Evaluation of a Multivalent Transcriptomic Metric for Diagnosing Surgical Sepsis and Estimating Mortality Among Critically Ill Patients

Importance

Rapid and accurate discrimination of sepsis and its potential severity currently require multiple assays with slow processing times that are often inconclusive in discerning sepsis from sterile inflammation.

Objective

To analyze a whole-blood, multivalent, host-messenger RNA expression metric for estimating the likelihood of bacterial infection and 30-day mortality and compare performance of the metric with that of other diagnostic and prognostic biomarkers and clinical parameters.

Design, Setting, and Participants

This prospective diagnostic and prognostic study was performed in the surgical intensive care unit (ICU) of a single, academic health science center. The analysis included 200 critically ill adult patients admitted with suspected sepsis (cohort A) or those at high risk for developing sepsis (cohort B) between July 1, 2020, and July 30, 2021.

Exposures

Whole-blood sample measurements of a custom 29-messenger RNA transcriptomic metric classifier for likelihood of bacterial infection (IMX-BVN-3) or 30-day mortality (severity) (IMX-SEV-3) in a clinical-diagnostic laboratory setting using an analysis platform (510[k]-cleared nCounter FLEX; NanoString, Inc), compared with measurement of procalcitonin and interleukin 6 (IL-6) plasma levels, and maximum 24-hour sequential organ failure assessment (SOFA) scores.

Main Outcomes and Measures

Estimated sepsis and 30-day mortality performance.

Results

Among the 200 patients included (124 men [62.0%] and 76 women [38.0%]; median age, 62.5 [IQR, 47.0-72.0] years), the IMX-BVN-3 bacterial infection classifier had an area under the receiver operating characteristics curve (AUROC) of 0.84 (95% CI, 0.77-0.90) for discriminating bacterial infection at ICU admission, similar to procalcitonin (0.85 [95% CI, 0.79-0.90]; P = .79) and significantly better than IL-6 (0.67 [95% CI, 0.58-0.75]; P < .001). For estimating 30-day mortality, the IMX-SEV-3 metric had an AUROC of 0.81 (95% CI, 0.66-0.95), which was significantly better than IL-6 levels (0.57 [95% CI, 0.37-0.77]; P = .006), marginally better than procalcitonin levels (0.65 [95% CI, 0.50-0.79]; P = .06), and similar to the SOFA score (0.76 [95% CI, 0.62-0.91]; P = .48). Combining IMX-BVN-3 and IMX-SEV-3 with procalcitonin or IL-6 levels or SOFA scores did not significantly improve performance. Among patients with sepsis, IMX-BVN-3 scores decreased over time, reflecting the resolution of sepsis. In 11 individuals at high risk (cohort B) who subsequently developed sepsis during their hospital course, IMX-BVN-3 bacterial infection scores did not decline over time and peaked on the day of documented infection.

Conclusions and Relevance

In this diagnostic and prognostic study, a novel, multivalent, transcriptomic metric accurately estimated the presence of bacterial infection and risk for 30-day mortality in patients admitted to a surgical ICU. The performance of this single transcriptomic metric was equivalent to or better than multiple alternative diagnostic and prognostic metrics when measured at admission and provided additional information when measured over time.

Sepsis-Induced Myopathy and Gut Microbiome Dysbiosis: Mechanistic Links and Therapeutic Targets

ABSTRACT

Sepsis is currently defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. The skeletal muscle system is among the host organ systems compromised by sepsis. The resulting neuromuscular dysfunction and impaired regenerative capacity defines sepsis-induced myopathy and manifests as atrophy, loss of strength, and hindered regeneration after injury. These outcomes delay recovery from critical illness and confer increased vulnerability to morbidity and mortality. The mechanisms underlying sepsis-induced myopathy, including the potential contribution of peripheral organs, remain largely unexplored. The gut microbiome is an immunological and homeostatic entity that interacts with and controls end-organ function, including the skeletal muscle system. Sepsis induces alterations in the gut microbiota composition, which is globally termed a state of "dysbiosis" for the host compared to baseline microbiota composition. In this review, we critically evaluate existing evidence and potential mechanisms linking sepsis-induced myopathy with gut microbiota dysbiosis.

Distinct immunologic endotypes are associated with clinical trajectory after severe blunt trauma and hemorrhagic shock

BACKGROUND

The genomic/cytokine "storm" after severe trauma is well described. However, the differing composition, magnitude and resolution of this response, and its relationship to clinical outcomes remain unclear.

METHODS

This is a secondary analysis of a prospective longitudinal cohort study of severely injured trauma patients in hemorrhagic shock. Peripheral blood sampling was performed at 0.5, 1, 4, 7, 14, and 28 days after injury for measurement of circulating immune biomarkers. K-means clustering using overall mean and trajectory slope of selected immunologic biomarkers were used to identify distinct temporal immunologic endotypes. Endotypes were compared with known clinical trajectories defined as early death (<14 days), chronic critical illness (CCI) (ICU length of stay of ≥14 days with persistent organ dysfunction), and rapid recovery (RAP) (ICU length of stay of <14 days with organ recovery).

RESULTS

The cohort included 102 subjects enrolled across 2 level 1 trauma centers. We identified three distinct immunologic endotypes (iA, iB, and iC), each with unique associations to clinical trajectory. Endotype iA (n = 47) exhibited a moderate initial proinflammatory response followed by a return to immunologic homeostasis, with a primary clinical trajectory of RAP (n = 44, 93.6%). Endotype iB (n = 44) exhibited an early hyperinflammatory response with persistent inflammation and immunosuppression, with the highest incidence of CCI (n = 10, 22.7%). Endotype iC (n = 11) exhibited a similar hyperinflammatory response, but with rapid return to immunologic homeostasis and a predominant trajectory of RAP (n = 9, 81.8%). Patients with endotype iB had the highest severity/duration of organ dysfunction and highest incidence of nosocomial infections (50%, p = 0.001), and endotype iB was the predominant endotype of patients who developed CCI (10 of 13 patients, 76.9%; p = 0.002).

CONCLUSION

We identified three distinct immunologic endotypes after severe injury differing the magnitude and duration of the early response. The clinical trajectory of CCI is characterized by an endotype (iB) defined by persistent alteration in inflammation/immunosuppression and is associated with poor clinical outcomes.

LEVEL OF EVIDENCE

Prognostic, level III.

Catheter ablation of atrial fibrillation in patients with heart failure with preserved ejection fraction: a systematic review and meta-analysis

Background

Catheter ablation improves clinical outcomes in symptomatic atrial fibrillation (AF) patients with heart failure (HF) with reduced ejection fraction (HFrEF). However, the role of catheter ablation in HF patients with a preserved ejection fraction (HFpEF) is less clear.

Purpose

To determine the efficacy of catheter ablation of AF in patients with HFpEF relative to those with HFrEF.

Methods

We performed an extensive literature search and systematic review of studies that compared AF recurrence at one year after catheter ablation of AF in patients with HFpEF versus those with HFrEF. Risk ratio (RR) 95% confidence intervals were measured using the Mantel-Haenszel method for dichotomous variables, where a RR&lt;1.0 favors the HFpEF group.

Results

Four studies with a total of 563 patients were included, of which 312 had HFpEF and 251 had HFrEF. All patients included were undergoing first time catheter ablation of AF. Patients with HFpEF experienced similar recurrence of AF one year after ablation on or off antiarrhythmic drugs compared to those with HFrEF (RR 0.87; 95% CI 0.69–1.10, p=0.24), as shown in Figure 1. Recurrence of AF was assessed with electrocardiography, Holter monitoring, and/or event monitoring at scheduled follow-up visits and final follow-up.

Conclusion

Based on the results of this meta-analysis, catheter ablation of AF in patients with HFpEF appears as efficacious in maintaining sinus rhythm as in those with HFrEF.

Funding Acknowledgement

Type of funding source: None

Chronic Critically Ill Septic Patients Exhibit Persistent Expression of Pro-Inflammatory Lipidomics

Objectives

In order to evaluate the therapeutic potential of resolvins to reduce inflammation in CCI-PICS, we recapitulated Glue Grant leukotriene and resolvin lipidomic scores above to quantify lipidomics in severe sepsis/septic shock survivors.

Methods

Ongoing University of Florida (UF) Sepsis Critical Illness Research Center (SCIRC) research studies indicate that Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS) occurs as a result of a self-perpetuating cycle of low-grade inflammation. However, specialized pro-resolving mediators (SPMs) – metabolically active lipid byproducts of omega-3 fatty acids – can promote inflammatory deceleration and resolution.,1 Post hoc analysis of the Glue Grant Data developed a mathematical lipidomic expression to better understand genes responsible for production and degradation of resolvins and leukotrienes.,2

Leukotriene Score = (ALOX5 * ALX5AP * LTA4H * LTB4R)/(HPGD + PTGR1 + CYP4F3)

Resolvin Score = [(ALOX5 * ALOX15) * (FPR2 + GPR32 + CMKLR1)]/(HPGD + PTGR1)

When the targeted genes were scored using a weighted scheme accounting for enzyme and receptor activity, patients with uncomplicated recoveries had higher resolvin scores (P &lt; 0.001) and lower leukotriene scores (P &lt; 0.001).

Utilizing our PICS patient data, we recapitulated the aforementioned lipidomic scores above to quantify expression in severe sepsis/septic shock survivors.

Results

Leukotriene and resolvin scores are depicted in Figure 1 at specific time points 0 (healthy controls), 3 hours, 1 and 14 days. The leukotriene score remains elevated consistent with ongoing inflammatory genotypic expression. Interestingly, the resolvin score also remains elevated in the CCI (Glue Grant complicated cohort) patient population when compared to our Rapid Recovery (RAP or uncomplicated) patients

*Accompanied by two graphs depicting correlating numerical values for the aforementioned Leukotriene and Resolvin scores.

Conclusions

In our patient population of sepsis survivors, the leukotriene score is similarly elevated to the complicated Glue Grant patients of polytrauma. The resolvin score, however, remains elevated in the CCI-PICS population compared to RAP; this is contrary to expected scores if resolution of inflammation is predicted.

Funding Sources

University of Florida.

Myeloid-derived suppressor cell function and epigenetic expression evolves over time after surgical sepsis

Background

Sepsis is an increasingly significant challenge throughout the world as one of the major causes of patient morbidity and mortality. Central to the host immunologic response to sepsis is the increase in circulating myeloid-derived suppressor cells (MDSCs), which have been demonstrated to be present and independently associated with poor long-term clinical outcomes. MDSCs are plastic cells and potentially modifiable, particularly through epigenetic interventions. The objective of this study was to determine how the suppressive phenotype of MDSCs evolves after sepsis in surgical ICU patients, as well as to identify epigenetic differences in MDSCs that may explain these changes.

Methods

Circulating MDSCs from 267 survivors of surgical sepsis were phenotyped at various intervals over 6 weeks, and highly enriched MDSCs from 23 of these samples were co-cultured with CD3/CD28-stimulated autologous T cells. microRNA expression from enriched MDSCs was also identified.

Results

We observed that MDSC numbers remain significantly elevated in hospitalized sepsis survivors for at least 6 weeks after their infection. However, only MDSCs obtained at and beyond 14 days post-sepsis significantly suppressed T lymphocyte proliferation and IL-2 production. These same MDSCs displayed unique epigenetic (miRNA) expression patterns compared to earlier time points.

Conclusions

We conclude that in sepsis survivors, immature myeloid cell numbers are increased but the immune suppressive function specific to MDSCs develops over time, and this is associated with a specific epigenome. These findings may explain the chronic and persistent immune suppression seen in these subjects.

Pediatric tracheotomy: is postoperative chest X-ray necessary?

A retrospective study of 101 children who underwent tracheotomy at the Children's Hospital of Pittsburgh from 1993 to 1996 was performed. The following criteria were reviewed in each patient: age, gender, race, prematurity, weight during tracheotomy, presence of preoperative airway support, duration of tracheotomy, nature (emergent versus elective), tracheotomy tube size, reason for tracheotomy, accompanying medical diagnoses, chest x-ray (CXR) findings, surgical service, postoperative symptoms (up to 3 days), and operative mortality rate. Of these criteria, our results show that CXR-screenable complications occurred in patients who underwent emergent recannulation, as well as those who exhibited ventilatory distress (oxygen saturation level of <90%) and specific changes in postoperative symptoms. Pneumothorax developed after tracheotomy in 3 of the 101 patients; each had one of these risk factors. We conclude that CXR of all pediatric patients after tracheotomy may be unnecessary with the use of flexible endoscopy and screening restrictions that are both health-conscious and cost-effective.