Clinical
Heating and cooling techniques for veterinary patients: Current Recommendations
A veterinary technician specialist in emergency and critical care reviews the current recommendations on safe and efficient warming and cooling in dogs and cats.
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How do you cool or warm your patient when you need to? Which methods are safe, and which are contraindicated? Questions like these are being asked in the AAHA Community with respect to both treating hyperthermia and hypothermia and maintaining a normal body temperature during anesthesia and surgery.
Over the years, there have been different ideas and protocols promoted as safe and effective. Those that were thought to be safe decades ago have in some cases fallen out of favor, and likewise, methods that were previously contraindicated have now been shown to be safe. For these reasons, it’s so important to keep up with the latest recommendations for the safe warming and cooling of veterinary patients.
To help answer questions about current recommendations, we asked Walter L. Brown, RVTg VTS (ECC), and experienced veterinary technologist and technician specialist in emergency and critical care, to weigh in. He said that because of the changes in recommendations over time, he sees a lot of confusion among veterinary professionals about which methods to utilize and how to implement them correctly.
“I believe it’s essential that we disseminate new research and techniques to veterinary professionals,” Brown said, “enabling them to implement these changes and enhance our patients’ outcomes.”
Warming
Patients can benefit from thermal support both as a treatment option (for hypothermia) and as a supportive option (during anesthesia and surgery, for example). Brown said that not all available warming devices are considered safe for patient use, however. He alluded to electric heating pads that provide direct heat to the patient. While they are efficient in their warming capability, they carry significant risk for thermal burns when the skin is exposed to high head from the pad and electrical injury, which is most likely to occur when a teething puppy chews on the pad’s power cord. This type of injury can lead to non-cardiogenic pulmonary edema as well, Brown added.
Other heating devices that should be avoided include heat lamps, which Brown says can cause burns at temperatures that are just slightly above body temperature if the exposure is prolonged, and any type of product that is warmed in the microwave and placed next to the patient. This includes rice bags, bean bags, water bottles, and fluid bags. “There is no practical way to regulate or ensure the safety of these heating devices,” he said.
Brown also warned that cage dryers should never be used as warming devices, a recommendation echoed by many professional veterinary associations and pet care providers, stating they pose serious and potentially deadly risks. “The enclosed, unmonitored heat can cause burns, overheating, and heatstroke, especially in animals that are already compromised or critically ill.”
In terms of recommended methods of thermal support, Brown highlighted circulating warm water pads and forced-air warmers. “These devices are generally safer,” he explained, “but still need monitoring to prevent the patient from becoming too warm.”
Other appropriate warming techniques include the use of a fluid warming cabinet to warm fluid for IV administration (this is preferred over the use of fluid line warmers) and warming towels in the dryer to place around a patient.
AAHA Standards on warming and cooling
AAHA’s standards cover a number of different patient care topics, including the safe and effective thermal support and cooling of patients when needed. Among the standards is one that states that one practice team member should be assigned to monitor a patient while a heating or cooling device is in use.
Another standard specifies that heating pads and cage dryers are not to be used as warming devices and stipulates that in-line fluid warmers should only be used if they display the fluid temperature and/or have a visual or audible alarm that would indicate if the fluid temperature exceeded set parameters.
Cooling
Cooling methods become important in cases of hyperthermia, which can be related to heat stroke. Brown advised that it is very important to differentiate between hyperthermia and fever when deciding if cooling measures are appropriate. He said that in patients with a true fever, cooling is often contraindicated.
“In dogs, the main difference between a true fever and heat-induced hyperthermia is the role of the hypothalamus,” he said. “A fever is a regulated, intentional response where the hypothalamus ‘resets’ the body’s internal thermostat to a higher temperature.”
Hyperthermia, Brown explained, is “an uncontrolled and unregulated increase in body temperature caused by external factors, with the hypothalamus attempting to correct it.” It’s these patients who will benefit from cooling measures.
How to best cool patients has been widely debated over the years. While it was previously thought that submerging patients in cold water would lead to vasoconstriction that would prevent adequate cooling, newer research indicates that this technique is an efficient and safe way to cool patients as long as they are being monitored during the process. “Submerge the trunk and extremities in cold water, keeping the head above to prevent drowning,” Brown said. “Stop cooling once the dog’s temperature reaches about 102.5–103°F to avoid overcooling.”
Other appropriate cooling devices include fans, cool water blankets, and wet towels, Brown added, with a caveat. “We need to be cautious when using cool towels. When using this method, avoid covering the entire body, as it could trap heat and worsen hyperthermia.”
He also explained that the safest method will depend on the condition being treated. With heat stroke, for example, it may be appropriate to utilize multiple measures including use of a fan, offering cold water, applying a wet towel, and immersion in an ice bath.
In cases where a patient needs cooling simply to prevent hyperthermia, Brown said, running a fan outside of their cage is likely sufficient.
One previously recommended method of cooling that has fallen out of favor is the application of isopropyl alcohol to paw pads and skin due to concerns for toxicity, the potential for resultant tissue damage, and inefficient cooling. “In contrast to popular myth, isopropyl alcohol can cause the blood vessels near the skin’s surface to constrict,” said Brown. “This traps heat in the body’s core, which is the opposite of what is needed to treat heatstroke.”
Monitoring and education
Even with techniques and devices that are considered to be safe and efficient, Brown stressed the importance of frequent patient monitoring to determine if measures should be continued and to identify any adverse effect of their use quickly. “Monitoring and team education are the gold standard for safe use of cooling and warming devices in veterinary medicine.”
As a member of the AAHA Community, you can also learn more from your colleagues and AAHA accreditation specialists on this topic on these threads:
Photo credit: Sergii Kolesnikov/iStock via Getty Images
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