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.
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