Impact of pathogen-directed antimicrobial therapy for ventilator-associated pneumonia in trauma patients on charges and recurrence

From bedside to bedside: how iterative clinical research influenced the diagnosis and management of pneumonia at the Elvis Presley Trauma Center

Ventilator-associated pneumonia is a well-acknowledged complication after hospitalization for injury or surgical emergency. The contribution to the literature on this topic by Dr Timothy Fabian and the Memphis group at the Elvis Presley Trauma Center resulted in the contemporary recognition that the diagnosis and management of pneumonia is an essential component of surgical critical care. During three decades, the Memphis group, under Dr Fabian's leadership, performed numerous clinical studies that led to the publication of over 40 articles concerning the epidemiology, diagnosis, and treatment of pneumonia after injury. The purpose of this review is to survey the consecutive studies from Memphis specifically that led to the development of a clinical pathway that has stood the test of time. Examination of the research output during this period provides a case study in how bedside clinical research can inform clinical practice and is a model for applied science in the intensive care unit.

Early pneumonia diagnosis decreases ventilator-associated pneumonia rates in trauma population

BACKGROUND

Ventilator-associated pneumonia (VAP) is a source of morbidity and mortality for trauma patients. Aspiration events are also common because of traumatic brain injury, altered mental status, or facial trauma. In patients requiring mechanical ventilation, early pneumonias (EPs) may be erroneously classified as ventilator associated.

METHODS

A prospective early bronchoscopy protocol was implemented from January 2020 to January 2022. Trauma patients intubated before arrival or within 48 hours of admission underwent bronchoalveolar lavage (BAL) within 24 hours of intubation. Patients with more than 100,000 colony-forming units on BAL were considered to have EP.

RESULTS

A total of 117 patients underwent early BAL. Ninety-three (79.5%) had some growth on BAL with 36 (30.8%) meeting criteria for EP. For the total study population, 29 patients (24.8%) were diagnosed with VAP later in their hospital course, 12 of which had previously been diagnosed with EP. Of EP patients (n = 36), 21 (58.3%) were treated with antibiotics based on clinical signs of infection. Of EP patients who had a later pneumonia diagnosed by BAL (n = 12), seven (58.3%) grew the same organism from their initial BAL. When these patients were excluded from VAP calculation, the rate was reduced by 27.6%. Patients with EP had a higher rate of smoking history (41.7% vs. 19.8%, p < 0.001) compared with patients without EP. There was no difference in median hospital length of stay, intensive care unit length of stay, ventilator days, or mortality between the two cohorts.

CONCLUSION

Early pneumonia is common in trauma patients intubated within the first 48 hours of admission and screening with early BAL identifies patients with aspiration or pretraumatic indicators of pneumonia. Accounting for these patients with early BAL significantly reduces reported VAP rates.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level IV.

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.

The Effect of Lung Lavage Volume Return on the Diagnosis of Ventilator-Associated Pneumonia

BACKGROUND

Bronchoalveolar lavage (BAL) is a commonly used tool in the diagnosis of ventilator-associated pneumonia (VAP). Previous protocols recommend 30% lavage return, though no studies have investigated this relationship. This study aims to assess the influence of BAL volume return on VAP diagnosis.

MATERIALS AND METHODS

A retrospective review was performed of a prospectively maintained database for BAL performed from January 2015 to January 2016 in the trauma and surgical ICU at a level 1 trauma center. In total, 147 ventilated patients with clinical suspicion for pneumonia underwent 264 BALs. A protocol was used with five aliquots of 20 cc of saline instilled. Quantitative cultures were performed with 10ˆ5 colony-forming organisms as the threshold for VAP diagnosis. BAL was repeated at 6-8 d on 50 patients. Univariate and multivariate regression analyses were performed to investigate the predictors of VAP diagnosis.

RESULTS

Patients with >40% lavage return had increased rates of VAP diagnosis (odds ratio [OR] 2.86, P = 0.002). Increasing volume return also trended toward a lower false-negative rate. Temperature, leukocytosis, and X-ray infiltrate were not associated with increased VAP diagnosis. Concurrent antibiotic therapy at the time of BAL predicted decreased VAP diagnosis (OR 0.58, P = 0.04). On multivariable analysis, only >40% return remained associated with increased rate of VAP diagnosis (OR 4.00, P = 0.004).

CONCLUSIONS

This study found that >40% lavage volume return was associated with increased VAP diagnosis. Clinicians should consider the reliability of a negative BAL if clinical suspicion of VAP is high and lavage return is <40%. Additional investigation is needed to further elucidate this association.

Does lack of thoracic trauma attenuate the severity of pulmonary failure? An 8-year analysis of critically injured patients

PURPOSE

Patients with thoracic trauma are presumed to be at higher risk for pulmonary dysfunction, but adult respiratory distress syndrome (ARDS) may develop in any patient, regardless of associated chest injury. This study evaluated the impact of thoracic trauma and pulmonary failure on outcomes in trauma patients admitted to the intensive-care unit (ICU).

METHODS

All trauma patients admitted to the ICU over an 8-year period were identified. Patients that died within 48 h of arrival were excluded. Patients were stratified by baseline characteristics, injury severity, development of ARDS, and infectious complications. Multiple logistic regression was used to determine variables significantly associated with the development of ARDS.

RESULTS

10,362 patients were identified. After exclusions, 4898 (50%) patients had chest injury and 4975 (50%) did not. 200 (2%) patients developed ARDS (3.6% of patients with chest injury and 0.5% of patients without chest injury). Patients with ARDS were more likely to have chest injury than those without ARDS (87% vs 49%, p < 0.001). However, of the patients without chest injury, the development of ARDS still led to a significant increase in mortality compared to those patients without ARDS (58% vs 5%, p < 0.001). Multiple logistic regression found ventilator-associated pneumonia (VAP) to be the only independent predictor for the development of ARDS in ICU patients without chest injury.

CONCLUSIONS

ARDS development was more common in patients with thoracic trauma. Nevertheless, the development of ARDS in patients without chest injury was associated with a tenfold higher risk of death. The presence of VAP was found to be the only potentially preventable and treatable risk factor for the development of ARDS in ICU patients without chest injury.

Treatment of Achromobacter Ventilator-Associated Pneumonia in Critically Ill Trauma Patients

BACKGROUND

Achromobacter sp are nonfermenting Gram-negative bacilli (NFGNB) that rarely cause severe infections, including ventilator-associated pneumonia (VAP). Data on the treatment of Achromobacter pneumonia are very limited, and the organism has been associated with a high mortality rate. Thus, more data are needed on treating this organism.

OBJECTIVE

To evaluate the treatment of Achromobacter VAP in critically ill trauma patients.

METHODS

This retrospective, observational study evaluated critically ill trauma patients who developed Achromobacter VAP. A previously published pathway for the diagnosis and management of VAP was used according to routine patient care. This included the use of quantitative bronchoscopic bronchoalveolar lavage cultures to definitively diagnose VAP.

RESULTS

A total of 37 episodes of Achromobacter VAP occurred in 34 trauma intensive care unit patients over a 15-year period. The most commonly used definitive antibiotics were imipenem/cilastatin, cefepime, or trimethoprim/sulfamethoxazole. The primary outcome of clinical success was achieved in 32 of 37 episodes (87%). This is similar to previous studies of other NFGNB VAP (eg, Pseudomonas, Acinetobacter) from the study center. Microbiological success was seen in 21 of 28 episodes (75%), and VAP-related mortality was 9% (3 of 34 patients).

CONCLUSIONS

Achromobacter is a rare but potentially serious cause of VAP in critically ill patients. In this study, there was an acceptable success rate compared with other causes of NFGNB VAP in this patient population.

Evaluation of the Xpert Carba-R (Cepheid) Assay Using Contrived Bronchial Specimens from Patients with Suspicion of Ventilator-Associated Pneumonia for the Detection of Prevalent Carbapenemases

There is a critical need for rapid diagnostic methods for multidrug-resistant (MDR) pathogens in patients with a suspicion of ventilator-associated pneumonia (VAP). The Xpert Carba-R detects 5 targets for carbapenemase-producing organisms (bla_KPC, bla_NDM, bla_VIM, bla_OXA-48, and bla_IMP-1). Our objective was to evaluate the performance of this assay directly on bronchial aspirates and to correlate the cycle number for a positive result (Ct) with the bacterial count. Bronchial aspirates from patients with a suspicion of VAP were spiked with a dilution of 1 of 4 MDR organisms carrying the resistance genes detected by the test prepared to a final concentration of 10²−10⁵ cfu/mL. We used a ROC curve and provided areas under the curve (AUC) with their 95% confidence intervals (CI). A point of maximum sensitivity (Se) and specificity (Sp) was derived and validity indices were calculated. One hundred contrived tests were performed. Se and Sp were 100% for all bacterial counts. A positive sample with a Ct ≤24.7 corresponded to a count ≥10⁵ cfu/mL; if the Ct was within the range >24.7-≤26.9, this corresponded to a count ≥10⁴ cfu/mL. When the Ct was >26.9, this corresponded to a count <10⁴ cfu/mL. The Xpert Carba-R detects carbapenemase-producing organisms directly in contrived bronchial aspirates. Still, an important issue to consider is that the number of gene copies may vary according to many factors in vivo. If confirmed in further studies, the strong correlation observed between Ct values and the results of semiquantitative cultures suggests this test could serve to differentiate between infection and colonization in routine clinical practice.