Rapid and selective cerebral hypothermia achieved using a cooling helmet

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Hypothermia is by far the most potent neuroprotectant. Nevertheless, timely and safe delivery of hypothermia remains a clinical challenge. To maximize neuroprotection yet minimize systemic complications, ultra-early delivery of selective cerebral hypothermia by Emergency Medical Service (EMS) personnel in the field would be advantageous. The authors (W.E. and H.W.) have developed a cooling helmet by using National Aeronautics and Space Administration spinoff technology. In this study its effectiveness in lowering brain temperature in patients with severe stroke or head injury is examined.


Patients were randomly assigned to groups receiving either the cooling helmet or no cooling, and brain temperatures (0.8 cm below the cortical surface) were continuously monitored for a mean of 48 to 72 hours with a Neurotrend sensor and then compared with the patients' core temperatures. There were eight patients in the study group and six in the control group. The mean change in temperature (brain — body temperature) calculated from 277 data hours in the study group was − 1.6°C compared with a mean change in temperature of + 0.22°C calculated from 309 data hours in the control group. This was statistically significant (p < 0.0001). On average, 1.84°C of brain temperature reduction (range 0.9–2.4°C) was observed within 1 hour of helmet application. It took a mean of 3.4 hours (range 2–6 hours) to achieve a brain temperature lower than 34°C and 6.67 hours (range 1–12 hours) before systemic hypothermia (< 36°C) occurred. Use of the helmet resulted in no significant complications. There was, however, one episode of asymptomatic bradycardia (heart rate < 40) that responded to a 0.5°C body temperature increase.


This helmet delivers initial rapid and selective brain cooling and maintains a significant temperature gradient between the core and brain temperatures throughout the hypothermic period to provide sufficient regional hypothermia yet minimize systemic complications. It results in delayed systemic hypothermia, creating a safe window for possible ultra-early delivery of regional hypothermia by EMS personnel in the field.

Article Information

Address reprint requests to: William C. Olivero, M.D., Department of Neurosurgery, University of Illinois College of Medicine at Peoria, P.O. Box 1649, Peoria, Illinois 61656. email: olib@uic.edu.

© AANS, except where prohibited by US copyright law.



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    Photograph showing the helmet worn by William Elkins, a NASA scientist, who invented this technology. The cooling helmet has an outer pneumatic liner pressurized to allow close contact with the cranium and neck. The device also is adjustable to fit a significant range of head sizes.

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    Graph showing that, within 15 minutes after application of the cooling helmet, the brain temperature dropped by approximately 2°C, whereas the core temperature did not drop below 37°C until 4 to 5 hours later. The cooling helmet maintained brain temperature at approximately 1.5 to 2.5°C below core temperature throughout the 48-hour cooling period. When the core temperature dropped to 32°C and brain temperature dropped to 29.4°C, active body warming was initiated to minimize the risk of cardiac arrhythmia. After the cooling helmet was removed at Hour 48, the brain temperature approached the core temperature within 1 to 2 hours, and then both rose gradually to 37°C over a 30-hour period. B-temp = brain temperature; C-temp = core temperature.



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