. It causes the release of potassium ions from the muscle tissue into the blood and may cause abnormal heart rhythms. It’s important to have a blood test to check potassium levels before an operation or procedure.

Local anaesthetics

Local anaesthetics are used for minor procedures, such as stitches for cuts. They stop nerves from sending signals, numbing the area. They usually have little side effects. For bigger procedures, like spinal or epidural anaesthesia, it’s important to carefully assess someone’s condition before an operation or procedure. They have few side effects. For major local anaesthetic techniques, such as spinal or epidural, careful assessment of the patient and their condition is required before the operation.

Changes in body temperature and preoperative fasting

People with muscle wasting and weakening conditions do not tolerate changes in body temperature or fasting before surgery, as well as patients without a muscle wasting condition. These issues can be minimised by keeping the patient warm and well-hydrated, using drips.

Malignant hyperthermia and muscle wasting conditions

Malignant hyperthermia (MH) is a serious and potentially life-threatening condition that can be triggered by specific general anaesthetics and muscle relaxants commonly used during surgery. People with a muscle wasting condition may have a heightened risk of MH susceptibility. Symptoms of MH include a dangerously high body temperature, muscle rigidity, and a rapid heart rate. Prompt recognition of MH is crucial and can be treated with a drug called dantrolene and measures to lower body temperature.

MH susceptibility is often linked to mutations in the RYR1 and CACNA1S genes. Conditions caused by a RYR1 mutation include central core disease and multiminicore myopathy. Patients can undergo a muscle biopsy to screen for MH susceptibility. Careful preoperative assessment and consideration of alternative anaesthetics is crucial for patients with known or suspected MH susceptibility.

Important precautions for local or general anaesthetic

For people with muscle wasting or weakening conditions, it’s important to take the following precautions when undergoing anaesthesia.

  • Your anaesthetist must make a careful and thorough assessment of your general health, your condition, and how it affects your body
  • Doctors should carry out an assessment before an operation or procedure. In most cases, people with muscle wasting or weakening conditions will not usually be treated as an outpatient. This may mean staying in hospital to allow enough time for recovery and after-care.
  • Inform the anaesthetist of your condition, even if you have only minor symptoms or no symptoms at all. The anaesthetist should be told if there is a muscle wasting or weakening condition in the family, even if someone has no symptoms present. Sometimes, a person may find out they have a condition due to an unexpected complication caused by an anaesthetic. This can be the case particularly with young children.
  • Ask that the anaesthetist and healthcare professionals looking after you are told about your muscle wasting or weakening condition before any hospital admission. In some cases, they might be able to speak with your specialist neuromuscular team to find out more information about your condition and any associated risk with anaesthetics.
  • It might be helpful to consider carrying a condition specific alert card or wearing a medical alert bracelet. This information will help the anaesthetics and healthcare professionals to better understand your condition.

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