HRS Article:
What's Up, Doc?
by Susan Brown, D.V.M.
PART TWO: TAKING THE FEAR OUT OF RABBIT ANESTHESIA
In part one general anesthetic concepts were discussed. In this column,
we will finish with a discussion of the process your pet will go through
to undergo general anesthesia for a surgical procedure through the recovery
period.
Preanesthetic Evaluation
Every rabbit that is going to undergo an anesthetic or surgical procedure
should have a thorough physical examination performed. There is no exception
to this rule. You would not expect your doctor to put you under anesthesia
unless you had been thoroughly examined and you should not expect less
for your pet. Depending on the type of procedure being suggested and the
age and condition of the rabbit, your veterinarian may suggest certain
diagnostic tests.
The most common tests include any of the following: a complete blood
cell (CBC) count, serum biochemistries, X-rays, ultrasound, ECG and/or
urinalysis. Your veterinarian can explain the reason for the tests in each
case.
*Important: In situations where
owners decline recommended preanesthetic/surgical diagnostics, the risk
factor for the rabbit may increase because the veterinarian cannot acquire
all the needed information to make an informed decision on the suitability
of the patient to undergo anesthesia/surgery.
Treat/Stabilize Existing Disorders
It is important to stabilize or treat any disorder present at the time
of the physical examination, such as dehydration, infections, liver or
kidney disorders, heart or lung disease or breathing difficulties prior
to the administration of the anesthetic. The most common condition that
we see that interferes with anesthesia and surgery is obesity. Obese rabbits
are always considered high risk patients due to the possibility of concurrent
liver disease (fatty liver) and respiratory problems due to the pressure
of excess fat on or in the chest cavity. Unless there is a life-threatening
situation that requires immediate surgery, obese rabbits should always
go through a weight reduction program prior to anesthesia.
*Important: It should be noted
that there are rare situations where a preexisting health condition that
interferes with safe anesthesia/surgery is not detected in a rabbit. As
mentioned previously, we are dealing with complex creatures and all our
tests are not infallible. However, the occurrence of such situations when
a thorough preanesthetic evaluation is done are extremely uncommon.
Anesthetic Induction
Anesthetic induction is the administration of the anesthetic agent(s).
Due to the nature of the rabbit's GI tract and the fact that he cannot
vomit, it is not necessary to fast a rabbit extensively prior to induction.
Some veterinarians prefer to remove the food one to two hours presurgically
to make sure the rabbit's mouth is clear of food. As we previously discussed,
your rabbit may be given preanesthetic drugs prior to receiving general
anesthesia.
The general anesthetic is administered either by injection or by inhalation.
Induction with gas anesthesia can be accomplished via an anesthetic chamber,
a face mask or an endotracheal (ET) tube. The rabbit is maintained under
general inhalation anesthesia with either a face mask or ET tube.
Anesthetic/Surgical General Procedures
Once your rabbit is unconscious, he or she is placed on a warm pad to help
prevent heat loss. In some cases an overhead source of heat is also used.
The mouth is cleaned of any food or excessive saliva if necessary. At this
time if an ET tube is going to used, it is be placed. The head and chest
should be level or slightly elevated to prevent excessive pressure of the
abdominal organs against the diaphragm which could interfere with the ease
of breathing. If an IV catheter was not placed prior to surgery, it will
be placed now that the rabbit is unconscious. Except for short procedures
in healthy animals, it is advisable to have an IV catheter in place in
case emergency drugs need to be given quickly and to administer fluids.
Most rabbits undergoing lengthy surgical procedures will receive IV fluids
to prevent dehydration and replace blood loss. It is preferable that the
fluids be warm, particularly in lengthy procedures, to help maintain normal
body temperature. Emergency drugs should be close at hand. Monitoring devices
are attached.
Anesthetic Monitoring
There are several parameters that are monitored during an anesthetic/surgical
procedure and a variety of monitoring devices that can be used.
Respiration - Respiration can be
monitored visually by an assistant, through a regular or esophageal stethoscope,
by a respiratory monitor (attaches between the ET tube and the anesthetic
machine to measure changes in air flow), or by a pulse oximeter (measures
oxygen saturation of the blood).
Heart Rate/Pulse - The heart rate
or pulse can be monitored by a regular or esophageal stethoscope, an ECG
machine, a Doppler or a pulse oximeter.
Body Temperature - The body temperature
is monitored with a rectal thermometer.
Reflexes - Monitoring the rabbit's
response to certain stimuli helps assess the depth of anesthesia. There
are several ways of doing this, but the most commonly used tests are pinching
the toe and touching the eye. If the toe is pinched and the rabbit tries
to pull its foot away or if the eye is touched and the rabbit tries to
blink, the anesthesia is too light. The rabbit may appear to be unconscious,
but positive reactions to these tests indicates that it can still feel
pain, so the anesthetic will be adjusted accordingly.
Postanesthetic Care
Once the procedure is completed your rabbit will enter the recovery period.
Inhalant anesthesia is discontinued and he or she will receive oxygen for
a few minutes prior to disconnecting the anesthetic machine. The ET tube
is removed as your rabbit starts to show signs of awakening. Reflexes are
checked with increasingly strong responses indicating recovery from anesthesia.
Your rabbit will be moved to a recovery area. It is preferable that this
area be quiet but visible to the veterinary staff who are monitoring the
recovery.
The amount of warmth your rabbit will need during recovery will depend
on his or her body temperature at the end of the procedure. It is important
to watch the amount of warmth used to prevent hyperthermia. Most rabbits
need only a brief period of extra warmth until recovery. Respiration and
heart rate continue to be monitored, usually by direct observation and
stethoscope, until your rabbit is fully awake.
Postanesthetic Care: Analgesia
Although this is primarily a discussion on anesthesia and surgery, we cannot
leave out the important aspect of pain control in the rabbit after a painful
procedure is performed. As mentioned early on, moderate to severe pain
can represent a serious stress to the rabbit and can result in some potentially
dangerous consequences. Many years past when we did not understand the
full significance of pain management in our pets, including rabbits, a
rabbit would often survive a surgical procedure, only to die within the
next 36 hours. The old cliche of "the operation was a success, but the
patient died" would apply to those situations Analgesics may not always
be needed for minor procedures, but should always be used for all major
surgeries.
Some of these cases would most likely have survived if postsurgical
pain had been managed, thereby reducing the stress on the rabbit. You know
that if you have had a painful procedure performed you much prefer
pain-alleviating medications to feeling uncomfortable. Rabbits in pain
recover more slowly than those not in pain. Analgesics may not always be
needed for minor procedures, but should always be used for all major surgeries.
The most common analgesics currently used in rabbits include butorphanol,
buprenorphine and nonsteroidal anti-inflammatory drugs (NSAIDs) such as
banamine, carprofen and ketafen. Aspirin can also be used for mild analgesia.
An alternative source of mild to moderate analgesia for chronic pain relief
is acupuncture or acupressure.
Rabbit Behavior Postanesthesia/Surgery
Your veterinarian should advise you on what specific signs to be aware
of in your rabbit after a anesthetic/surgical procedure. Here are some
general behaviors that might be observed:
*Quiet behavior: Your rabbit may want
to sleep and stay quietly in one area. The lack of activity can be caused
by residual anesthetic in the body, pain, or medication. Some analgesics
have sedative properties and may add to the lethargy. Check with your veterinarian
about what you should expect with any drugs that you are giving to your
rabbit. If your pet is extremely lethargic, is crying out or appears unable
to move normally and sits hunched in one spot, you should contact your
veterinarian immediately.
*Poor appetite - Your rabbit may not eat
or drink at all for the first 24hours after returning home. Analgesics
may improve this situation but not completely eliminate it. You may syringe
feed your pet a thin slurry of ground pellets or blenderized fresh vegetables
mixed with fruit juice once or twice during this period. If your rabbit
still refuses to eat after 24 hours, you should contact your veterinarian
immediately.
*Abnormal or absence of stools - Anesthetic
and analgesic agents can alter the motility of the GI tract. In addition,
the rabbit may have eaten poorly just prior to and just after surgery,
therefore, there may be an absence of stools for a period up to three days
after anesthesia/surgery. If stools are present, they may initially be
smaller than normal, misshapen or soft. This condition should clear up
within three days.
Watery diarrhea should not be present and is cause for immediate concern.
Please contact your veterinarian should you have any questions about your
rabbit''s stools or urine.
Questions to Ask Your Veterinarian
In summary, here are questions that you can ask your veterinarian that
cover the areas of concern regarding anesthetic procedures:
1. Experience level - Ask about the experience level of the veterinarian
regarding rabbits in general and about the procedure in question. Even
though he or she may not have had a lot of experience, based on the answers
to the other questions here and his or her willingness to work with you,
you may decide to go ahead with the procedure.
2. Types of anesthetic agents used - You now have a list of anesthetic
agents that are commonly used. If your veterinarian is using something
else, ask for some type of literature or their experience in using this
drug(s) before making your decision. Remember, some information in this
article will become outdated in time and new drugs will become available
that are not discussed here.
3. Explain the anesthetic/surgical procedure - You are entitled to
know how your pet is going to be handled through the anesthetic/surgical
process. You now have a detailed description of the kinds of things that
should be happening to decrease risk. Analgesics can be given prior to
or during surgery as well as after surgery to make the recovery period
go more smoothly. In particular, find out about preanesthetic evaluation,
anesthetic monitoring, recovery monitoring and use of analgesic agents.
_________
Dr. Brown is co-owner of the Midwest
Bird & Exotic Animal Hospital.