Biyernes, Setyembre 2, 2011

Pneumonia


Pathophysiology and Etiology
  • The organism gains access to the lungs through aspiration of oropharyngeal contents, by inhalation of respiratory secretions from infected individuals, by way of the bloodstream, or from direct spread to the lungs as a result of surgery or trauma.
  • Patients with bacterial pneumonia may have an underlying disease that impairs host defense; pneumonia arises from endogenous flora of the person whose resistance has been altered, or from aspiration of oropharyngeal secretions.
    • Immunocompromised patients include those receiving corticosteroids or immunosuppressants, those with cancer, those being treated with chemotherapy or radiotherapy, those undergoing organ transplantation, alcoholics, I.V. drug abusers, and those with HIV disease and acquired immunodeficiency syndrome.
    • These people have an increased risk of developing overwhelming infection. Infectious agents include aerobic and anaerobic gram-negative bacilli; Staphylococcus; Nocardia; fungi; Candida; viruses, such as cytomegalovirus; Pneumocystis carinii (also known as P. jiroveci); reactivation of tuberculosis (TB); and others.
  • When bacterial pneumonia occurs in a healthy person, there is usually a history of preceding viral illness.
  • Other predisposing factors include conditions interfering with normal drainage of the lung, such as tumor, general anesthesia, and postoperative immobility; depression of the central nervous system (CNS) from drugs, neurologic disorders, or other conditions, such as alcoholism, and intubation or respiratory instrumentation.
  • Pneumonia may be divided into three groups:
    • Community acquired, due to a number of organisms, including Streptococcus pneumoniae
    • Hospital or nursing home acquired (nosocomial), due primarily to gram-negative bacilli and staphylococci
    • Pneumonia in the immunocompromised person
  • People over age 65 have a high mortality, even with appropriate antimicrobial therapy.