Page 276 - Clinical Manual of Small Animal Endosurgery

264 Clinical Manual of Small Animal Endosurgery

Once the requisite materials have been laid out and sterilised as per
the manufacturer’s directions (see Chapter 1) the procedure can com-
mence. Cytological and bacteriological samples are collected before
introducing the endoscope into the ear canal. This is done prior to any
cleaning or examination of any sort. If needed, deeper samples for the
same clinical pathology testing can be obtained from the middle ear later
in the procedure.
There is some recent questioning as to the merit of bacterial culture
and sensitivity in the ear, citing a wide variability in bacterial species
recovered as well as the wide variance of sensitivity patterns among the
same species isolates. Still, it seems prudent in cases of resistant, con-
firmed bacterial infection that samples from both external and middle
ear be obtained separately.
Once samples for clinical pathology have been obtained a cursory
cleaning of the external ear can be performed. I usually avoid using
ceruminolytic cleaners for several reasons. The turbidity obtained with
dissolution of the ceruminous wax can be difficult to clear even with
subsequent aggressive saline irrigation. Even the mildest ceruminolytic
agent can be mildly irritating, causing some degree of oozing of already
inflamed aural tissues, further hindering good visualisation. Finally, these
agents are generally not sterile preparations, making subsequent culture
of the middle ear more difficult. The use of warm sterile saline is in my
experience more than adequate to achieve excellent results. This initial
cleaning should be done very gently in an effort to avoid causing further
iatrogenic damage to the aural tissues and the resultant difficulty in visu-
alisation. Only the most grossly obstructive material should be removed
in this initial cleaning. Ideally a suction/irrigation pump apparatus can
be used to perform this cleaning, but a red rubber feeding tube of appro-
priate size with gentle syringe pressure works well.
Fluids used as irrigants in otoendoscopy should be slightly warmer
than room temperature to facilitate ceruminolysis and to minimise any
transient post-endoscopy temperature-related neurological signs. Irriga-
tion is ideally done with a simple gravity-fed bag of warm saline via a
standard administration set. A pressure bag or pump can be used if
needed. Again, a suction/irrigation pump can be used via an irrigation
cannula that is delivered through the working channel of the endoscope
to keep the field of view clear intra-operatively, and to remove any col-
lected blood and debris.
With the endoscope/camera assembly held pistol-style in one hand, the
tip of the pinna is held in the other hand and retracted dorsally. This
action opens up the vertical canal for easy access of the endoscope. The
endoscope is placed in the intertragic notch and angled ventrally into the
vertical canal. At the base of the vertical canal the endoscope is deflected
medially towards the centre of the head into the horizontal canal. This
motion, with continued traction on the pinna and ongoing saline irriga-
tion, should open up visualisation of the tympanum.