Hydroxyethyl starch induced acquired von Willebrand's disease

Acquired von Willebrand Syndrome

Acquired von Willebrand syndrome can occur in the setting of myeloproliferative neoplasms; plasma cell dyscrasias and other lymphoproliferative disorders; autoimmune conditions; and causes of increased shear forces, such as aortic stenosis or other structural heart disease and mechanical circulatory support. The depletion of von Willebrand factor, especially high-molecular-weight multimers, can lead to mucocutaneous bleeding and the formation of arteriovenous malformations, particularly in the gastrointestinal tract. Management focuses on correction of the underlying cause when possible, but may include intravenous immunoglobulins, von Willebrand factor concentrate, rituximab, or antiangiogenic therapy depending on the clinical context.

Synthetic colloid resuscitation in severely injured patients: analysis of a nationwide trauma registry (TraumaRegister DGU)

The purpose of this study was to investigate the efficacy and safety of synthetic colloid resuscitation among severely injured patients. Fluid resuscitation of trauma patients of a nationwide trauma registry was analysed between 2002 and 2015. Effects of synthetic colloid resuscitation in the pre-hospital setting and emergency department on renal failure, renal replacement therapy and multiple organ failure were analysed among patients with ≥2 days intensive care unit stay, and in-hospital mortality was analysed among all patients. 48,484 patients with mean age of 49 years and mean injury severity score of 23 points were included; 72.3% were male and 95.5% had blunt trauma. Risk-adjusted analyses revealed that patients receiving >1,000 ml synthetic colloids experienced an increase of renal failure and renal replacement therapy rates (OR 1.42 and 1.32, respectively, both p ≤ 0.006). Any synthetic colloid use was associated with an increased risk of multiple organ failure (p < 0.001), but there was no effect on hospital mortality (p = 0.594). Between 2002 and 2015 usage of synthetic colloids dropped, likewise did total fluid intake and usage of blood products. The data from this analysis suggests that synthetic colloid resuscitation provides no beneficial effects and might be harmful in patients with severe trauma.

[Fluid resuscitation in hemorrhage]

How fluid resuscitation has to be performed for acute hemorrhage situations is still controversially discussed. Although the forced administration of crystalloids and colloids has been and still is practiced, nowadays there are good arguments that a cautious infusion of crystalloids may be initially sufficient. Saline should no longer be used for fluid resuscitation. The main argument for cautious fluid resuscitation is that no large prospective randomized clinical trials exist which have provided evidence of improved survival when fluid resuscitation is applied in an aggressive manner. The explanation that no positive effect has so far been observed is that fluid resuscitation is thought to boost bleeding by increasing blood pressure and dilutional coagulopathy. Nevertheless, national and international guidelines recommend that fluid resuscitation should be applied at the latest when hemorrhage causes hemodynamic instability. Consideration should be given to the fact that damage control resuscitation per se will neither improve already reduced tissue perfusion nor hemostasis. In acute and possibly rapidly progressing hypovolemic shock, colloids can be used. The third and fourth generations of hydroxyethyl starch (HES) are safe and effective if used correctly and within prescribed limits. If fluid resuscitation is applied with ongoing re-evaluation of the parameters which determine oxygen supply, it should be possible to keep fluid resuscitation restricted without causing undesirable side effects and also to administer a sufficient quantity so that survival of patients is ensured.

Pathophysiology of acquired von Willebrand disease: a concise review

Acquired von Willebrand disease (AVWD) is a rare, underdiagnosed hemorrhagic disorder, which is similar to congenital VWD with regard to the clinical and laboratory parameters; however, it is found in individuals with no positive family history and has no genetic basis. The etiology is varied, the commonest being hematoproliferative disorders and cardiovascular disorders. Other disorders associated with AVWD are autoimmune disorders such as systematic lupus erythematosus, hypothyroidism, and neoplasia, or it may also be drug induced. In quite a few cases, the etiology is unknown. The pathogenic mechanisms are different in different underlying disorders or they may be overlapping among these disorders. Some of the proposed mechanisms include the development of autoantibodies, selective absorption of high molecular weight von Willebrand factor (VWF) multimers, non-selective absorption of VWF, mechanical destruction of VWF under high shear stress, and increased proteolysis. This report presents a concise review of the pathophysiological mechanisms of AVWD in these various underlying conditions.

The Role Of von Willebrand Factor In Hemorrhagic And Thrombotic Disorders

von Willebrand factor (VWF) is a multimeric plasma protein that mediates platelet adhesion as well as platelet aggregation at sites of vascular injury and acts as a carrier of factor VIII. Although acquired or inherited VWF deficiency is associated with a bleeding tendency, there is increasing evidence that VWF has a pivotal role in thrombogenesis. In fact, while the presence in the plasma of unusually large VWF multimers, due to a congenital or acquired deficiency of a VWF-cleaving metalloprotease, has been implicated in the pathogenesis of thrombotic thrombocytopenic purpura, high plasma levels of VWF have been associated with an increased risk of both arterial and venous thrombosis. The role of VWF in normal and pathological hemostasis is discussed in this review, and important advances in the pathophysiology, diagnosis, and treatment of VWF-associated disorders are also described.

Acquired von Willebrand syndrome: an update

Acquired von Willebrand syndrome (aVWS) is a rare bleeding disorder with laboratory findings similar to those for congenital von Willebrand disease (VWD). However, unlike congenital VWD, it arises in individuals with no personal or family history of bleeding. aVWS occurs in association with a variety of underlying disorders, most frequently in lymphoproliferative disorders, myeloproliferative disorders, and cardiovascular diseases. Through an analysis of the more recent literature data, the pathophysiology and the clinical, laboratory, and therapeutic aspects of this syndrome are concisely reported in this review.

Recent acquisitions in acquired and congenital von Willebrand disorders

von Willebrand factor is a multimeric plasma protein that mediates platelet adhesion as well as platelet aggregation at sites of vascular injury and, moreover, acts as a carrier of factor VIII. Its deficiency is associated with a bleeding tendency. The progresses in the pathophysiology, diagnosis and management of inherited von Willebrand disease and acquired von Willebrand syndrome will be discussed in this review.

Acquired von Willebrand syndrome: features and management

Acquired von Willebrand syndrome (AvWS) is not a well-known bleeding disorder among clinicians and is associated with various underlying diseases. The clinical manifestations are similar to congenital von Willebrand disease. Diagnosis is confirmed mainly by a decrease of ristocetin cofactor activity (vWF:RCo) and/or collagen binding activity (vWF:CBA) and by vWF multimeric analysis, usually with a selective loss of large multimers. Plasma von Willebrand factor propeptide (vWF:AgII) is a good marker of vWF synthesis. Various pathogenic mechanisms have been proposed, including development of autoantibodies to the von Willebrand factor (vWF), adsorption of vWF onto tumor cells or activated platelets, increase of vWF proteolysis, and mechanical destruction of vWF under high shear stress. Treatment of the underlying disorder may resolve AvWS. Desmopressin (DDAVP) is a first-line therapeutic option. Factor VIII/vWF concentrates and high-dose immunoglobulin infusions are reserved for patients unresponsive to DDAVP.

Acquired von Willebrand Syndrome: An Underdiagnosed and Misdiagnosed Bleeding Complication in Patients With Lymphoproliferative and Myeloproliferative Disorders

Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder with laboratory findings similar to those for congenital von Willebrand disease (VWD). Unlike the congenital disease, AVWS usually occurs in individuals with no personal or family history of bleeding. The prevalence of AVWS in the general population is unknown because data from large prospective studies of this syndrome are not available. Although AVWS is particularly frequent in lymphoproliferative or myeloproliferative disorders, it can also be associated with solid tumors, immunologic and cardiovascular disorders, and other miscellaneous conditions. Diagnosis of AVWS is based on assays measuring the activity of von Willebrand factor (VWF). This tends to be abnormally low, but factor VIII (FVIII) coagulant activity can sometimes be normal. FVIII/VWF inhibiting activity is found in only a minority of cases. Bleeding episodes in patients with AVWS are mostly of the mucocutaneous type and can be managed with desmopressin, plasma-derived FVIII/VWF concentrates, and intravenous immunoglobulin (IVIg). Recombinant activated factor VII can be useful in patients unresponsive to standard therapy. An updated version of the International Registry on AVWS, recently available online, will provide more information on this rare, but underdiagnosed and misdiagnosed, disorder.

Use of Intravenous Immunoglobulin in Patients With Acquired von Willebrand Syndrome

Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder with laboratory findings similar to those for congenital von Willebrand disease. Unlike the congenital form, AVWS usually occurs in individuals with no personal or family history of bleeding disorders. According to an international registry, AVWS is mainly associated with lymphomyeloproliferative, immunologic, and cardiovascular disorders, as well as with solid tumors and other miscellaneous conditions; however, the prevalence of AVWS in these underlying disorders is still unknown. von Willebrand factor (VWF) is synthesized normally in most AVWS patients, and the low plasma VWF levels are from its accelerated removal from plasma by five different mechanisms, including autoantibodies. Because of the reduced half-life of endogenous-exogenous plasma VWF, bleeding of AVWS cannot be managed with desmopressin or factor VIII/VWF concentrates. Clinical use of intravenous immunoglobulin (IVIg) in AVWS has been reported since 1988. IVIg is most effective in AVWS with type immunoglobulin (Ig) G monoclonal gammopathies of undetermined significance and in other cases with IgG autoantibodies. IVIg can correct factor VIII and von Willebrand factor complex activities for about 15-20 days, and repeated injections induce remission of AVWS in these patients. Prospective studies are required to evaluate the efficacy and safety of IVIg in AVWS.

Management of hemodynamic changes associated with removal of a large abdominal myofibroblastic tumor in a pony

A 22-year-old female Welsh-cross pony was evaluated because of intermittent colic, signs of depression, pyrexia, anorexia, muscle wasting with abdominal distention, and weight gain over the preceding 12 months. A large abdominal mass was detected and surgically removed; the hemodynamic alterations and complications caused by the dramatic fluid losses and shifts that can occur in association with removal of a large abdominal mass required extensive postoperative management. Monitoring of clinical and hematologic variables such as attitude, heart rate, mucous membrane color, mean arterial blood pressure, PCV, and plasma total protein concentration provided useful information for successful management of the patient after surgery. On removal, the tumor weighed 19% of the pony's body weight and was characterized as a myofibroblastic tumor. Myofibroblastic tumors should be considered as a differential for large internal abdominal masses in horses, and surgical removal may be feasible and life extending with appropriate postoperative care.

[Effects of plasma substitutes on hemostasis]

OBJECTIVE

Data synthesis on haemostasis effects of cristalloids and colloids and clinical implications for their use for plasma volume replacement.

DATA SOURCES

Data were searched in the Medline database from 1954 to 2000 using the following key-words: cristalloids, colloids, albumin, gelatin, dextran, hydroxyethyl starch, haemostasis, von Willebrand disease, haemodilution.

DATA EXTRACTION

Publications from 1954 to 1990 were selected depending on the quality of their methodology. Most of articles published after 1990 and all types including case report were accepted.

DATA SYNTHESIS

Cristalloids induces a moderate hypercoagulable state with 10 to 30% haemodilution. Hypocoagulation is observed above 50% haemodilution. Albumin does not impair hemostasis except with a 50% or more haemodilution where hypocoagulation is observed. Dextran dramatically impairs haemostasis and fibrinolysis. With increasing dose, a progressive decrease of all von Willebrand multimers, mostly the largest, is observed. Till 50% haemodilution, gelatin has a moderate impact on hemostasis, but platelet aggregation is moderately modified. However this moderate impairment of haemostasis may potentiate the haemostatic effect of other colloids when used in association with gelatin. More than 30% haemodilution with hydroxyethyl starch (HES) has a serious effect in vitro on platelet function and fibrinoformation. In most studies in human, less than 20 ml.kg-1 plasma volume replacement has no clinical impact, but in some evaluations postoperative bleeding is more important with HES, particularly HES 450, in comparison to other colloids. With HES 450 and HES 200 highly substituted (0.6 of degree of substitution) intravascular cumulation of large molecules leads to type I von Willebrand syndrome when doses overtake 80 ml.kg-1. Dextran and HES are prohibited in patients with impaired haemostasis due to congenital disease (haemophilia and von Willebrand disease) or acquired defect (thrombocytopenia). Caution is required in patients with renal failure or receiving antithrombotic or non-steroidal anti-inflammatory agents. Patients without a haemorrhagic diathesis must not received more than 1.5 g.kg-1.j-1 of dextran and restrictive conditions of use must be respected with HES.

CONCLUSION

Except isotonic cristalloids, all colloids induce haemostastic changes particularly for haemodilution over 30%. Effects are more pronounced with HES and dextran.

Fluid Therapy in the Critically Ill Patient

The administration of intravenous fluids in the critically ill patient presents many challenges for clinicians. Intravenous fluids are usually categorized as either crystalloids or colloids, with each having distinct advantages and disadvantages in various patient populations. The appropriate selection of fluid type remains an issue of great debate in the critical care literature and has been the subject of numerous comparative studies. Despite the vast amount of data available, there is no clear consensus in the literature to direct the clinician in the choice of fluid type. This article will provide an overview of fluid distribution within the body and the factors that affect this distribution, a review of the various types of fluids administered in the critically ill patient, and the rationale for the selection of each type. A review of the literature surrounding the colloid-crystalloid controversy is provided.

Acquired von Willebrand disease

Acquired von Willebrand disease (AvWD) is a relatively rare acquired bleeding disorder that usually occurs in elderly patients, in whom its recognition may be delayed. Patients usually present predominantly with mucocutaneous bleeding, with no previous history of bleeding abnormalities and no clinically meaningful family history. Various underlying diseases have been associated with AvWD, most commonly hematoproliferative disorders, including monoclonal gammopathies, lymphoproliferative disorders, and myeloproliferative disorders. The pathogenesis of AvWD remains incompletely understood but includes autoantibodies directed against the von Willebrand factor (vWF), leading to a more rapid clearance from the circulation or interference with its function, adsorption of vWF by tumor cells, and nonimmunologic mechanisms of destruction. Laboratory evaluation usually reveals a pattern of prolonged bleeding time and decreased levels of vWF antigen, ristocetin cofactor activity, and factor VIII coagulant activity consistent with a diagnosis of vWD. Acquired vWD is distinguished from the congenital form by age at presentation, absence of a personal and family history of bleeding disorders, and, often, presence of a hematoproliferative or autoimmune disorder. The severity of the bleeding varies considerably among patients. Therapeutic options include desmopressin and certain factor VIII concentrates that also contain vWF. Successful treatment of the associated illness can reverse the clinical and laboratory manifestations. Intravenous immunoglobulins have also shown some efficacy in the management of AvWD, especially cases associated with monoclonal gammopathies. Awareness of AvWD is essential for diagnosis and appropriate management.

Rare acquired bleeding disorders

Accurate diagnosis of the cause of bleeding is a prerequisite for determination of the optimal therapeutic response. Clinicians are generally aware of the more prevalent hemorrhagic syndromes but some rare acquired conditions are also of importance. In many of these, inhibitors of coagulation factors or of platelet adhesion/aggregation cause bleeding. These inhibitors are generally, but not always, immunoglobulins. In this review, the less common inhibitors of coagulation and hemostasis, as well as some important but rare nutritional, iatrogenic and disease associated hemorrhagic disorders, are described.

Acquired von Willebrand syndromes: clinical features, aetiology, pathophysiology, classification and management

Acquired von Willebrand syndrome (AVWS) associated with hypothyroidism is of type I, results from a decreased synthesis of factor VIII and von Willebrand factor (VWF), responds to desmopressin with normal half-life times for factor VIII and VWF parameters, and disappears after treatment with I-thyroxine. AVWS type I or III, which occurs in a minority of patients with Wilms' tumour in the complete absence of an inhibitor against VWF and no absorption of factor VIII or VWF onto nephroblastoma cells, responds to chemotherapy and/or tumour resection. Hyaluronic acid produced by nephroblastoma cells may be the causative factor in atypical AVWS in Wilms' tumour. AVWS associated with thrombocythaemia of various myeloproliferative disorders is characterized by normal factor VIII and von Willebrand factor antigen (VWF: Ag) levels and a selective deficiency of functional ristocetin co-factor activity (VWF: RCo) and collagen-binding activity (VWF: CBA). AVWS type II in thrombocythaemia is caused by a platelet-dependent proteolysis of large VWF multimers, given the inverse relationship between platelet count and large VWF multimers in plasma and specific increases in the number of proteolytic VWF fragments in plasma. The laboratory findings of AVWS associated with systemic lupus erythematosus or IgG benign monoclonal gammopathy are characterized by a prolonged bleeding time and activated partial thromboplastin time, decreased or absent ristocetin-induced platelet activity, low to very low levels of factor VIII coagulant activity (mean 15%), VWF: Ag (mean 10.7%) and VWF: RCo (mean 6.2%), and a type II multimeric pattern of VWF. Neutralizing and non-neutralizing anti-VWF autoantibodies, usually IgG, have been detected in patient plasma either free or tightly bound to the intermediate and high molecular weight VWF factor VIII particles. The bound auto antibody-antigen complex is rapidly cleared from the circulation, resulting in low levels of factor VIII, VWF parameters as documented by a poor response to desmopressin and VWF factor VIII concentrate. High-dose intravenous immunoglobulin transiently corrects the factor VIII coagulant and VWF levels, lasting for a few weeks in AVWS type II associated with systemic lupus erythematosus or IgG benign monoclonal gammopathy. Prednisolone is effective in AVWS associated with autoimmune disorder. Prednisolone and chemotherapy will not affect AVWS associated with IgG benign monoclonal gammopathy because the monoclonal IgG protein remains to act as an anti-VWF autoantibody. An absorption of VWF to malignant cells has been documented in a few patients with various lymphoproliferative disorders or adrenal carcinoma and suggested to result in a depletion of VWF. The clinical picture of AVWS associated with early-stage IgG multiple myeloma, chronic lymphocytic leukaemia or non-Hodgkin's lymphoma without a paraprotein or no detectable underlying disorder is similar to that of AVWS type II in IgG benign monoclonal gammopathy but poorly documented with regard to the underlying immune mechanism of AVWS. The mechanical destruction of large VWF multimers may be of relevance in conditions in which the shear rate of flowing blood is increased, as may occur in cases of aortic stenosis, other heart valve defects or stenosed vessels. Drug-induced AVWS has been described in association with the use of pesticides valproic acid, ciprofloxacin, griseofulvin, tetracycline, thrombolytic agents and hydroxyethyl starch.

Effects of different plasma substitutes on blood coagulation: a comparative review

OBJECTIVE

To compare the effects of different colloid plasma substitutes on blood coagulation and postoperative blood loss.

DATA SOURCES

Relevant studies were obtained from the medical literature.

STUDY SELECTION

Articles were selected that provided data on the effects of colloids on hemostasis and postoperative blood loss in humans. Studies comparing different colloids were looked for using MEDLINE and by searching through the references of studies as they were collected.

DATA SYNTHESIS

Articles were reviewed and relevant data were extracted and partly presented in comparative tables.

CONCLUSIONS

Dextran, gelatin, and hydroxyethyl starch (HES) all can induce a specific decrease of von Willebrand factor and factor VIII:c. Blood coagulation is most impaired by dextran and high molecular weight HES, both associated with increased postoperative blood loss. The effects of HES on blood coagulation have been shown to depend on its molecular weight and rate of elimination. Detrimental effects have been shown for high molecular weight HES. Medium molecular weight (MMW)-HES with a high degree of substitution (HES 200/0.62) and MMW-HES with high C2/C6 hydroxyethylation ratio (HES 200/0.5/13) are slowly degradable and have been shown to impair blood coagulation after repeated administration. Rapidly degradable HES 200/0.5/6 and gelatin-based plasma expanders appear not to impair hemostasis. However, based on the reviewed literature, all artificial colloids could potentially induce increased bleeding tendency after infusion of very large volumes and especially when given to patients with even mild forms of von Willebrand disease. In those circumstances, crystalloid solutions or alternatives such as plasma or albumin, although associated with other serious complications, could be considered.

Microparticle-containing oncotic solutions augment in-vitro clot disruption by ultrasound

Echocardiographic contrast agents enhance blood clot disruption by ultrasound. It has been suggested that the microbubbles add nuclei for the enhancement of cavitation by ultrasound. However, microbubbles are rapidly destroyed by the ultrasound energy. We assessed whether non-gas filled colloidal solutions (hyperoncotic medium molecular hydroxyethyl starch and degraded gelatin polypeptides) will facilitate clot disruption by ultrasound. In two separate experiments human blood clots, 200-400 mg in weight, were weighed and then immersed for 15 seconds in 10 ml normal saline solution containing 0%, 0.1%, 1%, 2%, and 5% of hyperoncotic medium molecular hydroxyethyl starch or 0%, 0.035%, 0.175%, 0.35%, and 0.7% degraded gelatin polypeptides. Clots were randomized to 10 seconds 20 kHz ultrasound or immersion without ultrasound. After treatment, the clots were reweighed, and the percent difference in weight was calculated. Non-gas filled microparticle-containing solutions such as hyperoncotic medium molecular hydroxyethyl starch and degraded gelatin polypeptides significantly augmented blood clot disruption by ultrasound. The effect is dependent on the colloidal solution concentration with maximal effect achieved with 1% hyperoncotic medium molecular hydroxyethyl starch and 0.35% degraded gelatin polypeptides.

Therapeutic approaches to acquired von Willebrand syndrome

Acquired von Willebrand syndrome (AVWS) is a rare acquired bleeding disorder similar to the congenital von Willebrand disease (VWD) in terms of laboratory findings. Diagnosis of AVWS can be very difficult, with treatment normally taking an empirical form. Although more than 200 cases have been reported since 1968, no retrospective or prospective studies are available on AVWS. Recently, an International Registry on AVWS, gathering data directly from worldwide Departments of Haematology-Oncology and Haemophilia Centres, has been organised by a group working on behalf of the Subcommittee on VWF in the Scientific Standardisation Committee (SSC) of International Society on Thrombosis and Haemostasis (ISTH). Information about an additional 211 AVWS patients is now available, with more detailed data on demography, type of haemorrhage, diagnostic tests for AVWS and management of bleeding episodes. The additional 211 AVWS cases are associated with lymphoproliferative (47%) or myeloproliferative (19%) disorders, cardiovascular diseases, neoplasia (7%) and other miscellaneous diseases (14%). Bleeding episodes of AVWS patients were managed by different compounds including desmopressin (22%), FVIII/VWF concentrates (26%) and high-dose immunoglobulin (10%), plasmapheresis (2%), steroids (5%) and immunosuppressive drugs (20%). Based on complied data, we can conclude that none of the therapeutic approaches proposed are 100% effective in all AVWS cases. Therefore, treatment must be customized for each patient according to the underlying disorder, as well as to the type and the severity of bleeding episode and must be targeted to each specific case.

Acquired von Willebrand syndrome--report of 10 cases and review of the literature

Acquired von Willebrand syndrome (AvWS) is a rare bleeding disorder with clinical and laboratory features closely resembling hereditary von Willebrand disease (vWD), arising in previously haemostatically normal individuals. We present a retrospective review of 10 cases with AvWS diagnosed over 17 years. The severity of the bleeding tendency varied from mild to severe forms. Multimers electrophoresis showed that 8/10 patients had a normal pattern similar to type 1 vWD, 1/10 had a type 2A vWD pattern (with absence of high and intermediate molecular weight multimers) and 1/10 had a type 3 vWD pattern. An inhibitor screen was performed in 6/10 patients and autoantibodies against von Willebrand factor were found in only two cases. The underlying cause/associated conditions were identified in 8/10 patients. Treatment of the bleeding diathesis was successfully achieved with desmopressin or clotting factor concentrates. Resolution of underlying hypothyroidism (in two cases) and multiple myeloma (in one case) led to normalization of the coagulation parameters. The report on this cohort of 10 patients with AvWS illustrates the complexity of AvWS and its multifactorial aetiology. A brief review of the recent literature on AvWS is also presented, with emphasis on the current opinions in pathogenesis and treatment. Acquired von Willebrand syndrome (AvWS) is an acquired bleeding disorder, characterized by a phenotype similar to the inherited von Willebrand disease (vWD), with a prolonged bleeding time and low plasma levels of factor VIII - von Willebrand factor (vWF) measurements. It occurs in patients with no family history of vWD, who present with recent onset of bleeding symptoms. AvWS appears to be associated mainly with lymphoproliferative disorders, immunological conditions and neoplasia. AvWS is a rare condition and it is difficult to conduct prospective studies, therefore it is important to document the experience with such cases. The aim of this paper is first, to report 10 cases of AvWS identified at our Haemophilia Centre during the past 17 years. Second, to present a brief review of the recent literature on AvWS - outlining the salient features, associated disorders, mechanisms of acquisition and the available options of treatment.

Activity of blood coagulation and fibrinolysis during and after hydroxyethyl starch (HES) colloidal volume replacement

OBJECTIVES

To examine the effect of medium molecular weight hydroxyethyl starch on protein C levels and the changes in the activation state of blood platelets, coagulation and fibrinolyis during and after 5 day of its infusion.

DESIGN AND METHODS

Fifty male patients (mean age: 47 years, range 45-50 years) who required prostatectomy for benign prostatic hyperplasia were divided into two equal groups. One group was given 15 mL/kg body weight (mean volume 1000 mL +/- 100 mL) of 6% hydroxyethyl starch (HES) 200/0.5, the other received an equal volume of 5% human albumin during the operation. Blood samples were collected immediately before infusion (baseline values) and at 20, 40, 60, 90, 240, and 480 min after the infusion started then daily for the next 5 days postoperatively. Hematocrit, factor VIII:C, thrombin-antithrombin III complex; the anticoagulant protein C levels; the fibrinolytic parameters tissue type plasminogen activator (t-PA), and the fibrinolytic product D-Dimer and the platelet aggregation activity were measured.

RESULTS

The data obtained did not detect any significant differences between HES and human albumin in the plasma levels of thrombin-antithrombin III complex, protein C, tissue-type plasminogen activator and the fibrin split products D-Dimer. Factor VIII:C and platelet aggregation were significantly lower in the hydroxyethyl starch group in comparison with albumin. Baseline values were attained postoperatively for factor VIII:C and platelet aggregation by the first and fifth days, respectively.

CONCLUSION

The lowering effect of medium molecular weight hydroxyethyl starch on factor VIII:C would not be attributed to increased proteolytic activity of protein C on this coagulation cofactor because there is a nonsignificant change in protein C levels.

Peri-operative tolerance to large-dose 6% HES 200/0.5 in major urological procedures compared with 5% human albumin

We studied the long-term efficacy and safety of medium-molecular-weight hydroxyethyl starch (HES) administered in doses above 20 ml.kg-1 during major blood replacement therapy. Blood replacement for 50 patients used 6% HES 200/0.5 (HES group) or 5% albumin (ALB group) and additional blood components according to a defined protocol. We compared safety, efficacy and costs in 4 peri-operative days. Colloid administration on the day of surgery was 38.4 ml.kg-1 (HES group) and 35.1 ml.kg-1 (ALB group). Haemodynamic, coagulation and renal function parameters were similar. Although total serum protein was still different on the third postoperative day (53.45 gl-1 (HES group) and 60.6 gl-1 (ALB group) (p < 0.01)) the colloid osmotic pressure always remained above 19.5 (2.5) mmHg (HES group). Blood loss (3810 (1632) ml (HES group) and 3455 (1733) ml (ALB group)) and the requirement for blood components was comparable. Costs were reduced by 35% (p < 0.05) in the HES group. We conclude that using 6% HES 200/0.5 as the only colloid for treatment even of large blood loss is a safe and economic alternative to albumin.

[Hydroxethyl starch: effects on hemostasis]

HES are high-polymeric glucose compounds obtained via hydrolysis and subsequent hydroxyethylation from the highly-branched amylopectin contained in maize. Initially, the HES were only characterized by their in vitro molecular weight (Mw), without consideration of the in vivo hydrolysis by alpha-amylase. The degree of substitution and the molar substitution ratio quantify the hydroxyethylation. The glucose units can be substituted at carbon 2, 3 and 6 leading to various substitution patterns. This pattern is described with the C2/C6 hydroxyethylation ratio. The higher the degree of substitution and the C2/C6 ratio, the less the starch is metabolized. The in vitro Mw, the degree of substitution and the C2/C6 ratio are the main determinants of the in vivo Mw which is clinically relevant. Haemorrhagic complications that occur after infusing larger volumes of HES can be avoided with a starch of low in vivo Mw. This is not only due to a lesser effect on the coagulation system which prevents an acquired type I von Willebrand syndrome, but also to a smaller decrease in platelet volume, since platelet volume and platelet function are positively correlated. In addition, HES with low in vivo Mw has significantly better rheological effects than HES with a high in vivo Mw, as high Mw macromolecules affect plasma viscosity negatively. Furthermore high Mw HES macromolecules lead to a distinctive decrease in fibronectin concentration that reflects saturation of the reticuloendothelial system. Another advantage of low in vivo Mw HES is its rather short half-life. Patients with an increased bleeding risk, microcirculatory disturbance or affected RES should receive HES with low in vivo Mw. In the future, HES should be mainly characterized by the in vivo and not the in vitro Mw.

Acquired von Willebrand disease

Acquired von Willebrand disease (AvWD) is an acquired bleeding disorder which may suddenly become manifest in individuals, usually in the absence of a personal or family history of bleedings and frequently in association with monoclonal gammopathies, lymphoproliferative, myeloproliferative and autoimmune disorders. In a minority of the cases AvWD may develop in association with drugs or solid tumours. Pathogenetic mechanisms involve autoantibodies directed against von Willebrand factor (vWF) resulting in a rapid clearance of vWF from the circulation and/or inactivation of plasma vWF; absorption or adsorption of plasma vWF to malignant cells; drug-induced or cell-mediated proteolysis of plasma vWF; acquired decrease in synthesis of vWF and/or release of vWF from storage sites; or precipitation of plasma vWF. Treatment options include--whenever possible--treatment of the underlying disorder or symptomatic treatment aimed at replacing the loss of vWF by either infusion of vWF-rich concentrates or administration of desmopressin (DDAVP). In selected cases with anti-vWF antibodies, administration of high-dose intravenous gammaglobulin, plasma exchange or extracorporeal immunoadsorption may be successful.

Acquired von Willebrand disease: concise review of occurrence, diagnosis, pathogenesis, and treatment

Acquired von Willebrand disease (AvWD) is a rare complication of an autoimmune or neoplastic disease. It is associated mostly with a lymphoid or plasma cell proliferative disorder. The clinical manifestations are similar to congenital von Willebrand disease. Diagnosis is confirmed by the demonstration of decreased levels of factor VIII coagulant activity (VIII:C), ristocetin cofactor activity (vWF:RCo), and von Willebrand factor (vWF) antigen (vWF:Ag). vWF multimer analysis usually reveals a type II defect with decreased abundance of higher molecular weight vWF multimers. Various pathogenetic mechanisms have been described, including the development of anti-vWF antibodies and adsorption of vWF by tumor cells. Successful management approaches have included treatment of the underlying disorder, infusion of high-dose gamma globulin, replacement therapy with factor VIII/vWF concentrates, intravenous infusion of desmopressin, and administration of corticosteroids.

Acquired von Willebrand's disease: a concise review

Acquired von Willebrand's disease (AvWD), an adult-onset bleeding diathesis, has most commonly been found in patients with an underlying lymphoproliferative disease or monoclonal gammopathy. Other malignancies, autoimmune diseases, hypothyroidism, and drugs have also been associated with AvWD. We have included an illustrative case history of a patient with a bleeding diathesis consistent with AvWD and a monoclonal gammopathy who required emergent cardiac surgery. Our review of the literature determined that most cases of AvWD are due to a circulating antibody that combines with the high molecular weight multimers (HMWM) of von Willebrand factor (vWF). These vWF multimer-antibody complexes are subsequently cleared from the circulation either by the reticuloendothelial system or by adsorption onto tumor cells. Clearance of the HMWM of vWF thus results in extremely low functional levels and variable antigenic levels. Mixing studies which are traditionally used to diagnose factor inhibitors are useful only if removal of vWF-antibody complexes can be accomplished in vitro. Treatment with intravenous immunoglobulin has recently been shown to be the most effective therapy for patients with an underlying lymphoproliferative disorder or monoclonal gammopathy. This therapeutic strategy is based on the observed immune complex clearance phenomenon that appears to be operative in most cases. Other AvWD-associated diseases require treatment specifically directed at the underlying disorder.