Selective Cerebral Hypothermia: A New Tool to Really Cool

The neuroprotective effects of therapeutic hypothermia (TH) following cardiac arrest and acute stroke have been demonstrated in numerous experimental models and clinical trials. In the laboratory, efficacy of hypothermia increased with cooling to lower temperatures. However, a recent large multicenter out-of-hospital cardiac arrest trial suggested that current evidence-based recommendations of TH at 32°C to 34°C be reevaluated, concluding that 33°C conferred no benefit compared to 36°C, and challenged findings of years of research. In the setting of acute ischemic stroke, clinical studies have shown that mild TH (32°C-34°C) is safe, but all have failed to show the efficacy seen in animal models. A critical review of the reported data suggests the technique of administrating TH may explain the discrepancies between bench and bedside. A new catheter-based system designed to provide rapid, selective, and deep cerebral hypothermia, may offer a more effective method for neuroprotection in the setting of acute stroke and cardiac arrest. In pigs, cerebral cooling to as low as 15°C, and cooling rates up to 1.8°C/minute were achieved with no significant systemic cooling. Passive rewarming did not result in rebound hyperthermia, and no adverse events were observed. In a stroke reperfusion model, a significant reduction in stroke volume was observed by selective cerebral cooling to 26°C compared to a normothermic control group. In initial human experience, selective cerebral cooling to 26°C resulted in excellent outcomes in the settings of neurosurgery and out-of-hospital cardiac arrest.