Pneumonia, Hospital Acquired, Ventilator Associated

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)