Therapeutic hypothermia for acute ischemic stroke

Intravenous recombinant tissue plasminogen activator remains the only US FDA-approved treatment for acute ischemic stroke. However, the very limited time window for its administration restricts its usefulness. Furthermore, it is becoming increasingly clear that, given the numerous pathways via which cerebral ischemia causes cell death, the capacity to inhibit multiple mechanisms simultaneously may provide additive or synergistic beneficial clinical effects for stroke patients. Although no clinical trials have yet investigated the efficacy of therapeutic hypothermia in focal cerebral ischemia, its pleiotropic neuroprotective actions, positive results in preclinical studies, as well as proven enhancement of neurologic outcomes in survivors of cardiac arrest and newborns with hypoxic-ischemic encephalopathy, make this neuroprotective strategy highly promising. This review presents an overview of the potential role of hypothermia in the treatment of acute ischemic stroke and discusses ischemic cell death pathophysiology, neuroprotective mechanisms of hypothermia, methodologies employed for the induction of hypothermia, results from animal models of cerebral ischemia, and finally, currently available clinical trial data. Two valuable lessons learned thus far are that first, rapid induction of hypothermia is key and is best accomplished with a combination of ice-cold saline infusion and the use of endovascular cooling devices, and second, that shivering can be overcome with aggressive anti-shivering protocols including meperidine, buspirone and surface warming. We await the results of clinical trials to determine the utility of therapeutic hypothermia in acute ischemic stroke. If proven efficacious, hypothermia would be a welcome complement to established reperfusion therapies for ischemic stroke patients.