O10 – Screening for Ventilator-Associated Pneumonia in the Surgical Intensive Care Unit: Single-Institution Analysis of 1,013 Bronchoalveolar Lavage
Author(s):
Background: Refinement of criteria for both screening and initiation of empiric therapy in ventilator-associated pneumonia (VAP) will minimize antibiotic overuse. The aim of this study was to evaluate critically our current screening tools in order to develop evidence-based algorithms.
Hypothesis: Clinical and Gram stain (GS) variables used traditionally to screen for VAP have favorable test performance characteristics.
Methods: Bronchoalveolar lavage (BAL) cultures obtained from surgical intensive care unit patients at attending discretion were abstracted (2009-2012). VAP was defined as ≥10^5 cfu/mL (not on antibiotics) and ≥10^4 cfu/mL (on antibiotics). The clinical pulmonary infection score both without (CPISclinical) and with (CPISclinical+GS) GS results was calculated. Data: median (range) or number (%). Stats: Wilcoxon rank, Fischer’s exact, receiver operator curve area under the curve (ROC AUC) and multivariable logistic regression. α=0.05.
Results: 1,013 lower respiratory tract cultures from 492 patients were analyzed; age 48 years (18-88), 823 (81.2%) from male patients and 719 (71.0%) from trauma patients. Number of respiratory cultures per patient was 2 (1-10) and days ventilated 11 (1-109). 310 of 492 patients (62.4%) had at least one episode of VAP. Both CPISclinical and CPISclinical+GS had poor discrimination for VAP (ROC AUC 0.55 and 0.66, respectively). Sensitivity of CPISclinical using a threshold of > 6 was 21%; the lowest threshold for CPISclinical for which the sensitivity was at least 85% was 3. The highest sensitivity among the individual CPIS components was new CXR infiltrate (91.1%). Among cultures sent during the early VAP window (days intubated <5), organisms on GS had a sensitivity of 93.3%. CPISclinical, CPISclinical+GS, organisms, and neutrophiles on GS all became less accurate in the late VAP window and when screening for recurrent VAP. Every case of VAP had at least one of the following 1) fever; 2) new CXR infiltrate or 3) organisms on GS (sensitivity=100%).
Conclusions: In this series, traditional screening tools for VAP missed over one half of microbiologically-confirmed cases. Screening based on either new CXR infiltrate or fever yielded an acceptably high sensitivity. The only scenario identified in which empiric antibiotics could be withheld safely was the absence of organisms on GS in the early VAP window.