Is faster still better in therapeutic hypothermia?

Conscientious clinicians will always be challenged when they try to translate the latest research into good clinical practice. It can be particularly frustrating to hear that your efforts might in fact be harmful.In the previous issue of Critical Care, Haugk and colleagues [1] report a retrospective analysis of 13 years of therapeutic hypothermia (TH) cases, suggesting a surprising association between faster rates of cooling and less favorable neurological outcomes. Their data generate some fascinating hypotheses and opportunities for future research but clinicians would be ill-advised, based on both our understanding of pathophysiology and the growing body of published evidence, to use this study as justification to relax efforts to achieve target temperatures as quickly as possible.Precisely how TH improves neurological outcome after cardiac arrest is not known, but the mechanism is probably multi-factorial. TH is thought to minimize the release and the effect of free radicals, excitatory neurotransmitters and protease cascades during reperfusion of ischemic brain tissue, and may decrease vasoconstriction and intravascular thrombosis leading to potential ongoing micro-ischemia [2]. TH may also amplify the release of neuroprotective proteins [3]. For any of these proposed mechanisms, initiation of TH as soon as possible following resuscitation should be preferable.Animal models that have been used to study TH have supported early, rapid cooling [4,5]. In fact, one of the greatest challenges of advancing animal research into the clinical realm has been the difficulty in matching the rapid induction methods achieved in the laboratory in human subjects, with the hopes of observing similar therapeutic benefits. Although no prospective, randomized clinical trials have assessed the effect of time to target temperature on neurological outcome, there are noteworthy signals from existing human trials that support a benefit to rapid cooling. Wol and colleagues [6] analyzed p