Rapid institution of empiric antibiotic therapy is the cornerstone of ED treatment of the infected elder. It is clear that the consequences of a delay in diagnosis or treatment are much more grave in this population. Table 12 outlines suggested empiric antibiotic therapies for the most common infections in the elderly.



Antimicrobial Considerations In The Elderly

A pill for every ill, an ill from every pill. Proper antibiotic selection is particularly important in the elderly patient for a multitude of reasons. The incidence of adverse drug effects is 1.5-3.0 times higher in older patients.⁸⁷ (See Table 13.) Practically every pharmacokinetic parameter is altered in geriatric patients, including absorption, distribution, metabolism, and excretion. Because creatine clearance decreases an average of 10% per decade of life after age ^20,88 all elderly have some degree of renal insufficiency?an important consideration when selecting an antimicrobial agent.



Antibiotic choice is directed by several factors, including the suspected organ system involved. Table 12 lists the most common pathogens associated with various sites of infection. Note that geriatric patients are not only prone to a different spectrum of pathogens than younger patients, infections are also more likely to be polymicrobial. Thus, broad-spectrum antibiotics are usually indicated. Pharmacodynamics, side effect profiles, and compliance are also important considerations. The elderly have a high rate of noncompliance,which is in no small part due to complex dosing regimens. Once or at most twice a day dosing is preferred for outpatient treatment.

Penicillins and cephalosporins are generally the antibiotics that are best tolerated and have the least incidence of side effects in the elderly. Aminoglycosides have excellent activity against many gram-negative organisms but have the risk of ototoxic and nephrotoxic side effects. When used, aminoglycosides should be adjusted for the patient's diminished renal function. Once-daily dosing of gentamycin using the Hartford nomogram can decrease both toxicity and costs while possibly improving outcomes over traditional regimens. ^125-127 Nitrofurantoin should be avoided as it strongly associated with adverse reactions in the elderly.

The presence of "hardware" such as a central line or a prosthetic valve or joint increases the risk for methicillin-resistant Staphylococcus aureus and should trigger consideration of vancomycin in addition to other antimicrobials.

Pulmonary Infections

Once the diagnosis of pneumonia has been made, promptly administer antibiotics. The sooner the treatment is initiated, the lower the mortality and morbidity. ^38,40,89 The Clinical Pathway "Evaluation Of Fever In The Elderly Patient" outlines the decisions leading to admission and parenteral antibiotic therapy in this population. For inpatients, give the first dose before transfer to the in-hospital bed; for outpatients, the first antibiotic dose (oral or parenteral) should be given in the ED before discharge. (For more information on the treatment of pneumonia, see the September 1999 issue of Emergency Medicine Practice, "Community-Acquired Pneumonia: Deciding Whom To Admit And Which Antibiotics To Use.")

The most recent generation of fluoroquinolones (such as levofloxacin or sparfloxacin) and the extendedspectrum macrolides (such as azithromycin or clarithromycin) provide excellent coverage of both typical and "atypical" organisms. These agents are useful for both inpatient and outpatient therapy. Patients ill enough to require intensive care may be treated with a macrolide or new-generation fluoroquinolone in combination with a third-generation cephalosporin (such as cefotaxime or ceftriaxone) or a beta-lactam/betalactamase inhibitor (such as ampicillin/sulbactam,
ticarcillin/clavulanate, or piperacillin/tazobactam).

If influenza virus is suspected, amantadine or rimantadine can be given. However, these drugs are only
effective against influenza A.⁹⁰ Because confusion is a common side effect of amantadine in the elderly, reduce the dose by half.⁹¹

Urinary Tract Infections

Several studies have substantiated the use of short-course (3-day) oral therapy for elderly women with isolated lower urinary tract infection, though some experts still advocate a seven-day course.^92,93 Indwelling catheters predispose to colonization by multiple organisms and multidrug resistance.

An upper tract infection should be suspected in the patient who has any combination of high fever, new mental status changes, toxicity, flank tenderness, or granular casts in the urine. An upper tract infection is also likely in patients who do not substantially improve after 72 hours on oral antibiotics.

As with any febrile elder, a low threshold for admission is necessary for those with urinary tract infections. All older patients with evidence of acute pyelonephritis require admission. Elderly patients with pyelonephritis are much more likely to have bacteremia and urosepsis than their younger counterparts. UTI is the most common cause of bacteremia in older adults?of those with pyelonephritis, 66% will develop bacteremia, and up to 22% of elderly women with pyelonephritis develop sepsis.^94-96 Rapid institution of parenteral antibiotics is indicated in patients with signs of toxicity.

For outpatients, fluoroquinolones are an excellent choice. While TMP-SMX is frequently prescribed, increasing bacterial resistance is a growing concern, especially on the West Coast. While there are local variations in antibiotic susceptibility, more than 15% of common urinary pathogens are resistant to ampicillin, cephalothin, and trimethoprim/sulfamethoxazole.⁹⁷ Patients with upper tract disease and those with urosepsis may benefit from a combination of ampicillin or ceftriaxone plus an aminoglycoside, or a high-dose fluoroquinolone. A beta-lactam/beta-lactamase inhibitor such as ampicillin/sulbactam may also be effective.

Infection co-existent with an obstruction is a urological emergency and may require cystoscopy or surgery to remove the stone. Perinephric abscesses usually require percutaneous or open surgical drainage, whereas intrarenal abscesses can usually be managed with prolonged antibiotic therapy.

Abdominal Infections

Optimal treatment of cholecystitis and appendicitis consists of hemodynamic stabilization, empiric antibiotic therapy, and early surgical intervention. Uncomplicated diverticular disease is usually managed medically. Seventy percent of patients recovering from a bout of uncomplicated diverticulitis will have no recurrences regardless of medical or surgical management.⁹⁸ Mild disease is treated on an outpatient basis with a high-fiber diet, usually in conjunction with oral antibiotics. Severe or complicated disease is treated on an inpatient basis with IV fluids, nasogastric suction, and empiric antibiotics.

Treatment Of Fever

Numerous animal experiments show that fever can be a protective response during bacterial infection.⁹⁹ Although there have not been any clinical trials regarding the benefit of fever in the elderly, some pneumonia studies demonstrate a higher mortality rate in afebrile elderly patients.¹⁰⁰ There is also evidence that antipyretic treatment may have an adverse effect on the immune system.¹⁰¹

On the other hand, fever itself can be detrimental to elderly patients. It can be the source of mental status changes, worsen cardiopulmonary disease, and predispose to dehydration. With every degree Celsius increase, there is a 13% increase in oxygen consumption and heightened caloric and fluid requirements.¹⁰² This increase in basal metabolic rate elevates the heart rate as well?a significant stressor for the elderly person with COPD or unstable angina. In general, fever in the elderly is treated with antipyretics, acetaminophen being a safe and effective choice.