Chest
Volume 113, Issue 2, February 1998, Pages 412-420
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Clinical Investigations in Critical Care
The Influence of Mini-BAL Cultures on Patient Outcomes: Implications for the Antibiotic Management of Ventilator-Associated Pneumonia

https://doi.org/10.1378/chest.113.2.412Get rights and content

Study objective

To determine the influence of mini-BAL culture results on subsequent changes in antibiotic therapy and patient outcomes.

Design

Prospective, single-center, cohort study.

Setting

Medical ICU of Barnes-Jewish Hospital, St. Louis, a university-affiliated teaching hospital.

Patients

One hundred thirty mechanically ventilated patients undergoing mini-BAL for suspected ventilator-associated pneumonia (VAP).

Interventions

Mini-BAL, prospective patient surveillance, and data collection.

Measurements and results

Sixty (46.2%) patients had mini-BAL cultures that yielded at least one pathogen potentially accounting for the clinically suspected episode of VAP (64 bacterial, 3 viral, 2 fungal). Among the 60 patients with microbiologically positive mini-BAL cultures, 44 (73.3%) were classified as receiving inadequate antibiotic therapy (ie, identification of a microorganism resistant to the prescribed antibiotic regimen). Prior antibiotic administration or its absence remained unchanged in 51 (39.2%) patients based on the mini-BAL culture results, while in another 51 (39.2%) patients, antibiotic therapy was either begun (n=7) or the existing antibiotic regimen was changed (n=44), and in the remaining 28 (21.6%) patients, antibiotic therapy was discontinued altogether. The hospital mortality rates of these three groups were statistically different: 33.3%, 60.8%, and 14.3%, respectively (p<0.001). The most common pattern of antibiotic resistance resulting in an antibiotic change following mini-BAL was the identification of a Gram-negative bacteria resistant to a prescribed third-generation cephalosporin in 23 of 44 (52.3%) patients. Twenty-one of these 23 patients (91.3%) received prior therapy with a cephalosporin class antibiotic during the same hospitalization. Having an immunocompromised state (adjusted odds ratio [OR]=2.45; 95% confidence interval, 1.56 to 3.85; p=0.047) and the presence of a pathogen in the mini-BAL culture resistant to the empirically prescribed antibiotic regimen (adjusted OR=3.28; 95% confidence interval, 2.12 to 5.06; p=0.006) were identified as risk factors independently associated with hospital mortality by logistic regression analysis.

Conclusions

These data suggest that antibiotic selection prior to obtaining the results of lower airway cultures is an important determinant of outcome for patients with suspected VAP. A delay in initiating adequate antibiotic therapy was associated with a greater mortality. Therefore, the initial selection of antibiotics for the empiric treatment of VAP should be broad enough to cover all likely pathogens, including antibiotic-resistant bacteria. This appears to be especially important in patients having received prior antibiotics.

Section snippets

Study Location and Patients

The study was conducted at a university-affiliated teaching hospital, Barnes-Jewish Hospital (900 beds). During a 12-month period (February 1996 through February 1997), all patients receiving mechanical ventilation within the medical ICU (19 beds) of Barnes-Jewish Hospital were evaluated. All patients with suspected VAP undergoing mini-BAL were entered into the study. Patients were excluded if they were younger than 18 years and if they had massive hemoptysis. The study was approved by the

Patients

A total of 130 consecutive patients requiring mechanical ventilation with suspected VAP were evaluated using mini-BAL (Tables 1 and 2). The mean age of the patients was 52.3±16.8 years (range, 18 to 92 years). Sixty-eight (52.3%) patients were men and 62 (47.7%) were women. The mean APACHE II score of the entire study cohort was 17.3±5.0 (range, 3 to 29). The ICU admitting diagnoses of the study patients included sepsis (n=19), complications of therapy for leukemia, lymphoma, or solid cell

Discussion

We found a statistically significant association between patients receiving inadequate antibiotic therapy (ie, the identification of a pathogen from mini-BAL resistant to the prescribed antibiotic regimen) and subsequent hospital mortality (Fig 2). Multiple logistic regression analysis demonstrated that the risk of hospital mortality was more than three times as great among patients with inadequate antibiotic therapy compared to patients who received adequate antibiotic therapy to treat the

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    This research was supported in part by grants from the American Lung Association of Eastern Missouri and Merck and Co Inc.

    revision accepted July 15.

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