Now We Can Warm From Within

Peri-Anesthesia Hypothermia –


Warming hypothermic animals is difficult. Yet the majority of anesthesia patients have lost a significant amount of body heat before the procedure even begins. Smaller dogs and cats lose nearly 2ºF while waiting for induction of anesthesia. Then they rapidly lose  another 2º-4ºF during the first fifteen to thirty minutes after induction. This describes the challenges we face with the complex and difficult to manage syndrome: Peri-Anesthesia Hypothermia.

The Pre-Warming Solution

The reasons for up to 80% of anesthetized cats and dogs to become hypothermic include their small body size, vasodilation, inhaling cold, dry anesthetic gases, lack of shiver-response, and open body cavities during surgery. The key to solving this problem is pre-warming the patients.

It seems counter intuitive to provide thermal support before a patient needs it, but recent research shows that warming patients before induction can prevent that initial drop in body temperature, and may slow the rapid heat loss immediately following induction. This rationale sounds similar to pre-oxygenating, doesn’t it? It turns out that pre-warming is highly effective and easy to do. Just place the pre-medicated patient in a warm cage.

Warming a cage may sound simple enough, but all cage heating techniques are not created equal. Heating devices like heat lamps, jugs of warm water or heated rice bags, which are not specifically designed to warm sedated or anesthetized animals, can burn them. The margin of safety for causing significant thermal injury to animals is surprisingly narrow.

Forced warm air blanket systems are ideal to pre-warm cages because they safely deliver a constant flow of warm air at thermostatically controlled temperatures. However, all blanket systems are not created equal either. Forced warm air blanket systems built for humans are not specifically designed to make use of the fur that traps warm air against an animal’s body, and that limits their effectiveness.

Warmed Inspired Anesthetic Gas

There are many ways to reduce patient heat loss during anesthesia. You can minimize surgical prep time, insulate the patient’s feet, use warm IV fluids, and use forced warm air blankets before, during, and after anesthesia. However, none of these methods adequately address the rapid heat loss in the first fifteen minutes after induction. Just imagine how useful it would be if you could warm the inspired anesthetic gases. That way you could capture control of a patient’s body temperature at intubation, rather than playing catch-up as the procedure progresses.

Advanced Anesthesia Specialists ( recently introduced two innovations to the veterinary market. One is the Cocoon® forced warm air blanket system, that is proven to warm patients rather than just slow the rate at which they cool. The other is the world’s first heated breathing circuit. These smooth-wall heated circuits warm the inspired gases, allowing you control of patient hypothermia from the moment of intubation. Using these in combination is shown to adequately manage Peri-Anesthesia Hypothermia. For more information, click here.

Ken writerKen Crump ( is a writer and animal anesthetist and writes Making Anesthesia Easier for Advanced Anesthesia Specialists.  He makes dozens of Continuing Education presentations on veterinary oncology and anesthesia across the United States and in Canada.  Ken retired from Colorado State University in 2008. 
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