Keith Churchwell, MD
Keith Churchwell, MD, assistant professor of medicine, executive medical director, Vanderbilt Heart and Vascular Institute, Nashville, Tennessee.
A danger with emergency treatment for cardiac arrest is that the heart may get restarted, allowing the patient to live — but with brain damage due to oxygen deprivation. However this sad story may become less common because of a life-saving technique for cardiac arrest patients taking hold in ERs and hospitals around the country. You may have heard news of this process, called therapeutic hypothermia, which cools the patient’s body for up to 24 hours to protect the brain by slowing its need for oxygen.
Hypothermia has actually been used since the 1950s to protect vital organs and decrease pain in open heart surgery. Doctors attempted the technique with cardiac arrest patients but soon abandoned their efforts, saying it was difficult to perform and outcome was uncertain for this particular group of patients. Fast forward about 50 years, to 2002, when several small studies — one in Europe and another in Australia — demonstrated the successful use of hypothermia for cardiac arrest patients and found that treatment did indeed save lives and also helped preserve brain function. In the European study 55% of the hypothermia patients had favorable neurological outcome and were able to live independently and work at least part-time at six months, compared with 39% of patients receiving standard treatment. It also helped reduce mortality — where there were 76 deaths in the standard treatment group, only 56 of the 137 participants in the hypothermia group had died at the six-month mark. A growing number of major hospitals now use this treatment, either in the ER or in cardiac units. In New York City, for example, ambulances now take many cardiac arrest patients to the nearest hospital that offers therapeutic hypothermia rather than a closer ER, according to The New York Times.
To be effective, hypothermia should start within six hours of the cardiac event. The body’s temperature is chilled to about eight degrees below normal, where it will remain for up to 24 hours. Patients are sedated to prevent shivering, which would serve its natural function — to warm the body — and afterward are gradually warmed in a process that takes about eight hours. Patients who are eligible for hypothermia are those whose hearts have been revived sufficiently to show a pulse and who do not have heart problems associated with other trauma (for instance, from an accident). Cooling the body slows the metabolic action of the brain and seems to reduce the production of free radicals and the other deleterious effects that anoxia (being deprived of oxygen) has on all organ systems, especially the brain, after cardiac arrest.
I asked cardiologist Keith B. Churchwell, MD, executive medical director, clinical services at the Vanderbilt Heart and Vascular Institute in Nashville, Tennessee, how all of this works. He told me that some hospitals perform hypothermia by infusing chilled IV fluids, while others wrap patients in a special device that cools their bodies. Since patients benefit by starting the therapy as early as possible, many EMS crews now start cooling the patient in the ambulance with chilled intravenous fluids and ice packs. Dr. Churchwell told me that administration of hypothermia requires precise interaction among the entire medical team, including cardiologists, neurologists, emergency medicine physicians, nurses and technicians. Patients must be monitored closely to be sure their temperatures remain low enough, but not too low, which puts them at risk for complications including internal bleeding, arrhythmias and infection.
Even while patients are receiving hypothermia therapy, the medical team can treat the heart problem, Dr. Churchwell said. They can even insert a stent or perform angioplasty — in fact, he said that often outcome is improved by performing concurrently with hypothermia. Patients are resuscitated, stabilized and remain under monitoring, but with a decreased blood flow to the brain until the heart is fully prepared to take over efficient blood circulation once again. Dr. Churchwell said that as yet, there’s been no evidence that any long-term damage results from this form of treatment and that he expects this may someday become the standard of care.