SATURDAY, Nov. 13, 2010 (HealthDay News) -- For people stricken with sudden cardiac arrest, doctors often resort to a brain-protecting "cooling" of the body, a procedure called therapeutic hypothermia.
But new research suggests that physicians are often too quick to terminate potentially lifesaving supportive care when these patients' brains fail to "re-awaken" after a standard waiting period of three days. The research suggests that these patients may need care for up to a week before they regain neurological alertness.
"Most patients receiving standard care -- without hypothermia -- will be [neurologically] awake by day 3 if they are waking up," explained the lead author of one study, Dr. Shaker M. Eid, an assistant professor of medicine at Johns Hopkins University School of Medicine.
However, in his team's study, "patients treated with hypothermia took five to seven days to wake up," he said.
The results of Eid's study and two others on therapeutic hypothermia were scheduled to be presented Saturday during the meeting of the American Heart Association in Chicago.
For over 25 years, the prognosis for recovery from cardiac arrest and the decision to withdraw care has been based on a neurological exam conducted 72 hours after initial treatment with hypothermia, Eid pointed out. The new findings may cast doubt on the wisdom of that approach, he said.
For the Johns Hopkins report, Eid and colleagues studied 47 patients who survived cardiac arrest -- a sudden loss of heart function, often tied to underlying heart disease. Fifteen patients were treated with hypothermia and seven of those patients survived to hospital discharge. Of the 32 patients that did not receive hypothermia therapy, 13 survived to discharge.
Within three days, 38.5 percent of patients receiving conventional care were alert again, with only mild mental deficits. However, at three days none of the hypothermia-treated patients were alert and conscious.
But things were different at the seven-day mark: At that point, 33 percent of hypothermia-treated patients were alert and had only mild deficits. And by the time of their hospital discharge, 83 percent of the hypothermia-treated patients were alert and had only mild deficits, the researchers found.
"Our data are preliminary, provocative but not robust enough to prompt change in clinical practice," Eid stated.
In the second study, a team led by Dr. Kyle McCarty, an emergency medicine resident at Maricopa Medical Center in Phoenix, found that withdrawing hypothermia before three days was common even though it was counter to existing protocols.
"Thus far we have found that despite the fact that current guidelines state that the neurological prognosis after cardiac arrest cannot be reliably assessed within 72 hours of the completion of therapeutic hypothermia, the timing of withdrawal of care after hypothermia is highly variable," McCarty said. In fact, "early withdrawal of care is common even in a system with specific protocols aimed at preventing early withdrawal," he added.
Of the 177 patients studied, hypothermia care was withdrawn from one-third of patients within 24 hours and close to one-third (30 percent) of patients within 25 to 72 hours. Only about one-quarter of the patients studied received therapeutic hypothermia for the recommended minimum of 72 hours, McCarty's team found.
"This study implies that even in a system with specific protocols set up to prevent early withdrawal of care in patients who have undergone therapeutic hypothermia, there is significant variability in the timing of care withdrawal, frequently prior to the recommended 72 hours," McCarty said.
And in the final study, Dr. Keith Lurie, a professor of medicine at the University of Minnesota in Minneapolis, and colleagues found that withdrawing life support 72 hours after re-warming "may prematurely terminate life in at least 10 percent of all potentially neurologically intact survivors" of cardiac arrest treated with hypothermia.
For the study, Lurie's team looked at the time from when patients had been fully "re-warmed" to when they showed signs of awakening -- including being alert and oriented.
Among the 66 patients studied, six who showed signs of brain re-awakening beyond the traditional 72-hour cut-off regained good neurological function within a month of the cardiac arrest.
However, comatose patients were usually treated after hypothermia for at least two days before any decision to withdraw care was made, the researchers noted.
Commenting on the studies, Dr. Gregg Fonarow, American Heart Association spokesman and professor of cardiology at the University of California, Los Angeles, said that "therapeutic hypothermia for unconscious cardiac-arrest survivors has been demonstrated to improve neurologic outcomes and patient survival. As a result, this approach is being increasingly applied to individuals with out-of-hospital cardiac arrest."
These three new studies each suggest that significant neurologic recovery may occur beyond 72 hours of re-warming, however, he said. But, in some cases, premature withdrawal of life support within 72 hours after re-warming is still occurring, according to Fonarow.
Furthermore, "recent [American Heart Association] guidelines state that neurologic prognosis after out-of-hospital cardiac arrest cannot be reliably assessed within 72 hours of the completion of therapeutic hypothermia," he said.
"Centers providing therapeutic hypothermia for patients with out-of-hospital cardiac arrest need to pay close attention to these important new findings and ensure protocols consistent with current American Heart Association guidelines are being implemented and followed," Fonarow stressed.
Experts point out that research presented at meetings is not subjected to the same type of scrutiny given to research published in peer-reviewed journals.
For more information on cardiac arrest, visit the American Heart Association.