Bench-to-bedside review: Future novel diagnostics for sepsis - a systems biology approach

The early, accurate diagnosis and risk stratification of sepsis remains an important challenge in the critically ill. Since traditional biomarker strategies have not yielded a gold standard marker for sepsis, focus is shifting towards novel strategies that improve assessment capabilities. The combination of technological advancements and information generated through the human genome project positions systems biology at the forefront of biomarker discovery. While previously available, developments in the technologies focusing on DNA, gene expression, gene regulatory mechanisms, protein and metabolite discovery have made these tools more feasible to implement and less costly, and they have taken on an enhanced capacity such that they are ripe for utilization as tools to advance our knowledge and clinical research. Medicine is in a genome-level era that can leverage the assessment of thousands of molecular signals beyond simply measuring selected circulating proteins. Genomics is the study of the entire complement of genetic material of an individual. Epigenetics is the regulation of gene activity by reversible modifications of the DNA. Transcriptomics is the quantification of the relative levels of messenger RNA for a large number of genes in specific cells or tissues to measure differences in the expression levels of different genes, and the utilization of patterns of differential gene expression to characterize different biological states of a tissue. Proteomics is the large-scale study of proteins. Metabolomics is the study of the small molecule profiles that are the terminal downstream products of the genome and consists of the total complement of all low-molecular-weight molecules that cellular processes leave behind. Taken together, these individual fields of study may be linked during a systems biology approach. There remains a valuable opportunity to deploy these technologies further in human research. The techniques described in this paper not only have the potential to increase the spectrum of diagnostic and prognostic biomarkers in sepsis, but they may also enable the discovery of new disease pathways. This may in turn lead us to improved therapeutic targets. The objective of this paper is to provide an overview and basic framework for clinicians and clinical researchers to better understand the 'omics technologies' to enhance further use of these valuable tools

Utilizing the Boston Syncope Observation Management Pathway to Reduce Hospital Admission and Decrease Adverse Outcomes

Introduction: In an age of increasing scrutiny of each hospital admission, emergency department (ED) observation has been identified as a low-cost alternative. Prior studies have shown admission rates for syncope in the United States to be as high as 70%. However, the safety and utility of substituting ED observation unit (EDOU) syncope management has not been well studied. The objective of this study was to evaluate the safety of EDOU for the management of patients presenting to the ED with syncope and its efficacy in reducing hospital admissions. Methods: This was a prospective before-and-after cohort study of consecutive patients presenting with syncope who were seen in an urban ED and were either admitted to the hospital, discharged, or placed in the EDOU. We first performed an observation study of syncope management and then implemented an ED observation-based management pathway. We identified critical interventions and 30-day outcomes. We compared proportions of admissions and adverse events rates with a chisquared or Fisher’s exact test. Results: In the “before” phase, 570 patients were enrolled, with 334 (59%) admitted and 27 (5%) placed in the EDOU; 3% of patients discharged from the ED had critical interventions within 30 days and 10% returned. After the management pathway was introduced, 489 patients were enrolled; 34% (p\u3c0.001) of pathway patients were admitted while 20% were placed in the EDOU; 3% (p=0.99) of discharged patients had critical interventions at 30 days and 3% returned (p=0.001). Conclusion: A focused syncope management pathway effectively reduces hospital admissions and adverse events following discharge and returns to the ED. [West J Emerg Med. 2019;20(2)250–255.

Plasma Levels of Mitochondrial DNA in Patients Presenting to the Emergency Department with Sepsis

Introduction Elevated levels of plasma mitochondrial DNA (mtDNA) have been reported in trauma patients, and may contribute to the systemic immune response. We sought to determine the plasma levels of mtDNA in emergency department (ED) patients with and without sepsis and evaluate their association with severity of illness. Methods Prospective observational study of patients presenting to one of three large, urban, tertiary care EDs. Patients were enrolled into one of three cohorts: 1) sepsis defined as suspected infection and two or more SIRS criteria without hypotension; 2) septic shock defined as sepsis plus hypotension despite an adequate fluid challenge; and 3) control defined as non-infected ED patients without SIRS/hypotension. Plasma levels of three mtDNAs were measured using real-time quantitative PCR. Levels of mtDNAs were compared between the three cohorts and linear regression was used to assess the association between mtDNAs, IL-6, IL-10, and sequential organ failure assessment (SOFA) scores in patients with sepsis. Results We enrolled 93 patients: 24 controls, 29 with sepsis, and 40 with septic shock. As expected, co-morbidities and SOFA score increased across categories. We found no difference in mtDNA levels between the three groups (p = 0.14-0.30). Among patients with sepsis, we found a small but significant negative association between mtDNA level and SOFA score, most clearly with cytochrome b (p=0.03). Conclusions We found no difference in mtDNA levels between controls and patients with sepsis. mtDNA levels were negatively associated with organ dysfunction, suggesting that plasma mtDNA does not significantly contribute to the pathophysiology of sepsis

Soluble adhesion molecules as markers for sepsis and the potential pathophysiological discrepancy in neonates, children and adults

Sepsis is a severe and life-threatening systemic inflammatory response to infection that affects all populations and age groups. The pathophysiology of sepsis is associated with aberrant interaction between leukocytes and the vascular endothelium. As inflammation progresses, the adhesion molecules that mediate these interactions become shed from cell surfaces and accumulate in the blood as soluble isoforms that are being explored as potential prognostic disease biomarkers. We critically review the studies that have tested the predictive value of soluble adhesion molecules in sepsis pathophysiology with emphasis on age, as well as the underlying mechanisms and potential roles for inflammatory shedding. Five soluble adhesion molecules are associated with sepsis, specifically, E-selectin, L-selectin and P-selectin, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. While increased levels of these soluble adhesion molecules generally correlate well with the presence of sepsis, their degree of elevation is still poorly predictive of sepsis severity scores, outcome and mortality. Separate analyses of neonates, children and adults demonstrate significant age-dependent discrepancies in both basal and septic levels of circulating soluble adhesion molecules. Additionally, a range of both clinical and experimental studies suggests protective roles for adhesion molecule shedding that raise important questions about whether these should positively or negatively correlate with mortality. In conclusion, while predictive properties of soluble adhesion molecules have been researched intensively, their levels are still poorly predictive of sepsis outcome and mortality. We propose two novel directions for improving clinical utility of soluble adhesion molecules: the combined simultaneous analysis of levels of adhesion molecules and their sheddases; and taking age-related discrepancies into account. Further attention to these issues may provide better understanding of sepsis pathophysiology and increase the usefulness of soluble adhesion molecules as diagnostic and predictive biomarkers

Lactate Clearance vs Central Venous Oxygen Saturation as Goals of Early Sepsis Therapy: A Randomized Clinical Trial

Context Goal-directed resuscitation for severe sepsis and septic shock has been reported to reduce mortality when applied in the emergency department. Objective To test the hypothesis of noninferiority between lactate clearance and central venous oxygen saturation (ScvO2) as goals of early sepsis resuscitation. Design, Setting, and Patients Multicenter randomized, noninferiority trial involving patients with severe sepsis and evidence of hypoperfusion or septic shock who were admitted to the emergency department from January 2007 to January 2009 at 1 of 3 participating US urban hospitals. Interventions We randomly assigned patients to 1 of 2 resuscitation protocols. The ScvO2 group was resuscitated to normalize central venous pressure, mean arterial pressure, and ScvO2 of at least 70%; and the lactate clearance group was resuscitated to normalize central venous pressure, mean arterial pressure, and lactate clearance of at least 10%. The study protocol was continued until all goals were achieved or for up to 6 hours. Clinicians who subsequently assumed the care of the patients were blinded to the treatment assignment. Main Outcome Measure The primary outcome was absolute in-hospital mortality rate; the noninferiority threshold was set at Δ equal to −10%. Results Of the 300 patients enrolled, 150 were assigned to each group and patients were well matched by demographic, comorbidities, and physiological features. There were no differences in treatments administered during the initial 72 hours of hospitalization. Thirty-four patients (23%) in the ScvO2 group died while in the hospital (95% confidence interval [CI], 17%-30%) compared with 25 (17%; 95% CI, 11%-24%) in the lactate clearance group. This observed difference between mortality rates did not reach the predefined −10% threshold (intent-to-treat analysis: 95% CI for the 6% difference, −3% to 15%). There were no differences in treatment-related adverse events between the groups. Conclusion Among patients with septic shock who were treated to normalize central venous and mean arterial pressure, additional management to normalize lactate clearance compared with management to normalize ScvO2 did not result in significantly different in-hospital mortality

Outcomes of Patients Undergoing Early Sepsis Resuscitation for Cryptic Shock Compared with Overt Shock

Introduction We sought to compare the outcomes of patients with cryptic versus overt shock treated with an emergency department (ED) based early sepsis resuscitation protocol. Methods Pre-planned secondary analysis of a large, multicenter ED-based randomized controlled trial of early sepsis resuscitation. All subjects were treated with a quantitative resuscitation protocol in the ED targeting 3 physiological variables: central venous pressure, mean arterial pressure and either central venous oxygen saturation or lactate clearance. The study protocol was continued until all endpoints were achieved or a maximum of 6 h. Outcomes data of patients who were enrolled with a lactate ≥4 mmol/L and normotension (cryptic shock) were compared to those enrolled with sustained hypotension after fluid challenge (overt shock). The primary outcome was in-hospital mortality. Results A total of 300 subjects were enrolled, 53 in the cryptic shock group and 247 in the overt shock group. The demographics and baseline characteristics were similar between the groups. The primary endpoint of in-hospital mortality was observed in 11/53 (20%, 95% CI 11–34) in the cryptic shock group and 48/247 (19%, 95% CI 15–25) in the overt shock group, difference of 1% (95% CI −10 to 14; log rank test p = 0.81). Conclusion Severe sepsis with cryptic shock carries a mortality rate not significantly different from that of overt septic shock. These data suggest the need for early aggressive screening for and treatment of patients with an elevated serum lactate in the absence of hypotension

Association Between Early Hyperoxia Exposure After Resuscitation From Cardiac Arrest and Neurological Disability: Prospective Multicenter Protocol-Directed Cohort Study

BACKGROUND: Studies examining the association between hyperoxia exposure after resuscitation from cardiac arrest and clinical outcomes have reported conflicting results. Our objective was to test the hypothesis that early postresuscitation hyperoxia is associated with poor neurological outcome. METHODS: This was a multicenter prospective cohort study. We included adult patients with cardiac arrest who were mechanically ventilated and received targeted temperature management after return of spontaneous circulation. We excluded patients with cardiac arrest caused by trauma or sepsis. Per protocol, partial pressure of arterial oxygen (Pao2) was measured at 1 and 6 hours after return of spontaneous circulation. Hyperoxia was defined as a Pao2 >300 mm Hg during the initial 6 hours after return of spontaneous circulation. The primary outcome was poor neurological function at hospital discharge, defined as a modified Rankin Scale score >3. Multivariable generalized linear regression with a log link was used to test the association between Pao2 and poor neurological outcome. To assess whether there was an association between other supranormal Pao2 levels and poor neurological outcome, we used other Pao2 cut points to define hyperoxia (ie, 100, 150, 200, 250, 350, 400 mm Hg). RESULTS: Of the 280 patients included, 105 (38%) had exposure to hyperoxia. Poor neurological function at hospital discharge occurred in 70% of patients in the entire cohort and in 77% versus 65% among patients with versus without exposure to hyperoxia respectively (absolute risk difference, 12%; 95% confidence interval, 1-23). Hyperoxia was independently associated with poor neurological function (relative risk, 1.23; 95% confidence interval, 1.11-1.35). On multivariable analysis, a 1-hour-longer duration of hyperoxia exposure was associated with a 3% increase in risk of poor neurological outcome (relative risk, 1.03; 95% confidence interval, 1.02-1.05). We found that the association with poor neurological outcome began at ≥300 mm Hg. CONCLUSIONS: Early hyperoxia exposure after resuscitation from cardiac arrest was independently associated with poor neurological function at hospital discharge

Prognostic Value and Agreement of Achieving Lactate Clearance or Central Venous Oxygen Saturation Goals During Early Sepsis Resuscitation

Objectives:  Lactate clearance (LC) and central venous oxygen saturation (ScvO2) have been proposed as goals of early sepsis resuscitation. The authors sought to determine the agreement and prognostic value of achieving ScvO2 or LC goals in septic shock patients undergoing emergency department (ED)-based early resuscitation. Methods:  This was a preplanned analysis of a multicenter ED randomized controlled trial of early sepsis resuscitation targeting three variables: central venous pressure, mean arterial pressure, and either ScvO2 or LC. Inclusion criteria included suspected infection, two or more systemic inflammation criteria, and either systolic blood pressure of 4 mmol/L. Both ScvO2 and LC were measured simultaneously. The ScvO2 goal was defined as ≥70%. Lactate was measured at enrollment and every 2 hours until the goal was reached or up to 6 hours. LC goal was defined as a decrease of ≥10% from initial measurement. The primary outcome was in-hospital mortality. Results:  A total of 203 subjects were included, with an overall mortality of 19.7%. Achievement of the ScvO2 goal only was associated with a mortality rate of 41% (9/22), while achievement of the LC goal only was associated with a mortality rate of 8% (2/25; proportion difference = 33%; 95% confidence interval [CI] = 9% to 55%). No agreement was found between goal achievement (κ = –0.02), and exact test for matched pairs demonstrated no significant difference between discordant pairs (p = 0.78). Conclusions:  No agreement was found between LC and ScvO2 goal achievement in early sepsis resuscitation. Achievement of a ScvO2≥ 70% without LC ≥ 10% was more strongly associated with mortality than achievement of LC ≥ 10% with failure to achieve ScvO2≥ 70%