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When your pet is scheduled to undergo a surgical procedure your first thought may be of the risks entailed in anesthesia. This is perfectly natural – the risks of general anesthesia are usually greater than that of the surgery itself. All veterinarians know this and most of us have a great deal of empathy for your concerns. We veterinarians are fortunate in that older, less predictable, anethesthetics have been replaced by compounds that are very predictable and safe when properly used. Injectable anesthetics now each have their specific reversal agents and the gas anesthetics we use are quickly reversed by ventilation. These agents have dramatically reduced risk to your pet. My clients often as me which anesthetic is the safest. The answer is that which ever anesthetic your veterinarian is most familiar using is the safest. Many of the drugs that we use for anesthesia at one dose are sedatives at a lesser dose.
Because pets often become terrified in an animal hospitals, I use general anesthetics more frequently than a human physician would. Procedures such as x-ray, joint examinations and laparoscopy that a human physician would do while you were awake can not be done safely animals without sedation.

Pre-anesthetic Testing:
There are two components of safety in the use of anesthetics. The first is proficiency in their use. To attain this you must select a competent veterinarian. The second component is evaluating anesthetic risk in individual patients. Many times I have forgone anesthesia in a pet when I was dissatisfied with the results of my physical exam. Having worked in the Profession for over forty years I have developed the ability to sense the general health of the animal I am examining. When examination leaves me with uncertainties I schedule a group of biochemical tests to gauge the health of the major organs of the body. Before any major surgery I suggest you have your veterinarian perform B.U.N. and creatinine test to gauge kidney health and ALT, AP, bilirubin, and cholesterol to detect liver problems. Glucose analysis and total blood proteins detect diabetes and debilitating diseases and an EKG may detect heart problems. Include a hematocrit, a differential and total white blood cell count. It is extremely rare for all these tests to be normal in a dog that is a high anesthetic risk. When we know of problems in advance we can make modifications in anesthesia that protect the pet.

Pre-anesthetic administration:
I often give a pre-anesthetic sedation agent such as acepromazine or Valium to pets to calm them down before surgery. Excited dogs often require more anesthetic and may even react differently badly to anesthetic drugs. Once the sedative or tranquilizer has taken effect I shave the patient’s arm and place an intravenous catheter in its recurrent radial vein. This gives me easy access to the pet’s blood stream for fluids and other medications in the event of an emergency.

Selection Of The Proper Anesthetic Agent:
Various anesthetics are administered in one of three ways. They can be injected locally around nerves,injected into the muscle to work systemically or they can be inhaled as a gas. Injected systemic and inhaled anesthetics move through the blood stream to the brain where they render the pet unconscious or insensitive to pain. Anesthetics that are injected near nerves block the sensation of pain distant to the point of injection.

Ideal anesthesia uses neither more or less of the anesthetic than the amount necessary to perform the surgical procedure. I try to give just enough of the drugs to maintain the pet pain-free and relaxed during the procedure. This amount is different for each patient. More painful procedures, such as intra-abdominal surgery, or spaying and orthopedic surgery require more anesthetics than procedures such as teeth cleaning or superficial tumor removal.

Local Anesthetics:

Lidocaine, marcaine and carbocaine are three related compounds that I use to perform local or regional nerve block anesthesia on pets. I use more of these agent than most veterinarians. I do this because they are safer than general gas or injectable systemic anesthetics. When I use them to remove superficial tumors I combine these agents with epinephrine which decreases hemorrhage during surgery. When I use local anesthetics, I tranquilize the pets so they are not terrified during surgery. Although I have read that overdoses with these agents are possible, I have not seen a bad reaction to these agents in the forty years that I have used them. I also use these agents when I perform a cesarean section.

General Anesthetics:
Gas anesthetics cause a deep sleep-like state in animals completely eliminating the sensation of pain. All these agents work directly on the brain. Some that are currently used by veterinarians include sevoflurane, isofluorane and halothane. This group of chemicals are all halogenated (non-flammable) ethers.

Barbiturates such as sodium pentobarbital were used many years ago as general anesthetics in the United States. Although they were powerful anesthetics they were also dangerous because once given they could not be reversed. The only drugs of this class still in use are thiamylal and pentothal which are ultra short acting anesthetics used to place an endotracheal tube in the pet prior to administering maintenance gas anesthetics. Thiamylal is not currently sold in the United States.

Dissociative agents The most common dissociative anesthetics used in veterinary medicine are Ketamine which is approved for use in cats and Telazol which is a combination of tiletamine and the tranquilizer, zolazepam.

Xylazine is an alpha-2-adrenergic agonist sedative with profound pain control properties. Its sedative properties relate to central nervous system depression. Its muscle ­relaxant properties relate to inhibition of the transmission of impulses between nerve cells of the brain. A drug, yohimbine (Yobine) reverses the effects of xylazine almost instantaneously when the procedure is finished. I often use xylazine combined with Telazol in a “cocktail” that improves its safety. For safety, I tend to underdone with this drug. My initial dose of xylazine and Telazol in dogs is 0.2mg of each per pound body weight or 0.002ml/lb of each drug. When necessary, I fine tune respiration and stabilize respiration with another drug, doxapram hydrochloride injection (Dopram).

Medetomidine hydrochloride (Domitor) is an injectable, synthetic a2-adrenoreceptor agonist with strong sedative and pain relief properties. I do not use this drug but those that do say it is an excellent and safe anesthetic. This drug facilitates handling dogs and aid in conducting diagnostic and therapeutic procedures. It is excellent for minor surgical procedures with or without local anesthesia such as dental care when intubation is not required.

Preparing your Pet for General Anesthesia:
There are several things that you as a pet owner can do to help your veterinarian plan for a successful general anesthesia and surgery.

First, if you have fears about your pet’s ability to tolerate anesthesia tell them to your veterinarian a week or so before the scheduled surgery. Most veterinarians will be happy to explain the benefits and risks of anesthesia and other treatment options that may be available. Let the veterinarian know if you have noticed any lethargy, exercise intolerance, weight loss, tendency to bleeding or changes in body functions that may need to be explored. Ask that complete pre-anesthetic blood work be performed on your pet prior to surgery. Be sure to let the veterinarian know if your pet has reacted badly to anesthetics or medications in the past! Dogs and cats are extremely perceptive as to your fears and it is not unusual for them to show psychosomatic illness in response to your worry and concern.

Withhold all food from your pet for at least twelve hours prior to surgery. This is to prevent the pet from vomiting and inhaling stomach contents during surgery. It will also lessen nausea in the pet as he regains consciousness. It is amazing how many pets that I have operated on have had food in their stomachs despite my advice not to feed them. All members of the household need to withhold food from your pet and removing kitchen garbage containers from their reach is also a good idea. I allow pets to drink water up to 4 hours before surgery but veterinarians differ in their advice.

If the pet is not ill, groom and comb it prior to surgery and allow it to relieve itself before entering the hospital.

Many veterinary hospitals do not have twenty-four hour staff to observe your pet after surgery. Rather than have your pet spend the night after surgery alone in the hospital, if you are not squeamish, I suggest you pick the pet up just prior to hospital closing and watch over it yourself that evening. Keep the veterinarian’s emergency phone number or the number of a 24-hour emergency service at hand. Dogs and cats are homebodies who find the familiar odors, sites and sounds of home a powerful incentive to getting well.
You should leave the hospital with a set of discharge instructions. If you have small children at home be careful that they do not bother the pet during its recovery. It is not unusual for dogs and cats to be snappy for a few days subsequent to surgery.

Stages Of Surgical Anesthesia:
Induction is the first stage of anesthesia. Only gas anesthetics require pre-induction medications. Once the animal is induced with a pre-anesthetic or anesthetic compound, I place an endotracheal tube in its windpipe to facilitate breathing and to be sure its airways remain unobstructed. This is especially important in flat-faced breeds such as Persian cats, pekingeses, pugs and bulldogs.

During anesthesia I regulate the depth of the pet by increasing the amount of gas administered through the endotracheal tube or administering more injectable agent. Sick and older pets always require less of the anesthetic agent.

During surgery I constantly monitor the depth of anesthesia by checking the animal’s eye reflexes, pulse strength, heart rate, mucous membrane color and jaw muscle tone. I also place a pulse oxymeter clip on the patient’s tongue to monitor oxygen saturation of the blood.

I monitor the same signs during recovery to be certain it remains uneventful. If I become worried or just want to wake the patient up quickly, I administer a specific antagonist to the anesthetic drug that neutralizes it. Pets are often chilled and shivering as they recover from anesthesia. They really appreciate being wrapping a heated towel fresh from the dryer or being placing on a hot water bottle.

Post Anesthetic Pain Control:
Dogs and cats, like people, are in considerable pain after major surgery. One must balance the desire for pain control with the side effects of all pain control medications. Some dogs tolerate aspirin well. I generally give them 5mg/pound body weight. Cats may accept the same dose given only once every forty-eight hours. Aspirin can cause vomiting and diarrhea. Another danger of aspirin is its ability to decrease clotting of the blood at this dangerous time. A better drug for pain control in both cats and dogs is torbutrol (butorphanol tartrate). I generally give dogs and injection of 0.1-0.2mg/pound body weight and cats 0.1-0.4mg/pound body weight every 6-12 hours. Acetaminophen: 325 mg Oxycodone HCl 5mg (Percocet) is excellent in reducing post-surgical pain in dogs. I administer one tablet per sixty pounds body weight.

There is a common misconception in the United States that gas anesthesia is safer than anesthetics administered by injection. This was true thirty years ago but it is not true with today’s improved injectable agents and specific antagonists (antidotes). When gas anesthetics are administered by an undistracted, experienced technician gas is extremely safe. The realities in a typical veterinary hospital, however, are that distractions are constantly occurring and staff is not always adequately trained or sufficient in number. When this is the case injectable anesthetics given at the bare minimum dose required for the procedure are a much safer alternative.

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