OTITIS externa is the
inflammation of the external ear
canal and is very common in dogs.
Involvement of the middle ear
compartment is also possible, being
also quite common in dogs and
cats.
Ear problems are seen in first
opinion and referral practice and, due
to their frequently recurrent nature,
constitute a frustrating problem for
owners and veterinarians alike.
The ear inflammation and infection
can result from a
plethora of
different
factors and
recognition
and
correction of
these is the
key to successful management.
Management of ear diseases
includes medical and surgical options
and the aim of these notes, divided in
two articles, is to describe the medical
interventions available for otitis externa
and media. Part one covers ear
cleaning, ear flushing and
myringotomy; part two will cover
topical medications, systemic
mediations and ototoxicity.
Medical treatment of otitis
externa and media: ear
cleaning, ear flushing,
myringotomy
Therapy of otitis consists of
identifying and controlling all the
factors involved and medical options include topical and systemic therapy,
potentiated by ear cleaning and, when
needed, by ear flushing.
Length of treatment and prognosis
varies based on causes and factors. It is
paramount to highlight that the owner’s
involvement is important as most of
the topical procedures will be
performed at home by clients and this
will likely influence the success of
treatment.
Additionally, the relevance of
attending follow-up visits for examination and repeated cytology
should be stressed as often getting the
clients to continue with regular
treatment can be challenging.
Ear cleaning – when?
Whilst is commonly accepted that
cleaning is not necessary in healthy
ears, it is beneficial in the following
conditions:
- Seborrhoeic ears (Figure 1)
- Hairy ears (Figure 2)
- Stenotic ears (Figure 3)
- Pendulous ears
- Purulent discharge (Figure 4)
Ear cleaning is valuable in any treatment regimen as it can remove
debris and pus, potentiate the action of
topical antimicrobials such as
gentamicin and polimixin B and permit
complete diagnostic evaluation of the
ear canal and tympanic membrane.
Manual cleansing can be done at
home by the owners; however, it is
important to instruct them on how to
perform the cleaning and how often to
use the different preparations.
How to instruct owners
For good compliance, it is helpful to
explain the cleaning step by step:
1. Squirt a good amount directly intothe dog’s ear canal – avoid touching the
insides of the ear with the tip of the
bottle (Figure 5).
2. Use the dog’s ear to close the ear
opening and massage all of the liquid
around inside his ear (Figure 6).
3. Then, let go of his ear and let your
dog shake all of the excess ear wash
out.
4. Finally, wipe a small piece of cotton
wool around the entrance and
superficial portion of the ear canal
(Figure 7).
The cleaning fluids most
commonly contain:
- Ceruminolytics, surfactants and
foaming agents. These help soften,
emulsify and dissolve cerumen and
debris. Sodium dioctyl sulphosuccinate
and triethanolamine polypeptide oleate
condensate are potent ceruminolytic
agents; carbamine peroxide is slightly
less potent and acts more as a
humectant and foaming agent. Other
molecules include sodium lauryl
sulphate and squalene. Less effective
ingredients include propylene glycol,
glycerine, and landline. - Astringents or drying agents. These
are used to prevent maceration of the
ear canal and include isopropyl alcohol,
acetic acid, boric acid, benzoic acid and
milder cleansing agents such as salicylic
acid and lactic acid. - Antimicrobial agents. These are active ingredients of many ear
cleansing solutions and include
parachlorometaxylenol (PCMX), some
astringent and drying agents such as
isopropyl alcohol, acetic acid and boric
acid and chlorhexidine (at a
concentration lower than 2%).
In a study (Swinney et al., 2008), the
antimicrobial efficacy of different ear
cleaners against Staphylococcus intermedius,
Pseudomonas aeruginosa and Malassezia
pachydermatis was evaluated in vitro.
Antimicrobial activity appeared to be
associated with the presence of
isopropyl alcohol, PCMX and a low
pH. A more recent in vitro study (S. I.
Steen, 2012) partially contradicted these
results.
More in vivo studies are needed to
correctly assess the efficacy of
cleansing products within the ear as the
otic environment may influence the
action of the molecules. Additionally, a
single in vitro methodology may fail to
assess the multimodal action of
cleaners containing different molecules
with different properties and activities.
Ethylene diamine tetra acetic acid
(EDTA)-tris has no cleansing
properties. It is commonly used as
either a pre-soak or a carrier vehicle in
the treatment of Gram-negative
infections. EDTA promotes increased
permeability to extracellular solutes,
increased sensitisation to antibiotics
and enhances the antibacterial action of
PCMX.
Recently (Guardabassi et al., 2010)
the in vitro antimicrobial activity of a
commercial ear antiseptic containing
chlorhexidine (0.15%) and Tris-EDTA
was evaluated; according to the results,
this product was active against all the
pathogens most commonly involved in
canine otitis.
A combination of acetic acid and
boric acid has been shown to be useful
in the treatment of Malassezia otitis.
Although ear cleaners are normally
not recommended to be used more
than every 48 hours, in one study (Cole
et al., 2003) one cleaner (EpiOtic,
Virbac) used up to twice daily caused
no adverse effects. Manual cleansing
doesn’t remove tightly adherent debris
or material present in the deep portion
of the ear canal and therefore is best
used as routine cleansing at home once
ear flushing has been performed.
Additional manual cleaning can be
ineffective or challenging when ears are
painful and ulcerated.
Ear flushing
Ear flushing is indicated when the
entire external ear canal and/or the
middle ear need thorough cleaning. It
should always be performed under
general anaesthesia with an
endotracheal tube placed and cuffed, to avoid the fluids running from the ear
to the respiratory tract though the
Eustachian tube.
In the presence of hyperplastic,
stenotic or particularly inflamed ear
canals, systemic glucocorticoid
treatment is recommended (0.5-
1mg/kg once daily 2-3 weeks prior to
the flushing).
Ear flushing is best performed
using a video-otoscope or, if not
available, with a urinary catheter or a
feeding tube connected to a syringe
and fluids (sterile saline), preferably
through a three-way tap. Before ear
flushing is performed, some cases may
require use of an ear cleansing solution
to emulsify and remove debris.
If the ear drum cannot be visualised, care should be used as ear
cleaners (with the exception of those
containing only squalene) are not
licensed for applications in the middle
ear and are all potentially ototoxic.
Myringotomy
Iatrogenic rupture of the tympanic
membrane is indicated when otitis
media is suspected and/or confirmed
by diagnostic imaging techniques, to
take samples for cytology and culture
from the tympanic bulla and to allow
flushing of the middle ear cavities.
It should be performed under
general anaesthesia and under direct
visualization after lavage of the external
ear, when the canal is dry. The
preferred method used by the author is
using a 6 French urinary catheter cut
obliquely to a 60o and attached to a 2ml
syringe containing sterile saline solution.
The catheter is advanced through
the ventral and posterior quadrant of
the membrane with subsequent
aspiration of the fluids. An aliquot can
be used for direct cytological
examination and the remaining for
culture.
