Post-Cardiac Arrest Care on Memphis Medical News

Post-Cardiac Arrest Care

By: SHARON H. FITZGERALD

Therapeutic Hypothermia is One of Several Protocols Recommended in AHA Advisory

Once healthcare providers restart the heart of a cardiac-arrest patient, the job has only begun. That's according to a science advisory on post-cardiac arrest care published last October in Circulation, a journal of the American Heart Association (AHA).

"Much of the focus of resuscitation since the '60s has been doing everything we can to get the heart restarted as soon as possible. It turns out, if you look at the epidemiology, you still have only a 30 percent chance of leaving the hospital alive," said Robert W. Neumar, MD, PhD, who headed the committee that wrote the AHA advisory. Yet, Neumar added, research now shows that post-cardiac arrest care is the key to survival.

Associate director of the Center for Resuscitation Science at the University of Pennsylvania in Philadelphia, Neumar said a combination of injuries is brought on by the state of cardiac arrest and resuscitation. "When someone's had a cardiac arrest, they have had no blood flow to their body for a period of time. When they get their circulation restarted, it's a very unnatural state. The body's adaptation to that can be both beneficial and detrimental," he explained. The result is what's being called post-cardiac arrest syndrome, which is a combination of four components: brain injury, heart dysfunction, systemic inflammation and the underlying problem that caused the heart attack in the first place.

The American Heart Association's

Top Things to Know About
Post-Cardiac Arrest Syndrome*

Approximately 166,200 out-of-hospital cardiac arrests occur annually in the US.
On average, approximately 6.4 percent of out-of-hospital cardiac arrest victims survive to hospital discharge.
The in-hospital mortality rate of patients who achieve return of spontaneous circulation after cardiac arrest has not changed significantly over the past half-century.
There is growing evidence that appropriate post-cardiac arrest care, such as tight blood-glucose control and therapeutic hypothermia, can improve mortality rate and functional outcome.
Post-cardiac arrest brain injury is a common cause of morbidity and mortality.
Post-cardiac arrest syndrome is characterized by resumption of spontaneous circulation after prolonged complete whole body ischemia.
Hyperglycemia is common in post-cardiac arrest patients and is associated with poor neurological outcome.
Post-cardiac arrest myocardial dysfunction can contribute to low survival rates after in- and out-of-hospital cardiac arrest but is both responsive to therapy and reversible.
It is appropriate to consider immediate coronary angiography in all post-cardiac arrest patients in whom ACS is suspected. Cardiac arrest patients with STEMI ECG criteria should undergo immediate coronary angiography and subsequent PCI if indicated; thrombolytic therapy can be an appropriate alternative if PCI is not available.
Both pre-clinical and clinical evidence strongly support mild therapeutic hypothermia as an effective therapy for the post-cardiac arrest syndrome.

* Based on the AHA science advisory, Post-Cardiac Arrest Syndrome: Epidemiology, Pathophysiology, Treatment and Prognostication

When it comes to the brain, global ischemia is "a unique form of injury," Neumar said. "It's different from a stroke, where a single blood vessel is occluded for a long period of time. In cardiac arrest, the blood flow to the entire brain is stopped, but it's a shorter period of time." Also suffering is the cardiovascular system, which experiences a problem similar to sepsis after the stagnant blood begins to recirculate. "It triggers a systemic inflammatory response and coagulation cascade that causes abnormal signaling and inflammation in the body," Neumar said. "If it gets out of control, it can lead to multi-organ failure."

The AHA advisory covers several treatments for different types of cardiac-arrest patients (see accompanying list from the AHA), including immediate coronary angiography to check for artery blockages in patients resuscitated from a cardiac arrest caused by a heart attack (as evidenced by an electrocardiogram). An angioplasty or administration of a clot-busting drug may follow to re-establish blood flow to the heart.

The advisory also recommends therapeutic hypothermia (lowering the patient's core body temperature to 89.6 to 93.2 degrees Fahrenheit) for unconscious adult patients resuscitated after an out-of-hospital cardiac arrest. "There's a tremendous amount of animal data supporting the fact that therapeutic hypothermia definitely protects the brain and reduces brain damage and saves neurons from dying," Neumar said. Clinical trials, conducted in Australia and Europe and published in 2002, showed improved outcomes, he added.

Thus, more hospitals, particularly academic medical centers, are adopting hypothermia protocols. One is Vanderbilt University Medical Center in Nashville, which devised its own protocol in early 2007. So far, about 40 patients have received the treatment. "There's no way to know for sure, but I'm pretty optimistic that we've had some good outcomes because of this protocol," said John A. McPherson, MD, medical director of Vanderbilt's Cardiovascular Intensive Care Unit.

Vanderbilt uses external cooling blankets, including a head wrap, with ice-cold water circulating through them to create heat exchange. "One misconception is that it's simple. It's not a simple process. It's not as simple as just cooling somebody's core body temperature down," McPherson said. The patient is on a ventilator, heavily sedated and then paralyzed using a drug to prevent the body's shivering response. Doctors watch for warning signs of trouble such as an electrolyte imbalance, abnormal blood clotting, blood glucose shifts, and blood pressure and heart rhythm changes. "Somebody trained in intensive-care medicine has to be at the bedside when you do this," McPherson cautioned.

He said Vanderbilt's next step will be to initiate cooling procedures in the emergency room and perhaps eventually even by emergency responders in the field.