Chapter 26 ICU Infections

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CHAPTER 26 • ICU Infections

munity-acquired pneumonia caused by an unknown organism who exhibit little systemic toxicity can be treated initially with either ampicillin or a macro- lide antibiotic, such as azithromycin or clarithromy- cin. Macrolides, fluoroquinolones, and doxycycline are good options when atypical organisms are sus- pected. If the same patient appears toxic, reason- able initial treatments include ceftriaxone with or without azithromycin, levofloxacin, or moxifloxacin with ceftriaxone or an extended-spectrum penicillin. The following caveats apply: if postinfluenza pneu- monia ( Staphylococcus ) is suspected or if the patient is from a geographic region with a high prevalence of penicillin-resistant pneumococci, the addition or substitution of vancomycin should be considered. For patients with a high likelihood of aspiration, clindamycin alone and amoxicillin–clavulanate with metronidazole represent good initial choices. Community-acquired pneumonia in a patient with HIV was discussed earlier. Because a second chance to institute the correct therapy cannot be guaranteed, broad empiric cover- age is necessary for the toxic patient with nosocomial pneumonia. Recognizing that many toxic-appearing patients will not have pneumonia documented, nonetheless, coverage in this situation must include enteric Gram-negative rods (including multiresis- tant organisms), Streptococcus (including penicillin- resistant organisms), and Staphylococcus (including MRSA). Important clues to etiology can be gleaned from knowledge of the patient’s recent antibi- otic treatment, the resident flora of the ICU, the patient’s underlying illnesses, environmental expo- sures, and available culture data. Yet, in the majority of instances, therapy must be initiated empirically. Regardless of the appearance of the Gram stain, ini- tial therapy for critically ill patients should include a coverage for multiresistant Gram-negative bacilli, such as an extended-spectrum penicillin plus an ami- noglycoside or appropriate fluoroquinolone (e.g., cip- rofloxacin) or a third-generation cephalosporin (e.g., ceftazidime) plus an aminoglycoside or fluoroqui- nolone. For patients predisposed to staphylococcal infection (e.g., recent influenza, neutropenia, insti- tutional prevalence, or a suggestive sputum Gram stain), vancomycin represents first-line coverage. A fluoroquinolone, macrolide, or doxycycline should be added if there is an “atypical” clinical or radiographic presentation or if fever persists despite usual therapy. Highly resistant bacteria can be transferred between patients in the ICU, necessitating measures

to decrease cross-contamination. Careful handwash- ing or use of a bactericidal lotion between patient contacts dramatically decreases the risk of nosoco- mial infection. Use of gloves does not diminish the need for handwashing, and it is essential that gloves be changed between patient contacts. Whenever suctioning intubated patients, gloves should be worn on both hands to prevent staff acquisition and trans- fer of pathogens, including herpes viruses. One pneumonic infection that deserves spe- cial discussion is pulmonary tuberculosis. Although patients may be admitted to the ICU with signs and symptoms typical of pulmonary tuberculosis (cavi- tary apical infiltrates, cachexia, fever), the presenta- tion is often subtle. Tuberculosis in the ICU can take on almost any clinical or radiographic presenta- tion. Cavitary lung disease is only marginally more common than other frequently encountered vari- ants: punctate interstitial infiltrates (“miliary pat- tern”), lobar pneumonia, “empyema,” lung nodule, or diffuse bilateral infiltrates compatible with acute respiratory distress syndrome (ARDS). When the suspicion of tuberculosis is high, respiratory isola- tion should be instituted as quickly as possible and maintained until firm evidence suggests that the likelihood of contagion is low. (This is accomplished simply by examining two or more good-quality spu- tum smears for acid-fast organisms.) The implica- tions of missing a case of tuberculosis are enormous: potential death or disability of the infected patient and transmission of infection to the staff and other nearby immunocompromised patients. Viral Pneumonia Certain forms of viral pneumonia occur with distressing frequency in severely immunocom- promised patients (e.g., CMV in transplant recipi- ents). Although rhinitis, sinusitis, laryngitis, and other familiar manifestations of the “common cold” afflict most persons one or more times per year, viral disease rarely extends to the alveolar level in immunocompetent adults. Yet, certain classes of organism—notably adenovirus, influenza, varicella zoster, and in the recent past the coronaviruses responsible for severe acute respiratory syndrome (SARS) and middle east respiratory syndrome (MERS)—can cause devastating illness in exposed individuals who are vulnerable. These diseases gen- erally present with a diffuse bronchopneumonia or ARDS. In addition to general supportive measures applied to patients in respiratory failure, isolation