By Dr. Becker
Hypothermia is a medical condition in which the body is unable to maintain normal temperature. Mild hypothermia in dogs is classified as an abnormally low body temperature can cause central nervous system depression and problems with cardiovascular, respiratory and immune system function.
There are three phases of hypothermia: mild, moderate, and severe. Mild hypothermia is classified as a body temp of 101.3°F-97.7°F, moderate is 97.7°F-93.2°F, and severe is a body temperature under 93.2°F.
One of the causes of hypothermia is undergoing general anesthesia, and in fact, between 30 and 60 percent of humans who receive anesthesia for surgery or another medical procedure experience hypothermia. That may seem like a surprisingly high number, but the results of a new study on dogs and hypothermia are even more astonishing.
Vast Majority of Dogs (and Cats) Suffer Hypothermia as a Result of Anesthesia
The study was conducted by a research team from the Universidad CEU Cardenal Herrera in Spain and was published last summer in Veterinary Record1. It is the first global study to clinically document the frequency of hypothermia in dogs after surgery and other procedures requiring anesthesia. The results showed that 83.6 percent of 1,525 dogs developed hypothermia as a result of anesthesia.
This study clearly indicates hypothermia is a predictable complication of anesthesia in canines. It is especially prevalent in small dogs and dogs undergoing thoracic surgery (non heart-related chest surgery) or procedures that require prolonged periods of anesthetization.
Factors that increased the likelihood of hypothermia were the duration of pre-anesthesia and anesthesia, the general condition of the dog, and the way dogs were positioned during surgery. Dogs positioned on their stomachs with legs tucked under, or on their backs had lower body temps than dogs lying on their sides during procedures.
The dogs’ body temperatures were measured before induction of anesthesia, at 60 minutes after induction, and again at two and three hours post-induction. Body temps dropped continuously throughout the period of anesthetization. Mild hypothermia occurred in over half the dogs (51 percent), 29 percent experienced moderate hypothermia, and less than 3 percent experienced severe hypothermia.
According to Science Daily, a previous study performed by the same research team suggests that cats are even more likely than dogs to develop hypothermia while anesthetized. Almost 97 percent of cats develop hypothermia while receiving anesthesia, and kitties undergoing abdominal and orthopedic procedures are at increased risk.
These two studies suggest that hypothermia is the most common complication of anesthesia for both dogs and cats. The research team concludes that veterinary staff should continuously monitor the body temperatures of anesthetized animals and be proactive in preventing heat loss during procedures requiring anesthesia.
Ask Your Vet How He or She Monitors Body Temp and Prevents Hypothermia in Anesthetized Patients
The value of this study and the one done on cats is they clearly demonstrate the high rates of hypothermia during veterinary procedures requiring general anesthesia. Whereas the majority of pets will never develop other known complications of anesthesia, hypothermia is almost a given – especially if the animal is a cat, a small dog, or requires a certain type of procedure.
Fortunately, for over half the animals who develop the condition, it will be mild. But almost a third will develop moderate hypothermia, and for an unlucky few, the condition will be severe.
The American College of Veterinary Anesthesiologists (ACVA) and the American Animal Hospital Association (AAHA) have set forth guidelines that include evaluating body temperature as part of anesthesia monitoring of dog and cat patients during and after a veterinary procedure. Other monitored vital signs include respiration and pulse rate, blood pressure, blood oxygen and CO2 levels, and the electrical activity of the heart.
For patients who aren’t maintaining a normal body temperature while anesthetized (which will be most of them), supplemental heat can be provided through the use of warm IV fluids, a fluid line warmer, insulation on the feet, circulating warm water blankets, and/or warm air circulation systems. Supplemental heat sources should be designed specifically for anesthetized patients to prevent thermal injury.
If your dog or cat must undergo a procedure requiring general anesthesia, I recommend asking your vet not only how he or she monitors body temperature, but also how it is controlled during anesthesia and recovery. Because I practice exotic animal medicine, I bought a heated surgery table, which makes things really easy and benefits all of my surgical patients. My anesthetic monitoring equipment monitors my patients’ core body temperature, and one of my techs does as well, as a double-check.