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


table 1. Impact of the Change in National Health and Safety Network Surveillance Definitions on Burn Intensive Care Unit Ventilator- Associated Pneumonia Events


Jul 2011–Dec 2012 (18 mo)


Ventilator-associated events, no. Total ventilator days Total patient days


Device utilization ratio, device days/patient days Incidence of (P)VAP events/1,000 ventilator days Days from admission to event, d, median (IQR) Days hospitalized, d, median (IQR) Died during hospitalization, no. (%) Age at event, y, median (IQR) Male, no. (%)


Inhalational injury, no. (%)


Common organisms recovered, no. (%)b S. aureus


P. aeruginosa


Enterobacteriacae A. baumannii


4,695


11,148 0.42 4.47


19 (11–43) 73 (55–104) 9 (43)


50 (27–60) 13 (62) 8 (38)


3 (14)


13 (62) 7 (33) 0 (0)


Jan 2013–Jun 2014 (18 mo)


5 18 4,860


10,968 0.43 1.03


15 (5–36) 52 (15–66) 1 (20)


36 (34–77) 0 (0) 0 (0)


1 (20) 1 (20) 1 (20) 1 (20)


NOTE. IQR, interquartile range; VAP, ventilator-associated pneumonia; VAE, ventilator-associated event. aA single patient contributed 2 events but was counted only once for these analyses. bPercentages may not sum to 100 because>1 bacterial species could be collected from a single event.


(including possible VAP) of 2.93 events/1,000 ventilator days.6 We found an incidence of VAE-possible VAP cases ranging from 0.6 to 1.0/1,000 ventilator days over a 4.5-year period, which was much lower than our pre-2013VAPrates. Even though the BICU is our highest risk unit for VAP, we found very few events that met the current VAE-possible VAP definition. Our findings are consistent with other reports suggesting that the new VAE sur- veillance algorithm has low sensitivity for detecting VAP cases as previously defined and likely identifies only select VAP cases.7,8 Arguments supporting a change in the VAP surveillance


definition include that screening ventilator settings for VAE would capture a similar set of complications as VAP but may also provide data that could be used to assess the effectiveness of prevention of noninfectious complications of mechanical ventilation.9 VAE surveillance with automated computer algorithms may be less time-consuming and less subjective than pre-2013 VAP surveillance if the hospital has an electro- nic medical record system that captures ICU data. Possible and probable VAE reduction strategies have been published, such as conservative fluid management, transfusion thresholds, and minimizing sedation.9 Theoretically, these strategies would protect patients against mild VAP that do not meet the strict VAE mechanical ventilation and oxygenation parameters as well as severe possible VAP cases, but the effectiveness of these prevention strategies for VAE is not yet clear. Our infection control department does not yet track


VAC and IVAC routinely (1) because the computerized algo- rithm for this objective measure has not been integrated into our electronic surveillance system, (2) because no specific VAC prevention strategies have been endorsed by the CDC,


and (3) because these events are not classified as healthcare- associated infections. Therefore, we cannot comment on the characteristics of VAC or IVAC in our BICU or on what per- centage of VAC are attributable to possible VAP. Additionally, we do not yet have an automatic surveillance system for detection of VAC, so we may have missed some VAE-possible VAP cases. Manual surveillance has been shown to be less sensitive than automated surveillance for detection of VAE.10 Because these data were collected for infection control purposes, we cannot describe what aspects of the definition change are related to the reduced rate or why the ventilator days were lower during the later period. Low events numbers may have prevented us from detecting differences between groups. The date of event protocol change (from the day all elements were present together to the day the first symptom was present) may have led to more events in 2015 being class- ified as present on admission rather than as healthcare- associated events; however, this change should have primarily affected pre-2013 VAP cases. Lilly et al7 and Chang et al8 both found that not having a period of stability followed by worsening oxygenation was the major reason that most radiographic VAP failed to meet the VAE-probable VAE definition, and we suspect this is also the case in our BICU. Our results are strengthened by the collection of all events


by a single, highly experienced infection preventionist, who strictly followed NHSN surveillance definitions of VAP and VAE-possible VAP without regard for clinical diagnosis of pneumonia. Our VAP bundle has been in effect and consistently implemented in the BICU since 2007, and no additional improvement efforts were implemented over the study periods.


July 2014–Dec 2015 (18 mo)


Pre-2013 VAP VAE-Possible VAP Pre-2013 VAP VAE-Possible VAP 21


2 3,632


10,944 0.33 4.96


6 (4–21)


71a (46–119) 5a (29)


43a (30–64) 11a (65) 7a (41)


10 (56) 3 (17) 6 (33) 0 (0)


3,632


10,944 0.33 0.55


21.5 (5–38)


131 (125–137) 0 (0)


61.5 (59–64) 2 (100) 0 (0)


1 (50) 0 (0)


1 (50) 0 (0)


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