Beta-blockade guards burn victims’ muscle
By Ben Harder
A medication that reduces the risk of heart attack also can diminish a muscle-wasting metabolic response common among victims of severe trauma or illness, researchers have discovered by studying young burn patients.
In the aftermath of injuries or burns or during serious illnesses, victims typically exhibit higher metabolism, rapid protein breakdown, and difficulty making new muscle tissue. Even with plenty of nutrition, severely injured or ill patients can suffer metabolic breakdown of muscle mass, or muscle catabolism. During prolonged recoveries, patients can catabolize up to one-tenth of their muscle mass despite putting on weight.
Drugs known as beta-blockers are widely used to regulate heart rate and blood pressure in patients with heart conditions. The drugs inhibit the function of hormones such as epinephrine and other so-called catecholamines, already known to play a major role in post-traumatic hypermetabolism.
Because these drugs lower metabolism, researchers at the University of Texas Medical Branch in Galveston suspected that beta-blockers might help burn patients avoid muscle loss. To find out, the team studied 25 children under the age of 16 who were treated at the Shriners Hospitals for Children, also in Galveston, for severe burns covering at least 40 percent of their bodies.
The researchers administered propranolol, a generic beta-blocker, to 13 patients beginning on the fifth day after each subject’s first surgical treatment for burns. They adjusted the drug’s dose to depress resting heart rates by 20 percent below the patients’ premedication pulse. The rest of the patients in the group received standard care that did not include beta-blockers.
After 2 weeks, the resting metabolic rate had risen for those in the control group, and these patients were breaking down more protein than they were making. But the metabolic rate had fallen for those in the group receiving beta-blockers, and they were producing more protein than they were catabolizing.
While the patients not receiving beta-blockers lost, on average, 9 percent of their muscle mass in the 2 weeks, those in the propranolol group lost approximately 1 percent of their muscle mass, the researchers report in the Oct. 25 New England Journal of Medicine.
The study demonstrates that when patients receive beta-blockers, “muscle mass can be preserved through a long, stressful hospitalization,” says David N. Herndon, a surgeon specializing in burn injuries and the paper’s lead author. He plans to test whether victims of other traumas or infections can benefit from beta-blockade, too.
The Galveston researchers “used elegant techniques [to examine] a specific, uniform population,” remarks Robert L. Sheridan of Shiners Burns Hospital in Boston. In a commentary accompanying the study report, he cautions that beta-blockers must be tested in other groups before being used widely to stem postinjury muscle wasting.
Because beta-blockers slow the pulse rate and constrict airways, they might cause complications in people with heart and lung problems. These could include burn patients who had inhaled a lot of smoke, Sheridan says.
