Clinical Diagnosis of Infection in Surgical Intensive Care Unit: You're Not as Good as You Think!

Background: Because of the everincreasing costs and the complexity of institutional medical reimbursement policies, the necessity for extensive laboratory work-up of potentially infected patients has come into question. We hypothesized that intensivists are able to differentiate between infected and non-infected patients clinically, without the need to pan-culture, and are able to identify the location of the infection clinically in order to administer timely and appropriate treatment. Methods: Data collected prospectively on critically ill patients suspected of having an infection in the surgical intensive care unit (SICU) was obtained over a six-month period in a single tertiary academic medical center. Objective evidence of infection derived from laboratory or imaging data was compared with the subjective answers of the three most senior physicians' clinical diagnoses. Results: Thirty-nine critically ill surgical patients received 52 work-ups for suspected infections on the basis of signs and symptoms (e.g., fever, altered mental status). Thirty patients were found to be infected. Clinical diagnosis differentiated infected and non-infected patients with only 61.5% accuracy (sensitivity 60.3%; specificity 64.4%; p = 0.0049). Concordance between physicians was poor (κ = 0.33). Providers were able to predict the infectious source correctly only 60% of the time. Utilization of culture/objective data and SICU antibiotic protocols led to overall 78% appropriate initiation of antibiotics compared with 48% when treatment was based on clinical evaluation alone. Conclusion: Clinical diagnosis of infection is difficult, inaccurate, and unreliable in the absence of culture and sensitivity data. Infection suspected on the basis of signs and symptoms should be confirmed via objective and thorough work-up.

Variations of the lung microbiome and immune response in mechanically ventilated surgical patients

Mechanically ventilated surgical patients have a variety of bacterial flora that are often undetectable by traditional culture methods. The source of infection in many of these patients remains unclear. To address this clinical problem, the microbiome profile and host inflammatory response in bronchoalveolar lavage samples from the surgical intensive care unit were examined relative to clinical pathology diagnoses. The hypothesis was tested that clinical diagnosis of respiratory tract flora were similar to culture positive lavage samples in both microbiome and inflammatory profile. Bronchoalveolar lavage samples were collected in the surgical intensive care unit as standard of care for intubated individuals with a clinical pulmonary infection score of >6 or who were expected to be intubated for >48 hours. Cytokine analysis was conducted with the Bioplex Pro Human Th17 cytokine panel. The microbiome of the samples was sequenced for the 16S rRNA region using the Ion Torrent. Microbiome diversity analysis showed the culture-positive samples had the lowest levels of diversity and culture negative with the highest based upon the Shannon-Wiener index (culture positive: 0.77 ± 0.36, respiratory tract flora: 2.06 ± 0.73, culture negative: 3.97 ± 0.65). Culture-negative samples were not dominated by a single bacterial genera. Lavages classified as respiratory tract flora were more similar to the culture-positive in the microbiome profile. A comparison of cytokine expression between groups showed increased levels of cytokines (IFN-g, IL-17F, IL-1B, IL-31, TNF-a) in culture-positive and respiratory tract flora groups. Culture-positive samples exhibited a more robust immune response and reduced diversity of bacterial genera. Lower cytokine levels in culture-negative samples, despite a greater number of bacterial species, suggest a resident nonpathogenic bacterial community may be indicative of a normal pulmonary environment. Respiratory tract flora samples were most similar to the culture-positive samples and may warrant classification as culture-positive when considering clinical treatment.

Predictors of a histopathologic diagnosis of complicated appendicitis

BACKGROUND

Despite its utilization, the intraoperative (IO) assessment of complicated appendicitis (CA) is subjective. The histopathologic (HP) diagnosis should be the gold standard in identifying patients with CA; however, it is not immediately available to guide postoperative management. The objective of this study was to identify predictors of an HP diagnosis of CA.

MATERIALS AND METHODS

A retrospective review of all patients who underwent appendectomy at our institution from 2011-2013 was conducted. CA was defined by perforation or abscess on pathology report. Predictors of an HP diagnosis of CA were evaluated using a multivariable regression model.

RESULTS

A total of 239 of 1066 patients had CA based on IO assessment, whereas 143 of 239 patients (60%) had CA on HP and IO assessment. On multivariable analysis, an IO diagnosis of CA was associated with an HP diagnosis of CA (odds ratio [OR]: 10.92; 95% confidence interval [CI]: 7.19-16.58). Other risk factors were age (OR: 1.28; 95% CI: 1.09-1.49), number of days of pain (OR: 1.20; 95% CI: 1.07-1.37), increased heart rate (OR: 1.14; 95% CI: 1.02-1.26), appendix size (OR: 1.09; 95% CI: 1.03-1.16), and an appendicolith (OR: 1.74; 95% CI: 1.12-2.71) on preoperative CT imaging.

CONCLUSIONS

In addition to age, increased heart rate, pain duration, appendix size and appendicolith, the IO assessment is also associated with an HP diagnosis of CA; however, 40% of patients were incorrectly classified. Using these predictors with improved IO grading may achieve more accurate diagnosis of CA.

Ventilator-Associated Pneumonia: New Definitions

The National Healthcare Safety Network's new classification characterizes all adverse ventilator-associated events (VAE) into a tiered system designed to shift the focus away from ventilator-associated pneumonia as the only important cause or morbidity in ventilated patients. This new surveillance definition of VAE eliminates subjectivity by using clearly defined criteria and facilitates the automated collection of data. This allows for easier comparison and analysis of factors affecting rates of VAE. Numerous studies have been published that demonstrate its clinical application. This article presents the VAE criteria, contrasts the difference from the previous ventilator-associated pneumonia definition, and discusses its implementation over the past 5 years.

Common Lung Microbiome Identified among Mechanically Ventilated Surgical Patients

The examination of the pulmonary microbiome in patients with non-chronic disease states has not been extensively examined. Traditional culture based screening methods are often unable to identify bacteria from bronchoalveolar lavage samples. The advancement of next-generation sequencing technologies allows for a culture-independent molecular based analysis to determine the microbial composition in the lung of this patient population. For this study, the Ion Torrent PGM system was used to assess the microbial complexity of culture negative bronchoalveolar lavage samples. A group of samples were identified that all displayed high diversity and similar relative abundance of bacteria. This group consisted of Hydrogenophaga, unclassified Bacteroidetes, Pedobacter, Thauera, and Acinetobacter. These bacteria may be representative of a common non-pathogenic pulmonary microbiome associated within this population of patients.

Applicability of the National Healthcare Safety Network's surveillance definition of ventilator-associated events in the surgical intensive care unit: a 1-year review

BACKGROUND

In 2012, the National Healthcare Safety Network presented a new surveillance definition for ventilator-associated events (VAEs) to objectively define worsening pulmonary status in ventilated patients. VAE subcategories, ventilator-associated condition (VAC), infection-related VAC, and probable ventilator-associated pneumonia (PrVAP), were vetted predominantly in medical intensive care units. Our goal was to evaluate how well VAE criteria characterize pulmonary complications in surgical intensive care unit (SICU) patients.

METHODS

Since September 2012, all intubated SICU patients were screened prospectively for VAE and monitored for sustained respiratory dysfunction that did not meet VAE criteria. We diagnosed ventilator-associated pneumonia (VAP) using a clinical definition: Clinical Pulmonary Infection Score (CPIS) greater than 6 and catheter-directed bronchoalveolar lavage cultures with 10 or more colony-forming units per milliliter of pathogenic organisms.

RESULTS

We admitted 704 intubated patients. A total of 437 were intubated for two or more days (mean [SD], age 46 [18] years; 65% male; median ventilator days, 4 [range, 2-9]; median Sequential Organ Failure Assessment [SOFA] score, 8 [range, 5-10]). Using VAE criteria, we identified 37 patients with VAC, 31 with infection-related VAC, and 22 with PrVAP. While the remaining 400 patients did not meet VAE criteria, we identified 111 patients (28%) with respiratory deterioration and diagnosed 99 additional pneumonias. Of the 111 patients, 85 (77%) never had a period of stable/decreasing oxygenation, requiring elevated vent settings upon initiation of ventilation preventing them from meeting VAE criteria. Of the 99 pneumonia patients, 10% had sustained respiratory deterioration treated with elevations in mean airway pressure; they did not meet VAE criteria as the positive end-expiratory pressure or FIO2 was not elevated. Twenty-seven percent never had a period of stable/decreasing oxygenation. Fifty-eight percent had less than 2 days of respiratory deterioration. Agreement between PrVAP and clinical VAP was 77.3% (κ = 0.243, p < 0.001).

CONCLUSION

The applicability of the new National Healthcare Safety Network categories of VAE to critically ill surgery patients is limited. Agreement between PrVAP and clinical VAP in SICU patients is poor. Most surgical patients are not well categorized by this new definition; a better method of surveillance should be created for this patient population.

LEVEL OF EVIDENCE

Diagnostic study, level III.

Computed tomography pulmonary angiography: more than a screening tool for pulmonary embolus

BACKGROUND

Traumatically injured patients have multiple causes for acute respiratory decompensation. We reviewed the use of computed tomography pulmonary angiography (CTPA) in critically injured patients to evaluate the results and impact on patient care.

METHODS

The charts of trauma patients (age >16 years) admitted to our intensive care unit for greater than 48 hours, who underwent CTPA for acute respiratory decompensation, were reviewed to determine the results of these studies and the effect on patient care.

RESULTS

We identified 188 patients who underwent CTPA for acute physiologic changes. Pertinent clinical finding were identified in 95% of studies and included atelectasis/collapse (56%), pleural effusion (18%), pneumonia (15%), and pulmonary embolus (18%). These results prompted interventions designed to improve patient outcome. The most frequent interventions were modifications of ventilator therapy (52%), antibiotic therapy (28%), mini-bronchoalveolar lavage (15%), or bronchoscopy (15%). Diagnostic agreement between chest x-ray and CTPA was poor to moderate (κ = 0.013-0.512).

CONCLUSIONS

Computed tomography pulmonary angiography is valuable in the evaluation of cardiopulmonary deterioration in critically ill traumatically injured patients. Computed tomography pulmonary angiography offers the ability to identify causes of acute physiologic changes not detected using standard chest x-ray. The results of these studies provide insight into the underlying pathophysiology and offer an opportunity to direct subsequent patient care.

Fat embolism in pediatric patients: an autopsy evaluation of incidence and etiology

INTRODUCTION

Little is known about the incidence and etiology of fat embolism in pediatric patients. We sought to determine the incidence, time course, and associated factors of pulmonary fat embolism (PFE), cerebral fat embolism (CFE), and kidney fat embolism (KFE) in trauma and nontrauma pediatric patients at the time of autopsy.

METHODS

Retrospectively, a convenience sample of consecutive pediatric patients (age, ≤10 years) who had undergone autopsy between 2008 and 2012 were evaluated for fat embolism. Patients who had no documented cause of death or who were hospital births and died during the same hospitalization were excluded. Formalin-fixed paraffin sections were reviewed by a forensic pathologist for evidence of fat embolism and nuclear elements. Autopsy reports were used to determine cause of death, injuries, resuscitative efforts taken, sex, height, weight, and age.

RESULTS

Sixty-seven decedents were evaluated. The median age was 2.0 years (interquartile range, 0.75-4), median body mass index (BMI) was 18.0 kg/m(2) (interquartile range, 15.7-19.0 kg/m(2)), and 55% of the patients were male. Pulmonary fat embolism, CFE, and KFE were present in 30%, 15%, and 3% of all patients, respectively. The incidence of PFE was not significantly different by cause of death (trauma 33%, drowning 36%, burn 14%, medical 28%). Patients with PFE but not CFE had significantly higher age, height, weight, and BMI. Half of the PFE and 57% of the CFE occurred in patients who lived less than 1 hour after beginning of resuscitation. Seventy-one percent of patients with CFE did not have a patent foramen ovale. Multivariate regression revealed an increased odds ratio of PFE based on BMI (1.244 [95% confidence interval, 1.043-1.484], P = .015). None of the samples evaluated demonstrated nuclear elements.

CONCLUSIONS

Pulmonary fat embolism, CFE, and KFE are common in pediatric trauma and medical deaths. Body mass index is independently associated with the development of PFE. Absence of nuclear elements suggests that fat embolism did not originate from intramedullary fat.

Surgical rib fixation for flail chest deformity improves liberation from mechanical ventilation

PURPOSE

The goal of this study was to determine the impact of surgical rib fixation (SRF) in a treatment protocol for severe blunt chest trauma.

MATERIALS AND METHODS

Patients with flail chest admitted between September 2009 and June 2010 to our level I trauma center who failed traditional management and underwent SRF were matched with an historical group. Outcome variables evaluated include age, injury severity score, intensive care unit length of stay (LOS), hospital LOS, ventilator days, total number of rib fractures, and total number of segmental rib fractures.

RESULTS

The 2 groups were similar in age, injury severity score, intensive care unit LOS, hospital LOS, total number of rib fractures, and total segmental rib fractures. The operative group demonstrated a significant reduction in total ventilator days as compared with the nonsurgical group (4.5 [0-30] vs 16.0 [4-40]; P = .040). Patients with SRF were permanently liberated from the ventilator within a median of 1.5 days (0-8 days).

CONCLUSIONS

Surgical rib fixation resulted in a significant decrease in ventilator days and may represent a novel approach to decreasing morbidity in flail chest patients when used as a rescue therapy in patients with declining pulmonary status. Larger studies are required to further identify these benefits.

Examination with next-generation sequencing technology of the bacterial microbiota in bronchoalveolar lavage samples after traumatic injury

BACKGROUND

We examined the microbiota of bronchoalveolar lavage (BAL) samples with next-generation sequencing (NGS) technology to determine whether its results correlate with those of standard culture methods or affect patient outcome or both.

METHODS

We collected BAL samples in the surgical intensive care unit (SICU) as part of the standard of care for intubated individuals who had a Clinical Pulmonary Infection Score (CPIS)≥6 points. A portion of the BAL fluid was sequenced for the 16S region of ribosomal deoxyribonucleic acid (rDNA) with the Roche 454 FLX Titanium sequencer. Sequences were analyzed through a data-analysis pipeline to identify the appropriate taxonomic designation (∼species) of each 16s sequence. The bacterial microbiota of each BAL sample was compared with the bacteria identified in the sample through standard culture methods. Correlations between the taxonomic diversity of the microbiota and clinical outcome were examined through linear regression and Pearson correlation.

RESULTS

Bronchoalveolar lavage samples from 12 individuals in the SICU who had a CPIS≥6 points were examined through 454 pyrosequencing. The number of phylotypes (∼species) in the samples ranged from 15 to 129. The number of phyla in the BAL samples ranged from 3 to 14. There was little correlation between the bacteria identified by NGS and those identified with standard culture methods. The same predominant bacterial strain was identified by both culture and sequencing in only a single sample. The correlation between patient days on a ventilator and the number of species in BAL samples was significant (r=0.7435, p=0.0056; r2=0.5528).

CONCLUSIONS

Increasing diversity of the bacterial microbiota in BAL samples correlates with the duration of mechanical ventilation. Bacteria identified through standard culture methods were not well correlated with the findings of NGS.