Central venous catheter-associated thrombosis in severe haemophilia

Low molecular weight heparin for prevention of central venous catheter-related thrombosis in children

BACKGROUND

The prevalence of children diagnosed with thrombotic events has been increasing in the last decades. The most common thrombosis risk factor in neonates, infants and children is the placement of a central venous catheter (CVC). It is unknown if anticoagulation prophylaxis with low molecular weight heparin (LMWH) decreases CVC-related thrombosis in children. This is an update of the Cochrane Review published in 2014.

OBJECTIVES

To determine the effect of LMWH prophylaxis on the incidence of CVC-related thrombosis and major and minor bleeding complications in children. Further objectives were to determine the effect of LMWH on occlusion of CVCs, number of days of CVC patency, episodes of catheter-related bloodstream infection (CRBSI), other side effects of LMWH (allergic reactions, abnormal coagulation profile, heparin-induced thrombocytopaenia and osteoporosis) and mortality during therapy.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase and CINAHL databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 7 May 2019. We undertook reference checking of identified trials to identify additional studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and quasi-randomised trials comparing LMWH to no prophylaxis (placebo or no treatment), or low-dose unfractionated heparin (UFH) either as continuous infusion or flushes (low-dose UFH aims to ensure the patency of the central line but has no systemic anticoagulation activity), given to prevent CVC-related thrombotic events in children. We selected studies conducted in children aged 0 to 18 years.

DATA COLLECTION AND ANALYSIS

Two review authors independently identified eligible studies, which were assessed for study methodology including bias, and extracted unadjusted data where available. In the data analysis step, all outcomes were analysed as binary or dichotomous outcomes. The effects of interventions were summarised with risk ratios (RR) and their respective 95% confidence intervals (CI). We assessed the certainty of evidence for each outcome using the GRADE approach.

MAIN RESULTS

One additional study was included for this update bringing the total to two included studies (with 1135 participants). Both studies were open-label RCTs comparing LMWH with low-dose UFH to prevent CVC-related thrombosis in children. We identified no studies comparing LMWH with placebo or no treatment. Meta-analysis found insufficient evidence of an effect of LMWH prophylaxis in reducing the incidence of CVC-related thrombosis in children with CVC, compared to low-dose UFH (RR 0.68, 95% CI 0.27 to 1.75; 2 studies; 787 participants; low-certainty evidence). One study (158 participants) reported symptomatic and asymptomatic CVC-related thrombosis separately and detected no evidence of a difference between LMWH and low-dose UFH (RR 1.03, 95% CI 0.21 to 4.93; low-certainty evidence; RR 1.17, 95% CI 0.45 to 3.08; low-certainty evidence; for symptomatic and asymptomatic participants respectively). There was insufficient evidence to determine whether LMWH impacts the risk of major bleeding (RR 0.27, 95% CI 0.05 to 1.67; 2 studies; 813 participants; low-certainty evidence); or minor bleeding. One study reported minor bleeding in 53.3% of participants in the LMWH arm and in 44.7% of participants in the low-dose UFH arm (RR 1.20, 95% CI 0.91 to 1.58; 1 study; 158 participants; very low-certainty evidence), and the other study reported no minor bleeding in either group (RR: not estimable). Mortality during the study period was reported in one study, where two deaths occurred during the study period. Both were unrelated to thrombotic events and occurred in the low-dose UFH arm. The second study did not report mortality during therapy per arm but showed similar 5-year overall survival (low-certainty evidence). No additional adverse effects were reported. Other pre-specified outcomes (including CVC occlusion, patency and CRBSI) were not reported.

AUTHORS' CONCLUSIONS

Pooling data from two RCTs did not provide evidence to support the use of prophylactic LWMH for preventing CVC-related thrombosis in children (low-certainty evidence). Evidence was also insufficient to confirm or exclude a difference in the incidence of major and minor bleeding complications in the LMWH prophylaxis group compared to low-dose UFH (low and very low certainty respectively). No evidence of a clear difference in overall mortality was seen. Studies did not report on the outcomes catheter occlusion, days of catheter patency, episodes of CRBSI and other side effects of LMWH (allergic reactions, abnormal coagulation profile, heparin-induced thrombocytopaenia and osteoporosis). The certainty of the evidence was downgraded due to risk of bias of the included studies, imprecision and inconsistency, preventing conclusions in regards to the efficacy of LMWH prophylaxis to prevent CVC-related thrombosis in children.

Anticoagulation beyond direct thrombin and factor Xa inhibitors: indications for targeting the intrinsic pathway?

Antithrombotic drugs like vitamin K antagonists and heparin have been the gold standard for the treatment and prevention of thromboembolic disease for many years. Unfortunately, there are several disadvantages of these antithrombotic drugs: they are accompanied by serious bleeding problems, it is necessary to monitor the therapeutic window, and there are various interactions with food and other drugs. This has led to the development of new oral anticoagulants, specifically inhibiting either thrombin or factor Xa. In terms of effectiveness, these drugs are comparable to the currently available anticoagulants; however, they are still associated with issues such as bleeding, reversal of the drug and complicated laboratory monitoring. Vitamin K antagonists, heparin, direct thrombin and factor Xa inhibitors have in common that they target key proteins of the haemostatic system. In an attempt to overcome these difficulties we investigated whether the intrinsic coagulation factors (VIII, IX, XI, XII, prekallikrein and high-molecular-weight kininogen) are superior targets for anticoagulation. We analysed epidemiological data concerning thrombosis and bleeding in patients deficient in one of the intrinsic pathway proteins. Furthermore, we discuss several thrombotic models in intrinsic coagulation factor-deficient animals. The combined results suggest that intrinsic coagulation factors could be suitable targets for anticoagulant drugs.

Low molecular weight heparin for prevention of central venous catheterization-related thrombosis in children

BACKGROUND

The prevalence of children diagnosed with deep vein thrombosis or pulmonary embolism has been increasing in the last decade. The most common thrombosis risk factor in neonates, infants and children is the placement of a central venous catheter (CVC). To date, it is unknown if the practice of anticoagulation prophylaxis with low molecular weight heparin (LMWH) decreases CVC-related thrombosis in children.

OBJECTIVES

The primary objective of this review was to determine the effect of LMWH prophylaxis on reducing the incidence of CVC-related thrombosis in children.Secondary objectives were to determine the effect of LMWH on occlusion of CVCs, number of days of CVC patency, episodes of catheter-related sepsis, side effects of LMWH (allergic reactions, major and minor bleeding complications, abnormal coagulation profile, osteoporosis) and mortality during therapy.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched June 2013), CENTRAL (2013, Issue 5) and clinical trial databases. The authors searched MEDLINE and EMBASE (July 2013). Bibliographies of identified articles were searched. There were no language restrictions.

SELECTION CRITERIA

Randomised and quasi-randomised trials comparing LMWH prophylaxis to standard care given to prevent CVC-related thrombotic events in children were included. We selected studies conducted in children aged 0 to 18 years.

DATA COLLECTION AND ANALYSIS

Two review authors independently identified eligible studies, which were assessed for study quality including bias, and extracted unadjusted data where available. In the data analysis step, all outcomes were analysed as binary or dichotomous outcomes. The effects of interventions were summarised with risk ratios (RR) and their respective 95% confidence intervals (CI).

MAIN RESULTS

One of 17 studies retrieved for full-text assessment for eligibility was included in the final analysis. This study included a total of 186 participants and investigated the effect of LMWH to prevent CVC-related thrombosis compared to standard care. The risk of bias of the study was assessed to be low, except for the unclear risk of selection bias (allocation concealment not reported) and detection bias since it was an open-label study. Nonetheless, outcome adjudication was blinded. However, overall the quality of the evidence was low due to the fact that the study was underpowered. The CIs for the risk of CVC-related thrombosis (symptomatic and asymptomatic events) were compatible with benefits of either LMWH (reviparin) or the control (RR for symptomatic thrombosis 1.03, 95% CI 0.21 to 4.93; RR for asymptomatic thrombosis 1.17, 95% CI 0.45 to 3.08). Similarly, only one patient in the standard care group suffered a major bleeding event, while minor bleeding was found in 53.3% of patients in the reviparin arm and in 44.7% of patients in the standard care arm (major bleeding RR 0.34, 95% CI 0.01 to 8.26; minor bleeding RR 1.20, 95% CI 0.91 to 1.58). Lastly, there were two deaths within the study and neither were the result of a venous thrombotic event (VTE), occurring in the standard care arm. No additional adverse effects were reported. Other pre-specified outcomes for this review were not reported.

AUTHORS' CONCLUSIONS

A single study reported imprecise effects for the risk of CVC-related thrombosis in children on a CVC anticoagulant prophylaxis regimen. The quality of the evidence was low due to the fact that the included study was clearly underpowered, hampering any conclusions in regards to the efficacy of LMWH prophylaxis to prevent CVC-related thrombi in children. Further prospective randomised studies are highly encouraged.

Central venous access devices in patients with hemophilia

Hemophilia is a hereditary disorder in which the major clinical manifestation is bleeding into the joints, muscles, internal organs and the CNS, often without any obvious trauma. Bleeding can be fatal as in the case of CNS hemorrhage, or severely debilitating following repeated bleeding into joints that results in crippling arthritis. Treatment for hemophilia includes the intravenous administration of clotting factor concentrates to replace the missing or defective protein. Venous access is therefore critical to the treatment of hemophilia and the prevention of complications due to bleeding. According to the US Centers for Disease Control and Prevention, approximately half of patients less than 16 years of age and one-third of all patients with hemophilia receive regular prophylactic injections of clotting factor concentrates. Prophylaxis, or the regular scheduled administration of antihemophilic factor concentrate, is effective in preventing bleeding. Among those patients with severe disease, in the absence of prophylaxis, approximately 13 bleeds, including nine joint hemorrhages, occur annually. In contrast, when prophylaxis is administered, the annual number of total and joint bleeds decreases to five and three, respectively. One of the major barriers to the more wide-spread use of prophylaxis is venous access. While peripheral venipuncture remains the first choice for venous access, central venous access devices are frequently used to facilitate repeated and/or urgent administration of clotting factor concentrates. The advantages of central venous access devices are well recognized in certain treatment regimens such as prophylaxis and immune tolerance therapy, as well as certain patient groups such as young children in whom venipuncture is often difficult and traumatic, and adults with scarred veins. Central venous access devices also allow earlier commencement of both home treatment and prophylaxis. The goal of this review is to discuss the different types of central venous access devices and their role in the management of hemophilia to provide practitioners that care for patients with hemophilia with the necessary information to make sound therapeutic recommendations to their patients.

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.

Side-effects and venous access issues with immune tolerance therapy

Immune tolerance therapy (ITT) is the most effective approach to eradicate inhibitors in patients with haemophilia who develop high-titre inhibitors. Yet ITT is associated with many adverse side-effects. Rarely, adverse side-effects arise from the various factor concentrates that patients on ITT receive or from adjuvant immunosuppressive agents used during ITT. Most adverse side-effects of ITT are related to the need for frequent and repetitive venous access, which often results in the need for central venous access devices (CVAD). These devices greatly facilitate the ability to give repeated doses of factor concentrates to patients and are particularly useful in young children who often have small and poorly functioning peripheral veins. These devices can become infected, can malfunction or can lead to venous thrombosis. These complications, although rarely causing mortality, may lead to significant morbidity including the need to have the devices removed and new ones inserted. As well, such CVAD complications may lead to reduced effectiveness of ITT through interruptions in ITT.

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.

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.

Tissue plasminogen activator to prevent central venous access device infections: a systematic review of central venous access catheter thrombosis, infection and thromboprophylaxis

The recent unequivocal demonstration that prophylaxis, three to four weekly factor infusions, is effective in preventing joint disease in children with haemophilia, has provided impetus to initiate prophylaxis early in such children. Yet, nearly a quarter (22%) of the 83% who required central venous access devices for factor infusion developed central venous access catheter (CVAD)-related infection. This limitation of CVAD use prevents many families from initiating prophylaxis. The frequent occurrence of local thrombosis accompanying CVAD-related infection in surgical patients and autopsy cases, the thrombogenic plastic CVAD surfaces, and local clot formation at the insertion site, suggest the potential role of thrombolytic agents in preventing these infections. Yet, correlation between CVAD-related infection and local thrombosis in children with haemophilia are lacking, and thromboprophylaxis to prevent CVAD-related infection is controversial. Tissue plasminogen activator (t-PA), a recombinant serine protease glycoprotein that lyses plasmin-bound fibrin and is safe and effective in the treatment of occluded catheters, has not been evaluated in the prevention of these infections. We performed a literature review of CVAD-related infection, CVAD-related thrombosis, and thromboprophylaxis studies to evaluate the role of t-PA in the prevention of these infections in children with haemophilia. Metanalysis of published thromboprophylaxis trials demonstrate current prophylaxis regimens do not prevent CVAD infection, and further, that thrombosis and infection do not necessarily occur simultaneously. Pilot data demonstrate CVAD infection reduction in haemophilic children by monthly t-PA in 18 haemophilic children, suggesting the potential role of t-PA in CVAD infection prevention. Clinical trials to evaluate t-PA in CVAD infection prevention are justified.

Haemophilia therapies

In the last few decades dramatic improvements in the management of haemophilia patients have occurred. Haemophilia has moved from a fatal or disabling disease to a hereditary disorder with available treatment and much better clinical outcomes. The safety of antihaemophilic factor concentrates has been dramatically improved and, in a multidisciplinary environment including haematologists, orthopaedic surgeons, paediatrics, infectiologists, specialised nurses and physiotherapists, complications related to haemophilia are now limited, markedly improving the quality of life of haemophiliacs. One can even think that the cure of haemophilia through gene therapy might occur in the next decades. Keeping this ultimate aim in mind, efforts at present are mainly focused on bioengineered Factor VIII/Factor IX concentrates with increased efficacy or longer half-life or decreased immunogenicity. In addition, several preclinical and clinical studies are being carried out for optimising and individually tailoring the therapeutic regimens of antihaemophilic therapies using global haemostasis tests in combination with the routine coagulation assays.

Inadvertent anticoagulation of a haemophiliac child with routine line flushing

We report the case of a 3-year-old boy with severe haemophilia A presenting with recurrent haemarthroses despite daily infusions of factor VIII delivered through a central venous access device (CVAD). Regular rinsing of the CVAD with heparin, according to a standard protocol, resulted in systemic anticoagulation, as demonstrated by prolonged thrombin time and therapeutic anti-Xa levels. The bleeding symptoms resolved after replacing heparin with a normal saline solution. This case illustrates that heparin administered to maintain CVAD patency should be used with caution in young haemophiliacs. Prolonged thrombin time should alert the physician to this possible CVAD complication.

Non-catheter associated venous thrombosis in hemophilia A and B. A critical review of all reported cases

All reported cases of non-catheter induced venous thrombosis in patients with hemophilia A or B have been carefully evaluated. A total of 27 cases were reported,12 patients with hemophilia A and 15 patients with hemophilia B. The age of patients varied between 9 and 67 years. There were 10 cases of deep vein thrombosis, 8 patients with pulmonary embolism accompanied or not by deep vein thrombosis, 5 cases of superficial vein thrombosis. In addition, there were 3 cases of thrombosis in unusual sites (1 retinal central vein thrombosis and 2 portal vein thrombosis). Finally, in one case, venous thrombosis was multiple. There was a fatality in a hemophilia B patient with pulmonary embolism. The most frequent risk or triggering factor in hemophilia A was the administration of Feiba or rFVIIa concentrates in patients with inhibitors. Surgery together with Prothrombin Complex concentrates was the most frequent cause in hemophilia B patients. Congenital associated prothrombotic risk factors were present in two patients. No or very few therapeutic procedures were initiated in these patients but for a suspension or reduction of concentrates infusion. In a few instances low molecular weight heparin was given for a few days. The frequent association of venous thrombosis with infusion of concentrates indicates the need for a careful evaluation of patients about to receive such therapy.

Pulmonary embolism in a patient with severe congenital deficiency for factor V during treatment with fresh frozen plasma

Thrombosis is a rare complication in patients with congenital clotting factor deficiencies. In most cases, it is related to inherited procoagulant factors, use of central venous catheters or administration of coagulation factor concentrates. There are only a few case reports about thrombotic events during treatment with fresh frozen plasma (FFP). We report the case of a patient with homozygous inherited factor V deficiency, who developed a pulmonary embolism at a time of treatment with methylene blue treated FFP (MBFFP). The patient had only two other factors predisposing to thrombosis and both were acquired: obesity and bed rest. He started anticoagulant treatment with low molecular weight heparin (LMWH) while the deficient factors were replaced with MBFFP. After 8 days of treatment the patient developed a severe respiratory insufficiency. Pulmonary haemorrhage was considered among the differential diagnosis and LMWH was stopped. An inferior vena cava filter was placed without any further thrombotic complications. To our knowledge, there are no reports about patients with clotting factor deficiencies who developed a thrombotic event during treatment with MBFFP.

Haemophilia and thrombophilia: an unexpected association!

In patients with haemophilia, a close correlation is usually observed between the clinical expression of the disease and plasmatic factor VIII/factor IX clotting activity. However, some patients experience milder bleeding phenotypes than others, although they exhibit a similar biological profile. The high prevalence of some inherited thrombophilia risk factors offers the possibility of a co-inheritance in haemophilic patients which could influence the phenotypic expression of the disease. Rare thrombotic complications occurring in haemophiliacs could also be facilitated by the co-inheritance of modifier genes. The majority of thrombotic events occurring in haemophiliacs are in relation to clotting factor infusions or central venous catheters. Concerning surgical situations, in the absence of therapeutic recommendations, postoperative thromboprophylaxis is not systematically performed in haemophiliacs. However, substitutive treatment more or less completely corrects the coagulation defect and makes the venous thrombosis risk closer to the control population. It should be emphasized that haemophilia does not fully protect against venous thromboembolic disease. Patients with haemophilia very infrequently experience thrombotic events. Thus, the management of thrombotic complications occurring in haemophilic patients should be discussed in each case according to the precipitating risk factors, the clinical context and the thrombo-haemorrhagic balance of the patient with respect to a particular clinical situation.

Consensus recommendations for use of central venous access devices in haemophilia

Venous access is essential for delivery of haemophilia factor concentrate. Wherever possible, peripheral veins remain the route of choice, and the use of central venous access devices (CVADs) should be limited to cases of clear need in patients with caregivers able to exercise diligence in CVAD care and should continue no longer than necessary. CVADs are of recognized value for repeated administration of coagulation factors in haemophilia, particularly for prophylaxis and immune tolerance therapy and in young children. Evidence to guide best practices has been fragmentary, and standardized methods for CVAD usage have yet to be established. We have developed management recommendations based upon available published evidence as well as extensive clinical experience. These recommendations address patient and CVAD selection; CVAD placement, care and removal; caregiver/patient guidance; and complications, including infection and thrombosis. In the absence of inhibitors, ports are recommended, primarily because of fewer associated infections than with external catheters. For patients with inhibitors, ports also appear to be associated with fewer infections. Infection is the most frequent complication, and recommendations to prevent and treat infections are supported by extensive clinical data and experience. Strict adherence to handwashing and aseptic technique are essential elements of catheter care. Evidence-based data regarding the detection and treatment of CVAD-related thrombotic complications are limited. Caregiver education is an integral part of CVAD use and the procedural practices of users should be regularly re-assessed. These recommendations provide a basis for sound current CVAD practice and are expected to undergo further refinements as new evidence is compiled and clinical experience is gained.

Central venous catheters in children with haemophilia

Infections, thrombosis and technical problems are the most frequent complications when using implantable central venous access devices in patients with haemophilia. There seem to be two major experiences concerning infections in non-inhibitor patients, one is approx. 0.2 infections per 1000 days and the other approx. 1.0(0.7-1.6)/1000 days. Infections are more frequent in inhibitor patients and one can expect approx. one infection per 6-12 months of use. The figures are low for clinically apparent thrombosis in the larger series on record, but routine venograms were not done in most of these series. In studies where this has been done, a high frequency of abnormalities on venograms have been seen in some but not in others. The final decision to use a central line has to be a compromise between the medical goal, the patient's bleeding tendency, the social situation and the expected risk of complications at the particular haemophilia center. Some of the complications may be reduced by adequate aseptic measures both during implantation and in the subsequent use and clear basic routines for surveillance of the systems and repeated education of the users.

Life-threatening thrombosis complicating the management of hepatic hemorrhage: anticoagulant treatment in a newborn with hemophilia B

The authors report the case of a neonate presenting with a distended abdomen and shock from factor IX (F.IX) deficiency and intrahepatic bleeding. After resuscitation and treatment with recombinant F.IX through a central venous line, he developed superior vena cava, upper extremity, and intracerebral venous thrombosis resulting in superior vena cava syndrome and intrathalamic hemorrhage. He was treated with F.IX to achieve near-normal F.IX activity levels and with low-dose unfractionated heparin with clinical improvement. F.IX replacement on a subsequent admission was again complicated by upper venous system thrombosis and improved with low-dose heparin. The case illustrates an unusual presentation of hemophilia, life-threatening thrombotic complications associated with factor replacement, and a strategy for anticoagulant management in the setting of hemophilic bleeding.

Central venous access devices in haemophilia

Central venous access devices (CVADs) can facilitate repeated and/or urgent administration of coagulation factors in haemophilic patients. We conducted a systematic review and meta-analysis of complication rates and risk factors for poor outcome. Forty-eight studies with a total of 2704 patients and 2973 CVADs were included. The primary indications for CVADs were immune tolerance therapy (34.9% of patients), difficult venous access (31.8%) and prophylaxis (29.1%). Fully implanted CVADs were employed in 77.4% of cases and external CVADs in 22.6%. A total of 1190 infections were reported, and the pooled incidence of infection was 0.66 per 1000 CVAD days [confidence interval (CI), 0.44-0.97 per 1000 CVAD days]. Among patients developing infection, the pooled time to first infection was 295 days (CI, 181-479 days). Presence of inhibitors was an independent risk factor for infection with an incidence rate ratio (IRR) of 1.67 (CI, 1.15-2.43). Infection was less likely in patients >6 years of age (IRR, 0.46; CI, 0.27-0.79) and recipients of fully implanted CVADs (IRR, 0.31; CI, 0.12-0.86). Available information on thrombosis was limited, with only 55 cases being reported. Eventually, 31.3% of CVADs were removed, and infection was the reason for removal in 69.9% of cases and thrombosis in 4.1%. The pooled time period CVADs remained indwelling prior to removal or the expiration of the study observation period was 578 days per CVAD (CI, 456-733 days per CVAD). CVADs can confer major benefits in patients with haemophilia requiring long-term venous access, and serious complications are rare.

Central venous catheter-related thrombosis presenting as superior vena cava syndrome in a haemophilic patient with inhibitors

We report the case of a 10.5-year-old boy with severe haemophilia A (SHA) and inhibitors who presented with superior vena cava (SVC) obstruction while on immune tolerance induction (ITI) with daily recombinant factor VIII (rFVIII) and factor eight bypassing activity (FEIBA) (75 U kg(-1)) twice a week. The boy had a right-sided implanted central venous catheter. Imaging revealed a large occlusive thrombus in the SVC with all upper venous system drainage occurring through the azygos and collateral veins. Despite initial success with local thrombolytic therapy using recombinant tissue plasminogen activator, the thrombus persisted. Mechanical thrombolysis and angioplasty resulted in the successful removal of the thrombus and resolution of the SVC syndrome. Unfractionated heparin was used to prevent thrombus reformation/propagation. A work-up did not reveal any underlying genetic prothrombotic risk factors. The occurrence of such a profoundly symptomatic thromboembolism (TE) in a boy with SHA with inhibitors is unusual. A combination of risk factors, including the ongoing infusion of high doses of FVIII in the context of a disappearance of inhibitors together with the infusion of clotting factors known to be potentially thrombogenic, may place haemophilic patients on ITI (immune tolerance induction) at risk for this rare, life-threatening complication. The appropriate management of TEs in such a setting is unknown.

Adverse events in the prophylaxis of haemophilia

Whilst prophylaxis undoubtedly offers many advantages, the potential for adverse effects must also be borne in mind. Modern plasma-derived products have an extremely good safety record with regard to transmission of pathogens, although continuous vigilance is required as new pathogens continue to emerge, eg new variant Creutzfeldt-Jakob disease. There is no evidence that prophylactic treatment is associated with an increased incidence of inhibitors, and it is now recognized that genetic factors are the most significant in conferring susceptibility. Although subtle immunological abnormalities have also been observed in patients with haemophilia, there is no evidence that these are of any clinical significance. There has been a growing trend to use indwelling venous catheters for prophylaxis. The risk of infection has been appreciated for some time, although it has only recently been possible to quantify this with more precision. The risk of catheter-associated thrombosis is now recognized to be higher than hitherto appreciated. Whilst sporting activities are to be encouraged, there is a potential for significant trauma in children with prophylaxis, as plasma coagulation factor levels remain far below normal with the usual regimens.

Central venous lines in haemophilia

Infections and technical problems are the most frequent complications when using implantable central venous access devices in patients with haemophilia. There are two major experiences reported concerning infections in noninhibitor patients: one is approximately 0.2 infections per 1000 days and the other approximately 1.0 (0.7-1.6) per 1000 days. Infections are more frequent in inhibitor patients and approximately one infection per 6-12 months of use can be expected. The figures are low for clinically apparent thrombosis in the larger series on record, but routine venograms were not carried out in most of these series. In studies where this has been done, a high frequency of abnormalities on venograms has been seen in some but not in others. The final decision to use a central line has to take into account the medical goal, the patient's bleeding tendency, the social situation and the expected risk of complications at the particular haemophilia centre. Some of the complications may be reduced by adequate aseptic measures both during implantation and in subsequent use, and by clear basic routines for surveillance of the systems and repeated education of the users.

Treatment strategies in children with hemophilia

Hemophilia is an inherited bleeding disorder caused by quantitative or qualitative defects in the synthesis of factor VIII (FVIII) or factor IX (FIX). Clinically, it is divided into severe, moderate and mild disease depending on the levels of FVIII or FIX in the blood. The bleeding tendency is most pronounced and can start at a very young age in severe hemophilia, which is characterized by repeated hemorrhage into the joints and muscles. Without treatment, these episodes lead to severe arthropathy, and there is also a high risk of lethal cerebral hemorrhage. The treatment of bleeding symptoms requires the correction of the coagulation defect. Factor concentrates have been available for 30 years, initially with the development of cryoprecipitate, subsequently with increasingly purified plasma-derived forms, and ultimately with recombinant clotting factor concentrates. The advantage of this highly effective therapy has been subdued by the outbreak of HIV and Hepatitis C infections in patients with hemophilia treated with factor concentrates which did not have adequate viral inactivation steps in the purification process. Plasma-derived and recombinant factor concentrates are today considered to have a good safety profile, but are only available for a small group of hemophilia patients worldwide. A multidisciplinary team approach is important for early diagnosis, communication with the patient and parents, and to tailor the best treatment possible with the amount of clotting factor concentrates available. The main goal of hemophilia treatment is to prevent bleeding symptoms and allow normal integration in social life. In patients with severe hemophilia, this can best be achieved by early home treatment and primary prophylaxis. Future developments in gene therapy may transform severe hemophilia to a mild form, with no need for regular injections of clotting factor concentrates.

Simultaneous deep venous thrombosis and acquired factor VIII inhibitor

Acquired hemophilia A is a life-threatening immune-mediated hemorrhagic disorder that is most often found in individuals older than 50 who present with an unexplained activated partial thromboplastin time (aPTT) prolongation and clinically significant bleeding. The prolonged aPTT associated with acquired hemophilia A reflects factor VIII activity deficiency due to neutralizing or clearing autoantibodies. Deep venous thrombosis, in contrast, is a veno-occlusive disorder associated with several distinct hypercoagulable states that can result in significant morbidity and mortality due to pulmonary embolism, thrombus extension, and the post-thrombotic syndrome. A prolonged aPTT in the setting of thrombosis may reflect the presence of a lupus anticoagulant. In the absence of accurate diagnosis and the immediate institution of specific therapy, both disorders can be fatal. Three cases of acquired factor VIII inhibitors that included a prolonged aPTT, bleeding, and duplex ultrasound evidence of deep venous thrombosis are presented. The diagnostic and therapeutic challenges posed by these cases as well as a proposed mechanism by which pathologic thrombosis can develop in a patient with a life-threatening bleeding disorder are discussed.

Prophylaxis in developed and in emerging countries

The significant progress made in recent years in the safety and efficacy of both plasma-derived and recombinant factor concentrates has allowed treatment programmes to be developed that go beyond the simply curative or the treatment of the consequences of the disease (episodic or on-demand treatment), enabling the criteria of preventative medicine to be applied to congenital bleeding disorders. The aim of these programmes is to achieve constant, minimum levels of factor in patients above 1 or 2%, thereby converting severe haemophilia into moderate haemophilia.

Cost-utility analysis of primary prophylaxis versus treatment on-demand for individuals with severe haemophilia

OBJECTIVE

To assess the cost effectiveness of primary prophylaxis with clotting factor instead of treatment following a bleed (on-demand) for individuals with severe haemophilia.

DESIGN

Different data sources on the clinical effects and costs of treatments were combined using a Markov model.

SETTING

English treatment centres.

PERSPECTIVE

UK societal.

PARTICIPANTS

Hypothetical cohorts of 100 individuals with severe haemophilia A or B or severe von Willebrands disease.

INTERVENTIONS

Primary prophylaxis treatment on-demand with clotting factor.

OUTCOME MEASURES

Costs, quality-adjusted life-years (QALYs) and incremental cost per QALY in UK pounds ( pound, 1999/2000 values).

RESULTS

The baseline results showed that treating individuals with severe haemophilia A/severe von Willebrands disease or severe haemophilia B with primary prophylaxis instead of treatment on-demand cost an additional pound 46500 and pound 8600 per QALY gained, respectively. However, the results were extremely sensitive to a number of factors including the clotting factor unit cost, the time between prophylactic doses and the discount rate.

CONCLUSIONS

Despite the high costs of treatment, primary prophylaxis was cost effective compared with treatment on-demand in some scenarios. Primary prophylaxis is more likely to be cost effective for individuals with severe haemophilia B compared with individuals with severe haemophilia A/severe von Willebrands disease. Further research is required to assess the relationship between methods of clotting factor infusion and health-related quality-of-life.

Catheter-related deep venous thrombosis in children with hemophilia

Central venous catheters (CVCs) are a common adjunct to hemophilia therapy, but the risk of CVC-related deep venous thrombosis (DVT) in hemophiliacs is not well defined. In a previous study, 13 patients with CVCs had no radiographic evidence of DVT. However, recent abstracts and case studies demonstrate that DVT does occur. Therefore, this study sought to determine the frequency of DVT in children with hemophilia and long-term CVCs and to correlate venographic findings with clinical features. All hemophilia patients with tunneled subclavian CVCs in place for 12 months or more were candidates for evaluation. Patients were examined for physical signs of DVT and questioned about catheter dysfunction. Contrast venograms were obtained to identify DVT. Fifteen boys with severe hemophilia were evaluated, including 9 from the initially studied group of 13. Eight patients had evidence of DVT, 5 of whom previously had normal venograms. Five of 15 patients had clinical problems related to the CVC, all of whom had DVT. Four of 15 patients had suggestive physical signs; 3 had DVT. The mean duration of catheter placement for all patients was 57.5 months (range, 12-102 months). For patients with DVT, the mean duration was 66.6 +/- 7.5 months, compared to 49.5 +/- 7.2 months for patients without DVT (P =.06). No patient whose CVC was in place fewer than 48 months had an abnormal venogram. Many hemophilia patients with CVCs develop DVT of the upper venous system, and the risk increases with duration of catheter placement.

Central venous access devices in children with congenital coagulation disorders: complications and long-term outcome

Reliable venous access is essential to facilitate the administration of prophylactic factor concentrate or blood products in children with congenital coagulation disorders and immune tolerance therapy (ITT) regimens in those who develop high responding inhibitors. Poor venous access is even more problematic in very young children, the vast majority of whom will require the insertion of central venous access devices (CVADs). Previous studies have suggested that infection rates are low and that there are few long-term complications associated with CVAD usage. We have reviewed 86 CVADs that have been inserted, since 1988, in 58 children with congenital bleeding disorders, aged 6 d to 16.5 years, attending Great Ormond Street Hospital, London, and the National Children's Hospital, Dublin. The devices have remained in situ for 2 weeks to 92 months (median 22.5 months). Early (0-2 weeks) complications of CVAD insertion included nine bleeding episodes, one extravasation of factor concentrate, three allergic reactions to factor concentrate and five catheter infections. Overall, CVAD infection was the commonest problem encountered, with 52 devices (60%) becoming infected. Twenty-seven CVADs (31%) required removal. Infection rates in children without inhibitors (29/68) were 1/20 patient-months or 1. 6 infections/1000 patient-days, but infection rates for those with inhibitors were 1/8.5 patient-months or 4.3/1000 patient-days. Staphylococcus epidermidis was the predominant organism (25/52) isolated. Blockage of CVAD (four) and catheter disconnection (four) were the most frequently occurring non-infectious long-term complications. Skin erosion of the port was also seen in three children, in one child at 20 months, in one at 29 months and in one at 34 months after insertion. This study demonstrates a high CVAD infection rate and highlights the long-term complications of CVAD usage.

Teaching parents advanced clinical skills

The management of haemophilia, in common with many other inherited, chronic disorders, has witnessed enormous advances and improvements. The quality of life enjoyed by children with haemophilia is excellent. To realize these benefits, however, expectations are placed on parents to administer intravenous treatment at home. The frequency of required treatment can be as often as alternate days. The role of implantable venous access devices has made venous access in young children at home a realistic procedure. This is a highly complex skill for the lay person to undertake, and comprehensive parental teaching and standardized written information are necessary. A teaching package has been created that commences with theoretical instruction and moves onto practical training. On-going assessment is then carried out at regular intervals in the home environment. Not only does this package provide a formal framework for instruction, it also facilitates emotional support for both the child and parents, which can be given in a planned manner. Nurses are professionally accountable for the information and teaching they give. This package documents the process of training undertaken and standardizes the level of information given. Thereby providing reassurance to nurses that they have fulfilled the professional requirements placed on them. Currently, there is no other source of information about implantable venous access devices for the lay carer. This package could be of value in other chronic conditions that incorporate an element of intravenous home care.