Current treatment of von Willebrand’s disease

Fortschritte im Verständnis der Pathophysiologie, verbesserte diagnostische Techniken und Erfahrungen in den Erfordernissen der Therapie während der vergangenen 20 bis 25 Jahre haben zu deutlichen Verbesserungen der Sicherheit der Diagnose und der Lebensqualität von Patienten mit von Willebrand-Syndrom (VWS) geführt. Die wissenschaftlichen Erkenntnisse aus dieser Zeit haben dazu geführt, dass das VWS zurzeit als eine extrem heterogene Erkrankung gilt. Für einige Subtypen des VWS konnten die qualitativen Veränderungen des von-Willebrand-Faktors (VWF) eindeutig auf den zugrundeliegenden Gendefekt zurückgeführt werden, während dieses für andere Subtypen nicht gelungen ist. Für die häufigste Form, als Typ 1 bezeichnet, korreliert die Verminderung des VWF mit dem Funktionsverlust. Hier stehen wir allerdings erst in der Anfangsphase der Aufklärung der kausalen Gendefekte.

Behandlungsgrundlagen, welche die Kriterien evidenzbasierter Richtlinien erfüllen, existieren nicht. Daher stützen sich die Therapiestrategien weitgehend auf Empirie. Die Basis dieser Übersichtsarbeit über Therapiemodalitäten bei VWS-Patienten beruht auf der aktuellen Literatur und der klinischen Erfahrung der Autoren. Es ist unsere Absicht, die Fragen aufzuzeigen, die zurzeit bezüglich der Therapie in Abhängigkeit von der VWS-Subtypisierung diskutiert werden. Über die aktuellen Therapieoptionen auf pharmakologischer Basis oder mittels Substitution hinaus, sollen auch solche aufgezeigt werden, die sich vielleicht schon in naher Zukunft ergeben können.

Transfusion-associated anaphylaxis during anaesthesia and surgery--a retrospective study

BACKGROUND AND OBJECTIVES

Transfusion-associated anaphylaxis (TAA) is a severe adverse reaction reported to occur in 1:9000-90,000 transfusions. According to the Danish Registration of Transfusion Risks (DART), the frequency is 1:300,000 transfusions, which suggests insufficient reporting of TAA in Denmark. Our aims were to identify possible cases of TAA, to characterize their symptoms and tryptase levels and to investigate the reporting of TAA to the haemovigilance systems.

MATERIAL AND METHODS

We reviewed 245 patients with suspected allergic reactions during anaesthesia and surgery, investigated at the Danish Anaesthesia Allergy Centre (DAAC). Based on the outcome of this investigation, the patients were classified as DAAC positive (confirmed hypersensitivity to identified agent, n = 112), or DAAC negative (no confirmed hypersensitivity, n = 133). Data on case history, details of blood transfusion and results of laboratory and clinical investigations were collected. TAA cases were identified according to the recommendations of the International Society of Blood Transfusion (ISBT).

RESULTS

Ten possible TAA cases (30% of all transfused patients) were identified, all DAAC negative. The frequency of elevated serum tryptase, hypotension and male sex was significantly higher among these cases compared with the remaining DAAC negative (P < 0·05), but not different from the DAAC-positive patients. One case had been reported to the Blood Bank haemovigilance system and none to DART.

CONCLUSION

We identified unreported cases of possible TAA, which resembled the DAAC-positive patients with respect to elevated tryptase and symptoms. By applying the ISBT criteria of adverse transfusion reactions, we conclude that TAA during anaesthesia and surgery is likely to be underreported in Denmark.

FXIII: mechanisms of action in the treatment of hemophilia A

BACKGROUND

Hemophilia is characterized by abnormal thrombin generation and impaired clot stability. FXIII promotes clot stability and may be a useful adjunct treatment for hemophilia.

OBJECTIVES

This study examined the clot stabilizing effects and safety of supra-physiological FXIII and explored the mechanisms via which FXIII exerts its effects in hemophilia A.

METHODS

The effects of FXIII on clot formation and stability were examined using a thromboelastometry assay and blood samples collected from six patients with severe hemophilia A. The effect of FXIII on clot formation was also assessed using a murine model. The mechanisms of FXIII action in hemophilia A were explored by measuring thrombin generation, rates of FXIII activation and effects on clot permeability, pore size and fibrin fiber diameter.

RESULTS

This study demonstrates that supra-physiological concentrations of FXIII stabilize clots in blood from patients with hemophilia by improving resistance to t-Pa-induced fibrinolysis even at low concentrations of FVIII (FVIII< 0.1 IU mL⁻¹, P < 0.05, anova). Addition of FXIII stoichiometrically up-regulates its activation, correcting the fibrin clot structure, reducing clot permeability and facilitating thrombin generation; FXIII significantly shortens ttPeak and lagtime (P < 0.05) in FVIII-deficient plasma, providing a novel explanation for its positive effects on clot stability and structure. The murine model indicates that supra-physiological FXIII is tolerated and does not significantly alter time to clot formation.

CONCLUSION

The effects of FXIII on clot stability and physical clot structure are seen at low concentrations of FVIII, indicating that FXIII could be a useful treatment in a variety of clinical scenarios.

Dynamic behaviour of selected PET tracers in embryonated chicken eggs

Positron emission tomography/computer tomography (PET/CT) is an established method in preclinical research in small animal disease models and the clinical diagnosis of cancer. It combines functional information of the positron-emitting biomarker with the anatomical data obtained from the CT image. Thus, it allows for 4D in vivo investigation of biological processes. Recently, PET/CT was used to monitor bone growth of chicken embryos using (18)F-fluoride as a bone-seeking tracer. We are interested in investigating the adequacy of additional PET/CT tracers in chicken embryos as an in vivo model system. For this reason, we evaluated several positron emitting compounds typically used in clinical tests or if these were not commercially available, we synthesised them. We studied the properties of these (18)F- and (68)Ga-labelled tracers and of (64)Cu-chloride in catheterised eggs via small animal microPET/CT. 2-Deoxy-2-[(18)F]fluoroglucose ([(18)F]FDG) was primarily absorbed at the sites of bone growth. (64)Cu chloride and a (68)Ga-labelled amyloid-fibril-binding antibody accumulated in the liver, while the (68)Ga-albumin desferrioxamine conjugate signal in liver decreased over time. These results indicate that these biomarkers can potentially be used for the monitoring of biological processes in chicken eggs as an animal model.

Novel coagulation factor concentrates: issues relating to their clinical implementation and pharmacokinetic assessment for optimal prophylaxis in haemophilia patients

Prophylaxis is considered the optimal treatment regimen for patients with severe haemophilia, and may be especially important in the prevention of joint disease. Novel coagulation factor concentrates with prolonged half-lives promise to improve patient treatment by enabling prophylaxis with less frequent dosing. With the call to individualize therapy in haemophilia, there is growing awareness of the need to use pharmacokinetic (PK) assessments to tailor prophylaxis. However, for new factor concentrates, it is not yet known which PK values will be most informative for optimizing prophylaxis. This topic was explored at the Eighth Zurich Haemophilia Forum. On the basis of our clinical experience and a discussion of the literature, we report key issues relating to the PK assessment of new coagulation factors and include suggestions on the implementation of PK data to optimize therapy. As both inter- and intra-individual variability in factor half-life have been reported, we suggest that frequent PK assessments should be conducted. However, to diminish the burden of more frequent sampling, sparser sampling strategies and the use of population modelling should be considered. Guidelines on how to assay new factor concentrates, and which PK parameters should be measured, are needed. Concerns were raised regarding the possibility of breakthrough bleeding, and current thinking on how to prevent breakthrough bleeding may no longer be appropriate. Finally, as treatment adherence may be more important to ensure that a therapeutic level of a new coagulation factor concentrate is maintained, behavioural techniques could be implemented to help to improve treatment adherence.

Dynamic APTT parameters: applications in thrombophilia

BACKGROUND

Patients with a history of venous thrombosis occasionally have shortened APTTs when compared with those of healthy references, but the clinical applicability of a shortened APTT is limited.

OBJECTIVES

The present study aimed to characterize dynamic APTT profiles in patients with previously documented venous thrombosis and hypothesized that the APTT-MaxVel was significantly elevated in patients with a history of venous thrombosis as compared with healthy controls.

METHODS

We performed a case control study, enrolling a total of 38 patients, 17 males and 21 females, with a verified recent venous thrombotic event, as well as 88 healthy controls. Fifty-three per cent of patients were found to have a biochemical risk factor. A standard APTT was recorded in platelet-poor plasma, and the digital clotting signal was processed using simple algorithms developed to derive dynamic coagulation parameters.

RESULTS

Patients had a significantly higher mean APTT-MaxVel (195.5 s(-1) ; SD = 57; 95% CI, 176.8-214.1) as compared with healthy controls (137.3 s(-1) ; SD = 21; 95% CI, 130.7-143.8). Patients also had significantly shorter mean APTTs (26.9 s; SD = 3.2; 95% CI, 25.9-28.0) than healthy controls (28.5 s; SD = 2.8; 95% CI, 27.9-29.0). While only one out of 38 patients (2.6%) had a standard APTT below the lower reference interval, 15 of the 38 patients (38.5%) had an APTT-MaxVel above the upper reference limit. Regression analysis revealed linear correlation between FVIII:C, the level of fibrinogen and APTT-MaxVel (R(2) = 0.89, P < 0.05).

CONCLUSIONS

Simple signal processing of the APTT and the use of dynamic parameters represents a stronger predictive marker for hypercoagulation in patients with verified venous thrombosis than the standard APTT measurement.

Management of muscle haematomas in patients with severe haemophilia in an evidence-poor world

Treatment studies in haemophilia focus on joint bleeds; however, some 10-25% of bleeds occur in muscles. This review addresses management of muscle haematoma in severe haemophilia, defines gaps in the published evidence, and presents a combined clinician and physiotherapist perspective of treatment modalities. The following grade 2C recommendations were synthesized: (i) Sport and activity should be based on individual factor levels, bleeding history and physical characteristics, (ii) Musculoskeletal review aids the management of children and adults, (iii) 'Time to full recovery' should be realistic and based on known timelines from the healthy population, (iv) Diagnosis should be carried out by both a clinician and physiotherapist, (v) Severe muscle bleeds should be treated similarly to surgical patients: a 50% trough for 10-14 days followed by high-level prophylaxis, (vi) Protection, rest, ice, compression and elevation should be implemented in the acute stage, and (vii) Physiotherapy and rehabilitation should be divided into: control of haemorrhage (phase 1); restoration of Range of Movement (ROM) and strength (phase 2); functional rehabilitation and return to normal living (phase 3). Recommendations specifically for inhibitor patients include: (i) Minor to moderate bleeds should be managed by home-treatment within 1 h of bleed onset using either one injection of rFVIIa 270 μg kg(-1), or two to three injections of rFVIIa 90 μg kg(-1) (2-3 h intervals), or FEIBA 50-100 U kg(-1) (repeated at 12-hourly intervals, if necessary) and (ii) Severe muscle bleeds should be supervised by the treatment centre and include bypassing agents until clinical improvement is observed.

The need for speed in the management of haemophilia patients with inhibitors

Rapid control of bleeding is the key to reducing bleeding complications and thereby preserving joint and musculoskeletal function in haemophilia patients with inhibitors. However, this requires early diagnosis following the onset of bleeding and strategies for rapid treatment in an outpatient setting. Overarching themes on the need for speed in managing bleeds in haemophilia patients were examined by a panel of clinicians experienced in managing inhibitor patients and joint disease during the Third Zürich Haemophilia Forum on 8 May 2009. This report summarizes the opinions of the panel on how to achieve rapid bleeding control in inhibitor patients and areas that were identified by the panel for future research or as needing new consensus guidelines. The consensus was that home treatment should be established for haemophilia patients with inhibitors, as it is associated with a faster time to treatment, as well as improvements in the quality of life of patients and their carers. In addition, as improved haemostatic control now allows inhibitor patients to participate in a wider range of physical activities, specific guidelines are required on which types of sport and work are appropriate. It was agreed that clear, systematic approaches are needed for early diagnosis of joint and muscle bleeds in inhibitor patients, which could facilitate rapid treatment. There may be opportunities for exploiting new diagnostic techniques from osteoarthritis to enable earlier diagnosis of haemophilic arthropathy. Overall, it was concluded that greater emphasis should be placed on education and patients' psychological needs, to enable inhibitor patients to cope up more effectively with their disease.

Stabilization of fibrin clots by activated prothrombin complex concentrate and tranexamic acid in FVIII inhibitor plasma

Defective hemostasis in haemophilia patients with FVIII inhibitors results in a dramatic decrease in thrombin generation forming unstable fibrin clots that are susceptible to fibrinolyisis. In this study we tested whether the combination of plasma derived activated prothrombin complex concentrate (pd-aPCC) with tranexamic acid (TXA) may improve fibrin clot stability in FVIII inhibitor plasma. A microplate assay for clot lysis time was used to assess clot stability in FVIII inhibitor plasma. The effect of pd-aPCC on clot stability was first tested using the commercial FVIII inhibitor plasma. TXA (5 ~ 10 mg mL⁻¹) increased clot lysis time, but pd-aPCC (0.25 ~ 1.0 U mL⁻¹) had no effect on it. The combination of pd-aPCC and TXA significantly increased clot lysis time compared with TXA alone. The effect appeared to be limited to fibrin clot resistance to fibrinolysis, as TXA was found to have no effect on thrombin generation induced by pd-aPCC. The effect of pd-aPCC and TXA on clot stability was then tested and verified in plasma samples from ten patients with severe haemophilia A and inhibitors. The combination of TXA (10 mg mL⁻¹) and pd-aPCC (0.5 U mL⁻¹) significantly increased clot lysis time compared to TXA alone. Our results suggest that the combination of pd-aPCC with TXA improves clot stability in FVIII inhibitor plasma without additional increases in thrombin generation.

Factor XIII combined with recombinant factor VIIa: a new means of treating severe hemophilia A

BACKGROUND

Abnormal thrombin generation is considered the key defect in hemophilia. Conventional treatment seeks to correct this using coagulation factor replacement or bypassing agents, for example recombinant factor VIIa (rFVIIa). Previous studies demonstrate abnormal FXIII activation in patients with hemophilia. FXIII activation is essential for formation of structurally normal, stable clots.

OBJECTIVES

The present study challenges the hypothesis that in hemophilia the use of plasma-derived FXIII (pdFXIII) in combination with rFVIIa will produce a greater improvement in clot stability than promotion of thrombin generation alone.

METHODS

Fourteen individuals with severe hemophila A were enrolled. Whole blood was spiked ex vivo with buffer, rFVIIa (2 μg mL(-1)) or rFVIIa (2 μg mL(-1)) plus pdFXIII (10 μg mL(-1)). Whole blood thromboelastometry assessed clot stability, after activation with tissue factor (TF) (0.15 pm) plus tissue-type plasminogen activator (tPa) (2 nm). The primary outcome measure of clot stability was area under the elasticity curve (AUEC).

RESULTS

The combination of pdFXIII and rFVIIa significantly improved clot stability as measured by AUEC (P < 0.05) compared with rFVIIa alone.

CONCLUSION

The use of pdFXIII resulted in superior clot stability compared with solely enhancing thrombin generation and we suggest that increasing thrombin generation alone fails to fully correct dysregulation of clot-stabilizing mechanisms associated with bleeding disorders. Hemorrhage control in hemophilia may be improved using clot stabilizing drugs. FXIII shows potential as a novel agent.

Clinical benefit of recombinant factor VIIa in management of bleeds and surgery in two brothers suffering from the Bernard-Soulier syndrome

Bernard-Soulier syndrome (BSS) is a rare congenital bleeding disorder characterized by thrombocytopenia and giant platelets that display impaired or absent platelet agglutination with ristocetin. The disease is caused by mutations in genes controlling the expression of the platelet glycoprotein Ib-IX complex. The most severely affected patients suffer from profound muco-cutaneous bleeding tendency. Patients suffering from BSS may require platelet transfusion in prevention and management of severe bleeding. However, recent publications have suggested that recombinant factor VIIa (rFVIIa) infusion may support haemostasis in BSS. The present report describes two brothers who received treatment with rFVIIa together with tranexamic acid on a total of six occasions in management of haemostasis in minor surgery and for a serious spontaneous upper gastrointestinal tract bleed. Although platelet transfusion was omitted, haemostasis was regarded excellent in all of these treatment episodes.

Whole blood thrombelastographic coagulation profiles using minimal tissue factor activation can display hypercoagulation in thrombosis‐prone patients

OBJECTIVE

Recently, our laboratory devised a dynamic whole blood (WB) thrombelastographic coagulation model employing activation with minute amounts of tissue factor. A series of studies were conducted to validate the feasibility of the model to illustrate hypocoagulation in various bleeding disorders and its usefulness in detecting the haemostatic effect of pro-coagulants by ex vivo titration experiments. In this context, the present study hypothesized that the thrombelastographic model also can reveal hypercoagulation. Hence, the objective of the present study was to record dynamic WB coagulation profiles in a series of patients (n=76) who had previously suffered from a venous (n=34) or arterial (n=42) thrombo-embolic event and to compare the results with those of a group of healthy reference subjects (n=60).

MATERIAL AND METHODS

Patients receiving vitamin K antagonist treatment were not enrolled in the study. Forty-four of the patients had no known thrombophilia risk factor and 32 patients had at least one thrombophilia risk factor.

RESULTS

The most commonly found risk factors were mild hyperhomocysteinaemia and heterozygosity for the factor V Leiden polymorphism. The data showed that, as compared with the healthy controls, patients with a history of venous or arterial thromboembolism had a significantly greater hypercoagulant WB coagulation clot signature as defined by a shortened clotting time together with an accelerated maximum velocity of clot propagation.

CONCLUSIONS

In future studies with ex vivo dose titration assessment of pro-coagulant components mixed with blood from a patient suffering from compromised haemostasis, observation of a significantly shortened clot initiation concomitant with a distinctly accelerated clot propagation is likely to indicate an increased risk of thrombosis.

Mechanisms of hydroxyethyl starch-induced dilutional coagulopathy

BACKGROUND

The biochemical mechanisms causing dilutional coagulopathy following infusion of hydroxyethyl starch 130/0.4 (HES) are not known in detail.

OBJECTIVES

To give a detailed biochemical description of the mechanism of coagulopathy following 30%in vivo dilution with HES, to present a systematic ex vivo test of various hemostatic agents, and to investigate the hypothesis that acquired fibrinogen deficiency constitutes the most important determinant of the coagulopathy.

METHODS

Dynamic whole blood clot formation assessed by thromboelastometry, platelet count, thrombin generation, and the activities of von Willebrand factor, coagulation factor II, FVII, FVIII, FIX, FX and FXIII were measured in 20 bleeding patients enrolled in a prospective clinical study investigating in vivo substitution of blood loss with HES up to a target level of 30%. Thromboelastometry parameters were further evaluated after ex vivo spiking experiments with fibrinogen, prothrombin complex concentrate (PCC), FXIII, activated recombinant FVIIa (rFVIIa), fresh frozen plasma, and platelets.

RESULTS

Hemodilution reduced maximum clot firmness (MCF), whereas whole blood clotting time (CT) and maximum velocity remained unaffected. All coagulation factor activities were reduced. Fibrinogen, FII, FXIII and FX activities decreased significantly below the levels expected from dilution. The endogenous thrombin potential was unchanged. Ex vivo addition of fibrinogen normalized the reduced MCF and increased the maximum velocity, whereas PCC, rFVIIa and platelets shortened the CT but showed no effect on the reduced MCF.

CONCLUSIONS

Acquired fibrinogen deficiency seems to be the leading determinant in dilutional coagulopathy, and ex vivo addition corrected the coagulopathy completely.

A community-based long-term follow up of women undergoing obstetric fistula repair in rural Ethiopia

OBJECTIVES

To assess urinary and reproductive health and quality of life following surgical repair of obstetric fistula.

DESIGN

Follow-up study.

SETTING

A newly established fistula clinic (2004) at Gimbie Adventist Hospital, a 71-bedded district general hospital in West Wollega Zone, in rural Western Ethiopia.

POPULATION

Thirty-eight women (86%) of 44 who had undergone fistula repair were identified in their community.

METHODS

Community-based structured interviews 14-28 months following fistula repair, using a customised questionnaire addressing urinary health, reproductive health and quality of life.

MAIN OUTCOME MEASURES

Urinary health at follow up was assessed as completely dry, stress or urge incontinence, or fistula. King's Health Questionnaire was modified and used for the quality-of-life assessment.

RESULTS

At follow up, 21 women (57%) were completely dry, 13 (35%) suffered from stress or urge incontinence and three (8%) had a persistent fistula. Surgery improved quality of life and facilitated social reintegration to a level comparable to that experienced before fistula development for both women who were dry and those with residual incontinence (P = 0.001). For women still suffering from fistula no change was seen (P = 0.1). Four women became pregnant following their surgery, among which there was one maternal death, three stillbirths and one re-occurrence of fistula.

CONCLUSION

Community-based, long-term follow up after fistula repair succeeded in Western rural Ethiopia. Despite one-third still suffering stress or urge incontinence, the women reported improved quality of life and social reintegration after fistula closure.

Fibrinogen substitution improves whole blood clot firmness after dilution with hydroxyethyl starch in bleeding patients undergoing radical cystectomy: a randomized, placebo-controlled clinical trial

SUMMARY BACKGROUND

Infusion of artificial colloids such as hydroxyethyl starch (HES) induces coagulopathy to a greater extent than simple dilution. Several studies have suggested that the coagulopathy could be corrected by substitution with a fibrinogen concentrate.

OBJECTIVES

The aims of the present prospective, randomized, placebo-controlled trial were to investigate the hemostatic effect of a fibrinogen concentrate after coagulopathy induced by hydroxyethyl starch in patients experiencing sudden excessive bleeding during elective cystectomy.

METHODS

Twenty patients were included. Blood loss was substituted 1:1 with HES 130/0.4. At a dilution level of 30%, patients were randomly selected for intra-operative administration of a fibrinogen concentrate or placebo. The primary endpoint was maximum clot firmness (MCF), as assessed by thromboelastometry. Secondary endpoints were blood loss and transfusion requirements, other thromboelastometry parameters, thrombin generation and platelet function.

RESULTS

Whole-blood MCF was significantly reduced after 30% dilution in vivo with HES. The placebo resulted in a further decline of the MCF, whereas randomized administration of fibrinogen significantly increased the MCF. Furthermore, only 2 out of 10 patients randomly chosen to receive fibrinogen substitution required postoperative red blood cell transfusions, compared with 8 out of 10 in the placebo group (P = 0.023). Platelet function and thrombin generation were reduced after 30% hemodilution in vivo, and fibrinogen administration caused no significant changes.

CONCLUSIONS

During cystectomy, fluid resuscitation with HES 130/0.4 during sudden excessive bleeding induces coagulopathy that shows reduced whole-blood maximum clot firmness. Randomized administration of fibrinogen concentrate significantly improved maximum clot firmness and reduced the requirement for postoperative transfusion.

Recombinant factor VIIa and fibrinogen display additive effect during in vitro haemodilution with crystalloids

BACKGROUND

Major blood loss requires fluid resuscitation for maintaining hemodynamic stability. Excessive volume infusions predispose to dilutional coagulopathy through loss, consumption and dilution of cells and proteins involved in haemostasis. Further treatment with fibrinogen concentrate and/or recombinant activated factor VII (rFVIIa) may be initiated, although the haemostatic effects in a situation with haemodilution are not fully detailed. The present study evaluates haemostatic effect of fibrinogen and rFVIIa and their combination in an in vitro model of haemodiluted whole blood with two commonly used crystalloids.

METHODS

Eight healthy, male volunteers were enrolled. Outcome variables were clot initiation, propagation and strength assessed by thrombelastographic parameters: clotting time, clot formation time, maximum velocity, time until maximum velocity, maximum clot firmness evaluated at dilution levels of 0% (control), 10%, 30% and 50% with isotonic saline and Ringer's lactate in a model of tissue factor-activated whole blood. Fibrinogen and rFVIIa were additional final reaction concentrations, reflecting commonly used clinically therapeutic dosages.

RESULTS

Dose-dependent coagulopathy developed following haemodilution with isotonic saline and Ringer's lactate, characterised by a prolonged clot initiation, reduced clot propagation and reduced clot strength. Fibrinogen improved clot strength and propagation phase while rFVIIa shortened clot initiation, both with a positive dose dependency.

CONCLUSIONS

The combination of fibrinogen and rFVIIa displays an additive effect and improves overall in vitro whole blood clot formation in a model of in vitro crystalloid-induced haemodilution.

Fibrinogen concentrate substitution therapy in patients with massive haemorrhage and low plasma fibrinogen concentrations

BACKGROUND

Patients experiencing massive haemorrhage are at high risk of developing coagulopathy through loss, consumption, and dilution of coagulation factors and platelets. It has been reported that plasma fibrinogen concentrations may reach a critical low level relatively early during bleeding, calling for replacement fibrinogen therapy. Cryoprecipitate has been widely used in the past, but more recently, a pasteurized fibrinogen concentrate has become available. We audited the effects of fibrinogen concentrate therapy on laboratory and clinical outcome in patients with massive haemorrhage.

METHODS

We identified 43 patients over the previous 2 yr to whom a fibrinogen concentrate had been administered as treatment for hypofibrinogenaemia during serious haemorrhage. Platelet count, P-fibrinogen, activated partial thromboplastin time (APTT), prothrombin time (PT), D-dimer, and volume of blood lost were obtained from medical and laboratory records. Numbers of units of red blood cells (RBC), fresh frozen plasma (FFP), and pooled platelet concentrates were recorded before and after fibrinogen substitution.

RESULTS

A significant increase in plasma fibrinogen concentration was observed after fibrinogen concentrate therapy. Platelet counts and fibrin D-dimer values remained unchanged, whereas the APTT and PT improved significantly. Requirements for RBC, FFP, and platelets were significantly reduced. Blood loss decreased significantly.

CONCLUSIONS

Off-label substitution therapy with a fibrinogen concentrate generally improved global laboratory coagulation results and as supplementary intervention, appeared to diminish the requirements for RBC, FFP, and platelet substitution in this patient cohort.

Tranexamic acid combined with recombinant factor VIII increases clot resistance to accelerated fibrinolysis in severe hemophilia A

BACKGROUND

Most patients with severe hemophilia A suffer from a profoundly compromised hemostatic response. In addition to both the delayed and slow development of a clot, previous studies have documented that severe hemophilia A is also associated with reduced clot stability.

OBJECTIVES

We examined whether the clot stability in hemophiliacs could be improved by treatment with tranexamic acid (TXA) in combination with recombinant factor VIII (rFVIII).

PATIENTS/METHODS

Baseline blood samples were obtained from eight males with severe hemophilia A. Thereafter, a bolus injection of rFVIII was administered to increase the functional level of FVIII to approximately 50%. After 10 min, blood was collected followed by an intravenous injection of TXA. A third blood sample was obtained after a further 10 min. Whole blood clotting profiles were determined by thrombelastography using minimal tissue factor activation. Clot formation was assessed by both clot initiation and clot propagation. At clot termination, the maximum clot firmness and area under the elasticity curve were used to illustrate clot stability. Tissue-plasminogen activator was included in those experiments designed to assess clot stability.

RESULTS

As expected, rFVIII increased clot formation, whereas TXA had no effect upon this parameter. Assays including tissue-plasminogen activator revealed that rFVIII increased the maximum clot firmness 3-fold; whereas the presence of TXA induced an additional 4-fold increase. The area under the elasticity curve increased 5-fold after rFVIII and 24-fold after addition of TXA.

CONCLUSIONS

The study demonstrates that simultaneous treatment with TXA and rFVIII significantly improves the clot stability in patients with hemophilia A.

Validation of the PHEEM instrument in a Danish hospital setting

The Postgraduate Hospital Educational Environment Measure (PHEEM) has been translated into Danish and then validated with good internal consistency by 342 Danish junior and senior hospital doctors. Four of the 40 items are culturally dependent in the Danish hospital setting. Factor analysis demonstrated that seven items are interconnected. This information can be used to shorten the instrument by perhaps another three items.

Use of 360-degree assessment of residents in internal medicine in a Danish setting: a feasibility study

BACKGROUND

The aim of the study was to explore the feasibility of 360 degree assessment in early specialist training in a Danish setting. Present Danish postgraduate training requires assessment of specific learning objectives. Residency in Internal Medicine was chosen for the study. It has 65 learning objectives to be assessed. We considered 22 of these suitable for assessment by 360-degrees assessment.

METHODS

Medical departments of six hospitals contributed 42 interns to the study. Each resident was assessed by ten persons of whom one was a secretary, four were nurses and five senior doctors. The assessors spent 14.5 minutes (median) to fill in the forms.

RESULTS

Of the 22 chosen objectives, 15 could reliably be assessed by doctors, 7 by nurses and none by secretaries.

CONCLUSIONS

The method was practical in busy clinical departments and was well accepted by the assessors. Reliability of the method was acceptable. It discrimintated satisfactorily between the good and not so good performers.

New approaches for measuring coagulation

Although specific assays of coagulation factors are essential for diagnostic purposes they only give partial information about an individual's haemostatic state. This can be better assessed by various global tests, and recent developments and evaluations of five such tests are described in this symposium: the PFA-100; waveform analysis; thrombin generation; overall haemostasis potential; thrombelastography. Each test has advantages in various applications, but the thrombin generation test and waveform analysis have been found most useful in haemophilia, whilst the PFA-100 is helpful in von Willebrand's disease.

Acquired haemophilia: dynamic whole blood coagulation utilized to guide haemostatic therapy

Acquired haemophilia is a rare bleeding disorder caused by autoimmune antibodies interacting with factor VIII (FVIII) or factor IX. Anticipating a high degree of heterogeneity amongst cases, we recently initiated systematic recording of whole blood (WB) coagulation dynamic profiles using our recently developed thrombelastographic method employing very small amounts of tissue factor for activation. Six newly diagnosed patients with acquired haemophilia A in our University Hospital were investigated with the purpose to characterize the WB clotting phenotypes in each patient, as well as inspecting the ex vivo and in vivo response to supplementation with various haemostatic agents. Our results show a striking heterogeneity in patients WB clotting profiles, each patient having a particular pattern and an individual type of response to bypassing agents. Profiles in some of patients resembled severe haemophilia A, even if there was a measurable residual FVIII:C activity while others were more similar moderate-to-mild haemophilia. In one case the profile was very close to normal. Each patient seemed to respond individually to bypassing agents. WB clotting profiles assisted us in selecting an optimal treatment modality in each case and whenever possible, we compared the clinical effects of the treatment selected with the appearance of the WB clotting pattern. In one patient, the ex vivo response to FVIII looked promising, and a approximately 200 IU kg-1 per 24 h high-dose programme nearly normalized the clotting profile in 2-week time. Our preliminary small series of data should be concluded with caution. However, it seems that WB clotting profile studies at baseline, with ex vivo addition of haemostasis promoting agents, and during treatment may hold the potential to predict the success of treatment.

Tailoring haemostatic treatment to patient requirements - an update on monitoring haemostatic response using thrombelastography

Currently, there is no single haemostasis laboratory test that has the capacity to accurately illustrate the clinical effects of procoagulant or anticoagulant interventions. Although the time course of thrombin generation in plasma and the endogenous thrombin potential (ETP) may be useful coagulation parameters, clotting involves components other than thrombin (e.g. platelets, fibrinogen). The continuous coagulation profiles of thrombelastography may provide a more accurate reflection of in vivo biology, covering initiation, development and final clot strength during whole blood clot formation. This method has helped to clarify the mechanism of action of whole blood clot formation, demonstrating the differences from clotting in plasma, and the importance of platelets and tissue factor titrations. It has also been used to investigate hypocoagulation (in haemophilia A, rare coagulation disorders, anticoagulant therapy and dilutional coagulopathy), hypercoagulation and the ex vivo testing of haemostatic interventions. Thrombelastography has been shown to reflect the clinical efficacy of activated prothrombin complex concentrate (aPCC) and recombinant activated factor VII (rFVIIa) in patients with haemophilia A with inhibitors and in patients with acquired haemophilia. Overall, tailoring laboratory assays to illustrate and correlate with clinical phenotypes is essential for effective coagulation monitoring. Applying an algorithm of preoperative, perioperative and postoperative tests, including thrombelastography, may enable physicians to achieve this.

Thrombelastographic whole blood clot formation after ex vivo addition of plasma substitutes: improvements of the induced coagulopathy with fibrinogen concentrate

BACKGROUND

Plasma substitutes such as hydroxyethyl starch (HES) and various dextrans may compromise the haemostatic system, thereby causing potentially dangerous bleeding. Whilst several mechanisms have been advanced to explain the nature of the coagulopathy induced by this colloid, there has been comparably little interest in devising ways to optimize haemostasis after a relative colloid overdose.

METHODS

Real-time whole blood (WB) clot formation profiles were recorded using a thrombelastographic method employing activation with tissue factor. The coagulation tracings were transformed into dynamic velocity profiles of WB clot formation. WB from healthy individuals (n=20) was exposed to haemodilution of approximately 55% with isotonic saline, HES 200/0.5, HES 130/0.4, and dextran 70, respectively. Possible modalities for improvement of the induced coagulopathy were explored, in particular ex vivo addition of a fibrinogen concentrate.

RESULTS

WB coagulation profiles changed significantly with decreased clot strength, and a compromised propagation phase of clot formation. The duration of the initiation phase of WB coagulation was unchanged. No statistical differences were detected amongst the HES solutions and dextran 70. However, dextran 70 returned a more suppressed clot development and strength compared with the HES solutions. Ex vivo haemostatic addition of washed platelets (75 x 10(9) litre(-1)) and factor VIII (0.6 IU ml(-1)) produced insignificant changes in clot initiation, propagation, and in the clot strength. In contrast, ex vivo addition of a fibrinogen concentrate (1 g litre(-1)) improved the coagulopathy induced by all of the three individual plasma expanders tested.

CONCLUSION

Coagulopathy induced by haemodilution with either HES 200/0.5, HES 130/0.4, and dextran 70 may be improved by fibrinogen supplementation.