The Dangers of Hypothermia
Tracking your patient's temperature and staying ahead of their heat loss is a vital part of patient care, especially when it comes to anesthesia. The moment you discover that your patient's body temperature has dropped below a normal range it may have already begun to create complications for your patient. When one of our patients undergoes an imaging study and surgery they can be under anesthesia for hours on end. Without any heat support your patient can quickly end up in trouble.
Normally, the body temperature of a dog or cat should be somewhere between 38.3 and 39.2 degrees celsius. Any temperature below 37 degrees is considered to be hypothermic based on the patient's baseline temperature. From 37 to 32 degrees is mild hypothermia, 32 down to 28 is considered moderate, while severe hypothermia is anything below 28 degrees celsius. With anesthetic cases the heat loss is typically minimal and mild hypothermia is the only real concern, though it can still cause major complications for the patient.
When it comes to anesthetic cases, hypothermia occurs in three phases over the course of several hours if nothing is done to maintain the patient's temperature. The first hour after induction is the most critical in which a patient can rapidly loose body heat as warm blood is redistributed to the periphery of the body. For every hour of heat loss it can easily take two hours to regain and maintain that same amount of heat. This is why it is so important to have temperature monitoring and heat support in place prior to starting anesthesia. This first hour comprises the first phase of heat loss the second of which occurs during hours two to three. During this second phase the patient continues to loose heat though at a lower rate as the body is losing heat more rapidly than it can produce it. In the third phase, four hours or more, the body temperature stabilizes at a low temperature and severe side effects begin to set in.
Even mild hypothermia can cause major problems for your patient and complicate what could be an otherwise stable anesthesia. Cardiac arrhythmias, decreased oxygen saturation, impaired kidney function, vascular constriction, decreased drug breakdown and absorption, and even death can occur with just a mild to moderate decrease in the patient's body temperature. Other functions such as wound healing, cognitive changes, increased risk of infection, and clotting irregularities can be lasting affects of hypothermia even after the patient has regained a stable body temperature.
We get a lot of questions about what we do to prevent heat loss in our patients during our procedures. So here are a few tips and some ideas of the ways that we maintain body temperature.
Temperature Monitoring: Utilizing a temperature probe connected to the patient monitor or manually checking temperatures no less than every 30 minutes is a great way to ensure that you are doing everything to maintain your patient's temperature. This is also good to prevent overheating of the patient if you have active warming in place.
Passive Warming (Insulating): Our favourite passive warming option is the use of a thermal insulating blanket specially designed for veterinary use. It's as simple as just placing it on the patient and it can help maintain constant temperatures even over several hours. At the very least just covering your patients with blankets can make a huge difference in reducing their heat loss during a procedure. Make sure that the patients paws are covered as they lose an exceptional amount of heat through their pads.
Active Warming: Circulating warm water blankets, both flexible and solid surface versions depending on the application and environment, are a great option for adding active warming to your patient. The solid surface warming pad is awesome because of the number of soft water blankets that we've had puncture. It is important to make sure you're cleaning the pumps regularly on these units and changing the distilled water often to prevent bacteria growth in the system.
Forced air warming units are another excellent choice and we use them throughout the clinic: before, during, and after our procedures. It is vitally important to make sure there is a barrier between the patient and any active warming to prevent contact hot spots especially on the paw pads and with short haired or hairless breeds. If you are using active warming in the form of warming discs, hot packs, water bags, etc. it is very important to keep a close eye on your patient and the area nearest to the object. Many of these have been known to cause burns on animals especially items that are warmed by being microwaved. These should only be used for short periods of time and should never come in direct contact with the patient.
If you have any other questions regarding hypothermia or the items that we use at the VSCAN feel free to reach out to us.