All About Anesthesia

We hear it at least once a week: “She’s too old to do surgery on,” or “Well, I’m afraid of having her sedated.” And we certainly understand the apprehension that these owners and all the others with similar concerns feel. However, they’re doing their pets a disservice if they look at anesthetic procedures from just one view.

Risks in Anesthesia

Do anesthetics have risks? Absolutely. So do vaccines, and antibiotics, and your morning drive to work, and crossing the street. So why do we go forward with these procedures and activities if there are risks involved? Simple. Because the benefits outweigh the perceived risks. Anesthesia is no different.

First, let’s discuss today’s anesthetics. There are two phases to most anesthetic episodes:
1) Induction. This is the process of getting the pet from an awake state to one in which the pet can have an endotracheal (or ET) tube placed. The ET tube is placed in the trachea, or windpipe, to maintain an airway and deliver maintenance anesthesia.
2) Maintenance. Once the pet is tubed, anesthesia is maintained via ongoing gas administration. The gas keeps the pet asleep as long as it is administered. Once the gas is removed and pure oxygen administered the pet starts to awaken in just a matter of minutes.

I’ve been practicing long enough that I can remember using pentothal or its derivatives for induction of anesthesia. The problem with pentothal is that it was difficult to dose, slow to act, and slow to be removed from the body. In general, the faster an anesthetic acts and is removed from the body, the safer it is. Pentothal is very slow to act. Because of that and the fact that it was never administered as a calculated dose, but rather as a “dose to effect” drug, the pet often had issues either not going to sleep, or not waking up.

Pentothal stopped being used as an anesthetic induction agent sometime in the mid 1990’s. Today’s induction agents are much faster, have much wider margins of safety, and in most cases are not “dosed to effect,” but rather are calculated doses that work very predictably. We have different anesthetics that can be chosen specifically to avoid problems in pets with certain organ problems, such as renal compromise, liver problems, or cardiovascular insufficiencies.

And as for maintenance anesthesia, the gases we use now are much, much faster and safer than those we used 15 or 20 years ago. 20 years ago, a pet that was on gas anesthesia took about 30 to 60 minutes to wake up after gas was removed. Today, that number is about 5 minutes. And today’s gases support cardiovascular function much better than those of the past.

Assessing the Propriety of Anesthesia

The other thing to consider when trying to decide whether to allow an anesthetic episode is the actual procedure to be performed. One of the most common procedures we use anesthesia for is the routine dental. For instance, I’ll see a 12 year old poodle for routine vaccines, and during the normal physical exam determine that the teeth are very dirty, and well past due for cleaning.

Of course, routing dental cleaning involves full anesthesia. This is the time when I’ll hear the concerns listed above, such as “too old,” or “I’m afraid of anesthesia.” The point I always make to these owners is that while anesthesia has risk, not doing anesthesia – that is, not doing the dental – has even MORE risk. MUCH more risk.

Study after study has shown that bacteria from dirty teeth is responsible for up to 80% of bacterial infections in the liver, the kidneys and the heart. And in small dogs, especially, bacterial infections that attack the heart can lead to leaky heart valves, heart murmurs, congestive heart failure, and eventually death.

Likewise, small tumors that are not removed when they are small and easily removed can then become large, grumpy tumors that are much more difficult to remove, and can even end the pet’s life. Click here to read the case of one such dog.

So there’s a lot more to making the anesthetic decision than just reflexively saying no because of the fear of anesthesia. Anesthetic risk profiles and hidden risks of conditions not addressed are all things we discuss with any owner considering an anesthetic procedure.