Otitis Externa Flashcards
How does the external ear canal function?
auricular cartilage (ventral canal) overlaps annual cartilage (horizontal canal) to allow flexibility and movement to properly gather and guide sounds into the canal
What shape does the canine ear canal take?
L-shaped with a dorsal pocket and a ventral notch (“trap)
External ear canal:
L = vertical canal with pocket ventrally
R = “in the trap”, edge of annular cartilage
What is normal anatomy of canine ear canals?
depends on breed!
- normal to see hair throughout canal
- round opening
- brachycephalics - narrow oval opening, closes easily
What are 3 differences in the feline ear canal?
- external canal doesn’t have a deep trap
- smaller diameter - difficult to pass some scopes
- bony septum separates middle ear from bulla
What should the tympanic membrane look like? What structures does it have?
clear and transparent
- pars flaccida - moves with pressure differences
- pars tensa - remains still
- malleus - located between PF and PT, concave points rostrally
How does the feline tympanic membrane compare?
bony septum makes it look less transparent
What causes the pars flaccida to become prominent?
increased pressure in the ear canal
- NOT a tumor, but may be indicative of middle ear disease
How do the inner and outer layers of the tympanic membrane compare?
INNER = cuboidal epithelium
OUTER = stratified squamous epithelium
What is behind the tympanic membrane?
MIDDLE EAR - epitympanic cavity (recess), tympanic cavity, ventral (fundic) cavity
- lined with modified respiratory cells - ciliated, secretory
- contains nerves, vessels, ossicles, and muscles
What structures of the middle ear can be seen on otoscopic examination?
VENT = into the bulla
PROM = vestibular window, contains inner ear
How does the middle ear anatomy differ in cats?
- contains a septum to separate the middle ear
- cochlea + cochlear window
Feline tympanum and middle ear:
extremely thin, less transparent membrane
Feline middle ear, CT:
What 6 pathological changes in the ear occur with otitis?
- inflammation - edema and cellular infiltration
- glandular hyperplasia
- epidermal hyperplasia - obstructs duct opening
- additional inflammation - migration of inflammatory cells, release of proteases and other cytokines
- fibroplasia
- ossification
Ear, epidermal hyperplasia:
Ear, folliculitis and furunculosis:
What 5 diagnostics are used for otitis externa?
- history, PE
- otoscopic exam
- cytology***
- culture and sensitivity
- diagnostic imaging
What is commonly necessary for in-depth otoscopic exams? What are 3 keys to proper examination?
sedation/anesthesia as needed - topical, systemic, complete anesthesia for manipulation or surgery
- examine both canals
- visualize the tympanic membrane
- do no harm
How do otoscopes compare to video otoscopy?
OTOSCOPES = 2x magnification, attachment can be used to change pressure and evaluate tympanic membrane
VIDEO = 10x magnification, better light and clarity, good for individuals with visual deficitsW
What is considered the key diagnostic test in ontology?
cytology
- done on both ears no matter what
- done at initial presentation and every recheck exam
Where should cytology samples be collected in cases of otitis?
right at the edge of the annular cartilage in the entrance to the horizontal canal
What is proper positioning of swab and head when collecting ear cytology?
pull out ear horizontally and keep it and the swab horizontal to the floor
- aim past the inner tragus
What is proper technique when dipping cytology slides?
be gentle - wax does not adhere well and material can be lost
- use a clothespin to hold the slide
- never skip stains –> Malassezia sticks well to red-stained material!
- DON’T run water directly on sample
What artifact is seen on this ear cytology slide?
clumping of stain –> not bacteria!
What are 2 normal findings on ear cytology slides?
- cerumen - keratinocytes, sebum, ceruminous secretions from apocrine glands
- microorganisms - low numbers of yeast and various bacteria
Keratinocytes, ear cytology
Ear cytology, yeast:
Malassezia
Ear cytology, mixed infection:
cocci + rods
- mixed = easier to manage –> one has not been able to overpower the others
Ear cytology, WBCs:
epithelial damage
How does Diff-Quik stain compare to a Gram stain?
DIFF-QUIK - highlights bacteria, doesn’t differentiate type
GRAM - highly recommended for mixed infections, can differentiate between G- rods (Pseudomonas), G+ rods (Corynebacterium) and G+ cocci (Staph) –> slide has keratinocyte granules pictured
What are 5 indications for performing a bacterial culture and sensitivity in cases of otitis? Where are samples collected?
- known resistant organisms
- failure to respond to standard therapy
- previous administration of several antibiotics
- single population of rods
- concurrent systemic signs
cleanly from vertical/horizontal canal junction
What are 3 indications for diagnostic imaging in cases of otitis? What are some options?
- clear loss of tympanic membrane
- unable to adequately visualize TM
- recurring infections - look for nidus
radiography, U/S, MRI, CT
What is the purpose of cleaning out the ear before treating it?
removes debris that….
- causes irritation
- blocks movement of medication into horizontal canal
- interferes with self-cleansing - movement of wax from TM outward
- interferes with activity of active ingredients in medication (biofilm)
- increases microorganism burden
How does hair impact diagnosing and treating otitis? What is recommended for proper examination?
- prevents evaluation of entire ear canal and tympanum
- predisposing/perpetuating factor in developing otitis
- blocks penetration of medication into ear
remove hair prior to topical treatment of otitis externa –> NOT routine, can cause trauma that eventually leads to otitis
What is biofilm? What function does it have? What 3 bacteria associated with canine otitis produce it?
matrix of proteins and organic material produced by bacteria –> EPS, polysaccharides, proteins, extracellular DNA
protects microorganisms from immune system, external factors, and topical/systemic medications
- Pseudomonas
- Staphylococcus
- Malassezia
What are considered the best cleansers for purulent and waxy debris in the ear?
PURULENT - anything! (EpiOtic, OtiRinse, TrizEDTA)
WAXY - should contain ceruminolytic agents, like squalene (pH-notic, cerumene, KlearOtic, Douxo micellar solution)
When is deep ear cleaning/flushing indicated? What does it require? How is it performed?
tympanic membrane is unable to be clearly seen
general anesthesia or heavy sedation –> need thorough (aggressive) cleaning of the ear
- visually inspect canals with sterile cone and hand clean
- infuse serumenolytics (Cerumen, KlearOtic, Micellar Solution) for 5 mins
- flush with sterile saline and inspect
- use loops/biopsy if needed
- infuse medication or drying agent (Cort/Astrin)
Deep ear flush:
- could go another round
- residual debris obstructing tympanum
What is Animax? What is an advantage and disadvantage to its use?
Neomycin + Thiostrepton + Nystatin + Triamcinolone
- ADVANTAGE - broad-spectrum
- DISADVANTAGE - ointment-based (poor esthetic)
What does Tresaderm contain? What are some advantages and disadvantages?
Neomycin + Dexamethasone + Thiabendazole
- ADVANTAGES - mild antibacterial and yeast action, propylene glycol based, good for first occurrence
- DISADVANTAGES - mild, must be refrigerated and warmed prior to use, propylene glycol can trigger increased epithelial turnover and wax production
What does Otomax/Mometamax contain? What are some advantages and disadvantages?
Gentamicin + Clotrimazole + Betamethasone/Mometasone
- ADVANTAGE - excellent ingredients
- DISADVANTAGES - ointment based, Gentamicin is ototoxic, terrible packaging
What does Posatex contain? What are some advantages and disadvantages?
Orbafloxacin + Posaconazole + Mometasone
- ADVANTAGES - broad spectrum, excellent anti-inflammatory, excellent antifungal
- DISADVANTAGES - ointment based, terrible packaging, $$$
What does Baytril Otic contain? What are some advantages and disadvantages?
Enrofloxacin + silver sulfadiazine
- ADVANTAGE - excellent against Pseudomonas, broad spectrum (SSD), aqueous
- DISADVANTAGE - minimal anti-fungal, no glucocorticoid
What does easeOtic contain? What are some advantages and disadvantages?
Gentamicin + Miconazole + Hydrocortisone
- ADVANTAGES - good ingredients, excellent applicator, anti-inflammatory
- DISADVANTAGES - Gentamicin is ototoxic, total volume is insufficient, thicker ointment, $$$
What does Surolan contain? What are some advantages and disadvantages?
Polymyxin B + sulfates + Miconazole + Prednisone
- ADVANTAGES - good against Psuedomonas, excellent against Malassezia
- DISADVANTAGES - activity questionable in the presence of pus, ointment
What does Aurizon contain? What are some advantages and disadvantages?
Marbofloxacin + Clotrimazole + Prednisolone
- ADVANTAGES - excellent against Pseudomonas, broad spectrum, SID (10 drops for 7-14 days)
- DISADVANTAGES - not recommended for use in a first occurrence due to fluoroquinolone resistance, NOT in US
What does Canaural contain? What are some advantages and disadvantages?
Diethanolamine fusidate + Framycetin + Nystatin + prednisolone
- ADVANTAGE - broad spectrum
- DISADVANTAGE - ointment, 5-10 drops BID, NOT in US
Commercial otic medications in US:
What are long-acting topical medications used for otitis externa? What is a major advantage?
products containing lanolin (messy!), gel polymers, or lightweight oils able to be applied topically by veterinarians every 7-30 days
removes problem of owner compliance
What are 3 options for veterinary residual products for otitis externa?
- Claro - Florfenicol + Terbinafine + Mometasone (Simplera = generic)
- Ketocort Otic - Ketoconazole + Hydrocortisone
- Osurnia - Florfenicol + Terbinafine + Betamethasone
leave space in ear to empty contents and pull out at the same time to avoid TM rupture
What are 3 important aspects of residual otic preparations?
- great for clients who cannot treat daily
- NOT fire and forget –> need quality control check with recheck appointments
- may require multiple applications - cytology!
What are some advantages and disadvantages to topical therapy for otitis externa?
ADVANTAGES - delivers medication directly to affected areas in high concentrations, inexpensive
DISADVANTAGES - deliver deep into ear may be difficult/dangerous, compliance, poor penetration if middle ear is involved
Is there a value to culturing cases of otitis externa?
YES
- informs clinician of organisms present
- identified sensitive antibiotics
- provides insight into efficacy of other choices
What are considered the best antibiotics for S. pseudintermedius, Pseudomonas, Proteus, and Malassezia causes of otitis externa?
STAPH - Florfenicol, Aminoglycosides, Fluoroquinolones, SSD
PSEUDOMONAS - Aminoglycosides, Fluoroquinolones, Polymyxin B (not with pus), SSD
PROTEUS - Aminoglycosides, Fluoroquinolones, SSD
MALASSEZIA - Azoles, Terbinafine, Nystatin
What are considered the best choices for treating ruptured tympanum, cases with client compliance issues, and first occurrence cases?
Fluoroquinolones
Claro, Osurnia
antiseptics –> first-line approach
How do antiseptics compare to antibiotics when treating otitis externa?
- broad spectrum
- clincial efficacy against multi-drug resistant strains
- complimentary non-antimicrobial properties
- low/unknown impact on resistance
- action limited to site of application/infection
What 4 antiseptics are recommended for cases of otitis externa?
- SSD
- acetylcysteine
- aluminum acetate (Burow’s solution)
- Chlorhexidine
+/- lactic acid, salicylic acid, boric acid, parachlorometaxylenol
What is indicated if antiseptic treatment of otitis externa fails?
more aggressive treatments (antibiotics)
- continued presence of organisms at 10-14 days
- worsening of clinical signs (pain, swelling)
What flushes should be used for otitis externa caused by Malassezia?
those containing NO antibiotics –> antifungal + glucocorticoid
- Ketocort Otic - KTZ + hydrocortisone
- DuOtic - Terbinafine + Betamethasone
What is indicative of allergic otitis? What is the key to success?
inflammation/pruritus without infection seen early in condition
glucocorticoids
What volume of otic medication is recommended based on weight of dogs?
- <10 kg = 0.4-0.5 mL
- 10-20 kg = 0.5-0.7 mL
- <30 kg = 1.0 mL
- <40 kg = 1.5 mL
constitutes extra-label use, higher cost than labeled dose, increased systemic effects
How can owners be sure how much medication they ar putting in their pet’s ears/
bottle adapter cap connected to syringe
What position is recommended for proper installation of ear medications?
lateral recumbency
What are some indications for systemic therapy in cases of otitis externa?
- recurring or severe infection
- concurrent infection elsewhere
- owners incapable of medicating patient
- patients refuse to cooperate
- hyperplastic lesions prevent topical application
- known otitis media
- inflammatory cells seen on cytology
- ulcers present on otoscopic exam
- single population G- rods in recurring infection
- systemic signs
NOT recommended as sole therapy for infectious agents
How long should patients be on systemic medication for otitis externa if indicated/
3-4 weeks
What 2 doses of systemic glucocorticoids (Prednisone) are recommended for different cases of otitis externa?
- ANTI-INFLAMMATORY - 1.1 mg/kg SID, PO for 5-7 days, alternate days for 5 doses
- HYPERPLASIA - 2 mg/kg SID, PO for 5-7 days, then EOD for 5-7 doses, then reduce dose
What is considered best practice for glucocorticoid treatment in the ears?
use aggressively initially then back off
- decrease frequency and potency (dexamethasone to hydrocortisone)
- use antiseptics for long-term management
- avoids systemic effects on HPA axis
What should be done on recheck exams in cases of otitis externa?
- history
- PE + otic exam
- cytology
- culture
What 3 things should be done if treatment failure is seen on recheck exams?
- review treatment options
- review application of medications - have client demonstrate!
- consider additional diagnostics - culture or cytology for new agents, MDR bacteria, or resistant yeast
What 3 things should be done if treatment success is seen on recheck exams?
- work on maintenance plans
- first time - client education
- recurring - identify primary factor
How long should maintenance therapy be continued following initial treatment?
until primary factors are identified AND controlled
- long-term to reduce flare-ups
What are 3 parts of maintenance strategies for otitis externa?
- intermittent cleaning with products with antimicrobial activity
- antiseptics or astringents - vinegar and water, aluminum acetate, enzymatic systems, chlorhexidine
- intermittent use of glucocorticoids - switch from potent agents to those with fewer systemic effects (hydrocortisone, mometasone)
What database should be collected in first occurrence cases of otitis? What treatment approach is recommended?
history + otoscopy + cytology
- clean ears with antiseptics
- treat with appropriate medication based on cytology for 21 days OR intermittently (2-3x weely) with cleansers –> first time cases will most likely by Staph or Malassezia
- recheck in 21 days
What database should be collected in recurrent or non-responding cases of otitis? What treatment approach is recommended?
cytology + video otoscopy + culture + imaging
- clean ears
- more aggressive topical therapy - ingredients, duration, methods
- rechecks!!
- referral
What are 12 guidelines for effectiveness evaluation of topical/otic animal drugs?
- amount of drug interfacing with skin
- concentration/dilution
- vehicle
- solubility in vehicle
- rate of release, penetration, absorption
- surface area medicated
- frequency and manner of application
- contact time
- degree of excoriation
- accuracy of diagnosis
- quantity of hair
- presence of organic matter
