AN ANESTHETIC
PRIMER FOR THE BELGIAN OWNER
LIBBYE MILLER DVM
Having your beloved Belgian go under anesthesia can be a nerve-wracking
experience. Understanding exactly what will take place and what questions to
ask may help ensure your dog’s safety and your peace of mind.
What questions should be asked before you agree to anesthesia?
1. Is anesthesia really necessary for this procedure? Look for a veterinarian
who is willing to work with you on this. Some procedures CAN be done in the
awake patient. With a local anesthetic, some wounds can be sutured, a skin
biopsy taken, small tumors removed. OFA films can be done in awake dogs, but
the dog must be cooperative enough to lie on his back with his hind legs
stretched all the way out and rotated in. And he must be STILL. Some dogs just
won't go for this without sedation.
2. What kind of pre-anesthetic screening is done? At a minimum, in a healthy
young dog, a physical exam should be done, along with a history of the dog's
general health, recent medications, drug allergies, vaccinations and any recent
insecticide exposure. Depending on the dog's age and history, blood work may be
necessary before anesthesia.
3. Have you done anesthesia on Belgians before? While there is no definitive
proof that Belgians as a breed are more sensitive to anesthesia, there is
certainly enough anecdotal evidence to make us very cautious. Belgians, as a
breed, tend to be lean, active dogs with little body fat. This combination of
traits may make them susceptible to relative overdoses, if the anesthetic is
given strictly by body weight or given too quickly without letting the dog
settle down. In other words, a thin dog that will fight going under, may need a
lower dose than he seems to!
4. What kind of anesthetic will be used? There are many different drugs that
may be safely used for anesthesia, and the selection is subject to each
individual veterinarian’s experiences and preferences.
COMMONLY-USED DRUGS
Keeping in mind that new, better drugs are coming along all the time, here is a
list of some of the drugs that are commonly used in the average practice.
ATROPINE (or GLYCOPYRROLATE)
These drugs are used as pre-anesthetics to prevent the heart from slowing down
during anesthesia and to dry up the excess saliva that sometimes results with
anesthesia. Atropine should not be given to an animal with signs of congestive
heart failure.
ACEPROMAZINE
Commonly called ACE, this drug is often used in pill form for dogs that have
storm anxiety or car sickness. It is used as a pre-anesthetic to sedate the
patient, control nausea, and to protect against some heart arrhythmia. Ace
dilates the blood vessels so it may lead to lowered body temperatures which
slow recovery. This drug also lowers the blood pressure and the seizure threshold.
THIS DRUG SHOULD NOT BE USED IN EPILEPTICS OR PATIENTS IN SHOCK.
It has been suggested that the manufacturer's dose be reduced by 50% or more
when used as a pre-anesthetic. It should also be used with extreme caution in
older dogs, neonates and dogs with liver problems.
Belgians seem to be particularly sensitive to the effects of Acepromazine. I get more calls about problems with this
drug than any other. When given just a drop of Acepromazine
with their preanesthetic meds, some Belgians are still unable to stand 18 hours
later and require IV fluids to get them back up and going. I’d avoid this drug
if at all possible and do not use it for any dogs in my practice except in the
oral form.
BARBITURATES (Pentobarbital, Nembutal, Thiopental,
Pentothal, Thiamylal, Biotal,
Surital, Brevital).
These drugs are given intravenously to allow intubation.
During intubation, a tube is inserted into the
windpipe so that the patient is ensured of a clear airway. Oxygen and
anesthetic gas are then given through the tube. Respiratory depression can be a
problem with this class of drugs, the dog may even
stop breathing on its own when they are first administered. It is CRUCIAL that
dogs on this kind of anesthesia have an endotracheal tube in and be on oxygen,
so that they can be ventilated if need be.
Barbiturates may also cause a decline in heart function and blood pressure
immediately after injection. They can also cause irregular heartbeats and even
cardiac arrest, especially if the patient is stressed or excited. If these
drugs accidentally get outside the vein during injection, they can cause tissue
damage.
Animals awaken from barbiturate anesthesia when the drug leaves the brain and
disperses into the body fat. Over time, the drug exits the body by way of the liver
and kidneys. So thin animals, and those with liver or kidney problems, may have
prolonged recoveries. Sight hounds have a proven increased sensitivity to these
drugs, because they are very low in body fat and their livers have some
problems processing barbiturates. I, personally, don't use Barbiturates
anymore.
DOMITOR (Medetomidine)
Domitor is a
sedative analgesic drug which is useful for short procedures like taking X-rays
or minor surgery. It should not be used in patients with heart, liver, or kidney
disease nor in dogs that are very debilitated or in
shock. It always doesn’t work well (sometimes not at all!) in dogs that are very stressed or agitated. It
works best if you give it and then put the dog in a quiet, dark place to get
sleepy.
Adverse effects can include slow heart rate and breathing, excitation
rather than sedation, vomiting, and recurrence of sedation after recovery.
While it can be given intravenously, I prefer to use the intramuscular
route only. The big advantage of this drug is that it can be reversed with Antisedan so that when the procedure is done the dog can be
up and near normal in a very short time. I’ve used this drug for quite a few
Belgians and it has worked well for doing OFA films.
ISOFLURANE
This gas anesthetic is commonly used today, and although it is expensive, its
wide margin of safety compared to the older Metophane
and Halothane, make it the drug of choice for most
patients. Because 99% of Isoflurane leaves the body through breathing, animals
begin to wake up almost as soon as the gas is turned off. Isoflurane doesn't
depress the heart and doesn't have to be stored in the fat or processed by the
liver or kidneys.
Geriatric or ill patients can be masked down with Isoflurane in minutes, then
intubated and maintained on Iso during surgery. Animals usually begin to wake
in 1-2 minutes once the isoflurane is turned off. It may be difficult to find a
mask that fits the long, pointy Belgian face!
KETAMINE (KETASET) Ketamine has a wide margin of safety when used
for anesthesia. Given along with Valium, Ketamine gives a quick, smooth
induction in about 1 minute. Ketamine does not depress the heart rate, and
while some animals seem to hold their breath, their oxygen levels usually
remain adequate.
KETAMINE SHOULD NOT BE USED IN EPILEPTIC DOGS.
Rough recoveries with thrashing and screaming can sometimes be a problem with
Ketamine, so patients should be carefully monitored. This excitement generally
lasts only a few minutes. Recovery from Ketamine and Valium anesthesia usually
occurs in 2-6 hours in young, healthy animals.
PROPOFOL (Rapinovet):
This sedative-hypnotic drug has now become the “drug of choice” in many
practices. Propofol can be used alone for short procedures or as an induction
agent before gas anesthesia. A single dose last only about 5 to 7 minutes as
this drug is rapidly eliminated from the body. It does not accumulate in the
tissues so it is safe to repeat doses. Animals generally recover smoothly and
are normal very quickly without evidence of a “drug hangover”. Propofol’s rapid
elimination makes it safe even for animals with liver disease. It can be used
without fear of triggering seizures in epileptic patients.
Propofol can depress heart function and breathing, though it does not
cause cardiac arrhythmia. And endotracheal tube should be in place in case
ventilation is needed. If given too rapidly or at too high a dose this drug can
cause respiratory arrest. There has been a study showing prolonged recoveries
in Greyhounds (47 minutes as opposed to 7 minutes in mixed breeds) but I have
not seen this reported in Belgians.
SERVOFLURANE
This inhalation anesthetic is very similar to Isoflurane. It is quickly
expelled from the body just by breathing so it’s very safe, even for elderly or
ill animals. Recovery times are reportedly even quicker than those with Isoflurane.
VALIUM (Diazepam)
This drug is usually used together with Ketamine. Valium calms the
patients, helps prevent seizures, and relaxes the skeletal muscles. Valium is
one of the safest of preanesthetics, and while it must be used with caution in
patients with liver problems, it is very useful for anesthesia in the elderly
or high-risk patient.
XYLAZINE (Rompun)
Xylazine is a potent sedative and muscle relaxer. It is also associated
with a "higher incidence of anesthetic complications and death than any
other commonly used preanesthetic" (1) It is often combined with Ketamine for
general anesthesia.
The advantage to Rompun is that it can be given in the muscle, and
occasionally, a patient is so intractable that hitting a vein or masking down
is not an option. Also, the drug Yohimbine can be given to reverse the effects
of Rompun.
Rompun slows the heart and may cause irregular heartbeats and low blood
pressure. It may cause greatly depressed breathing, gastric bloating, and
vomiting, prolonged deep sleep. This drug should not be used in dogs with
heart, lung, liver or kidney problems, and I have serious reservations about
its use in any patient. EVER.
So how can you do your best to insure a safe anesthetic for you Belgian?
Look for a veterinarian who is willing to do procedures without anesthesia if
possible and who does appropriate pre-anesthetic screening. While it may prove
difficult to find a veterinarian who has much experience with Belgians, look
for someone who will listen seriously to your concerns and tell them that
Belgians seem to handle
anesthesia much like sight hounds.
As far as which anesthetic is used, each patient must be evaluated individually.
In my experience, (22 years) the safest way to induce anesthesia for the
majority of patients is to give Valium and Ketamine intravenously, intubate the
dog, and maintain it on Isoflurane. An alternative, especially for the sick or
elderly patient, is to mask the dog down with Isoflurane, and then intubate and
maintain on Iso.
I've used the Valium, Ketamine, Isoflurane combination on my own Belgians, my
elderly, diabetic Sheltie who has kidney failure, on a 14 year old who had
heart failure, kidney failure and a huge infected uterus--in fact, I use this
combination of anesthetic for 99% of the procedures I do.
Anesthesia is a state of controlled and reversible unconsciousness, and while
nothing can make it 100% safe for every patient, you and your veterinarian can
work together to make it the safest experience possible.