How Safe Is Anesthesia?

by Ron Mandsager, D.V.M.
© 1996 by Ron Mandsager and Cindy Tittle Moore
Reprinted with permission

"How safe is it to put my dog under anesthesia?" "My friend's uncle's neighbor's dog died when they put her under to spay her, so now I don't want to spay my dog!" "I've heard of dogs dying when being anesthetized for hip xrays." "My dog has to be anesthesized . . . what can I do to make sure it's as safe as possible for her?"

I consider myself qualified to address this subject, since I am a Veterinarian, a board-certified Veterinary Anesthesiologist (Diplomate, American College of Veterinary Anesthesiologists -DACVA), and an Assistant Professor of Veterinary Anesthesiology at Oklahoma State University's College of Veterinary Medicine.

First, anesthetics mishaps happen. The incidence is low, although we do not have a comprehensive morbidity/mortality report for general anesthesia in veterinary medicine. I would roughly estimate an average risk for deaths directly attributable to anesthesia in veterinary medicine to be in the order of 1:1,000 to 1:5,000 anesthetics. However, many factors come into play when considering the risk of anesthesia in your particular animal:

1. Any pre-existing conditions. A young, healthy dog is obviously a better anesthetic risk than a dog with liver disease, heart disease, kidney disease, etc. Prior to any anesthetic episode, your veterinarian should perform a physical examination, and depending on the age and condition of your animal, may perform a variety of pre-anesthetic evaluations, including but not limited to, a complete blood count, biochemical screen, thoracic radiographs, and an electrocardiogram.

2. Type of anesthetic used. A number of different anesthetics are available in veterinary medicine, and not one of them is the "perfect" anesthetic. They all have strengths and weaknesses. It is the job of your veterinarian to evaluate the condition of your animal as mentioned above, and then select the appropriate anesthetic protocol for that animal and the procedure that is to be performed. The degree of expertise that your veterinarian has in performing this task will definitely affect the outcome of the case.

3. The amount of anesthetic monitoring performed during the anesthetic episode. A variety of monitoring devices are available in veterinary medicine, but first and foremost is the use of our senses in evaluating the condition of the patient while under anesthesia. Examination of mucous membrane color, palpation of pulses, auscultation of heart and breath sounds, and evaluation of anesthetic depth should be performed on a regular basis throughout the anesthetic period.

Here at OSU, this is done at least every 5 minutes, and the results recorded on the anesthetic record. In addition, mechanical monitoring devices are available to aid in this task. We use an ECG and non-invasive blood pressure monitor on almost all patients. In addition, we have pulse oximeters (measures the oxeganation of the arterial blood) that we use on many patients.

4. The level of physiological support provided the patient during the perianesthetic period. Almost all of our patients have an intravenous catheter placed, intravenous fluids are administered throughout the anesthetic period, the patient is endotracheally intubated, and they breath an enriched oxygen mixture throughout the anesthetic period. Ventilatory support is given as needed. They are placed on warm water heating blankets in an attempt to minimize hypothermia while under anesthesia.

5. Duration of the anesthetic episode. Most healthy animals can tolerate some degree of physiologic compromise for a short period of time (minutes) with little ill effect; however, if that same level of physiologic compromise persists for a long period (hours), serious ill effects may develop. This does depend on the condition of the patient, however. Ten minutes of moderate hypotension in a young healthy dog will not bother it, but ten minutes of moderate hypotension in an elderly dog with heart disease, renal disease, and liver disease may be devastating.

Most of our anesthetic procedures at our teaching hospital take a fairly long time; most anesthetic procedures done at your local veterinarian are probably much shorter. This is due in large part to the teaching mission of our hospital, and the involvement of students in the process, but is also due to the complexity of the cases we see and the complexity of the procedures we perform.

Anesthesia is a necessary evil. We use more anesthesia than would be necessary for human patients, because we cannot talk our patients into cooperating with us for many of our procedures. On the other hand, modern anesthesia practice is in large part responsible for our ability to offer a wide range of diagnostic and therapeutic procedures. Modern surgery was not developed until a safe and effective method of anesthetizing surgical patients was developed. We are constantly fine-tuning anesthetic practice, and gradually developing better and safer methods of providing anesthesia. It is the obligation of your veterinarian to stay abreast of these changes in anesthesia, and provide you with reasonably up-to-date anesthetic case management.

It is your obligation then to pay for these changes and improvements in anesthetic practice. It costs your veterinarian money to provide technical support for frequent anesthetic monitoring, it costs your veterinarian money to provide the newer anesthetic monitors available (we often have $5,000 to $8,000 worth of monitors attached to our patients), it costs your veterinarian money to provide up-to-date anesthetic machines (basic models cost $3,000 to $5,000), and the newest anesthetic drugs are also the most expensive. We routinely discharge patients with anesthetic bills alone ranging from $50 to $150. Are you willing to pay? If so, tell your veterinarian! One strong criticism I have of veterinarians in general, and I am guilty of it also, is that we often decide for you what we think you are willing to pay, and then adjust the quality of our practice to fit our preconceived notion. Are you willing to pay more for higher quality anesthesia? Are you willing to pay for more intensive monitoring? Are you willing to pay for the latest anesthetics? Tell your veterinarian.

At a meeting I was at another night, I spent some time discussing propofol, a newer intravenous anesthetic with some very nice properties. It costs me $20 in drug costs alone to induce anesthesia in my 40 kg male Labrador with this drug. A veterinarian came up to me after the meeting and said, "It's too expensive, my clients won't pay for it." He won't even give his clients a chance to say "Yes, I will pay for it!"

Regarding discussion of people's unfortunate experience with anesthesia in their animals-don't paint "anesthesia" with too broad a brush. Why was the animal anesthetized? What pre-existing conditions were present, if any? How thoroughly was the animal evaluated prior to anesthesia? What anesthetics were used? How was the animal supported during anesthesia? What level of monitoring was performed during anesthesia? These are all important questions that may give insight into why the animal died and what perhaps could have been done differently. However, sometimes bad things happen regardless of the best care given. We do have animals that react unexpectedly to anesthetic agents-allergic reactions can occur (anaphylaxis), or an animal may be just more sensitive to the effects of a given anesthetic. The ability of the veterinarian to react to these untoward events in a rapid and efficient manner may save the animal-but not always.

DISCLAIMER: One of our concerns in writing a column like this is that we are not seeing the animal, and what we get from folks in ASCII isn't always going to be the whole story. So we cannot provide diagnoses, or really tell you to ignore or treat a given problem. We hope the information provided guides you in making good health care decisions for your pets.

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