APPLIED EVIDENCE

Management of the Patient with Otitis Externa

 Wilmington and Cincinnati, Ohio

 Submitted, revised, March 4, 2001.

From the Clinton Memorial Hospital Family Practice Residency, Wilmington, and the University of Cincinnati Department of Family Medicine. Reprint requests should be addressed to Keith B. Holten, MD, Family Health Center, 825 W. Locust St, Wilmington, OH 45177. E-mail: keholtenmd@cmhregional.com.

  Pathophysiology

The ear canal is a blind sac with an anterior recess. Trauma to the canal, accumulation of keratin, or a change in pH can trigger inflammation and infection. One study⁴ found that aerobic bacteria account for 91% of bacterial causes; anaerobes, 4%; and mixed infections, 4%. The most common offending organisms are Pseudomonas aeruginosa (50%), Staphylococcus aureus (23%), anaerobes and gram-negative organisms (12.5%), and yeast, such as Aspergillus and Candida (12.5%). The increased pH of pool water is believed to make infection more likely, since bacteriologic studies fail to show a direct link between swimming pool contamination and the organisms of OE.

  Diagnosis

There are no published studies of the accuracy of the medical history, physical examination, or office laboratory tests for the diagnosis of OE. Diagnosis is usually made based on physical examination findings: pain on movement of the auricle, edema, redness, and foul-smelling discharge.⁵ Swelling often obscures the tympanic membrane.

NOE is also a clinical diagnosis and requires a high index of suspicion. A study by Zaky and colleagues³ considered 2 new cases and 32 that were retrospectively reviewed from the literature. They found the following frequencies of symptoms: pain (100%), purulent discharge (97%), bilateral involvement (21%), and a polyp in the external canal (88%). Diabetes was common in this group of patients (82%), confirming that it is consistently a predisposing risk factor, and 91% of these patients were aged 55 years and older.

Few papers have been published concerning diagnostic studies for NOE. One found that temporal radiographs and tomograms are positive in most cases of NOE but were not necessary for diagnosis.⁶ The erythrocyte sedimentation rate is usually increased,³ but this is true in many other illnesses. Many studies^3,8-9,31-35 have reported that Pseudomonas is the primary offending organism for NOE. Because most ear cultures are positive for Pseudomonas, these cultures are of questionable value.¹⁰

There are 4 studies that consider more aggressive diagnostic testing for NOE using conventional temporal radiographs, tomographic temporal radiographs, qualitative and single photon emission computed tomography⁶⁷ gallium scans, and qualitative and quantitative⁹⁹ technetium bone scans.^6-9 These studies were limited by the use of unclear⁷ or poor quality^6,8 reference standards (radiograph or poor response to antibiotics). The diagnosis of NOE does not require additional studies. Expert opinion supports a diagnosis based on the history and physical examination and poor response to treatment. The most common symptom of NOE is persistent pain that is constant and severe. The leukocyte count may be normal or mildly elevated.³ Physicians should consider the diagnosis of NOE in any patient with diabetes who has OE, particularly older patients. Characteristics of OE and NOE are presented in Table 1.

  Treatment

Otitis Externa

The main principles of treatment are local cleansing of debris, drainage of the infection, re-establishment of the normal acidic environment, use of topical and systemic antimicrobials, and prevention of recurrent infections. The evidence regarding these treatments is summarized in Table 2. The best evidence (grade of evidence: A) demonstrates equivalent results with ear cleaning, an ear wick, and any of the choices of topical agents^12-13—acidifying agents, antibiotics, antibiotic and steroid combinations, or antifungal agents. Frequent dosing (3 to 4 times daily) for at least 4 days is supported by the studies. Two studies demonstrated equivalent efficacy with topical ciprofloxacin or ofloxacin dosed twice daily compared with antibiotic and steroid combinations dosed 4 times daily.^16-17 However, these agents are also more expensive than older topical antibiotics. The evidence for single topical treatments and oral antibiotics is weaker^14-29 (grade of evidence: B).

Physicians should treat patients with one of the following regimens for at least 4 days:

• ear cleaning + ear wick + acidifying agent dosed 4 times daily

• ear cleaning + ear wick + topical antibiotic dosed 4 times daily (twice daily if quinolone)

• ear cleaning + ear wick + topical antibiotic/steroid combination dosed 4 times daily (twice daily if quinolone)

The ear is best cleaned by simply irrigating the canal. Be sure to look for a foreign body, particularly in younger patients. For a wick, use either the Pope ear wick (Merocel Corporation, Mystic, Conn) or a fourth-inch sterile gauze. The wick helps draw topical medications into the affected canal, particularly when it is obstructed. The patient should return in approximately 2 days for removal of the wick and reassessment. Do not forget analgesics; this is a painful condition.

Necrotizing Otitis Externa

The treatment for NOE must be aggressive. As the infection invades through the soft tissues into surrounding bony structures, it can be life threatening.¹⁰ The evidence for various treatments is presented in Table 3. The studies are weaker than those for treatment of otitis externa (grade of recommendations: B and C). They support twice daily dosing with oral ofloxacin 400 mg orally twice daily or ciprofloxacin 750 mg orally twice daily for up to 3 months.^31-33 There is weak evidence that hyperbaric oxygen is effective.³⁴ Intravenous anti-Pseudomonal antibiotics are often used initially, based on expert opinion (grade: D) and the high mortality rate.

The oral fluoroquinolones (ofloxacin and ciprofloxacin) show promise for treating NOE. The choice of parenteral or oral antibiotics still rests with clinician judgment, based on the patient’s clinical presentation. If oral antibiotics are started, the length of treatment should be based on the severity of illness.

  Prognosis

The prognosis for cure of OE is excellent, although the actual natural history of untreated disease has not been studied. OE complicated by NEO is more common in persons with diabetes who have a persistent course and granulation tissue visualized in the external auditory canal. Untreated NEO can lead to osteomyelitis and paralysis of cranial nerves. Death can result from sepsis and central nervous system infection.

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The Journal of Family Practice ©2001 Dowden Health Media