Slowing Down Brain Is Still Fraught With Risk
Monday, March 13, 2006
When a doctor utters the word "coma," the prognosis is usually bleak. Yet every day, physicians intentionally put patients into comas.
Despite great advances in modern medicine, there are still few options for treating severe brain injuries such as those caused by a blow to the head, a stroke or constant seizures. Physicians can try draining fluid or raising the head of the patient's bed to alleviate potentially fatal swelling. But if those efforts fail, they sometimes decide to push patients to the precipice, as close to brain death as humanly possible.
The procedure, called medically induced coma, slows brain activity almost to a stop by pumping huge doses of barbiturates into the patient. The goal is to give the injured brain a rest in the hope it will heal itself.
"It's a leap of faith," said Julian Bailes, neurosurgery chairman at West Virginia University School of Medicine. "It's a last-ditch measure when we feel we're at the end of the game. Although it has been very effective for some patients."
Though drug-induced comas have been in use for three decades, the procedure has made headlines in recent months with famous patients such as Israeli Prime Minister Ariel Sharon and the sole survivor of the Sago Mine explosion in West Virginia.
The brain is an energy glutton, controlling all body activity from basic reflexes to deep intellectual thoughts. It rouses sleepy muscles in the morning, controls breathing and heart rates, inspires creative flights of fancy and sparks emotional outbursts. Even when the rest of the body is sleeping, the busy brain is working, generating dreams.
Fueled by oxygen and glucose, the brain operates like a faucet, opening capillaries when it needs to draw in more nutrient-packed blood to keep working. In some situations, such as when a patient has a blood clot, the delivery pipe from heart to brain becomes blocked, causing one type of stroke. In many injuries, the brain is bruised and too much blood pours in. To deal with a trauma, or "insult," the brain works harder, sucking in more nutrients and swelling up to accept them. But because it is encased in the skull, there is little room for it to expand.
"It literally suffocates inside the armor," said Lee Schwamm, associate director of the stroke center at Massachusetts General Hospital. If the "intracranial" pressure is not relieved, the patient will probably die in a matter of days.
To measure the pressure, doctors insert a small fiber-optic tube into the patient's head. The wire acts like an air gauge, monitoring the balance of blood flow. One way to reduce the pressure is essentially to "turn off the brain" so it does not need as much fuel, said Marc Mayberg, executive director of the Seattle Neuroscience Institute. The drug-induced coma, which Mayberg compared to a motor slowed to idle, "enables the brain to recover while it's under this state of reduced metabolism."
Some medical experts, however, say drug-induced coma is an experimental treatment with little data behind it.
"We're clear about what is therapy and we're clear about what counts as research, but experimentation falls in between the two," said Ronald Carson, an ethicist at the University of Texas Medical Branch at Galveston. "There are risks involved in doing something, as well as risks involved in doing nothing. We don't know what the person is going to be like at the other end."
Comas come in varying degrees, often measured on a scale created by a pair of professors at the University of Glasgow in Scotland in 1974. Patients are assigned a numerical score based on how well they respond to verbal commands and external stimuli such as pinching: the lower the score, the deeper the coma. A patient put into a medically induced coma rates a 3, the lowest score on the scale.