Published in the September 2013 issue of Today’s Hospitalist
A NEW STUDY confirms what many have suspected: Very few patients who suffer in-hospital cardiac arrest get a chance to benefit from therapeutic hypothermia.
The study found that only about 2% of potentially eligible hospitalized patients in the Get with the Guidelines Resuscitation database from the American Heart Association (AHA) between 2003 and 2009 received the therapy. That’s despite the fact that therapeutic hypothermia has been found to improve both mortality rates and neurologic function among patients surviving heart attacks that occur outside the hospital.
“We had hypothesized that use would be low, but we found that use was significantly lower than we had hypothesized,” explains Mark E. Mikkelsen, MD, a critical care physician, epidemiologist and assistant professor of medicine at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, and lead author of the study published in the June 2013 issue of Critical Care Medicine. The research looked at more than 67,000 patients whose circulation returned after in-hospital cardiac arrest in 538 hospitals. More than 200,000 people experience cardiac arrest in U.S. hospitals each year, and less than 20% survive to discharge.
Although there is little evidence about its effectiveness following in-hospital arrests, therapeutic hypothermia (cooling patients to between 32 and 34 degrees C) should be “considered,” according to the AHA’s 2010 guidelines. (By contrast, two studies published in 2002 addressed the therapy’s benefit for out-of-hospital cardiac arrests. For those patients, the AHA “recommends” its use.)
Dr. Mikkelsen nonetheless thinks the “conservative” choice is to initiate the therapy significantly more often than is done now.
“I’d err on the side of trying to improve patients’ lives, not just immediately but in the long term,” he says. Currently, data suggest the therapy may be of benefit, while no data indicate that it could be harmful.
“The epidemiologist in me says, ‘Wait for the data,’ ” Dr. Mikkelsen explains, “but the practicing physician in me says that if family or friends experienced an in-hospital cardiac arrest, I would use therapeutic hypothermia.”
The study showed that therapeutic hypothermia following in-hospital cardiac arrest is “vastly underused.” Given his experience at the University of Pennsylvania, where the therapy has been used regularly for “five to 10 years,” Dr. Mikkelsen says he “would have expected it to be used five to 10 times more often.”
The study points out that many hospitals have tried therapeutic hypothermia. In more than 80% of the hospitals that reported data yearly to the AHA database, the therapy was initiated in at least one patient.
Also, its use has increased over time, just not very dramatically. The rate of therapeutic hypothermia initiation in patients with in-hospital arrests increased from 0.7% in 2003 to 3.3% in 2009. Therapeutic hypothermia was much more likely to occur in academic centers and when patients were younger, or when the arrest happened on weekdays (vs. weekends) or on units outside the ICU.
Although the study didn’t look into the reasons why the therapy is used so rarely, Dr. Mikkelsen sees some hints in its findings. Some point to patient characteristics, while others reflect hospital issues. “It could be that hospitals’ initial experiences did not go well or that a local champion moved away,” Dr. Mikkelsen says.
As for patient characteristics, questions remain as to which patients are good candidates. That’s particularly true because hospitalized patients are “already severely ill” and may respond differently to therapeutic hypothermia than patients suffering cardiac arrests in the community.
Reaching target temperature
On this unanswered point, Dr. Mikkelsen notes the study’s findings that the “target temperature” was often not achieved during the rare attempts made. About 44% of patients were undercooled, while nearly 18% were overcooled. That may indicate how tough it can be to cool patients to target temperatures when they are already ill, perhaps febrile, or have other comorbidities that affect thermoregulation.
“That’s a question that requires further examination,” he notes. In addition, recent studies showing that overcooling can be harmful may be slowing the therapy’s adoption.
Subsequent research now underway by Dr. Mikkelsen and his colleagues explores which factors are associated with the inability to achieve target temperature.
“We want to try to educate others about what factors are specific to the patient or to the implementation method,” he says. Moreover, researchers don’t know yet if institutions initiating the therapy more frequently are better at achieving target temperatures than less experienced ones.
“Is it a knowledge issue or a patient-specific issue?” Dr. Mikkelsen asks. “We don’t know.”
Planning and coordination
Other researchers are focusing on outcomes. They are asking if therapeutic hypothermia has the potential to give patients who arrest in the hospital the best chance of neurologic recovery, as it seems to for those arresting in the community.
“Most folks who are experts in the field ask the basic question: Does the brain have any idea of whether the cardiac arrest occurred in or outside the hospital? And the general thought is that it doesn’t,” says Dr. Mikkelsen.
As this study shows, however, the medical community seems to be sending a clear message that “we need more data” before it spends the time and energy needed to initiate the therapy more often.
“A trial is urgently needed to determine if this theoretically beneficial therapy is actually beneficial,” he points out.
To promote more frequent use, Dr. Mikkelsen says the therapy requires a champion. “It also requires coordination between physicians and nurses. The bedside nurse is critical to effective implementation and to ensure that it is delivered safely.”
And because hospitals have many options for cooling patients, facilities need to decide which technique to use. They then have to purchase the right equipment and have it readily available, with staff trained to use it and a protocol to follow.
“It requires planning well before an inciting event,” says Dr. Mikkelsen. “If there is nothing in place prior to an event, it is highly unlikely that a patient will receive the therapy.” The biggest barrier, he adds, “is simply getting the right stakeholders together well in advance so individuals who will encounter cardiac arrest in the hospital can provide the therapy to the next patient.”
Therapeutic hypothermia remains one of the only weapons clinicians have to “potentially improve survival and the lives of those who actually survive this quintessential critical illness event,” Dr. Mikkelsen says.
“It fits within the general concept of what I call post-intensive care syndrome, which is the concept of new or worsening cognitive or physical function after illness,” he says. “Our responsibility is to recognize that the lives of patients after critical illness are often quite different than they were before, and we need to do what we can to improve the lives of survivors.”
Deborah Gesensway is a freelance writer who covers U.S. health care from Toronto.