Severe Pneumonia in the Elderly: Risks, Treatment, and Prevention

, Winthrop University Hospital, Mineola, NY

Disclosures

Medscape General Medicine. 1998;1(3) 

In This Article

Impact of Underlying Medical Illness

How do other diseases contribute to pneumonia risk? The incidence of comorbid medical illness, such as diabetes mellitus, heart disease, malnutrition, cancer, azotemia, and chronic liver disease increases with age, impairing immune defenses and predisposing the elderly to pneumonia. Diabetes mellitus is associated with neutrophil dysfunction, diminishing chemotaxis and phagocytosis, especially in ketotic or hyperglycemic states.[17] Congestive heart failure with pulmonary edema impairs clearance of pneumococci and staphylococci from the respiratory tract.[13,18] In addition, excess alveolar fluid fosters microbial growth and impairs surfactant functioning, which limits alveolar macrophage functioning.[18,19] Reduced apoprotein A, a surfactant protein, contributes to bacterial proliferation, especially in mechanically ventilated patients. The use of morphine sulfate and other sedatives and hypnotics can suppress cough and mucociliary clearance, thereby increasing the risk for aspiration and ensuing infection.

In patients with liver disease, colonization of the oropharynx with gram-negative bacteria predominates. Gram-negative oropharyngeal colonization is also associated with alcoholism.[20] Atelectasis from pleural effusions and/or ascites further compromise ventilation and bacterial clearance.[12]

In older age groups, renal failure is most commonly due to diabetes. Kidney dysfunction, complement deficiency, and impaired cellular immunity results in gram-negative colonization of the upper airway, resulting in an increased risk of pneumonia.[10,21,22] Staphylococcus aureus is a common colonizer of the respiratory tract and a cause of pneumonia in patients on hemodialysis.[11] Experiments in animal models with renal failure found a decreased clearance of staphylococci and Pseudomonas aeruginosa with increased buccal cell binding of gram-negative bacteria.[22]

Neoplasms can affect host defenses in numerous ways due to underlying immunologic impairment, weight loss, malnutrition, and/or as a consequence of therapy. For example, neutropenia can be secondary to the underlying neoplasm or it can be a consequence of chemotherapy. Neoplasms are also associated with locally impaired host defenses. In lung cancer, airway obstruction is secondary to tumor and/or adenopathy. Other commonly associated problems are the need for medications which suppress an already compromised cough reflex, and impairment of the mucociliary apparatus by cytotoxic drugs, and/or radiation.

Malnutrition in the older individual is both complicated and multifaceted.[23,24] Immune impairment from malnutrition varies, depending on whether there is an acute or a chronic deficit. Research indicates that acute starvation in mice results in impaired pulmonary clearance of S aureus and Serratia marcescens, while chronic protein malnutrition did not alter lung clearance of S aureus and P aeruginosa, but impaired clearance of Listeria monocytogenes (a common pathogen of the upper respiratory tract in the elderly).[25] Cell mediated immunity is typically altered by chronic starvation. Decreased bacterial clearance in the respiratory tract, secondary to malnutrition, would be expected to favor colonization, because pathogens have prolonged exposure to respiratory epithelium.[23] Hypoalbuminemia, while an identified risk factor for pneumonia in the elderly, more likely reflects underlying "sickness" rather than actual nutritional status.[26]

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