ORIGINAL ARTICLE |
https://doi.org/10.4103/ijrc.ijrc_19_20 |
Comparative Study of Demographic Profile, Mortality, Risk Factors, and Bacteriological Profile of Respiratory Isolates from Ventilated Patients: Ventilator-Associated Event versus NonVentilator-Associated Event Cases
Departments of Microbiology, GIPMER, New Delhi, India
E-mail: abha_sh79@rediffmail.com
Abstract
Introduction: Ventilator-associated pneumonia (VAP) rate has long been considered a quality indicator (QI) in intensive care units (ICUs) for mechanically ventilated patients. However, ever since the Centers for Disease Control and Prevention (CDC) redefined VAP as ventilator-associated events (VAEs), its validity as a tool for use in quality assurance needs to be assessed. Aim: The aim of the study was to identify VAE rate in ICU, compare the demographic and respiratory isolate profile and mortality with non-VAE cases, and identify risk factors for VAE. Materials and Methods: All ICU patients on mechanical ventilation (MV) for >2 days were followed prospectively. VAE data were collected using a checklist obtained from the CDC website (the National Healthcare Surveillance Network VAE surveillance tool). The demographic profile, risk factors, and treatment for each patient were recorded in a proforma. VAE rates were estimated per 1000 ventilator-days. Results: The overall VAE rate was 38.1/1000 MV days. Among VAE subtypes, 18.7% were ventilator-associated condition (VAC), 43.7% were infection-related VAC (IVAC), and 37.5% were possible VAP (PVAP). Survival rate was 100% for patients with VAC alone, whereas only 14.2% and 16.6% of patients survived with IVAC and PVAP, respectively. No significant association was found between age, gender, mortality, bacterial isolate, and VAE cases. Depressed level of consciousness, immunosuppression, antibiotic use, and reintubation were significant risk factors associated with VAE cases (P = 0.0001). Conclusion: There is no significant difference observed between VAE and non-VAE cases regarding demographic profile, respiratory bacterial profile, and mortality. More research is required to establish the role of VAE as a QI for patient care in ICUs.
Keywords: Intensive care unit, nonventilator-associated events, risk factors, ventilator-associated events
How to cite this article: Sharma A, Das M, Mishra B, Loomba PS. Comparative study of demographic profile, mortality, risk factors, and bacteriological profile of respiratory isolates from ventilated patients: Ventilator-associated event versus nonventilator-associated event cases. Indian J Respir Care 2021;10:66-9.
Received: 14-03-2020
Revised: 13-07-2020
Accepted: 06-08-2020
Published: 31-01-2021
INTRODUCTION
In 2013, the Centers for Disease Control and Prevention (CDC) redefined ventilator-associated pneumonia (VAP) as ventilator-associated events (VAEs) and as a result the National Healthcare Surveillance Network (NHSN) introduced the new VAE surveillance definition algorithm that recognized a broader range of pulmonary complications, both infectious and noninfectious, that occurred in mechanically ventilated adult patients.[1] The clinical definition of VAP lacks sensitivity, specificity, objectivity and is less accurate. The newer criteria are more specific and objective.[2] Studies done so far have shown that most of the VAEs are due to pneumonia, atelectasis, acute respiratory distress syndrome (ARDS), and fluid overload.[3] A VAE is defined as 2 days of stable or decreasing ventilator settings, followed by 2 days of increased ventilator settings (ventilator-associated condition [VAC]). Further subclassification of VAE includes infection-related VAC (IVAC) and possible VAP (PVAP).[1,4] Hence, using the new VAE surveillance criteria, we conducted this study with the aim of identifying VAE rate in our intensive care units (ICUs) and comparing the demographic characteristics and bacteriological profile of isolates obtained from respiratory samples of VAE cases with the non-VAE cases.
MATERIALS AND METHODS
This prospective, observational study was conducted with the approval of the ethics committee of the institute after obtaining consent as per institutional policy. All patients who were on mechanical ventilation (MV) for >2 days in the ICU were followed up prospectively till they were extubated or expired. The VAE data were collected using a checklist obtained from the CDC website (NHSN VAE Surveillance tool). Demographic profile, risk factors, and treatment for each patient were recorded in a proforma. VAEs were defined according to the new NHSN VAE surveillance algorithm:
- VAC: Increase in the daily minimum positive end- expiratory pressure of at least 3 cmH2O for at least 2 days or increase in the daily minimum fraction of inspired oxygen of at least 20 points for at least 2 days
- IVAC: Any one of the following four criteria - fever or hypothermia, leukocytosis, or leukopenia, and new antimicrobial agent started and continued for >4 days
- PVAP: Isolation of significant count of a pneumonia pathogen from respiratory specimens such as tracheal aspirate, bronchoalveolar lavage, and sputum.
Data were analyzed using the GraphPad software (www.graphpad.com/quickcalcs/contingency2/) to calculate statistical significance between categorical data by Fisher's exact test and odds ratio for risk factor analysis. VAE rates were estimated per 1000 ventilator-days.
RESULT
Over a period of 6 months, a total of 122 cases on MV were followed up. Out of the 122 cases, 16 VAE cases were identified. The demographic profile and mortality of VAE cases were compared to those of non-VAE cases (patients who were on ventilator but did not develop any VAE) [Table 1]. No significant association was found between age, gender, mortality, and VAE cases. However, the mean total MV days and ICU days were very less for non-VAE cases (5.3 and 8.3, respectively) as compared to VAE cases (26.1 and 27.5, respectively). The overall VAE rate was 38.1/1000 MV days [Table 2]. Among VAE cases, 68.7% of patients expired, whereas 31.2% of patients survived. Among subtypes of VAE, 18.7% were VAC, 43.7% were IVAC, and 37.5% were PVAP. Survival rate was 100% for patients with VAC alone, whereas only 14.2% and 16.6% of patients survived with IVAC and PVAP, respectively.
| Parameter | VAE (n) | Non-VAE (n) | P |
| Total cases 122 | 16 | 106 | |
| Age (years) | |||
| <20 | 3 | 27 | 0.7585 (NS) |
| 21-40 | 5 | 25 | 0.5383 (NS) |
| 41-60 | 3 | 32 | 0.5536 (NS) |
| >60 | 5 | 22 | 0.3449 (NS) |
| Gender | |||
| Male | 5 | 56 | 0.1781 (NS) |
| Female | 11 | 50 | |
| ICU | |||
| Medical | 9 | 35 | 0.0943 (NS) |
| Surgical | 7 | 71 | |
| Total MV days (mean) | 419 (26) | 567 (5) | |
| Total ICU days (mean) | 441 (27) | 889 (8) | |
| Mortality, n (%) | |||
| Survival | 5 (31.2) | 33 (31.1) | 1.0000 (NS) |
| Expired | 11 (68.7) | 73 (68.8) |
VAE: Ventilator-associated event, ICU: Intensive care unit, NS: Not significant, MV: Mechanical ventilation
| Total (%) | Rate (per 1000 MV days) | Mortality, n (%) | ||
|---|---|---|---|---|
| Survived | Expired | |||
| VAE | 16 (13.1) | 38.1 | 5 (31.25) | 11 (68.75) |
| VAC | 3 (18.7) | 7.1 | 3 (100) | 0 |
| IVAC | 7 (43.7) | 16.7 | 1 (14.2) | 6 (85.7) |
| PVAP | 6 (37.5) | 14.3 | 1 (16.6) | 5 (83.3) |
VAC: Ventilator-associated condition, IVAC: Infection-related VAC, VAE: Ventilator-associated event, PVAP: Possible ventilator-associated pneumonia, MV: Mechanical ventilation
| Total organism isolated (n=47) | VAE (n=16) | Non-VAE (n=31) | P |
|---|---|---|---|
| Polymicrobial | 4 | 7 | 1.0000 (NS) |
| Monomicrobial | 12 | 24 | |
| Klebsiella spp. | 11 | 16 | 0.3547 (NS) |
| Pseudomonas spp. | 4 | 9 | 1.0000 (NS) |
| Acinetobacter spp. | 3 | 5 | 1.0000 (NS) |
| Escherichia coli | 0 | 2 | 0.5412 (NS) |
| Staphylococcus aureus | 1 | 1 | 1.0000 (NS) |
| Enterococcus spp. | 0 | 1 | 1.0000 (NS) |
NS: Not significant, VAE: Ventilator-associated event
The bacterial profile [Table 3] of respiratory samples was analyzed from both VAE and non-VAE cases. Among non-VAE cases, respiratory samples were cultured for only 31 cases, whereas all 16 VAE cases had their respiratory samples cultured. No significant association was found between VAE and non-VAE cases with regard to bacterial isolate. The most common isolate was Klebsiella spp., followed by Pseudomonas spp. in both cases. Almost all strains were sensitive to quinolones, aminoglycosides, piperacillin-tazobactam, carbapenems, and colistin. Acinetobacter spp. were sensitive only to colistin and tigecycline. Respiratory isolates specifically from PVAP cases are shown in Table 4.
Depressed level of consciousness, immunosuppression, antibiotic use, and reintubation were significant risk factors associated with VAE cases [Table 5].
DISCUSSION
In this study, the incidence and characteristics of VAE in ICU have been described and compared with that of the non-VAE cases. The patients in the ICU were nonsurgical and mainly had neurological disorders. The overall VAE rate in ICU reported in this study was 38.1/1000 ventilator-days. This finding is very high as compared to a study done in a Japanese ICU, where the VAE rate was only 6.4/1000 ventilator-days.[5] Another study done by Zhu et al. reported a VAE rate of 11.1/1000 ventilator-days.[6] However, a study conducted in Kerala, India, also reported a high VAE rate of 29.2/1000 ventilator-days.[7] Another study conducted in New Delhi reported a low VAE rate of 11.8/1000 ventilator-days as compared to this study.[8] Thomas et al. reported a VAE rate of 29.6/1000 ventilator-days in another study, also done in Kerala, India.[9]
Very few studies have been done in India using the new CDC VAE surveillance criteria. Most of the researches are on VAP rates (old surveillance criteria). The most common subtype of VAE reported in this study was IVAC (43.7%). There was no significant association between mortality and VAE cases. Around 31% of mortality was seen in both categories. Other authors have reported that the presence of VAE was related to mortality and that higher mortality is seen in VAE cases compared to non-VAE cases.[6‣8] Among the subtypes of VAE, the survival rate for VAC alone subtype was 100%, whereas only 14.2% and 16.6% of patients survived with IVAC and PVAP, respectively, in this study. The study conducted in a Japanese ICU, however, observed a tendency toward higher mortality with all the three subtypes, with no difference among them.[5] Like mortality, no significant association was found between demographic profile and VAE cases. However, other studies have reported male gender to be significantly associated with VAE, whereas age had no significant association with VAE cases.[5,6] In the present study, although mortality had no significant association with VAE, it was observed that the mean total MV days and ICU days were very less for non-VAE cases (5.3 and 8.3, respectively), whereas for VAE cases, it was 26.1 and 27.5 days, respectively. Similar findings have been reported by other studies also.[5‣7] This implies that VAE definitely increases the duration of hospital stay and as a consequence, increases the economic burden on the hospital and the patient.
| Organism | Total |
|---|---|
| Klebsiella spp. | 3 |
| Acinetobacter spp. | 1 |
| Pseudomonas spp. | 2 |
The significant risk factors for VAE identified in this study were depressed level of consciousness, immunosuppression, antibiotic use, and reintubation (P = 0.0001). Lewis et al. in their research have found significant risk factors for VAE, especially VAC and IVAC. They observed that positive fluid balance, mandatory mode of ventilation, and use of drugs such as benzodiazepines, opioids, and muscle relaxants are risk factors for IVAC.[10] Sedation and depressed level of consciousness increase the chances of reintubation and aspiration and prolong the duration of MV, thus increasing the risk of VAE.[10,11] Several other studies have also found that deep and sustained sedation, sedation with benzodiazepines and propofol, positive fluid balance, packed red blood cell transfusions, and high-tidal volume ventilation are all risk factors for VAE.[12‣15] Hence, in order to prevent VAEs, certain practices need to be followed in ICUs, which will help in minimizing the duration of MV, avoiding intubation in patients and preventing conditions such as pneumonia, volume overload, and ARDS, leading to VAE.[3]
Klebsiella spp., Pseudomonas spp., and Acinetobacter spp. were the common bacterial isolates in the respiratory specimens of both VAE and non-VAE cases. The isolates were mostly sensitive to all antibiotics except Acinetobacter spp., which was sensitive only to colistin and tigecycline. Klebsiella spp. was the most common isolate in PVAP cases. Other studies have reported Acinetobacter spp. and Staphylococcus aureus as the most common organisms causing VAP.[16,17] Most of them are multidrug-resistant pathogens. Magill et al. in their research have observed S. aureus, Pseudomonas aeruginosa, Klebsiella spp., and Escherichia coli as common pathogens causing PVAP.[18] Out of these, 37.3% were methicillin-resistant S. aureus, 31.1% were carbapenem-resistant Pseudomonas, and 14% were carbapenem-resistant Klebsiella spp. Another study in India reported Acinetobacter spp. as a common isolate from VAE cases.[8]
| Risk factor | VAE (n=16) | Non-VAE (n=106) | P | OR (95% CI) |
| Mean prolonged duration of ICU stay (days) | 18.5 | 5.6 | ||
| Depressed level of consciousness | 14 | 25 | 0.0001 (S) | 22.68 (4.8234-106.6422) |
| Presence of chronic lung disease | 3 | 2 | 0.0160 (S) | 12 (1.8314-78.6291) |
| Prolonged use of antibiotic in the preceding 90 days | 12 | 10 | 0.0001 (S) | 28.8 (7.8047-106.2740) |
| Immunosuppression | 15 | 41 | 0.0001 (S) | 23.7805 (3.0258-186.8939) |
| Sedation | 11 | 55 | 0.4169 (NS) | 2.0400 (0.6631-6.2756) |
| Reintubation | 7 | 2 | 0.0001 (S) | 40.4444 (7.2952-224.2231) |
VAE: Ventilator-associated event, ICU: Intensive care unit, OR: Odds ratio, CI: Confidence interval
CONCLUSION
VAE increases cost of hospital stay with prolong MV and ICU days has been established. There is no significant difference with respect to age, gender, mortality, and respiratory isolate profile between VAE and non-VAE cases. Therefore, whether VAE should be considered a potential quality indicator for improving patient outcome in ICUs is uncertain, especially in ICUs where patients are at high risk due to comorbidities, immunosuppression, or depressed levels of consciousness and are expected to have a poor outcome. Larger, similar studies need to be done in order to assess the usefulness of such data for improving patient care and safety.
Acknowledgment
The authors would like to sincerely thank all the ICUs of the hospital for assisting in this study with special reference to nursing officers Sini and Dimple.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest
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