The regulation of the factor VII-dependent coagulation pathway: rationale for the effectiveness of recombinant factor VIIa in refractory bleeding disorders

Improved hemostasis in hemophilia mice by means of an engineered factor Va mutant

BACKGROUND

Factor (F)VIIa-based bypassing not always provides sufficient hemostasis in hemophilia.

OBJECTIVES

To investigate the potential of engineered activated factor V (FVa) variants as bypassing agents in hemophilia A.

METHODS

Activity of FVa variants was studied in vitro using prothrombinase assays with purified components and in FV- and FVIII-deficient plasma using clotting and thrombin generation assays. In vivo bleed reduction after the tail clip was studied in hemophilia A mice.

RESULTS AND CONCLUSIONS

FVa mutations included a disulfide bond connecting the A2 and A3 domains and ones that rendered FVa resistant to inactivation by activated protein C (APC). '(super) FVa,' a combination of the A2-A3 disulfide (A2-SS-A3) to stabilize FVa and of APC-cleavage site mutations (Arg506/306/679Gln), had enhanced specific activity and complete APC resistance compared with wild-type FVa, FVL eiden (Arg506Gln), or FVaL eiden (A2-SS-A3). Furthermore, (super) FVa potently increased thrombin generation in vitro in FVIII-deficient plasma. In vivo, (super) FVa reduced bleeding in FVIII-deficient mice more effectively than wild-type FVa. Low-dose (super) FVa, but not wild-type FVa, decreased early blood loss during the first 10 min by more than two-fold compared with saline and provided bleed protection for the majority of mice, similar to treatments with FVIII. During the second 10 min after tail cut, (super) FVa at high dose, but not wild-type FVa, effectively reduced bleeding. These findings suggest that (super) FVa enhances not only clot formation but also clot stabilization. Thus, (super) FVa efficiently improved hemostasis in hemophilia in vitro and in vivo and may have potential therapeutic benefits as a novel bypassing agent in hemophilia.

Recombinant activated factor VII in patients with acute liver failure with UNOS Status 1A: a single tertiary academic centre experience

BACKGROUND AND OBJECTIVES

Recombinant activated factor VII (rFVIIa) is often used in off-label indications, including many situations in which the patients are at risk of thrombosis. In this study, we retrospectively reviewed the use of rFVIIa in patients with acute liver failure - UNOS Status 1A (ALF-1A) to determine its efficacy and safety profile.

MATERIALS AND METHODS

Using the transplantation records, all adult patients with ALF-1A were identified from 6/2001 to 3/2009. From patients' medical charts, rFVIIa dose, blood component usage, short-term outcomes [length of intensive care unit (ICU) and hospital stay, ability to undergo orthotopic liver transplant (OLT) and in-hospital survival rate] and adverse events were examined.

RESULTS

Forty-two patients with ALF-1A were identified. Fifteen patients received rFVIIa with doses ranging between 24·4 μg/kg and 126·8 μg/kg. Three patients received two doses of rFVIIa. The age, baseline activated partial thromboplastin time (aPTT) and platelet (PLT) count were not statistically different between the group receiving rFVIIa versus the group that did not. However, the prothrombin time (PT) was significantly higher in the rFVIIa group. Although the rFVIIa group stayed in the ICU longer and required significant more blood products during admission, there was no statistical difference between the two groups in terms of length of hospital stay, ability to undergo OLT and survival rate. There was no increase in complications, including thrombosis, after receiving rFVIIa.

CONCLUSION

Recombinant activated factor VII (rFVIIa) appears to be safe in patients with ALF-1A, but to elucidate its full role, a randomized controlled trial would be ideal.

Tissue factor controversies

Tissue factor plays a primary role in both hemorrhage control and thrombosis depending upon whether its presentation is extravascular or intravascular. The molecular architecture and function of the tissue factor molecule and its role in the activations of factor IX and factor X have been elegantly elucidated but controversies prevail with respect to distinctions between tissue factor sources and tissue factor "activity." This presentation will review data on the architecture and functions of the tissue factor-factor VIIa complex and discuss the elements of the controversies associated with tissue factor presentation in both normal and pathologic milieu.

Recombinant factor VIIa in trauma patients without coagulation disorders

Recombinant activated factor VIIa (rFVIIa) has many clinical applications for patients with congenital bleeding disorders and in a variety of clinical settings. Additional studies in the future are ongoing and should provide the clinical anesthesiologist an additional option during certain bleeding states. Specific recommendations as to timing of administration and frequent monitoring of ionized calcium status are suggested at this time. Optimization of fibrinogen levels, platelet levels, pH, and body temperature will enhance efficacy of rFVIIa.

The role of tissue factor and factor VIIa in hemostasis

Tissue factor (TF) is a transmembrane receptor for Factor VII/VIIa (FVII/VIIa). It is constitutively expressed by cells surrounding blood vessels. The endothelium physically separates this potent "activator" from its circulating ligand FVII/FVIIa and prevents inappropriate activation of the clotting cascade. Breakage of the endothelial barrier leads to exposure of extravascular TF and rapid activation of the clotting cascade. TF is also expressed in certain tissues, such as the heart and brain, and provides additional hemostatic protection to these tissues. Small amounts of TF are also present in blood in the form of microparticles, which are small membrane vesicles derived from activated and apoptotic cells. Levels of microparticle TF increase in a variety of diseases, such as sepsis and cancer, and this so-called "blood-borne" TF may contribute to thrombosis associated with these diseases. Recombinant FVIIa has been developed as an effective hemostatic drug for the treatment of hemophilia patients with inhibitory antibodies. In addition, it is used for patients with bleeding that do not respond to conventional therapy. However, the mechanism by which recombinant FVIIa restores hemostasis has not been clearly defined. In conclusion, the TF:FVIIa complex is essential for hemostasis and recombinant FVIIa is an effective hemostatic drug.

Differential clot stabilising effects of rFVIIa and rFXIII-A2 in whole blood from thrombocytopenic patients and healthy volunteers

The haemostatic effect of recombinant activated factor VII (rFVIIa;NovoSeven) in thrombocytopenic patients has been a matter of controversy. Haemostasis by rFVIIa occurs via FVIIa-mediated thrombin generation in a platelet-dependent manner and may therefore be suboptimal in patients without functional platelets. Under such conditions, a clot-stabilizing agent, such as factor XIII (FXIII), may supplement the effect ofrFVIIa and improve haemostasis. Recombinant factor XIII (rFXIII-A2) is produced as an A2 homodimer of the FXIII A subunit and is equivalent to cellular FXIII normally found in platelets. The combined effects of rFVIIa andrFXIII-A2 were evaluated in clot lysis assays using factor XIII-deficient plasma and by whole blood thrombelastography (TEG) analysis from normal donors and thrombocytopenic stem cell transplantation patients. Clotting time was shortened by rFVIIa (0.6-10 microg/ml). rFVIIa only modestly improved anti-fibrinolysis,whereas rFXIII-A2 (0-20 microg/ml) enhanced anti-fibrinolysis without effect on clotting time. TEG analysis showed rFVIIa shortened the clotting time, and enhanced clot development, maximal mechanical strength and resistance to fibrinolysis, whereas, rFXIII-A2 enhanced clot development,maximal mechanical strength and markedly enhanced resistance to fibrinolysis. These data illustrate that rFVIIa and rFXIII-A2 contribute to clot formation and stability by different mechanisms suggesting enhanced haemostatic efficacy by combining these agents.

Use of recombinant factor VIIa in the treatment of massive retroperitoneal bleeding due to severe necrotizing pancreatitis

Background. Recently, a growing number of case reports and case series have suggested that the use of recombinant activated factor VII (rFVIIa) may be effective in treatment of patients with non-hemophilic acquired coagulopathy not responding to conventional treatment such as major surgery, major trauma, sepsis, necrotizing pancreatitis and bleeding due to cerebral arteriovenous malformations. Case report. We presented a septic patient with massive, lifethreatening bleeding caused by retroperitoneal necrosis, due to severe acute necrotizing pancreatitis. As conservative treatment (blood, plasma, cryoprecipitates and platelet transfusions) failed to induce cessation of bleeding, the patient was urgently operated on. In spite of usual procedures of surgical hemostasis (ligation, suture, thermocauterisation, fibrin glue, temporary tamponade), hemorrhage could not be stopped. The patient manifested the signs of hypothermia and metabolic acidosis and, therefore, the decision was made to use recombinant activated factor VII (Novo Seven?). The application of rFVIIa resulted in significant discontinuation of hemorrhage, restoration to normal blood count as well as other relevant coagulation parameters. Conclusion. Although application of rFVIIa is still in the initial clinical phase, and the experience is based mainly on uncontrolled series as well as on individual observations, it seems that this drug can be promising, potent and attractive adjunctive prohemostatic agent. This drug may play a beneficial role in the treatment of serious and unresponsive, 'nonsurgical', life-threatening bleeding due to severe acute necrotizing pancreatitis.

The glycoprotein Ib-IX-V complex contributes to tissue factor–independent thrombin generation by recombinant factor VIIa on the activated platelet surface

Several lines of evidence suggest that recombinant factor VIIa (rFVIIa) is able to activate factor X on an activated platelet, in a tissue factor-independent manner. We hypothesized that, besides the anionic surface, a receptor on the activated platelet surface is involved in this process. Here, we showed that, in an ELISA setup, a purified extracellular fragment of GPIbα bound to immobilized rFVIIa. Surface plasmon resonance established a affinity constant (Kd) of approximately 20 nM for this interaction. In addition, CHO cells transfected with the GPIb-IX-V complex could adhere to immobilized rFVIIa, whereas wild-type CHO cells could not. Furthermore, platelets sti-mulated with a combination of collagen and thrombin adhered to immobilized rFVIIa under static conditions. Platelet adhesion was inhibited by treatment with O-sialoglycoprotein endopeptidase, which specifically cleaves GPIbα from the platelet surface. In addition, rFVIIa-mediated thrombin generation on the activated platelet surface was inhibited by cleaving GPIbα from its surface. In summary, 3 lines of evidence showed that rFVIIa interacts with the GPIb-IX-V complex, and this interaction enhanced tissue factor-independent thrombin generation mediated by rFVIIa on the activated platelet surface. The rFVIIa-GPIbα interaction could contribute to cessation of bleeding after administration of rFVIIa to patients with bleeding disorders.

Recombinant activated factor VII (rFVIIa) treatment in infants with hemorrhage

BACKGROUND

Recombinant activated factor VII (rFVIIa) is approved by the FDA for the treatment of bleeding episodes in patients with hemophilia A or B with inhibitors to factor VIII or factor IX. In addition to the FDA-approved indications, rFVIIa has been anecdotally reported effective for profound bleeding episodes in adult patients without hemophilia, and proven beneficial for adults with intracranial hemorrhage. In the pediatric literature, case reports have been made with apparent clinical improvement seen after the use of rFVIIa for acute life-threatening bleeding; however, there are limited data regarding its use in infants<4 months of age. We report our experience with rFVIIa in nine infants with severe hemorrhage of diverse etiologies.

METHODS

This case series of infants under 4 months with coagulopathy and bleeding treated with rFVIIa was collected from two institutions. We report the age, weight and pre-rFVIIa laboratory values of the patients as well as the clinical scenario and outcomes.

RESULTS

The nine infants all suffered acute life-threatening hemorrhage. Two patients were postoperative from cardiac surgery, two with Vitamin K deficiency and intracranial hemorrhage, three with suspected necrotizing enterocolitis and abdominal hemorrhage, and two with pulmonary hemorrhage. The patients ranged in age from 2 days to 4 months, (average age 1 month and average weight 3.3+/-1.0 kg). Seven of the nine patients had frozen plasma, cryoprecipitate, or platelet administration in failed attempts to correct the coagulation defect prior to receiving rFVIIa. The dose range used in this series was 90-100 microg.kg-1, with 90 microg.kg-1 being the most commonly used dose. The average pre-rFVIIa INR was 8.7+/-5.1. Four patients had an immeasurably high INR. All patients had clinical resolution of bleeding after receiving rFVIIa, and seven of nine patients survived.

CONCLUSIONS

rFVIIa is a powerful hemostatic drug whose mechanism of action provides a theoretical specificity to sites of tissue injury. In addition to its FDA-approved uses in hemophiliac patients, this drug has a potential role in the treatment of life-threatening hemorrhage from multiple causes.

Models of blood coagulation

Our research aims to provide quantitatively transparent, biologically realistic descriptions of the processes involved in hemostasis which will permit predictions of the behavior of the coagulation system in normal and pathologic states. We use four models of coagulation: (1) numerical approximations of the tissue factor (Tf) pathway of thrombin generation based upon mechanism and dynamics; (2) Tf activation of the "blood coagulation proteome" from isolated cells and proteins; (3) Tf activated contact pathway inhibited whole blood in vitro; and (4) blood shed from standardized microvascular wounds in vivo. The results from these models are integrated in interactive assessments aimed at achieving convergence of biochemical rigor and biological authenticity. Microvascular injury is the most biologically secure but least accessible to mechanistic study. Numerical models while quantitatively transparent are biologically limited. By the integrated analyses of all four models, we establish observations which require inclusion or discovery of new parameters to achieve mechanistically interpretable biological reality. Discoveries made in this fashion have included thrombin's role in the initiation phase, TFPI/ATIII/APC synergy interactions, rfVIIa in fVII deficiency, the roles of fVIII and fIX in the Tf reaction, and the cleavage of fIX by fXa membrane. Ideally, our results will provide descriptions which predict the behavior of the biological blood coagulation system under normal and pathologic conditions.

High dose factor VIIa improves clot structure and stability in a model of haemophilia B

Factor IX (FIX) deficiency results in haemophilia B and high dose recombinant activated factor VII (rFVIIa) can decrease bleeding. Previously, we showed that FIX deficiency results in a reduced rate and peak of thrombin generation. We have now used plasma and an in vitro coagulation model to examine the effect of these changes in thrombin generation on fibrin clot structure and stability. Low FIX delayed the clot formation onset and reduced the fibrin polymerisation rate. Clots formed without FIX were composed of thicker fibrin fibres than normal. rFVIIa shortened the clot formation onset time and improved the fibre structure of haemophilic clots. We also examined clot formation in the presence of a fibrinolytic challenge by including tissue plasminogen activator or plasmin in the reaction milieu. In these assays, normal FIX levels supported clot formation; however, clots did not form in the absence of FIX. rFVIIa partially restored haemophilic clot formation. These results were independent of the effects of the thrombin-activatable fibrinolysis inhibitor. Our data suggest that rFVIIa enhances haemostasis in haemophiliacs by increasing the thrombin generation rate to both promote formation of a structurally normal clot and improve clot formation and stability at sites with high endogenous fibrinolytic activities.

Use of recombinant factor VIIa in patients with warfarin-associated intracranial hemorrhage

INTRODUCTION

Warfarin-associated intracranial hemorrhage (ICH) requires rapid normalization of clotting function. Current therapies are associated with significant complications and/or prolonged time to correction of coagulopathy. Recombinant factor VIIa (FVIIa) might allow faster and safer correction of coagulopathy.

METHODS

This article presents a retrospective chart review of all patients with warfarin-associated ICH treated in a neurology/neurosurgery intensive care unit over an 11-month period.

RESULTS

All patients were treated to rapidly reverse the warfarin effect. Fifteen patients received vitamin K and fresh frozen plasma (FFP) alone (FFP group). Twelve patients also received FVIIa (FVIIa group). The median times from presentation to an international normalization ratio (INR) of less than 1.3 were 32.2 and 8.8 hours in the FFP the FVIIa groups, respectively (p = 0.016). INR normalized slowly (at 110 and 130 hours, respectively) in two patients with end-stage renal failure who were given FVIIa, one of whom developed disseminated intravascular coagulation after three doses of FVIIa. No other complications occurred from FVIIa administration. One patient in the FFP group developed severe pulmonary edema.

CONCLUSION

FVIIa may be an effective adjunct to FFP in warfarin-related ICH, facilitating faster correction of INR and decreasing FFP requirements. A prospective, randomized trial is needed to confirm these preliminary findings and to determine whether there is a clinical benefit.

Mechanistic implications for the use and monitoring of recombinant activated factor VII in trauma

As interest in the use of activated recombinant factor VII (rFVIIa) in trauma grows, questions arise regarding how best to monitor rFVIIa therapy and when rFVIIa may be expected to improve hemostasis. Knowledge of the mechanisms of action may be combined with available data on laboratory monitoring and efficacy in various coagulopathic states in coming to clinically relevant conclusions. This review addresses the physiology of hemostasis, placing emphasis on how rFVIIa influences the process by both tissue factor dependent and tissue factor independent mechanisms. This is extended to a mechanistic consideration of how rFVIIa may function under acidotic, hypothermic, and hemodilutional and/or consumptive conditions of trauma related coagulopathy. When these considerations are viewed alongside the available clinical data, it becomes apparent that rFVIIa has potential to improve hemostasis during trauma coagulopathy, within limitations. Common laboratory procedures are discussed with reference to mechanisms of action of rFVIIa and the available clinical data. Although there is no single assay that can predict rFVIIa efficacy in trauma, the prothrombin time (PT) is recommended as a minimum. Although a shortened PT does not predict success, correction of PT into the normal range may be a better indicator. A nonresponding PT appears to indicate that rFVIIa alone will not lead to hemostasis, and that additional blood products and other measures must be applied. Once the patient is more stable, PT and thromboelastography are recommended.

New Perspectives in Hemophilia Treatment

A variety of factor concentrates are currently available for replacement therapy for patients with hemophilia. These differ by several parameters, including source (pooled from pooled blood vs recombinant), purity, pathogen inactivation, and by the presence or absence of extraneous proteins such as albumin. The choice of replacement product reflects both safety issues of pathogen transmission or inhibitor development, and personal preferences of the patient and the physician. In general, currently available products are viral pathogen-free, although there is debate about the risk of transmission of parvovirus B19 and prion pathogens. Because of this very small risk, recombinant factor is the treatment of choice in previously untreated patients. In addition, a subset of concentrates contain factor that is activated during manufacture, yielding activated products that can be used in the treatment of patients with inhibitors. Such activated products, especially recombinant factor VIIa (rFVIIa), have also acquired several off-label indications in the management of bleeding in non-hemophiliac patients. The management of hemophilia patients with inhibitors is an ongoing challenge. Immune tolerance induction using a desensitization technique is successful in up to 90% of patients with alloantibodies against factor VIII, with greatest success seen in patients with low titer inhibitors who are treated soon after detection of an alloantibody and in whom treatment includes administration of immunosuppression along with repeated infusions of high titer concentrates. Such therapy is less successful in patients with factor IX alloantibodies. Non-hemophiliac patients with acquired inhibitors represent a unique patient population that requires special management. These patients have a mortality rate that approaches 25% because of the association of acquired inhibitors with severe bleeding complications, occurrence in a largely elderly population, and the frequent presence of an underlying, often serious, primary medical condition. Treatment consists of immunosuppression with steroids, chemotherapy, or intravenous immunoglobulin. Recent studies using rituximab for selective B-cell depletion in these patients have been very promising, although prospective controlled studies have not yet been performed. Finally, although hemophilia A and B appear to be ideal diseases to target with gene therapy approaches, the promise of this therapy remains to be realized.

Factor VIIa replacement therapy in factor VII deficiency

Factor (F)VII deficiency is an autosomal recessive disorder for which a replacement therapy is not universally available; recombinant FVIIa has been utilized as a therapeutic substitute. As FVII competes with FVIIa for binding to tissue factor in initiating the extrinsic pathway of blood coagulation, a lower dose of FVIIa replacement in cross-reacting material-negative (CRM-) individuals can achieve hemostasis. Three coagulation models (computational, synthetic and in vitro whole blood) were used to predict the FVIIa levels needed to provide apparent hemostasis in a non-bleeding state. Our whole blood results show that a 'normalized' coagulation profile for FVII-deficient individuals has an initiation phase that ends at 5.8 +/- 0.5 min (clot time) and the propagation phase of thrombin generation (thrombin-antithrombin III) yields a maximum concentration of 380 +/- 29 nmol L(-1). When CRM- FVII-deficient subjects were infused with a prophylactic dose of 23 micro g kg(-1) of recombinant FVIIa, 6-8 h postinfusion resulted in a comparable normalized whole blood profile. This FVIIa concentration (0.3-0.7 nmol L(-1)/equivalent dose: 0.8-1.8 micro g kg(-1)) is approximately 1/10 that currently used in treating FVII-deficient individuals and suggests that therapies should be altered relative to the concentration of the FVII zymogen.

Factor VIIa for Correction of Traumatic Coagulopathy

INTRODUCTION

Activated factor VIIa (FVIIa) was developed to treat hemophiliacs with high-titer antibodies to factor VIII. FVIIa initiates thrombin formation by binding with exposed tissue factor. Anecdotal reports have described the utility of FVIIa in correcting coagulopathy from trauma, but no large series exists. We present our experience with 81 coagulopathic trauma patients treated using FVIIa in years 2001-2003, compared with "control" patients matched from the trauma registry from the same time period.

METHODS

Use of FVIIa was restricted to active hemorrhage with clinical coagulopathy. We recorded the cause of coagulopathy, dose of FVIIa administered, effect on clinical coagulation, pertinent laboratory values, length of stay, number and type of blood products administered, and patient outcome. For the same time period we also examined outcomes in coagulopathic patients who did not receive FVIIa.

RESULTS

Causes of coagulopathy were diverse, and included acute traumatic hemorrhage (46 patients), traumatic brain injury (20), warfarin use (9), congenital Factor VII deficiency (2), and other acquired hematologic defects (4). Coagulopathy was reversed in 61/81 cases (75%), with an associated reduction in PT from 19.6 to 10.8 (p=0.000018). 34 patients (42%) survived to hospital discharge (20/46 traumatic hemorrhage, 5/20 TBI, 4/9 on warfarin, 2/2 factor deficient, 3/4 other). Patients died from irreversible shock, multiple organ system failure, or traumatic brain injury. FVIIa patients had a higher mortality than coagulopathic controls matched by specific anatomic injuries, admission lactate value, and predicted probability of survival. Only a group identified by all three characteristics had a similar mortality to the FVIIa cohort, but the number of patients that could be matched this way was too small to be meaningful.

CONCLUSION

FVIIa therapy lead to an immediate reduction in coagulopathic hemorrhage in most cases, accompanied by a significant improvement in laboratory measures. Application of FVIIa as a therapy of last resort makes the identification of equivalent control patients difficult. Use of FVIIa should be considered for any patient with coagulopathic hemorrhage in which surgically-accessible bleeding has been controlled. Prospective trials of FVIIa in patients with traumatic coagulopathy are strongly indicated, and should focus on appropriate patient selection and the dose and timing of therapy.

The use of recombinant factor VIIa in the treatment of bleeding disorders

Recombinant factor VIIa was initially developed for the treatment of hemorrhagic episodes in hemophilic patients with inhibitors to factors VIII and IX. After its introduction, it has also been used "off-label" to enhance hemostasis in nonhemophilic patients who experience bleeding episodes not responsive to conventional therapy. Evidence so far indicates that the use of factor VIIa in hemophilic patients with inhibitors is both safe and effective. Anecdotal reports also suggest that the product is safe and effective in controlling bleeding in nonhemophilic patients. However, its use in these conditions has not been approved by the FDA, and conclusive evidence of its effectiveness from controlled clinical trials is not yet available. Several questions pertaining to the use of factor VIIa require further investigation, including the mechanism of action; the optimal dose; definitive indications; ultimate safety; and laboratory tests for monitoring therapy.

Prophylactic and therapeutic recombinant factor VIIa administration to patients with Glanzmann's thrombasthenia: results of an international survey

BACKGROUND

Antibodies to glycoprotein (GP) IIb-IIIa and/or HLA may render platelet transfusions ineffective to stop bleeding or to cover surgery in patients with Glanzmann's thrombasthenia (GT). Anecdotal reports suggest recombinant factor (rF)VIIa might be a therapeutic alternative in these situations.

OBJECTIVES

An international survey was conducted to evaluate further the efficacy and safety of rFVIIa in GT patients.

PATIENTS

We analyzed the use of rFVIIa during 34 surgical/invasive procedures and 108 bleeding episodes in 59 GT patients including 29 with current or previous antiplatelet antibodies, and 23 with a history of refractoriness to platelet transfusion.

RESULTS

rFVIIa was effective in 29 of the 31 evaluable procedures, and in 77 of the 103 evaluable bleeding episodes of which eight had a recurrence. A significantly higher success rate was observed in severe bleeding episodes when an arbitrarily defined 'optimal regimen' derived from the Canadian pilot study results (> or = 80 micro g kg(-1) rFVIIa/injection, dosing interval < or = 2.5 h, three or more doses before failure declaration) was used compared with other regimens (77%; 24/31 vs. 48%, 19/40; chi(2), P = 0.010). Patients given maintenance doses had significantly fewer recurrences within 48 h of bleed cessation compared with those not given any (Fisher's exact test, P = 0.022). One thromboembolic event and one blood clot in the ureter occurring in surgical patients following prolonged continuous infusion of high-dose rFVIIa and antifibrinolytic drug use have been previously reported.

CONCLUSION

rFVIIa seems a potential alternative to platelet transfusion in GT patients, particularly in those with antiplatelet antibodies and/or platelet refractoriness.

Use of recombinant factor VIIa in infants with severe coagulopathy

The risk of hemorrhage in infants with severe coagulopathies unresponsive to fresh frozen plasma (FFP) infusions may preclude therapeutic invasive interventional procedures. We describe the successful use of recombinant factor VIIa (rFVIIa) in two such infants, the first with cirrhosis requiring paracentesis and the second with necrotizing enterocolitis requiring laparotomy. This report reviews the current concepts on the mechanism of action of the drug rFVIIa and considers its expanded use in infants unresponsive to FFP replacement.

Recombinant activated factor VII for life-threatening pulmonary hemorrhage after pediatric cardiac surgery

OBJECTIVE

To report intractable life-threatening pulmonary hemorrhage after cardiac surgery in an infant who was treated successfully with recombinant activated factor VII (rFVIIa).

DESIGN

Descriptive case report.

SETTING

An 18-bed pediatric intensive care unit at a tertiary-care children's hospital.

PATIENT

A 10-wk-old child with acute life-threatening pulmonary hemorrhage after cardiac surgery.

INTERVENTIONS

General supportive intensive care.

MEASUREMENTS AND MAIN RESULTS

Care included mechanical ventilatory support, inotropic support, and concurrent treatment with blood products (packed cells, platelet concentrates, and plasma-derived products), as well as aprotinin and desmopressin to improve hemostasis. The addition of rFVIIa resulted in complete resolution of the hemorrhage.

CONCLUSIONS

rFVIIa should be considered as a possible novel therapeutic approach to be used as rescue therapy for patients presenting with massive life-threatening hemorrhage progressing into hemorrhagic shock. Further controlled trials to elucidate the safety of this treatment are warranted.

Successful treatment of acquired factor VIII deficiency in a child using activated factor VII concentrates: case report and review of the literature

Acquired factor VIII deficiency is a rare life-threatening disorder that should be suspected in individuals without a prior bleeding history who present with mucous membrane, muscle, and/or urinary tract bleeding. The authors describe a 5-year-old girl with epistaxis, intramuscular bleeding, and forearm compartment syndrome requiring emergent fasciotomy. Coagulation studies showed a factor VIII level of less than 1%. The prolonged activated partial thromboplastin time corrected immediately when mixed with normal plasma at a 1:1 ratio but became prolonged again following incubation at 37 degrees C. She was treated successfully with serial administrations of activated factor VII concentrates and immunosuppression with corticosteroids. Activated factor VII concentrates should be considered as an option for patients of all ages with acquired factor VIII deficiency.

Recombinant factor VIIa for control of hemorrhage: early experience in critically ill trauma patients

STUDY OBJECTIVE

To examine our institutional experience with recombinant Factor VIIa (rFVIIa) as a treatment for exsanguinating hemorrhage in critically ill trauma patients.

DESIGN

Retrospective case review.

SETTING

A specialized trauma and critical care hospital, serving as the quaternary referral center for trauma and surgical shock in the state of Maryland.

PATIENTS

All patients with diffuse coagulopathy and impending exsanguination, given rFVIIa in an effort to control life-threatening hemorrhage. Patients were in the intensive care unit (ICU) or operating room (OR) and included both acute admissions and late-stage patients with multiple organ system failure.

INTERVENTIONS

Patients of interest were those that had received rFVIIa.

MEASUREMENTS

Examination of medical records, including pharmacy data, laboratory results, and the institutional trauma registry.

MAIN RESULTS

Administration of rFVIIa contributed to successful control of hemorrhage in three of five patients. Failure in two patients was mostly likely due to overwhelming shock and acidosis.

CONCLUSIONS

Administration of rFVIIa shows promise in the treatment of exsanguinating hemorrhage. Prospective, controlled clinical trials of this therapy are strongly recommended.

Recombinant activated factor VII for coagulopathy in fulminant hepatic failure compared with conventional therapy

Severe coagulopathy in fulminant hepatic failure (FHF) is difficult to correct by conventional means. Recombinant activated factor VII (rFVIIa) is an antihemophilic factor that has shown promise in treating coagulopathy in liver disease. Our aim is to review our experience with rFVIIa in treating the coagulopathy of FHF and compare these results with those of conventional therapy. Fifteen patients with FHF who met King's College criteria for orthotopic liver transplantation were studied. All were ascertained from our liver disease registry. Eight consecutive patients were administered fresh frozen plasma (FFP) alone, whereas seven consecutive patients were administered FFP and rFVIIa (40 microg/kg intravenous bolus). The two groups, with similar demographic characteristics, were compared in terms of measured parameters of coagulopathy (prothrombin time and international normalized ratio), amount of plasma infused, development of anasarca, ability to undergo intracranial pressure (ICP) transducer placement, bleeding complications, ability to undergo transplantation, and survival. All patients administered rFVIIa (after a single dose) versus none administered FFP alone had temporary (2- to 6-hour) correction of coagulopathy (P <.0002). All patients administered rFVIIa versus 38% administered FFP alone were able to have an ICP transducer placed (P =.03). The rFVIIa group had less anasarca (P =.04). An equal number of patients underwent transplantation from each group, but overall survival was slightly better in the rFVIIa group (P =.04). Five of seven patients in the rFVIIa group were administered one or more subsequent doses of rFVIIa after placement of the ICP monitor (two patients, for additional procedures; three patients, prophylactically in the first 24 hours after ICP transducer placement) at the discretion of the attending physicians. We conclude that rFVIIa is effective in transiently correcting laboratory parameters of coagulopathy in patients with FHF. It facilitates the performance of invasive procedures and is associated with less frequent anasarca compared with conventional therapy. Our preliminary experience supports the need for further studies to define the optimal dosing, safety, and efficacy of rFVIIa in patients with FHF.