Hi Nore,
Shih-tzu's do not really have any specific anesthetic concerns
compared to other breeds of dog, apart from having the typical
"squashed face" which can cause breathing difficulties. Shih-tzu's,
along with bulldogs, pugs and other squashed faced breeds should
always be intubated during anesthesia, Their elongated soft palette
can cause breathing difficulties during heavy sedation.
Xyalizine is sold under the brand name "Rompun" for use in animals, it
is not routinely used alone as it has only heavy sedation properties.
It is not considered appropriate to use alone for surgical procedures
and is often mixed with a dis-associative drug like ketamine. Used in
this combination it is suitable to bring the dog under anesthesia,
making it possible to intubate and place on gaseous anesthetic.
Standard pre anesthetic monitoring includes a full blood screening to
ensure that basic organ function is normal. This is especially true of
the liver and kidneys as good kidney function is required for the body
to expel the drug over a period of about 72 hours. Impaired kidney
function may cause renal failure when combined with a drug like
Rompun. Heart and lung function would also be checked to ensure no
cardiac problems were present and that lungs were functioning
normally. Whilst heart and lungs problems are not specifically a
concern with Rompun, placing an animal with heart or lung conditions
under heavy sedation can be very dangerous.
Pre-anesthetic blood screening is usually only performed in older dogs
or dogs with a known condition. However most clinics will perform
screening at the request of the owner, heart and lung function are
always checked before any sedation is administered.
Rompun will also induce vomiting which can be a problem when the dog
is heavily sedated, animals under very heavy sedation loose their
swallowing reflex and vomit can be inhaled into the lungs resulting in
aspiration pneumonia. Dogs should be fasted for 12 hours prior to
being sedated with xyalzine.
During administration, care must be taken not to overdose the drug.
Rompun is often given "to effect" meaning that it is slowly
administered until the dog reaches a satisfactory level of sedation.
The drug should be injected very slowly and intravenously if possible
to ensure a rapid effect. The dog should be restrained adequately to
avoid complications.
During anesthetic, the dog should be monitored for regular breathing,
a "pulse-oximeter" is often used which monitors the amount of free
oxygen in the blood and also the animals heart rate.
If the animal has not been intubated, great care must be taken to
ensure that vomiting does not occur during sedation.
During recovery (usually around 30 minutes if no other agent was used
and a reverser was not administered), the dog must be placed in a
quiet, well padded area. Dogs awaking from sedation will often throw
themselves around and can be especially sensitive to sudden noises. If
the dog has been intubated the tube should not be removed until the
dog has begun to swallow normally again. If the dog has not been
intubated then it should be placed so that the shoulder is higher than
the head and should be monitored closely incase of vomiting. The dog
should be back to normal within 2-5 hours but food should probably be
withheld for around 12 hours following the sedation, vomiting may
occur during this time as the drug is still active in the body.
All traces of the xylazine should be absent from the dog after 72
hours.
I hope this is the information you required, if there is anything more
specific you require please let me know and I can reference some of
the drug text books next week.
Molloch
** Note: This answer was written from my personal experience as a
veterinary nurse over the past 8 years at a very busy animal hospital
(20-30 surgical cases each day). This answer was written from personal
notes collected during this time and from discussions with
veterinarians at the hospital. Following are some links to sites with
more information on this topic which may or may not have been used to
write this answer. The above is not medical advice and the opinion of
your veterinarian should be taken above anything written here. If
something you believe conflicts with your veterinarians opinion, seek
a second opinion for a qualified veterinarian.
This site contains specific chemical action of may sedatives,
including xylazine.
http://lam.vet.uga.edu/LAM/LM000019.HTML
South-Paws Pet Anesthetic page.
http://www.southpaws.com/topics/anesthesia.htm
Long Beach Animal Hospital.
Blood test information with a good section on pre-anesthetic
screening.
http://www.lbah.com/PreA.htm
Dental Vet.
This page gives information about monitoring equipment used with
anesthetics.
http://www.dentalvet.com/patients/anesthesia/anesthesia_and_your_pet.htm
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