The Incidence of Ventilator-Associated Infections in Children Determined Using Bronchoalveolar Lavage.

Abstract

Hospital-acquired infections are a major contributor to inpatient morbidity, mortality, and health care costs. Ventilator-associated pneumonia (VAP) is among the most common. It is associated with longer duration of mechanical ventilation (MV), longer intensive care unit stays, increase in cost per case of VAP of at least $40 000, and over 2-fold increased risk of mortality.1,2 Hospital rates of VAP are subject to mandated reporting and measured against national benchmarks. However, because the definition of VAP is complex and includes subjective signs and symptoms, the reported incidence in children varies widely from 0.3 to 45.1 cases per 1000 ventilator days.3 VAP may not include all clinically important infections associated with MV.4 Another infection, ventilator-associated tracheobronchitis (VAT), has been described using varying definitions with unclear clinical significance. The incidence of VAT in pediatric intensive care unit (PICU) populations has been reported at 3.4% to 7.3% of ventilated patients, and as high as 21.2% in trauma patients.5-9 VAT has been associated with longer duration of MV and length of stay but not increased mortality.5-7 Variable definitions have been used in studies of VAT, but generally include clinical signs of respiratory infection in the absence of pneumonia on chest radiograph combined with a positive respiratory culture.8,9 Recent studies of VAT in pediatrics have all used a definition based on the Centers for Disease Control and Prevention/National Healthcare Safety Network (CDC/NHSN) definition of “lower respiratory tract infection other than pneumonia” and applied it to children on MV.5-7,10 Definitions of VAT, and those of VAP, are complicated by their reliance on poor interpretability and subjectivity of data including clinical signs and chest radiographs. Microbiologic testing is complicated due to the lack of standard microbiologic methods.3 Respiratory specimens can be obtained by bronchoscopic or non-bronchoscopic bronchoalveolar lavage (BAL), by protected specimen brush, or by endotracheal aspirate (ETA) via new or inline suction catheters. ETA may be preferred due to perceived safety, feasibility, and cost concerns.4 However, validity of cultures obtained by ETA may be questioned due to bacterial colonization of endotracheal tubes. Quantitative bacterial cultures may improve specificity of ETA cultures for infection over colonization, and a threshold of >105 cfu/mL has been suggested.9 Publications on VAT have invariably used ETA as the method to obtain specimens, but have varied in the use of quantitative culture. In our institution, BAL is used for the routine evaluation of ventilator-associated infections including VAP and VAT. Surveillance cultures and ETA are not performed due to concerns of interpretability of results. Because of this, we are in a unique position to provide the first report of BAL results in a large cohort of PICU patients. We hypothesized that VAP represents only a small portion of positive BALs, suggesting that other potentially significant ventilator-associated infections are not well characterized.