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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 9  |  Issue : 1  |  Page : 62-66

Ventilator-associated events: Incidence and mortality in intensive care unit of a superspecialty hospital of North India


Department of Microbiology, G.B. Pant Institute of Postgraduate Medical Education and Research, New Delhi, India

Date of Submission24-Oct-2019
Date of Decision02-Nov-2019
Date of Acceptance14-Nov-2019
Date of Web Publication13-Jan-2020

Correspondence Address:
Dr. Abha Sharma
Department of Microbiology, G.B. Pant Institute of Postgraduate Medical Education and Research, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijhas.IJHAS_96_19

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  Abstract 


INTRODUCTION: The revised definition proposed in 2013 by the Centers for Disease Control and Prevention (CDC) replaced ventilator-associated pneumonia (VAP) surveillance with ventilator-associated event (VAE) surveillance for monitoring both infectious and noninfectious complications in mechanically ventilated patients in intensive care unit (ICU). Few studies have been reported from India using the new VAE surveillance definition.
OBJECTIVE: The objective of the study was to determine and compare the incidence and mortality of VAE in patients on mechanical ventilation in medical versus surgical ICU of a superspecialty hospital.
MATERIALS AND METHODS: All patients on mechanical ventilation for more than 2 days in two ICUs (medical and surgical) were followed daily, and VAE data were collected using a checklist obtained from CDC website (National Healthcare Safety Network VAE Surveillance tool). The incidence and mortality of VAEs were determined. The percentage was used to analyze clinical and demographic data.
RESULTS: A total of 189 patients were followed up over a period of 8 months. The overall VAE rate was 23.7/1000 ventilator days. Ventilator-associated condition (VAC) only (6.7/1000 ventilator days), infection-related VAC (IVAC) (11.57/1000 ventilator days), and possible VAP (PVAP) (5.7/1000 ventilator days). All VAC cases (100%) survived, which was statistically significant (P = 0.0002), and 83.3% of IVAC cases expired, which was also statistically significant (P = 0.0069). However, 77.7% of PVAP cases expired but were not found to be statistically significant (P = 0.2616). The mean duration of mechanical ventilation days and ICU days for VAE cases was 18.5 and 18.6 days, respectively. VAC and IVAC incidence was almost similar in both ICUs; however, the incidence of PVAP was more in medical ICU (9.1/1000 ventilator days) as compared to surgical ICU (1.45/1000 ventilator days), which was found to be statistically significant (P = 0.0044).
CONCLUSION: The new VAE surveillance definition targets many other complications of mechanical ventilation apart from infection/pneumonia in ICU patients. The IVAC subtype of VAE is associated with significant mortality. VAE incidence rates help in guiding the hospitals to plan VAE prevention programs for better patient care.

Keywords: Intensive care units, mechanical ventilation, surveillance, ventilator-associated event, ventilator-associated pneumonia


How to cite this article:
Sharma A, Das M, Mishra B, Thakur A, Loomba PS. Ventilator-associated events: Incidence and mortality in intensive care unit of a superspecialty hospital of North India. Int J Health Allied Sci 2020;9:62-6

How to cite this URL:
Sharma A, Das M, Mishra B, Thakur A, Loomba PS. Ventilator-associated events: Incidence and mortality in intensive care unit of a superspecialty hospital of North India. Int J Health Allied Sci [serial online] 2020 [cited 2020 Apr 6];9:62-6. Available from: http://www.ijhas.in/text.asp?2020/9/1/62/275664




  Introduction Top


Ventilator-associated pneumonia (VAP) is one of the most serious health care-associated infection[1] that occurs after the first 48 h of initiating mechanical ventilation (by endotracheal tube or tracheostomy). Surveillance for VAP first began in 1970 by the Centers for Disease Control and Prevention (CDC) in the National Nosocomial Infections Surveillance System and then later on in the National Healthcare Safety Network (NHSN) from 2006 onward.[2] The complications of mechanical ventilation were monitored by VAP surveillance till 2013 by relying on a combination of clinical, radiological, and microbiological criteria. However, these criteria had limited accuracy and specificity.[3] There are a wide range of clinical conditions that resemble VAP such as acute respiratory distress syndrome, pulmonary edema, tracheobronchitis, and thromboembolic disorders. Furthermore, interpretation of chest X-rays is difficult and expertise is required which most infection control nurses (ICNs) are lacking. Overall, no agreed definition of VAP had been reached for the accurate diagnosis of VAP.[4] Therefore, in 2013, the CDC (NHSN) introduced the concept of ventilator-associated event (VAE) surveillance in the place of VAP. The VAE surveillance definition algorithm includes a broad range of pulmonary complications, both infectious and noninfectious, that may occur in mechanically ventilated patients.[5],[6] This algorithm includes a hierarchy of surveillance targets – ventilator-associated condition (VAC), infection-related VAC (IVAC), and possible/probable VAP (PVAP).[3] This new NHSN surveillance criteria are supposed to provide more objective and specific VAP definition, are for the purpose of surveillance only, and are not meant for the clinical management of patients.[7] At least 2 days of stable or decreasing ventilator settings followed by at least 2 days of increased ventilator settings defines a VAE.[8] This study was done with the aim of assessing the incidence and mortality of VAE in mechanically ventilated patients in the intensive care unit (ICU) of a superspecialty hospital using the new surveillance definition by the CDC.


  Materials and Methods Top


Data collection

This prospective study was conducted in two ICUs (medical and surgical) of a superspecialty hospital over a period of 8 months (October 2018–May 2019). All patients who were on mechanical ventilation for > 2 days were included in the study. VAE data were collected using a checklist obtained from the CDC website (NHSN VAE Surveillance tool). A pro forma was made to collect data on demographic profile, risk factors, and treatment for each patient. The patients were followed up daily till they were extubated or expired. VAEs were identified using the new NHSN VAE surveillance algorithm as follows:

Ventilator-associated condition

It is defined as increase in the daily minimum positive end expiratory pressure (PEEP) of at least 3 cmH2O for at least 2 days or increase in daily minimum fraction of inspired oxygen (FiO2) of at least 20 points for at least 2 day s.

Infection-related ventilator-associated condition

It is defined as any one out of the following four conditions: fever or hypothermia or leukocytosis or leukopenia, and new antimicrobial agent started and continued for ≥4 days.

PVAP

It is defined as isolation of significant count of a pneumonia pathogen from respiratory specimens such as tracheal aspirate, bronchoalveolar lavage, and sputum.

Data analysis

Descriptive analysis of the data was done. Percentage was used to analyze clinical and demographic data collected. The incidence and mortality of VAEs were determined. First, overall VAE rates were estimated (all events meeting VAC definition) per 1000 ventilator days and then VAEs were further subclassified into VAC, IVAC, and PVAP, and their rates per 1000 ventilator days were calculated. The patient characteristics of VAEs were studied that included age, gender, type of ICU, total and mean mechanical ventilator (MV) days, and ICU stay.

Fisher's exact test was done using the GraphPad software (www.graphpad.com/quickcalcs/contingency2/) to calculate statistical significance between categorical data.

The study was conducted with the approval of the ethics committee of the institute.


  Results Top


A total of 189 patients on more than 2 days of mechanical ventilation were followed up over a period of 8 months. Out of these, 37 VAE cases (19.5%) were identified. Overall VAE incidence rate and mortality is shown in [Table 1]. The impact of VAE on mortality was studied and was found to be statistically significant for VAC and IVAC cases. However, although 22% of PVAP cases survived and 77.7% cases expired, statistically, it was not found to be significant (P = 0.2616).
Table 1: Overall ventilator-associated event incidence and mortality

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The demographic profile of VAE cases is shown in [Table 2]. Most cases (32.4%) were above 60 years of age and were from medical ICU (62.1%). The mean duration of mechanical ventilation (MV days) and ICU days for VAE cases was 18.5 and 18.6 days, respectively.
Table 2: Demographic profile of ventilator-associated event cases

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On comparing the VAE incidence and mortality between medical and surgical ICUs [Table 3], out of 110 patients on ventilator in surgical ICU, 14 VAEs were identified, whereas out of 79 patients on ventilator in medical ICU, 23 VAEs were identified. This finding was found to be statistically significant (P = 0.0086). Among VAE cases, the incidence of VAC and IVAC was almost similar in both ICUs; however, the incidence of PVAP was more in medical ICU (9.1/1000 ventilator days) as compared to surgical ICU (1.45/1000 ventilator days), which was found to be statistically significant (P = 0.0044). There was no significant difference in the mortality among VAE cases in both ICUs. However, the mean duration of MV days and ICU days was more in medical ICU (11.7 and 11.2 days, respectively), as compared to surgical ICU where it was 5.8 days only, although this finding was not statistically significant (P = 0.2324).
Table 3: Ventilator-associated event incidence and mortality - surgical intensive care unit versus medical intensive care unit

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  Discussion Top


In this study, the overall VAE incidence and rate were 19.5% and 23.7/1000 ventilator days, respectively. Our VAE rate is lower than that of other studies conducted in India (Kerala) by Vaisakh et al.[9] and Thomas et al.[10] that reported VAE rates of 29.2 and 29.6, respectively. Ever since CDC has introduced the concept of VAE in 2013, several studies have been conducted in Western countries to evaluate the impact of VAE. However, very few studies have been reported in developing and non-Western countries. Recently, a study in Japan has reported a VAE rate of 6.4/1000 ventilator days, which is quite low as compared to that of our study.[11] Among the subtypes of VAE, 27% cases were VAC only (6.7/1000 ventilator days), 48.6% were IVAC (11.5/1000 ventilator days), and 24% were PVAP (5.7/1000 ventilator days). Vaisakh et al.[9] reported 58.3% VACs, 25% IVACs, and 8.3% PVAP. The present study reported more cases of IVAC as compared to their study. VAE is a new surveillance definition. Although it shifts the focus not only to pneumonia but also to other noninfectious condition, it has been observed that VAE surveillance detects few cases of VAP (24% in our study), pooled prevalence of PVAP in study by Fan et al.[3] was 1.1% and 8.3% in another Indian study.[9] VAC will include all events with respiratory worsening only. IVAC includes all events with respiratory worsening due to infection but not confirmed microbiological, whereas PVAP includes all events of IVAC confirmed by microbiological diagnosis. VAE criteria for identifying VAP do not rely on chest X-ray which is used to radiologically diagnose VAP. Therefore, patients who clinically and radiologically look like VAP but do not meet the requirements for stable baseline ventilator settings or worsening gas exchange do not meet the VAE criteria. Furthermore, if respiratory sample is not sent for culture due to any reason (microbiological confirmation not done), then only IVACs are identified, but PVAPs in these infection-related cases may be missed. Hence, some cases of VAP could have been missed using the new VAE surveillance definition.

In our study, majority of the VAE cases were either above 60 years (32.4%) or between 21 and 40 years (29.7%) and 59.4% were female patients as compared to males. While the study in Kerala[9] has reported 42.5% cases between 51 and 65 years and 27.5% above 65 years and 65% of the patients in their study were males, other studies[11],[12] have reported high number of VAE cases in above 65 years' age group and only 24%–25% were female cases. VAEs have a clinical importance. Several studies have reported that VAE is associated with high mortality and prolonged duration of ventilator days.[9],[12],[13],[14] In fact, VAE is also associated with prolonged antibiotic use and longer ICU stay.[15] The total MV days in our VAE cases was 685 days, with a mean of 18.5 days. The mortality for VAC-only cases was significantly low (100% survived), but for IVAC, the mortality was high (83% expired) and PVAP was 77%. This implies that events associated with infection are definitely associated with higher mortality as compared to noninfectious conditions leading to VAE. We have reported more VAE cases (62.1%) from medical ICU as compared to surgical ICU, which was found to be statistically significant. The study conducted in Japan[11] reported higher VAE incidence in surgical ICU. The risk factors for VAE present in patients of medical ICU were mainly depressed level of consciousness, immunosuppression, prolonged antibiotic use, coma, presence of underlying lung disease, neurological disorders, and reintubation. The total duration of mean MV days and ICU stay was also more in medical ICU (11.7 and 11.2 days, respectively), as compared to surgical ICU (5.8 days). Furthermore, it was observed in this study that VAP bundle care compliance was more than 95% in surgical ICU, whereas it was <95% in medical ICU. VAP bundle care in our ICUs includes hand hygiene, head of bed elevation 30°, daily sedation interruption, deep-vein thrombosis prophylaxis, ulcer prophylaxis, oral care with chlorhexidine, subglottic secretion drainage, daily spontaneous breathing trials, and assessment of readiness to wean. Therefore, lower VAE rate is associated with high bundle care compliance as observed in our surgical ICU as compared to medical ICU, which may also mean that preventive strategies for VAP can also help prevent VAEs. Other studies have also found that strategies such as daily awakening/breathing trials and minimizing sedation[8],[16],[17],[18] are protective against VAE. We need to perform furthermore extensive studies to establish the association of low VAE rates and higher compliance with preventive strategies.


  Conclusion Top


The limitation of our study was that we used only the new VAE surveillance definition to identify VAP without using the older VAP surveillance definition, so we could not elucidate the better surveillance method. More studies will be required to prove whether or not new VAE surveillance is beneficial than the older VAP surveillance. Definitely, VAE surveillance does focus on a broader category of patients on mechanical ventilation who suffer from many other complications apart from infection/pneumonia. Better patient care and outcome may be achieved by identifying the noninfectious complications of ventilated patients through VAE surveillance and guiding the hospital in planning VAE prevention programs accordingly.

Acknowledgment

We would like to sincerely thank all our ICNs for helping us in data collection for conducting this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3]



 

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