infection control & hospital epidemiology july 2017, vol. 38, no. 7 concise communication


From VAP to VAE: Implications of the New CDC Definitions on a Burn Intensive Care Unit Population


Anne M. Lachiewicz, MD, MPH;1 David J. Weber, MD, MPH;1,2 David van Duin, MD, PhD;1 Shannon S. Carson, MD;3 Lauren M. DiBiase, MS;2 Samuel W. Jones, MD;4,5 William A. Rutala, MS, MPH, PhD;2 Bruce A. Cairns, MD;4,5 Emily E. Sickbert-Bennett, PhD, MS1,2


Ventilator-associated pneumonia (VAP) is a frequent complication of severe burn injury. Comparing the current ventilator-associated event-possible VAP definition to the pre-2013 VAP definition, we identified considerably fewer VAP cases in our burn ICU. The new definition does not capture many VAP cases that would have been reported using the pre-2013 definition.


Infect Control Hosp Epidemiol 2017;38:867–869


or extensive exfoliating skin conditions. Surveillance for hospital- associated respiratory infections was prospectively collected over a 4.5-year period (July 2011–December 2015) in accordance with NHSN criteria, and these data were entered into an electronic database. Positive microbiological cultures or nursing notifica- tion prompted infection preventionist review of potential cases according to the pre-2013 VAP algorithm, starting with physician-confirmed imaging review or according to the VAE algorithm starting with VAC criteria. From July 2011 to December 2012, the pre-2013 NHSN definition was used to identify VAP cases. From January 2013 to June 2014, the new VAE algorithm was used to identify VAE-possible VAP cases. From July 2014 to December 2015 both definitions were used simultaneously to identify cases. The results are displayed as median and interquartile range (IQR) for continuous variables and counts and percentages for categorical variables. Incidence was calculated as infections/1,000 ventilator days. Denominator data were collected following Centers for Disease Control and Prevention criteria.4 Using Stata release 13 (StataCorp LP, College Station, Texas), univariate analyses were performed using the Wilcoxon rank sum and Fisher exact tests, and a 2-sided P value<.05 was considered significant.


Ventilator-associated pneumonia (VAP) is a frequent com- plication among acute burn patients. In 2013, the National Health and Safety Network (NHSN) implemented a new adult surveillance algorithm to capture a variety of ventilator- associated events (VAE), including possible VAP cases.1 This algorithm was intended to enhance the reliability and credi- bility of the surveillance definition within the critical care and infection prevention communities by capturing more general, objective measures of conditions and complications occurring in patients on mechanical ventilation.2 The most notable changes are that (1) radiographic evidence


of pneumonia is no longer a criterion for possible VAP cases and (2) that VAE are further defined as ventilator-associated condi- tions (VAC), infection-related ventilator-associated complica- tions (IVAC), and possibleVAPcases. In contrast to the pre-2013 VAP algorithm,3 a possible VAP case in the new 2013 VAE algorithmmust alsomeet uniqueVACand IVAC criteria, such as worsening oxygenation and need for new antibiotic therapy.1 Our burn intensive care unit (BICU) patients are often


maintained on stable ventilator settings without aggressive weaning until surgeries are completed. Therefore, we hypo- thesized that VAP incidence would be lower using the new VAE-possible VAP surveillance definitions, and we assessed the effect of the changed definition on our BICU VAP rates.


methods


Our institution is an 850-bed tertiary-care facility including a 21-bed ICU for severely ill adult and pediatric patients with burns


results


Comparing the new NHSN definition for VAE–possible VAP to the pre-2013 VAP definition, we identified substantially fewer VAP cases with a lower VAP incidence over 2 different time periods (Table 1). Compared to the incidence of 4.47 VAP/1,000 ventilator days during July 2011–December 2012, the incidences of VAE-possible VAP were 1.03 during January 2013–June 2014 and 0.55 during July 2014–December 2015. Among cases screened from July 2014 to December 2015 that


failed to meet the VAE-possible VAP definition by any aspect of the VAE algorithm, our BICU infection preventionist identified 18 VAP cases meeting the pre-2013 criteria resulting in an inci- dence of 4.96 VAP/1,000 ventilator days. Neither VAE-possible VAP case from this period met the pre-2013 VAP definition. Two patients contributed 2 events during this period. We did not identify any statistically significant differences


between pre-2013 VAP and VAE-possible VAP cases by median age, sex, inhalational injury, days from admission to event, days of hospitalization, or hospital mortality.


discussion


In 2012, the NHSN reported a pooled mean VAP incidence in BICUs of 4.4 infections/1,000 ventilator days, which was similar to our BICU rate during the same time period.5 Although VAE reporting is not mandated, 36 BICUs reported data to the NHSNin 2014 with a pooledmean incidence of 6.55 VAE/1,000 ventilator days and a pooled mean incidence of IVACs


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