COMMUNITY-ACQUIRED PNEUMONIA IN THE GERIATRIC PATIENT
Most elderly patients in whom community-acquired pneumonia (CAP) develops have an identifiable risk factor. Predisposing factors include chronic obstructive lung disease, lung cancer, alcoholism, influenza, congestive heart failure, multiple myeloma, chronic lymphocytic leukemia, esophageal disease, neurologic disorders that affect cough and swallowing reflexes (such as basal ganglia stroke), and immunosuppressive medication. Table 8-1 lists some of the relationships between predisposing illnesses and specific organisms that cause CAP in geriatric patients. Streptococcus pneumoniae is the most common bacterial pathogen. Mycobacteria often causes a chronic clinical disorder, unassociated with fever or night sweats, that resembles a pulmonary neoplasm. Mycoplasma pneumoniae is a rare cause of CAP in elderly patients, but polymicrobic infections, Chlamydia pneumoniae pneumonia, and respiratory syncytial virus pneumonia may be more common than initially believed. Legionella pneumonia very rarely is mild enough to permit management in the outpatient setting.
Table 8-1. Microbiologic associations
Manifestations of CAP in elderly patients are variable, ranging from septic shock or adult respiratory distress syndrome to altered mental status (acute confusion or a deterioration from baseline) with cough. Cough occurs more commonly than dyspnea. Some, although not all, patients experience pleuritic pain, sputum production, and fever.
A technically good chest x-ray film, even if the patient is dehydrated, should reveal an infiltrate. Rare exceptions include Pneumocystis carinii pneumonia in the HIV-infected patient and tuberculosis. A number of disorders can produce similar clinical and radiologic abnormalities and resemble pneumonia. The list includes both infectious (bronchitis) and noninfectious [heart failure, pulmonary embolism, lung cancer, aspiration of gastric contents, and BOOP (bronchiolitis obliterans–organizing pneumonia)] disorders. Rarely, pneumonia can be the initial manifestation of lung cancer.
Many elderly patients with pneumonia can be effectively treated without hospitalization. Hospitalization would be indicated for the patient who is immunocompromised (by disease or treatment) or disoriented, or who has concomitant unstable medical disorder(s), an obstructive neoplasm, or infection beyond the lung (concomitant empyema, meningitis, endocarditis, pericarditis, septic arthritis). Patients should also be admitted to the hospital when they are noncompliant or have an inadequate support system, the disease is caused by a bacterium other than S. pneumoniae, Haemophilus influenzae, or Branhamella (Moraxella) catarrhalis, or there is a need for immediate intervention (as in shock, respiratory failure, electrolyte abnormalities, or failure of initial outpatient treatment). This listing is not complete, however, and additional social, ethical, economic, and medical considerations can influence the decision for hospitalization.
Candidates for admission to the ICU include patients who require mechanical ventilation or who have a respiratory rate greater than 30 breaths per minute, multiple lobe involvement, shock that fails to respond to intravenous fluid challenge, or concomitant life-endangering events (myocardial ischemia, meningitis).
The hospitalized patient merits a CBC count, arterial blood gas analysis, electrocardiogram, tests for renal and hepatic function, and measurement of serum electrolytes (including calcium, phosphate, and magnesium). Hypokalemia and hypomagnesemia can precipitate digitalis-related arrhythmias. Hypophosphatemia impairs the contractile properties of the diaphragm during acute respiratory failure, and hypocalcemia, which can occur during gram-negative infections, impairs cardiac contractility, causing arrhythmias and contributing to hypotension.
Although its value is debated, I feel that a properly performed and interpreted Gram’s stain of valid expectorated sputum is a useful guide to direct initial antibiotic selection, and that blood cultures should be obtained before antibiotic treatment is begun. Additional laboratory studies that on occasion provide invaluable microbiologic information include the following: sputum culture, acid-fast bacilli stain/culture, urine Legionella antigen testing, and analysis of pleural fluid.
Fiberoptic bronchoscopy is usually reserved for patients who are immunocompromised and critically ill and for those who have a nonresolving pneumonia. Bronchoscopy can be useful to identify endobronchial pathology (tumors, foreign bodies), polymicrobic infections, and unusual or drug-resistant organisms.
Computed tomography of the lungs is particularly useful when the plain film shows a questionable finding or an obstructive mass, when there is a need to differentiate between a parenchymal lung abscess and empyema, and when interventional diagnostic and therapeutic procedures, such as guided transthoracic biopsy, aspiration, or drainage, are indicated.
Therapy consists of antibiotic treatment, adequate oxygenation, fluid/electrolyte administration, patient positioning, nutritional support, drainage of empyema, and, in the case of patients who will experience prolonged inactivity, prophylaxis for deep venous thrombosis. Patients who experience delirium should be assessed for meningitis, hypoxemia, hypoglycemia, and overmedication. Ancillary treatments that have not proved efficacious include vigorous hydration, postural drainage (in the absence of a lung abscess), and administration of an antipyretic.
Guidelines for the initial empiric administration of an antibiotic to the nonimmunocompromised elderly patient have been published. Selection of an empiric antibiotic would take into account the following: drug allergy history, occupational/ exposure history, renal function, immune status, the probable organism, and the potential for drug-drug interaction. For a patient who is not penicillin-allergic and does not meet the criteria for management in the medical ICU, ceftriaxone would be an appropriate selection. For a patient who merited admission to an ICU, I would consider prescribing levofloxacin, as this fluoroquinolone has demonstrated efficacy in patients with pneumonia caused by the traditional bacterial pathogens, and also in patients infected with Legionella species and Staphylococcus aureus. The antimicrobial should be administered as soon as possible.
When a patient fails to respond to therapy, the clinician should consider the following reasons: The disease is of noninfectious origin; the infection is caused by an unusual organism or is polymicrobic; the respiratory pathogen is resistant to the antibiotic selected; unrecognized/undrained empyema is present; an endobronchial lesion is present; host defenses are deficient, or the cardiovascular system is deteriorating concomitantly (arrhythmia, congestive heart failure, or compromised cardiac blood flow). In the case of an outpatient receiving an oral antibiotic, an additional consideration of drug failure is lack of compliance.
Selected hospitalized elderly patients are candidates for oral antibiotic treatment after 72 hours of intravenous therapy. Candidates for this “switch” (“step-down,” “follow-on,” “sequential”) therapy must be immunocompetent and clinically improving, have no impairment of absorption of oral medication, and have an appropriate support system on discharge. Appropriate drugs for switch therapy include amoxicillin-clavulanate, doxycycline, trimethoprim-sulfamethoxazole, cefuroxime, and levofloxacin, as they are well absorbed, have excellent bioavailability, and provide therapeutic tissue concentrations that inhibit the majority of strains of the two traditional bacterial respiratory pathogens, S. pneumoniae and H. influenzae.
Some measures that appear to enhance drug compliance among geriatric patients include the following: oral and written instructions, the establishment of a daily routine for taking the medication, a simplified medication program, and assistance from family and friends. Patient compliance is also enhanced when oral antibiotic treatment is prescribed no more frequently than twice a day.
The optimum treatment duration for geriatric patients with uncomplicated CAP caused by S. pneumoniae or H. influenzae has never been firmly established. There are data to indicate, however, that a 7- to 10-day treatment course is appropriate. Recovery of premorbid physical health often exceeds 30 days, and complete radiographic resolution often takes 3 to 4 months after the onset of antimicrobial therapy. Malignancy and neurologic disease are associated with a high risk for death within 30 days of the recognition and management of pneumonia. (R.A.G.)
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