Bench-to-bedside review: thrombocytopenia-associated multiple organ failure--a newly appreciated syndrome in the critically ill

Endothelial cell dysfunction in viral hemorrhage and edema

The endothelium maintains a vascular barrier by controlling platelet and immune cell interactions, capillary tone and interendothelial cell (EC) adherence. Here we suggest common elements in play during viral infection of the endothelium that alter normal EC functions and contribute to lethal hemorrhagic or edematous diseases. In viral reservoir hosts, infection of capillaries and lymphatic vessels may direct immunotolerance without disease, but in the absence of these cognate interactions they direct the delayed onset of human disease characterized by thrombocytopenia and vascular leakage in a severe endothelial dysfunction syndrome. Here we present insight into EC controls of hemostasis, immune response and capillary permeability that are altered by viral infection of the endothelium.

Biology of sepsis: its relevance to pediatric nephrology

Because of its multi-organ involvement, the syndrome of sepsis provides clinical challenges to a wide variety of health care providers. While multi-organ dysfunction triggered by sepsis requires general supportive critical care provided by intensivists, the impact of sepsis on renal function and the ability of renal replacement therapies to modulate its biologic consequences provide a significant opportunity for pediatric nephrologists and related care providers to impact outcomes. In this review, we aim to highlight newer areas of understanding of the pathobiology of sepsis with special emphasis on those aspects of particular interest to pediatric nephrology. As such, we aim to: (1) review the definition of sepsis and discuss advances in our mechanistic understanding of sepsis; (2) review current hypotheses regarding sepsis-induced acute kidney injury (AKI) and describe its epidemiology based on evolving definitions of AKI; (3) review the impact of renal failure on the immune system, highlighting the sepsis risk in this cohort and strategies that might minimize this risk; (4) review how renal replacement therapeutic strategies may impact sepsis-induced AKI outcomes. By focusing the review on these specific areas, we have omitted other important areas of the biology of sepsis and additional interactions with renal function from this discussion; however, we have aimed to provide a comprehensive list of references that provide contemporary reviews of these additional areas.

Use of therapeutic plasma exchange in children with thrombocytopenia-associated multiple organ failure in the Turkish thrombocytopenia-associated multiple organ failure network

OBJECTIVE

Thrombocytopenia-associated multiple organ failure can lead to high mortality in critically ill children, possibly related to consequences of thrombotic microangiopathy. Plasma exchange therapy may improve thrombotic microangiopathy. The purpose of this observational cohort study is to describe whether there is an association between use of plasma exchange therapy and outcome in the Turkish thrombocytopenia-associated multiple organ failure network.

SETTING-INTERVENTIONS

We performed a retrospective cohort analysis in patients with thrombocytopenia-associated multiple organ failure at three different PICUs comparing those who received plasma exchange (+) plus standard therapies with those who did not receive plasma exchange (-) and only received standard therapies.

RESULTS

Among 42 of the enrolled patients with thrombocytopenia-associated multiple organ failure, all had a primary or secondary sepsis diagnosis. Fifteen received plasma exchange therapy (PE [+] group) and 27 received standard medical treatment without plasma exchange (PE [-] group). The mean age was 17.69 months (8.24-54.22) in the PE (+) group and 13.46 months (6.47-20.55) in the PE (-) group. Age (p = 0.232), gender (p = 0.206), thrombocyte count (p = 0.09), Organ Failure Index score (p = 0.111), and pediatric logistic organ dysfunction score (p = 0.177) at admission were not statistically different between groups. The overall 28-day mortality was higher in the PE (-) group (70.37%) compared with the PE (+) group (26.67%) (univariate p = 0.006; multivariate controlling for pediatric logistic organ dysfunction, Organ Failure Index, Pediatric Risk of Mortality scores, and neurological failure p = 0.048). Length of stay was increased in the PE (+) group (p = 0.004).

CONCLUSIONS

The positive association found between use of plasma exchange therapy and improved survival supports the potential of this therapy in Turkish children with thrombocytopenia-associated multiple organ failure. The positive, although less so, associated treatment effect observed after controlling for illness severity provides further rationale for performing a randomized controlled trial in the pediatric Turkish thrombocytopenia-associated multiple organ failure network. Sample size calculations call for a 100-patient trial with a pre hoc interim analysis after enrollment of 50 patients with thrombocytopenia-associated multiple organ failure.

Active exercise in critically ill adults affected by thrombocytopaenia

Introduction

Thrombocytopaenia (TCP), or low platelet count, is a haematological disorder that commonly occurs in critically ill patients and is defined as a platelet count below 100 000/μL. Patients are at higher risk of muscular atrophy and other complications after prolonged bed rest. This literature review aims to clarify the appropriateness of active exercise in critically ill adult patients with TCP.

Methods

A review of the literature was conducted using the following key words that are PubMed medical subheading (MeSH) terms: ‘critical illness’, ‘exercise therapy’, ‘manual therapy’, ‘physical therapy’, ‘physiotherapy’, ‘postoperative care’, ‘rehabilitation’, ‘thrombocytopenia’, and ‘thrombopenia’. The search was limited by publication date (2000 to 2013) and language (English only) in three main databases: PubMed, SCOPUS, and CINAHL.

Results

The key word searches found a total of 78 citations. Of these, only those meeting the inclusion criteria were selected after reading the title and abstract. Two studies were included after reading the full-texts. Exercise is used to treat muscular atrophy in critically ill adult patients, and rehabilitation plays an important role in the care pathway. Results of our analysis do not support evidence for or against exercise in critically ill adult patients with TCP; therefore, health professionals must pay close attention to the presence of signs of bleeding in these patients when proposing exercise.

Discussion

Surprisingly, no study was found that directly covered this issue. Aggressive exercise may not be appropriate in patients with very low platelet counts. On the other hand, critically ill patients are at high risk of muscular atrophy due to the forced bed rest, especially after complex surgery or in prolonged hospitalisation. Physiotherapists and those providing care must share their observations with the rest of the multidisciplinary team before treatment starts.

Conclusions

Active exercise in critically ill adult patients with severe TCP must be personalised and platelet count carefully monitored before proposing physical activity. Physical recovery can be challenging in critically ill adult patients, and it can be limited by severe TCP, mostly when bleeding is present.

Thrombocytopenia-associated multiple organ failure or severe haemolysis, elevated liver enzymes, low platelet count in a postpartum case

Thrombocytopenia-associated multiple organ failure (TAMOF) is a thrombotic microangiopathic syndrome that includes thrombotic thrombocytopenic purpura, secondary thrombotic microangiopathy, and disseminated intravascular coagulation. We report a case of postpartum female who presented with TAMOF or severe Haemolysis, elevated liver enzymes, low platelet count (HELLP) which was managed with plasma exchange. This case report is to make clinicians aware that TAMOF, severe HELLP, and other differential diagnosis in a postpartum case have a thin differentiating line and plasma exchange can be considered as one of the management options.

Is hyperoxaemia helping or hurting patients during extracorporeal membrane oxygenation? Review of a complex problem

Extracorporeal membrane oxygenation (ECMO) facilitates organ support in patients with refractory cardiorespiratory failure whilst disease-modifying treatments can be administered. Improvements to the ECMO process have resulted in its increased utilisation. However, iatrogenic injuries remain, with bleeding and thrombosis the most significant concerns. Many factors contribute to the formation of thrombi, with the hyperoxaemia experienced during ECMO a potential contributor. Outside of ECMO, emerging evidence associates hyperoxaemia with increased mortality. Currently, no universal definition of hyperoxaemia exists, a gap in clinical standards that may impact patient outcomes. Hyperoxaemia has the potential to induce platelet activation, aggregation and, subsequently, thrombosis through markedly increasing the production of reactive oxygen species. There are minimal data in the current literature that explore the relationship between ECMO-induced hyperoxaemia and the production of reactive oxygen species – a putative link towards pathology. Furthermore, there is limited research directly linking hyperoxaemia and platelet activation. These are areas that warrant investigation as definitive data regarding the nascence of these pathological processes may delineate and define the relative risk of supranormal oxygen tension. These data could then assist in defining optimal oxygenation practice, reducing the risks associated with extracorporeal support.

Severe dengue is associated with consumption of von Willebrand factor and its cleaving enzyme ADAMTS-13

Background

Thrombocytopenia, bleeding and plasma leakage are cardinal features of severe dengue. Endothelial cell activation with exocytosis of Weibel-Palade bodies (WPBs) may play an etiological role in this condition.

Methods and Principal Findings

In a cohort of 73 Indonesian children with dengue hemorrhagic fever (DHF), of which 30 with dengue shock syndrome (DSS), we measured plasma levels of the WPB constituents von Willebrand factor antigen (VWF:Ag), VWF propeptide and osteoprotegerin (OPG), together with activity levels of the VWF-cleaving enzyme ADAMTS-13 and the amount of VWF in a platelet binding conformation (VWF activation factor). Compared with healthy controls (n = 17), children with DHF/DSS had significantly higher levels of VWF:Ag, VWF propeptide and OPG and decreased ADAMTS-13 activity. The VWF activation factor was also significantly higher in DHF/DSS and highest in children who died. There were significant differences in the kinetics of the various WPB constituents: VWF propeptide and OPG levels decreased toward discharge, while VWF:Ag levels were lower than expected at enrollment with plasma levels increasing toward discharge. Moreover, VWF propeptide levels correlated better with markers of disease severity (platelet count, liver enzymes, serum albumin and pleural effusion index) than corresponding VWF levels. Together, these findings suggest that there is consumption of VWF in DHF/DSS. In 4 out of 15 selected children with low ADAMTS-13 levels on admission, we found a remarkable reduction in the large and intermediate VWF multimers in the discharge blood samples, consistent with an acquired von Willebrand disease.

Conclusion

These findings suggest that severe dengue is associated with exocytosis of WPBs with increased circulating levels of VWF:Ag, VWF propeptide and OPG. High circulating levels of VWF in its active conformation, together with low ADAMTS-13 activity levels, are likely to contribute to the thrombocytopenia and complications of dengue. During the convalescence phase, qualitative defects in VWF with loss of larger VWF multimers may develop.

Severe dengue infections are characterized by thrombocytopenia, clinical bleeding and plasma leakage. Activation of the endothelium, the inner lining of blood vessels, leads to the secretion of storage granules called Weibel Palade bodies (WPBs). We demonstrated that severe dengue in Indonesian children is associated with a strong increase in plasma levels of the WPB constituents von Willebrand factor (VWF), VWF propeptide and osteoprotegerin (OPG). An increased amount of the hemostatic protein VWF was in a hyperreactive, platelet binding conformation, and this was most pronounced in the children who died. VWF levels at enrollment were lower than expected from concurrent VWF propeptide and OPG levels and VWF levels did not correlate well with markers of disease severity. Together, this suggests that VWF is being consumed during severe dengue. Circulating levels of the VWF-cleaving enzyme ADAMTS-13 were reduced. VWF is a multimeric protein and a subset of children had a decrease in large and intermediate VWF multimers at discharge. In conclusion, severe dengue is associated with exocytosis of WPBs with consumption of VWF and low ADAMTS-13 activity levels. This may contribute to the thrombocytopenia and complications of dengue.

Rapid identification of thrombocytopenia-associated multiple organ failure using red blood cell parameters and a volume/hemoglobin concentration cytogram

Thrombocytopenia-associated multiple organ failure (TAMOF) has a high mortality rate when not treated, and early detection of TAMOF is very important diagnostically and therapeutically. We describe herein our experience of early detection of TAMOF, using an automated hematology analyzer. From 498,390 inpatients, we selected 12 patients suspected of having peripheral schistocytosis, based on the results of red blood cell (RBC) parameters and a volume/hemoglobin concentration (V/HC) cytogram. We promptly evaluated whether the individual patients had clinical manifestations and laboratory findings were consistent with TAMOF. Plasma exchanges were then performed for each patient. All 12 patients had TAMOF. The mean values of RBC parameters were significantly higher in all of the patients than with the reference range, however, 3 patients had % RBC fragments within the reference range. The mean value of ADAMTS-13 activity was slightly lower in patients compared with the reference range. Of the 12 patients, remission was obtained in 9 patients (75%) within 4 to 5 weeks using plasma exchanges. Three patients died. An increased percentage of microcytic hyperchromic cells with anisocytosis and anisochromia indicated the presence of schistocytes, making it an excellent screening marker for TAMOF. Identification of TAMOF with RBC parameters and a V/HC cytogram is a facile and rapid method along with an automated hematology analyzer already in use for routine complete blood cell counting test.

Rethinking platelet function: thrombocytopenia induced immunodeficiency in critical illness

Thrombocytopenia in critical illness predicts a poor clinical outcome. Apart from its role in microvascular thrombus formation, it is widely anticipated that this association is indirect rather than causal. Emerging evidence however indicates that platelets are also immune competent cells. Like traditional innate immune cells, platelets are recruited immediately into injured and inflamed tissue, they release immune mediators, express and shed immunologically active membrane receptors, they interact with other immune cells and they recognize and clear pathogens. We hypothesize that thrombocytopenia per se results in immunodeficiency through loss of platelet-mediated immune functions, and propose that thrombocytopenia induced immunodeficiency in critical illness in part explain the negative predictive value of low or declining platelet count. We propose that rethinking the risks of thrombocytopenia to include not only bleeding but also immunodeficiency and immune dysregulation along with the conduct of studies investigating mechanisms contributing to thrombocytopenia induced poor non-hemorrhagic outcome in critical illness, may be means to improve outcome in these patients through development of new treatment modalities.

A Difficult Diagnosis Case of Prolonged Thrombocytopenia With Sepsis and Disseminated Intravascular Coagulation

A 19-year-old male was admitted because of the trauma due to sepsis-induced disseminated intravascular coagulation (DIC) and multiple organ failure (MOF). We treated with antibiotics, danaparoid, and continuous hemodiafiltration (CHDF). Once he recovered, but after several days, he had septic shock and MOF again. With treatment, the inflammation and MOF improved but the platelet count was less than 1.0 × 10 4/μL. Because of the usage of heparin, we suspected heparin-induced thrombocytopenia (HIT) and measured the HIT antibody and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). Heparin-induced thrombocytopenia antibody was positive in the second sepsis but negative in the first sepsis. ADAMTS13 activity was low in both sepses. After stopping CHDF and the usage of heparin, his platelet count improved. Thrombocytopenia is the common and occasional condition for DIC. Heparin-induced thrombocytopenia and thrombotic thrombocytopenic purpura is rare but they must be ruled out in thrombocytopenia with nontypical clinical course, and the assays for HIT antibody and ADAMTS13 activity are useful tools.

Organ failure in sepsis

The development of organ failure determines the course and prognosis of the septic patient. Although several successful clinical trials in recent years have raised the enthusiasm of intensivists, severe sepsis and septic shock still have an increasing incidence with more or less unchanged mortality. Recent sepsis research, including progress made in definitions, epidemiology, pathophysiology, diagnosis, standard and adjunctive therapy, and experimental approaches, is encouraging. This includes genomic information for stratifying subgroups of patients, a broader field of laboratory diagnostics due to clinical studies, and basic research on the cellular mechanisms of inflammation and organ dysfunction. Furthermore, new findings in pathogenesis and therapeutic approaches to organ failure merit attention. In this review, state-of-the-art publications are presented to elucidate the possible impact of sepsis-induced organ failure on clinical routine.

ADAMTS-13 assays in thrombotic thrombocytopenic purpura

ADAMTS-13, the thirteenth member of the ADAMTS (A Disintegrin And Metalloprotease with Thrombo-Spondin 1 repeats) family, is the plasma metalloprotease responsible for regulating the multimeric structure of VWF. In congenital or acquired deficiency it is actively involved in the pathophysiology of thrombotic thrombocytopenic purpura (TTP), a rare but life threatening disease characterized by microangiopathic haemolytic anaemia and consumptive thrombocytopenia leading to disseminated microvascular thrombosis and variable signs and symptoms of organ ischemia and damage. In the last few years, a number of in house and commercial laboratory assays for ADAMTS-13 and its autoantibodies have been developed. The features and clinical utility of ADAMTS-13 assays are summarized in this review.

Genetic polymorphisms in the endotoxin receptor may influence platelet count as part of the acute phase response in critically ill children

PURPOSE

To determine if common polymorphisms in the endotoxin recognition complex influence the acute phase response as determined by the development of the systemic inflammatory response syndrome (SIRS) and platelet count on admission.

METHODS

This was a prospective observational cohort study. Paediatric intensive care patients (n = 913) were genotyped for common functional polymorphisms in the endotoxin recognition complex, including Toll-like receptor 4 (TLR4). We also selected potentially confounding polymorphisms in other genes of the innate immune system. SIRS was defined by age-specific consensus criteria. Platelet counts were recorded on admission.

RESULTS

The development of SIRS was primarily determined by the nature of the insult, but carriers of TLR4 variant alleles had lower platelet counts than children with wild-type genotype [mean +/- standard error of the mean (SEM) 143 +/- 7 vs. 175 +/- 4; p = 0.0001)--independent of other innate immune system polymorphisms. These findings were validated using a patient cohort of 1,170 adults with coronary artery disease. Carriers of TLR4 polymorphisms with a history of myocardial infarction (n = 573) had lower platelet counts than those with the wild-type genotype (217 +/- 7 vs. 237 +/- 2.8; p = 0.021).

CONCLUSIONS

Our results show that TLR4 variant alleles are associated with lower platelet counts across a range of ages and precipitating insults but that they do not influence the incidence of SIRS. This result may reflect redundancy and 'robustness' in the pathways leading to SIRS or the lack of specificity of this endpoint. Platelet count may vary with TLR4 genotype because it may be sufficiently sensitive and more linearly related to inflammation than other markers or, alternatively, there may be a direct TLR4-mediated platelet effect.

Sepsis-induced disseminated intravascular coagulation with features of thrombotic thrombocytopenic purpura: a fatal fulminant syndrome

Disseminated intravascular coagulation (DIC) and thrombotic thrombocytopenic purpura (TTP) are different disease states, while ADAMTS13 deficiency could occur in sepsis-induced DIC. We report 2 patients who had septic DIC with features of idiopathic TTP characterized by low ADAMTS13 activity and positive ADAMTS13 inhibitor. They had a specific fulminant course and fatal outcome, which might represent a new specific syndrome.

Blood coagulation, inflammation, and malaria

Malaria remains a highly prevalent disease in more than 90 countries and accounts for at least 1 million deaths every year. Plasmodium falciparum infection is often associated with a procoagulant tonus characterized by thrombocytopenia and activation of the coagulation cascade and fibrinolytic system; however, bleeding and hemorrhage are uncommon events, suggesting that a compensated state of blood coagulation activation occurs in malaria. This article (i) reviews the literature related to blood coagulation and malaria in a historic perspective, (ii) describes basic mechanisms of coagulation, anticoagulation, and fibrinolysis, (iii) explains the laboratory changes in acute and compensated disseminated intravascular coagulation (DIC), (iv) discusses the implications of tissue factor (TF) expression in the endothelium of P. falciparum infected patients, and (v) emphasizes the procoagulant role of parasitized red blood cells (RBCs) and activated platelets in the pathogenesis of malaria. This article also presents the Tissue Factor Model (TFM) for malaria pathogenesis, which places TF as the interface between sequestration, endothelial cell (EC) activation, blood coagulation disorder, and inflammation often associated with the disease. The relevance of the coagulation-inflammation cycle for the multiorgan dysfunction and coma is discussed in the context of malaria pathogenesis.

Extracorporeal blood purification in sepsis and sepsis-related acute kidney injury

Sepsis-related acute kidney injury (AKI) is an important complicating feature of sepsis, and is associated with greater complexity of care and higher mortality. Until recently, AKI lacked a standard, widely accepted definition, rendering it difficult to compare previously published strategies to prevent, recognize and treat this entity. Recently, the RIFLE classification of AKI has been developed, and confirmed in observational studies to be associated with subsequent morbidity and mortality. The management of sepsis-related AKI is evolving with new basic discoveries and ongoing translational clinical research, and will likely include nephroprotective strategies to protect kidneys in patients at risk, early recognition and amelioration of renal damage and pharmacological interventions to minimize injury and promote recovery. Furthermore, extracorporeal blood purification (EBP) has an important role to play, not only in the replacement of certain aspects of renal organ function such as acid-base/electrolyte homeostasis and extracellular fluid volume, but also in an immunomodulatory fashion. As a therapy that has the potential to influence the course of disease in sepsis, EBP in sepsis and sepsis-related AKI is the subject of this review.