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SOURCE

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Source: Blackford MG, Glover ML, Reed MD. Lower respiratory tract infections. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey L, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146071234. Accessed January 16, 2017.

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DEFINITION

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  • Lung inflammation caused by bacterial or viral infection.

  • Pneumonia developing in patients with no contact to a medical facility.

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ETIOLOGY

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  • Majority of cases in otherwise healthy adults caused by Streptococcus pneumoniae (pneumococcus).

  • Atypical pathogens include:

    • Mycoplasma pneumoniae

    • Legionella species

    • Chlamydophila pneumoniae

  • Other common pathogens include Haemophilus influenza and a variety of viruses including influenza.

  • Staphylococcus aureus and Gram-negative rods causative agents in elderly nursing home patients and in association with alcoholism and other debilitating conditions.

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PATHOPHYSIOLOGY

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  • Microorganisms gain access to lower respiratory tract by three routes:

    • Inhaled as aerosolized particles.

    • Via bloodstream from extrapulmonary site of infection.

    • Aspiration of oropharyngeal contents.

  • Viral lung infections suppress bacterial clearing activity of lung by impairing alveolar macrophage function and mucociliary clearance, setting stage for secondary bacterial pneumonia.

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EPIDEMIOLOGY

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  • One of the most common causes of severe sepsis and infectious causes of death in the United States.

  • Occurs in persons of all ages, although clinical manifestations most severe in very young, elderly, and chronically ill.

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PREVENTION

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  • Polyvalent polysaccharide vaccines available for S. pneumoniae and H. influenzae type b.

  • Annual influenza vaccine.

  • Pneumococcal vaccine.

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RISK FACTORS

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  • Age >65 years.

  • Diabetes mellitus.

  • Asplenia.

  • Chronic cardiovascular, pulmonary, renal, and/or liver disease.

  • Smoking and/or alcohol abuse.

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CLINICAL PRESENTATION

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  • Clinical appearance similar regardless of etiology.

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SIGNS AND SYMPTOMS
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  • Abrupt onset of:

    • Fever.

    • Chills.

    • Dyspnea.

    • Productive cough.

  • Rust-colored sputum or hemoptysis.

  • Pleuritic chest pain.

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PHYSICAL EXAMINATION
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  • Tachypnea and tachycardia.

  • Dullness to percussion.

  • Increased tactile fremitus, whisper pectoriloquy, and egophony.

  • Chest wall retractions and grunting respirations.

  • Diminished breath sounds over affected area.

  • Inspiratory crackles during lung expansion.

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DIAGNOSIS

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MEANS OF CONFIRMATION AND DIAGNOSIS
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  • Chest radiograph.

  • Sputum examination and culture.

    • Gram stain.

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LABORATORY TESTS
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  • Sputum Gram stain and culture.

  • Complete blood count (CBC)

    • Leukocytosis with predominance of polymorphonuclear cells.

  • Arterial blood gas or pulse oximetry.

    • Low oxygen saturation.

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IMAGING
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  • Chest radiograph: dense lobar or segmental infiltrate.

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DIAGNOSTIC PROCEDURES
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  • Sputum induction and bronchoscopy for patients who cannot provide expectorated samples.

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DIFFERENTIAL DIAGNOSIS
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DESIRED OUTCOMES

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  • Eradicate offending organism.

  • Achieve complete clinical cure.

  • Minimize associated morbidity (eg, renal, pulmonary, or hepatic ...

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