Understanding the role of von Willebrand factor and its cleaving protease ADAM TS13 in the pathophysiology of critical illness

Thrombocytopenia-associated multiple-organ failure (TAMOF): recognition and management

Thrombocytopenia-associated multiple-organ failure (TAMOF) is an increasingly fatal phenomenon that may be associated with sepsis. TAMOF results from immune dysregulation and impaired activity of A Disintegrin And Metalloproteinase with ThromboSpondin type 1 motif, member 13. Early recognition of this premorbid condition and specific management results in a significantly improved outcome. Herein, we report the presentation and management of a 2-year-old child with TAMOF who was successfully treated with plasma exchange and recovered without long-term sequelae.

Pediatric Sepsis Update: How Are Children Different?

BACKGROUND

Although there are some commonalities between pediatric and adult sepsis, there are important differences in pathophysiology, clinical presentation, and therapeutic approaches. The recognition and diagnosis of sepsis is a significant challenge in pediatric patients as vital sign aberrations and examination findings are often subtle as compared to those observed in adults. Gaps in knowledge that have been studied in depth in adult sepsis are still being investigated in pediatric patients such as best practices in ventilation, invasive monitoring, and resuscitation.

DISCUSSION

In this review, we address key differences in the etiology, presentation, resuscitation, and outcomes of sepsis in children compared with adults.

Pediatric Sepsis Biomarker Risk Model-II: Redefining the Pediatric Sepsis Biomarker Risk Model With Septic Shock Phenotype

OBJECTIVE

The Pediatric Sepsis Biomarker Risk Model (PERSEVERE), a pediatric sepsis risk model, uses biomarkers to estimate baseline mortality risk for pediatric septic shock. It is unknown how PERSEVERE performs within distinct septic shock phenotypes. We tested PERSEVERE in children with septic shock and thrombocytopenia-associated multiple organ failure (TAMOF), and in those without new onset thrombocytopenia but with multiple organ failure (MOF).

DESIGN

PERSEVERE-based mortality risk was generated for each study subject (n = 660). A priori, we determined that if PERSEVERE did not perform well in both the TAMOF and the MOF cohorts, we would revise PERSEVERE to incorporate admission platelet counts.

SETTING

Multiple PICUs in the United States.

INTERVENTIONS

Standard care.

MEASUREMENTS AND MAIN RESULTS

PERSEVERE performed well in the TAMOF cohort (areas under the receiver operating characteristic curves [AUC], 0.84 [95% CI, 0.77-0.90]), but less well in the MOF cohort (AUC, 0.71 [0.61-0.80]). PERSEVERE was revised using 424 subjects previously reported in the derivation phase. PERSEVERE-II had an AUC of 0.89 (0.85-0.93) and performed equally well across TAMOF and MOF cohorts. PERSEVERE-II performed well when tested in 236 newly enrolled subjects. Sample size calculations for a clinical trial testing the efficacy of plasma exchange for children with septic shock and TAMOF indicated PERSEVERE-II-based stratification could substantially reduce the number of patients necessary, when compared with no stratification.

CONCLUSIONS

Testing PERSEVERE in the context of septic shock phenotypes prompted a revision incorporating platelet count. PERSEVERE-II performs well upon testing, independent of TAMOF or MOF status. PERSEVERE-II could potentially serve as a prognostic enrichment tool.

Pathophysiology of Pediatric Multiple Organ Dysfunction Syndrome

OBJECTIVE

To describe the pathophysiology associated with multiple organ dysfunction syndrome in children.

DATA SOURCES

Literature review, research data, and expert opinion.

STUDY SELECTION

Not applicable.

DATA EXTRACTION

Moderated by an experienced expert from the field, pathophysiologic processes associated with multiple organ dysfunction syndrome in children were described, discussed, and debated with a focus on identifying knowledge gaps and research priorities.

DATA SYNTHESIS

Summary of presentations and discussion supported and supplemented by relevant literature.

CONCLUSIONS

Experiment modeling suggests that persistent macrophage activation may be a pathophysiologic basis for multiple organ dysfunction syndrome. Children with multiple organ dysfunction syndrome have 1) reduced cytochrome P450 metabolism inversely proportional to inflammation; 2) increased circulating damage-associated molecular pattern molecules from injured tissues; 3) increased circulating pathogen-associated molecular pattern molecules from infection or endogenous microbiome; and 4) cytokine-driven epithelial, endothelial, mitochondrial, and immune cell dysfunction. Cytochrome P450s metabolize endogenous compounds and xenobiotics, many of which ameliorate inflammation, whereas damage-associated molecular pattern molecules and pathogen-associated molecular pattern molecules alone and together amplify the cytokine production leading to the inflammatory multiple organ dysfunction syndrome response. Genetic and environmental factors can impede inflammation resolution in children with a spectrum of multiple organ dysfunction syndrome pathobiology phenotypes. Thrombocytopenia-associated multiple organ dysfunction syndrome patients have extensive endothelial activation and thrombotic microangiopathy with associated oligogenic deficiencies in inhibitory complement and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13. Sequential multiple organ dysfunction syndrome patients have soluble Fas ligand-Fas-mediated hepatic failure with associated oligogenic deficiencies in perforin and granzyme signaling. Immunoparalysis-associated multiple organ dysfunction syndrome patients have impaired ability to resolve infection and have associated environmental causes of lymphocyte apoptosis. These inflammation phenotypes can lead to macrophage activation syndrome. Resolution of multiple organ dysfunction syndrome requires elimination of the source of inflammation. Full recovery of organ functions is noted 6-18 weeks later when epithelial, endothelial, mitochondrial, and immune cell regeneration and reprogramming is completed.

Therapeutic plasma exchange may improve hemodynamics and organ failure among children with sepsis-induced multiple organ dysfunction syndrome receiving extracorporeal life support

OBJECTIVE

To determine the effect of therapeutic plasma exchange on hemodynamics, organ failure, and survival in children with multiple organ dysfunction syndrome due to sepsis requiring extracorporeal life support.

DESIGN

A retrospective analysis.

SETTING

A PICU in an academic children's hospital.

PATIENTS

Fourteen consecutive children with sepsis and multiple organ dysfunction syndrome who received therapeutic plasma exchange while on extracorporeal life support from 2005 to 2013.

INTERVENTIONS

Median of three cycles of therapeutic plasma exchange with median of 1.0 times the estimated plasma volume per exchange.

MEASUREMENTS AND MAIN RESULTS

Organ Failure Index and Vasoactive-Inotropic Score were measured before and after therapeutic plasma exchange use. PICU survival in our cohort was 71.4%. Organ Failure Index decreased in patients following therapeutic plasma exchange (mean ± SD: pre, 4.1 ± 0.7 vs post, 2.9 ± 0.9; p = 0.0004). Patients showed improved Vasoactive-Inotropic Score following therapeutic plasma exchange (median [25th-75th]: pre, 24.5 [13.0-69.8] vs post, 5.0 [1.5-7.0]; p = 0.0002). Among all patients, the change in Organ Failure Index was greater for early therapeutic plasma exchange use than late use (early, -1.7 ± 1.2 vs late, -0.9 ± 0.6; p = 0.14), similar to the change in Vasoactive-Inotropic Score (early, -67.5 [28.0-171.2] vs late, -12.0 [7.2-18.5]; p = 0.02). Among survivors, the change in Organ Failure Index was greater among early therapeutic plasma exchange use than late use (early, -2.3 ± 1.0 vs late, -0.8 ± 0.8; p = 0.03), as was the change in Vasoactive-Inotropic Score (early, -42.0 [16.0-76.3] vs late, -12.0 [5.3-29.0]; p = 0.17). The mean duration of extracorporeal life support after therapeutic plasma exchange according to timing of therapeutic plasma exchange was not statistically different among all patients or among survivors.

CONCLUSIONS

The use of therapeutic plasma exchange in children on extracorporeal life support with sepsis-induced multiple organ dysfunction syndrome is associated with organ failure recovery and improved hemodynamic status. Initiating therapeutic plasma exchange early in the hospital course was associated with greater improvement in organ dysfunction and decreased requirement for vasoactive and/or inotropic agents.

Clinical measurement of von Willebrand factor by fluorescence correlation spectroscopy

BACKGROUND

Identification of von Willebrand factor (vWF) abnormalities in a variety of conditions is hampered by the limitations of currently available diagnostic tests. Although direct multimer visualization by immunoelectrophoresis is a commonly used method, it is impractical as a routine clinical test. In this study, we used a biophysical analysis tool, fluorescence correlation spectroscopy (FCS), to measure vWF distributions. The goals were to develop a method that is quicker and simpler than vWF gel electrophoresis and to evaluate the potential of FCS as a clinical diagnostic technique.

METHODS

We analyzed plasma from 12 patients with type 1 von Willebrand disease (vWD), 14 patients with type 2 vWD, and 10 healthy controls using a fluctuation-based immunoassay approach.

RESULTS

FCS enabled identification and proper classification of type 1 and type 2 vWD, producing quantitative results that correspond to qualitative gel multimer patterns. FCS required minimal sample preparation and only a 5-min analysis time.

CONCLUSIONS

This study represents the first implementation of FCS for clinical diagnostics directly on human plasma. The technique shows potential for further vWF studies and as a generally applicable laboratory test method.