Criteria For Ventilator-associated Pneumonia Research Articles

Blood Cultures Have Limited Value in Predicting Severity of Illness and as a Diagnostic Tool in Ventilator-Associated Pneumonia

To define the usefulness of blood cultures for confirming the pathogenic microorganism and severity of illness in patients with ventilator-associated pneumonia (VAP). Prospective observational study using BAL and blood cultures collected within 24 h of establishing a clinical diagnosis of VAP. A 15-bed medical and surgical ICU. One hundred and sixty-two patients receiving mechanical ventilation hospitalized for > 72 h who had new or progressive lung infiltrate plus at least two of three clinical criteria for VAP. BAL and blood culture performed within 24 h of establishing a clinical diagnosis of VAP. Ninety patients were BAL positive (BAL+), satisfying a microbiological definition of VAP (>/= 10(4) cfu/mL), 72 patients were BAL negative (BAL-). Bacteremia was diagnosed when at least two sets of blood cultures yielded a microorganism or when only one set was positive, but the same bacteria was present at a concentration >/= 10(4) cfu/mL in the BAL fluid. Bacteremia was significantly more frequent in the BAL+ than in the BAL- group (22/90 patients vs 5/72 patients; p = 0.006). In 6 of 22 BAL+ patients with bacteremia, an extrapulmonary site of infection was the source of bacteremia. Sensitivity of blood culture for disclosing the pathogenic microorganism in BAL+ patients was 26%, and the positive predictive value to detect the pathogen was 73%. Factors associated with mortality were age > 50 years, simplified acute physiology score > 14, prior inadequate antibiotic therapy, PaO(2)/fraction of inspired oxygen < 205, and use of H(2) blockers. By multivariate analysis, only the use of prior inadequate antimicrobial therapy (odds ratio [OR], 6.47) and age > 50 years (OR, 5.12) were independently associated with higher mortality. The rate of complications was not different in patients with bacteremia. Blood cultures have a low sensitivity for detecting the same pathogenic microorganism as BAL culture in patients with VAP. The presence of bacteremia does not predict complications, it is not related to the length of stay, and it does not identify patients with more severe illness. Inadequacy of prior antimicrobial therapy and age > 50 years were the only factors associated with mortality in a multivariate analysis. Blood cultures in patients with VAP are clearly useful if there is suspicion of another probable infectious condition, but the isolation of a microorganism in the blood does not confirm that microorganism as the pathogen causing VAP.

Implementation of bronchoscopic techniques in the diagnosis of ventilator-associated pneumonia to reduce antibiotic use.

In intensive care units, a large proportion of antibiotics are prescribed for presumed episodes of ventilator-associated pneumonia (VAP). VAP is usually diagnosed on a combination of clinical, radiographic, and microbiologic criteria with a high sensitivity but low specificity for VAP. As a result, patients may receive antibiotics unnecessarily. Specificity can be increased by the addition of quantitative cultures of samples of protected specimen brush (PSB) and bronchoalveolar lavage (BAL) to the diagnostic criteria. We prospectively analyzed the effects of implementation of PSB and BAL in the diagnosis of VAP on antibiotic prescription. PSB and/or BAL were performed in patients who fulfilled the clinical, radiographic, and microbiologic criteria for VAP. Based on quantitative cultures of PSB and/or BAL, patients were categorized into three groups: VAP microbiologically proven (Group 1; n = 72); clinical suspicion of VAP not confirmed microbiologically (Group 2; n = 66); and patients in whom bronchoscopy could not be performed (Group 3; n = 17). In Group 1, antibiotic therapy was instituted empirically in 40 patients (56%) (Group 1a) and after obtaining culture results in the other 32 patients (Group lb). Adjustment of therapy, based on culture results, occurred in 14 (35%) patients in Group la. In Group 2 empiric therapy was instituted in 34 (52%) patients (Group 2a) and dIscontinued within 48 h in 17 of them (50%). In Group 3, 17 (100%) patients were treated with antibiotics. Among the 66 patients in whom a clinical suspicion of VAP was not confirmed, only 18 (27%) were treated with antibiotics, and antibiotic therapy was withheld in 48 (35%) of 138 patients who underwent bronchoscopy. Withholding of antibiotic therapy had no negative effect on the recurrence of a clinical suspicion of VAP or on mortality rates. We conclude that addition of bronchoscopic techniques to the criteria for VAP may help to reduce antibiotic use. However, the definite benefits and cost-effectiveness of these techniques should be analyzed in a randomized study.

Impact of BAL Data on the Therapy and Outcome of Ventilator-Associated Pneumonia

To define the impact of BAL data on the selection of antibiotics and the outcomes of patients with ventilator-associated pneumonia (VAP). Prospective observation and bronchoscopy with BAL, performed within 24 h of establishing a clinical diagnosis of a new episode of hospital-acquired VAP or progression of a prior episode of nosocomial pneumonia (NP). A 15-bed medical and surgical ICU. One hundred thirty-two patients hospitalized for more than 72 h, who were mechanically ventilated and had a new or progressive lung infiltrate plus at least two of the following three clinical criteria for VAP: abnormal temperature (> 38 degrees C or < 35 degrees C), abnormal leukocyte count (> 10,000/mm3 or < 3,000/mm3), purulent bronchial secretions. Bronchoscopy with BAL within 24 h of establishing a clinical diagnosis of VAP or progression of an infiltrate due to prior VAP or NP. All patients received antibiotics, 107 prior to bronchoscopy and 25 immediately after bronchoscopy. Sixty-five of the 132 patients were BAL positive (BAL[+]), satisfying a microbiologic definition of VAP (> 10(4) cfu/mL), while 67 were BAL negative (BAL[-]). The BAL(+) patients had no differences in mortality, prior antibiotic use, and demographic features when compared with the BAL(-) patients. More of the BAL(+) patients (38/65) satisfied all three clinical criteria of VAP than did BAL(-) patients (24/67) (p < 0.05). A total of 50 BAL(+) patients received antibiotic therapy prior to bronchoscopy, and when this prior therapy was adequate (n = 16), as defined by the results of BAL, then mortality was 38%, while if prior therapy was inadequate (n = 34), mortality was 91% (p < 0.001), and if no therapy was given (n = 15), mortality was 60%. When therapy changes were made after bronchoscopy, more patients (n = 42) received adequate therapy, but mortality in this group was comparable to mortality among those who continued to receive inadequate therapy (n = 23). A total of 46 of the 65 BAL(+) patients died, with 23 of these deaths occurring during the 48 h after the bronchoscopy, before BAL results were known. When BAL data became available, 37 of the 42 surviving patients received adequate therapy, but their mortality was comparable to the patients who continued to receive inadequate therapy. Patients with a strong clinical suspicion of VAP have a high mortality rate, regardless of whether BAL cultures confirm the clinical diagnosis of VAP. When adequate antibiotic therapy is initiated very early (ie, before performing bronchoscopy), mortality rate is reduced if this empiric therapy is adequate, compared to when this therapy is inadequate or no therapy is given. If adequate therapy is delayed until bronchoscopy is performed or until BAL results are known, mortality is higher than if it had been given at the time of first establishing a clinical diagnosis of VAP. When patients were changed from inadequate antibiotic therapy to adequate therapy, based on the results of BAL, mortality was comparable to those who continued to receive inadequate therapy. Thus, even if bronchoscopy can accurately define the microbial etiology of VAP, this information becomes available too late to influence survival.