By Dr. Becker
Most pet owners know that putting a dog or cat under anesthesia gets riskier the older the animal is. But many people aren’t aware that genetic differences among breeds and even a dog’s anatomy can also increase the risk of anesthesia.
For example, the “smashed in” faces of brachycephalic breeds put those pets at higher risk for airway obstruction than breeds with longer muzzles.
Then there are breeds predisposed to increased responsiveness to anesthesia. This means it takes less of the drug to produce the desired effect, which increases the risk for overdose. There are also breeds that take much longer to recover than other animals.
Another high risk group for anesthesia is pets with heart disease. If heart problems, either acquired or congenital, are known or suspected to exist, a veterinary cardiologist should be consulted before a procedure requiring anesthesia is performed.
The purpose of the following information is to make pet owners and caretakers of these breeds aware of the potential for anesthesia-related risks. Certainly your veterinarian and his or her staff should also be aware of breed-related sensitivities and take all necessary precautions before, during and after anesthesia. But as an informed pet owner, you can provide a double layer of protection in the care of your beloved four-legged companion.
Most brachys (for example, bulldogs, pugs, boxers, Boston terriers, as well as cats with “pushed in” faces) have some degree of brachycephalic airway syndrome. The stress placed on the airways from the use of anesthesia can result in additional airway contraction, which can cause obstruction.
Brachycephalic pets must be closely monitored from the point of premedication through the final step of extubation. Extubation (removal of the breathing tube) shouldn’t be attempted until the pet is awake, alert and swallowing. Removing the tube while the animal is still groggy from anesthesia increases the risk for upper airway obstruction.
Unfortunately, many brachys are overweight or obese and must be ventilated while anesthetized. One way to reduce your brachy’s anesthesia risk (and increase his overall quality of life) is to keep your pet at a healthy weight.
Sighthounds are so named because they hunt using sight and speed, whereas scent hounds hunt by scent and endurance. The greyhound, whippet, Italian greyhound, Afghan hound, Borzoi, Irish wolfhound and the Saluki are examples of sighthounds.
Sighthounds, especially greyhounds, are genetically inclined to metabolize drugs differently than other breeds. That’s why these dogs need a careful physical exam and comprehensive blood work prior to any procedure requiring anesthesia. They should also be tested for cardiac abnormalities like dilated cardiomyopathy.
Other considerations for sighthounds undergoing anesthesia:
- They tend to experience “white-coat effect” (hospitalization-related stress)
- They metabolize drugs more slowly than other dogs, and sometimes recover more slowly as well
- They are at higher than normal risk for hyperthermia while anesthetized because they have only about half the body fat of other dogs.
Herding dogs like the collie, border collie, Australian shepherd and the sheltie often have a genetic mutation in the ABCB1 (formerly MDR1) gene that allows certain drugs to accumulate in the brain – including some anesthesia agents. Without proper dosing and monitoring, these breeds can be over-sedated and experience respiratory depression.
Simply put, the smaller the animal, the higher the risk when administering any kind of drug, including anesthesia.
Toy dogs must be carefully weighed and the appropriate dose of anesthetic given based on their small size. Monitoring during the procedure is crucial (as it is for all patients, but in particular the tiny ones), including accurate blood pressure measurement.
Small dogs tend to have low body temps and hypoglycemia (low blood sugar), so it’s also important they be kept warm while anesthetized and their blood glucose levels monitored.
Now, you might think Newfoundlands or Great Pyrenees, for example, are so massive they need higher doses of anesthesia drugs in order to put them “under.” But the fact is, giant dogs often respond profoundly – in other words, they over-respond – to normal therapeutic doses of sedatives.
It’s important that these dogs are dosed according to lean body mass or surface area rather than actual body weight.
Dobies have a genetic variation which can cause von Willebrand disease, a problem with blood clotting. They also have a predisposition to develop dilated cardiomyopathy.
Dobermans should be evaluated for both conditions before any surgery is scheduled. If von Willebrand is suspected, a drug can be given prior to surgery. Also, the use of NSAIDs (non-steroidal anti-inflammatory drugs) in Dobies with von Willebrand disease is controversial, so other types of painkilling agents should be considered.
Boxers Bred in the U.K.
Rarely, certain dogs within a breed respond differently to anesthesia than other dogs of the same breed. An example: boxers from the U.K. are known to suffer heart arrhythmias, low blood pressure and collapse when given a standard dose (for U.S. boxers) of the sedative acepromazine.
Despite breed-related variations, what’s most important is that your vet and his or her staff customize an anesthesia protocol for your individual pet. As long as the proper pre-operative workup is accomplished and the pet is appropriately monitored – beginning with premedication and ending only after well-timed extubation – anesthesia can be safe for any breed of dog or cat.