The future is predetermined in severe sepsis, so what are the implications?:

The Neutrophil: Constant Defender and First Responder

The role of polymorphonuclear neutrophils (PMNs) in biology is often recognized during pathogenesis associated with PMN hyper- or hypo-functionality in various disease states. However, in the vast majority of cases, PMNs contribute to resilience and tissue homeostasis, with continuous PMN-mediated actions required for the maintenance of health, particularly in mucosal tissues. PMNs are extraordinarily well-adapted to respond to and diminish the damaging effects of a vast repertoire of infectious agents and injurious processes that are encountered throughout life. The commensal biofilm, a symbiotic polymicrobial ecosystem that lines the mucosal surfaces, is the first line of defense against pathogenic strains that might otherwise dominate, and is therefore of critical importance for health. PMNs regularly interact with the commensal flora at the mucosal tissues in health and limit their growth without developing an overt inflammatory reaction to them. These PMNs exhibit what is called a para-inflammatory phenotype, and have reduced inflammatory output. When biofilm growth and makeup are disrupted (i.e., dysbiosis), clinical symptoms associated with acute and chronic inflammatory responses to these changes may include pain, erythema and swelling. However, in most cases, these responses indicate that the immune system is functioning properly to re-establish homeostasis and protect the status quo. Defects in this healthy everyday function occur as a result of PMN subversion by pathological microbial strains, genetic defects or crosstalk with other chronic inflammatory conditions, including cancer and rheumatic disease, and this can provide some avenues for therapeutic targeting of PMN function. In other cases, targeting PMN functions could worsen the disease state. Certain PMN-mediated responses to pathogens, for example Neutrophil Extracellular Traps (NETs), might lead to undesirable symptoms such as pain or swelling and tissue damage/fibrosis. Despite collateral damage, these PMN responses limit pathogen dissemination and more severe damage that would otherwise occur. New data suggests the existence of unique PMN subsets, commonly associated with functional diversification in response to particular inflammatory challenges. PMN-directed therapeutic approaches depend on a greater understanding of this diversity. Here we outline the current understanding of PMNs in health and disease, with an emphasis on the positive manifestations of tissue and organ-protective PMN-mediated inflammation.

Antibiotics in the first hour: is there new evidence?

INTRODUCTION

International guidelines have recommended for many years to start antimicrobials as early as possible in sepsis and shock. This concept has been challenged by the controversial results of experimental studies and clinical cohorts and resulted in intense debate in the literature. This review aims to summarize the available knowledge on early antimicrobial therapy and to consider perspectives.

AREAS COVERED

First, after a research using MEDLINE, we reviewed the studies that advocated the implementation of early antimicrobial therapy. We then discussed the drawbacks of these studies. Finally, we suggested possible explanations of the benefit and then absence of the prognostic impact of early antimicrobial therapy i.e. confounding factors, irreversibility of the inflammatory process, non-control of the source of the infection, pharmacodynamic considerations and the harmful effect of antimicrobial drugs.

EXPERT OPINION

Sepsis is very heterogeneous. The first antimicrobial therapy should be personalized. The sickest patients should be given early antimicrobial therapy, whereas a 'watch and wait process' should be preferred for less severe patients, to allow confirmation of sepsis, identification of pathogens and administration of adequate antimicrobial therapy. We propose steps to personalize the first antimicrobial therapy. New early diagnostic tools will assist the physicians in the future.

Heart rate elevations during early sepsis predict death in fluid-resuscitated rats with fecal peritonitis

BACKGROUND

In sepsis, early outcome prediction would allow investigation of both adaptive mechanisms underlying survival and maladaptive mechanisms resulting in death. The aim of this study was to test whether early changes in heart rate monitored by telemetry could predict outcome in a long-term rat model of fecal peritonitis.

METHODS

Male Wistar rats (n = 24) were instrumented with a central venous line for administration of fluids, antibiotics and analgesics. A telemetry transmitter continuously collected electrocardiogram signals. Sepsis was induced by intraperitoneal injection of fecal slurry, and the animals were observed for 48 h. Additional animals underwent arterial cannulation at baseline (n = 9), 4 h (n = 16), or 24 h (n = 6) for physiology and laboratory measurements.

RESULTS

48-h mortality was 33% (8/24), with all deaths occurring between 4 and 22 h. Septic animals were characterized by lethargy, fever, tachycardia, positive blood cultures, and elevated cytokine (IL-1, IL-6, TNF alpha) levels. An increase in heart rate ≥ 50 bpm during the first 4 h of sepsis predicted death with sensitivity and specificity of 88% (p = 0.001).

CONCLUSIONS

In this long-term rat sepsis model, prognostication could be made early by telemetry-monitored changes in heart rate. This model enables the study of underlying mechanisms and the assessment of any differential effects of novel therapies in predicted survivors or non-survivors.

Melanocortin-1 Receptor Polymorphisms and the Risk of Complicated Sepsis After Trauma: A Candidate Gene Association Study

OBJECTIVE

The aim of the study was to determine if melanocortin-1 receptor (MC1R) single nucleotide polymorphisms (SNPs) are associated with complicated sepsis after trauma.

BACKGROUND

Nosocomial infections are an important cause of morbidity and mortality after trauma. Several SNPs in inflammation-related genes have been associated with sepsis. MC1R is an anti-inflammatory mediator that may be involved in the immune response after trauma.

PATIENTS AND METHODS

We genotyped eight common MC1R SNPs in genomic DNA from subjects enrolled in a previously reported prospective cohort study. Subjects were adult trauma patients admitted to the intensive care unit at a Level 1 trauma center (2003-2005).

RESULTS

A total of 1,246 subjects were included in the analysis. The majority were male (70%), severely injured (81%), and injured by a blunt mechanism (89%). Forty percent developed sepsis, and 23% developed complicated sepsis, which was defined as sepsis with organ dysfunction. In logistic regression analysis, with adjustments for age, sex, body mass index, injury severity score, red blood cell transfusion requirement, and mechanism of injury, the MC1RR163Q variant (rs885479) was associated with a lower risk of developing complicated sepsis (adjusted odds ratio [ORadj] = 0.48, 95% confidence interval [CI]: 0.28-0.81, P = 0.006). In a subgroup of 511 subjects with genome-wide SNP data, the association between the MC1RR163Q variant and complicated sepsis remained significant after adjusting for genetic substructure (by principal components) and the above clinical factors (ORadj = 0.30, 95% CI: 0.13-0.70, P = 0.005).

CONCLUSIONS

MC1RR163Q is associated with a lower risk of complicated sepsis after trauma. Therapeutic targeting of MC1R may be beneficial for trauma patients at risk for complicated sepsis.

Clinical predictors of adverse outcome in severe sepsis patients with lactate 2-4 mM admitted to the hospital

BACKGROUND

Severe sepsis patients with initial lactate level 2-4 mM are commonly considered to have lower risk for mortality and adverse outcomes.

AIM

We aim to determine clinical variables that are associated with adverse outcome in these patients.

DESIGN

A retrospective cohort study.

METHODS

Severe sepsis patients with initial lactate ≥ 2 and < 4 mM admitted to our hospital were examined for any of the following primary outcomes: (i) in-hospital death, (ii) vasopressor requirement, (iii) use of mechanical ventilator, (iv) lactate ≥ 4.0 mM or (v) need care in the intensive care unit (ICU) within 48 h.

RESULTS

Five-hundred and thirty-five patients were enrolled, age 58.7 ± 19.3 years, 53.2% male. The most common sources of infection were urinary tract infection and pneumonia, 38.3 and 35.7%, respectively. One-hundred and twenty-four (23.2%) patients had at least one primary adverse outcome within 48 h, including in-hospital death 1.1%, vasopressor requirement 12.9%, use of mechanical ventilator 13.3%, increase lactate ≥ 4.0 mM in 5.6% patients and 21.5% of patients requiring ICU (including 13.8% of the patients admitted directly to ICU from the emergency department, and 7.7% initially admitted to the general medical ward but later required ICU transfer). Altered mentation, hypotension, tachypnea and elevated blood urea nitrogen at admission were associated with the primary outcome in multivariable logistic regression analysis, odds ratio 2.50 (95% confidence interval: 1.54, 4.06), 3.76 (2.31, 6.10), 1.97 (1.22, 3.17) and 1.78 (1.11, 2.83), respectively.

CONCLUSIONS

Our study suggests that clinicians should be cautious about the potential adverse outcomes in severe sepsis patients with initial lactate level between 2 and 4 mM and a presentation of altered mentation, hypotension, tachypnea and/or elevated blood urea nitrogen.

Is there an association between central vein stenosis and line infection in patients with tunnelled central venous catheters (TCVCs)?

PURPOSE

Central vein stenosis (CVS) and line infection are well-recognized complications of tunnelled central venous catheters (TCVCs) in patients on haemodialysis. The aim of this study was to evaluate any relationship between CVS and line infection.

METHODS

Analysis of 500 consecutive patients undergoing TCVC insertion was undertaken. Data were collected on patient demographics, details of line insertion and duration, culture-proven bacteraemia and presence of symptomatic CVS. Logistic regression analysis was used to determine risk factors for CVS and bacteraemia.

RESULTS

Mean patient age was 59.0 years (range: 17-93). Mean number of catheter days was 961.1 ± 57.6 per TCVC; 39.4% of TCVCs were associated with culture-proven bacteraemia and 23.6% developed symptomatic CVS. Bacteraemia and CVS were inevitable complications of all TCVCs. The time to symptomatic CVS was longer in patients with bacteraemia than without (1230.91 ± 101.29 vs. 677.49 ± 61.59 days, p<0.001). Patients who had early infection within 90 days of TCVC insertion were less likely to develop CVS (5.9% vs. 22.8%, p<0.001). There was no difference in the bacteraemia rate per 1,000 catheter days between patients with and without CVS (2.62 ± 1.41 vs. 2.35 ± 0.51; p = 0.98). Number of line days (odds ratio (OR) 1.02, p = 0.003), age (OR 1.04, p = 0.04) and culture-proven line infection (OR 0.59, p = 0.014) were all independently associated with CVS.

CONCLUSIONS

Our results suggest that early line infection may be protective against CVS. Alternatively, there may be two distinct predisposition states for CVS and line infection. Further studies are needed to confirm our association and investigate causation.

Lectin pathway of complement activation and relation with clinical complications in critically ill children

BACKGROUND

Critically ill children are susceptible to nosocomial infections, which contribute to adverse outcomes. Deficiencies in the innate immunity lectin pathway of complement activation are implicated in a child's vulnerability to infections in conditions such as cancer, but the role during critical illness remains unclear. We hypothesized that low on-admission levels of the pathway proteins are, in part, genetically determined and associated with susceptibility to infectious complications and adverse outcomes.

METHODS

We studied protein levels of mannose-binding lectin (MBL), H-ficolin and M-ficolin, three MBL-associated-serine proteases (MASPs) and MBL-associated protein (MAp44), and relation with functional genetic polymorphisms, in 130 healthy children and upon intensive care unit (ICU) admission in 700 critically ill children of a randomized study on glycemic control.

RESULTS

Levels of MASP-1, MASP-2, MASP-3, and MAp-44 were lower and the levels of M-ficolin were higher in ICU patients on admission than those in matched healthy controls. Only a low on-admission MASP-3 level was independently associated with risk of new ICU infections and prolonged ICU stay, after correcting for other risk factors. On-admission MASP-3 varied with age, illness severity, and genetic variation.

CONCLUSION

Low on-admission MASP-3 levels in critically ill children were independently associated with subsequent acquisition of infection and prolonged ICU stay. The biological explanation needs further investigation.

Cytokine removal on extracorporeal life support for treatment of acute endotoxemia: a randomized controlled animal study

BACKGROUND

We prospectively evaluated the effectiveness of resin adsorption incorporated in an extracorporeal life support (ELS) circuit in an animal model of sepsis for removal of cytokines and prevention of hemodynamic deterioration during the treatment of septic shock.

METHODS

Twelve female landrace pigs were randomly assigned to two groups, a study group(n=6), treated with high-flow resin adsorption (300 mL/min) and ELS, and a control group (n=6), treated only with ELS. Septic shock was induced by intravenous 0.02 μg/kg/min infusion was of Escherichia coli lipopolysaccharide (LPS). Measurements were carried out in the study group at baseline, at the end of LPS injection(t0) at 30(t1), 60(t2), 90(t3) and 120 min (t4) and 60 min after stopping resin-adsorption (t5). In the control group measurements were performed at baseline (t0), t1 and only t2, as no control animal survived beyond this latter experimental timepoint.

RESULTS

The final population consisted of 9 animals, five in the study group and 4 in the control group. Plasma values of both tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) were reduced during resin-adsorption (t1-t4) while these mediators increased in controls undergoing ELS only. With a clearance of TNF-α of 15,233 pg/min and IL-6 of 10,233 pg/min, 79.2% of TNF-α and 95.3% of IL-6 produced were adsorbed. Systemic vascular resistance decreased significantly in both groups at t0. While it further was reduced during the control experiments at t1 and t2, it returned to normal in the study animals. Cardiac output increased at t0, t1 and t2 in the control experiments. In contrast, in study animals after a peak at t0, it returned to the baseline value and did not vary thereafter.

CONCLUSIONS

Combined resin-adsorption and ELS improved hemodynamics resulting from effective removal of inflammatory mediators in a pig model of septic shock.

Beyond single-marker analyses: mining whole genome scans for insights into treatment responses in severe sepsis

Management of severe sepsis, an acute illness with high morbidity and mortality, suffers from the lack of effective biomarkers and largely empirical predictions of disease progression and therapeutic responses. We conducted a genome-wide association study using a large randomized clinical trial cohort to discover genetic biomarkers of response to therapy and prognosis utilizing novel approaches, including combination markers, to overcome limitations of single-marker analyses. Sepsis prognostic models were dominated by clinical variables with genetic markers less informative. In contrast, evidence for gene-gene interactions were identified for sepsis treatment responses with genetic biomarkers dominating models for predicting therapeutic responses, yielding candidates for replication in other cohorts.

Influence of aging and hemorrhage injury on Sirt1 expression: possible role of myc-Sirt1 regulation in mitochondrial function

Trauma-hemorrhage (T-H) causes hypoxia and organ dysfunction. Mitochondrial dysfunction is a major factor for cellular injury due to T-H. Aging also has been known to cause progressive mitochondrial dysfunction. In order to study the effect of aging on T-H-induced mitochondrial dysfunction, we recently developed a rodent mitochondrial genechip with probesets representing mitochondrial and nuclear genes contributing to mitochondrial structure and function. Using this chip we recently identified signature mitochondrial genes altered following T-H in 6 and 22 month old rats; augmented expression of the transcription factor c-myc was the most pronounced. Based on reports of c-myc-IL6 collaboration and c-myc-Sirt1 negative regulation, we further investigated the expression of these regulatory factors with respect to aging and injury. Rats of ages 6 and 22 months were subjected to T-H or sham operation and left ventricular tissues were tested for cytosolic cytochrome c, mtDNA content, Sirt1 and mitochondrial biogenesis factors Foxo1, Ppara and Nrf-1. We observed increased cardiac cytosolic cytochrome c (sham vs T-H, p<0.03), decreased mitochondrial DNA content (sham vs T-H, p<0.05), and decreased Sirt1 expression (sham vs TH, p<0.05) following T-H and with progressing age. Additionally, expression of mitochondrial biogenesis regulating transcription factors Foxo1 and Nrf-1 was also decreased with T-H and aging. Based upon these observations we conclude that Sirt1 expression is negatively modulated by T-H causing downregulation of mitochondrial biogenesis. Thus, induction of Sirt1 is likely to produce salutary effects following T-H induced injury and hence, Sirt1 may be a potential molecular target for translational research in injury resolution.