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› articles by michael goldberg, dvm
Anesthesia: What is it and can it be harmful for my dog or cat? The term anesthesia comes from Greek: an- negative, asthesis meaning sensation. Thus, anesthesia means, lack of sensation. It is especially applied to loss of the sensation of pain as it is induced to permit the performance of surgery, or any other painful procedure. It is commonly used in reference to drug-induced behavior although there are other modalities that can induce this state for example through the use of acupuncture. There are a number of different types of anesthetics, which are very broadly characterized, as either local or general. There are also many ways through the use of drugs to achieve both of these types of anesthesia. There are also anesthetics, which paralyze and desensitize regions of the body known as epidural anesthesia or regional blocks, which are infrequently used in small animal veterinary medicine. Local anesthetic is the act of desensitizing very small areas of the body such as the skin or the teeth. The process involves injecting a local anesthetic agent into the tissue, which numbs the area on which the surgery is taking place. The mechanism by which they work is that the nerve impulse, which relays pain form the nerve to the brain is, blocked chemically in which the nerve is temporarily shut down. Epidural anesthesia does this as well except the injection is in the space above the spinal cord and it blocks pain from traveling up to the brain from the spinal cord and thus affects a larger area of the body. General anesthetic on the other hand, is a procedure in which the pet is temporarily put to "sleep" with either an injectable anesthetic, (which are usually administered through intravenous injection), or gas anesthetic, which is inhaled. There are basically three aspects to this procedure; sedation with a pre-anesthetic drug or drugs, induction with an injectable or an inhaled anesthetic (which allows an endotracheal or breathing tube to be placed in the trachea, and then maintenance with either a gas inhaled or injectable intravenous anesthetic. The first aspect, or pre-anesthetic phase, is a sedative, which serves to calm and relax your pet, relieve pain, and to minimize movement in the case of a local anesthetic. It also helps decrease saliva, help the heart beat, and reduces the amount of general anesthetic needed. It also helps "smooth" the recovery from the general anesthetic. The second aspect is to "induce" the pet after which a breathing tube is placed down the trachea to deliver either gas anesthetic or oxygen. The sedatives are usually a combination of two or more drugs consisting of drugs such as Valium, which are tranquilizers, and narcotics such as morphine for pain and calming. These are usually combined with an anticholinergic drug that helps the heart. Induction is accomplished with drugs that are barbiturates, which basically have their action on the brain in which it is depressed into a state of unconsciousness so that the surgery may be performed. They do not posses pain inhibition though. They can have deleterious affects on the heart as well. Other common drugs such as ketamine actually disrupt the brain from the rest of the body and cause a rapid state of "paralysis". This drug can affect the heart as well as it increases the heart rate but is generally very well tolerated by most animals. It should not be used in epileptics. Another injectable anesthetic is propofol, which produces a short acting unconsciousness. It is very heart friendly so it has minimal effect on the heart and thus is a very safe drug to use. It also has no analgesia to it (pain prevention). These drugs act extremely quickly and within a few seconds, they take effect so that your pet will be unconscious. Gas anesthetics are administered through a tube known as an endotracheal tube, which is placed after the pet is unconscious. There are three main gas anesthetics used in veterinary medicine all of which have the ability to induce an unconscious state and as well they confer some analgesia. Halothane is still used and is the oldest of the commonly used gas anesthetics. It is very safe though but it does take longer to bring about unconsciousness than the newer gas anesthetics. Potential side effects are malignant hyperthermia, which occurs rarely, which is a condition in which the body develops an extremely high fever and can result in death. It is metabolized by the liver and can cause liver toxicity. It may also induce heart rhythm abnormalities. Isoflorane is a newer analog of halothane and is generally less toxic overall. It has a much more rapid onset of action and exits the body much quicker. It can be used safely with preexisting liver or kidney disease and has much less of a deleterious effect on the heart muscle. Sevoflurane is a newer anesthetic, which is similar to isoflurane though it is even more rapidly exited from the body. It is taken up much quicker as well which should be cautioned on allowing too much anesthetic for the patient. The advantage is that it is so quickly taken up by the body, that a few quick puffs with a face mask may be all you need to put a pet under anesthetic, which means you may not need other medications for the "induction" phase because you can induce very rapidly with inhaled Sevoflurane. It is very important that prior to having a general anesthetic, that you have your pet fully examined by your veterinarian. It is during a physical examination that certain conditions may be obvious to your veterinarian, which may potentially increase the risks associated with an anesthetic. Certain precautionary diagnostics should be done prior to this procedure such as blood testing as well as x-rays and often an electrocardiogram. I encourage my clients to ask questions regarding the anesthetic and how they are cared for and monitored while they are under anesthetic. There are all sorts of standards across the veterinary field as to monitoring a patient under anesthetic. Some may monitor the blood pressure, while others monitor the heart rate and breathing rate as well as the oxygen levels in the blood during the procedure. Still others may have a continuous electrocardiogram at all times during the anesthetic. You should speak with your veterinarian regarding these monitoring practices. The cost of anesthetic can vary. Some of the drugs are very inexpensive whereas the newer drugs (as a general rule) are more costly reflecting the research and development that goes into them. The cost of the monitoring must also be accounted for and these may reflect the expense or in expense of an anesthetic. With the right anesthetic for your pet, the result should be a safe procedure with minimal pain and rapid recovery. Often there may be a 24 "hangover" period that I account for which I may prescribe homeopathic remedies. There often may be vocalizing upon the recovery of the patient and I find homeopathic remedies often help smooth out this phase of the anesthetic as well. I tend to try to minimize the amount of anesthetics given to my patients over their lifetime. The safety margin for an anesthetic is very good with the correct monitoring and adequate levels of precaution. There is also an excellent Veterinary Anesthesiologist available in the Vancouver area, to monitor any difficult situations. On the whole, anesthetic is a fairly safe procedure. There are certain risks associated with it but usually the outcome is positive if care and caution are exercised. I tend to feel that the fewer anesthetics over a lifetime are optimal for your petıs health. I still find a number of clients though who are quite fearful of the procedure, after all, a part of the family is undergoing a procedure that is not 100% risk free. Read more Articles by Michael Goldberg, DVM... |
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vancouver animal wellness hospital Michael Goldberg, DVM; Sue Hughson, DVM 105 e. broadway, vancouver, bc v5t 1w1 / phone: 604.738.4664 / fax: 604.738.4694 Hours of Operation: Monday, Thursday & Friday: 9am - 6pm, Tuesday & Wednesday: 9am - 7pm, Saturday: 9am - 5pm © Copyright 2004-2006. vancouver animal wellness hospital. All rights reserved. › Contact Us › Privacy Policy › Sitemap › Home |