To the FML:
Let's put this topic to bed.  I have always recommended the use of
isoflurane only in ferrets as the safest way to perform anesthesia.  There
are a number of reasons for this:
 
1) Isoflurane is a gas.  This means that once you turn off the gas machine,
and put the animal on oxygen or room air, you only have to wait until the
animal "blows off" the remainder of the anesthesia by breathing it out.
Essentially, anesthesia begins to lighten as soon as you turn off the gas.
With injectable anesthetics, once it's in, it's in.  While there are some
injectable anesthetics that can be reversed with another drug, these are
generally not the ones used in ferrets.  Ketamine is not reversible.
 
2) Most injectable anesthetics are metabolized (broken down) by the liver,
the kidney, or both.  Inhalant anesthetics (gases) are broken down by the
lung.  Older animals often have low-grade liver or kidney disease, resulting
in impaired metabolism and a potential for much longer duration of
anesthesia.  Lung disease is fairly uncommon in older ferrets, so the odds
are far greater that the anesthetic will wear off more quickly.
 
3) No premeds are needed with isoflurane anesthesia.  In dogs and cats, it
is common to use a mild tranquilizer to sedate the animal prior to
anesthetic induction, and injectable anesthetic to knock the animal out long
enough to put a tube in the trachea, and maintenance with gas.  Often, a
drug known as atropine is used to decrease salivation and intestinal
motility as well as to support the heart rate is also given.  This is not
necessary in ferrets.  The easiest way to anesthetize a ferret is simply to
administer isoflurane by facemask or tank, and when they are groggy, put in
the tracheal tube.  Do your procedure, and as when you are done sewing them
up, stop the gas and administer a combination of oxygen and room air.  In
most cases, the ferret will be awake within five minutes, ten at the most.
Any additional tranquilizers will extend the length of the anesthesia, and
also increase the risks unnecessarily.  Tranquilizers are also given to
minimize post-anesthetic flopping around in dogs, and to a lesser extent in
cats.  This is not usually a problem in ferrets following isoflurane
anesthesia, so the extra risk is not worth taking.  If it is a problem, you
can administer a mild sedative at the time rather than routinely
incorporating another into the regiment.
 
A couple of comments on yesterday's post:
 
>I called and talked to our vet on this subject and their response was a bit
>enlightening, to say the lest.  Ketamine is a Tranquilizer, often used with
>or in place of Valium, for the same reasons similar drugs are given to
>humans, prior to surgery - to help calm then down.
 
Ketamine is really a dissociative - the animal is dissociated from its
environment - in essence, it's hallucinating.  This is not to be construed
as "calming them down", really.  There has also been a continuual question
whether animals (or people) under the influence of ketamine still feel pain -
the cellular response (vascular blanching, nerve impulses) are still
there.  Valium is a tranquilizer, and also does nothing for pain.
 
>Animals, like most people, get really freaked-out, when a mask is forced
>over their mouth nose.
 
My experience is that this is not really the case.  While anesthesia doesn't
smell great, the process of masking a ferret down usually more stressful to
owners than ferrets, and if a ferret does get highly stressed, a tank can be
used.  (Actually, it is not too bad if the animal has a little stress - it
forces it to take deeper breaths, and induction of anesthesia occurs more
quickly.)
 
In short, there is no question in my mind that isoflurane anesthesia is the
way to go in ferrets - it is far safer in the long run than injectable
anesthetics of any type, which may be more convenient for the vet, but
risker and more unpredictable for your pet.
 
Bruce Williams, DVM
 
[Moderator's note: I'm reminded of a couple of vet techs (now both ex-techs,
for obvious reasons...) who would "enjoy" ketamine themselves.  They
reported being aware of things happenning to them (though the things
wouldn't always make perfect sense) and, yes, they were able to know if they
were in pain, but they were basically unable to move even if they wanted to.
Doesn't sound like too much fun for the ferrets either.  BIG]
[Posted in FML issue 2252]