Complications of central venous access devices in paediatric haemophilia patients.

We conducted a retrospective survey of our experience with central venous access devices (CVADs) implanted in children with haemophilia seen at the Vanderbilt Hemostasis-Thrombosis Clinic from 1986 to 2000. Following discussion with parents on the merits and risks associated with the use of CVADs for immune tolerance induction or factor prophylaxis, catheters were inserted under sterile technique in the operating room. One nurse provided demonstration and teaching about catheter care and access. Thirty central venous catheters were inserted in 22 children. Our survey revealed that the two most common complications associated with central venous catheters were bacteraemia and thrombosis. We found a sepsis rate of 0.30/1000 catheter-days or one episode of bacteraemia for every 3346 days of catheter use. The thrombosis rate of our cohort was 0.13/1000 catheter-days or one episode of thrombosis for every 7529 days of catheter use. Uncomplicated venous access is essential in children with severe haemophilia who require prophylaxis or immune tolerance induction. While infection was the most common complication observed in our series, we experienced a lower overall infection rate than several reported series. Catheter thrombosis and subsequent obstruction may occur as a result of intraluminal fibrin deposits. We conclude that the use of implantable central venous catheters is an effective method for accessing children with haemophilia. We accept that the benefits of CVADs in the treatment of paediatric haemophilia patients outweigh the previously documented risks. Future prospective studies should be designed to define all associated risks and to determine effective strategies to reduce them.

High-dose cytosine arabinoside and etoposide: an effective regimen without anthracyclines for refractory childhood acute non-lymphocytic leukemia.

The purpose of this report is to describe the tolerability and activity of the combination of high-dose cytosine arabinoside (Ara-C) given at the maximum tolerated dose of 36 g/m2, together with high doses of etoposide in relapsed and refractory childhood acute leukemias. Eighteen children with relapsed or refractory acute leukemia were treated with Ara-C 3 g/m2 every 12 h on days 1-6, followed by etoposide 400 mg/m2 on days 7-9 (HDAC/VP-16). Eight children with refractory disease received HDAC/VP-16 as salvage induction therapy after failing conventional induction regimens; four of five refractory ANLL patients (80%) had a complete response (CR) after HDAC/VP-16 therapy. Ten patients received HDAC/VP-16 as post-remission intensification therapy; five patients (four ANLL, one relapsed ALL) remain in second CR at 56, 26, 9, 5 and 2 months. Toxicities were primarily hematologic and dermatologic. Seven patients (39%) developed bacterial or fungal infections; four patients developed grade 3 or 4 acral erythema. No patient died of therapy-related toxicity. The combination of 36 g/m2 cytosine arabinoside and 1200 mg/m2 etoposide is an effective regimen for children with relapsed or refractory acute nonlymphocytic leukemia, with tolerable toxicities; the absence of anthracyclines makes this regimen suitable for patients who have previously received maximal doses of anthracyclines or who have evidence of cardiac dysfunction. Further evaluation of this regimen in acute nonlymphocytic leukemia is presently being investigated.

Stress and incidence of bleeding in children and adolescents with hemophilia.

OBJECTIVE: To examine the relationship of stress and incidence of bleeding in boys with hemophilia. STUDY DESIGN: We conducted a 6-month longitudinal study of 97 subjects (ages 4 to 16 years) from six hemophilia centers. Diaries recorded bleeding episodes (including site and history of previous trauma) and both child and parent daily stress. Parent and child stressful life event measures were obtained monthly. Socioeconomic data and clotting factor level were determined at enrollment. Logistic regression models examined the influence of recent stress on likelihood of bleeding on each day, controlling for factor level and socioeconomic data. We also determined associations of aggregated previous month's events with bleeding likelihood in the succeeding month. RESULTS: Fifty-eight percent of study participants had severe hemophilia. The sample population averaged nine bleeding episodes per 6 months; of these; two thirds of bleeding incidents occurred into joints and 44% after injury. Factor level strongly predicted bleeding incidence (p < 0.0001). Increased parent stress was associated with increased bleeding in general (odds ratio = 1.37, p < 0.003) and with injury (odds ratio = 1.65, p < 0.001), but not bleeding into joints. Similar findings followed parent reports of positive life events. Increased parent negative life events in 1 month were associated with increased bleeding in the succeeding month (p < 0.05). CONCLUSION: Short- and long-term parental stress may lead to increased bleeding incidence in hemophilia, although factor level much more strongly predicts bleeding.

Analysis of factor VIII gene inversion mutations in 166 unrelated haemophilia A families: frequency and utility in genetic counselling.

Haemophilia A is an X-linked recessive bleeding disorder of variable severity that is caused by a deficiency of coagulation factor VIII (FVIII). The disease results from mutations in the FVIII gene which are heterogenous both in type and position within the gene. Recently, however, inversion mutations were found to be common to patients with severe disease (Lakich et al., 1993). These mutations result from intrachromosomal recombinations between DNA sequences in the A gene (located in intron 22 of the FVIII gene) and one of two A genes upstream to the FVIII gene. To determine the frequency of these inversions we performed Southern blot analysis on banked DNA from 166 consecutive, unrelated haemophilia A families previously referred for carrier or prenatal testing. In 57/166 (34%) families an inversion or other unique mutation was detected. The distal and proximal A genes lying upstream to the FVIII gene were involved in 79% and 18% of the mutations, respectively, but in 3% of the families the sequences involved in the mutation have not been identified. In 20/38 (53%) families with severe disease a mutation was detected. Interestingly, the relative risk of developing inhibitors in patients with FVIII gene inversions or other 3° mutations detected by this assay, as compared to patients with no detectable mutation by this assay, was 3.8. In families for which a mutation is detected, direct DNA testing is an accurate and inexpensive alternative to linkage analysis for prenatal or haemophilia A carrier testing.

A prospective study of patterns of bleeding in boys with haemophilia.

To describe the patterns of bleeding and clotting factor concentrate use in boys with haemophilia over a 6-month period, daily diary records of bleeding, factor use, levels of physical activity, chore performance and school attendance were collected from parents of 96 males between 4 and 17 years of age with haemophilia A or B followed at six comprehensive haemophilia treatment centres in Massachusetts, Rhode Island and Tennessee. 14 243 person days were available for analysis. The sample cohort averaged approximately nine bleeding episodes (1.5 per months), almost two-thirds of which were haemarthroses. 44% of bleeds were associated with injury and the average duration was 1.4 days. New bleeding episodes were significantly more likely to begin on weekdays (Monday-Thursday) than on weekends (Friday-Sunday). Boys with more severe disease had significantly more bleeding episodes and a higher frequency of haemarthroses. Boys with the most severe disease were also more likely to have joints involved when they bled and to have more spontaneous bleedings without apparent preceding trauma. Bleeding was associated with increased school absence, decreased levels of physical activity and decreased rates of household task performance. Relatively high rates of bleeding associated with trauma suggest the need for preventive interventions.

Long-term granulocyte-macrophage colony-stimulating factor and immunosuppression in the treatment of acquired severe aplastic anemia.

PURPOSE: Seven children with newly diagnosed acquired severe aplastic anemia (SAA) were treated with a combination of long-term granulocyte-macrophage colony-stimulating factor (GM-CSF) and immunosuppression to assess the potential for GM-CSF to induce sustained neutrophil recovery, reduce the incidence of infection, and enhance the therapeutic efficacy of immunosuppression. METHODS: Patients received a 14-day course of i.v. antithymocyte globulin 15 mg/kg/day with oral prednisone 1 mg/kg/day, long-term daily oral cyclosporine A 10 mg/kg/day, and long-term daily s.c. GM-CSF 5 micrograms/kg/day. RESULTS: All seven children recovered an absolute neutrophil count of > 1.0 x 10(9)/L within 3.5 months of diagnosis (mean 60 days). Of the six children followed throughout their entire illness (follow-up 10-27 months), five are platelet and red cell transfusion independent (three off-therapy, two on tapering therapy) and one continues on therapy with a diminishing transfusion requirement. Compared with seven children treated previously with immunosuppression alone, children who received GM-CSF spent fewer days in the hospital and were less likely to develop infection. CONCLUSIONS: The addition of GM-CSF to immunosuppressive therapy appears to be beneficial in the treatment of children with acquired SAA with GM-CSF stimulating granulopoiesis. The children are better protected from infectious complications while immunosuppressive agents achieve full therapeutic potential.

Cross-platform hypermedia examinations on the Web.

The authors developed a multiple-choice medical testing system delivered using the World Wide Web. It evolved from an older, single-platform, locally-developed computer-based examination. The old system offered a number of advantages over traditional paper-based examinations, such as digital graphics and quicker, easier scoring. The new system builds on these advantages with its true cross-platform design and the addition of hypertext learning responses. The benefits of this system will increase as more medical educational resources migrate to the Web. Faculty and student feedback has been positive. The authors encourage other institutions to experiment with Web-based teaching materials, including examinations.

Why does the human factor IX gene have a G + C content of 40%?

The factor IX gene has a G + C content of approximately 40% in all mammalian species examined. In human factor IX, C----T and G----A transitions at the dinucleotide CpG are elevated at least 24-fold relative to other transitions. Can the G + C content be explained solely by this hot spot of mutation? Using our mathematical model, we show that the elevation of mutation at CpG cannot alone lower the G + C content below 45%. To search for other hot spots of mutation that might contribute to the reduction of G + C content, we assessed the relative rates of base substitution in our sample of 160 families with hemophilia B. Seventeen independent single-base substitutions are reported herein for a total of 96 independent point mutations in our sample. The following conclusions emerge from the analysis of our data and, where appropriate, the data of others: (1) Transversions at CpG are elevated an estimated 7.7-fold relative to other transversions. (2) The mutation rates at non-CpG dinucleotides are remarkably uniform; none of the observed rates are either more than twofold above the median for transitions or more than threefold above the median for transversions. (3) The pattern of recent mutation is compatible with the pattern during mammalian evolution that has maintained the G + C content of the factor IX gene at approximately 40%.

Characterization of a thrombin cleavage site mutation (Arg 1689 to Cys) in the factor VIII gene of two unrelated patients with cross-reacting material-positive hemophilia A.

The molecular defect responsible for moderate and severe hemophilia A has been identified for two unrelated patients with the CRM-positive form of this disorder (factor VIII activity of 0.02 and 0.05 U/mL with factor VIII antigen of 0.87 and 2.20 U/mL). In both cases, the immunopurified dysfunctional factor VIII protein is abnormal, in that the 80 Kd light chain is not cleaved by thrombin at arginine-1689. The basis for this failure was identified by polymerase chain reaction amplification of exon 14 of the variant factor VIII genes and direct sequencing of the amplified products. In both cases, a single base substitution (C to T) was identified that produces an arginine to cysteine substitution at amino acid residue 1689. These data identify the molecular defects of the two identical factor VIII variant proteins. The dysfunctional factor VIII has been designated "Factor VIII-East Hartford," the residence of the patient in whom the defect was first identified.

Inherited hypercoagulable states in children.

Disorders that predispose children to venous thrombosis include inherited abnormalities of antithrombin III, protein S, protein C, fibrinogen, and plasminogen. Arterial thrombosis may result from disorders that produce endothelial damage, abnormal vascular flow, or increased platelet aggregation. We present here a case of a child who had recurrent thromboses and discuss the evaluation and management of such patients.

Does stress affect bleeding in hemophilia? A review of the literature.

Many bleeding episodes in hemophilia are thought to be related to ambient stress. The evidence in support of this hypothesis comes from a variety of anecdotal and clinical reports. Whether or not stress leads to bleeding has had little direct study in a prospective way, however, and methodological problems affect most of the studies in this field. This paper examines the evidence in support of this hypothesis and suggests ways to improve research relating stress to bleeding.

Detection of hemophilia A carriers using intragenic factor VIII:C DNA polymorphisms.

A DNA polymorphism for an Xbal site in intron 22 of the human factor VIII:C gene extends the utility of DNA methods for carrier detection in families segregating for hemophilia A. While the DNA polymorphism detected by a BclI site in intron 18 of the factor VIII:C gene was informative for 41% of females studied, the BglI/intron 25 polymorphism provided no additional information because of apparent linkage disequilibrium. In contrast, the Xbal intron 22 polymorphism was useful in 53% of women who were uninformative (homozygous) for either the BclI or BglI polymorphisms. Using the BclI/intron 18 and Xbal/intron 22 intragenic polymorphisms, we could provide highly accurate information for 68% of women we studied who were at risk for carriership. The carrier status of the remaining 32% could be determined utilizing the closely linked Taql/St14 DNA polymorphism.

MR imaging of hemophiliac arthropathy.

Magnetic resonance (MR) imaging of the knee was performed in 10 patients with hemophilia. The periarticular and subchondral abnormalities were classified according to the signal intensity from these regions on T1- and T2-weighted pulse sequences. Periarticular abnormalities were detected in 50% of the hemophiliac joints, and fibrous changes were noted in 57% of all the areas of subchondral abnormality. Magnetic resonance imaging identifies periarticular and subchondral abnormalities in patients with hemophilia and may help in monitoring the progress of the disease process.