Hemostatic effect of activated recombinant factor VII (rFVIIa) in liver disease: studies in an in vitro model

Reversal of apixaban induced alterations in hemostasis by different coagulation factor concentrates: significance of studies in vitro with circulating human blood

Apixaban is a new oral anticoagulant with a specific inhibitory action on FXa. No information is available on the reversal of the antihemostatic action of apixaban in experimental or clinical settings. We have evaluated the effectiveness of different factor concentrates at reversing modifications of hemostatic mechanisms induced by moderately elevated concentrations of apixaban (200 ng/ml) added in vitro to blood from healthy donors (n = 10). Effects on thrombin generation (TG) and thromboelastometry (TEM) parameters were assessed. Modifications in platelet adhesive, aggregating and procoagulant activities were evaluated in studies with blood circulating through damaged vascular surfaces, at a shear rate of 600 s(-1). The potential of prothrombin complex concentrates (PCCs; 50 IU/kg), activated prothrombin complex concentrates (aPCCs; 75 IU/kg), or activated recombinant factor VII (rFVIIa; 270 μg/kg), at reversing the antihemostatic actions of apixaban, were investigated. Apixaban interfered with TG kinetics. Delayed lag phase, prolonged time to peak and reduced peak values, were improved by the different concentrates, though modifications in TG patterns were diversely affected depending on the activating reagents. Apixaban significantly prolonged clotting times (CTs) in TEM studies. Prolongations in CTs were corrected by the different concentrates with variable efficacies (rFVIIa≥aPCC>PCC). Apixaban significantly reduced fibrin and platelet interactions with damaged vascular surfaces in perfusion studies (p<0.05 and p<0.01, respectively). Impairments in fibrin formation were normalized by the different concentrates. Only rFVIIa significantly restored levels of platelet deposition. Alterations in hemostasis induced by apixaban were variably compensated by the different factor concentrates investigated. However, effects of these concentrates were not homogeneous in all the tests, with PCCs showing more efficacy in TG, and rFVIIa being more effective on TEM and perfusion studies. Our results indicate that rFVIIa, PCCs and aPCCs have the potential to restore platelet and fibrin components of the hemostasis previously altered by apixaban.

Venous thromboembolism in cirrhosis

The cirrhosis population represents a unique subset of patients who are at risk for both bleeding and developing venous thromboembolic events (VTEs). It has been commonly misunderstood that these patients are naturally protected from thrombosis by deficiencies in coagulation factors. As a result, the cirrhosis population is often falsely perceived to be "autoanticoagulated." However, the concept of "autoanticoagulation" conferring protection from thrombosis is a misnomer. While patients with cirrhosis may have a bleeding predisposition, not uncommonly they also experience thrombotic events. The concern for this increased bleeding risk often makes anticoagulation a difficult choice. Prophylactic and therapeutic management of VTE in patients with cirrhosis is a difficult clinical problem with the lack of clear established guidelines. The elucidation of laboratory and/or clinical predictors of VTE will be useful in this setting. This review serves to examine VTE and the use of anticoagulation in the cirrhosis population.

Human recombinant activated factor VII for upper gastrointestinal bleeding in patients with liver diseases

BACKGROUND

Mortality from upper gastrointestinal bleeding in patients with liver disease is high. Recombinant human activated factor VII (rHuFVIIa) has been suggested for patients with liver disease and upper gastrointestinal bleeding.

OBJECTIVES

To assess the beneficial and harmful effects of rHuFVIIa in patients with liver disease and upper gastrointestinal bleeding.

SEARCH METHODS

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register (December 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Issue 4, 2011), MEDLINE (1948 to December 2011), EMBASE (1980 to December 2011), Science Citation Index Expanded (1900 to December 2011), and LILACS (December 2011). We sought additional randomised trials from the reference lists of the trials and reviews identified through the electronic searches.

SELECTION CRITERIA

Randomised clinical trials.

DATA COLLECTION AND ANALYSIS

Outcome data from randomised clinical trials were extracted and were presented using random-effects model meta-analyses. Data on the risk of bias in the included trials were also extracted.

MAIN RESULTS

We included two trials with 493 randomised participants with various Child-Pugh scores. The trials had a low risk of bias. The rHuFVIIa administration did not reduce the risk of mortality within five days (21/288 (7.3%) versus 15/205 (7.3%); risk ratio (RR) 0.88, 95% confidence interval (CI) 0.48 to 1.64, I(2) = 49%) and within 42 days (5/286 (1.7%) versus 36/205 (17.6%); RR 1.01, 95% CI 0.55 to 1.87, I(2) = 55%) when compared with placebo. Trial sequential analysis demonstrated that there is sufficient evidence to exclude that rHuFVIIa decreases mortality by 80%, but there is insufficient evidence to exclude smaller effects. The rHuFVIIa did not increase the risk of adverse events by number of patients (218/297 (74%) and 164/210 (78%); RR 0.94, 95% CI 0.84 to 1.04, I(2) = 1%), serious adverse events by adverse events reported (164/590 (28%) versus 123/443 (28%); RR 0.91, 95% CI 0.75 to 1.11, I(2) = 0%), and thromboembolic adverse events (16/297 (5.4%) versus 14/210 (6.7%); RR 0.80, 95% CI 0.40 to 1.60, I(2) = 0%) when compared with placebo.

AUTHORS' CONCLUSIONS

We found no evidence to support or reject the administration of rHuFVIIa for patients with liver disease and upper gastrointestinal bleeding. Further adequately powered randomised clinical trials are needed in order to evaluate the proper role of rHuFVIIa for treating upper gastrointestinal bleeding in patients with liver disease. Although the results are based on trials with low risk of bias, the heterogeneity and the small sample size result in rather large confidence intervals that cannot exclude the possibility that the intervention has some beneficial or harmful effect. Further trials with alow risk of bias are required to make more confident conclusions about the effects of the intervention.

Clinical Usefulness of Recombinant Activated Factor VII in Patients with Liver Failure Undergoing Invasive Procedures

Objective:

To evaluate the use of recombinant activated factor VII (rFVIIa) in patients with liver failure undergoing invasive procedures.

Methods:

An OVID/MEDUNE and PubMed search (1997-June 2011) was performed to identify literature on the use of rFVIIa to reduce bleeding risk in patients with liver failure undergoing invasive procedures.

Study Selection and Data Extraction:

English-language data evaluating the efficacy of rFVIIa to reverse coagulopathies prior to invasive procedures in patients with liver disease were included.

Data Synthesis:

Following administration of rFVIIa, prothrombin time (PT) and international normalized ratio (INR) response is within 30 minutes. Doses ranging from 20 to 120 μg/kg have been studied, with a reduction in PT seen in a dose-dependent manner. One study in patients with no bleeding administered 5, 20, and 80 μg/kg sequentially during a 24-day period. All doses provided reversal of prolonged PT within 10 minutes, and the duration was dose-dependent. In a study of 15 patients with fulminant liver failure, requiring intracranial pressure monitor placement, a rFVIIa dose of 40 μg/kg was compared to fresh frozen plasma. In patients who received rFVIIa, the PT and INR normalized, compared to none of the patients in the fresh frozen plasma group.

Conclusions:

Retrospective and prospective data demonstrate that rFVIIa effectively reverses elevated PT and INR, reducing the risk of bleeding and safely facilitating invasive procedures. Based on available data, a dose of 20-40 μg/kg 30 minutes prior to an invasive procedure should be considered in patients with acute or chronic liver failure at risk for bleeding complications. A major limitation of rFVIIa use is the high cost of therapy. A prospective, randomized trial could help determine the appropriate dose of rFVIIa, timing of dose in relationship to procedure, and usefulness of subsequent doses.

Redistribution and hemostatic action of recombinant activated factor VII associated with platelets

Clinical evidence accumulated from hemophilic patients during prophylaxis with recombinant activated factor VII (rFVIIa) suggests that the duration of the hemostatic action of rFVIIa exceeds its predicted plasma half-life. Mechanisms involved in this outcome have not been elucidated. We have investigated in vitro the redistribution of rFVIIa in platelets from healthy donors, patients with FVII deficiency, and one patient with Bernard-Soulier syndrome. Platelet-rich plasma was exposed to rFVIIa (3 to 60 μg/mL). Flow cytometry, immunocytochemistry, and coagulation tests were applied to detect and quantify rFVIIa. The hemostatic effect of rFVIIa associated to platelets was evaluated using perfusion models. Our studies revealed a dose-dependent association of rFVIIa to the platelet cytoplasm with redistribution into the open canalicular system, and α granules. Mechanisms implicated in the internalization are multiple, involve GPIb and GPIV, and require phospholipids and cytoskeletal assembly. After platelet activation with thrombin, platelets exposed rFVIIa on their membrane. Perfusion studies revealed that the presence of 30% of platelets containing FVIIa improved platelet aggregate formation and enhanced fibrin generation (P < 0.01 versus control). Our results indicate that, at therapeutic concentrations, rFVIIa can be internalized into platelets, where it is protected from physiological clearance mechanisms and can still promote hemostatic activity. Redistribution of rFVIIa into platelets may explain the prolonged prophylactic effectiveness of rFVIIa in hemophilia.

Coagulopathy in liver disease

The liver plays a central role in hemostasis, as it is the site of synthesis of clotting factors, coagulation inhibitors, and fibrinolytic proteins. The most common coagulation disturbances occurring in liver disease include thrombocytopenia and impaired humoral coagulation. Therapy's overall goal is not to achieve complete correction of laboratory value abnormalities but to gain hemostasis. Therapy with vitamin K may be a useful option in patients with increased prothrombin time due to vitamin K deficiency; in patients with malnutrition; in patients using antibiotics; and in patients with cholestatic liver disease, particularly prior to invasive procedures. Infusion of fresh frozen plasma is more often effective and is recommended in patients with liver disease before invasive procedures or surgery, as such patients require transient correction in their prothrombin time. Therapy with plasma exchange may be considered in patients who cannot be treated with fresh frozen plasma due to volume overload risk. In patients with severe coagulopathy and hypofibrinogenemia, cryoprecipitate therapy is ideal. Therapy with prothrombin-complex concentrate is seldom pursued in patients with liver disease due to high risk of thrombotic complications. Transfusions of platelets are appropriate for patients with thrombocytopenia (< 50,000/mm(3)) associated with active bleeding or before invasive procedures in which a short-term platelet count increase is noted. Trial with desmopressin may be considered before invasive procedures in patients with liver disease and with refractory and prolonged bleeding time. Recombinant activated factor VIIa administration is suggested for patients with significantly prolonged prothrombin time and contraindications to fresh frozen plasma therapy; however, this is expensive. Thrombopoietin and interleukin-11 are currently investigational for patients with thrombocytopenia of chronic liver disease. Liver transplantation completely restores impaired coagulation abnormalities and is the ultimate intervention that corrects coagulopathy of advanced liver disease and liver failure.

Review article: blood platelet number and function in chronic liver disease and cirrhosis

BACKGROUND

The liver plays a central role in coagulation and fibrinolysis but is also closely intertwined with the function and number of blood platelets.

AIM

To describe and integrate all literature concerning blood platelets and liver disease by performing a thorough literature research.

METHODS

A thorough literature research on 'blood platelets' and 'liver disease' was performed.

RESULTS

Thrombocytopenia is a marked feature of chronic liver disease and cirrhosis. Traditionally, this thrombocytopenia was attributed to passive platelet sequestration in the spleen. More recent insights suggest an increased platelet breakdown and to a lesser extent decreased platelet production plays a more important role. Besides the reduction in number, other studies suggest functional platelet defects. This platelet dysfunction is probably both intrinsic to the platelets and secondary to soluble plasma factors. It reflects not only a decrease in aggregability, but also an activation of the intrinsic inhibitory pathways. The net effect, finally, is a decreased platelet function in the various types of chronic liver diseases and cirrhosis. Finally, recent data suggest that platelets are not only affected by but can also contribute to the liver disease process, as for instance, in viral hepatitis and cholestatic liver disease.

CONCLUSION

Platelet research in liver disease is a growing area of investigation and could provide new pathophysiological insights.

Liver cirrhosis, other liver diseases, and risk of hospitalisation for intracerebral haemorrhage: a Danish population-based case-control study

Background

Liver diseases are suspected risk factors for intracerebral haemorrhage (ICH). We conducted a population-based case-control study to examine risk of ICH among hospitalised patients with liver cirrhosis and other liver diseases.

Methods

We used data from the hospital discharge registries (1991–2003) and the Civil Registration System in Denmark, to identify 3,522 cases of first-time hospitalisation for ICH and 35,173 sex- and age-matched population controls. Among cases and controls we identified patients with a discharge diagnosis of liver cirrhosis or other liver diseases before the date of ICH. We computed odds ratios for ICH by conditional logistic regressions, adjusting for a number of confounding factors.

Results

There was an increased risk of ICH for patients with alcoholic liver cirrhosis (adjusted OR = 4.8, 95% CI: 2.7–8.3), non-alcoholic liver cirrhosis (adjusted OR = 7.7, 95% CI: 2.0–28.9) and non-cirrhotic alcoholic liver disease (adjusted OR = 5.4, 95%CI:3.1–9.5) but not for patients with non-cirrhotic non-alcoholic liver diseases (adjusted OR = 0.9, 95%CI:0.5–1.6). The highest risk was found among women with liver cirrhosis (OR = 8.9, 95%CI:2.9–26.7) and for patients younger than 70 years (OR = 6.1, 95%CI:3.4–10.9). There were no sex- or age-related differences in the association between other liver diseases (alcoholic or non-alcoholic) and hospitalisation with ICH.

Conclusion

Patients with liver cirrhosis and non-cirrhotic alcoholic liver disease have a clearly increased risk for ICH.

Platelets interact with tissue factor immobilized on surfaces: effects of shear rate

BACKGROUND

While procoagulant activities of Tissue Factor (TF) have been widely investigated, its possible pro-adhesive properties towards platelets have not been studied in detail.

MATERIAL AND METHODS

We explored the interaction of platelets with human Tissue Factor (hTF) firmly adsorbed on a synthetic surface of polyvinilidene difluoride (PVDF) using different shear rates. For studies at 250 and 600 s(-1), TF firmly adsorbed was exposed to flowing anticoagulated blood in flat perfusion devices. Deposition of platelets and fibrin were evaluated by morphometric, immunocytochemical and ultrastructural methods. Prothrombin fragment 1 + 2 (F1 + 2) levels were also measured. Experiments at 5000 s(-1), were performed on the Platelet Function Analyzer (PFA-100) with experimental cartridges with collagen (COL) or collagen-hTF (COL + TF). Haemostatic effect of recombinant activated FVIIa (rFVIIa) was assessed in the same experimental settings.

RESULTS

Platelet deposition on hTF reached 19.8 +/- 1.3% and 26.1 +/- 3.4% of the total surface, at 250 and 600 s(-1), respectively. Fibrin formation was significantly higher at 250 s(-1) than at 600 s(-1) (P < 0.05). The addition of rFVIIa did not influence platelet deposition but raised fibrin formation and thrombin generation at both shear rates (P < 0.05). At 5000 s(-1), closure times (CT) in the PFA-100 were significantly shortened in the presence of hTF (154.09 +/- 14.69 s vs. 191.45 +/- 16.09 s COL alone; P < 0.05). Addition of rFVIIa did not cause a further reduction of CT.

CONCLUSIONS

Our studies demonstrate that hTF is an adhesive substrate for platelets and suggest that the von Willebrand factor could mediate these interactions. At low and intermediate shear rates, rFVIIa enhanced the procoagulant action of hTF, but this effect was not observed at very high shear rates.

Human recombinant activated factor VII for upper gastrointestinal bleeding in patients with liver diseases

BACKGROUND

Mortality from upper gastrointestinal bleeding in patients with liver disease is high. The human recombinant activated factor VII is one of the suggested treatments for upper gastrointestinal bleeding in these patients.

OBJECTIVES

To assess the beneficial and harmful effects of human recombinant factor VIIa in patients with liver disease and upper gastrointestinal bleeding.

SEARCH STRATEGY

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, ISI Web of Knowledge, and LILACS. The search strategies used are given in Table 01. We sought additional randomised trials from the reference lists of the trials and reviews identified through the electronic searches.

SELECTION CRITERIA

All randomised clinical trials irrespective of design, publication status, and language comparing human recombinant activated factor VII versus placebo, or any other control intervention for patients with liver disease and upper gastrointestinal bleeding, irrespectively of aetiology.

DATA COLLECTION AND ANALYSIS

We estimated relative risks (RR) for dichotomous outcomes and mean differences for continuous data. Since only one trial was identified, meta-analysis was not possible.

MAIN RESULTS

We included one trial with 242 adult patients. In this study, human recombinant activated factor VII administration did not reduce the risk of death (mortality within five days (RR 1.75, 95% confidence interval (CI) 0.53 to 5.82), and mortality within 42 days (RR 1.45, 95% CI 0.70 to 3.00)).

AUTHORS' CONCLUSIONS

We found no evidence that human recombinant activated factor VII reduces the risk of death in patients with liver disease and upper gastrointestinal bleeding. However, we made our conclusion on a single randomised clinical trial. More randomised clinical trials having low risk of bias are necessary in order to determine the role of human recombinant factor VIIa in clinical practice.

Mechanism of action, development and clinical experience of recombinant FVIIa

Recombinant FVIIa has been developed for treatment of bleedings in hemophilia patients with inhibitors, and has been found to induce hemostasis even during major surgery such as major orthopedic surgery. Recombinant FVIIa is being produced in BHK cell cultures and has been shown to be very similar to plasma-derived FVIIa. The use of rFVIIa in hemophilia treatment is a new concept of treatment and is based on the low affinity binding of FVIIa to the surface of thrombin activated platelets demonstrated in a cell-based in vitro model. By the administration of pharmacological doses of exogenous rFVIIa the thrombin generation on the platelet surface at the site of injury is enhanced independently of the presence of FVIII/FIX. As a result of the increased and rapid thrombin formation, a tight fibrin hemostatic plug is being formed. A tight fibrin structure has been found to be more resistant to fibrinolytic degradation thereby helping to maintain hemostasis. The general mechanism of action of pharmacological doses of rFVIIa shown to induce hemostasis not only in hemophilia, but also in patients with platelet defects, and with profuse bleedings triggered by extensive surgery or trauma, may very well be the capacity of generating a tight fibrin hemostatic plug through the increased thrombin generation. Such a fibrin plug will help to resist the overwhelming mostly local release of fibrinolytic activity triggered by the vast tissue damage occurring in extensive trauma. A release of fibrinlytic activity locally has also been demonstrated to occur in the gastrointestinal tract as well as during profuse postpartum bleedings. Pharmacological doses of rFVIIa have in fact, also been shown to induce hemostasis in such cases.

Recombinant factor VIIa reduces transfusion requirements in liver transplant patients with high MELD scores

Patients undergoing orthotopic liver transplantation (OLT) often experience significant coagulopathy and remain at risk for excessive blood loss and massive transfusion. The ability of recombinant factor VIIa (rFVIIa) to reduce transfusion requirements during OLT has not been well established. This retrospective study investigates whether rFVIIa reduces transfusion requirements in liver transplant patients with a significantly prolonged prothrombin time (PT) and a model of end-stage liver disease (MELD) score of > 20. Eleven patients received a single dose of rFVIIa (58 +/- 18 microg kg(-1)) at the time of incision. This group was matched with a selected control group that fulfilled all of the inclusion/exclusion criteria. Patient characteristics, pre-operative PT, HCT, PLT and MELD were identical between groups. Prophylactic application of rFVIIA reduced packed red blood cells (3.9 +/- 2.6 versus 6.9 +/- 2.3 U, P = 0.01) and fresh-frozen plasma (FFP) (12.6 +/- 6 versus 19.8 +/- 7 U, P = 0.018) transfusion requirements when compared with the control group. FFP administration in the first 24 h after surgery was also significantly less in the rVIIa group when compared with the control group (388 +/- 385 versus 1225 +/- 701 mL, P = 0.003). Hospital stay following transplantation tended to be shorter in the rFVIIa group, albeit statistical significance was not achieved (11 +/- 7.3 versus 7.9 +/- 2.7, P = 0.2). All but one patient in the control group survived for 30 days after transplantation. In a selected group of patients with prolonged PT and high MELD score, the prophylactic application of rFVIIa at the start of the OLT may reduce perioperative transfusion requirements.

Recombinant factor VIIa enhances platelet adhesion and activation under flow conditions at normal and reduced platelet count

BACKGROUND

Recombinant factor VIIa (rFVIIa), which was developed for treatment of inhibitor-complicated hemophilia, appears suitable as prohemostatic agent in other clinical disorders including patients with thrombocytopenia. It is generally accepted that rFVIIa functions by enhancement of thrombin generation at the site of injury. It is, however, unknown if and how this affects platelet adhesion and aggregation.

OBJECTIVES

To determine the effect of rFVIIa-mediated thrombin generation on platelet adhesion and aggregation under flow conditions at normal and reduced platelet counts.

METHODS

Washed platelets and red cells were combined to obtain plasma-free blood with different platelet counts. The reconstituted blood was perfused over a collagen- or fibrinogen-coated surface in the absence or presence of a thrombin generating system consisting of purified coagulation factors rFVIIa, factor (F)X and prothrombin.

RESULTS

Addition of coagulation factors rFVIIa, FX and prothrombin to washed platelets and red cells enhanced platelet adhesion and aggregation to collagen and adhesion and spreading to fibrinogen at normal platelet count and at platelet numbers as low as 10 000 microL(-1). rFVIIa-mediated thrombin generation enhanced the activation state of platelets as measured by intracellular calcium fluxes, and enhanced the exposure of procoagulant phospholipids as measured by annexin A5 binding.

CONCLUSIONS

Taken together, increased platelet adhesion and aggregation by rFVIIa-mediated thrombin formation may explain the therapeutic effects of rFVIIa in thrombocytopenic conditions and in patients with a normal platelet count by (i) enhancement of primary hemostasis and (ii) enhancement of procoagulant surface leading to elevated fibrin formation.