CITATION: Gwaltney JM. 1996. Management of acute community-acquired rhinosinusitis. APUA Newsletter 14(1): 1-5.

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Management of acute community-acquired rhinosinusitis
Jack M Gwaltney, Jr
Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, Virginia, USA

Upper respiratory infections continue to cause considerable morbidity, time lost from school and work and frequent visits to physicians. The direct and indirect costs of these conditions are substantial, including the use and misuse of antibiotics. Because upper respiratory illness is due to a complex interaction of both viruses and bacteria, development of accurate diagnostic methods and effective management strategies for these conditions has been difficult. This review highlights new information on the pathogenesis of acute rhinosinusitis and places it and other pertinent information into a framework on which to build management strategies.

Role of Viruses. Acute sinusitis is characteristic of the common cold, making it difficult to distinguish the viral rhinosinusitis of a cold from a secondary acute bacterial sinusitis. Computed tomographic (CT) scans of the sinuses of young adults with early (two to four day) colds showed sinus cavity abnormalities in 87% of maxillary and 65% of ethmoid sinuses.1 Gaseous bubbles in the material present in some of the sinus cavities indicated that this condition resulted from thick secretions and not thickened mucous membrane (Figure 1). Obstruction of the infundibulum draining the maxillary sinus was also present in 77% of the patients.

These findings indicate that the drainage systems of the paranasal sinuses do not function normally during the acute stages of a common cold. The maxillary sinus cavity in adults has an average volume of approximately 30 mL. The sinus epithelium contains plentiful goblet cells, but the density of seromucous glands is sparse compared with that in the nasal passages.
2-4 Mucus secreted into the sinus chamber is normally propelled by ciliary action towards and through the infundibulum at a rate of 1 cm/min. The infundibulum, a short passage with an average diameter of 3 mm in adults, empties into the hiatus semilunaris of the ostiomeatal complex (Figure 2). Under normal conditions, ciliary clearance is sufficient to prevent secretions from accumulating in the sinus cavity. During a cold, excessive and/or abnormal secretory activity overwhelms the sinus clearing apparatus and leads to accumulation of thick fluid in the chamber. This accumulation is a key event in colds that sets the stage for secondary bacterial infection of the sinus cavity.

Role of Pharyngeal Bacteria. A second important factor in the pathogenesis of acute bacterial sinusitis is the existence of a reservoir of bacterial pathogens in the nasopharynx (Table 1).5 Bacteria normally found in the nasopharynx include pneumococcus and Hemophilus influenzae, the most important causes of acute bacterial infection of the sinus. How bacteria gain entrance into the normally sterile sinus cavities is unclear, but sneezing and coughing during a cold may play a role in propelling bacteria into these sites. Apparently, bacteria then become trapped by the thick secretions in the cavity and drainage passages, leading to infection.

Differential Diagnosis: Acute Viral or Acute Bacterial Sinusitis
The differentiation of a common cold from acute bacterial sinusitis has always been a difficult clinical problem because of the similarities of the two conditions. Traditional features of acute bacterial sinusitis, including fever, facial pain, tenderness, erythema and swelling, are insensitive diagnostic indicators when compared to positive bacterial culture of a sinus aspirate.
6 A recent study7 used positive sinus x-ray films as the criterion standard for acute bacterial sinusitis to determine the sensitivity and specificity of selected signs and symptoms (Table 2). Colored nasal discharge, cough and sneezing were the most sensitive findings, but they lacked specificity; poor response to decongestants, maxillary toothache and temperature of greater than 38°C were specific but not sensitive. The criterion standard selected in this study was not ideal because sinus imaging (either by x-ray films, CT, or magnetic resonance imaging [MRI]) lacks precision in distinguishing between acute viral and acute bacterial sinusitis (an exception to this is discussed below).

In another study,
8 a criterion standard of gross purulence of a sinus aspirate (culture was not performed) was used to evaluate clinical findings in adults presenting to an emergency room with paranasal symptoms. Patients were included only when examination showed pus from the middle meatus. Nasal discharge alone did not qualify a patient for inclusion. The presence of two of the three criteria of local pain with unilateral predominance, unilateral purulent rhinorrhea and an erythrocyte sedimentation rate of more than 12 had a 79% sensitivity and an 83% specificity.

How can secondary acute bacterial sinusitis be diagnosed in the patient with an initial cold or influenza-like illness? Until a sensitive and specific test is discovered that can be used to make this distinction and in the absence of fever and the classical findings described above, the duration of the illness is probably as good a diagnostic feature as is available for this purpose. Natural rhinovirus colds have a mean duration of seven days, and most are over by 10 to 12 days (Figure 2).
9 Therefore, in patients with colds or influenza-like illnesses in whom the complaints of nasal purulence, facial pressure and associated cough have not improved or are worse after 10 to 12 days, the diagnosis of secondary bacterial infections should be considered.

Routine imaging studies of patients with suspected acute sinusitis are not recommended because of their lack of specificity and cost. However, if they are available, a classic air-fluid level (indicating thin fluid in the cavity) suggests the presence of bacterial infection. When sinus aspirate culture was used as the criterion standard, 16 (89%) of 18 aspirates from young adults with air-fluid levels on x-ray films were positive for bacteria.10 However, an air-fluid level represented only 18 (38%) of the 48 abnormal sinus x-ray findings observed in this series. Thus, a classic air-fluid level on an x-ray film is a specific but insensitive finding.

Bacterial Etiology
Cultures of sinus aspirates have been used during the past four decades to investigate the bacterial etiology of acute community-acquired sinusitis.
11 The results of these studies are in good agreement--Streptococcus pneumoniae and H. influenzae account for more than half of all cases in adults (Table 3). Moraxella catarrhalis, group A beta-hemolytic streptococci and other streptococcal species and Staphylococcus aureus each account for a lesser percentage of cases. Mixed anaerobic infections also cause some acute community--acquired sinusitis, usually arising from a dental infection. Mycoplasma species have not been implicated in acute sinusitis and are an unlikely cause of disease. Chlamydia pneumoniae is a more likely candidate but is not a proven cause at this time.

The incidence and relative importance of the bacteria causing acute sinusitis in the community has not changed since the early studies in the l950s, but their antimicrobial sensitivities have changed, and are continuing to change, in ways that profoundly affect treatment (Table 4). Since these early reports,
S. aureus developed resistance to penicillin, followed by resistance to methicillin. This resistance did not create a major problem because S. aureus is not a frequent cause of acute sinusitis in the community and most sinusitis strains have not been methicillin-resistant.

The development of ampicillin resistance by
H. influenzae was a more serious problem, which raised the cost of antimicrobial therapy. However, a number of effective drugs to treat ampicillin-resistant H. influenzae became available. Similar resistance was also recognized in M. catarrhalis. More recently, a new dimension to the problem of antibiotic resistance has emerged in the United States with the appearance of intermediate- and high-level penicillin resistance in strains of S. pneumoniae.12,13 The incidence of intermediate-level-resistant pneumococcal strains has approached 30% in many areas of the country. Intermediate-level-resistant strains may be susceptible to amoxicillin/clavulanate and some second-generation cephalosporins and are susceptible to cefuroxime and cefotaxime. High-level-resistant strains may be susceptible to the latter two drugs but can also be sensitive only to vancomycin. This new development presents a serious concern for the future management of acute bacterial sinusitis as well as for the treatment of other pneumococcal infections.

Antimicrobial Treatment
The most convincing standard for establishing bacteriologic cure in the antimicrobial treatment of acute bacterial sinusitis is quantitative culture of pre- and posttreatment sinus aspirates. This procedure not only provides a definitive etiologic diagnosis in culture--positive cases but also assures that treatment was effective. Experience has shown that only approximately 50% of aspirates from suspected cases of acute community-acquired sinusitis (including cases confirmed by x-ray films) will grow bacteria. Technical problems in sampling and testing may account for some of the negative specimens. Also, new or as yet undiscovered agents may account for others. But the most likely explanation for most of the negative specimens is that they are from patients who have a viral rhinosinusitis. Supporting this view is the recovery of respiratory viruses from sinus aspirates in up to 15% of patients with suspected acute sinusitis, although many patients were sampled late in the illness when viral shedding would be expected to be diminished.

Because of the above findings, it is not possible to be sure that a bacterial infection is being treated unless a sinus aspirate culture has been obtained. Most cases of both viral rhinosinusitis and acute bacterial sinusitis are self-limited when untreated. For this reason, methods of assessing efficacy other than posttreatment sinus aspirate culture may be misleading. Clinical evaluations are imprecise. Clinical improvement has been reported by patients receiving ineffective treatment in whom follow-up sinus puncture has shown purulent secretions and high titers of the same bacteria present on the pretreatment culture (see below). Follow-up imaging studies show a slow resolution of the problem and have not been correlated with aspirate culture results.

A number of antimicrobials have been evaluated in adults with acute community-acquired sinusitis using pre- and posttreatment aspirate cultures. Those antimicrobials of current interest are prescribed for a 10-day course of therapy (Table 5). Bacteriologic cure rates of more than 90% were achieved with these drugs. In cases not recorded in the table, failure of bacteriologic cure resulted from the use of antibiotics to which the infecting bacteria were not susceptible (e.g., clindamycin for
H. influenzae) or when inadequate doses were used (e.g., cefaclor in daily doses of 1.0 and 1.5 gms). Correlations between drug plasma levels and sinus cavity drug concentrations are not available, making it important for physicians treating bacterial sinusitis to use daily doses and treatment schedules that have been proved effective by sinus puncture studies. For the initial antimicrobial treatment of patients with acute bacterial sinusitis acquired in the community, a 10-day course of treatment is recommended. Longer or shorter courses of treatment are not advisable unless supported by studies employing pre- and posttreatment aspirate culture results.

Antibiotic selection should also be determined by the patient's history of allergies, drug cost and current bacterial susceptibility patterns. Dealing with penicillin-resistant pneumococcal strains presents a challenge. Because use of third-generation cephalosporins or vancomycin for the initial treatment of acute bacterial sinusitis in the community is impractical, treatment options are still represented by the drugs listed in Table 5.
14 Amoxicillin/clavulanate or cefuroxime axetil have been suggested as providing better coverage for intermediate-level-resistant pneumococci. Patients should be followed, and if the clinical course is not satisfactory, especially if intracranial extension of infection is suspected, appropriate imaging studies, lumbar puncture and other diagnostic evaluations should be performed. In such patients, antibiotic coverage should be given for suspected resistant bacteria, including S. pneumoniae and possibly S. aureus.

Ancillary Treatment
Decongestants, such as phenylephrine and oxymetazoline, applied intranasally provide rapid and effective shrinking of the nasal turbinates and give prompt relief of nasal obstruction. However, topical decongestants may cause irritation and burning in the pharynx, adding to the severity of a sore throat. Also, topical decongestants are accompanied by rebound vasodilation and, with prolonged use, rhinitis medicamentosa. Oral decongestants, such as pseudoephedrine and phenylpropanolamine, while giving less prompt and dramatic shrinkage of the turbinates, do provide satisfactory relief of nasal obstruction. Pharyngeal irritation and rebound nasal obstruction are also not a problem. For this reason, oral decongestants may have an advantage in providing better overall relief. Also, a recent study found that oral decongestants did not adversely affect blood pressure in patients with stable hypertension on antihypertensive treatment.

Decongestants are recommended in the treatment of viral rhinosinusitis and acute bacterial sinusitis to open nasal passages and decongest the ostiomeatal area. Any beneficial effect on the sinus cavity or infundibulum is problematic because the small (3 mm) passageway is enclosed in bone and during sinusitis is often obstructed with thick viscous secretions that are not moved by ciliary action. Limited investigations
16,17 have not made clear how much decongestants may help in increasing the size of the maxillary ostium, but overall they may provide benefit by helping clear the ostiomeatal area and nasal passages.

Mucoevacuants, such as guaifenesin and acetylcholine, should theoretically be of benefit in patients with viral and bacterial sinusitis. However, no clear evidence for their effectiveness is available, and clinical trials with guaifenesin in sinusitis have given conflicting results. They are recommended on theoretical grounds, but more data are needed in this area. Until evidence clearly shows the value of topical or oral steroids in promoting sinus or ostial decongestion, evacuating mucus or otherwise benefiting patients with acute sinusitis, they are not recommended.


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