Your dog is injured, the veterinarian informs you that he or she must be put
under anesthesia to care for the problem. You are concerned and worried. What
goes on before, during and after the anesthesia procedure.
Why does an animal have to be placed under anesthesia? There are two main reasons: to keep them immobile, free of pain and anxiety. Unfortunately most animals will not allow us to perform uncomfortable procedures on them without excessive motion. Due to the pain of some diagnostic and surgical procedures, anesthesia (which means "without feeling") allows the doctor to do what needs to be done in the shortest period of time without discomfort or injury to the patient.
How is anesthesia delivered? As in people, there are different ways to give the anesthesia from intravenous or intra-muscular sedation to general anesthesia. Each has its advantages and disadvantages. Intravenous anesthesia results in a fast induction (time from administration to time the animal is asleep) but does not last long. Some intravenous anesthetics take longer to exit the body because they require metabolism by the liver and kidneys first. Sedatives are often given through the vein muscle. In many cases sedation is sufficient to provide pain relief and motion control for short periods of time without having to use general anesthesia.
Longer procedures (greater than fifteen minutes) usually require general inhalant (gas) anesthesia. The gas is breathed in through a tube placed in the windpipe which is then attached to an anesthetic machine which mixes the vaporized anesthetic with oxygen. The degree of anesthesia (light, medium, heavy) is controlled by the percent of gas mixture. In that the anesthesia is delivered through the lungs and not in the vein, after the procedure is finished the dog simply breaths off the medication and recovers quickly.
The veterinarian considers many factors such as age, procedure performed, and pre-existing conditions in order to choose the best anesthesia for the patient. Isoflufrane is one of the newest and safest type of inhalation anesthetic used in small animal practice. In most cases a pre-anesthetic injection is given to sedate the patient, then the gas is administered with a mask over the dog's muzzle. Once the dog is sleeping an endo-tracheal tube is placed in the windpipe in order to establish a direct route for the anesthetic to be delivered. Many patients control their own level of anesthesia. When they are not deep enough, they will breath harder, inhaling more anesthetic and go back to sleep. If they are too deep the respiration will decrease and breath less gas.
Safety is the veterinarian's most important concern. Prior to anesthetic delivery the K-9 is examined, with particular attention to heart and lung sounds. In older patients diagnostic testing of organ function is often performed first to confirm the patient can safely be anesthetized. The veterinarian should be made aware of any preexisting medical conditions or medication your dog is taking.
The patient under anesthesia is constantly monitored. Observing the color of the gums and the number of respiration's per minute are helpful. Veterinarians now use electrocardiograms, respiratory monitors with alarms, and pulse oximeters (which measure the amount of oxygen inside the patient as well as the heart rate). These instruments add another level of safety to the procedure.
Unfortunately we have all heard of the occasional case that has had problems with anesthesia. When this happens, unrecognized pre-existing conditions are usually uncovered on an autopsy. Occasionally nothing is found.
Anesthesia is an important part of modern veterinary practice and though routine is not taken lightly. If your dog needs anesthesia, many times there are no alternatives. Feel free to discuss your concerns with your veterinarian, and make sure he or she is using the most modern equipment and monitoring devices. Your partner will thank you.