With only an eight percent survival rate, cardiac arrest has a devastating effect on some 300,000 victims in the United States each year. Of those who survive, many are left with damage to brain tissue. Physicians here in New York City and across the country are fighting back with a “cool” advanced technology.
When administered during cardiac arrest, therapeutic hypothermia safely lowers the patient’s body temperature and protects the brain from severe damage caused by the lack of oxygen-rich blood. “Hypothermia slows metabolism in the tissues, including the brain, so the cooling effect acts as protection,” says Eyal Herzog, MD, Director of the Cardiac Care Unit at St. Luke’s Hospital.
Steps for better outcomes
Therapeutic hypothermia has been in use for more than five years and is not a stand-alone treatment. In fact, it works best when done in concert with quick emergency medicine, both in the field and at the hospital.
In cardiac arrest events, traditional life-saving methods such as CPR or defibrillation will first be used to resuscitate the patient until first responders can get them to an emergency department. With the introduction of hypothermic therapies, emergency responders may also apply cooling blankets or iced saline, to start lowering body temperature and preserving delicate tissue in a non-invasive way.
Cooling the body fast
In less than 90 minutes from arriving at a Continuum hospital, adult cardiac arrest patients will be sent to the cardiac catheterization lab to diagnose and open the closed artery. At the same time, physicians start therapeutic hypothermia in three phases.
- Invasive cooling for the first 24 hours. A specialized catheter is usually placed in the femoral vein in the leg that delivers cold saline until the body temperature drops to 33 degrees Celcius (or 91.4 degrees Fahrenheit). “This way, we can quickly reduce the temperature from 98.6 degrees Fahrenheit to 91.4 F, which helps preserve brain function when time is of the essence,” Dr. Herzog notes. This method is a closed loop system-with no fluid infusion to the patient.
- Re-warming the body. After a 24-hour cooling period, doctors slowly bring the body temperature back to normal. “Re-warming has to be done very slowly by raising the body temperature by 0.25 degrees C every hour,” Dr. Herzog explains. “It takes about 16 hours to safely raise the patient’s body temperature back to normal, which is 98.6 degrees Fahrenheit.”
- Maintaining normal body temperature. During the last phase of the hypothermia treatment, a patient’s body temperature is kept at exactly 98.6 degrees F for 24 to 48 hours after re-warming to prevent fever, which can worsen brain damage. Patients often remain in the intensive care unit for at least a week throughout the treatment.
During this treatment a neurologist will evaluate brain function and help the patient’s medical care team decide the best plan of care. “Hypothermia protects the brain, but we have to make sure to protect the heart,” Dr. Herzog says. “Some patients are treated with an implantable defibrillator, which sends a small electrical shock to the heart when it recognizes abnormal heart rhythms that could lead to cardiac arrest.”
Continuum hospitals implemented the protocol for therapeutic hypothermia in 2008. “More patients who come to a Continuum hospital with cardiac arrest will be able to survive it because of our hypothermia protocol,” Dr. Herzog says.
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