Validation of different techniques for the diagnosis of ventilator-associated pneumonia. Comparison with immediate postmortem pulmonary biopsy

Biomarkers in lower respiratory tract samples in the diagnosis of ventilator-associated pneumonia: a systematic review

BACKGROUND

Ventilator-associated pneumonia (VAP) is the most common intensive care unit-acquired infection, yet its diagnosis is complicated by the lack of reliable diagnostic criteria and validated biomarkers. Due to the compartmentalisation of the immune response, host proteins in respiratory tract samples are more likely than serum proteins to accurately identify VAP. However, a reliable biomarker is still missing and it is generally agreed that >90% sensitivity and specificity are required for the introduction of a VAP biomarker into clinical routine.

METHODS

A structured database search was performed to identify publications aimed at deriving or verifying human respiratory tract VAP biomarkers. The results were screened by two independent reviewers and summarised using statistical and narrative synthesis.

RESULTS

40 articles were identified, focusing on 29 unique biomarkers with clinical and microbiological diagnoses of VAP as the reference standard. The most frequently studied biomarker was soluble triggering receptor expressed on myeloid cell 1 (sTREM-1) (n=16), followed by various interleukins (n=7), neutrophil-related proteins (n=8) and amylase as a surrogate for microaspiration (n=4). The target accuracy of >90% specificity and sensitivity for VAP was reported in four publications on sTREM-1, one on pentraxin-3 (PTX3) and one on heparin-binding protein (HBP). Meta-analysis of sTREM-1 resulted in a sensitivity of 78% (95% CI 61-89%) and specificity of 76% (95% CI 49-91%).

DISCUSSION

This systematic review found that no biomarker can currently be recommended for clinical use due to performance below 90% specificity or sensitivity, or insufficient data (PTX3 and HBP). Accurate clinical phenotyping into VAP subcategories may enable the discovery of VAP biomarkers with higher accuracy.

A Bibliometric Analysis of the Role and Research Trending of Bronchoalveolar Lavage in the Diagnosis and Treatment of Ventilator-Associated Pneumonia

Ventilator-associated pneumonia (VAP) is one of the most common complications in intensive care units (ICUs) and negatively affects patient outcomes. Despite its widespread use as a diagnostic and therapeutic measure, the application and effectiveness of bronchoalveolar lavage (BAL) in the management of VAP require further exploration. This study aimed to evaluate the research dynamics, major trends, and scientific networks of BAL in the diagnosis and treatment of VAP using bibliometric analysis. Literature from the Web of Science database on BAL for the diagnosis and treatment of VAP from 1990 to 2024 was screened and analyzed. Keyword co-occurrence, trend analysis, and citation burst analyses were conducted using CiteSpace to identify research hotspots, core authors, institutions, and countries, as well as the evolution of research domains. The bibliometric analysis included 968 publications. Trend analysis indicated growing interest in BAL techniques, particularly in the categories of RESPIRATORY SYSTEM (burst score: 27.82) and MEDICINE, RESEARCH, and EXPERIMENTAL (burst score: 7.41). The co-citation analysis highlighted influential authors in the field, such as Torres (burst score: 9.35), Croce (burst score: 5.86), and Meduri (burst score: 5.71). Keyword analysis results revealed core clusters in the treatment of VAP with BAL, including "nonbronchoscopic lavage" (silhouette value: 0.703), "ICU-acquired infection" (silhouette value: 0.7), and "ventilator-associated tracheobronchitis" (silhouette value: 0.637). Additionally, geographic analysis showed that North America and Europe dominated the research in this field. Recently, research trends regarding protected specimen brushes and quantitative culture techniques have emerged. This study found broad applications of BAL in VAP management, especially in improving diagnostic accuracy and treatment outcomes. Optimized strategies such as improvement of lavage techniques and multidisciplinary collaboration may emerge as potential research hotspots in the future.

Lung ultrasound: A potential tool in the diagnosis of ventilator-associated pneumonia in pediatric intensive care units

PURPOSE

Ventilator-associated pneumonia (VAP) is a common healthcare-associated infection in pediatric intensive care unit (PICU), increasing mortality, antibiotics use and duration of ventilation and hospitalization. VAP diagnosis is based on clinical and chest X-ray (CXR) signs defined by the 2018 Center for Disease Control (gold standard). However, CXR induces repetitive patients' irradiation and technical limitations. This study aimed to investigate if lung ultrasound (LUS) can substitute CXR in the VAP diagnosis.

METHODS

A monocentric and prospective study was conducted in a French tertiary care hospital. Patients under 18-year-old admitted to PICU between November 2018 and July 2020 with invasive mechanical ventilation for more than 48 h were included. The studied LUS signs were consolidations, dynamic air bronchogram, subpleural consolidations (SPC), B-lines, and pleural effusion. The diagnostic values of each sign associated with clinical signs (cCDC) were compared to the gold standard approach. LUS, chest X-ray, and clinical score were performed daily.

RESULTS

Fifty-seven patients were included. The median age was 8 [3-34] months. Nineteen (33%) children developed a VAP. In patients with VAP, B-Lines, and consolidations were highly frequent (100 and 68.8%) and, associated with cCDC, were highly sensitive (100 [79-100] % and 88 [62-98] %, respectively) and specific (95.5 [92-98] % and 98 [95-99] %, respectively). Other studied signs, including SPC, showed high specificity (>97%) but low sensibility (<50%).

CONCLUSION

LUS seems to be a powerful tool for VAP diagnosis in children with a clinical suspicion, efficiently substituting CXR, and limiting children's exposure to ionizing radiations.

A novel gelatinized barium sulfate injection method for assessment of bronchoalveolar lavage parameters

INTRODUCTION

Bronchoalveolar lavage (BAL) is frequently used in pulmonary medicine though it requires further optimization. Practical obstacles such as patient safety and procedural limitation have to date precluded large, controlled trials aimed at standardization of BAL procedure. Indeed, BAL guidelines are based on observational data. Innovative research methods are necessary to advance the clinical practice of BAL.

METHODS

In our study, we evaluated the effect of injecting a gelatinized barium solution into different lobes and segments of cadaveric lungs. As the technique requires an irreversible injection into lung airspaces, it is not suitable for in vivo purposes. We measured the volume returned from BAL as well as the distribution of BAL injection via dissection. Segmental anatomic orientation was compared to a radiologist's impression of plain film radiographs taken of injected lungs.

RESULTS

Mean injected volume distributions were greatest in the upper lobes and lowest in the lower lobes; mean ratios of injected volume distribution to lung lobe volume also followed this trend. Cannulated bronchi orders favored lower branches in the upper lobe and higher branches in the lower lobes. Segmental anatomy varied by the lung lobe injected and was most varied in the lower lobes.

CONCLUSION

This novel gelatinized-barium injection technique provides a minimally complex method to yield clinically meaningful feedback on the performance of BAL. The technique is also adaptable to study of procedural parameters in the context of variable lung anatomies and pathologies.

Infections in Critically Ill Children

Health care-associated infections (HAI) directly influence the survival of children in pediatric intensive care units (PICU), the most common being central line-associated bloodstream infection (CLABSI) 25-30%, followed by ventilator-associated pneumonia (VAP) 20-25%, and others such as catheter-associated urinary tract infection (CAUTI) 15%, surgical site infection (SSI) 11%. HAIs complicate the course of the disease, especially the critical one, thereby increasing the mortality, morbidity, length of hospital stay, and cost. The incidence of HAI in Western countries is 6.1-15.1% and in India, it is 10.5 to 19.5%. The advances in healthcare practices have reduced the incidence of HAIs in the recent years which is possible due to strict asepsis, hand hygiene practices, surveillance of infections, antibiotic stewardship, and adherence to bundled care. The burden of drug resistance and emerging infections are increasing with limited antibiotics in hand, is still a dreadful threat. The most common manifestation of HAIs is fever in PICU, hence the appropriate targeted search to identify the cause of fever should be done. Proper isolation practices, judicious handling of devices, regular microbiologic audit, local spectrum of organisms, identification of barriers in compliance of hand hygiene practices, appropriate education and training, all put together in an efficient and sustained system improves patient outcome.

The comparison of curcuminoid formulations or its combination with conventional therapies versus conventional therapies alone for knee osteoarthritis

BACKGROUND

Presently, curcuminoid formulations or its combination with conventional therapies has been used for the treatment of knee osteoarthritis (KOA). Nevertheless, evidence is limited due to small-sized clinical trials. This study aims to evaluate the efficacy of curcuminoid formulations or its combination with conventional therapies for KOA.

METHODS

Randomized controlled trials comparing curcuminoid formulations or its combination with conventional therapies versus conventional therapies, such as non-steroidal antiinflammatory drugs (NSAIDs) and chondroitin sulfate/glucosamine, were searched from databases.

RESULTS

In total, 14 studies involving 1533 patients were included. Curcuminoid formulations were comparative to NSAIDs in reducing Visual Analogue Scale (VAS), total Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and WOMAC score for pain/stiffness/physical function. No significant difference was seen between the two groups in terms of patients' satisfaction index, patients' global assessment, reduction of several inflammatory factor, rate of drug compliance, and rescue medication. Notably, curcuminoid formulations combined with NSAIDs significantly reduced VAS and WOMAC/Knee injury and OA Outcome Score (KOOS) pain score more than NSAIDs did. In addition, the curcuminoid formulations were superior to chondroitin sulfate/glucosamine in reducing VAS, total WOMAC score, and WOMAC score for stiffness/difficulty in physical function, while no significant difference was seen in reducing WOMAC pain score and Karnofsky Performance Scale score.

CONCLUSIONS

Curcuminoid formulations may be considered a promising alternative for treating KOA. Key points • Curcuminoid formulations are comparative to NSAIDs for KOA. • Curcuminoid formulations are superior to chondroitin sulfate/glucosamine for KOA. • Curcuminoid formulations could provide additional benefits in alleviating pain and some adverse events caused by NSAIDs.

Isolated Rib Fractures in Elderly Falls: Not As Deadly As We Think

BACKGROUND

Rib fractures in elderly patients have been associated with high morbidity and mortality; however, many of these patients had substantial mechanisms of injury, which may have contributed to these high rates.

OBJECTIVE

The purpose of this study was to determine the morbidity and mortality of elderly patients with isolated rib fractures who fell from standing.

METHODS

A single-institution retrospective study was conducted in a Level I trauma center using the trauma registry and a separate elderly fall from standing database. Admitted patients 65 years or older who presented with rib fractures after a fall from January 2013 to June 2017 were included. Patients with a nonthoracic Abbreviated Injury Scale score greater than 2 were excluded from the study.

RESULTS

Of 129 patients with isolated rib fracture, 94% (n = 121) had comorbidities and 71% (n = 92) had two or more comorbidities. Almost half (41.9%; n = 54) were taking antiplatelet and anticoagulant medications, 78.3% (n = 101) were caused by a mechanical fall, and 7% (n = 9) were caused by syncope. Data showed 72.9% (n = 94) had three or more rib fractures. The mortality rate of patients was 3.9% (n = 5). Three patients had dementia at death, four had do-not-resuscitate order, and only two deaths were directly related to pulmonary status. Patients who developed pneumonia (14.7%; n = 19) and required mechanical ventilation for a median of 11 days (3.9%; n = 5) were fewer than those in in previous studies.

CONCLUSION

The morbidity and mortality associated with rib fractures are significantly less than reported in the literature when additional injuries are excluded.

Clinical Value of Bronchoscopy in Acute Respiratory Failure

Bronchoscopy may be considered the “added value” in the diagnostic and therapeutic pathway of different clinical scenarios occurring in acute respiratory critically ill patients. Rigid bronchoscopy is mainly employed in emergent clinical situations due to central airways obstruction, haemoptysis, and inhaled foreign body. Flexible bronchoscopy (FBO) has larger fields of acute applications. In intensive care settings, FBO is useful to facilitate intubation in difficult airways, guide percutaneous dilatational tracheostomy, and mucous plugs causing lobar/lung atelectasis. FBO plays a central diagnostic role in acute respiratory failure caused by intra-thoracic tumors, interstitial lung diseases, and suspected severe pneumonia. “Bronchoscopic” sampling has to be considered when “non-invasive” techniques are not diagnostic in suspected ventilator-associated pneumonia and in non-ventilated immunosuppressed patients. The combined use of either noninvasive ventilation (NIV) or High-flow nasal cannula (HFNC) with bronchoscopy is useful in different scenarios; the largest body of proven successful evidence has been found for NIV-supported diagnostic FBO in non-ventilated high risk patients to prevent and avoid intubation. The expected diagnostic/therapeutic goals of acute bronchoscopy should be balanced against the potential severe risks (i.e., cardio-pulmonary complications, bleeding, and pneumothorax). Expertise of the team is fundamental to achieve the best rate of success with the lowest rate of complications of diagnostic and therapeutic bronchoscopic procedures in acute clinical circumstances.

Association between increased mortality and bronchial fibroscopy in intensive care units and intermediate care units during COPD exacerbations: an analysis of the 2014 and 2015 National French Medical-based Information System Databases (PMSI)

Background

The course of chronic obstructive pulmonary disease (COPD) is punctuated by exacerbations, most often of infectious origin, responsible for many intensive care unit (ICU) and intermediate care unit (IMCU) admissions. Our objective was to study in-hospital mortality during severe COPD exacerbations in ICU and IMCU based on the performance of bronchoscopy.

Methods

A retrospective analysis was carried out on stays in ICUs for COPD exacerbation from the French Programme for the Medicalisation of Information Systems databases for the years 2014 and 2015. Propensity score matching of stays made it possible to constitute two comparable groups on the factors of excess mortality described in the literature (age, sex, SAPS 2, type of admission and bronchial tumour).

Results

We identified 14,491 stays for COPD exacerbation in ICUs, 2586 of which received a bronchoscopy. Mortality was significantly higher in the fibroscopy group (31.32% versus 19.8%). After propensity score matching, we found an excess of mortality in the intervention group (OR = 1.749 [1.516–2.017]) associated with a significantly longer length of stay. The main diagnoses associated with an increased risk of death were pulmonary embolism (OR = 3.251 [1.126–9.384]), bacterial pneumonia (OR = 1.906 [1.173–3.098]) and acute respiratory failure (OR = 1.840 [1.486–2.278]).

Conclusions

Performing bronchoscopy during ICU hospitalisations for severe COPD exacerbations was associated with increased mortality. This increased mortality appears to be related to a bias in patient selection with a procedure reserved for patients with the adverse course.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40560-021-00560-w.

A comparison of diagnostic algorithms and clinical parameters to diagnose ventilator-associated pneumonia: a prospective observational study

Background

Suspicion and clinical criteria continue to serve as the foundation for ventilator-associated pneumonia (VAP) diagnosis, however the criteria used to diagnose VAP vary widely. Data from head-to-head comparisons of clinical diagnostic algorithms is lacking, thus a prospective observational study was performed to determine the performance characteristics of the Johanson criteria, Clinical Pulmonary Infection Score (CPIS), and Centers for Disease Control and Prevention’s National Healthcare Safety Network (CDC/NHSN) criteria as compared to Hospital in Europe Link for Infection Control through Surveillance (HELICS) reference standard.

Methods

A prospective observational cohort study was performed in three mixed medical-surgical ICUs from one academic medical center from 1 October 2016 to 30 April 2018. VAP diagnostic criteria were applied to each patient including CDC/NHSN, CPIS, HELICS and Johanson criteria. Tracheal aspirate cultures (TAC) and serum procalcitonin values were obtained for each patient.

Results

Eighty-five patients were enrolled (VAP 45, controls 40). Using HELICS as the reference standard, the sensitivity and specificity for each of the assessed diagnostic algorithms were: CDC/NHSN (Sensitivity 54.2%; Specificity 100%), CPIS (Sensitivity 68.75%; Specificity 95.23%), Johanson (Sensitivity 67.69%; Specificity 95%). The positive TAC rate was 81.2%. The sensitivity for positive TAC with the serum procalcitonin level > 0.5 ng/ml was 51.8%.

Conclusion

VAP remains a considerable source of morbidity and mortality in modern intensive care units. The optimal diagnostic method remains unclear. Using HELICS criteria as the reference standard, CPIS had the greatest comparative diagnostic accuracy, whereas the sensitivity of the CDC/NHSN was only marginally better than a positive TAC plus serum procalcitonin > 0.5 ng/ml. Algorithm accuracy was improved by adding serum procalcitonin > 0.5 ng/ml, but not positive quantitative TAC.

Trial Registration: Not indicated for this study type.

Comparative Evaluation of the Role of Nonbronchoscopic and Bronchoscopic Techniques of Distal Airway Sampling for the Diagnosis of Ventilator-Associated Pneumonia

Background:

The diagnosis of ventilator-associated pneumonia (VAP) remains a challenge, with clinicians mainly relying on clinical, radiological, and bacteriologic strategies to manage patients with VAP.

Aims:

To compare the results of non-bronchoscopic and bronchoscopic techniques of distal airway sampling for the diagnosis of VAP.

Settings and Design:

This was a single-center prospective diagnostic accuracy study done in the 14-bedded intensive care unit of a tertiary care referral hospital.

Materials and Methods:

Patients aged ≥18 years, on mechanical ventilation for ≥48 h, and with clinical suspicion of VAP (fever, leukocytosis, and increased tracheal secretions) either on admission or during their stay were included. Every patient underwent both procedures for sample collection, first non-bronchoscopic protected bronchoalveolar lavage (NP-BAL) and then bronchoscopic BAL (B-BAL). Clinical Pulmonary Infection Score (CPIS) was calculated for each patient and the collected samples were evaluated in laboratory using standard microbiological techniques.

Statistical Analysis Used:

The sensitivity, specificity, positive predictive value, and negative predictive value of NP-BAL and B-BAL for the diagnosis of VAP were calculated taking CPIS score of >6 as index test for the diagnosis of VAP.

Results:

Sixty patients were included in the study. Both NP-BAL and B-BAL had concordance with the CPIS at 69.1%. The concordance between NP-BAL and B-BAL was better at 67.6% with a kappa coefficient of 0.064 (P = −0.593). The yield and sensitivity of NP-BAL were comparable to that of B-BAL.

Conclusions:

The blind NP-BAL is an equally effective method of airway sampling and could be a better alternative to replace more invasive B-BAL for microbiologic diagnosis of VAP.

Microorganisms and clinical outcomes of early- and late-onset ventilator-associated pneumonia at Srinagarind Hospital, a tertiary center in Northeastern Thailand

Background

Ventilator-associated pneumonia (VAP) is a common nocosomial infection in intensive care unit (ICU). Local microbiological surveillance of pathogens and resistance patterns for early-onset VAP (EOVAP) and late-onset VAP (LOVAP) will help to choose appropriate empiric antibiotics.

Objective

To compare the multi-drug resistant (MDR) pathogens, treatment outcomes, and factors associated with hospital mortality of VAP.

Method

A cross-sectional study between 1 January 2015 and 31 December 2017 at Srinagarind hospital, Khon Kaen University was conducted. The demographic data, causative pathogens, hospital length of stay (LOS), ICU LOS, mechanical ventilator (MV) days, and hospital mortality were retrospectively reviewed.

Results

One hundred and ninety patients were enrolled; 42 patients (22%) were EOVAP and 148 patients (78%) were LOVAP. Acinetobacter baumannii was the most common pathogen in both groups (50% EOVAP vs 52.7% LOVAP). MDR pathogens were significant greater in LOVAP (81.8%) than EOVAP (61.9%) (p = 0.007). The EOVAP had a significantly better ICU LOS [median (interquartile range, IQR) 20.0 (11.0, 30.0) vs. 26.5 (17.0, 43.0) days], hospital LOS [median (IQR) 26.5 (15.0, 44.0) vs. 35.5 (24.0, 56.0) days] shorter MV days [median (IQR) 14.0 (10.0, 29.0) vs. 23.0 (14.0, 35.5) days] and lower hospital mortality (16.7% vs 35.1%) than LOVAP (p < 0.05). The factor associated with hospital mortality was having simplified acute physiology (SAP) II score ≥ 40 with an adjusted odds ratio (aOR) of 2.22 [95% confidence interval (CI), 1.08–4.54, p = 0.02].

Conclusion

LOVAP had significantly higher MDR pathogens, MV days, ICU LOS, hospital LOS and hospital mortality than EOVAP. A broad-spectrum antibiotic to cover MDR pathogens should be considered in LOVAP. The factor associated with hospital mortality of VAP was a SAPII score ≥ 40.

Evaluation of semi-quantitative compared to quantitative cultures of tracheal aspirates for the yield of culturable respiratory pathogens - a cross-sectional study

Background

Diagnosis of lower respiratory tract infections (LRTI) depends on the presence of clinical, radiological and microbiological findings. Endotracheal suction aspirate (ETSA) is the commonest respiratory sample sent for culture from intubated patients. Very few studies have compared quantitative and semi-quantitative processing of ETSA cultures for LRTI diagnosis. We determined the diagnostic accuracy of quantitative and semi-quantitative ETSA culture for LRTI diagnosis, agreement between the quantitative and semi quantitative culture techniques and the yield of respiratory pathogens with both methods.

Methods

This was a cross-sectional study conducted at the Aga Khan University clinical laboratory, Karachi, Pakistan. One hundred and seventy-eight ETSA samples sent for routine bacteriological cultures were processed quantitatively as part of regular specimen processing method and semi-quantitatively. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy was calculated for both methods using clinical diagnosis of pneumonia as reference standard. Agreement between the quantitative and semi quantitative methods was assessed via the kappa statistic test. Pathogen yield between the two methods was compared using Pearson’s chi-square test.

Results

The quantitative and semi-quantitative methods yielded pathogens in 81 (45.5%) and 85 (47.8%) cases respectively. There was complete concordance of both techniques in 155 (87.1%) ETSA samples. No growth was observed in 45 (25.3%) ETSA specimens with quantitative culture and 37 (20.8%) cases by semi-quantitative culture. The diagnostic accuracy of both techniques were comparable; 64.6% for quantitative and 64.0% for semi-quantitative culture. The kappa agreement was found to be 0.84 (95% CI, 0.77–0.91) representing almost perfect agreement between the two methods. Although semi-quantitative cultures yielded more pathogens (47.8%) as compared to quantitative ETSA cultures (45.5%), the difference was only 2.3%. However, this difference achieved statistical (chi-square p-value < 0.001) favoring semi-quantitative culture methods over quantitative culture techniques for processing ETSA.

Conclusion

In conclusion, there is a strong agreement between the performances of both methods of processing ETSA cultures in terms of accuracy of LRTI diagnosis. Semi-quantitative cultures of ETSA yielded more pathogens as compared to quantitative cultures. Although both techniques were comparable, we recommend processing of ETSA using semi-quantitative technique due to its ease and reduced processing time.

Effects of Multidrug-resistant Bacteria in Donor Lower Respiratory Tract on Early Posttransplant Pneumonia in Lung Transplant Recipients Without Pretransplant Infection

BACKGROUND

Multidrug-resistant (MDR) bacteria in the lower respiratory tracts of allografts may be risk factors for early posttransplant pneumonia (PTP) that causes detrimental outcomes in lung transplant recipients (LTRs). We evaluated the effects of immediate changes in MDR bacteria in allografts on early PTP and mortality rates in LTRs.

METHODS

We reviewed 90 adult bilateral LTRs without pretransplant infections who underwent lung transplantation between October 2012 and May 2018. Quantitative cultures were performed with the bronchoalveolar lavage fluids of the allografts preanastomosis and within 3 days posttransplant. The International Society for Heart and Lung Transplantation consensus defines early PTP as pneumonia acquired within 30 days posttransplant and not associated with acute rejection.

RESULTS

MDR Acinetobacter baumannii (11/34, 32.4%) and Staphylococcus aureus (9/34, 26.5%) were identified in 24.4% (22/90) of the preanastomosis allografts. Four LTRs had the same MDR bacteria in allografts preanastomosis and posttransplant. Allograft MDR bacteria disappeared in 50% of the LTRs within 3 days posttransplant. Early PTP and all-cause in-hospital mortality rates were not different between LTRs with and without preanastomosis MDR bacteria (P = 0.75 and 0.93, respectively). MDR bacteria ≥10 CFU/mL in the lungs within 3 days posttransplant was associated with early PTP (odds ratio, 5.8; 95% confidence interval, 1.3-27.0; P = 0.03).

CONCLUSIONS

High levels of preexisting MDR bacteria in allografts did not increase early PTP and mortality rates in LTRs. Despite the small and highly selective study population, lung allografts with MDR bacteria may be safely transplanted with appropriate posttransplant antibiotic therapy.

Diagnostic accuracy of portable chest radiograph in mechanically ventilated patients when compared with autopsy findings

PURPOSE

Evaluate diagnostic accuracy of portable chest radiograph in mechanically ventilated patients taking autopsy findings as the gold standard and the interobserver agreement among intensivists and radiologists.

MATERIALS AND METHODS

Retrospective study of 422 patients over 22 years who died in the ICU, underwent an autopsy, and had at least one portable chest radiograph 72 h prior to death. Two intensivists and two radiologists independently read each chest radiograph. Sensitivity, specificity, positive and negative likelihood ratios were evaluated. Overall performance metrics accuracy between intensivists and radiologists were compared using a generalized estimating equation. Cohen's kappa coefficient was used to evaluate the interobserver agreement with the following values: <0.20:poor, 0.21-0.40:fair, 0.41-0.60:moderate, 0.61-0.80:good, 0.81-1.00:excellent.

RESULTS

Overall sensitivity and specificity for pneumonia was 24% and 91% respectively. Overall sensitivity and specificity for ARDS was 68% and 74% respectively. Sensitivity for pneumonia was higher among radiologists (p < 0,05). Specificity for ADRS was higher among radiologists (p < 0,05). Good interobserver agreement among radiologists and poor correlation between intensivists was found.

CONCLUSIONS

Chest radiographs has a moderate specificity for ARDS and a high specificity for pneumonia, with limited sensitivity in both entities. Interobserver agreement of portable chest radiograph in the mechanically ventilated patients is higher between radiologists than intensivists.

Diagnosis of ventilator-associated pneumonia in critically ill adult patients-a systematic review and meta-analysis

The accuracy of the signs and tests that clinicians use to diagnose ventilator-associated pneumonia (VAP) and initiate antibiotic treatment has not been well characterized. We sought to characterize and compare the accuracy of physical examination, chest radiography, endotracheal aspirate (ETA), bronchoscopic sampling cultures (protected specimen brush [PSB] and bronchoalveolar lavage [BAL]), and CPIS > 6 to diagnose VAP. We searched six databases from inception through September 2019 and selected English-language studies investigating accuracy of any of the above tests for VAP diagnosis. Reference standard was histopathological analysis. Two reviewers independently extracted data and assessed study quality. We included 25 studies (1639 patients). The pooled sensitivity and specificity of physical examination findings for VAP were poor: fever (66.4% [95% confidence interval [CI]: 40.7-85.0], 53.9% [95% CI 34.5-72.2]) and purulent secretions (77.0% [95% CI 64.7-85.9], 39.0% [95% CI 25.8-54.0]). Any infiltrate on chest radiography had a sensitivity of 88.9% (95% CI 73.9-95.8) and specificity of 26.1% (95% CI 15.1-41.4). ETA had a sensitivity of 75.7% (95% CI 51.5-90.1) and specificity of 67.9% (95% CI 40.5-86.8). Among bronchoscopic sampling methods, PSB had a sensitivity of 61.4% [95% CI 43.7-76.5] and specificity of 76.5% [95% CI 64.2-85.6]; while BAL had a sensitivity of 71.1% [95% CI 49.9-85.9] and specificity of 79.6% [95% CI 66.2-85.9]. CPIS > 6 had a sensitivity of 73.8% (95% CI 50.6-88.5) and specificity of 66.4% (95% CI 43.9-83.3). Classic clinical indicators had poor accuracy for diagnosis of VAP. Reliance upon these indicators in isolation may result in misdiagnosis and potentially unnecessary antimicrobial use.

In situ identification of Gram-negative bacteria in human lungs using a topical fluorescent peptide targeting lipid A

Respiratory infections in mechanically ventilated patients caused by Gram-negative bacteria are a major cause of morbidity. Rapid and unequivocal determination of the presence, localization, and abundance of bacteria is critical for positive resolution of the infections and could be used for patient stratification and for monitoring treatment efficacy. Here, we developed an in situ approach to visualize Gram-negative bacterial species and cellular infiltrates in distal human lungs in real time. We used optical endomicroscopy to visualize a water-soluble optical imaging probe based on the antimicrobial peptide polymyxin conjugated to an environmentally sensitive fluorophore. The probe was chemically stable and nontoxic and, after in-human intrapulmonary microdosing, enabled the specific detection of Gram-negative bacteria in distal human airways and alveoli within minutes. The results suggest that pulmonary molecular imaging using a topically administered fluorescent probe targeting bacterial lipid A is safe and practical, enabling rapid in situ identification of Gram-negative bacteria in humans.

Ribosomal PCR assay of excised intervertebral discs from patients undergoing single-level primary lumbar microdiscectomy

PURPOSE

To determine the presence of infectious microorganisms in the herniated discs of immunocompetent patients, using methodology that we hoped would be of higher sensitivity and specificity than has been reported in the past. Recent studies have demonstrated a significant rate of positive cultures for low virulent organisms in excised HNP samples (range 19-53%). These studies have served as the theoretical basis for a pilot trial, and then, a well done prospective randomized trial that demonstrated that systemic treatment with antibiotics may yield lasting improvements in a subset of patients with axial back pain. Whether the reported positive cultures in discectomy specimens represent true positives is as yet not proven, and critically important if underlying the basis of therapeutic approaches for chronic low back pain.

METHODS

This consecutive case series from a single academic center included 44 patients with radiculopathy and MRI findings of lumbar HNP. Patients elected for lumbar microdiscectomy after failure of conservative management. All patients received primary surgery at a single spinal level in the absence of immune compromise. Excised disc material was analyzed with a real-time PCR assay targeting the 16S ribosomal RNA gene followed by amplicon sequencing. No concurrent cultures were performed. Inclusion criteria were as follows: sensory or motor symptoms in a single lumbar nerve distribution; positive physical examination findings including positive straight leg raise test, distributional weakness, and/or a diminished deep tendon reflexes; and magnetic resonance imaging of the lumbar spine positive for HNP in a distribution correlating with the radicular complaint.

RESULTS

The PCR assay for the 16S rRNA sequence was negative in all 44 patients (100%). 95% CI 0-8%.

CONCLUSIONS

Based on the data presented here, there does not appear to be a significant underlying rate of bacterial disc infection in immunocompetent patients presenting with radiculopathy from disc herniation.

Impact and feasibility of an emergency department-based ventilator-associated pneumonia bundle for patients intubated in an academic emergency department

BACKGROUND

Ventilator-associated pneumonia (VAP) has been linked to emergency department (ED) intubation and length of stay (LOS). We assessed VAP prevalence in ED intubated patients, feasibility of ED VAP prevention, and effect on VAP rates.

METHODS

This was a quality improvement initiative using a pre/post design. Phase 1 (PRE1) comprised patients before intensive care unit (ICU) bundle deployment. Phase 2 (PRE2) occurred after ICU but before ED deployment. Phase 3 (POST) included patients received VAP prevention starting at ED intubation. Log-rank test for equality and Cox regression using a Breslow method for ties were performed. Bundle compliance was reported as percentages. Number needed to treat (NNT) was calculated by ventilator day.

RESULTS

PRE1, PRE2, and POST groups were composed of 195, 192, and 153 patients, respectively, with VAP rates of 22 (11.3%), 11 (5.7%), and 6 (3.9%). Log-rank test showed significant reduction in VAP (χ² = 9.16, P = .0103). The Cox regression hazard ratio was 1.38 for the Clinical Pulmonary Infection Score (P = .001), and the hazard ratio was 0.26 for the VAP bundle (P = .005). Bundle compliance >50% for head-of-bed elevation, oral care, subglottic suctioning, and titrated sedation improved significantly with introduction of a registered nurse champion. NNT varied from 7 to 11.

CONCLUSIONS

VAP was common for ED intubated patients. ED-based VAP prevention is feasible. We demonstrate significant reduction in VAP rates, which should be replicated in a multicenter study.

Critical Care Medicine: Major Changes in Dogma of the Past Decade

Critical care medicine is a young specialty that has experienced an expansion of research efforts in the last decade. Many physiologic and therapeutic principles or “dogmas” have been challenged, resulting in major “shifts” and minor “drifts” in thinking. This article reviews the available literature about some of these important and sometimes controversial changes, with emphasis on the practical implications of the concepts. Specific areas discussed include supply-dependent oxygen consumption in critical illness, manipulation of the cytokine cascade in sepsis, ventilation in the acute respiratory distress syndrome (ARDS), blood transfusion in the critically ill, the concept of the multiple organ dysfunction syndrome (MODS), the need for nutritional support in the critically ill, and others. Many of the changes discussed involve the recognition that the host response to a severe insult is exceedingly complex, and the understanding of this response and the effects of it at a tissue and cellular level are incomplete. As a result, the ability to impact the outcome of sepsis and MODS has thus far been disappointing, with the possible exception of “lung-protective” ventilation. The final challenge in critical care medicine is to gain information that will allow the practitioner to better understand, prevent, and treat the complex events that result in organ and cellular dysfunction. Future changes in dogma are welcome if they help achieve these goals.

The Effect of Blind-Protected Specimen Brush Sampling on Antibiotic Use in Patients with Suspected Ventilator-Associated Pneumonia

The diagnosis of pneumonia in ventilated patients is exceedingly difficult. Although culture of tracheal aspirates have poor diagnostic value they are frequently used to diagnose ventilator-associated pneumonia (VAP). Recently a number of studies have reported on the diagnostic value of “blind” protected specimen brush (B-PSB) sampling in the diagnosis of VAP. B-PSB sampling can readily and safely be performed by respiratory care practitioners (RCPs). The aim of this study was to determine the cost-effectiveness of B-PSB sampling performed by respiratory therapists in patients with suspected VAP. During a 3-month run-in period, patients in our medical intensive care unit (MICU) with suspected VAP were treated based on clinical criteria and tracheal aspirate culture. Following this run-in period the house staff, nurses, and RCPs were prevented from sending tracheal aspirates for culture. All patients suspected of having VAP underwent B-PSB sampling with quantitative culture. The B-PSB sampling was performed by RCPs who had been trained to perform the technique. A PSB with a potential bacterial pathogen concentration greater than 500 CFU/ml was regarded as positive. During the 3-month run-in period 172 patients received mechanical ventilation with an average of 4.9 ±3.1 ventilator days/patient. During this period 79 patients were treated for VAP. During the 3-month study period 160 patients received mechanical ventilation, with an average of 5.1 ± 2.9 ventilator days/patient (NS). Fifty-eight B-PSB samplings were performed in 50 patients for suspected VAP. No complications related to the procedure were reported. No tracheal aspirates were cultured during this time period. Eight patients had positive PSB cultures. Antibiotics were changed in three of these patients based on the PSB results. Thirty-eight courses of antibiotics (in 36 patients) were stopped based on negative PSB results. Twelve cases of VAP were suspected in six patients receiving antibiotics for other reasons. No change in antibiotics were made in these cases based on the negative PSB results. The length of mechanical ventilation was 5.4 ± 3.2 days in the 38 culture-negative patients in whom antibiotics were stopped compared to 8.2 ± 4.7 days in the 8 patients with PSB-positive VAP (NS; p = 0.14). The direct cost savings as a result of discontinuing antibiotics was $9,500. There were additional cost savings due to the reduced number of culture specimens sent to the laboratory (approximately $3,000; taking the $23 cost of the PSB brush into account), with a projected annual cost savings of $50,000. B-PSB sampling is a simple and cost-efficient diagnostic test that can safely be performed by adequately trained RCPs. Furthermore, this study confirms that antibiotics may be safely discontinued in patients with negative quantitative culture results.

Does ventilator-associated event surveillance detect ventilator-associated pneumonia in intensive care units? A systematic review and meta-analysis

Background

Ventilator-associated event (VAE) is a new surveillance paradigm for monitoring complications in mechanically ventilated patients in intensive care units (ICUs). The National Healthcare Safety Network replaced traditional ventilator-associated pneumonia (VAP) surveillance with VAE surveillance in 2013. The objective of this study was to assess the consistency between VAE surveillance and traditional VAP surveillance.

Methods

We systematically searched electronic reference databases for articles describing VAE and VAP in ICUs. Pooled VAE prevalence, pooled estimates (sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV)) of VAE for the detection of VAP, and pooled estimates (weighted mean difference (WMD) and odds ratio ([OR)) of risk factors for VAE compared to VAP were calculated.

Results

From 2191 screened titles, 18 articles met our inclusion criteria, representing 61,489 patients receiving mechanical ventilation at ICUs in eight countries. The pooled prevalence rates of ventilator-associated conditions (VAC), infection-related VAC (IVAC), possible VAP, probable VAP, and traditional VAP were 13.8 %, 6.4 %, 1.1 %, 0.9 %, and 11.9 %, respectively. Pooled sensitivity and PPV of each VAE type for VAP detection did not exceed 50 %, while pooled specificity and NPV exceeded 80 %. Compared with VAP, pooled ORs of in-hospital death were 1.49 for VAC and 1.76 for IVAC; pooled WMDs of hospital length of stay were −4.27 days for VAC and −5.86 days for IVAC; and pooled WMDs of ventilation duration were −2.79 days for VAC and −2.89 days for IVAC.

Conclusions

VAE surveillance missed many cases of VAP, and the population characteristics identified by the two surveillance paradigms differed. VAE surveillance does not accurately detect cases of traditional VAP in ICUs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1506-z) contains supplementary material, which is available to authorized users.

Impact of bacterial load on pharmacodynamics and susceptibility breakpoints for tigecycline and Klebsiella pneumoniae

OBJECTIVES

In the absence of other therapeutic options, tigecycline is used to treat bloodstream infections and pneumonia caused by carbapenemase-producing Klebsiella pneumoniae (CP-Kp). In this study, the standard and high tigecycline dosing regimens were simulated and tested against different inocula of CP-Kp isolates in an in vitro pharmacokinetic (PK)/pharmacodynamic (PD) model.

METHODS

Four susceptible isolates (EUCAST MICs of 0.125-1 mg/L) and two intermediately susceptible CP-Kp clinical isolates (MICs of 2 mg/L) were tested at three different inocula (10⁷, 10⁵ and 10³ cfu/mL), simulating tigecycline serum and lung fC_max concentrations of 0.15 and 1.5 mg/L, respectively, of 50 mg tigecycline every 12 h for 48 h. The exposure-effect relationships were described and the probability of target attainment was calculated for each inoculum in order to determine PK/PD susceptibility breakpoints.

RESULTS

No cfu reduction was observed at serum concentrations. At lung concentrations and low inocula, a bacteriostatic and killing effect was found for isolates with MICs of 0.25 and 0.125 mg/L, respectively. The fAUC_0-24/MIC (tAUC_0-24/MIC) associated with half-maximal activity was 16 (150) with 10³ cfu/mL, 28 (239) with 10⁵ cfu/mL and 79 (590) with 10⁷ cfu/mL. A PK/PD susceptibility breakpoint of ≤0.06 and ≤0.125 mg/L for bacteraemia with ≤10¹ cfu/mL and ≤0.25 and ≤0.5 mg/L for pneumonia with ≤10³ cfu/g was determined for the standard tigecycline dose of 50 mg and the higher dose of 100 mg, respectively.

CONCLUSIONS

Tigecycline monotherapy with either 50 or 100 mg would not be sufficient for most patients with bacteraemia, though the higher dose of 100 mg could be effective for patients with pneumonia with low bacterial load.

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

Effectiveness of biomarker-based exclusion of ventilator-acquired pneumonia to reduce antibiotic use (VAPrapid-2): study protocol for a randomised controlled trial

Background

Ventilator-acquired pneumonia (VAP) is a common reason for antimicrobial therapy in the intensive care unit (ICU). Biomarker-based diagnostics could improve antimicrobial stewardship through rapid exclusion of VAP. Bronchoalveloar lavage (BAL) fluid biomarkers have previously been shown to allow the exclusion of VAP with high confidence.

Methods/Design

This is a prospective, multi-centre, randomised, controlled trial to determine whether a rapid biomarker-based exclusion of VAP results in fewer antibiotics and improved antimicrobial management. Patients with clinically suspected VAP undergo BAL, and VAP is confirmed by growth of a potential pathogen at > 10⁴ colony-forming units per millilitre (CFU/ml). Patients are randomised 1:1, to either a ‘biomarker-guided recommendation on antibiotics’ in which BAL fluid is tested for IL-1β and IL-8 in addition to routine microbiology testing, or to ‘routine use of antibiotics’ in which BAL undergoes routine microbiology testing only. Clinical teams are blinded to intervention until 6 hours after randomisation, when biomarker results are reported to the clinician. The primary outcome is a change in the frequency distribution of antibiotic-free days (AFD) in the 7 days following BAL. Secondary outcome measures include antibiotic use at 14 and 28 days; ventilator-free days; 28-day mortality and ICU mortality; sequential organ failure assessment (SOFA) at days 3, 7 and 14; duration of stay in critical care and the hospital; antibiotic-associated infections; and antibiotic-resistant pathogen cultures up to hospital discharge, death or 56 days. A healthcare-resource-utilisation analysis will be calculated from the duration of critical care and hospital stay. In addition, safety data will be collected with respect to performing BAL. A sample size of 210 will be required to detect a clinically significant shift in the distribution of AFD towards more patients having fewer antibiotics and therefore more AFD.

Discussion

This trial will test whether a rapid biomarker-based exclusion of VAP results in rapid discontinuation of antibiotics and therefore improves antibiotic management in patients with suspected VAP.

Trial registration

ISRCTN65937227. Registered on 22 August 2013. ClinicalTrials.gov, NCT01972425. Registered on 24 October 2013.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1442-x) contains supplementary material, which is available to authorized users.

Ventilator-associated Pneumonia caused by commensal oropharyngeal Flora; [corrected] a retrospective Analysis of a prospectively collected Database

Background

The significance of commensal oropharyngeal flora (COF) as a potential cause of ventilator-associated pneumonia (VAP) is scarcely investigated and consequently unknown. Therefore, the aim of this study was to explore whether COF may cause VAP.

Methods

Retrospective clinical, microbiological and radiographic analysis of all prospectively collected suspected VAP cases in which bronchoalveolar lavage fluid exclusively yielded ≥ 10⁴ cfu/ml COF during a 9.5-year period. Characteristics of 899 recent intensive care unit (ICU) admissions were used as a reference population.

Results

Out of the prospectively collected database containing 159 VAP cases, 23 patients were included. In these patients, VAP developed after a median of 8 days of mechanical ventilation. The patients faced a prolonged total ICU length of stay (35 days [P < .001]), hospital length of stay (45 days [P = .001]), and a trend to higher mortality (39 % vs. 26 %, [P = .158]; standardized mortality ratio 1.26 vs. 0.77, [P = .137]) compared to the reference population. After clinical, microbiological and radiographic analysis, COF was the most likely cause of respiratory deterioration in 15 patients (9.4 % of all VAP cases) and a possible cause in 2 patients.

Conclusion

Commensal oropharyngeal flora appears to be a potential cause of VAP in limited numbers of ICU patients as is probably associated with an increased length of stay in both ICU and hospital. As COF-VAP develops late in the course of ICU admission, it is possibly associated with the immunocompromised status of ICU patients.

Quantitative culture of endotracheal aspirate and BAL fluid samples in the management of patients with ventilator-associated pneumonia: a randomized clinical trial

OBJECTIVE:

To compare 28-day mortality rates and clinical outcomes in ICU patients with ventilator-associated pneumonia according to the diagnostic strategy used.

METHODS:

This was a prospective randomized clinical trial. Of the 73 patients included in the study, 36 and 37 were randomized to undergo BAL or endotracheal aspiration (EA), respectively. Antibiotic therapy was based on guidelines and was adjusted according to the results of quantitative cultures.

RESULTS:

The 28-day mortality rate was similar in the BAL and EA groups (25.0% and 37.8%, respectively; p = 0.353). There were no differences between the groups regarding the duration of mechanical ventilation, antibiotic therapy, secondary complications, VAP recurrence, or length of ICU and hospital stay. Initial antibiotic therapy was deemed appropriate in 28 (77.8%) and 30 (83.3%) of the patients in the BAL and EA groups, respectively (p = 0.551). The 28-day mortality rate was not associated with the appropriateness of initial therapy in the BAL and EA groups (appropriate therapy: 35.7% vs. 43.3%; p = 0.553; and inappropriate therapy: 62.5% vs. 50.0%; p = 1.000). Previous use of antibiotics did not affect the culture yield in the EA or BAL group (p = 0.130 and p = 0.484, respectively).

CONCLUSIONS:

In the context of this study, the management of VAP patients, based on the results of quantitative endotracheal aspirate cultures, led to similar clinical outcomes to those obtained with the results of quantitative BAL fluid cultures.

Surveillance versus clinical adjudication: differences persist with new ventilator-associated event definition

BACKGROUND

The National Healthcare Safety Network (NHSN) has recently supported efforts to shift surveillance away from ventilator-associated pneumonia to ventilator-associated events (VAEs) to decrease subjectivity in surveillance and minimize concerns over clinical correlation. The goals of this study were to compare the results of an automated surveillance strategy using the new VAE definition with a prospectively performed clinical application of the definition.

METHODS

All patients ventilated for ≥2 days in a medical and surgical intensive care unit were evaluated by 2 methods: retrospective surveillance using an automated algorithm combined with manual chart review after the NHSN's VAE methodology and prospective surveillance by pulmonary physicians in collaboration with the clinical team administering care to the patient at the bedside.

RESULTS

Overall, a similar number of events were called by each method (69 vs 67). Of the 1,209 patients, 56 were determined to have VAEs by both methods (κ = .81, P = .04). There were 24 patients considered to be a VAE by only 1 of the methods. Most discrepancies were the result of clinical disagreement with the NHSN's VAE methodology.

CONCLUSIONS

There was good agreement between the study teams. Awareness of the limitations of the surveillance definition for VAE can help infection prevention personnel in discussions with critical care partners about optimal use of these data.

A prospective evaluation of ventilator-associated conditions and infection-related ventilator-associated conditions

BACKGROUND

The Centers for Disease Control and Prevention has shifted policy away from using ventilator-associated pneumonia (VAP) and toward using ventilator-associated conditions (VACs) as a marker of ICU quality. To date, limited prospective data regarding the incidence of VAC among medical and surgical ICU patients, the ability of VAC criteria to capture patients with VAP, and the potential clinical preventability of VACs are available.

METHODS

This study was a prospective 12-month cohort study (January 2013 to December 2013).

RESULTS

We prospectively surveyed 1,209 patients ventilated for ≥ 2 calendar days. Sixty-seven VACs were identified (5.5%), of which 34 (50.7%) were classified as an infection-related VAC (IVAC) with corresponding rates of 7.0 and 3.6 per 1,000 ventilator days, respectively. The mortality rate of patients having a VAC was significantly greater than that of patients without a VAC (65.7% vs 14.4%, P < .001). The most common causes of VACs included IVACs (50.7%), ARDS (16.4%), pulmonary edema (14.9%), and atelectasis (9.0%). Among IVACs, 44.1% were probable VAP and 17.6% were possible VAP. Twenty-five VACs (37.3%) were adjudicated to represent potentially preventable events. Eighty-six episodes of VAP occurred in 84 patients (10.0 of 1,000 ventilator days) during the study period. The sensitivity of the VAC criteria for the detection of VAP was 25.9% (95% CI, 16.7%-34.5%).

CONCLUSIONS

Although relatively uncommon, VACs are associated with greater mortality and morbidity when they occur. Most VACs represent nonpreventable events, and the VAC criteria capture a minority of VAP episodes.

Development of an Algorithm for Surveillance of Ventilator-Associated Pneumonia With Electronic Data and Comparison of Algorithm Results With Clinician Diagnoses

Objective.

Surveillance for ventilator-associated pneumonia (VAP) using standard Centers for Disease Control and Prevention (CDC) criteria is labor intensive and involves many subjective assessments. We sought to improve the efficiency and objectivity of VAP surveillance by adapting the CDC criteria to make them amenable to evaluation with electronic data.

Design.

Prospective comparison of the accuracy of VAP surveillance by use of an algorithm with responses to prospective queries made to intensive care physicians. CDC criteria for VAP were used as a reference standard to evaluate the algorithm and clinicians' reports.

Setting.

Three surgical intensive care units and 2 medical intensive care units at an academic hospital.

Methods.

A total of 459 consecutive patients who received mechanical ventilation for a total of 2,540 days underwent surveillance by both methods during consecutive 3-month periods. Electronic surveillance criteria were chosen to mirror the CDC definition. Quantitative thresholds were substituted for qualitative criteria. Purely subjective criteria were eliminated. Increases in ventilator-control settings were taken to indicate worsening oxygenation. Semiquantitative Gram stain of pulmonary secretion samples was used to assess whether there was sputum purulence.

Results.

The algorithm applied to electronic data detected 20 patients with possible VAP. All cases of VAP were confirmed in accordance with standard CDC criteria (100% positive predictive value). Prospective survey of clinicians detected 33 patients with possible VAP. Seventeen of the 33 possible cases were confirmed (52% positive predictive value). Overall, 21 cases of confirmed VAP were identified by either method. The algorithm identified 20 (95%) of 21 known cases, whereas the survey of clinicians identified 17 (81%) of 21 cases.

Conclusions.

Surveillance for VAP using electronic data is feasible and has high positive predictive value for cases that meet CDC criteria. Further validation of this method is warranted.

Application of fiberoptic bronchscopy in patients with acute exacerbations of chronic obstructive pulmonary disease during sequential weaning of invasive-noninvasive mechanical ventilation

BACKGROUND

Early withdrawal of invasive mechanical ventilation (IMV) followed by noninvasive MV (NIMV) is a new strategy for changing modes of treatment in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) with acute respiratory failure (ARF). Using pulmonary infection control window (PIC window) as the switch point for transferring from invasive to noninvasive MV, the time for early extubation can be more accurately judged, and therapy efficacy can be improved. This study aimed to prospectively investigate the clinical effectiveness of fiberoptic bronchscopy (FOB) in patients with AECOPD during sequential weaning of invasive-noninvasive MV.

METHODS

Since July 2006 to January 2011, 106 AECOPD patients with ARF were treated with comprehensive medication and IMV after hospitalization. Patients were randomly divided into two groups according to whether fiberoptic bronchoscope is used (group A, n=54) or not (group B, n=52) during sequential weaning from invasive to noninvasive MV. In group A, for sputum suction and bronchoalveolar lavage (BAL), a fiberoptic bronchoscope was put into the airway from the outside of an endotracheal tube, which was accompanied with uninterrupted use of a ventilator. After achieving PIC window, patients of both groups changed to NIMV mode, and weaned from ventilation. The following listed indices were used to compare between the groups after treatment: 1) the occurrence time of PIC, the duration of MV, the length of ICU stay, the success rate of weaning from MV for the first time, the rate of reventilation and the occurrence rate of ventilator-associated pneumonia (VAP); 2) the convenience and safety of FOB manipulation. The results were compared using Student's t test and the Chi-square test.

RESULTS

The occurrence time of PIC was (5.01±1.49) d, (5.87±1.87) d in groups A and B, respectively (P<0.05); the duration of MV was (6.98±1.84) d, (8.69±2.41) d in groups A and B, respectively (P<0.01); the length of ICU stay was (9.25±1.84) d, (11.10±2.63) d in groups A and B, respectively (P<0.01); the success rate of weaning for the first time was 96.30%, 76.92% in groups A and B, respectively (P<0.01); the rate of reventilation was 5.56%, 19.23% in groups A and B, respectively (P<0.05); and the occurrence rate of VAP was 3.70%, 23.07% in groups A and B, respectively (P<0.01). Moreover, it was easy and safe to manipulate FOB, and no side effect was observed.

CONCLUSIONS

The application of FOB in patients with AECOPD during sequential weaning of invasive-noninvasive MV is effective in ICU. It can decrease the duration of MV and the length of ICU stay, increase the success rate from weaning MV for the first time, reduce the rate of reventilation and the occurrence rate of VAP. In addition, such a method is convenient and safe in patients of this kind.

Ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is a type of nosocomial pneumonia that occurs in patients who receive mechanical ventilation (MV). According to the International Nosocomial Infection Control Consortium (INICC), the overall rate of VAP is 13.6 per 1,000 ventilator days. The incidence varies according to the patient group and hospital setting. The incidence of VAP ranges from 13-51 per 1,000 ventilation days. Early diagnosis of VAP with appropriate antibiotic therapy can reduce the emergence of resistant organisms.

METHOD

The aim of this review was to provide an overview of the incidence, risk factors, aetiology, pathogenesis, treatment, and prevention of VAP. A literature search for VAP was done through the PUBMED/MEDLINE database. This review outlines VAP's risk factors, diagnostic methods, associated organisms, and treatment modalities.

CONCLUSION

VAP is a common nosocomial infection associated with ventilated patients. The mortality associated with VAP is high. The organisms associated with VAP and their resistance pattern varies depending on the patient group and hospital setting. The diagnostic methods available for VAP are not universal; however, a proper infection control policy with appropriate antibiotic usage can reduce the mortality rate among ventilated patients.

Weighted-incidence syndromic combination antibiograms to guide empiric treatment of critical care infections: a retrospective cohort study

Introduction

Empiric antimicrobial selection for critical care infections must balance the need for timely adequate coverage with the resistance pressure exerted by broadspectrum agents. We estimated the potential of weighted incidence syndromic combination antibiograms (WISCAs) to improve time to adequate coverage for critical care infections. In contrast to traditional antibiograms, WISCAs display the likelihood of coverage for a specific infectious syndrome (rather than individual pathogens), and also take into account the potential for poly-microbial infections and the use of multi-drug regimens.

Methods

Cases of ventilator-associated pneumonia (VAP) and catheter-related bloodstream infection (CRBSI) were identified over three years using stringent surveillance criteria. Based on the susceptibility profile of the culprit pathogens, we calculated the WISCA percentages of infections that would have been adequately covered by common antimicrobial(s). We then computed the excess percentage coverage offered by WISCA regimens compared to the actual antimicrobials administered to patients by 12 h, 24 h, and 48 h from culture collection.

Results

Among 163 patients with critical care infection, standard practice only resulted in adequate coverage of 35% of patients by 12 h, 52% by 24 h, and 75% by 48 h. No WISCA mono-therapy regimen offered greater than 85% adequate overall coverage for VAP and CRBSI. A wide range of dual therapy regimens would have conferred greater than 90% adequate coverage, with excess coverage estimated to be as high as +56%, +42% and +18% at 12 h, 24 h and 48 h, respectively. We did not detect a decrease in mortality associated with early adequate treatment, and so could not estimate potential downstream benefits.

Conclusions

WISCA-derived empiric antimicrobial regimens can be calculated for patients with intensive care unit (ICU)-acquired infections, and have the potential to reduce time to adequate treatment. Prospective research must confirm whether implementation of WISCA prescribing aids facilitate timely adequate treatment and improved ICU outcomes.

Descriptive epidemiology and attributable morbidity of ventilator-associated events

OBJECTIVE

The Centers for Disease Control and Prevention implemented new surveillance definitions for ventilator-associated events (VAEs) in January 2013. We describe the epidemiology, attributable morbidity, and attributable mortality of VAEs.

DESIGN

Retrospective cohort study.

SETTING

Academic tertiary care center.

PATIENTS

All patients initiated on mechanical ventilation between January 1, 2006, and December 31, 2011.

METHODS

We calculated and compared VAE hazard ratios, antibiotic exposures, microbiology, attributable morbidity, and attributable mortality for all VAE tiers.

RESULTS

Among 20,356 episodes of mechanical ventilation, there were 1,141 (5.6%) ventilator-associated condition (VAC) events, 431 (2.1%) infection-related ventilator-associated complications (IVACs), 139 (0.7%) possible pneumonias, and 127 (0.6%) probable pneumonias. VAC hazard rates were highest in medical, surgical, and thoracic units and lowest in cardiac and neuroscience units. The median number of days to VAC onset was 6 (interquartile range, 4-11). The proportion of IVACs to VACs ranged from 29% in medical units to 42% in surgical units. Patients with probable pneumonia were more likely to be prescribed nafcillin, ceftazidime, and fluroquinolones compared with patients with possible pneumonia or IVAC-alone. The most frequently isolated organisms were Staphylococcus aureus (29%), Pseudomonas aeruginosa (14%), and Enterobacter species (7.9%). Compared with matched controls, VAEs were associated with more days to extubation (relative rate, 3.12 [95% confidence interval (CI), 2.96-3.29]), more days to hospital discharge (relative rate, 1.46 [95% CI, 1.37-1.55]), and higher hospital mortality risk (odds ratio, 1.98 [95% CI, 1.60-2.44]).

CONCLUSIONS

VAEs are common and morbid. Prevention strategies targeting VAEs are needed.

Developing a new, national approach to surveillance for ventilator-associated events*

OBJECTIVE

To develop and implement an objective, reliable approach to surveillance for ventilator-associated events in adult patients.

DESIGN

The Centers for Disease Control and Prevention (CDC) convened a Ventilator-Associated Pneumonia (VAP) Surveillance Definition Working Group in September 2011. Working Group members included representatives of stakeholder societies and organizations and federal partners.

MAIN RESULTS

The Working Group finalized a three-tier, adult surveillance definition algorithm for ventilator-associated events. The algorithm uses objective, readily available data elements and can identify a broad range of conditions and complications occurring in mechanically ventilated adult patients, including but not limited to VAP. The first tier definition, ventilator-associated condition (VAC), identifies patients with a period of sustained respiratory deterioration following a sustained period of stability or improvement on the ventilator, defined by changes in the daily minimum fraction of inspired oxygen or positive end-expiratory pressure. The second tier definition, infection-related ventilator-associated complication (IVAC), requires that patients with VAC also have an abnormal temperature or white blood cell count, and be started on a new antimicrobial agent. The third tier definitions, possible and probable VAP, require that patients with IVAC also have laboratory and/or microbiological evidence of respiratory infection.

CONCLUSIONS

Ventilator-associated events surveillance was implemented in January 2013 in the CDC's National Healthcare Safety Network. Modifications to improve surveillance may be made as additional data become available and users gain experience with the new definitions.

Abundant DNase I-sensitive bacterial DNA in healthy porcine lungs and its implications for the lung microbiome

Human lungs are constantly exposed to bacteria in the environment, yet the prevailing dogma is that healthy lungs are sterile. DNA sequencing-based studies of pulmonary bacterial diversity challenge this notion. However, DNA-based microbial analysis currently fails to distinguish between DNA from live bacteria and that from bacteria that have been killed by lung immune mechanisms, potentially causing overestimation of bacterial abundance and diversity. We investigated whether bacterial DNA recovered from lungs represents live or dead bacteria in bronchoalveolar lavage (BAL) fluid and lung samples in young healthy pigs. Live bacterial DNA was DNase I resistant and became DNase I sensitive upon human antimicrobial-mediated killing in vitro. We determined live and total bacterial DNA loads in porcine BAL fluid and lung tissue by comparing DNase I-treated versus untreated samples. In contrast to the case for BAL fluid, we were unable to culture bacteria from most lung homogenates. Surprisingly, total bacterial DNA was abundant in both BAL fluid and lung homogenates. In BAL fluid, 63% was DNase I sensitive. In 6 out of 11 lung homogenates, all bacterial DNA was DNase I sensitive, suggesting a predominance of dead bacteria; in the remaining homogenates, 94% was DNase I sensitive, and bacterial diversity determined by 16S rRNA gene sequencing was similar in DNase I-treated and untreated samples. Healthy pig lungs are mostly sterile yet contain abundant DNase I-sensitive DNA from inhaled and aspirated bacteria killed by pulmonary host defense mechanisms. This approach and conceptual framework will improve analysis of the lung microbiome in disease.

Diagnosis of ventilator-associated pneumonia: controversies and working toward a gold standard

PURPOSE OF REVIEW

The aim is to discuss the clinical, microbiologic, and radiological criteria used in the diagnosis of ventilator-associated pneumonia (VAP), distinguish between ventilator-associated tracheobronchitis (VAT) and VAP, and reconcile the proposed Centers for Disease Control surveillance criteria with clinical practice.

RECENT FINDINGS

Numerous ventilator-associated complications (VACs), including VAP and VAT, may occur in critically ill, intubated patients. A variety of definitions for identifying VAP have been proposed, but there is no diagnostic gold standard. The proposed surveillance definition will identify infectious and noninfectious VAC, including VAP and VAT, but this definition may be inadequate for clinical practice.

SUMMARY

The clinical characteristics of VAP and VAT are similar and include fever, leukocytosis, and purulent sputum. An infiltrate on chest radiograph is consistent with VAP but lacks diagnostic precision, so it is not a criterion in the proposed surveillance definition and should be interpreted cautiously by clinicians. Microbiologically, quantitative and semiquantitative endotracheal aspirate cultures may be employed to diagnose VAP and VAT. Positive bronchoalveolar lavage and protected specimen brush cultures are useful only for the diagnosis of VAP. Experts should collaborate to develop consensus definitions for VAP and VAT that can be applied in practice.

Evaluation of the diagnostic value of fluorescent in situ hybridization in a rat model of bacterial pneumonia

In severe nosocomial pneumonia, the pathogenic responsibility of bacteria isolated from airways is far from certain, and a lung biopsy is sometimes performed. However, detection and identification of pathogens are frequently unachieved. Here, we developed a protocol for direct visualization of bacteria within the lung tissue using fluorescent in situ hybridization (FISH) in a rat model of Acinetobacter baumannii pneumonia. The reference positive diagnosis of bacterial pneumonia was the presence of pathological signs of pneumonia associated with the proof of bacteria or bacterial PCR products into the parenchyma. By analysis of 122 sets of slices from 26 rats and using the eubacterial probe EUB-338, our results show that FISH reached a sensitivity and a diagnostic accuracy higher than that of optic microscopy (sensitivity: 96% versus 55.4% and diagnostic accuracy: 96.7% versus 66.4%), whereas both approaches had 100% specificity. FISH could be useful especially on negative biopsies from patients with suspected infectious pneumonia.

Prospective, protocolized study evaluating effects of antibiotics on sputum culture results in injured patients

BACKGROUND

Appropriate utilization of antibiotics for critically ill patients involves tailoring the drug to culture results; however, the culture results must be reliable. We hypothesized that antimicrobial agents reduce significantly the reliability of cultures obtained between 1 and 24 h after antibiotic administration.

METHODS

Patients were eligible for the study if they were ventilated mechanically and were suspected to have pneumonia. After enrollment, sputum cultures were obtained, and broad-spectrum antibiotics were started. Sputum cultures were repeated at 1, 6, 12, and 24 h after delivery of the first dose of antibiotic. Twenty-one patients whose initial culture was positive were included in the analysis. Their average age was 49.4 years, and the average Injury Severity Score was 27.7 points.

RESULTS

The average intensive care unit and hospital lengths of stay were 20.2 days and 24.7 days, respectively. All of the organisms grown from the pre-antibiotic cultures also grew in the cultures obtained 1 h after antibiotics were given. However, a significant number of these organisms were unable to be grown in subsequent cultures. The rate of negative cultures increased to 21%, 32%, and 42% in the 6-, 12-, and 24-h groups (p<0.01), respectively. Gram-positive organisms accounted for 42.9% of infections, with Staphylococcus aureus being the most common. All patients positive for S. aureus prior to antibiotic administration remained positive at each subsequent time. By 6 h, 21.5% of the gram-negative organisms could no longer be cultured. At 12 h, among the gram-positive organisms, 11 of 12 cultures were still positive, whereas only 50% of gram-negative organisms were still recoverable.

CONCLUSION

Antibiotics have a substantial effect on culture results that is most pronounced in gram-negative organisms and is observed in cultures obtained beginning 1 h after antibiotics are given. As a result, cultures obtained more than 1 h after antibiotics are started cannot be used to tailor antibiotic choice in injured patients with suspected infections.

Bilateral versus unilateral bronchoalveolar lavage for the diagnosis of ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) complicates the clinical course of critically injured intubated patients. Bronchoscopic bronchoalveolar lavage (BAL) represents an invasive and accurate means of VAP diagnosis. Unilateral and blinded techniques offer less invasive alternatives to bronchoscopic BAL. This study evaluated clinical criteria as well as unilateral directed versus bilateral BAL for VAP diagnosis.

METHODS

A retrospective chart review of 113 consecutive intubated trauma patients with clinically suspected VAP undergoing unilateral versus bilateral BAL was performed with comparison of positive culture results (>10(4) colony-forming units [CFU]/mL). Culture results were compared with chest radiograph (CXR) infiltrates and white blood cell (WBC) count elevation.

RESULTS

Bilateral BAL was more likely to be positive than unilateral BAL (50.4% vs. 25.5%). In 37.1% of bilateral BALs, there was discordance between the sides of positivity or the bacteria isolated. A CXR infiltrate and WBC count elevation did not predict positive BAL.

CONCLUSIONS

Clinical indicators of VAP are inaccurate, and bilateral bronchoscopic BAL is more likely than unilateral BAL to provide a positive sample in intubated trauma patients. Techniques that do not sample both lungs reliably should be avoided for diagnosis in this patient population.

Ventilator-associated complications, including infection-related complications: the way forward

Acute respiratory failure represents the most common condition requiring admission to an adult intensive care unit. Ventilator-associated pneumonia (VAP) has been used as a marker of quality for patients with respiratory failure. Hospital-based process-improvement initiatives to prevent VAP have been successfully used. The use of ventilator-associated complications (VACs) has been proposed as an objective marker to assess the quality of care for this patient population. The use of evidence-based bundles targeting the reduction of VACs, as well as the conduct of prospective studies showing that VACs are preventable complications, are reasonable first-steps in addressing this important clinical problem.

Rapid and reproducible surveillance for ventilator-associated pneumonia

BACKGROUND

The complexity and subjectivity of ventilator-associated pneumonia (VAP) surveillance limit its value in assessing and comparing quality of care for ventilated patients. A simpler, more quantitative VAP definition may increase utility.

METHODS

We streamlined the Centers for Disease Control and Prevention definition of VAP to increase objectivity and efficiency. Qualitative criteria were replaced with quantitative criteria, and changes in ventilator settings were used to screen patients for worsening oxygenation. We retrospectively compared surveillance time, reproducibility, and outcomes for streamlined versus conventional surveillance among medical and surgical patients on mechanical ventilation in 3 university hospitals.

RESULTS

Application of the streamlined definition was faster (mean 3.5 minutes vs 39.0 minutes per patient) and more objective (interrater reliability κ 0.79 vs 0.45) than the conventional definition. On multivariate analysis, the streamlined definition predicted increases in ventilator days (6.5 days [95% CI, 4.1-10.0] vs 6.4 days [95% CI, 4.7-8.6]), intensive care days (5.6 days [95% CI, 3.2-8.9] vs 6.2 days [95% CI, 4.6-8.2]), and hospital mortality (odds ratio [OR] 0.84 [95% CI, 0.31-2.29] vs OR 0.69 [95% CI, 0.30-1.55]) as effectively as conventional surveillance. The conventional definition was a marginally superior predictor of increased hospital days (5.2 days [95% CI, 3.4-7.6] vs 2.1 days [95% CI, -0.5-5.6]).

CONCLUSIONS

A streamlined version of the VAP definition was faster, more objective, and predicted patients' outcomes almost as effectively as the conventional definition. VAP surveillance using the streamlined method may facilitate more objective and efficient quality assessment for ventilated patients.