Anesthesia in Children with Muscular Dystrophy

Important Information for Your Son’s Doctor

By Dr. Margaret Vroom Anesthesia-

When a patient with Muscular Dystrophy is subjected to general anesthesia, a number of serious problems may arise. As a parent, it might be useful to be informed about these possible anesthesia-related risks and how these risks can by minimized by careful selection of the administered anesthetic agents. Therefore, a brief overview of the literature and some of the current ideas and concepts will be discussed.

Anesthesia -related complications in children with muscular dystrophy can be subdivided into generate and specific categories.

General

Muscular dystrophy not only affects the muscles of the extremities, but as the disease progresses, heart and respiratory muscles become involved as well.

Almost all anesthetics decrease contractility of the heart. Many children with muscular dystrophy have an impaired cardiac function

(Cardiomyopathy)

As a result, difficulties may arise with the circulation in the preoperative period.

Prolonged spontaneous respiration during general anesthesia may result in inadequate ventilation of the lungs with increased carbon dioxide levels in the blood. This in turn can cause severe heart rhythm disturbances, especially in those patients with an already impaired cardiac function and even more so in combination with certain (volatile) anesthetics. During the majority of general anesthetic procedures, however the respiratory function is controlled by a mechanical respirator via insertion of a tube in the upper airways, which will be discussed below.

Following general anesthesia, problem may arise when the patient has to regain his respiratory function. The respiratory drive is diminished as a result of residual drugs effects, coughing is impaired and aspiration easily occurs. All of this may result in low levels of oxygen and high levels of carbon dioxide in blood. Furthermore, certain areas of the lung may collapse (telecasts) impairing oxygenation of the blood and increasing the risk of respiratory infections.

Therefore, it is important (and for large operations even mandatory)To perform extensive preoperative screening, not only to estimate the preoperative risks, but to provide optimal preoperative monitoring. The screening may included a cardiac ultrasound, an electrocardiogram, pulmonary functions tests as well as blood gases.

Specific

The membranes of muscle fibers and/or the receptors on the muscle cells can alter as a result of the disease, both in function as well as in number, modulate the function of the cell.

In patients who have been bedridden of a long period or who are unable to actively use their muscles, the administration of the depolarizing muscle relaxant succinylcholine may result in the release of large amounts of the ion potassium from the muscle cell into the blood stream, since depolarizing muscle relaxants cause the muscles to contract briefly before they relax. This sudden heart in potassium concentration in the blood may result in life-threatening heart rhythm disturbances. The non-polarizing muscle relaxants (for instance europium, atracurium or mivacuronium) do not initiate muscle contraction and, therefore their use does not carry this risk. Nonetheless, the affected muscles may have become more sensitive to non-depolarizing muscle relaxants and therefore the dose administered has to be carefully chosen.

The brief but profound muscle contraction associated with the use of succinylcholine leads to elevated levels of creatinine kinase (CK) and myoglobin which can be detected in the blood afterwards. The use of succinylcholinee and muscle breakdown called rhabdomyolysis. Muscle break down leads to the release of high concentrations of potassium, CK and myoglobin in the circulation. As mentioned previously high concentrations of muscle-proteins of potassium in the blood may result in cardiac arrest and the high concentrations of muscles proteins may severely impair the kidney function.

In addition the use of succinylcholine and inhalational anesthetics may results in a syndrome called malignant hyperthermia. Malignant hyperthermia is a life threatening disturbance of a calcium homeeostasis in muscle cell provoked by certain anesthics. Succinylcholine and inhalational anesthetics are particularly renowned for causing this syndrome malignant hyperthermia occurs relatively frequent in patients with muscular dystrophy. Malignant hyperthermia is characterized by an extremely elevated metabolism within the muscle cell. As a result the temperature of the entire body rises to life threatening levels, oxygen consumption and carbon dioxide production of the body increases dramatically and waste products are released into the circulation. It is of extreme importance that this syndrome is readily recognized so that the appropriate measures can be taken. Including drastic cooling of the body and prompt initiation of therapy with the drug dantroleen. Unfortunately despite appropriate measures, the course of this syndrome is often fatal. Children with MD should always be considered of being at high risk for the development of malignant hyperthermia and, therefore, the high risk anesthetics should be avoided.

Conclusions

General anesthesia is accompanied by a number of important risks.

When general anesthesia is required in order to undergo a specific procedure succinylcholine and inhalational anesthetic needs to be avoided

Painkillers (opioids) the anesthetic propofol midazolam and hypnomidate can probably all be used safely. When it is essential to use muscle relaxants, short acting, non-depolarizing muscle relaxants can be used albeit at a reduced dose (1/4 - 1/5 of the usual does) controversy exists as to whether antagonizing these muscle relaxants with cholinesterase inhibitors carry additional risks. Therefore, it is of utmost importance to inform your anesthetist as early as possible about the medical history of your child. The necessary pre-operative screening procedures (heart and lungs) can be performed and also the appropropiate anesthetics can be selected. In addition, the anesthetics will be enabled to provide optimal peri-operative monitoring. You may want to show this document to the anesthetist involved in caring for your child during any surgical or emergency procedure.

Ok not sure where this info came. I found it with a bunch of pages. I had on DMD

I do not claim to write this has my info.