Which nursing action should be included in the management of the patient with external otitis

Cytology

Cytology should be carried out in all cases presenting with clinical signs of otitis externa as it is a quick and inexpensive way of detecting primary factors such as ectoparasites and secondary infections. This is achieved by examining the exudate taken from the ear canal. The equipment needed to obtain samples are cotton buds and microscope slides. It is important that cytology and any culture and sensitivity samples are taken before any ear cleaners or medicated products have been administered to prevent any contamination or removal of exudate. A cotton bud should be inserted deep in the horizontal canal and gently rotated several times in order to collect exudate. Care must be taken when this technique is carried out as it may cause pain to the patient or further trauma to an already inflamed and damaged ear canal.

The exudate on the cotton bud should then be rolled onto a clean dry microscope slide. This is best achieved when the microscope slide is placed on a flat surface, as it helps to create an even thin layer of exudate. Samples should be obtained from both ears and labelled accordingly, as bilateral disease may be present although clinical signs may only be evident in one ear. It is also important because it is not uncommon for both ears to have different pathology (Bosznay, 2014).

The slide should then be allowed to air dry or dried with a heat source for example a hairdryer or wall mounted hand dryer. Once dried the slide should be stained using Romanowsky type stains. Some dermatologists advise to only stain the slide with the 3rd (purple) stain, as the fixer can dissolve ear wax or remove microorganisms such as bacteria (Paterson, personal communication). The slide should then be rinsed using clean water and allowed to dry before viewing under the microscope. When using the microscope the slide should be viewed using the lower x4 and x10 lenses to check for any ectoparasites such as Otodectes cynotis or Demodex spp. that can be missed if only the higher lenses are used. To view small organisms or cells more closely the slide can be viewed on the x1000 lens using immersion oil (Hensel, 2009).

Cytology of a clinically normal ear canal can be distinguished by the presence of cerumen (Figure 1), exfoliated squamous epithelial cells collected from the canal wall, and scant numbers of commensal organisms in the form of cocci and yeast.

Performing cytology and bacterial cultures is a very useful skill for veterinary nurses to have: it helps the veterinary surgeon to reduce the irresponsible use of antimicrobial medication, thus helping to reduce the occurrence of bacterial resistance. This is becoming increasingly important as antimicrobial resistance is now on the UK risk register. There are many cytology training courses available for veterinary nurse to acquire these skills, so they are able to feel confident in carrying out cytology.

Organisms commonly found in the ear canal

Yeast is a commensal organism found in low numbers in a normal ear canal. The most common being Malassezia spp. which is characteristically shaped like a ‘peanut’ or ‘snowman’ (Figure 1) and appears dark purple in colour when stained with Romanowsky stain. Multiple studies have failed to reach a consensus on how many Malassezia organisms found within a microscope field is deemed normal. Several studies have suggested that 1–2 yeast organisms per high powered microscopic field (x100) found from ear cytology is usually considered to be an abnormal quantity of Malassezia spp. Greater numbers than this found per microscopic field is thought to be a large quantity and therefore overgrowth. It is thought large numbers commonly occur when predisposing factors present an optimum environment for replication. Malassezia infection commonly presents with a dark brown sweet smelling exudate (Duncan, 2011).

Bacteria are small prokaryotic cells that can be occasionally found when cytology has been obtained. Bacteria are categorised as cocci or bacilli (rods). Cocci (Figure 2) are spherical in shape, and may occur singularly, in pairs, chains or clusters. The most common, Staphylococcus spp. Streptococcus spp. and Enterococcus spp., can be found occasionally. Bacilli (Figure 3) are shaped like rods or cylinders that can be seen singularly or in chains. Pseudomonus spp. are the most frequently found rods in chronic ear disease with Escherichia coli spp. and Proteus being present occasionally (Bosznay, 2014). Colonisation with these bacteria can occur when the normal environment of the ear canal has changed. Changes can transpire due to hot humid conditions or after swimming when the ear has become moist and also due to the development of one or more primary or predisposing factors (Bloom, 2009). It is important to distinguish whether cocci or rods are present to ensure suitable ear cleaners and antimicrobial therapies are applied to help prevent bacterial resistance. Malassezia and bacterial infections can frequently occur simultaneously in the same ear canal which also plays a part when therapy is being considered. When only yeast is found on cytology bacterial cultures are not necessary. However when rods and/or cocci are seen along with Malassezia (mixed infection), bacterial culture and sensitivity swabs are extremely useful to aid effective treatment. This enables the clinician to identify the type of bacteria present and its susceptibility or resistance to the antimicrobial chosen. Thus appropriate treatment is achieved and the risk of antibiotic resistence reduced.

How to examine the ear

Once cytology has been performed it is important to then examine the ears using a handheld otoscope or video otoscope. This is performed to identify the condition of the ear canal and tympanic membrane. The ear should be examined with care to check the lumen for hairs, foreign bodies and the type and amount of exudate present (Figure 4). The colour of the exudate can be a helpful indicator of the type of infection present, although should not be relied on for diagnosis (Table 5). The ear walls should be checked for the presence of ulceration, polyps and the degree hyperplasia or erythema. It is important to establish whether the tympanic membrane is normal and intact (Figure 5), as some topical therapies cause damage to the middle ear. Therefore if it is established that the tympanic has ruptured, ototoxic therapies should be avoided. In severe case the use of ototoxic ear therapies can lead to permanent deafness (Paterson, 2014). Ear cleaning is, therefore, not only helpful to remove exudate so topical therapies can work correctly, but can also enable the tympanic membrane to be viewed.

The table shows how the colour of the exudate can help indicate the type of infection present.

Management of otitis externa

To provide a good level of control when managing otitis externa all the factors involved must be identified and adequately controlled. This is achieved by the use of appropriate topical and/or systemic medicinal therapy combined with ear cleaning and possible ear flushing. The extent of treatment and prognosis varies based on all the causes and factors involved. Prolonged treatment means owners themselves will play an important role in the success of treatment, as clients will be using ear cleaners and/or applying topical therapy at home. This in an area where veterinary nurses play a major role in educating clients how to clean and apply topical therapy correctly, increasing the possibility of good owner compliance which can often be a challenge.

Ear cleaner properties

Ear cleaning is beneficial in the treatment of otitis externa as it can enable the removal of exudate and cerumen from the ear canal that can cause inflammation of the ear canal and may inhibit the effectiveness of antimicrobials (Paterson, 2014). There are a number of different ingredients that make up ear cleaning solutions with different functions to aid removal of specific types of exudate and cerumen. It is important to be aware that some ear cleaners can be more irritant than others when applied to damaged and/or ulcerated ear canals. Therefore care must be taken when choosing an ear cleaner to prevent causing the patient to be in pain or further damaging the ear canal itself.

Ceruminolytics, surfactants and foaming agents help to soften, emulsify and dissolve cerumen and exudate. Sodium dioctyl sulphosuccinate and triethanolamine polypetide oleate condensate are very effective ceruminolytic agents. Carbamide peroxide is marginally less potent and functions more as a humectant and foaming agent. Other ceruminolytics include sodium lauryl sulphate, squalene and the least effective propylene glycol, glycerine and lanolin.

Astringents such as isopropyl alcohol, acetic acid, boric acid, benzoic acid and milder cleansing agents such as salicylic acid and lactic acid, also known as drying agents, are used to counteract maceration of the ear canal.

Antimicrobial agents are active ingredients found in ear cleaning solutions such as parachlorometaxylenol (PCMX), <2% concentration of chlorhexidine. Some astringents such as isopropyl alcohol, boric acid and acetic acid have antimicrobial properties.

Tromethamine-ethylenediaminetetraacetate (TrisEDTA) is used as a pre-soak or as a base for off license preparations of antibiotics in otitis media. Owners consent must be obtained when any off license medication is prescribed. Tris acts like a buffer, and EDTA (although it has no cleansing properties) damages the bacterial cell walls, especially Gram negative bacteria, to increase antibiotic sensitisation, for example it enhances the antibacterial action of PCMX.

Manual ear cleaning

Educating owners in the importance of good ear cleaning techniques is an essential part of the management of otitis externa. This enables veterinary nurses to support and educate owners, to create good compliance and confidence in their abilities to routinely clean the patient's ears, helping to maintain healthy ear canals and also prevent infection reoccurring.

Ear cleaning technique

Owners should be encouraged to approach ear cleaning step by step:

• Fill the ear canal with the ear cleaner, avoiding touching the canal walls (Figure 6)

• Use the patient's ear pinna to close the opening of the external ear canal and gently massage the cleaner around the inner ear for a couple of minutes, then allow the patient to shake out any excess cleaner by letting go of the ear (Figure 7)

• The last step is to wipe away any dislodged exudate in the superficial portion of the ear canal with a small wad of cotton wool (Figure 8).

Manual ear cleaning is not always successful in removing excessive exudate or cerumen from the deep portion of the ear canal. It can also be difficult for owners to manually clean the patient's ears, especially as cleaning can be painful when ears are very ulcerated, adding to problems with patient compliance. In these cases the patient may need to be admitted for an ear flush under general anaesthetic, to allow the ear to be cleaned thoroughly before manual ear cleaning can be continued at home.

Ear flushing

Ear cleaners for flushing should be chosen using the results of cytology and be warmed to body temperature to prevent scalding the ear canal if it is too hot and to help prevent lowering the patient's body temperature during the anaesthetic. Ear flushing is recommended in cases where excessive cerumen or exudate is present in the external ear canal that cannot be removed by manual ear cleaning alone. When there is a possibility that the tympanic membrane is damaged, flushing should be performed to ensure the middle ear is thoroughly flushed clean of exudate. If exudate is left within the middle ear it can result in secondary infection of the middle ear that can lead to recurrent infection, which can lead to otitis media (Bloom, 2009). Flushing should always be performed under general anaesthetic whereby an endotracheal tube is placed and cuffed to ensure fluid from ear flushing does not enter the respiratory tract via the Eustachian tubes, that could results in aspiration pneumonia. Ear flushing is best accomplished using a video otoscope and a 6 g urinary catheter (with the fenestrated end cut off), as this allows a higher quality view of the ear canal and tympanic membrane. If a video otoscopy is unavailable a handheld otoscope should be used with 6 g urinary catheter. When flushing if the tympanic membrane cannot be viewed it should be assumed that is not intact until visual evidence of the area is achieved. Ear cleaners should be applied and left to soak for 10 minutes in the ear canal, occasionally massaging the ear from the outside to help breakdown any cerumen/exudate (Payne, 2008). A small piece of cotton wool should then be used to clean any excess discharge from the opening of the canal. Using an otoscope, 6 g urinary catheter and a suction unit or syringe the canals should be flushed with the ear cleaner until the fluid runs clear. The canal should be checked intermittently to establish whether the tympanic membrane is intact. If the tympanic membrane is found to be ruptured it is important to ensure that the tympanic bulla is flushed thoroughly with a non-ototoxic product. Thorough cleaning of the middle ear is important to ensure infection has not been trapped. If the tympanic membrane has ruptured and infection has not been effectively flushed from the middle ear canal it is possible for the tympanum to re-heal trapping infection within the middle ear. This can lead to chronic otitis media. Myringotomy and re-flushing of the middle ear until it is thoroughly cleaned will be necessary to ensure adequate treatment. Table 6 shows the equipment needed for ear flushing.

Equipment needed for ear flushing

After the ear canals have been thoroughly flushed, unless contraindicated anti-inflammatory medication can be administered to counteract any further inflammation of the ear canals, and an appropriate medicated topical product applied directly to the canals. Once the patient has recovered from the general anaesthetic the patient is discharged with an appropriate ear cleaner, medical topical solution and/or systemic treatment.

This is where the veterinary nurse can play a further part in educating the owner in how best to clean the ear canals and administer any topical medication correctly. Pain relief may also be administered and dispensed as per the supervising veterinary surgeon. It is good practice for patients to be assessed on and after recovery from the anaesthetic to ensure the appropriate type and level of pain relief is applied. Veterinary nurses can also inform owners of the signs associated with pain, such as head shaking, pawing at the ears face, head pressing and crying etc. This allows owners to update veterinary surgeons if they see any signs of pain so the levels of pain relief can be reassessed if required.

Conclusion

Otitis externa is a commonly presented complaint in small animal practice that may need prolonged treatment in the form of ear cleaning and topical and/or systemic medicated products for the condition to be effectively managed. Cytology plays a major part in the effective diagnosis and therapeutic plan. Veterinary nurses are well placed to provide fundamental assistance to the veterinary surgeon in diagnosing and managing otitis externa.

Key Points

• Ear cytology is an effective step in diagnosing secondary infections that inhibit successful treatment of otitis externa.

• Veterinary nurses can be trained to perform and interpret cytology, ensuring it is an effectively utilised procedure in small animal practice.

• It is important to perform cytology and bacterial cultures to diagnose the presence of bacterial infection, thus helping to reduce the risk of antimicrobial resistance and also aid the speed of recovery by ensuring correct antimicrobials are dispensed.

• Veterinary nurses play an important role in helping to educate owners in good ear cleaning techniques and administration of medication to promote compliance, and in effective management of otitis eternal to prevent re-infection.

Conflict of interest: none.