Patients in intensive care units (ICU) are usually at high risk of mortality not only from their critical illness but also from secondary complication such as nosocomial infection. Nosocomial pneumonia, a common ICU infection, affects 27% of all critically ill patients, where 86% of it is associated with mechanical ventilation .
According to the infectious diseases society of America / American thoracic society (IDSA/ATS) guidelines (2016), hospital-acquired/nosocomial pneumonia (HAP) is pneumonia that occurs 48h or more after admission and did not appear to be incubating at time of admission. On the other hand, VAP is a type of HAP that develops more than 48–72h after endotracheal intubation .
Moreover, VAP occurs in 28% of patients who receive mechanical ventilation, where its rate of occurrence varies with the duration of mechanical ventilation. Estimated rates are 3% per day for the first 5days, 2% per day for days 6–10, and 1% per day after day 10 . The diagnostic clinical Triad for VAP consists of Pulmonary infection signs including fever, purulent secretions, and leukocytosis, together with bacteriologic evidence of pulmonary infection, and radiological suggestion of pulmonary infection .
The mortality rate for VAP ranges between 27 and 76%. Pseudomonas or Acinetobacter pneumonia is associated with higher mortality rates than those associated with other organisms. Studies have consistently shown that a delay in starting appropriate and adequately dosed antibiotic therapy increased the mortality rates . Furthermore, VAP has been associated with prolonged ICU length of stay (LOSICU), and higher costs for medical care since ICUs incur an important part of hospital expenses. Therefore, prevention of VAP could reduce the care utilized during hospitalization and decrease resource utilization and subsequent expenses . The aim of our study was to determine the prevalence of ventilator-associated pneumonia in adult patients in our hospital, as well as to identify the possible complications related to it and to determine its relation to in-hospital prognosis.
2. Patients and methods
This is a prospective, observational, case-control study, conducted at King Fahd hospital, Saudi Arabia during the time period from September 2012 to August 2013. Forty-eight adult (>18 yrs.) patients were enrolled in the study. Inclusion criteria were: hospitalized, intubated and mechanically ventilated more than 48h.
Pneumonia was diagnosed as VAP when it occurs after 48h of endotracheal intubation and mechanically ventilated. The criteria of diagnosis are: new persistent pulmonary infiltrates appearing on chest radiographs and, at least two of following: (1) fever of ≥38°C, (2) leukocytosis of ≥12,000\ mm3, and (3) purulent tracheobronchial secretions. In cases of clinically suspected pneumonia, endotracheal aspirate was sent for microbiology, and the diagnosis of VAP was established with a positive quantitative culture (cut-off point≥106 CFU/ mL).
To analyze the predisposing factors and in hospital morbidity, the following variables were evaluated: age, gender, other co-morbidity (diabetes mellitus, COPD on admission), the clinical diagnosis at time of hospitalization, length of ICU stay, mechanical ventilation days, development of complications and the need for tracheostomy.
2.1. Statistical analysis
Statistical software (SPSS version 9; SPSS; Chicago, IL) was used for data analysis. Case patients were compared with subjects using χ2 test or Fisher Exact Test when appropriate for qualitative variables, and Mann-Whitney U test for quantitative variables. Results are presented as frequency (%) for qualitative variables or mean±SD for quantitative variables. Continuous variables were compared using Student's t test for normally distributed variables. All p value lower than 0.05 were considered significant.
Forty-eight patients were enrolled in the study with a mean age 55±15 (range 27–88 yrs.), 28 male (58.3%). VAP occurred in 17 out of 48 patients (35.4%, VAP group). Comorbidities included diabetes in 24 patients, COPD in 25 patients, CHF in 10 patients, while 5 patients were admitted for post-operative care.
By assessing the risk factors for VAP in mechanically ventilated patients, there was no statistically significant difference between VAP and non-VAP groups regarding the age sex, or underlying comorbidities (Diabetes, COPD, CHF) [Table 1]. On the other hand, the duration of mechanical ventilation (LOV), as well as the length of ICU stay (LOSICU) were significantly higher in the VAP group (P=0.001, 0.0001 respectively).
Complications different significantly among VAP and non-VAP groups, where severe sepsis/septic shock, ARDS, atelectasis and infection with MDR organisms were significantly higher in the VAP group, on the other hand the incidence of pneumothorax and tracheo-bronchitis did not showed significant difference between both groups. Importantly, Tracheostomy use was significantly higher in the VAP group. The overall ICU mortality was 20.8% in all mechanically ventilated patients, however, there was no significant difference regarding the mortality, re-intubation or ICU re-admission between both groups [Table 2].
By evaluating the common infecting organism among all patients, Pseudomonas aeruginosa infection occurred in 11 patients (22.9%), Klebsiella pneumoniae in 4 patients, Staphylococcus aureus in 4 patients, Escherichia coli in 3 patients, others in 4 patients, and no microbiological data in 15 patients. In comparing both groups, only Pseudomonas aeruginosa infection was significantly higher in the VAP group, while other organisms showed no significant difference [Table 3].
Overall incidence of VAP was 35.4% in our study. This figure is high, though comparable to the incidence reported by other investigators [15–58%] .
Such high incidence can be possibly related to the use of preventive strategies and the application of VAP bundle.
In our study the incidence of VAP was 36/1000 ventilator days, and it comparable to most of the ICUs in other developing countries . The explanation for this high incidence in our study could be due to small number of cases and short duration, as compared to other studies which showed lower incidence. Other explanation could be lack of adequate nursing staff which may have adversely affected the quality of care given to patients .
Our study has shown that LOV and LOS ICU were significantly higher in the VAP group. We may imply that the duration of mechanical ventilation significantly increases the incidence of VAP. This is line with an Italian study conducted on 724 adult ICU patients, which confirmed that the incidence of VAP increased from 5% for patients receiving mechanical ventilation for 1day to 69% for those receiving mechanical ventilation for more than 30days . Alternatively, we may also infer, since VAP was detected in the first few days, that significantly increased the LOV, and LOS as a complication.
Importantly, Tracheostomy was significantly higher in the VAP group (17.6%), which again indicates the effect of VAP on the LOV, and in-turn would increase the possibility of Tracheostomy in this subset of patients.
It was suggested in a previous study that patients with VAP appear to have a 2-10-fold higher risk of death compared to ventilated patients without pneumonia . However, our study did not show any significant difference regarding the mortality, re-intubation or ICU re-admission between both groups. Similarly, Tejerina et al., in evaluating more than two thousand patients concluded that VAP was associated with a significant increase in ICU length of stay but no increase in mortality .
By analyzing the differences between the two groups in terms of complications during MV, we observed that the patients with VAP developed severe sepsis/septic shock, ARDS, atelectasis, infection with multi-drug resistant organisms significantly more frequently than those in the non-VAP group. This may be explained by the longer ICU length of stay which exposed the VAP group to higher rate of complications. Ventilator-associated pneumonia increased the duration of mechanical ventilation, the number of complications, as well as the LOSICU and hospital stays. Alternatively, patients who developed those complications became more liable for the development of VAP (an association, whether cause or effect). The greater susceptibility to infection among these patients is justified by their impaired immunological state. Patients with ARDS are also predisposed to pulmonary infection (within 24h of an ARDS diagnosis) between 34% and 70% of the cases, frequently leading to sepsis, multiple organ dysfunction syndrome and death .
Among our studied groups, the isolated Pseudomonas aeruginosa infection was significantly higher in the VAP group (p=0.02), however, there was no difference in other various organisms between both groups. Such distribution of identified pathogens was similar to that observed in National Nosocomial Infections Surveillance (NNIS) system data from 1992 to 1997 and in other studies, including high frequencies of P. aeruginosa and S. aureus.
5. Study limitations
The small sample size in our study, however, the turn-over in our ICU in a developing country was not high enough for a larger number of prospective cases. We could not get microbiologic data in 15 ventilated patients, this was due to insufficient sampling in those patients.
Ventilator associated pneumonia is a common and serious ICU complication, that is associated with a longer ventilation duration, ICU/hospital stay, and increased in-hospital morbidity and mortality which may lead to higher treatment costs. Effective nursing care and application of VAP bundle should be rigorously applied in developing countries for VAP prevention.
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