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

Allo-Hemodialysis, a Novel Dialytic Treatment Option for Patients with Kidney Failure: Outcomes of Mathematical Modelling, Prototyping, and Ex Vivo Testing

It has been estimated that in 2010, over two million patients with end-stage kidney disease may have faced premature death due to a lack of access to affordable renal replacement therapy, mostly dialysis. To address this shortfall in dialytic kidney replacement therapy, we propose a novel, cost-effective, and low-complexity hemodialysis method called allo-hemodialysis (alloHD). With alloHD, instead of conventional hemodialysis, the blood of a patient with kidney failure flows through the dialyzer's dialysate compartment counter-currently to the blood of a healthy subject (referred to as a "buddy") flowing through the blood compartment. Along the concentration and hydrostatic pressure gradients, uremic solutes and excess fluid are transferred from the patient to the buddy and subsequently excreted by the healthy kidneys of the buddy. We developed a mathematical model of alloHD to systematically explore dialysis adequacy in terms of weekly standard urea Kt/V. We showed that in the case of an anuric child (20 kg), four 4 h alloHD sessions are sufficient to attain a weekly standard Kt/V of >2.0. In the case of an anuric adult patient (70 kg), six 4 h alloHD sessions are necessary. As a next step, we designed and built an alloHD machine prototype that comprises off-the-shelf components. We then used this prototype to perform ex vivo experiments to investigate the transport of solutes, including urea, creatinine, and protein-bound uremic retention products, and to quantitate the accuracy and precision of the machine's ultrafiltration control. These experiments showed that alloHD performed as expected, encouraging future in vivo studies in animals with and without kidney failure.

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.

Central venous access device (CVAD) complications in Haemophilia with inhibitors undergoing immune tolerance induction: Lessons from the international immune tolerance study

INTRODUCTION

Central venous access devices (CVADs) are frequently required as stable long-lasting venous access in children with haemophilia, especially those requiring immune tolerance induction (ITI) for inhibitors. CVAD infection is one of the most frequently reported catheter-related complications in this patient population.

AIM

Detailed review of CVAD complications from the International ITI (I-ITI) study and analysis of potential risk factors for such complications.

METHODS

Retrospective analysis of prospectively obtained data from the I-ITI study primarily focused on CVAD-related complications.

RESULTS

A total of 115 children were recruited and 183 CVADs were placed in 99 subjects resulting in 121,206 CVAD-days observed on-study. A total of 124 CVAD infections were reported in 41 of 99 (41%) subjects with an overall infection rate of 0.94 per 1000 CVAD-days (interquartile ranges 0-1.7). A similar number of infections were observed in the two treatment arms (median: 2 and 3 in high dose and low dose respectively). Infections occurred more frequently in the presence of external catheters than with fully implanted catheters (P = 0.026). Infected patients were significantly younger at the time of CVAD insertion (median age: 22 vs. 25 months, P = 0.020). Patients with Gram-positive infections were also significantly younger than those with Gram-negative infections (median age: 17 vs. 25 months, P < 0.0001).

CONCLUSION

CVAD infection was the most common complication observed in children with severe haemophilia and inhibitors in the frame of the I-ITI study. Younger age at CVAD insertion and external CVAD were associated with higher risk for infection. ITI outcome was unaffected by CVAD infections.

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.

Treatment of hemophilia: a review of current advances and ongoing issues

Replacement of the congenitally deficient factor VIII or IX through plasma-derived or recombinant concentrates is the mainstay of treatment for hemophilia. Concentrate infusions when hemorrhages occur typically in joint and muscles (on-demand treatment) is able to resolve bleeding, but does not prevent the progressive joint deterioration leading to crippling hemophilic arthropathy. Therefore, primary prophylaxis, ie, regular infusion of concentrates started after the first joint bleed and/or before the age of two years, is now recognized as first-line treatment in children with severe hemophilia. Secondary prophylaxis, whenever started, aims to avoid (or delay) the progression of arthropathy and improve patient quality of life. Interestingly, recent data suggest a role for early prophylaxis also in preventing development of inhibitors, the most serious complication of treatment in hemophilia, in which multiple genetic and environmental factors may be involved. Treatment of bleeds in patients with inhibitors requires bypassing agents (activated prothrombin complex concentrates, recombinant factor VIIa). However, eradication of inhibitors by induction of immune tolerance should be the first choice for patients with recent onset inhibitors. The wide availability of safe factor concentrates and programs for comprehensive care has now resulted in highly satisfactory treatment of hemophilia patients in developed countries. Unfortunately, this is not true for more than two-thirds of persons with hemophilia, who live in developing countries.

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.