Long-term safety and feasibility of arteriovenous fistulae as vascular accesses in children with haemophilia: a prospective study

Prophylactic versus on-demand treatments for hemophilia: advantages and drawbacks

INTRODUCTION

Early long-term prophylaxis is the standard of care to prevent joint bleeding and chronic arthropathy in patients with severe hemophilia. Areas covered: Despite the obvious prophylaxis advantages upon the clinical outcomes, there are still several drawbacks to be addressed for the optimal patients' compliance. Frequency of treatment due to short half-life of conventional FVIII and FIX concentrates, difficult venous access, adherence to the prescribed therapy and costs may represent significant critical issues. The development of inhibitors also makes replacement therapy ineffective, preventing patients from receiving long-term prophylaxis. This paper will review these drawbacks and the tools to overcome these limitations, mainly thanks to the use of extended half-life products and the development of novel non-conventional therapeutic approaches. Expert commentary: The use of extended half-life products may help in reducing the burden of the frequent intravenous administration and in better tailoring an individualized prophylaxis. The development of novel therapeutic approaches, like the bi-specific antibody mimicking the coagulation function of FVIII or inhibition of anticoagulant proteins may facilitate prophylaxis treatment not only in patients with inhibitors, but also in severe hemophilia patients without inhibitors. Exciting opportunities are emerging for improving prophylaxis in hemophilia.

Arteriovenous shunts as venous access in children with haemophilia

INTRODUCTION

Venous access is essential in patients with haemophilia for administration of factor concentrates. Peripheral venipuncture may be challenging, particularly in young children or during immune tolerance induction (ITI). Central venous access devices (CVADs) carry a significant risk for complications. An alternative for venous access is peripheral arteriovenous shunts (AVSs), but there is sparse documentation in the literature. The aim of this study was to document our experience with AVS over 12 years in 27 boys with severe haemophilia.

METHODS

For AVS creation, a subcutaneous vein is connected end-to-side with an artery at the wrist (Cimino) or at the forearm (Gracz shunt). Factor concentrates were substituted as for intermediate size surgery. To prevent shunt occlusion, heparin (5 units/kg/h) was given during the first 3 days.

RESULTS

Indications for AVS creation were prophylaxis start (n = 20) and ITI (n = 7). Age at shunt insertion was median 1.5 years (minimum 8 months; maximum 11.7 years). Shunt maturation was achieved within a median of 3 weeks after surgery (1.5 weeks; 18 weeks). Age when home treatment was established was median 2.1 years (9 months; 11.7 years). Four patients required AVS revisions due to stenosis, but 26 of 27 patients (96%) achieved good long-term shunt function. There were few other complications.

CONCLUSION

Arteriovenous shunts provide a good alternative to CVAD and carry a lower risk of complications. AVSs allow earlier start of prophylaxis and home therapy with an improved quality of life for patients and families.

Renal diseases in haemophilic patients: pathogenesis and clinical management

Haemophilia A and B are genetic X-linked bleeding disorders, caused by mutations in genes encoding factors VIII and IX, respectively. Clinical manifestations of haemophilia are spontaneous haemorrhage or acute bleeding caused by minor trauma, resulting in severe functional consequences that can culminate in a debilitating arthropathy. Life expectancy and quality of life of patients with haemophilia have dramatically improved over the last years, mainly for new therapeutic options and the awareness to the risk of HCV and HIV infections. Different clinical problems arise from this important change in history of patients with haemophilia. In particular, ageing-related diseases, such as diabetes, hypertension and cancer, and chronic viral infections are emerging as new challenges in this patient population. Among the different types of chronic illnesses, renal diseases are of special interest as they involve some difficult management issues. In fact, decisions regarding adequate preventive strategies and viral infection treatment, the choice of the dialytic modality, placement of vascular access and prescription of dialytic treatments are particularly complicated, because only few data are available. In this review, we discuss the pathogenesis of renal damage in patients with haemophilia, especially in those with blood-transmitted viral infections, and the major issues about the management of renal diseases, including problems related to dialytic treatment and kidney transplantation, providing practical algorithms to guide the clinical decision-making process.

Past, present and future of hemophilia: a narrative review

Over the past forty years the availability of coagulation factor replacement therapy has greatly contributed to the improved care of people with hemophilia. Following the blood-borne viral infections in the late 1970s and early 1980, caused by coagulation factor concentrates manufactured using non-virally inactivated pooled plasma, the need for safer treatment became crucial to the hemophilia community. The introduction of virus inactivated plasma-derived coagulation factors and then of recombinant products has revolutionized the care of these people. These therapeutic weapons have improved their quality of life and that of their families and permitted home treatment, i.e., factor replacement therapy at regular intervals in order to prevent both bleeding and the resultant joint damage (i.e. primary prophylaxis). Accordingly, a near normal lifestyle and life-expectancy have been achieved. The main current problem in hemophilia is the onset of alloantibodies inactivating the infused coagulation factor, even though immune tolerance regimens based on long-term daily injections of large dosages of coagulation factors are able to eradicate inhibitors in approximately two-thirds of affected patients. In addition availability of products that bypass the intrinsic coagulation defects have dramatically improved the management of this complication. The major challenges of current treatment regimens, such the short half life of hemophilia therapeutics with need for frequent intravenous injections, encourage the current efforts to produce coagulation factors with more prolonged bioavailability. Finally, intensive research is devoted to gene transfer therapy, the only way to ultimately obtain cure in hemophilia.

Pharmacotherapy of haemophilia A

INTRODUCTION

Haemophilia A is due to factor VIII (FVIII) deficiency. The main treatment is replacement therapy with FVIII concentrates. However, these concentrates carried a high risk of blood-borne viral infections and still have a high risk of inducing anti-FVIII inhibitors.

AREAS COVERED

An overview of products available and therapeutic options for haemophilia A management in order to help in decision making. A literature search using Medline with the keywords: 'haemophilia', 'factor VIII', 'therapy', 'inhibitor', 'concentrate', 'bleeding', 'prophylaxis', 'on demand', 'plasma-derived', 'recombinant', 'coagulation factors', 'immunotolerance' was performed. The years 1960 - 2010 are included.

EXPERT OPINION

Progress in management of patients with haemophilia A has allowed increased life expectancy and quality of life. There is evidence that prophylaxis prevents or, at least, slows down arthropathy development when started early in childhood. FVIII concentrates have achieved high levels of blood-borne pathogen safety. However, treatment is frequently complicated by development of FVIII-neutralizing inhibitors, which prevent control of bleeding and predispose to a high morbidity and mortality risk. Bypassing agents are effective in bleeding treatment in a high percentage of cases. Prophylaxis with bypassing agents and their use in combination are offering opportunities in management of inhibitor patients. More evidence is necessary to understand how to prevent and manage this complication.

A randomized clinical trial of prophylaxis in children with hemophilia A (the ESPRIT Study)

BACKGROUND

Prevention of arthropathy is a major goal of hemophilia treatment. While studies in adults have demonstrated an impact of prophylaxis on the incidence of joint bleeds and patients' well-being in terms of improved quality of life (QoL), it is unclear whether or not prophylaxis influences the outcome and perception of well- of children with hemophilia.

OBJECTIVE

This randomized controlled study compared the efficacy of prophylaxis with episodic therapy in preventing hemarthroses and image-proven joint damage in children with severe hemophilia A (factor VIII <1%) over a 10-year time period.

METHODS

Forty-five children with severe hemophilia A, aged 1-7 years (median 4), with negative clinical-radiologic joint score at entry and at least one bleed during the previous 6 months, were consecutively randomized to prophylaxis with recombinant factor VIII (25 IU kg(-1) 3 × week) or episodic therapy with ≥25 IU kg(-1) every 12-24 h until complete clinical bleeding resolution. Safety, feasibility, direct costs and QoL were also evaluated.

RESULTS

Twenty-one children were assigned to prophylaxis, 19 to episodic treatment. Children on prophylaxis had fewer hemarthroses than children on episodic therapy: 0.20 vs. 0.52 events per patient per month (P < 0.02). Plain-film radiology showed signs of arthropathy in six patients on prophylaxis (29%) vs. 14 on episodic treatment (74%) (P < 0.05). Prophylaxis was more effective when started early (≤36 months), with patients having fewer joint bleeds (0.12 joint bleeds per patient per month) and no radiologic signs of arthropathy.

CONCLUSION

This randomized trial confirms the efficacy of prophylaxis in preventing bleeds and arthropathy in children with hemophilia, particularly when it is initiated early in life.

Venous access in haemophilic children: choice and management

Current haemophilia treatment in children is based on regular intravenous infusions of concentrates for prolonged periods, according to prophylaxis regimens or immune tolerance induction treatment, in cases of inhibitor development. Therefore, a stable and uncomplicated venous access is required and as such peripheral veins represent the preferred option. However, frequent infusions in the home setting can be problematic in very young children and for this reason, central venous access devices (CVADs) have been widely used to improve treatment feasibility. Unfortunately CVADs' use is associated with a high rate of complications, and infections and thrombotic occlusion can influence treatment outcome by causing unwanted treatment interruption. CVADs can be grouped into three main categories: external non-tunnelled, external tunnelled and fully implantable devices known as ports. The management of CVADs at home often represents a challenge because a strict adherence to sterile procedures is required. Indeed, the incidence of infections with ports is much lower than that reported for external devices; however, ports carry the inconvenience of needle sticks. More recently, arteriovenous fistula was shown to be a suitable alternative to CVADs because it is easy to use and is associated with a lower rate of complication.

Arteriovenous fistula as stable venous access in children with severe haemophilia

Treatment for children with severe haemophilia is based on prophylaxis and, if inhibitors occur, on immune tolerance induction (ITI). Both regimens require frequent infusions at early ages and therefore an adequate venous access is essential. Peripheral veins represent the best option; however, central venous catheters (CVCs) have been used to facilitate regular treatment. Unfortunately, survival of CVCs is affected by infectious and/or thrombotic complications that often lead to premature removal and consequent treatment discontinuation. This aspect may have an impact on treatment outcome, especially in the case of ITI. In light of this, internal arteriovenous fistula (AVF) has been proposed as an alternative option because of a lower rate of infectious complications. Moreover, AVF is easy to use in the home setting and is well accepted by children and parents. The possible complications are postoperative haematoma and transient symptoms of distal ischaemia; one case of symptomatic thrombosis has been reported to date. Other complications include loss of patency, aneurysmatic dilatation and limb dysmetria. A regular follow-up is mandatory to allow early remedial interventions. Surgical AVF dismantlement is recommended as soon as transition to peripheral vein access is possible.

Improved treatment feasibility in children with hemophilia using arteriovenous fistulae: the results after seven years of follow-up

BACKGROUND

An easy and stable venous access is essential in hemophilic children who receive regular prophylaxis or immune tolerance induction treatment. Central venous access devices improve treatment feasibility, but their use is complicated by infection and/or thrombosis. Arteriovenous fistula (AVF) has been evaluated as an alternative to central venous access devices in hemophilic children since 1999.

DESIGN AND METHODS

This study provides results obtained in a large series after seven years of follow-up.

RESULTS

From 1999 to 2008, 43 procedures were performed in 38 children (median age: 2.7 years). Thirty-five AVFs (81%) achieved maturation after a median of 58 days and were used for a median of five years (range: 0.4-8.5). A brachial artery caliber larger than 1.2 mm was associated with successful maturation (p<0.05). Complications with some impact on arteriovenous fistula use or duration were observed in 14/43 procedures (32%) and in 13/38 children (34%). Age at arteriovenous fistula creation was younger in children who lost arteriovenous fistula patency (p<0.05) and aneurysms were more frequent in children who were on daily treatment regimen and thus had a greater cumulative number of arteriovenous fistula accesses (p<0.05). At the end of the follow-up period, 22 AVFs were still in use and 9 had been surgically dismantled. Arteriovenous fistula use allowed long-term prophylaxis (up to 8.5 years) in 11 children and the completion of immune tolerance induction without interruptions in 18 children.

CONCLUSIONS

This study confirms the feasibility of arteriovenous fistula with an acceptable rate of complications and suggests that its use is particularly favorable in children with inhibitors in whom it should be considered as first-choice venous access.

Barriers to primary prophylaxis in haemophilic children: the issue of the venous access

Modem treatment for hemophilic children is based on prophylaxis and immune tolerance induction (ITI). Both treatment regimens are based on frequent infusions at early ages, therefore an adequate venous access is essential. Peripheral veins represent the best option, however, different solutions, as central venous access devices (CVADs) and arteriovenous fistulae (AVFs), can be adopted if needed. CVADs have been used in hemophiliacs, however their survival is affected by infectious complications. Among CVADs, fully implantable devices are usually preferred to external lines due to a lower infectious risk. The limited survival of CVADs may have a relevant impact on treatment outcome, especially in case of ITI where treatment interruptions are counterproductive. To overcome such drawbacks, internal AVF has been considered as an alternative option owing to a lower rate of infectious complications. Moreover, AVF is easy to use in the home setting and well accepted by children. Possible complications not preventing AVF use are postoperative hematoma and transient symptoms of distal ischemia; one case of symptomatic thrombosis has been reported so far. Long-term complications include loss of patency, aneurysmatic dilatation and, rarely, limb dysmetria and a regular follow-up is mandatory to allow early remedial intervention. Surgical dismantlement of AVF is recommended as soon as transition to peripheral veins is possible.

Forum on: the role of recombinant factor VIII in children with severe haemophilia A

The development of recombinant FVIII (rFVIII) products, fuelled by the need for improved safety of treatment arising from the dramatic widespread blood-borne virus transmission in the 1970-1980s revolutionized the care of children with haemophilia A over the last two decades. The larger availability of perceived safer replacement therapy associated with the introduction of rFVIII products reassured the haemophilia community and there was a strong push in some Western countries to treat haemophilic children only with rFVIII. Moreover, this significantly contributed in the 1990s to the diffusion outside Northern Europe of prophylactic regimens implemented at an early age to prevent bleeding and the resultant joint damage (i.e. primary prophylaxis), together with the possibility of home treatment. These changes led to a substantial improvement of the quality of life of haemophilic children and of their families. The general agreement that primary prophylaxis represents the first-choice treatment for haemophilic children has been recently supported by two randomized controlled trials carried out with rFVIII products, providing evidence on the efficacy of early prophylaxis over on-demand treatment in preserving joint health in haemophilic children. However, the intensity and optimal modalities of implementation of prophylaxis in children, in particular with respect to the issue of the venous access, are still debated. A number of studies also supports the role of secondary prophylaxis in children, frequently used in countries in which primary prophylaxis was introduced more recently. With viral safety now less than an issue and with the more widespread use of prophylaxis able to prevent arthropathy, the most challenging complication of replacement therapy for children with haemophilia remains the risk of inhibitor development. Despite conflicting data, there is no evidence that the type of FVIII concentrate significantly influences the complex multifactorial process leading to anti-FVIII alloantibodies, whereas other treatment-related factors are likely to increase (early intensive treatments due to surgery or severe bleeds) or reduce (prophylaxis) the risk. Although the optimal regimen is still uncertain, eradication of anti-FVIII antibodies by immune tolerance induction (ITI), usually with the same product administered at inhibitor detection, should be the first-choice treatment for all patients with recent onset inhibitors. This issue applies particularly to children, as most patients undergo ITI at an early age, when inhibitors usually appear. The availability of a stable and long-lasting venous access represents a leading problem also in this setting. These and other topics concerning rFVIII treatment of haemophilic children were discussed in a meeting held in Rome on 27 February 2008 and are summarized in this report.

Therapeutic use of arteriovenous fistula in children with haemophilia

Haemophilia is an X-linked inherited bleeding disorder, which only affects males. Contemporary treatment of children with haemophilia requires adequate venous access for the administration of prophylactic therapy which commences as a relatively early age. In the majority of children this treatment is administered at home, usually by the parents and then, once competent, by the boys themselves. As venous access in young children is fraught with difficulty, central venous access devices have become the mainstay of haemophilia care. However, these devices come with their own difficulties, with infection and thrombosis causing significant side-effects in some children. Small but substantial cohorts of boys with haemophilia develop antibodies (or inhibitors) to coagulation factors, rendering them both more likely to experience bleeding and more complex to treat. These boys are, for reasons not yet fully understood, more likely to experience central line infections, which also affect overall treatment outcomes. Arteriovenous fistulae were used in four such boys in an attempt to eliminate central line infection and to enable continued treatment administration. The experience and outcomes of these four boys is discussed along with considerations and implications for nurses caring for them.

Prevention of haemophilic synovitis: prophylaxis

It has been proven that early prophylactic therapy can prevent bleeding and arthropathy. Numerous retrospective non-randomized cohort studies have demonstrated that prophylaxis, if started early in life, is associated with a considerable reduction of the mean number of joint bleeds and the rate of joint deterioration. It is quite extraordinary that despite the considerable evidence base it has been considered necessary by investigators to pursue the ideal of the controlled randomized trial and expose children to the risk of cerebral bleed. This questionable ethical approach is driven by the reluctance of the 'willingness to pay' but it is important that patients are not subjected to unnecessary investigation at either the behest of the Cochrane Database or those who control the financing of haemophilia care.

Overview of the use of implantable venous access devices in the management of children with inherited bleeding disorders

Frequent infusion of factor concentrates may be challenging in young boys with haemophilia, especially if their disease is complicated by inhibitors. A central venous access device (CVAD) is often placed in young patients in need of repeated infusions for prophylaxis or immune tolerance induction. Although user friendly and capable of providing reliable venous access, these devices are associated with a high complication rate over time. In the haemophilia population, major complications include CVAD-associated infections and deep venous thrombosis, which is most often silent. Established risk factors for catheter-related infection include age less than 6 years at the time of CVAD placement and use of an external CVAD when compared with a totally implantable device such as a port. Avoidance of CVAD-related infections is facilitated by strict adherence to aseptic technique. The risk of deep venous thrombosis appears related to the duration for which the catheter is in place, with the risk increasing beyond 4 years. The promotion of a strict clinic policy in which CVADs are left in place for as short a time as possible should decrease the risk of complications. In rare cases where a totally implantable CVAD cannot be placed for technical reasons, an arteriovenous fistula may provide reliable venous access. In all cases, however, venous access via peripheral veins is preferred over CVADs.

International workshop on immune tolerance induction: consensus recommendations

Although immune tolerance induction (ITI) has been used for 30 years to eliminate inhibitors and restore normal factor pharmacokinetics in patients with hemophilia, there is a paucity of scientific evidence to guide therapeutic decision-making. In an effort to provide direction for physicians and hemophilia treatment center staff members, an international panel of hemophilia opinion leaders met to develop consensus recommendations for ITI in patients with severe and mild hemophilia A and hemophilia B. These recommendations draw on the available published literature and the collective clinical experience of the group and are rated based on the level of supporting evidence.

Immune tolerance therapy for factor VIII inhibitors: moving from empiricism to an evidence-based approach

Currently, the only proven strategy for achieving antigen-specific tolerance to factor VIII (FVIII) is immune tolerance induction (ITI) therapy. This paper discusses our current knowledge of the host and treatment factors, as well as supportive care initiatives, known or suspected to influence the outcome of ITI in the treatment of inhibitors arising in patients with severe hemophilia A. Among these, questions surrounding the choice of therapeutic product and/or dosing regimen generate the most controversy, given the lack of a definitive evidence-based approach to either. Furthermore, the potential for central venous access device (CVAD) and intercurrent bleeding complications to impact the ultimate success of ITI remains unclear. The ongoing clinical trials designed to further clarify several of these polarizing issues are reviewed. This paper also explores the current and future role of immune modulation in possible salvage, ancillary or primary alternative tolerance induction strategies. The special cases of low titer/ responding inhibitors and inhibitors developing in mild hemophilia A patients are considered. Finally, this paper summarizes the currently recommended approach to ITI and makes the case for a move from empiric therapeutics to a risk-stratified evidence-based approach to FVIII inhibitor eradication.

Arteriovenous fistula for long-term venous access for boys with hemophilia

OBJECTIVES

Hemophilia is a sex-linked condition affecting about 1 of every 5000 males in the United States. The management of children with hemophilia can be improved with regular intravenous infusion of factor VIII or IX, thus preventing crippling and sometimes fatal hemorrhage. Maintaining this vital intravenous access is often hampered by gradual loss of superficial veins or repeated central catheter sepsis and thrombosis. This study reviewed an experience with arteriovenous fistula in selected hemophilia patients with limited venous access.

METHODS

Consecutive patients operated on between October 2000 and July 2006 for venous access with the creation of an arteriovenous fistula were reviewed. They were selected because of repeated problems with other venous access. Patency, ease of use, duplex scan derived brachial artery diameter, and arm length were assessed.

RESULTS

During a 69-month period, 10 arteriovenous fistulas (five brachial artery-basilic vein fistulas, 5 brachial artery-cephalic vein fistulas) were created for nine patients. The patients were a median age of 5.5 years (range, 1 to 27 years), and all were <13 except the 27-year-old patient. There were no postoperative hematomas requiring evacuation. One arteriovenous fistula failed to mature and was redone in the opposite arm, which subsequently occluded after 13 months. Of the mature fistulas, patency was 100% at 1 year, 80% (4/5) at 3 years, and 75% (3/4) at 4 years, with mean follow-up of 22 months. Brachial artery diameter increased in the involved arm by a ratio of 1.95 (range, 1.51 to 2.5) compared with the opposite arm. Arm length disparity was increased by 0.5 cm (range, 0.8 to 1.5 cm) in the involved arm. All fistulas allowed good access at home by a care provider.

CONCLUSIONS

For hemophilia patients with compromised venous access, arteriovenous fistulas provide good early patency. Brachial artery diameter and arm length require continued follow-up.

Hemophilia management: optimizing treatment based on patient needs

PURPOSE OF REVIEW

Progress in hemophilia management over the past year has focused on improving understanding of the most common complications of genetic bleeding disorders and building upon available therapeutic strategies.

RECENT FINDINGS

Research continued to link factor VIII structure with immune recognition and inhibitor formation. Clinical regimens of immune tolerance induction confirmed and expanded basic understanding. Barriers to optimal prevention using prophylaxis were explored allowing future refinements to address unmet needs. Outcome tools to assess joint health and overall quality of life were developed and validated. The inclusion of standardized instruments in assessment of outcome will allow meaningful comparison of available therapies. Use and complications of central venous access devices (CVAD), needed to deliver aggressive infusion regimens, were exhaustively reviewed. Finally, continued progress was achieved in development of improved vectors for future gene therapy of the hemophilias.

SUMMARY

A general theme of recent progress in hemophilia management is harmonization in definitions and assessments of complications and outcomes, facilitating more rigorous and ultimately more useful interpretation of laboratory and clinical research.

Optimizing factor prophylaxis for the haemophilia population: where do we stand?

The hallmark of severe haemophilia, defined as a circulating level of factor (F) VIII (haemophilia A cases) or FIX (haemophilia B cases) of < 1%, is recurrent bleeding into muscles and joints (haemarthroses) from an early age of life. The inevitable result of such bleeding is progressive joint damage, leading to disabling arthritis that is typically evident within the first 2 decades of life in people with haemophilia who have limited or no access to regular factor replacement therapy, or those in whom factor replacement therapy is ineffective because of the presence of high-titre inhibitors. For children with severe haemophilia and no evidence of inhibitors, the unwanted musculoskeletal complications of severe haemophilia can be effectively prevented by the early initiation of a programme of long-term factor prophylaxis. In order to achieve the best outcome (a perfect musculoskeletal status for age) the programme of prophylaxis should be started before the onset of joint damage (primary prophylaxis). The gold standard primary prophylaxis regimen (the Malmo protocol) was pioneered and tested in Sweden and involves the infusion of 20-40 IU of FVIII per kg body weight on alternate days (minimum three times per week) for haemophilia A cases, and 20-40 IU kg(-1) of FIX twice weekly for haemophilia B cases. This protocol is, however, demanding on peripheral veins and very expensive. Modifications of the parent protocol such as starting primary prophylaxis with once-weekly infusions via peripheral veins with rapid escalation to full-dose prophylaxis or dose escalation based on frequency of bleeding are increasingly implemented in haemophilia treatment centres in countries that can afford the high cost of such programmes. These modified programmes can be achieved in the majority of young children with severe haemophilia without the need for central venous access devices (e.g. Port-a-Caths) and with avoidance of device-associated complications such as infection and thrombosis. In at least one centre, experience with arteriovenous fistulae as a strategy to ensure reliable venous access is being accumulated. The issues of compliance (adherence) to recommended prophylaxis protocols and when, if ever, to stop a programme of primary prophylaxis once started are real and require ongoing prospective studies. Such studies should incorporate outcome measures such as health-related quality-of-life and economic analyses.