Prevention of hospital-acquired pneumonia in critically ill patients (original) (raw)

1993, Antimicrobial Agents and Chemotherapy

Hospital-acquired pneumonia causes considerable morbidity and mortality and adds appreciably to the costs of health care (40, 69). Pneumonia accounts for approximately 10 to 15% of hospital-acquired infections, and mortality rates range from 15 to 50% (5, 24, 37, 40, 69), although the rates of mortality directly attributable to pneumonia may be lower (40). Facultative gram-negative bacilli are isolated in 40 to 60% of these infections (5, 9, 12, 24, 37). Risk factors for colonization and infection of the respiratory tract by facultative gram-negative rods include intubation and tracheostomy, severe underlying disease, especially chronic lung disease, prolonged hospitalization, prior aspiration of gastric contents, and exposure to antibiotics (5, 12, 18, 30, 42, 59, 69). Since gram-negative bacilli account for a major portion of isolates in hospital-acquired pneumonia, efforts to prevent this infection have focused on the elimination of these pathogens. These efforts have been aimed at the elimination of exogenous sources of gram-negative organisms by encouraging regular hand washing by health care workers, the use of aseptic techniques for tracheal suction, and the sterilization of respiratory equipment (37). Although these efforts have had an impact, nosocomial pneumonia remains a major problem. Recently, the focus of intervention has shifted from exogenous sources to the patient's fecal flora as a potential source of gram-negative bacilli that may colonize the nasopharynx and cause pneumonia. This shift has led to renewed interest in the use of topical and systemic antimicrobial prophylaxis to prevent pneumonia. The purpose of this review is to examine the assumptions that underlie the use of antimicrobial prophylaxis to prevent nosocomial pneumonia and to review the results of comparative studies in terms of the efficacy and risks of prophylaxis. The lack of a "gold standard" for the diagnosis of hospitalacquired pneumonia as well as variability in the definition of nosocomial pneumonia makes a comparative analysis of prophylaxis studies difficult. Differences in the patient populations studied provide a source of sample bias that makes generalization of the study results problematic. The focus of this review will be on critically ill or high-risk patients, i.e., patients requiring intensive care unit (ICU) admission and, frequently, mechanical ventilation, because these patients have been the most carefully studied population. Neutropenic patients, who constitute a separate risk group, will not be considered here.