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Trouble at the Gates

Shayne Hinton after his malignant hyperthermia episode.

In a group of disorders known as periodic paralyses, ion channels that normally open when acetylcholine docks on membrane receptors don't function normally, and people experience temporary paralysis attacks in response to a variety of dietary, exercise, stress-related and other environmental changes.

After surgery, "many patients [with periodic paralysis] say, 'I woke up in the recovery room and I couldn't move; I didn't get my full strength back for four or five days,'" says Louis Ptacek, a neurologist at the University of Utah in Salt Lake City.

Ptacek emphasizes that the exact cause of the prolonged paralysis with anesthesia in some people with periodic paralysis isn't known and that it could be the stress of the surgery and/or any of the anesthetic drugs. One thing is critical for the medical team, he says: to distinguish between a periodic paralysis attack and an MH reaction. The treatments are completely different.

A recovered Shayne.

Certain other muscle conditions, such as myotonic muscular dystrophy (MMD) and myotonia congenita (MC), involve an inability to relax muscles at will (myotonia). The problem is usually traceable to faulty action of ion channels in the muscle cells (although the connection in myotonic dystrophy isn't entirely clear).

When certain drugs, particularly the muscle relaxant succinylcholine, are used, "these patients become rigid instead of relaxing," says Christopher Viscomi, an anesthesiologist at the University of Utah. That, he says, can complicate some procedures and make it harder than usual to put a patient on a ventilator.

If muscle relaxation during surgery is needed in people with periodic paralysis or myotonia, care must be taken with the choice of relaxing agent.

The anesthetic risks in myotonic dystrophy go far beyond inability to relax muscles with drugs. People with this disorder seem to have an especially high incidence of trouble with anesthesia in general for reasons that aren't well understood.

Fragile Muscles Break Down Under Stress

If the stress of surgery itself, awkward positions on the operating table and tourniquets that impair blood flow weren't enough for a person with fragile muscles to endure, there are also some threats to such muscles from anesthetic agents.

"A lot of people consider that patients with muscular dystrophy are susceptible to malignant hyperthermia," says Henry Rosenberg, an anesthesiologist at Thomas Jefferson University in Philadelphia. In his opinion, what they often have is something that looks like MH but really isn't.

Instead, he says, they have "some kind of muscle breakdown syndrome" that occurs with certain anesthetic drugs.

Early in the 1990s, Rosenberg says, "we began to be aware that when patients with Duchenne and Becker muscular dystrophies, and maybe some of the other muscular dystrophies, were exposed to succinylcholine and inhalational agents, their muscle membranes became leaky. "The way we knew this is that patients would develop very high potassium levels and have cardiac arrests. At first, we thought it was the succinylcholine. Most of [the patients] were children, and it was not clear that they had muscular dystrophy, because they were too young to have manifested symptoms."

Like Shayne Hinton, now 13, many of these patients were later found to have muscular dystrophy, Rosenberg says. A few years ago, the Food and Drug Administration required the manufacturers of succinylcholine to warn anesthesiologists not to use the drug on patients suspected of having a muscle disorder.

Unfortunately, says Rosenberg, eliminating succinylcholine from the anesthesia regimen didn't solve all the problems it was expected to.

"More recently, we found out that if people with muscular dystrophy receive any of the malignant hyperthermia-triggering agents, even without succinylcholine, they can also get into problems." The problems, in addition to life-threatening potassium levels, can include the release of large proteins, such as myoglobin, from the inside of the muscle cells, as the cells break down and membranes become massively leaky. These large proteins can damage the kidneys.

It isn't clear that dantrolene can help in this muscle breakdown syndrome, Rosenberg says. He suggests that it be treated by regulating potassium levels with solutions of glucose and insulin, and minimizing the damage from the myoglobin with lots of intravenous fluids.

But the best treatment, he says, is prevention - not giving MH-triggering agents to people with muscular dystrophy, actual or suspected - in the first place.

Good Anesthetic Alternatives

"There are excellent alternative anesthetics that can be given," says Jordan Miller, anesthesiologist and director of the Malignant Hyperthermia Program at the University of California at Los Angeles. Rosenbaum, who co-directs that program, says he and Miller always encourage people to be honest about their concerns because there are almost always solutions to an anesthesia problem.

Henry Rosenberg

Succinylcholine can be avoided by using other muscle relaxants, if such drugs are needed.

And, Rosenbaum says, "We're quite capable of doing without potent inhalational agents." He says the gas nitrous oxide and several intravenous agents can be safely used in the presence of a neuromuscular disease. Many people ask Miller and Rosenbaum about "local" anesthesia, the kind usually used for dental procedures or sewing up a wound, and "regional" anesthesia, the kind used to numb large areas of the body (for example, in labor and delivery).

The drugs used for local and regional numbing of an area affect signal transmission along nerves and are usually all right for people with neuromuscular conditions. However, Rosenbaum says, because nerves are affected by these drugs, "most practitioners are a little gun-shy about using them in patients with peripheral neuropathies." (Charcot-Marie-Tooth disease, Dejerine-Sottas disease and Friedreich's ataxia fall into this category.)

Miller says the real challenge is to make sure local or regional anesthetics are used properly and that a technique isn't being "pushed be-yond its normal use" just because either the patient or the doctors are afraid of using general anesthesia.

When that occurs, he says, the anesthetic is sometimes found to be inadequate for the procedure. The anesthesiologist may keep giving the patient more narcotics or other systemic drugs to compensate, which, he says, "can be a disaster.

"The issue is not so much that you can or can't use regional anesthesia, but you have to use it where it's appropriate, where the anesthesiologist and the surgeon think it would work well for that procedure," Miller says.

One place where regional anesthesia may be especially appropriate is in the woman with periodic paralysis who's having a baby, Viscomi says.

Viscomi says he and Ptacek treated a woman with this disorder during her pregnancy and childbirth, and epidural anesthesia (a regional anesthetic injected into the fluid around the spinal cord) was an excellent choice for her. Viscomi says it probably would be for most women in that situation.

"Strenuous muscle activity, both voluntary and involuntary, is associated with the onset of a periodic paralysis attack," Viscomi says.

He notes that epidural anesthesia reduces the work of labor by about 50 percent, thus reducing the risk of a periodic paralysis attack and avoiding the risks of general anesthesia at the same time. Epidurals can also often be used for Caesarean deliveries, Viscomi adds.

Communication, Preparation, Monitoring

Perhaps the great decrease in mortality rates associated with anesthesia has come about in recent years because of the marked increase in high-tech monitoring of patients during surgery. Today, sophisticated devices can continuously check a patient's temperature, exhaled carbon dioxide, blood oxygen concentration, blood potassium or sodium levels, electrical activity of muscles, and many other body functions.

The use of some of these devices is now routine, but some procedures depend on the surgical team's awareness and preparedness for specific problems - which is where patient responsibility comes into play.

When surgical teams have been thoroughly briefed about a patient's condition, they can take many precautions that otherwise might not have occurred to them - such as changing the patient's position on the table or minimizing shivering after surgery.

Unfortunately, it may fall to the patient and family to ensure that such briefing takes place. "I would recommend to the patient or the patient's family, if a child is involved, that they schedule a meeting with the anesthesiologist well ahead of time," Rosenbaum says.

"The anesthesiologist should look over a recently updated summary from the patient's primary care physician, such as the pediatrician or internist, as well as the patient's neurologist, to have a very good understanding of the patient's condition," he says. "This should cover not only how it affects the neuromuscular system, but what other organ systems are affected, how it affects day-to-day functioning, and how it might impact the patient during surgery and in the early postoperative period.

"I think serious problems are relatively uncommon if one is educated about patients and can anticipate problems and minimize the likelihood of their occurrence."

Miller agrees. "I think the biggest problem is that patients frequently depend on surgeons to adequately convey information to the anesthesiologist, but that should not be depended on," he says.

"The patient should have direct communication, preferably with the anesthesiologist who's going to be taking care of them, but, if not, then with some member of the anesthesiology department, so that the whole anesthesia can be planned."

Just knowing the patient's neuromuscular disease diagnosis isn't nearly enough, Miller says. "Where the patient is in the course of the disease is extremely important."

Even a written summary isn't sufficient to do the job in his opinion. A face-to-face meeting or at least a telephone conversation should happen, he says, and the patient should insist on it.

Rosenbaum admits that in a large and complex medical system it can be difficult to play this liaison function, but it's crucial that patients follow through.

"Once the patient gets the doctors in touch with each other, they should be able to continue the process," he says.

The anesthesiologist should know everything possible about you, Miller says. Your medications, herbal remedies, history and diagnosis are all important.

The goal, Miller says, "is not to panic people but to point out that it's like wearing a seatbelt in a car. If you don't wear a seatbelt, it doesn't mean you're definitely going to die, even if you're in an accident. But you want to take the precautions that you can."