In 2002 Therapeutic hypothermia, now called Targeted Temperature Management was expected to revolutionize treatment of patients with cardiac arrest, neonatal hypoxic-ischemic encephalopathy, stroke and traumatic head injury. Medical equipment manufacturers rushed their versions of cooling devices into production. Therapeutic hypothermia was about to become as routine as aspirin… until December of 2013, when New England Journal of Medicine (NEJM) published a large multinational study of adult patients suffering from cardiac arrest. This study showed no benefit in outcomes between those who received hypothermia and those who did not. During the following months the enthusiasm of using hypothermia in adults vanished. At the same time study after study demonstrates benefits of Therapeutic Hypothermia in newborns suffering from hypoxic brain injuries, and cooling following catastrophic deliveries is routinely used in infants. Newborns suffering from hypoxic brain injuries that receive cooling therapy are shown to have better survival rate, higher IQ and higher cognitive function.
Is there an explanation to this discrepancy? Since newborn brain cells function and structure is not fundamentally different from adult brain cells, the explanation lies somewhere else. In fact, the explanation is rather simple. Early studies of animals and humans, conducted prior to early 2000s demonstrated that achievement of target body temperature of 33-35° C within minutes to about an hour following brain injury decreases mortality and improves neurological recovery. Achieving fast body cooling becomes a key factor. Target body temperature can be easily achieved in newborns literally within minutes, but with current equipment it is nearly impossible to achieve target body temperature within the time window of opportunity in adults. This are the reasons:
- FIrst, newborns suffer from brain injuries in hospitals, usually in Delivery Rooms, with Neonatal Intensive Care Units located only minutes away, whereas adults suffer from brain injuries almost exclusively outside of the hospitals. Newborns can be attached to a cooling system within minutes, whereas adults must be first resuscitated, then transported to Emergency Room, then undergo testing and stabilisation and only then transferred to Intensive Care Unit where body cooling is usually initiated.
- Second, newborns, especially soon after birth are not capable of maintaining normal body temperature without assistance, such as drying, clothing, close contact with mother, whereas adults can.
- Third, the most popular cooling devices are based on plastic body wraps percolated with ice cold water. This is where the biggest difference between babies and adults comes to play: newborns body surface area to weight ratio is four time higher than in adults, making babies cool four times faster.
There are at least ten different hypothermia devices in the US market built on distinctly different physiological mechanisms of cooling. The main reason for disappointing results of using hypothermia in adult patients is due to the lack of a commercially available device that meets the necessary requirements for achieving fast rate of cooling. The ideal Therapeutic Hypothermia / Targeted TEmperature Management System should meet the following criteria:
- It must be effective and capable of providing fast rate of heat loss to achieve target body temperature within an hour after the insult.
- It should be minimally invasive to reduce the spectrum of potential complications.
- The device must be unobtrusive, allowing easy access to the patient, especially during CPR.
- The device should be portable and usable in pre-hospital settings, such as ambulances.
- It has to be easy to operate without requiring lengthy training.
- It should allow precise temperature maintenance during cooling, maintenance and re-warming stages.
None of the commercially available Targeted Temperature Management Systems meet all of these criteria. We believe, that broad range of equipment for induction of hypothermia and temperature management and subsequent lack of uniformity in cooling methods combined with inability to meet the requirements listed above are the main reasons for disappointing clinical outcomes and low utilization of therapeutic hypothermia. The study described at the beginning of this page was a perfect illustration of the problems with the use of hypothermia in real life situations: people enrolled into the study had their body temperature reduced to desirable range within 6 hours after cardiac arrest, when the window of opportunity to achieve brain protection was already closed. A simple, easy to use, portable and small hypothermia induction device with minimum side effects can become a standard in providing hypothermia therapy. Dr. Sergei Shushunov in collaboration with The University of Kansas Department of Engineering have designed and built a prototype body cooling device based on using hyper cold air with either manual or mechanical ventilation that all patients with life threatening emergencies receive. This new method of inducing, maintaining and reversing hypothermia will eliminate the problems of existing types of hypothermia induction devices and will replace equipment currently in use. This revolutionary device will bring uniformity to the hypothermia equipment industry and expand the use of therapeutic hypothermia equipment to pre-hospital settings, such as ground and air ambulances as well as military field hospitals – the perfect settings for starting therapeutic hypothermia.
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