When a pet requires surgery, often the owner’s first concern is the idea of anesthesia. We as veterinarians are very sensitive to your apprehensions and concerns. Although, anesthetic protocols have become considerably safer and much easier to both administer , we are very respectful of these medications. We now have at our fingertips ultra-short anesthetics, totally reversible anesthetics, and very safe and effective gas anesthetics which have dramatically decreased the risk to your pet. Along with the pre-anesthetic testing, anesthetic monitoring, and pain control, anesthetic accidents have been tremendously reduced.
When thinking about your pet and anesthesia, remember that they are not people. Obvious though this might be, it’s important to separate the human experience of anesthesia from what an animal experiences. For instance, humans often awaken from general anesthesia feeling nauseous and with a thumping headache. Recovering pets, on the other hand, are rarely nauseous. And because veterinarians routinely administer pain medication (analgesia) as an important part of general-anesthetic protocol, they usually awake headache free.
Again, while anesthesia is not totally without risk, the risk is mitigated by two factors: today’s exceptionally safe and easily adjusted dosing of the anesthetic drugs and veterinarians experienced in how to anesthetize their patients – from small kittens to feline senior citizens. Also, many of our pets now have pre-anesthetic testing. This also will minimize the risk involved.
While owners tend to think of all anesthesia as general anesthesia, veterinarians administer anesthetic drugs for other purposes, too. For instance, veterinarians routinely inject short- acting anesthetics to immobilize and relax a distressed patient. These may administered intramuscularly, subcutaneously, or intravenously or by inhalation through a mask. There are now a variety of anesthetics to choose from depending upon your pet’s condition.
Your cat’s doctor also relies on anesthesia as an integral part of more advanced diagnostic techniques. As in human medicine, it’s now standard in animal medicine for a veterinarian to use less invasive, nonsurgical approaches to take a peek at what’s going on inside a cat’s body. Endoscopy and biopsy are examples of less invasive diagnostic procedures where anesthetics may assist in the detective work.
General anesthesia has a number of benefits. Some pertain to the patient; others to the doctor. Anesthesia brings about a loss of consciousness in the patient so the patient has no awareness of what is going on and, upon awakening, has no memory of what happened. Anesthesia also blocks any sensation of pain. In addition, anesthesia brings about muscle relaxation and suppression of reflex movement in the patient.
Anesthetic drugs are administered in one of two ways: they can be injected into a vein or muscle or inhaled as a gas. Scientists don’t completely understand how anesthesia works. But they do know that once the drugs enter the bloodstream and travel to specific receptors in the brain, they induce a state of anesthesia. Moreover, once they’re no longer needed, the drugs are quickly expelled from the cat’s body. This speedy expulsion is critical because cats can have difficulty eliminating drugs from their bodies.
A fundamental goal of anesthesia is to use neither more or less anesthetic than necessary to get the job done. The depth of anesthesia required to keep a pet pain free, relaxed, and unconscious depends on the type of procedure and the individual patient. More painful procedures, such as abdominal surgery (spaying or ovariohysterectomy for females) and orthopedic surgery, require deep anesthesia. On the other hand, teeth cleaning requires only light anesthesia. The age and health of a pet also influence anesthetic depth.
It’s very important to plan for general anesthesia. Planning includes a review by your pet’s doctor of the patient’s medical history as well as a physical examination. During this preliminary phase, you and your veterinarian (who is both the surgeon and anesthetist) work as a team. Your pet’s doctor looks to you to provide as full a medical history as you can. (Make sure you mention any previous difficulties with anesthesia.) Depending on the age of your animal, your veterinarian should also recommend tests to check out your pet’s liver, kidney, and heart functions. Knowing the health status enables you vet to put together the proper anesthetic protocol and be on the lookout for any unusual developments during anesthesia and recovery.
The Stages of General Surgery:
Preparation: During this initial stage, the anesthetist sedates the patent and inserts into a front or hind limb an intravenous catheter through which injectable anesthetics and other fluids can pass as needed. This catheter also acts as a gateway for emergency drugs if necessary. Your pet will receive pain medication at this stage to smooth its recovery from surgery.
Induction: The anesthetist takes the patient into the unconscious state by administering injectable or inhalant anesthetics. For animals under 20 pounds, at our practice we use a gas anesthesia, isofluorane, to induce our patients. This procedure give us total control over the stages of anesthesia as well as rapid induction and recovery. Other recent developments are a new generation of injectable anesthetics . One drug allows rapid induction and as soon as the medication is discontinued, rapid recovery. Another injectable anesthetic is totally reversible by administering a follow up medication after your pet’s procedure is performed. Maintenance: Once the patient is unconscious, the anesthetist maintains optimal anesthetic depth. Although for certain shorter, more superficial procedures, injectable anesthetics are sufficient, inhalants offer the anesthetist the advantage of moment-to-moment control, which may be an important consideration for an older or sick pet. During maintenance, the patient inhales anesthetic gases either through a mask over its nose and mouth or via a tube inserted into its windpipe (intubation).
Intubation establishes an unobstructed airway that could be vital should complications arise. (Your veterinarian should consider intubating older or sick pets, and breeds that are subject to breathing difficulties – such as Persians or Pekinese).
To maintain a safe anesthetic state, the anesthetist monitors the depth of anesthesia; the rate and quality of the patient’s pulse and heartbeat; the lungs; the body temperature (to prevent hypothermia); and the mucous membranes (for abnormal color). Many anesthetic monitors are now available to our profession to also assist in monitoring of our patient. These sophisticated devices include heart monitors, instruments to measure your pet’s oxygen and carbon dioxide levels, respiratory rate, and blood pressure. Most animals have a dedicated person whose sole job is to monitor the patient while we, the veterinarian, are treating your pets.
Recovery: A good recovery is an uneventful recovery.
So you see, anesthesia is actually a series of procedures rather than a single event. And certainly, time spent preparing is time well spent. Above all, remember that anesthesia is your cat’s ally in certain times of need.
How Anesthetic Gases Work
1. Anesthetic gases travel to the lungs via a tube inserted into the cat’s windpipe (intubation).
2. The anesthetic moves through the branching structure of the lungs until it can go no further, ending up in an alveolar sac.
3. The anesthetic gas transfers from the lungs to the bloodstream by crossing from an individual alveolus into a neighboring blood vessel (a pulmonary capillary). Once in the bloodstream, the anesthetic travels to special receptors in the brain where it does its “stuff.”
The Young and Old
With appropriate preanesthetic preparation, both the very young to the oldest seniors are acceptable candidates for anesthesia. As pets age, though, they process drugs differently from younger animals, and they especially dislike being away from home. So veterinarians monitor senior very carefully and try to get them home as quickly as possible.
Animals recover best from anesthesia when they’re kept under observation in a warm, quiet, undisturbed environment.