February 12, 2008
Therapeutic hypothermia is a “hot” topic
Joan Marie Pellegrini, MD
Therapeutic hypothermia is the cooling of a patient for medical treatment of a disease. Usually, providers in a hospital spend quite a bit of energy trying to prevent hypothermia particularly after surgery or in trauma patients. However, it has been known for decades that cooling the brain could help prevent injury during certain surgeries in which blood to the brain is at risk. In these situations, hypothermia was protective if started before the injury but it was unknown if it was protective if started after a brain injury. There is now much more knowledge about therapeutic hypothermia but also many more questions about its use and about which patients will benefit.
There are enough studies to now support the use of hypothermia in cardiac arrest patients who have been resuscitated but remain in a coma. These patients are in a coma because of the anoxic (meaning lack of oxygen) injury produced while there was no blood flow during cardiac arrest. If these patients are actively cooled soon after they are resuscitated, we now know that their chance of having a meaningful neurologic recovery (meaning they can live independently) is significantly improved. Many hospitals, including EMMC, have protocols in place to guide the care of these patients in terms of their cooling and rewarming. They are cooled as soon as possible but only for about 12 hours and then are slowly rewarmed. When the research was first being done, it was discovered that there are many possible complications to cooling a patient and much work was done to refine the technique to minimize these complications. These complications may be why earlier studies did not show a consistant benefit to cooling these patients. The most recent studies however, have answered the questions on how to do this safely. It is now safe to say that therapeutic hypothermia is accepted and even standard therapy in post-cardiac arrest patients who meet the criteria and are in a coma because of anoxic brain injury. It is still unknown how hypothermia helps the brain after cardiac arrest but it is believed that decreasing the metabolic demands and decreasing the inflammatory response are helpful
Other disease states that may benefit from this therapy are stroke patients and traumatic brain injury. There have been many studies in these patients and there continue to be ongoing studies. The use of hypothermia in these patients is still considered experimental and is controversial. One of the reasons these two patient populations are difficult to study is that the brain injury can be very different from one patient to the next. One question that research will need to answer is which of these patients, if any, could benefit from therapeutic hypothermia and how does the clinician identify these patients.