Anesthesia

by Doreen Kent

Pet owners should always be concerned about the risks of anesthesia and should ask their veterinarians what steps they take to ensure that risks are kept to a minimum.
DON’T BE AFRAID TO ASK QUESTIONS AND THOROUGHLY DISCUSS WITH YOUR VET BEFORE GOING AHEAD WITH ANY PROCEDURE REQUIRING ANESTHESIA.

WHAT A PET OWNER CAN DO

Planned surgery – spaying, neutering, hip and elbow x-rays, cleaning and repairing damaged teeth, removal of growths

Your pet should be up-to-date on all his/her vaccinations – distemper, hepatitis, parvo, rabies
Your pet should have been tested for heartworm and have been on the prevention program
Your pet should be free of all internal and external parasites
Age and health should be taken into consideration when planning a surgical procedure.
Sometimes it’s best to leave a lump alone on an elderly pet. Discuss this with your vet rather than assuming that surgery is the best option.
A thorough examination of your pet by your veterinarian should be done prior to any surgery. Depending upon known or suspected medical problems or physical examination findings, some or a complete blood work-up, x-rays, and/or an electro-cardiogram may be recommended or essential. Liver enzymes and kidney values testing can be performed in most clinics in a matter of minutes with just a few drops of blood. Discuss all pre-op work-up options with your veterinarian and always opt on the side of caution.
Any growth should be brought to the attention of your veterinarian right away. Rapid increase in the size of a growth may be an urgent warning signal – seek attention immediately.
Mention to your vet all the medications your dog is taking and if your dog has been wearing a flea collar or has recently been dipped for fleas and ticks. Be specific about the products used and their ingredients. Mention any unusual behavior or change in routine.
EXTREMELY IMPORTANT - mention any seizure occurrences and any medication your dog is taking for seizures.
Try to combine procedures; i.e., spaying and teeth cleaning and perhaps the removal of a wart, mole or growth. Consult with your veterinarian about how much would be safe to do in one operation. Keeping a dog under anesthesia for a longer period of time to accomplish a number of procedures may not be a good option.
Removal of mast cell tumors in conjunction with any invasive procedure IS NOT RECOMMENDED due to possible internal post-operative bleeding.
If your dog has very little body fat or a great deal, discuss with your vet that barbiturates should not be used.
Scrupulously follow directions given to you by your veterinarian for pre and post-operative care.
Emergency surgery – since a number of emergency surgeries are handled by emergency clinics that do not have a case history of your dog, you have to make certain that you give them as much medical history and information on your pet as possible.
Always have your pet up-to-date on his/her vaccinations, free of internal and external parasites and on heartworm prevention.
Prior to any emergency surgery, advise your vet of what medications your pet is on and when they were last given and what your pet has eaten, how much and when last fed. EXTREMELY IMPORTANT - Mention any seizure occurrences.
Discuss with your vet that the use of barbiturates may not be an option with Ridgebacks.

TYPES OF ANESTHETICS

LOCAL -These are either topical or injectable and are used to diminish or eliminate pain sensation by interfering locally with nerve conduction and transmission of pain signals to the brain. A local will not render an animal motion-free. This would be an option to repair minor lacerations in good-natured, cooperative dogs. It is also an option to provide temporary pain relief to seriously injured animals who are not stable enough for general anesthesia to repair the problem.

REGIONAL - Involves injecting local anesthetic agents into or around nerves that provide pain sensation to an entire region. For example, blocking the brachial plexus with injections renders the front leg below the elbow pain-free. Again, it does not aid in restraint of the animal.

EPIDURAL - Another type of regional anesthesia accomplished by injecting an analgesic such as morphine into the space surrounding the spinal cord to deaden sensation to a region of the body. This procedure is usually not practiced in veterinary medicine except in university veterinary centers and critical care centers.

INJECTABLE - Excellent choice for short procedures not involving entering a body cavity as they do not provide sufficient pain relief.

INHALANT - Most common form of anesthesia used for prolonged and invasive procedures. Very safe drugs available today; i.e., sevoflurane. Isoflurane is also a safe inhalant anesthesia; however, sevoflurane is the newest. As it is necessary to insert an endo-tracheal tube so the animal can inhale the gas, an injectable anesthetic is needed to render the animal unconscious and not fight the insertion of the tube. Propofal is the drug of choice. Puppies and small breeds, however, can be anesthetized using an anesthetic mask or induction chamber.

ANESTHESIA PROCEDURE

PRE-OPERATIVE - Usually, sedatives, tranquilizers, analgesics (pain reducers), and medication to reduce salivation.

Sedatives – Acepromazine – can cause low blood pressure

INDUCTION AGENTS - Injections to induce anesthesia to a level where an endo-tracheal tube can be inserted. Barbiturates such as Thiamylal and Thiopental should be used with caution in any sighthound. Barbiturates are redistributed into the body fat. In the case of a Ridgeback that is in top notch lure coursing condition with very little body fat, the use of barbiturates should be avoided. The same would hold true for a Ridgeback that is overweight with a lot of body fat. However, most veterinary practices are opting for combination drugs such as Ketamine, Valium or Ketamine and Medetomidine. Propofal is an extremely safe induction agent. It is eliminated quickly and used extensively in Greyhound and other sighthound surgeries. It is much more expensive than other induction anesthetics.

MAINTENANCE - Accomplished by inhalant anesthetics such as Halothane, Methoxyflurane, Isoflurane and the newest - Sevoflurane. These gases are used to maintain the anesthesia throughout the operation. Additional administration of injectable anesthetics is not recommended, with the exception of Propofal. IV fluid therapy is recommended for any invasive or extended procedure in order to maintain blood pressure, decrease the risk of shock, and have a line open to the bloodstream in the event of an emergency.

Involves constant administration of inhalant gas to maintain the needed level of anesthesia. A good anesthetist will constantly monitor mucous membrane color, heart and pulse rate, pulse quality, respiratory rate and depth, and eye reflexes.

Electrocardiogram gives instantaneous visual and audio picture of the heart rate during a procedure.
Blood pressure monitoring equipment is not commonly available in regular veterinary practices. Most anesthetics can cause low blood pressure. Monitoring enables the veterinarian to intervene when needed. Doppler is an inexpensive alternative to expensive blood pressure monitoring equipment.
Pulse oximetry is becoming more available in veterinary practices. Measures oxygen in the peripheral blood vessels. An excellent means of determining whether an animal is breathing sufficiently to provide oxygen to the blood.

POST-OPERATIVE - With the use of the new and safer anesthetics, animals are coming out of anesthesia quicker, and post-operative pain may be more intense. Therefore, the use of post-operative pain relievers and the continuation of IV fluid therapy is highly recommended. . A growing number of veterinarians are using duragesic patches for post-operative pain. However, they are recommend for only the most painful of post-operative procedures such as orthopedic surgery. There is considerable sedation with them, some constipation, decreased appetite, and gastrointestinal stasis. Torbutrol is a good oral pain reliever for the first 24 – 48 hours after surgery. It should not be administered, however, unless the dog is exhibiting signs of pain and discomfort.

NOTE: This article has been reviewed by three licensed veterinarians for input and accuracy and has been reviewed and accepted by several more since publication.