Tintinalli's Emergency Medicine - Just the Facts, 3ed.

32. PNEUMONIA, BRONCHITIS, ANDUPPER RESPIRATORY TRACT INFECTION

Jeffrey M. Goodloe

BRONCHITIS

EPIDEMIOLOGY

images Acute bronchitis is a commonly encountered, typically viral infection of the lower respiratory tract airways that often follows an upper respiratory infection.

images Incidence of acute bronchitis predominates in fall and winter, affecting up to 5% of the adult population in the United States.

PATHOPHYSIOLOGY

images Respiratory viruses cause the vast majority of cases of acute bronchitis. Influenza A or B, parainfluenza, respiratory syncytial virus (RSV), and coronavirus are amongst the more common viral etiologies (Table 32-1).

images Atypical bacteria, specifically Mycoplasma pneumo-niae, Chlamydia pneumoniae, and Bordetella pertussis may cause acute bronchitis in otherwise healthy individuals (Table 32-2).

CLINICAL FEATURES

images Early acute bronchitis B manifestations may closely mimic the common cold with symptoms of nasal congestion, rhinorrhea, and sore throat.

images Acute bronchitis symptoms, including the primary manifestation of cough with or without sputum, typically resolve within 3 weeks.

images Sputum purulence may accompany the hallmark persistent cough of acute bronchitis and is indicative of sloughed inflammatory airway cells; taken alone, sputum does not indicate a bacterial etiology.

images Acute bronchitis typically presents without fever >38°C (100.4°F), heart rate >100 beats/min, or respiratory rate >24 breaths/min. These vital signs, particularly in patients older than 64 years of age, should lead to investigation for other respiratory ailments, including pneumonia.

DIAGNOSIS AND DIFFERENTIAL

images Clinical diagnosis of acute bronchitis is supported with (1) acute cough (less than 2–3 weeks duration), (2) no history of chronic lung disease, and (3) absence of focal consolidation, egophony, or fremitus by chest auscultation.

images Pulse oximetry is indicated if the patient describes dyspnea or appears short of breath.

images Sputum Gram’s stain and culture are not recommended in the routine diagnosis of acute bronchitis.

images A chest radiograph is not required in nonelderly patients who appear nontoxic, unless symptoms exceed 3 weeks in duration.

images Consider pertussis in adolescents and young adults, particularly if eliciting a known contact with a confirmed pertussis case or coughing paroxysms with prominent post-tussive emesis.

TABLE 32-1 Viral Causes of Acute Bronchitis and Upper Respiratory Infections: Presentation and Management

image

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images Although predominantly viral in etiology, acute bronchitis is strongly associated with the prescribing of antibiotics in acute care environments. Although antibiotics are commonly requested by acute bronchitis patients, in non-atypical bacterial cases, antibiotics do not confer clinically relevant benefits and contribute to medication side effects and future pathogen resistance.

images For strongly suspected pertussis, treat with azithromy-cin to decrease coughing paroxysms and limit disease transmission.

images Airflow obstruction findings (eg, wheezing) should be treated with bronchodilators. Albuterol by a metered dose inhaler, 2 puffs q4h to q6h, is usually effective.

images Additional agents for cough suppression, mucolysis, or other symptom relief should be considered on an individual basis, factoring comorbidities, drug interactions, and potential side effects.

TABLE 32-2 Known Bacterial Causes of Bronchitis

image

PNEUMONIA

EPIDEMIOLOGY

images Community-acquired pneumonia (CAP) is a common medical problem, accounting for about 4 million cases and 1 million hospitalizations per year in the United States.

images Pneumonia is the sixth leading cause of death in the United States. Bacterial causes are the most common.

PATHOPHYSIOLOGY

images Pneumonia is an infection of the alveolar or gas exchange portions of the lung. Some forms of pneumonia produce an intense inflammatory response within the alveoli that leads to filling the air space with organisms, exudate, and white blood cells.

images Patients most at risk for pneumonia are those with a predisposition to aspiration, impaired mucociliary clearance, or risk of bacteremia.

images Pneumococcus (Streptococcus pneumonia) remains the classic bacterial etiology.

images Besides pneumococcus, other prevalent bacterial pneumonias are caused by Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenza.

images Incidence from atypical and opportunistic agents, particularly if pneumonia is acquired in the health care setting, is increasing.

images Legionella pneumophila, M. pneumoniae, C. pneumoniae, and a spectrum of respiratory viruses account for the bulk of atypical pneumonia.

images Multiple risk factors exist for pneumonia and include chronic diseases, such as cancer, bronchiectasis, chronic obstructive pulmonary disease (COPD), diabetes, sickle-cell anemia, AIDS, and other immunodeficiencies, as well as smoking.

images Aspiration pneumonia occurs more frequently in alcoholics and patients with seizures, stroke, or other neuromuscular diseases. Anaerobic agents must be suspected in aspiration.

images Lung abscesses are frequently related to aspiration pneumonia. Other causes of abscess in the lower respiratory tract include bacteremia from a remote source, pulmonary infarction, neoplasm, or pulmonary trauma.

CLINICAL FEATURES

images Patients with undifferentiated bacterial pneumonia generally present with some combination of cough, fatigue, fever, dyspnea, sputum production, and pleuritic chest pain.

images Physical findings of pneumonia vary with the offending organism and the type of pneumonia each causes, although most are associated with some degree of tachypnea and tachycardia (Table 32-3).

images Pneumococcal pneumonia classically presents with abrupt fever, rigor, and rusty brown sputum. Pleural effusion occurs in 25% of patients.

images Lobar pneumonias (see Fig. 32-1), such as those caused by pneumococcus and K. pneumoniae, exhibit signs of consolidation, including bronchial breath sounds, egophony, increased tactile and vocal fremitus, and dullness to percussion.

images Bronchial pneumonias, such as those caused by H. influenzae, reveal rales and rhonchi on examination, without signs of consolidation. A parapneumonic pleural effusion may occur in either setting; empye-mas are most common with S. aureus, K. pneumoniae, and anaerobic infections.

images Interstitial pneumonias, such as those caused by M. pneumoniae, C. pneumoniae, and a host of respiratory viruses may exhibit fine rales, rhonchi, or normal breath sounds.

images Pneumonia due to Legionella is spread via airborne aerosolized water droplets rather than by person-to-person contact. This particular agent creates patchy bronchopneumonia (see Fig. 32-2), which may progress to frank consolidation and be associated with relative bradycardia and confusion.

images Clinical features of aspiration pneumonitis depend on the volume and pH of the aspirate, the presence of particulate matter in the aspirate, and bacterial contamination. Although acid aspiration results in the rapid onset of symptoms of tachypnea, tachycardia, and cyanosis, and often progresses to frank pulmonary failure, most other cases of aspiration pneumonia progress more insidiously.

images Physical signs of aspiration pneumonia develop over hours and include rales, rhonchi, wheezing, and copious frothy or bloody sputum. The right lower lobe is most commonly involved due to the anatomy of the tracheobronchial tree and gravity.

images Hypoxemia quantified by pulse oximetry may result from any agent of pneumonia, depending upon extent of disease and comorbidities.

TABLE 32-3 Clinical Characteristics of Common Bacterial Pneumonias.

image

DIAGNOSIS AND DIFFERENTIAL

images Uncomplicated presentations in otherwise healthy patients may not require use of radiology, laboratory, or pathology resources, although chest radiography is most commonly used in diagnosis (see Figs. 32-1 and 32–2)

images Additional diagnostic tests can include white blood count with differential and pulse oximetry. In patients with serious consideration for intensive care unit admission, obtaining blood gas analysis and cultures of blood and sputum may provide benefit to the continued treatment course.

images Sputum Gram’s stain rarely changes therapy in the emergency department.

images If Legionella is being considered, serum chemistry studies and liver function tests should be performed, as hyponatremia, hypophosphatemia, and elevated liver enzymes are commonly found. Urine can also be tested for Legionella antigen.

images Most patients do not require identification of a specific organism for clinical resolution of disease.

images Given a multitude of significant pneumonia-causing organisms and special patient populations, the parent text should often be consulted for additional guidance in complicated cases.

images The differential diagnosis includes noninfectious atel-ectasis; acute tracheobronchitis; pulmonary embolus or infarction; exacerbation of COPD; pulmonary vas-culitides, including Goodpasture’s disease or Wegener’s granulomatosis; bronchiolitis obliterans; and endocarditis.

image

FIG. 32-1. Lobar pneumonia.

image

FIG. 32-2. Pneumonia suggesting Legionella.

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images The emergency department treatment and disposition of pneumonia depends primarily on the severity of the clinical presentation and radiographic findings.

images Vital respiratory function (oxygenation and ventilation) should be supported as indicated, up to and including intubation and mechanical ventilation.

images While historical features and clinical examination can prove helpful in predicting a causative organism, the treatment of pneumonia has shifted to empiric therapy based upon the patient’s environment.

images The emergency clinician should differentiate between CAP and healthcare-associated pneumonia with its risk for organisms that require specific and/or broadened antibiotic coverage, such as P. aeruginosaor methicillin-resistant S. aureus.

images The complexity of pneumonia severity scoring as a means to determine discharge or admission prevents inclusion in this review. In general, progressive degrees of abnormal vital signs, comorbidities, and advancing age are associated with need for inpatient management.

images Specialty society guidelines and infectious disease consultation advice change with advent of antimicrobials and resistance patterns. The antimicrobials listed here represent a summary of current and generally accepted antibiotic regimens for adults with the indicated clinical situations. Dosages may require adjustment for renal insufficiency. Refer to parent text for more details.

images Outpatient CAP management for otherwise healthy patients who present in nontoxic states: azithromycin 500 milligrams on day 1 followed by 250 milligrams daily for 4 additional days or doxycycline 100 milligrams twice daily for 10 days (a low-cost alternative). The Centers for Disease Control and Prevention (CDC) recommends reserving oral fluoroquinolones for those failing macrolide or tetracycline class therapy to minimize resistance.

images Outpatient CAP management for patients with significant comorbidities (and without healthcare-associated pneumonia suspected): levofloxacin 750 milligrams orally daily for 5 days or amoxicillin-clavulanate 875/125 milligrams orally twice daily for 10 days plus azithromycin 500 milligrams orally on day 1, followed by 250 milligrams orally on days 2 to 5.

images Inpatient CAP management for patients not requiring ICU admission: initiate levofloxacin 750 milligrams IV or ceftriaxone 1 gram IV plus azithromycin 500 milligrams IV. Implement antibiotics early in the course of any patient with pneumonia requiring admission.

images Inpatient CAP management for patients requiring ICU admission: initiate ceftriaxone 1 gram IV plus levofloxacin 750 milligrams IV. If methicillin-resistant S. aureus (MRSA) is suspected, add vanco-mycin 10 to 15 milligrams/kg IV to the regimen.

images Inpatient management of suspected healthcare-associated pneumonia: initiate double coverage against Pseudomonas with levofloxacin 750 milligrams IV plus cefepime 1 to 2 grams IV every 8 to 12 hours orpiperacillin/tazobactam 4.5 grams IV every 6 hours. Also, initiate coverage against MRSA with vancomycin 10 to 15 milligrams/kg IV or linezolid 600 milligrams IV every 12 hours.

images Aspiration: In aspiration-induced pneumonitis, prophylactic antibiotics are not recommended and their indiscriminate use may contribute to organism resistance. For witnessed aspirations, immediate tracheal suction followed by bronchoscopy (if needed to remove large particles) is indicated. In pneumonitis that has already progressed to pneumonia prior to or shortly after emergency department presentation, initiate levofloxacin 750 milligrams IV plusclin-damycin 600 milligrams IV every 6 hours.

images Empyema: Initiate piperacillin/tazobactam 4.5 grams IV every 6 hours. If MRSA suspected, add vancomy-cin 10 to 15 milligrams/kg IV to the regimen. The patient should be admitted with early consultation with a pulmonologist or thoracic surgeon for further consideration of definitive diagnostic measures and treatment options to promote drainage.

images Lung abscess: Initiate clindamycin 600 milligrams IV every 6 hours for anaerobic coverage plus ceftri-axone 1 gram IV every 12 hours. Inpatient medical management successfully treats a significant majority of lung abscesses; surgical consultation is required in only a minority of cases.

images Discharge instructions should, at a minimum, include close follow-up with a primary care physician, smoking cessation (when applicable), and delineation of symptoms that should prompt a return visit to the emergency department.

SEVERE ACUTE RESPIRATORY SYNDROME

Up-to-date information regarding severe acute respiratory syndrome (SARS) can be found at the CDC Web site.

EPIDEMIOLOGY

images SARS came to worldwide attention in the winter of 2002 to 2003. Numerous deaths were reported in Asia, North America, and Europe.

PATHOPHYSIOLOGY

images The etiologic agent is a coronavirus, SARS-CoV, spread by “droplet infection.”

CLINICAL FEATURES

images SARS should be considered in symptomatic individuals who have traveled to an area with current suspected community transmission of SARS or who have had close contact within 10 days of symptom onset with a person known or suspected to have SARS.

images In the appearance of SARS, clinical findings included temperature >100.4°F (>38°C) and one or more findings of cough, shortness of breath, difficult breathing, or hypoxia, with advanced cases indicating radiographic evidence of pneumonia or respiratory distress syndrome. Future outbreak symptoms can be referenced at the CDC Web site.

DIAGNOSIS AND DIFFERENTIAL

images Initial testing for suspected SARS patients may include chest radiograph, pulse oximetry, blood cultures, sputum Gram’s stain and culture, and testing for viral respiratory pathogens. Specifics on recommended differential pathways and confirmatory testing can be referenced at the CDC Web site.

EMERGENCY DEPARTMENT CARE AND DISPOSITION

images No specific SARS treatment recommendations can be made at the time of this text’s creation.

images Clinicians evaluating suspected SARS cases should use standard precautions (eg, hand hygiene) together with airborne (eg, N-95 respirator or greater), and contact (eg, gowns and gloves) isolation precautions. Consider eye protection.

images Empiric therapy should include coverage for organisms associated with any CAP of unclear etiology, including agents with activity against both typical and atypical respiratory pathogens. Treatment choices may be influenced by severity of the illness. See section above.

images Infectious disease consultation is recommended.


For further reading in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 67, “Acute Bronchitis and Upper Respiratory Tract Infections,” by Thomas A. Tallman; Chapter 68, “Community-Acquired Pneumonia, Aspiration Pneumonia, and Noninfectious Pulmonary Infiltrates,” by Charles L. Emerman, Eric Anderson, and David M. Cline; and Chapter 69, “Empyema and Lung Abscess,” by Eric Anderson and Sharon E. Mace.