The prospect of anesthesia can be very frightening for the owner of a Sighthound. Veterinarians and owners alike have been warned about the dangers of any kind of anesthesia for Sighthounds and reports of anesthetic deaths are common in the Sighthound community. Unfortunately some conditions such as Cesarean sections, fractured bones, dental disease, and other surgical conditions require anesthesia for proper treatment. Therefore veterinarians and pet owners are frequently faced with the dilemma of whether to treat Sighthounds surgically or to ignore certain health problems.

Fortunately, modern anesthetic agents have given veterinarians the ability to perform anesthesia for a variety of surgical problems with relative safety on Sighthounds. The following discussion will address basic anesthesiology and some of the anesthetic regimens that are suitable for Sighthounds.

Anesthesia is defined as "without pain." In order to perform surgical procedures on animals safely and humanely, an anesthetic agent must be administered. The classes of anesthesia which are available are local, regional, and general anesthetics.

Local anesthesia is provided by injecting lidocaine ("Novocaine") directly into the area which has to be anesthetized. Regional anesthesia injects the anesthetic into a nerve or area around the spinal cord which supplies sensation to the surgical site. Only the pain impulses from the region of the body being anesthetized are blocked. These forms of anesthesia leave the patient conscious and are very safe. Vital signs are not affected.

I recently performed a skin biopsy on a Saluki by using local anesthesia. The area of surgery was injected with the local anesthetic, a small incision was made, and the wound was sutured with little trauma to the patient. Within 30 minutes of entering my hospital, the Saluki and owner went home safe and sound.

The disadvantage of this type of anesthesia is that the doctor is limited to treating minor problems such as suturing lacerations, or removing small skin tumors. The patient is awake and can struggle during the procedure. This can cause the patient to become injured while being restrained. In addition, complications such as excessive hemorrhage can be very difficult to control.

General anesthetics produces a loss of feeling in the entire body and produces a state of unconsciousness. They permit veterinarians to perform complex surgical procedures and have revolutionized the quality of care offered to pets. However, one of the drawbacks of general anesthesia is that there is a risk of a serious adverse reaction to the anesthetic. These include heart, liver, kidney and neurological problems that could ultimately lead to death. Because of two unique anatomic features, Sighthounds can be more sensitive to certain anesthetics than other dogs. Some general anesthetics are unpredictable in Sighthounds and have a prolonged duration of effect. This increases the risk of a complicated recovery. The reason for increased anesthetic sensitivity is the low amount of body fat that Sighthounds possess, and decreased liver metabolism of some anesthetics. Sighthounds have a higher ratio of lean muscle mass to total body fat. Body fat is important in that some anesthetics, such as barbiturates, require redistribution from the blood to the body fat in order for the patient to recover from the anesthetic. Years ago barbiturate anesthetics were the only "safe" anesthetics available for veterinary use. With their use, some Sighthounds were unable to tolerate anesthetic procedures, and had serious complications. This helped spread the myth that Sighthounds could not tolerate any kind of general anesthetic.

Luckily, today there are many anesthetics that are safe for Sighthounds. Veterinarians are able to perform surgery and other medical procedures with safety and confidence. The following discussion will focus on some of the anesthetics which I have used safely in my practice.

In order to anesthetize a dog, a veterinarian must either inject a liquid anesthetic agent into a vein or muscle, or administer an anesthetic gas. In almost all cases, I will initiate anesthesia with a short acting injectable agent and then place an endotracheal tube in the trachea (windpipe) of the dog in order to administer a gas anesthetic and oxygen. This is the safest way to maintain and control the depth of anesthesia. However, using an injectable anesthetic as the sole anesthetic agent is appropriate only for short procedures.

Various injectable anesthetics are available. As discussed, barbiturates, which are injectable anesthetics are more risky in Sighthounds because of their body fat content and liver metabolism. In my practice, barbiturates are never used. Instead, I have successfully used three separate injectable anesthetic regimens and a gas anesthetic.

In order to produce a smooth transition from the awake to the anesthetic state, it is best to give a preanesthetic medication. These drugs reduce patient fear and stress, and allow the anesthetic drugs to take affect in a gradual and predictable manner. Additional benefits of some preanesthetic drugs is the reduction of postoperative pain.

Butorphanol, an opioid analgesic, is an excellent preanesthetic for Sighthounds. Given intravenously or intramuscularly before anesthesia, it will help ensure that the patient becomes anesthetized smoothly. Butorphanol is a medication that will reduce post operative pain.

Once a patient receives its preanesthetic, the injectable anesthetic agent can be administered. For over ten years, I have used a combination of ketamine and diazepam (Valium) as an injectable anesthetic. Ketamine is a dissociative anesthetic and valium is a tranquilizer. Used together, they provide rapid, smooth anesthesia, with minimum depression of cardiac function. It will induce fewer irregular heartbeats than barbiturates, and can be used in patients with cardiovascular disease.[2] Because of its cardiovascular sparing affects, this anesthetic combination can be used in critically ill pets.[3] It is relatively easy to place an endotracheal tube in the dog's trachea once they are anesthetized.

Recovery from anesthesia is dependent on liver conversion to inactive substances and direct excretion by the kidneys. Sighthounds and other breeds appear to react alike to this anesthetic combination.

A disadvantage of this drug combination is that young dogs tend to be anesthetized less deeply than older dogs when the recommended dosage is given. Once gas anesthesia is administered, it takes longer for the dogs to achieve the proper surgical anesthetic plane.

Ketamine and diazepam can induce seizures in dogs and should not be used in patients with epilepsy. It should not be used in patients with liver or kidney disease.

Another anesthetic combination used in Sighthounds is oxymorphone and diazepam. Oxymorphone is a narcotic analgesic, and when used with diazepam, produces a state of sedation and analgesia that permits the veterinarian to perform minor procedures, or place an endotracheal tube for the administration of gas anesthetics. It should be noted that if this drug combination is used, the preanesthetic butorphanol should not be used, because it is in the same drug class as oxymorphone.

One advantage of using oxymorphone is the ability to reverse its affects by administering naloxone, a narcotic reversal agent. Dogs will wake up within minutes of receiving the proper intravenous dosage of naloxone. This gives the veterinarian the ability to halt anesthesia if a dog is having an adverse reaction.

Although cardiovascular changes are minimal during anesthesia, respiratory depression may occur. Dogs can stop breathing for a period of time, and the veterinarian must be prepared to provide respiratory support if this happens. When using oxymorphone and diazepam, some dogs will react to loud noises in the operating room. It is helpful to administer this anesthetic combination in a quiet atmosphere.

Oxymorphone and diazepam is suitable for most patients except those with severely compromised liver function. These patients tend recover slowly.[7]

The most recent injectable anesthetic used successfully in my practice is propofol. It is considered a safe anesthetic in Sighthounds.[6] Propofol has many characteristics that make it ideal for use in veterinary practice. Its use creates smooth, excitement free anesthesia, and its effects are very predictable.[6]

Recovery is rapid and smooth. Termination of propofol's effect has been attributed to the redistribution of the drug to muscles and fat, and to metabolism in the liver. The primary difference between propofol and barbiturates is due to propofol's rapid clearance in the liver.[1] Sighthounds will wake up more slowly than other breeds, but propofol is still considered a good choice.

When using propofol, the most remarkable aspect is how quickly the patient becomes anesthetized and how quickly the patient wakes up after the procedure is finished. It is very easy to place an endotracheal tube, and propofol works well with gas anesthetics.

One disadvantage of propofol is the development of respiratory depression when administered; dogs could stop breathing for several minutes. This may be avoided by injecting propofol slowly until the desired effect is obtained. Equipment for assisted ventilation should be available when propofol is used. Also, propofol should be used with caution in dogs that have cardiovascular disease.[5]

Inhalant anesthesia, also known as "gas," offers many advantages over injectable anesthesia. These include the ability to control the depth of anesthesia, the ability to provide a high concentration of oxygen during the anesthetic period, and minimal cardiovascular and respiratory depression.[9] Most of the inhalant anesthetic is removed from the body by exhalation and Sighthounds appear to utilize and remove inhalant anesthetics similar to other dogs.

Inhalant anesthetics can be used to induce anesthesia by placing a facemask over the patient's nose and mouth. After anesthesia is achieved, an endotracheal tube is placed. In my practice, I never use an inhalant anesthetic to induce anesthesia because of the risks of chronic exposure to humans. Instead, I use the injectable anesthetics described above to induce the anesthesia and the inhalant anesthetic delivered with an endotracheal tube to maintain anesthesia. This method allows me to safely anesthetize Sighthounds with minimal risk to my staff.

There are several types of inhalant anesthetics available. The inhalant anesthetic used exclusively in my practice is isoflorane. This is considered the safest of all of the veterinary inhalant anesthetics because the patients reach a surgical anesthetic level faster, and tend to exhale it out faster, than other inhalant anesthetics. This means better anesthetic control for the veterinarian and safer anesthesia for the patient. Isoflorane is eliminated from the body mostly by respiration. Unlike other inhalant anesthetics, which can damage the liver or kidney when eliminated, isoflorane is particularly safe for the patient. Isoflorane can reduce cardiac function if too much is given, but it does not sensitize the heart to irregular rhythms.[8]

I have discussed some of the anesthetic regimens used successfully in my practice. Used judiciously, with careful preoperative testing and monitoring in the operating room, anesthesia can be as safe in sighthounds as other breeds. Anesthesia is stressful for the patient, owner, and veterinarian. However, the anesthetics available today allow Sighthounds to be anesthetized safely, and permit veterinarians to perform complex surgical procedures. Hopefully this report will help make Sighthound owners more confident and at ease when anesthesia is required. In the future, research will develop even safer and more sophisticated anesthetic agents. Ultimately Sighthounds will live longer and healthier lives because of the advances in veterinary anesthesia.

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