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SOURCE

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. https://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146071234. Accessed September 18, 2018.

DEFINITION

  • Lung inflammation caused by bacterial or viral infection

  • Hospital-acquired pneumonia (HAP)

    • Pneumonia developing >48 hours after hospital admission

  • Ventilator-associated pneumonia (VAP)

    • Pneumonia developing >48 hours after endotracheal intubation

ETIOLOGY

  • Hospital-acquired pneumonia

    • Most common organisms associated with HAP:

      • Staphylococcus aureus

      • Enteric gram-negative bacilli (eg, Klebsiella pneumoniae and Escherichia coli)

      • Nonenteric gram-negative bacilli (eg, Pseudomonas aeruginosa)

    • Ventilator-associated pneumonia

      • Most common organisms associated with VAP:

        • Pneumonia that develops within 4 days of hospitalization:

          • Streptococcus pneumoniae

          • S. aureus

          • Haemophilus species

        • Pneumonia that develops later:

          • aeruginosa

          • MRSA

          • Acinetobacter species

PATHOPHYSIOLOGY

  • 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, which can lead to secondary bacterial pneumonia.

EPIDEMIOLOGY

  • 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

PREVENTION

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

  • Annual influenza vaccine

  • Pneumococcal vaccine

RISK FACTORS

  • Hospital-acquired pneumonia

    • Witnesses aspiration

    • COPD, ARDS, or coma

    • Administration of antacids, H2-antagonists, or proton pump inhibitor

    • Supine position

    • Enteral nutrition, nasogastric tube

    • Reintubation, tracheostomy, or patient transport

    • Head trauma, ICP monitoring

    • Age >60 years

    • MDR risk (eg, MRSA, MDR Pseudomonas) if IV antibiotics use within 90 days (Table 1)

  • Ventilator-associated pneumonia

    • Same as hospital acquired pneumonia

    • MDR risk with septic shock, ARDS, acute renal replacement therapy, or 5+ days of hospitalization (Table 1)

TABLE 12016 IDSA Guidelines Regarding Risk Factors for Multidrug Resistant Organisms in HAP and VAP

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