PHOENIX, ARIZ.—Therapeutic hypothermia after cardiac arrest offers proven neurological benefits to patients and should be implemented in hospitals worldwide, Simon R. Dixon, M.B., said at a congress of the Society of Critical Care Medicine.
Only about 20 hospitals in the United States are doing therapeutic hypothermia, said Dr. Dixon, codirector of cardiovascular research at William Beaumont Hospital in Royal Oak, Mich.
Medical staffs have been slow to adopt hypothermia, despite an International Liaison Committee on Resuscitation (ILCOR) task force advisory statement (Circulation 2003;108:118-21) endorsing its use after cardiac arrest, he said.
“This statement should really serve as a call to action to physicians around the world that hypothermia is here, and we should be doing it to improve care to our patients,” he said. “And it's discouraging that even though this statement was issued 2 years ago, adoption of this therapy is so slow throughout the world.”
Although much effort goes to improving resuscitation of cardiac patients, little has been done to improve neurologic dysfunction. “It is important to remember that neurological aspects determine the longevity or most of the disability in these patients when they go home,” he said.
The ILCOR statement followed two trials that found patients had better outcomes if given therapeutic hypothermia after cardiac arrest. The percentages of hypothermia patients with favorable neurologic recovery were 49%—versus 26% for a control group—in an Australian study (N. Engl. J. Med. 2002;346:557-63) and 55%—versus 39% for controls—in a European study (N. Engl. J. Med. 2002;346:549-56).
Other studies, published (Am. J. Physiol. Heart Circ. Physiol. 2002;282:H1584-91) and ongoing, have also indicated that therapeutic hypothermia can reduce the size of an infarction, Dr. Dixon noted.
“These two trials suggest if the heart can be cooled adequately by the time angioplasty is done, probably there will be benefit from hypothermia,” he said, citing the Cooling for Myocardial Infarction (COOL MI) and Intravascular Cooling Adjunctive to Primary Coronary Intervention (ICE-IT) studies.
Dr. Dixon concluded that evidence clearly shows hypothermia to be safe and effective. Nonetheless, training requirements and fear of side effects have so far inhibited wider use, he said.
Session moderator Stefan A. Mayer, M.D., a consultant to and shareholder in several hypothermia device companies, also urged greater use of the therapy in cardiac cases. Dr. Mayer, director of critical care neurology at Columbia University, New York, warned that uncontrolled fever can be damaging and ongoing in ischemia and in stroke.
“In cardiac arrest you've got to make them hypothermic,” he said. “Why wait for a patient to get febrile and try to get it [temperature] down? That's like waiting for the toothpaste to get out of the tube and try to get it back.”
One Hospital's Experience With Therapeutic Hypothermia
Therapeutic hypothermia is not risk free, but its side effects are predictable and can be managed, according to a physician who has 8 years' experience cooling critically ill patients at the Free University Medical Center in Amsterdam.
“Our treatments can have severe side effects, but the good news is most side effects of hypothermia can be prevented or controlled. So fear of side effects should not prevent you from using this,” internist/intensivist Kees H. Polderman, M.D., said at a congress of the Society of Critical Care Medicine.
The optimal duration and depth of cooling and time to rewarming have yet to be determined, Dr. Polderman said. Nonetheless, he maintained that therapeutic hypothermia could be used safely for cardiac protection as well as neural protection.
“Start cooling as early and as quickly as possible, both to produce the effects we are looking for and to reduce the severity of some side effects,” he advised. “Do not rewarm too fast.”
Dr. Polderman encouraged physicians to educate themselves on the physiologic changes and side effects that can be expected before starting hypothermia. They need to know “which are harmful, which we can treat, and which we can ignore,” he said.
Among high-risk side effects, Dr. Polderman cited coagulopathy, impaired coagulation cascade, electrolyte disorders, and hypovolemia. He warned that insulin sensitivity and insulin secretion both decrease, so physicians need to monitor glucose and to be prepared to avert hyperglycemia. Amylase, platelets, and white blood cells also need to be monitored, he said.
The hospital laboratory must be told that the patient is being cooled because temperature can alter laboratory test results. In addition, pharmacokinetics of some medications can change, but for many drugs these effects are not yet known, he warned.
Dr. Polderman listed manifest bleeding, severe coagulation disorders, airway and wound infections, and myocardial ischemia as low-risk events. Manifest pancreatic and intracerebral bleeding are rare, he said. Patients undergoing long-term cooling need antibiotic prophylaxis and protection against bedsores, he advised.