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Posted on Tue, Oct 16, 2012 : 5 a.m.

Severe reaction to general anesthesia is rare

By Ask Dr. K


I'm scheduled to have surgery soon, and I have never been under general anesthesia. How can I be sure I won't have a severe reaction to the anesthesia?


Severe reactions to anesthesia, fortunately, are extremely rare. You may be concerned, in particular, with a severe, sometimes fatal, reaction to anesthetics called malignant hyperthermia. It usually occurs during or after surgery, but it can occur whenever anesthetic drugs are used. This includes emergency rooms, dental offices and intensive care units.

Malignant hyperthermia is caused by a rare muscle abnormality. In this inherited condition, muscle cells have an abnormal protein on their surfaces. The protein does not greatly affect muscle function. As a result, many people are unaware of this abnormality.

However, when certain general anesthetic drugs interact with the abnormal protein on the muscle cells, they cause the muscles to contract forcefully and to keep contracting. This sustained muscle contraction generates a lot of heat.

As a result, the following symptoms develop:

-- a dramatic rise in body temperature

-- rigid or painful muscles

-- flushed skin

-- sweating

-- rapid or irregular heartbeat

-- rapid or uncomfortable breathing

-- brown- or cola-colored urine (from a brown-colored protein in damaged muscle cells)

-- very low blood pressure (shock)

-- confusion

Symptoms usually occur within the first hour after exposure to the trigger medication. As soon as malignant hyperthermia is suspected, doctors must act quickly. They should immediately stop giving the trigger medication and stop the surgery. Doctors then give the drug dantrolene (Dantrium). Dantrolene relaxes the muscles and stops the dangerous increase in muscle metabolism.

With prompt treatment, symptoms should resolve within 24 hours. However, if a severe reaction develops before treatment begins, complications may develop. These can include respiratory or kidney failure.

How can you protect yourself against having malignant hyperthermia if you are scheduled for general anesthesia? It is not practical to test for this condition in everyone who is scheduled for surgery. The abnormal protein can be caused by a number of different genetic defects, and not every person with the abnormal protein has a bad reaction with general anesthesia. However, you should be tested before surgery if you have:

-- a family history of malignant hyperthermia

-- a history of heat stroke or hyperthermia after exercise

-- muscle abnormalities that may be associated with malignant hyperthermia (including muscular dystrophy)

If you have been diagnosed with the disorder, you can prevent future episodes. Notify your doctor before you undergo any surgery or office-based procedure. You don't have to avoid surgery altogether; your doctor or dentist can use one of the many safe alternative anesthetics that are available.

One such safe alternative is propofol. You may recognize the name of that drug, because it was an overdose of it that led to the death of Michael Jackson. Overdoses definitely can be fatal, but proper doses are perfectly safe and effective.

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)

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