Hemostatic defects in end stage liver disease

Pivotal role of ADAMTS13 function in liver diseases

The liver is a major source of clotting and fibrinolytic proteins, and plays a central role in thrombo-regulation. Patients with advanced liver diseases tend to bleed because of reduced plasma levels of several clotting factors and thrombocytopenia, but they do also exhibit thrombotic complications. ADAMTS13 is a metalloproteinase, produced exclusively in hepatic stellate cells, and specifically cleaves highly multimeric von Willebrand factor (VWF). VWF plays a pivotal role in hemostasis and thrombosis, and its function is dependent on its multimeric state. Deficiency of ADAMTS13 results in accumulation of unusually large VWF multimers (UL-VWFM) in plasma, in turn induces platelet clumping or thrombi under high shear stress, followed by microcirculatory disturbances. Considering that UL-VWFM, the substrate of ADAMTS13, is produced in transformed vascular endothelial cells at sites of liver injury, decreased ADAMTS13 activity may be involved in not only sinusoidal microcirculatory disturbances, but also subsequent progression of liver injuries, eventually leading to multiorgan failure. This concept can be applied to the development or aggravation of liver diseases, including liver cirrhosis, alcoholic hepatitis, veno-occlusive disease, and adverse events after liver transplantation. These results promise to bring further understanding of the pathophysiology of liver diseases, and offer new insight for development of therapeutic strategies.

Relationship between serum thrombopoietin level and Child-Pugh grade in patients with liver cirrhosis

AIM: To assess the relationship between serum thrombopoietin (TPO) level and Child-Pugh grade in patients with liver cirrhosis.

METHODS: One hundred and nineteen liver cirrhotic patients (experimental group) and 30 healthy volunteers (control group) were included in the study. Serum TPO level was detected by enzyme-linked immunosorbent assay (ELISA). Meanwhile, routine blood tests, blood biochemistry tests, detection of hepatitis virus markers, and color Doppler ultrasound examination of the liver were performed.

RESULTS: Based on clinical manifestations and laboratory examinations, 43 patients were classified as having Child-Pugh class A cirrhosis, 63 as having Child-Pugh class B cirrhosis, and 13 as having Child-Pugh class C cirrhosis. No significant difference was noted in serum TPO level between the control group and the experimental group. Patients with Child-Pugh class A cirrhosis had higher serum TPO level than normal controls (P = 0.19), while those with Child-Pugh class B or C cirrhosis had significantly lower serum TPO levels (43.44 ng/L ± 33.51 ng/L and 45.16 ng/L ± 30.04 ng/L, respectively; P = 0.001 and 0.048, respectively) than normal controls. Platelet counts (PLT) in patients with Child-Pugh class A, B or C cirrhosis were significantly lower than that in normal controls (all P < 0.001). Serum TPO was negatively correlated with PLT in normal controls (r = - 0.363, P = 0.048). Although no correlation was noted between serum TPO and PLT in patients with Child-Pugh class A or C cirrhosis, a positive correlation was found between serum TPO and PLT in patients with Child-Pugh class B cirrhosis (r = 0.383, P = 0.002).

CONCLUSION: Reduced hepatic synthesis of TPO is important for the development of thrombocytopenia in cirrhotic patients. Serum TPO and PLT can be used as parameters for evaluation of liver function.

The effect of hepatectomy on coagulation: an evaluation by thromboelastography

OBJECTIVES

Liver has a major role in coagulation. The hemostatic derangements measured by the mostly used coagulation parameters as prothrombin time, activated partial thromboplastin time, and thrombocyte count do not always correlate with the bleeding associated with liver diseases and these factors do not measure the thrombotic risks. So, thromboelastography is used in new clinical and laboratory research. The aim of this study is to study the effect of different levels of hepatectomy on coagulation.

METHODS

Laparatomy, 40% hepatectomy, and 70% hepatectomy was performed in three different groups of rats. Prothrombin time, international normalized ratio, activated partial thromboplastin time, thrombocyte count, fibrinogen levels, and thromboelastography parameters were obtained at the 0, 6, and 24th hour of the study.

RESULTS

Fibrinogen level at the 24th hour was greater than the early hours in both of the hepatectomy groups. Prothrombin time and international normalized ratio values were significantly higher in hepatectomy groups than in the sham group. There were no statistically significant difference in the clotting time, clot formation time, alpha-angle, and maximum clot firmness values in any of the thromboelastography channels, in any of the study times, in between the sham, 40% hepatectomy, and 70% hepatectomy groups.

CONCLUSION

There is no difference between 40 and 70% hepatectomy when the coagulopathy is evaluated. The coagulation derangements as reflected by the increase in fibrinogen and prolongation of prothrombin time and activated partial thromboplastin time after hepatectomy were not supported by thromboelastography parameters in this study.

Liver disease, coagulation testing, and hemostasis

This article reviews the variety of coagulation testing abnormalities identified and the evidence demonstrating their lack of correlation with hemostasis and inability to predict bleeding for patients with liver disease. The article discusses the historical and incorrect evolution of the commonly used "1.5x" prothrombin time/international normalized ratio "threshold" for fresh frozen plasma/frozen plasma (FFP/FP) administration. Finally, this article reviews why FFP/FP cannot correct minimally prolonged clotting times in patients with liver disease, nor provide adequate prophylaxis against bleeding from percutaneous liver biopsy.

Hyperfibrinolysis in liver disease

The incidence of hyperfibrinolysis in patients with cirrhosis is still debated. The reasons for this uncertainty probably lie in the lack of appropriate laboratory tests for its evaluation. There is a relative consensus, however, that hyperfibrinolysis can complicate the clinical course of liver cirrhosis, especially in cases of moderate to severe liver failure. Hyperfibrinolysis correlates positively with the severity of underlying liver disease, and low-grade systemic fibrinolysis is found in 30% to 46% of patients who have end-stage liver disease. Accelerated intravascular coagulation with secondary hyperfibrinolysis has been reported in patients who have liver failure. Hyperfibrinolysis may delay primary hemostasis, thereby aggravating variceal bleeding and facilitating recurrence.

Use of Recombinant Factor VIIa in Inherited and Acquired von Willebrand Disease

Recombinant factor VIIa (rFVIIa) is increasingly used outside the labeled indications for the treatment of life-threatening bleeding episodes after failure of respective standard therapy. In this article, the authors focus on the use of the agent in patients with inherited or acquired von Willebrand disease (vWD). Although the current experience is sparse, published cases indicate the high efficacy of rFVIIa for the treatment of patients refractory to conventional treatment. The agent may be used in patients with congenital vWD complicated by alloantibodies directed against substituted von Willebrand factor or in the presence of concomitant hemostatic defects as well as acquired vWD with hitherto limited therapeutic options. Controlled clinical studies are necessary to define the use of rFVIIa in this clinical setting.

Review article: coagulation disorders in chronic liver disease

BACKGROUND

The liver is the site for synthesis of the vast majority of proteins that play a central role in maintaining hemostasis, by participating in the regulation of coagulation and fibrinolysis.

AIM

To summarize the available data on the impact of coagulation disorders in patients with chronic liver disease.

RESULTS

Hepatocellular damage in patients with severe liver disease can lead to abnormalities in the production and function of coagulation and fibrinolytic factors, disrupting the balance between coagulation and anticoagulation systems.

CONCLUSIONS

Hemostatic abnormalities (eg. impaired synthesis of clotting factors, heightened fibrinolysis, disseminated intravascular coagulation, thrombocytopenia, and platelet dysfunction) can increase the risk of bleeding in cirrhotic patients.

Overview of the human pharmacokinetics of recombinant activated factor VII

AIMS

To review the pharmacokinetics of rFVIIa in various patient populations, and to discuss the differences observed between groups.

METHODS

Based on a registry of Novo Nordisk studies, 14 studies evaluating rFVIIa pharmacokinetics following single and multiple bolus administration in healthy volunteers, adult and paediatric patients with congenital haemophilia and inhibitors, patients undergoing liver surgery and in patients with cirrhosis, inherited FVII deficiency, upper gastrointestinal bleeding or severe trauma were identified. Data on rFVIIa PK, analyzed with noncompartmental and population pharmacokinetic methods, were extracted.

RESULTS

Plasma clearance was a more robust parameter than half-life for comparing rFVIIa pharmacokinetics between groups. In healthy volunteers and patients with no or low-level bleeding (e.g. adults with haemophilia, nonbleeding patients with cirrhosis), plasma clearance was relatively low (30-40 ml kg(-1) h(-1)). In children with haemophilia and adults with high-level bleeding (e.g. cirrhotic patients undergoing orthotopic liver transplantation or resection) and patients with congenital FVII deficiency, plasma clearance was relatively higher (60-90 ml kg(-1) h(-1)).

CONCLUSIONS

Comparison of plasma clearance rates in different patient populations suggested that subjects fall into two distinct groups. These differences may have clinical implications in terms of how to adapt the rFVIIa dosing regimen, depending on the expected bleeding rate/blood loss and underlying disease.