Acute Otitis Media

Acute Otitis Media: New Approaches to a Common Problem

Benjamin Cable, M.D. , Richard J. H. Smith, M.D.
University of Iowa Hospitals and Clinics

First Published: Fall 2002
Last Revised: February 2003
Peer Review Status: Internally Peer Reviewed

Para buscar en este sitio

The American Academy of Pediatrics defines acute otitis media (AOM) as "fluid in the middle ear accompanied by signs and symptoms of ear infection." This seemingly simple definition is difficult to apply in practice. Indeed, diagnosing AOM remains one of the hardest challenges facing a pediatric health care provider. Current studies have shown that primary-care providers range in accuracy from 40% to 50% in diagnosing AOM with a hand-held otoscope. Sub-specialty trained otolaryngologists approach 80% accuracy levels with the same otoscopes.

The diagnostic challenges of the ear exam can be greatly aided by a few simple steps. The first and most commonly overlooked step is cerumen removal. Cerumen removal should take less than a moment or two and in many cases can be effectively completed with no more than a disposable cerumen loop and an otoscope. With an assistant illuminating the external auditory canal with the otoscope about 5-10 cm away from the ear, the practitioner is free to use both hands. One hand retracts the pinna and advances the tragus while the other is free to manipulate the loop. As cerumen is only produced in the outer 1/3 of the auditory canal, the vast majority of cerumen can be removed under direct vision and with virtually no discomfort to the patient. However, if visualization is difficult, the patient is anxious, or the cerumen is deeply impacted, the external auditory canal should be cleaned using microscopic illumination and magnification.

The second critical aide to the ear exam is pneumatic otoscopy. Because the otoscope only allows monocular vision, three-dimensional views are impossible. By using the speculum to obtain an air-tight seal with the external auditory canal, air pressure can be varied with an insufflation bulb. Watching the resultant movement of the tympanic membrane provides the examiner with another critical piece of information about the status of the middle ear.

The third and probably most valuable aide in the ear exam is tympanometry. This measure of tympanic membrane compliance (the reciprocal of stiffness) is generated by continuously measuring middle-ear impedance as air pressure in the external auditory canal is systematically varied. The resultant tympanogram takes less than a minute to obtain, does not depend on patient cooperation, and provides valuable information on middle-ear function, with positive and negative predictive values greater than 90%.

Once an accurate diagnosis of AOM has been made, providers should base their treatment on a firm understanding of the many drug-resistant pathogens that are present in the pediatric population. Most cases of AOM are caused by S. pneumoniae (40-50%), H. influenzae (20-30%), and M. catarrhalis (10-15%). Each of these pathogens has developed an increasing number of resistant strains.

Current estimates for S. pneumoniae resistance are placed at approximately 35%. This bacterium has developed resistance to penicillin-based antibiotics by altering its penicillin-binding proteins. These proteins essentially serve as a "docking port" for the drug and, if altered, help the bacterium avoid interaction with the drug. However, drug concentrations can be increased to the point that the kinetics of the drug-bacterium interaction are overwhelmed and take place irrespective of the binding protein modifications. This strategy is the basis of high-dose regimens and has resulted in the development of a number of very useful algorithms in the treatment of AOM. One of the most commonly cited high-dose regimens is the CDC algorithm published in 1999 (Fig. 1). This algorithm identifies high- and low-risk patients for drug-resistant pneumococcus. High-risk patients should always be treated with high-dose therapy.

Figure 1. 1999 CDC Algorithm¹
First-Line Therapy	High risk for drug resistant S. pneumoniae (DRSP) (<2 years old, day care, antibiotics treatment in last 3 mo)	Amoxicillin 80-90mg/kg/d
	Low risk for DRSP (none of the above factors present)	Amoxicillin 40-45mg/kg/d
Treatment Failure (after 72 hours)	(Consider tympanocentesis)	Amoxicillin-Clavulanate Cefuroxime Axetil Ceftriaxone (IM)
¹Centers for Diseae Control and Prevention. Acute otitis media: management and surveillance in an era of pneumocococcal resistance. Pediat Infec Dis J., 1999, 18:1-9.

H. influenzae and M. catarrhalis have developed an alternate mechanism of drug resistance. Each of these bacteria produces beta-lactamase, a substance capable of directly degrading the beta-lactam ring of penicillins. H. influenzae and M. catarrhalis are estimated to produce beta-lactamase in approximately 35% and 90% of cases, respectively. Unlike S. pneumoniae's resistance profile, increased antibiotic concentrations have no effect on this bacterial defense. Current strategies focus on added inhibitors, such as clavulanate, or the more stable beta-lactam rings of the cephalosporins. One of the most practical algorithms for this strategy was proposed by the Clinical Advisory Committee in August, 2000 (summarized in Fig. 2).

Figure 2. 2000 Clinical Advisory Committee²
First-Line Therapy	High risk for DRSP (< 2 years old, day care, history of recurrent AOM, contact with individuals treated with antibiotics, treated in last month with Erythromycin-sulfisoxazole, Trimethoprim-sulfamethoxazole, Azithromycin, Ampicillin, or any prophylactic regimen)	Amoxicillin 90mg/kg/d or Amoxicillin 45mg/kg/d plus Amoxicillin/Clavulanate (45mg/kg/d) (Alternates: Cefprozil, Cefuroxime, Cefpodoxime, Cefdinir)
	High risk for B -lactamase positive organisms (preceding therapy with amoxicillin)	Amoxicillin-Clavulanate (45mg/kg/d) (Alternates: Cefprozil, Cefuroxime, Cefpodoxime, Cefibuten, Cefixime, Cefdinir)
	High risk for both DRSP and B -lactamase organisms (one risk factor from eachof above categories)	Amoxicillin 45mg/kg/d plus Amoxicillin-Clavulanate (45mg/kg/d) (Alternates: Cefprozil, Cefuroxime, Cefpodoxime, Cefdinir)
	Low risk for DRSP and B -lactamase organisms (no risk factors from above)	Amoxicillin 40-90mg/kg/d
Treatment Failure		Ceftriaxone or Alternate Oral
Second Failure	Tympanocentesis	Culture Directed Choice
²C Pichichero ME et al. Controversies in the medical management of persistent and recurrent acute otitis media. anns Otol Rhinol Laryngol., 2000, 109: Supplement 183.

Duration of antibiotic therapy for AOM has also been revised. Multiple recent prospective trials have shown that five-day courses for children over 2 years of age with AOM have equal efficacy to standard 10-day courses.

As we continue to focus on appropriate diagnosis and antibiotic therapy, new treatment approaches have begun to emerge. Some strategies focus on prevention. Since only 10% to 15% of children who become colonized with potentially pathogenic bacteria develop an AOM episode within the following month, targeting factors that lead from colonization to infection may decrease rates of AOM. For example, we know that many upper-respiratory-tract viruses down-regulate the immune system and create mucosal breakdowns that allow bacterial attachment and infection. Interrupting this pathway could result in fewer episodes of AOM.

Another promising approach is immunization. A conjugate pneumococcal vaccine is recommended for all children starting at 2 months of age. This vaccine was designed to protect children from invasive infections, including pneumonia and meningitis. While it is extremely effective in this regard, it has also been found to have a positive impact on AOM. Initial licensing studies showed a 57% decrease in AOM caused by the serotypes of pneumococcus included in the vaccine. This striking statistic is somewhat tempered by an overall reduction in AOM of only 6%, but even this much smaller number is important from a public health perspective. Vaccinated children underwent 20% fewer procedures for tympanostomy tube placement than did unvaccinated children. This level of improvement has prompted the development of vaccines to target M. catarrhalis and nontypable H. influenzae.

The anti-influenza vaccine shows an even greater impact on AOM rates. Using both inactivated and attenuated forms of influenza virus, multiple prospective studies have shown that overall AOM rates decrease by 30% to 35% during the influenza season. Although the only currently approved form of this vaccine is injectable, these studies included a nasal spray form that was equally effective in reducing AOM. It is anticipated that this form of the vaccine will obtain FDA approval this year.

Another area of active research is the dietary consumption of polyol sugars like xylitol. Also known as birch sugar, xylitol has comparable relative sweetness to sucrose, which it replaces in "sugarless" gum. Because it inhibits the growth of S. mutans, chewing xylitol-containing gum does not lead to dental caries. Interestingly, xylitol also inhibits the attachment of S. pneumoniae and H. influenzae to the nasopharyngeal epithelium, thereby decreasing overall AOM rates by 36% to 42% in three prospective studies when the gum was chewed five times daily.

http://www.vh.org/pediatric/provider/otolaryngology/otitismedia/index.html