Role of quantitative endotracheal aspirate and cultures as a surveillance and diagnostic tool for ventilator associated pneumonia: A pilot study

Abstract

Accurate diagnosis and appropriate treatment of ventilator associated pneumonia (VAP) is crucial for good outcomes. Endotracheal suctioning is performed in ventilated patients as part of routine care and for tracheal toileting. We evaluated if quantitative endotracheal aspirate (ETA) was a suitable alternative to bronchoalveolar lavage (BAL) for suspected VAP. In addition we assessed if surveillance ETA guided antibiotic selection for subsequent VAP. Prospective study in the surgical intensive care unit (ICU) of a tertiary hospital in India. Two hundred consecutive patients with mean (standard deviation) APACHE II score of 12.3+/-5 and requiring mechanical ventilation beyond 48 hours underwent surveillance ETA cultures. A second ETA and BAL were performed if the patient developed features of VAP. The threshold for microbiological diagnosis of VAP was taken as 10 5 colony forming units/ml (cfu/ml) for ETA and 10 4 cfu/ml for BAL. The sensitivity and specificity of surveillance and concurrent ETA aspirate cultures were compared with BAL cultures. VAP was suspected clinically and corroborated radiologically in 27/177 patients (15.3%). Although microbiological support for VAP was obtained by ETA in 19 patients, bronchoscopy was possible only in 13 patients, 8 of whom had isolates at significant threshold. Of the 16 organisms isolated from BAL, 11 were of significant threshold with 9/11 (82%) BAL isolates having a similar antibiogram to a concurrent ETA. Only one BAL isolate (9%), at significant threshold, was not isolated on a concurrent ETA. On the other hand just 6/11 BAL isolates (55%) had an identical antibiogram to surveillance ETA. BAL had 3 additional isolates (27%) at significant threshold not isolated on surveillance ETA. Concurrent quantitative ETA could substitute BAL cultures for VAP. Surveillance ETA at 48 hours of ventilation does not appear to assist with antibiotic selection for a subsequent VAP.