Cooling heads and hearts versus cooling our heels.

Evidence suggests that full implementation of therapeutic hypothermia after cardiac arrest could save thousands of lives each year. Critical unanswered questions persist, beginning with a lack of evidence in regard to how early cooling should be initiated, which cooling strategy is most effective at cooling the brain, and, ultimately, what method of cooling is most optimal for survival. Two reports in this issue of Circulation, from Castren et al1 and Bernard et al,2 begin to provide some of these needed data. Given the immense logistic difficulty of performing randomized field studies, the teams of investigators involved in both studies are to be congratulated for conducting this important research. The presented results begin to explore the important question of how quickly and by what methods cooling should be started in the field. Although they provide some answers, they also provoke new questions. For clinicians using therapeutic hypothermia with cardiac arrest patients, it is important to clearly understand the pros and cons of earlier cooling initiated in the field with the newer techniques explored in these 2 reports. It is also important to understand the differences between the findings in these studies, along with the practical implications and limitations of each technique, before conclusions are drawn about the manner in which these studies may influence practice.