Cool Way to Treat Cardiac Arrest
MADISON - The University of Wisconsin Hospital and Clinics Level One Heart Attack Program is using a new technique to treat cardiac arrest patients that involves cooling a patient's body to 34 degrees following cardiac arrest, lowering the risk of death and reducing damage to both the brain and heart.
Patients who suffer out-of-hospital cardiac arrest can often suffer severe anoxic brain injury due to stoppage of blood flow carrying oxygen to the brain. Thus, it is common for heart attack patients to survive the resulting cardiac arrest, but die from brain injury.
The mild hypothermia technique has been shown to enhance a patient's chances of surviving, and more importantly, improves the likelihood of surviving with a good neurologic recovery.
"Brain Protective Therapy"
"It's similar to the person who falls through the ice on a lake and spends 15 or even 20 minutes underwater without oxygen, but still makes a full recovery," said Darren Bean, MD,* an emergency and UW Med Flight physician who directs the Level One Heart Attack Program at UW Hospital.
"When the brain suffers an injury resulting in low blood flow, there can be an area of the brain that is irreversibly injured. However, there is a significant area of surrounding brain tissue that remains exceedingly vulnerable post injury," Bean explains.
"This area is often injured (secondary brain injury) by a cascade of events we do not fully understand. Induced mild hypothermia can be a very effective, immediate brain protective therapy that greatly slows progression of secondary brain injury," adds Bean.
The Cooling Process
For patients transferred to UW Hospital via Med Flight, cooling is started as soon as possible in the community emergency department by "packing" the patient with ice packs and infusing ice-cold normal saline through an IV. This cooling process is continues in flight.
At UW Hospital, a cooling catheter is placed into the deep vein of the thigh, which rapidly drops body core temperature to precisely 34 degrees Celsius. This slows down metabolism and protecting brain function while reducing demand on the heart.
If the patient is having a heart attack, the cooling is done while the patient undergoes emergent angioplasty, where a balloon is used to open the blocked heart artery and restores blood flow to the starving heart muscle. After 24 hours, the cooling catheter is removed and the patient is rewarmed.
Clinical trials have demonstrated the technique improves the likelihood of a good neurologic outcome in patients treated if induced hypothermia is used during the first 24 hours of their care. The American College of Cardiology and the American Heart Association have recently adopted post-arrest hypothermia as recommended therapy.
Emphasis on Speed
The mild hypothermia technique is one of several new protocols being used to treat heart attack patients through UW Hospital and Clinics Level One Heart Attack Program. The program is designed to treat heart attack patients much like trauma patients, with an emphasis on speed and the quick delivery of appropriate critical care.
"The concept of the golden hour long associated with trauma care is now being applied to regional cardiac care," said Bean. "The new program allows physicians to activate UW Med Flight and interventional cardiology team within the first 30 seconds of the phone call."
"As soon as a patient is identified having a severe heart attack, emergency departments can call a 24-hour hotline at UW Hospital," Bean explains. "The call immediately activates Med Flight and UW Hospital's cardiac catheterization lab to prepare for the patient."
According to studies in Europe, Level 1 heart attack protocols reduce rates of death, recurrent heart attack, or disabling stroke for patients who are transferred faster for angioplasty.
Bean says the protocols have dramatically reduced treatment times and that translates to improved survival and improved quality of life for patients.
* Note to readers: This article includes quotes from Dr. Darren Bean, who tragically died in the UW Health Med Flight crash Saturday, May 10, 2008. A passion for emergency services was at the core of Dr. Bean's compassionate commitment to the health sciences and for this reason, his quotes are included in tribute to this passion. He will be missed by all who knew, respected and loved him.
Date Published: 06/16/2008