Ventilator Associated Pneumoniaina Medical Intensive Care Unit: Incidence, Risk factors and Mortality

BACKGROUND: Ventilator Associated Pneumonia (VAP) increases hospital costs, lengthens the hospital length of stay, and significantly contributes to patients discomfort, morbidity, and mortality. The aim was to look at the patient characteristics, microbiological profile and in-hospital mortality in adults receiving mechanical ventilation. METHODOLOGY: In a prospective observational study we enrolled patients aged more than 12 years, with medical-illness and were receiving mechanical ventilation. Patients intubated for >48 hours were analysed for VAP. Variables were collected, observed and analysed. Tracheo-bronchial aspiration and microbiological analysis was done. We used Students t test to compare means, Chi-square test for proportions and Mann-Whitney test for medians. RESULTS: Of the 837 patients who underwent intubation and mechanical ventilation during the study period, 298 patients were ventilated for 48 hours or more. The incidence of VAP was 37.6%. Of the 298 patients, 241 (81% [95% CI 76%- 85%]) died in the hospital. The median length of stay was 6(IQR 4–12) days. The median APACHE II score of those who died was numerically and statistically significantly higher compared to those who survived [16 (IQR 11–20.5) vs. 12 (8-16)]; p = 0.001. The most common pathogen associated with VAP was Acinetobacter baumannii. The independent predictors of mortality in mechanically ventilated patients were Age and APACHE II score. CONCLUSION: The incidence and overall mortality due to VAP is high. VAP is an important problem in ICU settings and requires prompt care. The most common pathogens causing VAP were Acinetobacter baumannii and Pseudomonas aeruginosa and were associated with a high fatality rate. INTRODUCTION: Hospital-acquired pneumonia (HAP) is one of the leading cause of death among patients with hospital-acquired infections. Ventilator-associated pneumonia (VAP) has an incidence estimated of 10 to 25 percent and an all-cause mortality of 25 to 50 percent.(1) Early diagnosis of VAP is important because prompt and appropriate treatment can be lifesaving.(2) About 50% of the antibiotics administered in ICUs are for treatment of VAP.(3) VAP increases hospital costs, lengthens the hospital length of stay, and significantly contributes to patients discomfort, morbidity, and mortality.[4] As an example, two studies had estimated that VAP prolongs the length of mechanical ventilation by 7.6 to 11.5 days and prolongs hospitalization by 11.5 to 13.1 days compared with similar patients without VAP.(4, 5) Currently there is no valid, reliable definition for VAP, and even the most widely-used VAP criteria and definitions lack accuracy. Clinical Pulmonary Infection Score (CPIS) have been suggested to identify mechanically ventilated patients at high risk of developing VAP.(6) A score of more than 8 was found to have a sensitivity of 80%, and specificity of 80%.(3) An another study comparing the Acute Physiology and Chronic Health Evaluation II (APACHE II) and CPIS scores for the predicting 30-day mortality in patients with VAP, APACHE II had better discrimination for predicting 30- day mortality in patients with VAP, with area under curve 0.808 (95% CI)0.704–0.912, p < 0.001).(7)Previous studies have shown that appropriate antimicrobial treatment of patients with VAP significantly improves outcome.(8) Because local epidemiology, etiology, case mix, risk factors and resistance patterns are key determinants of the success or failure of treatment, it is important that the physicians caring for mechanically ventilated patients must use these data when they choose an antibiotic for their patients suspected to have VAP. Published data from India emphasizes the importance of identifying the local microbiological flora and sensitivity patterns for rational treatment of VAP.(9) We designed this study to look at the patient characteristics, microbiological profile and in-hospital mortality in adults receiving mechanical ventilation for medical illnesses at a teaching hospital in Maharashtra. SUBJECTS AND METHODS: SETTING: We conducted a prospective observational study in the adult Medical Intensive Care Unit (ICU) of a teaching not-for-profit hospital in Maharashtra. Patients were eligible for inclusion if they were aged more than 12 years, had a medical-illness as the cause of hospitalization, and were receiving mechanical ventilation. Patients were excluded if they had any one of the following—patients intubated from another hospital and referred to us; patients receiving mechanical ventilation for less than 48 hours. DATA COLLECTION: At enrollment, we collected data on the baseline variables: age, sex, date of hospital and ICU admission, the severity of illness score (Acute Physiology and Chronic Health Evaluation [APACHE II] score), and diagnosis at admission. Laboratory parameters included complete blood counts, serum creatinine, electrolytes, chest radiographs, Ultrasound of abdomen, Computed Tomography scans (wherever applicable) and arterial blood gas (ABG) analysis was noted at the time of evaluation. We used the definition set by Centre for Disease Control (CDC) and Prevention National Healthcare Safety Network (NHSN) for defining VAP. APACHE II score was calculated by using the values of the following variables age, temperature, heart rate, respiratory rate, mean arterial pressure, serum sodium, potassium, creatinine, hematocrit, Arterial pH, white cell count, Glasgow coma scale, A-A gradient or PaO2. It was computed within 24 hours of admission. The score ranges from 0 to 71; the higher score, more severe disease and a higher risk of death. The Clinical Pulmonary Infection Score (CPIS) was calculated by collecting data on six variables: tracheal secretions, chest radiograph infiltrates, temperature, white cell count, PAO2/FIO2, and endotracheal aspirate cultures.(8) The clinical pulmonary infection score of >6 was considered as highly significant of VAP. Centers of Disease Control (CDC) Atlanta guidelines were used to calculate Ventilator Associated Condition (VAC), Infection Related Ventilator Associated Complication (IVAC), Possible and Probable Ventilator Associated Pneumonia. As a part of our ICU protocol, we provided standard ventilator care which includes VAP bundle (head end elevation, prophylaxis for peptic ulcer, deep vein thrombosis prophylaxis, and daily sedation hold). Patients were ventilated for indications such as an acute respiratory failure, inadequate oxygenation or ventilation, and airway protection in a patient with depressed mental function. Tracheo-bronchial aspiration was performed by advancing a catheter through the endotracheal tube until resistance was met and then applying suction. Samples were sent to the microbiology laboratory within 1 hour for microbiological analysis. Gram-staining and culture were performed on all respiratory samples and antibiotic sensitivity and resistance patterns were noted. All included patients were followed up daily to study their clinical progress and outcomes. The duration of mechanical ventilation and hospital stay, as well as the status on discharge, i.e., whether alive or dead, were noted. DATA ANALYSIS: All the statistical analyses were performed using Stata (version 14, Stata Corporation, College Station, Texas). Descriptive analysis: The data was initially summarized with the median and mean as measures of central tendency and standard deviations and interquartile ranges (IQR) as measures of spread for continuous variables. Categorical variables were reported as numbers and percentages and they were compared using the χ(2) test or Fisher exact test. Continuous variables were reported as the mean (standard deviation) or median (interquartile range), and the variables were compared using the t test or the Mann- Whitney test. All tests were 2-sided, and a P value of less than 0.05 was considered statistically significant. MULTIVARIATE REGRESSION MODELS: For the multivariable analysis, we built the models by including the factors that reflect demographics, APACHE II score, diagnosis, and CPIS. The analysis was performed using a mixture of continuous, categorical and binary candidate variables. Multivariable analysis was used to select the most influential variables in the final model. RECEIVER OPERATING CHARACTERISTIC (ROC) CURVES: To evaluate the performance of the different scales, we calculated the area under the Receiver operating characteristic (ROC) curves (8) by c-statistic and calibration (the p-value of Hosmer-Lemeshow goodness of fit test). An AUC of 0.5 indicates no discrimination, and an AUC of 1.0 indicates perfect discrimination. We used lfit, lstat, lroc and roccomp commands in Stata to test the calibration and discrimination of the models. OBSERVATION AND RESULTS: We conducted this study in a Medical ICU of Kasturba Hospital, Sevagram in 2016. Of the 837 patients who underwent intubation and mechanical ventilation during the study period, 298 patients were ventilated for 48 hours or more. These patients were free of pneumonia at admission to the intensive care unit. Of the 298 patients, 241 (81% [95% CI 76%- 85%]) died in the hospital; 57 (19% [16%-28%]) survived to hospital discharge. The median length of stay was 6(IQR 4–12) days. Compared with survivors (6[3-12] days), non-survivors stayed a day short in the hospital (5[4-12] days; P = 0.001). The incidence of VAP was 37.6% (112 of 298; 95% CI 32.0-43.1%). Of the 112 patients who developed VAP, 38 (33%) patients developed early VAP, while 74 patients (67%) developed late VAP—calculated by using a cut point of > 4 days of mechanical ventilation. Pulmonary disorders (73, 24%), poisoning (46, 15%) and neurological disorders (48, 16%) accounted for 167 (56%) of 298 admissions. The total duration of mechanical ventilation among patients with VAP was 10.83 ± 7.37 days (median, 8.5 days [interquartile range, 6 to 12 days]) compared with 5.03 ± 3.01 days (median, 4 days [interquartile range, 3 to