LAST month I told you of the
paradigm shift I had in whether
to use an alcohol-based scrub as a
hand disinfectant. Yet part of the
problem I had with that was that
I had no evidence base for this
change of mind.
In fact it wasn’t so much a change
of mind with a set of criteria that
changed my thought processes, but
rather a change of heart.
And much
of veterinary
medicine is
about heart
quite as much
as mind – we
have been
trained in the
art and science of veterinary medicine.
Actually, when I look at it now
there is a scientific base to support my
choice of the alcohol-based scrub but
it wasn’t that which changed my mind.
And even though we have a modern
mantra that everything we do should
be evidence-based, the vast majority
of my clinical decisions may have
an evidence base somewhere but my
therapeutic choices on a day-to-day
basis are primarily based on my past
experience.
As an ophthalmologist, when I have
a case of glaucoma I first reach for a
prostaglandin analogue topical drop.
There are four papers in the literature
documenting how these work in dogs
with glaucoma and three of these are
based on a specific group of beagles in
Florida.
Good background science
Those dogs have a type of open angle
glaucoma which is a good model
of chronic glaucoma in people but
may not mirror particularly well the
glaucoma we see in other breeds of
dog. The background science is good:
uveitis in dogs results in a reduction
in intraocular pressure mediated by
prostaglandins in the anterior segment
of the eye which opens up new
drainage pathways for the aqueous
humour.
So PGF2alpha, which I always
associated only with cattle
reproduction, works really well
topically in many dogs with glaucoma
to resolve the high intraocular pressure
within half-an-hour.
I know that from my experience but
as far as having a strong evidence base
akin to that in human ophthalmology
where there are hundreds of papers on
the subject, we basically y by the seat
of our pants!
Ah you say, well that is a niche
subject like glaucoma therapeutics in a
small eld like ophthalmology. What more can you expect? What about a
condition much more regularly seen?
Something like an aural haematoma?
I remember as a veterinary student
seeing those drained under a general
anaesthetic and being amazed that
buttons sewn onto the pinna seemed
to have a beneficial effect.
I reasoned that the haematoma
might be caused by the animal shaking its head and that buttons sewn on
the pinna might cause more head
shaking, but the evidence – well the
four or five I saw operated on then
– seemed to suggest that this was an
effective treatment. But a quick search
through the literature shows only a
very few papers on the subject, one
on cyanoacrylate glue, one on use of
indwelling drains in nine dogs, and
another on use of a bovine mammary
teat tube with complications in seven
out of 35 patients.
Closed suction drainage gave good
results in seven out of 10 cases and
yet another on CO2 laser showed good
results in eight out of 10 cases. No
controlled clinical trials comparing
any of these therapeutic options have
been undertaken and the very fact
that we have so many treatments does
suggest that nothing works particularly
brilliantly well.
Perhaps one of the main problems
is that we do not understand the
pathogenesis of the problem.
A study to evaluate possible
immunopathogenesis did not yield
positive results.
Compare that with anal furunculosis
in the German shepherd dog where an
imbalance of infiltrating lymphocyte
populations was reported. This led
to a substantial change in treatment
regime, from ablative surgery to
cyclosporine medical treatment, a real
paradigm shift, to return to where this
perambulation started.
More focused studies
Perhaps the best evidence base to
inform treatment choices is not
merely large-scale comparisons of
different therapeutic options but more
focused studies on the pathogenesis of
conditions.
Putting the two together is the
ideal way forward. The tibial plateau
levelling operation for canine cruciate
ligament rupture is in many ways an excellent example of this. Barney
Slocum described this technique back
in 1993 based on clinical results in
no fewer than 394 cases but also on
his previous biomechanical studies on
forces in the canine stifle. But I do
have a problem with the subsequent
studies on the technique.
Over the subsequent 20 years,
thousands upon thousands of TPLOs
have been performed. And although
many of us non-orthopods might
jest that it is the Totally Pointless Leg
Operation, it has had a significant
benefit to many dogs with cranial
cruciate rupture. But other techniques
are available.
And for all the cases which have
gone under the knife, we just don’t
seem to have much evidence to say
whether the TPLO and the lateral
suture is better. Putting TPLO and
lateral suture into PubMed yields only
four papers.
No significant difference
The most recent one, from September
last year, shows no significant
difference in long-term results between
the two techniques while a study of
complication rates post-operatively
showed a rate of 8.4% of infection/
inflammation after the TPLO
compared with the lateral suture at
4.2%.
The trouble is, of course, that this is
from one centre, and while the study
involves over 900 animals, it is difficult
to know if those risk factors would
vary with a different surgical team. Can
it be used by a single surgeon starting
out on CCL repair to decide which
technique to use? Does it really mean
much at all?!
Maybe we shouldn’t be so hard
on ourselves regarding how much
data we need to make a decision.
The government tells us we should
be eating five portions of fruit and
vegetables a day – or maybe it’s now
seven! Where did those numbers come
from? Consuming five portions a day
had no effect on inflammatory airway
disease in one study14 nor on cancer
prevention in a large recent meta-
analysis.
A study of nearly 17,000 middle-
aged people in Norfolk found that
those in the top quartile of fruit
and vegetable consumption had a
significantly higher self-reported health
status than those in the lowest quartile
of consumption.
Quite what relevance that has to
populations in central London or in
Glasgow I’m not sure; for me the main
thing that sort of study shows is just
how woefully poor our reporting of
much disease in companion animals is,
or at least has been to date; veterinary studies are often lucky to have 17
animals in their dataset, far less 17,000!
Hopefully, the RCVS push towards
an evidence-based profession will have
beneficial results but that will need all
vets to contribute rather than leaving
the issue to those in academia.
We are so much better than the
doctors at seeing healthy animals on a
regular basis and could so easily collate
our findings through systems such
as VetCompass with merged clinical
databases now accessing records of
more than half a million pets.
Here’s trusting that such efforts pay
handsome dividends!
References
1. Verwilghen, D. R. et al (2011) Surgical
hand antisepsis in veterinary practice:
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2. Leftwich, M. W. and Carey, D. P. (1981)
Cyanoacrylate adhesive for aural hematoma.
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3. Kagan, K. G. (1983) Treatment of canine
aural hematoma with an indwelling drain. J
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4. Wilson, J. W. (1983) Treatment of
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14. Baldrick, F. R. et al (2012) Effect of fruit
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