New Drug-Induced Hypothermia Could Save Lives Before Hospital Arrival

The development of drug-induced hypothermia could offer a critical new method for saving patients experiencing strokes, cardiac arrests, or spinal cord injuries before they reach a hospital. This approach aims to lower body and brain temperature to reduce disability and mortality.

The concept of using hypothermia to aid healing is not new. Therapeutic hypothermia, which involves lowering a patient's core temperature to between 33-34 degrees Celsius (91.4-93.2 degrees Fahrenheit) for 12 to 24 hours, is already a recognized treatment for traumatic brain injuries, spinal cord injuries, cardiac arrests, and oxygen deprivation in newborns. This process slows the brain's metabolic rate, decreases inflammation, and prevents brain cell death, thereby improving the chances of recovery.

Currently, therapeutic hypothermia is administered in hospitals using methods like cooling blankets applied to the skin or infusing cold saline solution directly into the bloodstream. These methods can be time-consuming, potentially delaying crucial treatment during the "golden hour"—a critical window for stroke patients where prompt intervention significantly increases the likelihood of avoiding long-term disability and improves survival rates.

A study conducted by scientists at Capital Medical University in Beijing investigated the use of two medications, chlorpromazine and promethazine, which have been in use since the 1950s for other conditions. When combined, these drugs were found to significantly lower the body temperature in mice and primates and reduce brain damage following a stroke.

A subsequent clinical trial involving 32 patients who had experienced ischemic strokes showed a temperature drop of approximately 1 degree Celsius (1.8 degrees Fahrenheit) at the highest dose. However, this reduction was deemed insufficient to induce hypothermia in humans, possibly due to differences in surface area to body mass ratio compared to the animal models.

Experts suggest that drug-induced hypothermia may offer advantages over physical cooling methods. One theory is that these drugs might interact with the brain's thermostat to prevent shivering, the body's natural response to generate heat. Physical cooling methods do not prevent shivering, which can counteract the intended cooling effect. Additionally, drugs may widen blood vessels, facilitating heat release and reducing metabolic rate.

Researchers are also examining the potential of common over-the-counter medications like paracetamol, aspirin, and ibuprofen to induce rapid cooling. Studies indicate that paracetamol, for instance, can lower body temperature by as much as 1 degree Celsius for up to four hours by inhibiting COX-1, an enzyme involved in raising body temperature. However, some experts caution that achieving sufficient cooling with single household medications may require high doses, potentially leading to toxicity. For example, excessive paracetamol can cause liver damage.

While the prospect of pre-hospital drug-induced hypothermia is promising, researchers acknowledge that more work is needed to determine effective and safe dosages and drug combinations for human use. The initial clinical trial results, showing only a minor temperature reduction, highlight the challenges in translating findings from animal models to human physiology. Some experts remain cautious about the immediate prospects of this approach, noting that the cooling effect observed in humans was too small to be clinically significant.