Impact of Invasive and Noninvasive Quantitative Culture Sampling on Outcome of Ventilator-Associated Pneumonia

Abstract

We performed an open, prospective, randomized clinical trial in 51 patients receiving mechanical ventilation for more than 72 h, in order to evaluate the impact of using either invasive (protected specimen brush [PSB] and bronchoalveolar lavage [BAL] via fiberoptic bronchoscopy) or noninvasive (quantitative endotracheal aspirates [QEA]) diagnostic methods on the morbidity and mortality of ventilator-associated pneumonia (VAP). Patients were randomly assigned to two groups: Group A patients (n = 24) underwent QEA, PSB, and BAL; Group B patients (n = 27) underwent only QEA cultures. Empiric antibiotic treatment was given according to the attending physician and was modified according to the results of cultures and sensitivity in Group A using PSB and BAL results and in Group B based upon QEA cultures. Bacteriologic cultures were done quantitatively for EA, PSB, and BAL. Thresholds of > or = 10(5), > or = 10(3), and > or = 10(4) CFU/ml were used for QEA, PSB, and BAL, respectively. Microbial cultures from Group A patients were positive in 16 (67%) BAL samples, 14 (58%) PSB samples, and 16 (67%) QEA samples. In Group B patients, QEA microbial cultures yielded positive results in 20 of 27 (74%) samples. In Group A, there was total agreement between culture results of the three techniques on 17 (71%) occasions. In five (21%) cases, QEA coincided with either BAL or PBS. In only two (8%) cases, QEA cultures did not coincide with either PSB or BAL. No cases of positive BAL or PSB cultures had negative QEA cultures. Initial antibiotic treatment was modified in 10 (42%) patients from Group A and in four (16%) patients from Group B (p < 0.05). The observed crude mortality rate was 11 of 24 (46%) in Group A, and 7 of 27 (26%) in Group B, whereas the adjusted mortality rates (observed crude minus predicted at admission) for Groups A and B were 29 and 10%, respectively. There were no statistically significant differences when comparing crude and adjusted mortality rates of Groups A and B. There were no differences in mortality between both groups when comparing pneumonia, considering together Pseudomonas aeruginosa and Acinetobacter spp. (Group A, 33% versus Group B, 27%). There were no differences between Groups A and B with regard to ICU stay duration and total duration of mechanical ventilation. In this pilot study, the impact of bronchoscopy was to lead to more frequent antibiotic changes with no change in mortality. Further studies with larger population samples are warranted to confirm these findings.

Ventilator associated pneumonia: quality of nonbronchoscopic bronchoalveolar lavage sample affects diagnostic yield

“…This would support the concept that deeper specimens would be more reliable than upper airway secretions. The use of semiquantitative cultures of tracheal aspirates was as good as deeper samples in one pilot study [39], the group had previously shown that the endotracheal aspirate was not as specific as deeper samples [40]. Therefore, their pilot study may not adequately answer the question of whether invasive specimens are necessary.…”

Ventilator-Associated Pneumonia: Diagnosis, Treatment, and Prevention

“…In the three, randomized, controlled Spanish studies, no differences in mortality and morbidity were found when either invasive (PSB and/or BAL) or QEA techniques were used to diagnose VAP (175,176,186). However, these studies contained relatively few patients (51, 76, and 88 patients) and therefore were not powered sufficiently to demonstrate a difference in mortality.…”

Ventilator‐associated pneumonia

“…Three comparatively small single centre studies comparing mortality in patients with suspected VAP managed on the results obtained by either invasive studies or quantitative analysis of tracheal aspirates failed to find any difference in mortality. 55 58 61 A much larger study involving 413 patients suspected of having VAP suggested that an invasive diagnostic strategy was desirable. 59 Compared with patients who received clinical management, patients who received invasive management had reduced mortality rate at day 14 (16.2% and 25.8%, p = 0.02) and decreased antibiotic use (mean (SD) number of antibiotic free days, 5.0 (5.1) and 2.2 (3.5), p,0.001).…”