Protein C, protein S and C4b-binding protein in neonatal severe infection and septic shock

A Global Assessment of Coagulation Profile and a Novel Insight into Adamts-13 Implication in Neonatal Sepsis

Neonatal sepsis is a life-threatening condition associated with significant morbidity and mortality. Sepsis-induced coagulopathy is a well-recognized entity, signifying the strong cross-talk between inflammation and coagulation. The aim of the present study was to compare the coagulation profile between the acute phase of sepsis and recovery in term and preterm neonates. Additional comparisons to healthy neonates were undertaken. Levels of clotting, anti-clotting factors and ADAMTS-13 (A disintegrin and metalloprotease with thrombospondin type-1 motives), the cleaving protein of von Willebrand factor (VWF), were measured in 16 term and preterm neonates in the acute phase of infection and following recovery, as well as in 18 healthy neonates. Clotting times were prolonged, while levels of particular clotting factors were lower in the acute phase of infection compared to controls and recovery. On the other hand, levels of fibrinogen, factor VIII (FVIII) and VWF were significantly higher in the acute phase in comparison to controls and recovery, while they remained persistently higher in the infection group compared to controls. In regard to the anticlotting mechanism, a clear suppression was observed in septic neonates. ADAMTS-13 levels were significantly lower in the acute phase of infection in comparison to controls and recovery (p = 0.015 and 0.004, respectively), while a trend toward superimposed normalization was demonstrated post infection, as higher ADAMTS-13 levels were measured in recovered neonates compared to controls (p = 0.002). The coagulation profile is considerably deranged in neonatal sepsis. ADAMTS-13 deficiency in septic neonates is a novel finding with promising future implications, as ADAMTS-13 substitution may serve as a useful therapeutic option in neonatal sepsis, prompting further investigation in future studies.

Protein C Pathway in Paediatric and Neonatal Sepsis

Protein C plays a major role in the physiological regulation of coagulation pathways through inactivation of factor Va, factor VIIIa, and plasminogen activator inhibitor. Protein C is involved in the control of inflammation during sepsis, by inhibiting release of pro-inflammatory cytokines, thereby controlling neutrophil, and monocyte effects on injured tissue. Recombinant human activated protein C (rhAPC) reduced mortality in adult sepsis in earlier studies but had no significant benefit in more recent trials. Protein C levels are reduced during paediatric and neonatal sepsis, which may play a major role in the development of disseminated intravascular thrombosis, purpura fulminans, and multiorgan dysfunction. The role of protein C in paediatric sepsis requires further clinical and immunological evaluation to define the patient subgroups who may benefit from this therapy. Newer versions of rhAPC are under development with less risk of haemorrhage potentially broadening the scope of this intervention.

Successful management of neonatal myocardial infarction with ECMO and intracoronary r-tPA lysis

Acute myocardial infarction (MI) is a life-threatening condition rarely encountered in neonates. The patients usually present with sudden cardiogenic shock. Clinical management in neonates is extremely challenging. If treatment is delayed, the prognosis is dismal. We report on a 4-day-old full-term male newborn presenting with acute MI and cardiogenic shock secondary to proximal thromboembolic occlusion of the left descending coronary artery. Hemodynamic stabilization could only be achieved after extracorporeal membrane oxygenation (ECMO) support. Coronary artery patency restoration was performed by selective intracoronary lysis with recombinant tissue plasminogen activator (r-tPA). ECMO support could be discontinued and myocardial function recovered within 6 weeks. We discuss the potential etiologies of acute perinatal MI and the role of ECMO support in the immediate post-MI period. Prompt recognition, timely referral to a cardiac center with availability of specialized advanced treatment options, and management in an orchestrated interdisciplinary approach are crucial for achieving a good outcome.

Study of protein C, protein S, and antithrombin III in newborns with sepsis

OBJECTIVE

The aim of this study is to clarify the effect of sepsis on the physiologic inhibition system of coagulation including protein S, protein C, and antithrombin III, and to study their further effect on thromboembolic accidents of septic newborns.

DESIGN

Clinical study including 30 septic neonates and 30 normal neonates served as control group.

DATA SOURCES

MEDLINE, pediatric textbooks, Neonatal Intensive Care Unit, Department of Pediatrics, Faculty of Medicine, Cairo University.

RESULTS

The results of this study showed marked decrease in the level of the physiologic inhibition system of coagulation including antithrombin III, protein C, and protein S in 100% of cases, compared to the control group (p < .001). Disseminated intravascular coagulation developed and death occurred in 33.3% of cases, necrotizing enterocolitis developed in 40% of cases, rectal bleeding developed in 33.3%, hematuria developed in 20% of cases, hematemesis developed in 26.7% of cases, intracranial hemorrhage developed in 23.3% of cases, and convulsions developed in 23.3% of cases.

CONCLUSIONS

In this study we have tried to evaluate the effect of sepsis on the physiologic inhibition system of coagulation in neonates. We should expect the effect of sepsis and its severity and perform the necessary laboratory investigations for coagulation including antithrombin III, protein C and protein S levels to help prevent thromboembolic accidents in neonates with sepsis, including disseminated intravascular coagulation, necrotizing enterocolitis and intracranial hemorrhage. Based on the findings of our study and the results of the other studies, we are in agreement that protein C is a very useful biomarker in severe sepsis, and it is a possible tool for monitoring treatment with activated protein C. We also encourage further placebo-controlled clinical trials to investigate the role of activated protein C and antithrombin III in severe neonatal sepsis and especially in the states before disseminated intravascular coagulation and the disseminated intravascular coagulation states, on the condition that they are guided by the experience and recommendations gained from the PROWESS, ENHANCE, and RESOLVE clinical trials. Protein C might be more effective if dosed according to protein C levels rather according to weight. Furthermore, we encourage future research on activated protein C mutants, which are anticipated to appear very soon because they can reduce some side effects associated with the use of recombinant human activated protein C, such as intracranial hemorrhage and bleeding tendencies, because they have reduced anticoagulant activity while retaining the cytoprotective effects.

Protein C: a potential biomarker in severe sepsis and a possible tool for monitoring treatment with drotrecogin alfa (activated)

Introduction

Drotrecogin alfa (activated; DrotAA) treatment, a 96-hour infusion, reduces 28-day mortality in severe sepsis to approximately 25%. The question remains whether a longer infusion or higher dose could increase rate of survival. The goal of this study was to identify a dependable, sensitive measure with which to monitor disease progression and response in patients during DrotAA treatment.

Methods

Data on severe sepsis patients included in PROWESS (placebo-controlled, double-blind, randomized study of 850 DrotAA and 840 placebo individuals) and ENHANCE (single-arm, open-label study of 2,375 DrotAA patients) studies were analyzed. In these studies, DrotAA (24 μg/kg per hour) or placebo was infused for 96 hours and patients were followed for 28 days. Data on six laboratory measures and five organ dysfunctions were systematically analyzed to identify a potential surrogate end-point for monitoring DrotAA therapy and predicting 28-day mortality at the end of therapy. To allow comparison across variables, sensitivity and specificity analyses identified cut-off values for preferred outcome, and relative risks for being above or below cut-offs were calculated, as was the 'proportion of treatment effect explained' (PTEE) to identify biomarkers that contribute to benefit from DrotAA.

Results

Protein C was the only variable that correlated with outcome across all analyses. Using placebo data, a baseline protein C under 40% was established as a useful predictor of outcome (odds ratio 2.12). Similar odds ratios were associated with cut-off values of other biomarkers, but the treatment benefit associated with DrotAA was significantly greater below the cut-off than above the cut-off only for protein C (relative risk for 28-day mortality 0.66 versus 0.88; P = 0.04). Protein C was the only end-of-infusion biomarker that potentially explained at least 50% of the benefit from DrotAA (PTEE 57.2%). The PTEE was 41% for cardiovascular Sequential Organ Failure Assessment score and for d-dimer. At the end of infusion (day 4), protein C categories (≤40%, 41% to 80%, and > 80%) remained significantly related to mortality, regardless of treatment assignment.

Conclusion

Based on systematic analyses of 11 variables measured in severe sepsis clinical trials, protein C was the only variable consistently correlated with both DrotAA treatment effect and survival. Further study is needed to determine whether longer infusions or higher doses of DrotAA would achieve the goal of normalizing protein C in more patients with severe sepsis.

The protein C pathway: implications for the design of the RESPOND study

The predictive value of plasma protein C level in sepsis has been demonstrated in a number of studies in which depressed protein C levels were associated with increased likelihood of negative outcome. Data from the PROWESS (Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis) trial indicate that administration of drotrecogin alfa (activated; DrotAA) leads to an increase in endogenous protein C levels in severe sepsis patients. In a group as heterogeneous as sepsis patients, the currently approved dose and duration of administration (24 mug/kg per hour for 96 hours) might not be optimal in some individuals. The RESPOND (Research Evaluating Serial Protein C levels in severe sepsis patients ON Drotrecogin alfa [activated]) trial is a phase II study being conducted to explore the use of endogenous protein C level as both a biomarker and a steering parameter for administration of DrotAA. Eligible patients will receive DrotAA either at the normal, currently approved dose and duration of administration ('standard therapy') or at a higher dose with variable infusion duration or variable infusion duration only ('alternative therapy'). The duration of DrotAA infusion in the alternative therapy arm depends on the individual response in terms of sustained increase in endogenous protein C. The ultimate aims of this and potential following studies are as follows: to establish serial plasma protein C measurement as a biomarker that will aid in the identification of severe sepsis patients who are most likely to benefit from DrotAA therapy, to enable adjustment of DrotAA therapy in individual patients (specifically, the possibility to use a higher dose and to adjust the infusion duration), and to provide guidance to the clinician regarding whether the patient is responding to DrotAA.

Protein C as an early marker of severe septic complications in diffuse secondary peritonitis

To evaluate the predictive value of protein C as a marker of severity in patients with diffuse peritonitis and abdominal sepsis, protein C levels were repeatedly determined and compared with serum levels of antithrombin III, plasminogen, alpha(2)-antiplasmin, Plasminogen activator inhibitor, D-dimer, C1-inhibitor, high molecular weight kininogen, and the C5a, C5b-9 fragments of the complement system. We carried out a prospective study from 44 patients with severe peritonitis confirmed by laparotomy and 15 patients undergoing elective ventral hernia repair who acted as controls. Analyzed biochemical parameters were determined before operations and on days 1, 2, 3, 5, 7, 10, and 14 after operations. For the study group, preoperative average protein C level was significantly lower in the patients who developed septic shock in the late course of the disease, with lethal outcome, than in the patients with severe peritonitis and sepsis who survived (p = 0.0001). In non-survivors, protein C activity remained decreased below 70%, whereas the course of survivors was characterized by increased values that were significantly higher (p < 0.03) at every time point than in those patients who died. Protein C was of excellent predictive value and achieved a sensitivity of 80% and a specificity of 87.5% in discriminating survivors from non-survivors within the first 48 hours of the study (AUC-0.917; p < 0.001), with a "cut-off" level of 66.0%. As for the control group, throughout the study period, protein C activity was permanently maintained within the range of normal, with significant differences with reference to the study group (p < 0.01). These results suggest that protein C represents a sensitive and early marker for the prediction of severe septic complications during diffuse peritonitis, and of outcome.

Linking the sepsis triad of inflammation, coagulation, and suppressed fibrinolysis to infants

Sepsis continues to be a significant cause of morbidity and mortality in hospitalized newborns and premature infants. The pathophysiology and disease state of sepsis appear to be similar between adults and children. Both groups display symptoms that indicate a systemic inflammatory response leading to coagulopathy, hypotension, inadequate perfusion of peripheral tissues and organs, and, ultimately, organ failure and death. By presenting a comparison of adult and neonatal pathophysiology, as well as a supporting literature review and clinical evidence, this article links the pathways of inflammation, activation of coagulation, and impaired fibrinolysis, known as the sepsis cascade, to neonatal sepsis. Knowledge of the pathophysiology has important clinical and research implications. Unlike traditional antimicrobial therapy, new potential therapies, currently under investigation for the treatment of sepsis, target the cellular response rather than the invading organism. A more complete understanding of the pathophysiology of sepsis may also lead to diagnostic tools with improved sensitivity and specificity for early recognition and treatment.

Evaluation of protein C and other biomarkers as predictors of mortality in a rat cecal ligation and puncture model of sepsis

OBJECTIVE

To evaluate protein C and other factors associated with the septic response as predictors of mortality in a clinically relevant animal model of sepsis.

DESIGN

Laboratory investigation.

SETTING

Eli Lilly and Company discovery research laboratory.

SUBJECTS

Forty female Sprague Dawley rats weighing 245-265 g.

INTERVENTIONS

Polyethylene catheters were surgically implanted into the femoral vein and sepsis was induced by cecal ligation and puncture (CLP). A solution of 5% dextrose in 0.9 % saline was continuously infused via femoral catheters immediately following surgery. Blood sampling was done before surgery and at 6 and 20 hrs after surgery. Rats were then monitored for survival out to 4 days.

MEASUREMENTS AND MAIN RESULTS

Blood collections were used to measure blood glucose, bacteremia, plasma protein C, D-dimer, hormones, chemokines, cytokines, and myoglobin (as a marker of organ damage). Mortality was categorized into three groups: early death (before 30 hrs post-CLP), late death (after 30 hrs post-CLP), and survivors (96 hrs post-CLP). Compared with survivors, early death rats had statistically significant differences in 30 variables indicative of severe inflammation, coagulopathy, and muscle damage including less bacterial clearance, hypoglycemia, lower plasma protein C, higher plasma D dimer, higher plasma cytokine/ chemokines, and higher plasma myoglobin concentrations. Twenty variables had a moderate to strong correlation with time of death. Receiver operator characteristic curves generated from a simple logistic regression model indicated that KC and macrophage inflammatory protein-2, rodent homologues of the human growth related oncogene CXC chemokine family, and protein C were the best predictors of mortality in this model.

CONCLUSIONS

The data from this study indicate that an early decrease in protein C concentration predicts poor outcome in a rat sepsis model. The data further indicate that increases in the CXC chemokines macrophage inflammatory protein-2 and KC precede poor outcome.

The epidemiology of severe sepsis syndrome and its treatment with recombinant human activated protein C

Severe sepsis syndrome has important consequences to healthcare systems as the incidence is increasing, there is significant attributed morbidity and mortality and there is a substantial cost for in-hospital and post-discharge care. Current treatment includes the use of antimicrobials, local source control and aggressive physiological support, usually in an intensive care unit setting. Drotrecogin-alpha (activated) or recombinant human activated protein C (rhAPC) is the only biological agent approved for use in severe sepsis syndrome that has demonstrated efficacy in reducing 28-day all-cause mortality and new data suggests a trend towards longer term survival. However, given the evidence of a variable effect on survival rates in patient subgroups and its acquisition cost, controversy has arisen concerning its appropriate use. This review discusses the epidemiology of sepsis, preclinical and clinical evidence supporting the use of rhAPC use, controversies about the evidence of efficacy in severe sepsis syndrome and cost-effectiveness data.

Acute myocardial infarction in the neonatal period

We describe two neonates presenting with myocardial infarction, due to two different aetiologies of this extremely rare but potentially treatable condition, and discuss the management. One neonate had myocardial infarction complicating enteroviral myocarditis and recovered completely. The second had fatal myocardial infarction due to thrombosis of the left coronary artery. Although rare, the attending paediatrician should have a high index of suspicion when evaluating a neonate with acute onset of collapse. Electrocardiographic changes are diagnostic, but further echocardiographic assessment and prompt management at a tertiary cardiac centre are advised.

Recombinant human activated protein C: a system modulator of vascular function for treatment of severe sepsis

OBJECTIVE

To review the mechanisms of action and rationale for the use of recombinant human activated protein C in the treatment of severe sepsis. Specifically, we focus on the mechanisms of action in the protein C pathway that converge to modulate the pathophysiology of severe inflammatory disease and sepsis. This analysis includes a discussion of the role of activated protein C in directly modulating cell system biology, independent of antithrombotic activity.

DATA SOURCES/STUDY SELECTION

Published research and review articles relating to the protein C pathway, recombinant human protein C, and the role of protein C in sepsis. Data were also derived from broad gene profiling in model systems of endothelial dysfunction.

DATA EXTRACTION AND SYNTHESIS

Relevant studies were included to support discussion of the unique mechanistic aspect of protein C and its role in the pathogenesis of severe sepsis. We discuss the potential of activated protein C as a unique system modulator for the treatment of severe sepsis and other systemic inflammatory responses that result in microvascular coagulopathy, endothelial dysfunction, and vascular bed failure.

CONCLUSIONS

The protein C pathway plays a unique role in modulating vascular function. As an antithrombotic/profibrinolytic agent, it plays a clear role in maintaining vascular patency. Moreover, it has anti-inflammatory properties and appears to play a unique role as an antiapoptotic and endothelial cell survival factor. In states of systemic inflammatory activation, loss of protein C due to consumptive processes results in a compromised ability to modulate coagulation as well as inflammatory and cell survival functions. This compromise leads to vascular dysfunction, end-organ failure, and death. Replacement with recombinant human activated protein C offers a system-modulating approach to improved outcome.

Protein C levels as a prognostic indicator of outcome in sepsis and related diseases

OBJECTIVE

To consider the appropriateness of protein C levels as a prognostic indicator for sepsis and related diseases.

DATA SOURCES/STUDY SELECTION

Published research and review articles related to protein C deficiency in patients with sepsis and related diseases.

DATA EXTRACTION AND SYNTHESIS

All applicable data were extracted, and relevant literature was cited to support factual statements in the text. The protein C pathway represents one of the major regulatory systems of hemostasis, exhibiting antithrombotic, profibrinolytic, and anti-inflammatory properties. Numerous studies have shown that acquired protein C deficiency is prevalent in the majority of septic patients (>85%) and is associated with increased morbidity and mortality in patients with severe sepsis and septic shock. This deficiency in protein C is not simply a transient marker for sepsis, but parallels the progress of the disease. In addition, protein C deficiency occurs in the presence of a wide range of pathogens and develops early in the disease process.

CONCLUSIONS

A review of the relevant literature suggests that protein C levels may serve as a useful prognostic indicator of outcome in sepsis and related diseases.

Prognostic value of protein C concentrations in neutropenic patients at high risk of severe septic complications

OBJECTIVE

To assess the prognostic value of protein C, endogenous activated protein C, and D-dimer concentrations in patients at high risk of developing severe septic complications secondary to cytostatic chemotherapy.

DESIGN

Prospective, comparative, single-center study.

SETTING

Specialized ward for treating patients with acute leukemia and associated intensive care unit at a university hospital.

SUBJECTS

Twenty-six consecutive patients who developed either severe sepsis (n = 13) or septic shock (n = 13) during chemotherapy-induced neutropenia (leukocytes <1,000/microL).

INTERVENTION

None, other than standard care.

MEASUREMENTS AND MAIN RESULTS

Baseline blood samples were obtained from 97 adult patients treated with intensive cytostatic chemotherapy. Serial blood sampling was performed in 62 of 97 patients who developed fever (>38.3 degrees C). Thirteen patients progressed to severe sepsis and 13 patients to septic shock. Protein C, endogenous activated protein C, and D-dimer were measured in these 26 patients. At fever onset, protein C concentrations decreased from normal baseline concentrations and were significantly lower in the group of patients who progressed to septic shock compared with those who developed severe sepsis (medians for protein C activity: 23.1% vs. 69.5%; p = .0003). The median elapsed time between detection of fever and the diagnosis of severe sepsis or septic shock was 16 hrs and 12 hrs, respectively. All septic shock patients died, whereas patients who progressed only to severe sepsis survived.

CONCLUSIONS

Septic shock in neutropenic patients is associated with increased protein C consumption. The data demonstrate that the coagulation cascade is activated and produces a hypercoagulable state before the onset of clinical symptoms of severe sepsis and septic shock. Low protein C concentrations at the onset of fever and before the onset of clinical symptoms of severe sepsis or septic shock may have prognostic value in predicting an unfavorable outcome. Protein C measurements may help identify patients at risk in an early phase of neutropenic sepsis. It is also attractive to speculate that because low protein C concentrations were seen in these patients, protein C replacement may be beneficial in sepsis.

Septic shock

Although our understanding of molecular events in septic shock is growing exponentially, bedside management has changed only incrementally over the last 20 years. In pediatric and adult patients alike, treatment continues to be largely supportive. Morbidity and mortality, though gradually improving, continue to be high. The major similarities, as well as the minor differences, between pediatric and adult septic shock are reviewed in this article, with an emphasis on current clinical practice and recent clinical investigations of novel therapies.