How Safe are Anesthetics in Vet Med?
February 21st, 2010 Posted in UncategorizedHOW SAFE IS ANESTHESIA?
(from Dr. Langlais’ column in The Record)
Q: Someone at work told me their cat died on Friday under anesthetic. How common is that? Do they offer anesthetic screening with cats, or just dogs? If so, how common is that screening and how expensive is it?
A: My sympathies to your co-worker and to anyone who has had an animal die under an anesthetic.
Fortunately, anesthetic deaths are pretty rare in most veterinary practices. Statistics seem to indicate that an animal is more likely to die in an accident in its owner’s car on the way to the hospital than under an anesthetic. However, there is always a small risk with any anesthetic, and things can go wrong. The patient might have a congenital heart problem that is not evident on a physical exam, or an animal might react unpredictably to the anesthetic agents. Or sometimes there is human error; even the best anesthesiologist might make a mistake at some time in his or her career.
How frequent are anesthetic deaths? Dr. Doris Dyson, an anesthesiologist at the University of Guelph, found 2.1 per cent of dogs and 1.3 per cent of cats undergoing anesthesia experienced complications. Only 0.1 per cent actually died. Dyson obtained these statistics in a prospective study of 66 small-animal practices; she published the results in 1993 in the Journal of the Animal Hospital Association.
A lot has changed in the field of veterinary anesthesia since then. I suspect the incidence of deaths is now significantly lower. What has changed? For one, we use much safer drugs. Our sedatives and anesthetics are better than ever. For example, years ago, vets used to use long-acting barbiturates. These have many side effects and a narrow margin of safety. Anesthetic deaths were more common with their use, and it used to take pets days or weeks to recover.
I don’t personally know any veterinarians who use this anesthetic any more. (Caution: if you choose a really “cheap” clinic for your pet’s surgery, there’s a chance they’re using inexpensive but dangerous anesthetic agents.) Many of us use isoflurane, an inhalant anesthetic, to maintain anesthesia in dogs and cats. Isoflurane has a great safety profile, and, because it is a gas, once we turn the anesthetic machine “off,” the animal is awake within minutes.
Secondly, we have some pretty cool monitoring equipment available now. End-tidal CO2 monitors measure the carbon dioxide expelled with every breath. They’re an early warning system if your pet isn’t breathing properly. Pulse oximeters clip to the animal’s tongue or ear and measure the percentage of oxygen in the bloodstream and the patient’s heart rate. Blood-pressure monitors help us watch for hypotension. All these monitors have alarms and allow us to detect trends before the patient has an anesthetic emergency. I suggest you always ask what monitoring is offered before your pet undergoes any anesthesia.
Pre-anesthetic screening is available for both dogs and cats. It is commonly offered at most veterinary clinics. I highly recommend it. The cost varies with the number of tests run, but it is quite affordable. It helps us screen for anemia or organ disease that might make an anesthetic more dangerous, and also gives us values that serve as a baseline in the future, for wellness testing.
I strongly feel that giving intravenous fluids during surgery or dentistry is important. The administration of fluids helps maintain adequate blood pressures, gives the anesthetist an intravenous access for drug administration should an emergency arise and helps the animal wake up more quickly. It also helps prevent that nasty post-anesthetic hangover. (I’ve had this and it felt terrible.)
Anesthetics are relatively safe, and the chance of complications is low, so don’t let the fear of anesthetic death deter you from choosing dentistry or surgery for your dog or cat. With the proper precautions, the chance of things going wrong is very small.
Here’s a nice YouTube video showing a dog being anesthetized for dentistry.
