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Pneumonia: Predisposing Factors, Prevention and Treatment
by Keith C. Meyer, M.D.
Geriatric Times September/October 2004 Vol. V Issue 5
Severe pneumonia can cause premature death or unrelenting disability in previously healthy, productive elderly individuals. Although the many changes that occur with advancing age are thought to predispose the elderly to lower respiratory tract (LRT) infections are not necessarily proved beyond a doubt, both immunologic and non-immunologic changes that occur with aging likely increase the risk of developing pneumonia. This article will discuss and summarize factors that predispose the elderly to developing pneumonia as well as strategies that may prevent it.
Understanding Risks
Why do older individuals have a greatly increased risk of developing pneumonia, increased morbidity and mortality, and prolonged recovery as compared to younger adults? This is not an easy question to answer because there are many age-associated changes that can increase the risk of LRT infection in older adults in addition to various disease states such as structural lung disease, diabetes, rheumatologic disorders and cardiac dysfunction that are typically associated with increased risk of pneumonia. Nonetheless, certain age-associated changes or conditions have been linked to LRT infection in the elderly.
Decline in immune function and host defense has been linked to infection risk in the elderly (Meyer, 2004). Because the lung is directly exposed to the external environment via inhaled air and has a total mucosal surface area that is approximately the size of a tennis court, innate immune mechanisms (immediate, recognition of pathogen-specific components) and mucociliary clearance must function properly when challenged by inhaled or aspirated potential pathogens and clear them before significant infection becomes established. If immediate clearance mechanisms are not effective, acquired immune responses (delayed, lymphocyte-mediated) must kick in and provide antigen-specific responses to invading microorganisms before the host is overwhelmed by a large burden of the offending agent or an overexuberant local or systemic inflammatory response occurs. Although there is considerable interindividual variation, many aspects of acquired immunity wane with advancing age, and both antibody production and T cell responses generally decline. Mucociliary clearance also has been shown to decline with advanced age.
Many other factors have also been linked to LRT infection risk in the elderly (Table 1). Oral clearance and salivary flow keep pathogenic bacteria from colonizing the oral cavity, and medications (e.g., antihistamines, antidepressants, antiparkinsonian agents, diuretics) or conditions that disrupt salivation and oral clearance are implicated as important pneumonia risk factors, particularly for pneumonia due to gram-negative bacilli (Palmer et al., 2001). Conditions that predispose to aspiration (e.g., stroke victims or patients with Alzheimer's disease) or that blunt mechanical airway clearance responses to aspiration are important risk factors for LRT infection as well. Other pneumonia risk factors include malnutrition and hypoalbuminemia, chronic organ dysfunction (e.g., structural lung disease, congestive heart failure, renal failure), hospitalization or residence in a long-term care facility, or viral infection (e.g., influenza, rhinovirus).
Treating Patients
If an elderly individual develops bacterial pneumonia, the key elements of successful treatment are rapid diagnosis and prompt administration of empiric but adequate antibacterial chemotherapy (Table 2). Because typical symptoms of pneumonia are frequently lacking in the elderly patient, physicians must be aware that altered mental status may be the sole sign of an evolving LRT infection. Rapidly instituting empiric antibiotic therapy following guidelines established by the American Thoracic Society for community-acquired pneumonia without performing extensive, time-consuming, diagnostic testing that delays antibiotic administration may not only be life-saving but may prevent prolonged hospitalization and subsequent debilitation (Niederman et al., 2001).
When community-acquired pneumonia is suspected, a chest radiograph should be performed to establish the diagnosis and to detect other processes such as a significant parapneumonic effusion, the presence of multilobar pneumonia, underlying chronic obstructive pulmonary disease or a lung mass causing post-obstructive pneumonia. It is not necessary to obtain a sputum Gram's smear and cultures unless a drug-resistant organism is suspected and the Gram's smear could be used to focus initial antibiotic selection. Atypical pathogens (Legionella, Mycoplasma pneumoniae and Chlamydia pneumoniae) are not identified on the sputum Gram's smear, and patients are frequently not able to produce an adequate specimen ( >25 PMNs and <10 squamous epithelial cells). Furthermore, the sputum Gram's smear often does not identify the correct pathogenic organism in the lower respiratory tract when a pathogen is isolated from blood cultures or transthoracic needle aspiration. When a patient is ill enough to require admission to the hospital, two sets of blood cultures should be drawn before administration of antibiotics, and thoracentesis should be performed on patients with pleural effusions that layer >10 mm on lateral decubitus chest X-ray to evaluate the characteristics of the effusion and detect a complicated parapneumonic effusion or empyema, if present.
Because antibiotic resistance by various respiratory pathogens is a growing problem, physicians must consider the likelihood that a given patient may have a pneumonia caused by bacteria resistant to some of the widely used antibiotics and institute empiric therapy that will cover drug-resistant pneumococci or other agents such as gram-negative bacilli, including Pseudomonas aeruginosa, if the possibility of infection caused by these organisms is present. In addition, if viral influenza is suspected, prompt administration of a neuraminidase inhibitor within 36 to 48 hours of the onset of symptoms may prevent subsequent serious infection and associated bacterial LRT infection.
Chemoprophylaxis with such agents may also be warranted if influenza A or B is epidemic in the community, especially for institutionalized patients. If elderly patients develop pneumonia while hospitalized or residing in a long-term care facility, vigilance for the presence of difficult-to-treat, antibiotic-resistant bacteria must be maintained and empiric therapy must cover typical hospital-acquired pathogens that are often resistant to multiple antibiotics.
Prevention Is the Goal
Because the outcome of treating LRT infection may be unsuccessful despite the best care and the choice of optimal antibiotics, prevention of pneumonia is obviously preferable to treatment. Administering vaccines that provide immunity to common respiratory pathogens can be safe, protective and cost-effective. However, protective responses may be attenuated in the elderly due to a decline in humoral and cell-mediated immunity (Meyer, 2004).
A meta-analysis conducted by Dear and colleagues (2003) suggested that the widely used pneumococcal vaccine that stimulates antibody formation to capsular polysaccharides does not provide significant protection. Many smaller studies, however, have suggested that the vaccine is protective. On the other hand, one recent cost-efficacy analysis suggested that extending the pneumococcal vaccine to those in the general population ages 50 to 64 would provide benefit (Sisk et al., 2003). The influenza vaccine has been shown to be effective in the elderly when the vaccine and circulating influenza strain are matched, and it is now recommended for individuals age 50 or older as well as at-risk, younger populations.
Optimizing nutrition through oral protein and energy supplements have been shown to reduce all-cause mortality in elderly individuals (Milne et al., 2002). Other important interventions include smoking cessation, minimizing the risk of aspiration, optimal therapy of chronic disease states, avoiding institutionalization whenever possible, and administering neuraminidase inhibitors for early treatment of viral influenza or for prophylaxis with community or institutional outbreaks (Table 3).
Lower respiratory tract infections remain a major cause of debility and death in the elderly. Improved preventive measures including better vaccines may decrease risks in the future, but preventive measures that can be utilized at present are often overlooked. Similarly, LRT infections are frequently not perceived by health care providers in early stages as they progress, especially when typical symptoms and signs are lacking.
If antibiotic choices do not cover the causative pathogens or antibiotic administration is delayed, morbidity and mortality will likely be increased. Prevention, rapid diagnosis and rapid administration of appropriate antibiotics can optimize outcome, especially for the elderly.
Dr. Meyer is professor of medicine and medical director of lung transplantation at the University of Wisconsin Medical School.References
Dear K, Holden J, Andrews R, Tatham D (2003), Vaccines for preventing pneumococcal infection in adults. Cochrane Database Syst Rev (4):CD000422 [see comment].
Meyer KC (2004), Lung infections and aging. Ageing Res Rev 3(1):55-67.
Milne AC, Potter J, Avenell A (2002), Protein and energy supplementation in elderly people at risk from malnutrition. Cochrane Database Syst Rev (3):CD003288 [see comment].
Niederman MS, Mandell LA, Anzueto A et al. (2001), Guidelines for the management of adults with community-acquired pneumonia. Diagnosis, assessment of severity, antimicrobial therapy, and prevention. Am J Respir Crit Care Med 163(7):1730-1754.
Palmer LB, Albulak K, Fields S et al. (2001), Oral clearance and pathogenic oropharyngeal colonization in the elderly. Am J Respir Crit Care Med 164(3):464-468.
Sisk JE, Whang W, Butler JC et al. (2003), Cost-effectiveness of vaccination against invasive pneumococcal disease among people 50 through 64 years of age: role of comorbid conditions and race. Ann Intern Med 138(12):960-968.
