Thrombin generation test in children and adolescents with chronic liver disease

Thrombin generation in children using ThromboScreen reagent kit with ST Genesia-A pilot study

INTRODUCTION

Thrombin generation assays assess overall coagulation system and are widely used in research; however, they still need standardization and clinical validation. The new ST Genesia is a benchtop, automated analyzer that normalizes each thrombin generation parameter using a reference plasma. The ThromboScreen reagent kit has two triggers, one of which contains thrombomodulin to assess the effect of the protein C pathway. This study aimed to make a pilot approach to the ThromboScreen reference range in children and evaluate the impact of sex, age, and pro- and anticoagulant plasma proteins on thrombin generation parameters.

METHODS

This study included 55 healthy children from the following age groups: 1-6 years (n = 14), 7-11 years (n = 15), and 12-17 years (n = 26). Children younger than 1 year were excluded from the study. We measured thrombin generation using ThromboScreen, coagulation routine and test, pro- and anticoagulant proteins.

RESULTS

Age did not influence ThromboScreen results. Males showed significantly lower endogenous thrombin potential and peak height values than females. The strongest determinants of endogenous thrombin potential were von Willebrand factor parameters, whereas for endogenous thrombin potential inhibition, the strongest determinants were protein C and protein S. No statistically significant differences were found between groups on temporal parameters.

CONCLUSIONS

For the ThromboScreen reagent kit, it may not be necessary to subdivide reference ranges according to age for children (>1 year).

Evidence for a rebalanced hemostatic system in pediatric liver transplantation: A prospective cohort study

In adults with end-stage liver disease concurrent changes in pro- and antihemostatic pathways result in a rebalanced hemostasis. Children though, have a developing hemostatic system, different disease etiologies, and increased risk of thrombosis. This study aimed to assess the hemostatic state of children during and after liver transplantation. Serial blood samples were obtained from 20 children (≤16 years) undergoing primary liver transplantation (September 2017-October 2018). Routine hemostasis tests, thrombomodulin-modified thrombin generation, clot lysis times, and hemostatic proteins were measured. Reference values were established using an age-matched control group of 30 children. Thrombocytopenia was present in study patients. Von Willebrand factors were doubled and ADAMTS13 levels decreased during and after transplantation up until day 30, when platelet count had normalized. Whereas prothrombin time and activated partial thromboplastin time were prolonged during transplantation, thrombin generation was within normal ranges, except during perioperative heparin administration. Fibrinogen, factor VIII levels, and clot lysis time were elevated up until day 30. In conclusion, children with end-stage liver disease are in tight hemostatic balance. During transplantation a temporary heparin-dependent hypocoagulable state is present, which rapidly converts to a hemostatic balance with distinct hypercoagulable features that persist until at least day 30. This hypercoagulable state may contribute to the risk of posttransplant thrombosis.

Coagulopathy in Children With Liver Disease

It was thought that a high international normalized ratio predicted bleeding in patients with chronic liver disease (CLD) and patients were "autoanticoagulated." Contrary to this belief, while patients with CLD experienced bleeding, they also developed thromboses. In the last decade, the prevailing literature challenged the idea that an elevated international normalized ratio increased bleeding risk. The global assays of coagulation such as thromboelastography (TEG)/rotational thromboelastometry and thrombin generation assays provide additional insight into coagulation processes. It has become apparent that a parallel reduction of procoagulant and anticoagulant factors leave patients in a new "balanced" state, albeit a fragile one, where the balance can be easily disrupted. The inherent differences in coagulation between children and adults such as differences in levels of procoagulant and anticoagulant factors, underlying liver disease, and the paucity of studies in children make extrapolation of these findings to the pediatric population problematic. Ultimately, this is an area that requires further investigation to avoid inappropriate use of blood products and medication.

Characterization of the coagulation profile in children with liver disease and extrahepatic portal vein obstruction or shunt

INTRODUCTION

Chronic liver disease causes a disruption of procoagulant and anticoagulant factors, resulting in a fragile state, prone to increased rates of both bleeding and thrombosis. Currently, there is limited literature describing the changes observed in pediatric liver disease and extrahepatic portal vein obstruction or shunt. This study aimed to describe the changes that occur in children with chronic liver disease and extrahepatic portal vein obstruction or shunt.

MATERIALS AND METHODS

We measured the concentration and activity of key procoagulant and anticoagulant factors in children with liver disease, children with extrahepatic portal vein obstruction or shunt, and healthy children.

RESULTS

Children with severe liver disease had coagulopathic changes, including either decreased concentration or activity of factor II, factor V, and factor VII. Nineteen percent (8/42) of the cohort had significant bleeding. Thrombophilic changes were also observed, including decreased concentration or activity of protein C, protein S, and antithrombin and increased concentration and activity of factor VIII and Von Willebrand factor. Similar coagulation factor changes were observed in children with extrahepatic portal vein obstruction or shunt. There was a trend toward greater changes in coagulation factor activity compared to concentration.

CONCLUSION

This study provides a detailed description of the changes in both the concentration and activity of coagulation factors in pediatric liver disease and extrahepatic portal vein obstruction or shunt. Interestingly, procoagulant and anticoagulant factors were deranged in portal vein obstruction or shunt to a similar degree as in liver disease. An improved understanding of the coagulation profile in the pediatric setting will contribute to the improved management of liver disease and extrahepatic portal obstruction or shunt.

ABBREVIATIONS

PELD: pediatric end-stage liver disease score; MELD: model for end-stage liver disease score; ELISA: enzyme-linked immunosorbent assay; MCRI: Murdoch Childrens Research Institute; FII: factor II; FV: factor V; FVII: factor VII; FVIII: factor VIII; AT: antithrombin III; A2M: alpha-2-macroglobulin; vWF: Von Willebrand factor; PC: protein C; PS: protein S; ISTH-BAT: International Society on Thrombosis and Haemostasis Bleeding Assessment Tool.

A conceptual and practical approach to haemostasis in paediatric liver disease

Children with liver disease can develop severe bleeding episodes and thrombosis. Liver failure usually results in decreased levels of procoagulant and anticoagulant factors. Additional risk factors, including changes in vascular flow and endothelial function, are of importance for the development of bleeding or thrombosis in individual vascular beds. Detailed studies of haemostatic disturbances in the setting of paediatric liver disease are sparse and extrapolation from adult studies is common. The spectrum of liver diseases and the haemostatic system differs between children and adults. Specific paediatric liver diseases are reported to have more distinctive effects on haemostasis and the risk of bleeding and/or thrombosis.

CONCLUSION

we propose a model regarding haemostasis in paediatric liver disease, taking into account a number of specific variables and mechanisms, as well as the type of liver disease, which will provide a framework for clinical decision-making in these complex patients.

Coagulopathy and transfusion therapy in pediatric liver transplantation

Bleeding and coagulopathy are critical issues complicating pediatric liver transplantation and contributing to morbidity and mortality in the cirrhotic child. The complexity of coagulopathy in the pediatric patient is illustrated by the interaction between three basic models. The first model, "developmental hemostasis", demonstrates how a different balance between pro- and anticoagulation factors leads to a normal hemostatic capacity in the pediatric patient at various ages. The second, the "cell based model of coagulation", takes into account the interaction between plasma proteins and cells. In the last, the concept of "rebalanced coagulation" highlights how the reduction of both pro- and anticoagulation factors leads to a normal, although unstable, coagulation profile. This new concept has led to the development of novel techniques used to analyze the coagulation capacity of whole blood for all patients. For example, viscoelastic methodologies are increasingly used on adult patients to test hemostatic capacity and to guide transfusion protocols. However, results are often confounding or have limited impact on morbidity and mortality. Moreover, data from pediatric patients remain inadequate. In addition, several interventions have been proposed to limit blood loss during transplantation, including the use of antifibrinolytic drugs and surgical techniques, such as the piggyback and lowering the central venous pressure during the hepatic dissection phase. The rationale for the use of these interventions is quite solid and has led to their incorporation into clinical practice; yet few of them have been rigorously tested in adults, let alone in children. Finally, the postoperative period in pediatric cohorts of patients has been characterized by an enhanced risk of hepatic vessel thrombosis. Thrombosis in fact remains the primary cause of early graft failure and re-transplantation within the first 30 d following surgery, and it occurs despite prolongation of standard coagulation assays. Data, however, are currently lacking regarding the use of anti-aggregation/anticoagulation therapies and how to best monitor for thrombosis in the early postoperative period in pediatric patients. Therefore, further studies are necessary to elucidate the interaction between the development of the coagulation system and cirrhosis in children. Moreover, strategies to optimize blood transfusion and anticoagulation must be tested specifically in pediatric patients. In conclusion, data from the adult world can be translated with difficulty into the pediatric field as indication for transplantation, baseline pathologies and levels of pro- and anticoagulation factors are not comparable between the two populations.