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Desmopressin (DDAVP) is a proven therapy for bleeding disorders; however, the therapeutic efficacy of different parenteral formulations has never been systematically analyzed. This study investigated whether subcutaneous (SC) DDAVP provides equivalent hemostatic efficacy to intravenous (IV) desmopressin, particularly in patients with mild to moderate bleeding tendencies from hemophilia A (HA) or von Willebrand disease (vWD).We searched PubMed, EMBASE, MEDLINE, Cochrane, and CINAHL databases for observational studies and randomized controlled trials which compared the hemostatic efficacy of parenteral formulations of DDAVP in healthy patients and those with bleeding disorders. Two reviewers independently performed screening and data extraction. Extracted data included Factor VIII (FVIII) levels, von Willebrand factor (vWF) antigen levels, and vWF activity.The search strategy yielded a total of 5519 studies. Twelve studies met the inclusion criteria and were included in the review. Seven out of eight studies conducted in patients with bleeding disorders and all four studies conducted in healthy subjects found no difference in hemostatic efficacy between parenteral formulations. A meta-analysis was not performed due to disparities between study design and outcomes of interest.Our study showed that IV and SC administration of DDAVP appeared to result in near equivalent hemostatic efficacy; however, the strength of these findings is limited by the small number and lack of comparability in the primary studies. A sizable contemporary study powered to detect differences in coagulation factor levels would be required to confirm our findings.

The deficiency or abnormal activity of von Willebrand factor, a multi-adhesive protein which binds platelets to exposed subendothelium and carries factor VIII in circulation, is responsible for von Willebrand disease, the most frequent inherited bleeding disorder. Clinical symptoms are characterized by mucous membrane and soft tissue bleeding, bleeding after surgery and rarely joint and gastrointestinal bleeding. Intriguingly, also factor VIII, the protein deficient in hemophilia A, may be variably reduced because VWF stabilizes it into circulation. Treatment strategies are well designed for patients with levels of VWF activity

Introduction The effective diagnosis and monitoring of Von Willebrand Disease (VWD) requires an accurate assessment of ristocetin co-factor activity (VWF:RCo). Current methodologies include automated platelet aggregometry and manual visual agglutination both of which are laborious to perform and notoriously subject to a high degree of inter and intra assay variation. Methods and Materials We have evaluated an automated VWF:RCo assay (BC Von Willebrand Reagent, Siemens, Marberg, Germany) for use on the Sysmex CS2100i analyser (Milton Keynes, UK) and retrospectively compared the results with an in-house manual visual agglutination assay and VWF antigen (Siemens) in normal subjects and in 53 patients with various types of VWD and 23 patients following VWF therapeutic treatment. Results The intra and interassay CV was improved with the automated assay (2.3% and 3.8% respectively) compared to 7% with the manual VWF:RCo assay. Good correlation was found between the two assays (r = 0.91) in 53 patients with VWD. The mean manual VWF:RCo was 0.25 IU/ml and mean automated VWF:RCo was 0.27 IU/ml. A comparable increase in VWF:RCo following treatment, mostly with Desmopressin, was found in 13 patients with type 1 VWD (mean 3.9 fold increase with manual VWF:RCo and 3.1 fold with the automated VWF:RCo). In 13 patients with type 2 or 3 VWD following treatment mostly with concentrate , a higher increase was found with the automated VWF:RCo assay than the manual assay (mean 11.9 fold manually and mean 20.3 automated). Conclusion The automated VWF:RCo assay shows enhanced precision and analysis time in this difficult and time consuming laboratory test and its introduction should greatly improve the reliability of VWF testing.

We performed a retrospective audit of desmopressin (DDAVP) usage to assist in the functional characterisation of von Willebrand disease (VWD). Data was evaluated for 208 patients, comprising those with VWD (Type 1 [n = 160], Type 2A [n = 19], Type 2M [n = 10]), plus 19 individuals with haemophilia or carriers of haemophilia. Laboratory testing comprised pre- and post-DDAVP evaluation of factor VIII (FVIII:C), von Willebrand factor (VWF) antigen (VWF:Ag), VWF ristocetin cofactor (VWF:RCo) activity, VWF collagen binding (VWF:CB) activity, and in one laboratory an alternate VWF activity assay. In brief, combined usage of VWF:RCo and VWF:CB appears to provide improved functional characterisation and/or ‘classification’ of VWD types, in particular better differentiation of Type 2A and 2M VWD, and clearer validation of a Type 1 VWD diagnosis. Thus, (i) Type 1 VWD displayed generally good absolute and relative rises in all test parameters, although relative rises were greatest for FVIII:C and VWF:CB, and CB/Ag ratio increases overshadowed those for RCo/Ag; (ii) Type 2A VWD patients showed good absolute and relative rises in both FVIII:C and VWF:Ag, but poor absolute rises in both VWF:CB and VWF:RCo; although small rises in both CB/Ag and RCo/Ag were also observed, both ratios tended to remain below 0.7; (iii) finally, Type 2 M VWD patients generally showed good absolute and relative rises in FVIII:C, VWF:Ag and VWF:CB, but a poor absolute and relative rise in VWF:RCo; thus, there were good rises in CB/Ag ratios but little change in RCo/Ag, which tended to remain below 0.7. Future multi-centre prospective investigations are warranted to validate these findings and to investigate their therapeutic implications.

Recent studies have suggested a unifying pathophysiological concept to explain the underlying defects of von Willebrand factor (VWF) causing von Willebrand disease (VWD) and have highlighted the relevance of simple VWF related activities in producing a useful diagnosis. A standardized bleeding history condensed into a final bleeding score and few widely available laboratory tests, such as VWF ristocetin cofactor activity, VWF antigen and factor VIII (FVIII), in the index case and in his/her relatives are of critical importance. Ristocetin-induced platelet aggregation (RIPA) should also be tested. Trial with desmopressin should be carried out in patients, except those with virtual absence of VWF or with increased RIPA. Desmopressin should be used in all responsive patients as first choice. Substitutive treatment with VWF/FVIII containing products should be used in unresponsive patients, in those with heightened response to desmopressin or in those undergoing interventions requiring good hemostasis for more than 3-5 days. Special consideration should be deserved to the treatment of menorrhagia and parturition.

Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder that is characterized by structural or functional alterations in von Willebrand factor (VWF) caused by a range of lymphoproliferative, myeloproliferative, cardiovascular, autoimmune, and other disorders. The pathogenic mechanisms responsible for the VWF abnormalities depend on the underlying condition, but include clearance due to binding of paraproteins, inhibition of VWF, adsorption to the surface of platelets, increased fluid shear stress, and resultant proteolysis or, more rarely, decreased synthesis. The diagnosis and treatment of AVWS are complicated by the need for multiple laboratory tests and the management of bleeding risk in a typically elderly population with serious underlying conditions that predispose towards thrombosis. Recently developed diagnostic algorithms, based on standard laboratory assays, may assist clinicians with the diagnostic workup and help differentiate between AVWS and von Willebrand disease (VWD) types 1 and 2. AVWS should be considered in all patients with new-onset bleeding whenever laboratory findings suggest VWD, particularly in the presence of an AVWS-associated disorder. AVWS testing is also recommended prior to surgery or an intervention with a high risk of bleeding in any individual with an AVWS-associated disorder. Treatment of the underlying condition using immunosuppressants, surgery, or chemotherapy, can lead to remission of AVWS in some individuals and should always be considered. Strategies to prevent and/or treat bleeding episodes should also be in place, including the use of VWF-containing factor VIII concentrates, desmopressin and tranexamic acid. Treatment success will depend largely on the underlying pathogenesis of the disorder.

Desmopressin (DDAVP), an analog of vasopressin (AVP), has wide clinical application as an anti-hemorrhagic (AH) agent. DDAVP in vivo releases vWF from endothelial cells but is reported to have little action on platelets. However, DDAVP is often used to improve hemostasis in platelet dysfunctions. We examined the effect of DDAVP on platelet microparticle (PMP) formation and procoagulant activity in vitro using platelets from normal volunteers and in vivo in six patients receiving DDAVP therapy. In the former, platelets were incubated with DDAVP (0.5 to 25 nM) and PMP released were stained with FITC-labeled MAb alpha-GP IIb/IIIa for flow cytometry. Procoagulant activity was measured in a clot-based assay using Russel's viper venom (RVV) calibrated with cephalin. A mean increase of 2-3 fold was observed in both PMP and procoagulant activity. Parallel to these observations was a dose-dependent rise in organelle-associated Ca2+. The assays were also performed on six patients prior to and at one hour after infusion of DDAVP, and similar but lesser effects were observed. We conclude that DDAVP acts on platelets in vitro, and that these effects may contribute to the hemostatic action of DDAVP in platelet dysfunctions in vivo.

von Willebrand disease (VWD) is the most common inherited bleeding disorder and arises from deficiencies and/or defects in the plasma protein von Willebrand factor (VWF). VWD is classified into 6 different types, with type 1 identified as a (partial) quantitative deficiency of VWF, type 3 defined by a (virtual) total deficiency of VWF, and type 2 identifying four separate types (2A, 2B, 2M, 2N) characterised by qualitative defects. The classification is based on phenotypic assays including FVIII, VWF:Ag and VWF activity, typically by ristocetin cofactor (VWF:RCo), but also increasingly by collagen binding (VWF:CB). Phenotypic testing may be supplemented by multimer analysis, RIPA, and VWF:FVIII binding. Although genetic analysis is not required to diagnose VWD or to define a classification type, it may be useful in discrete situations. The current review briefly covers this diagnostic process, with a focus on newer approaches, including extended test panels and the use of data from desmopressin challenges as a diagnostic tool.

Administration of 1-desamino-8-D-arginine vasopressin (DDAVP), a synthetic vasopressin derivative, causes an increase in plasma factor VIII and von Willebrand factor (vWF). Recently, evidence has become available that intravenous infusion of DDAVP shortens the prolonged bleeding times in some patients with primary platelet defects even though their plasma levels of vWF and FVIII are normal prior to drug administration. The mechanism of this effect of DDAVP has not been well defined and it has been generally considered that the beneficial effect on the bleeding time is related to the rise in plasma vWF and its impact on platelet adhesion to subendothelial components including collagen, an important step in hemostasis. Thus, studies aimed at understanding the effect of DDAVP have focused on vWF-mediated adhesion of platelets to the subendothelium. For example, Sakariassen et al studied the platelet adherence to human arterial subendothelium and concluded that DDAVP improves hemostasis by causing enhanced vWF-mediated platelet adherence. This mechanism would explain the shortening of the bleeding time in patients with milder forms of vWD with subnormal levels of vWF. But patients with congenital platelets defects have normal plasma vWF raising the possibility that there may be other mechanisms contributing to the beneficial effect of DDAVP. It is clear that platelets can interact directly with collagen, mediated by specific platelet binding sites. Further, DDAVP binds to platelets even though by itself does not activate them. The present investigation was designed to elucidate whether DDAVP had any effect on the direct adhesion of platelets to collagen in the absence of mediation by vWF. Hashemi et al have suggested that the effect of DDAVP on endothelial cell release of vWF is mediated by an as yet uncharacterized intermediate factor(s) released from peripheral mononuclear cells. Therefore, we studied the effect also of plasma samples obtained from patients treated with DDAVP on adhesion of platelets to collagen.

Although the vasopressin analogue desamino-d-arginine vasopressin (DDAVP) induces a very well characterized increase in factor VIII (FVIII), von Willebrand factor (vWF), tissue plasminogen activator (t-PA) and urokinase-type plasminogen activator (u-PA), the mechanism(s) by which DDAVP enhances the plasma levels of these proteins is poorly understood. Some clinical evidence suggests that certain patients repeatedly treated with DDAVP at closely spaced intervals become progressively unresponsive (tachyphylaxis). In order to investigate the effect of repeated DDAVP infusion on the behaviour of FVIII, vWF, t-PA and u-PA, we infused three different doses of DDAVP (0.3 microgram/Kg) to six healthy volunteers (19-26 years old, mean 22) at 12-hour intervals. Blood samples were collected immediately before and after DDAVP. The second and third infusion of DDAVP induced a low response of FVIII and vWF. In contrast, t-PA and u-PA exhibited a consistent response after each DDAVP infusion. If the progressive decrease of FVIII and vFW response observed in healthy subjects after repeated doses of DDAVP at 12-hour intervals is extended to haemophiliacs and von Willebrand's patients, the usefulness of desmopressin may be limited when these proteins must be raised therapeutically for a prolonged period of time. Finally, our results suggest that the mechanism for regulating the release of vWF and plasminogen activators in the conditions of our study are not dependent.

A 21-year-old woman (A.S.) and his 16-year-old brother (A.L.) with congenital afibrinogenemia were investigated. They suffered in the past from several episodes of joint hemarthroses and posttraumatic bleeding. A.S. suffered from two spontaneous hemoperitoneum and two laparotomies with wedge ovary resection _____--------__________~-~_____-_-~-~-__--~-~-~~~~----~~~~~~~~~~~

The effects of desmopressin and dextran on haemostasis and fibrinolysis were studied in four healthy volunteers. Both drugs were compared to placebo, each volunteer being subject to four experiments. Dextran 70 (30 g i.v.) moderately decreased VIII:C and vWF:Ag and slightly increased antithrombin III, also when haemodilution and diurnal variation were considered. Desmopressin (0.3 γ/kg BW i.v.), alone as well as in combination with dextran, increased VIII:C, vWF:Ag, protein C and tPA and decreased PAI-1. The combination of desmopressin and dextran stimulated coagulation and fibrinolysis and might be of relevance to surgical blood loss as well as to postoperative thromboembolism.

Endothelial cells in biopsied blood vessels from von Willebrand factor (vWf)-deficient Doberman pinscher dogs contain immunologically detectable vWf. These dogs and normal dogs were treated with DDAVP (0.6 microgram/kg) and epinephrine (0.5 microgram/kg/min for 30 minutes) and were exercised, using 5 different exercise protocols, (3-4 m/s for 5-40 minutes at 0-5% grade) to determine if treatments reported to increase plasma factor VIII:C/vWf complex in humans would elevate canine plasma vWf. Following the two most strenuous exercise conditions--30 and 40 minutes--plasma von Willebrand factor antigen (vWf:Ag) increased in normal dogs by 30% and 70%, respectively. Factor VIII:C was increased 47% by the most strenuous exercise conditions. The vWf-deficient dogs would not exercise beyond 30 minutes and neither vWf:Ag nor factor VIII:C activity increased. Following DDAVP, plasma vWf:Ag increased in the normal dogs by 47% and factor VIII:C activity was increased by 48%. Factor VIII:C activity increased by 30% in the vWf-deficient dogs, but there was only a slight change in vWf:Ag. Bleeding time decreased in 5 of 6 vWf-deficient dogs. In the normal dogs vWf:Ag increased by 14% after epinephrine infusion, but factor VIII:C activity did not change; neither parameter was altered in the vWf-deficient dogs. While the factor VIII:C/vWf:Ag complex was increased in the normal dog by exercise and DDAVP, the increase is not as pronounced as has been reported for humans. It is not known whether the poor response of the vWf-deficient dog is due to low levels of vWf in their endothelium or to a release defect.

Fil: Sánchez Luceros, Analía Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina Fil: Meschengieser, Susana S.. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina Fil: Turdó, Karina. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina Fil: Arizó, Adriana. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina Fil: Woods, Adriana Inés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Casais, Patricia. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina Fil: Blanco, Alicia Noemi. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina Fil: Kempfer, Ana Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Lazzari, María Ángela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Academia Nacional de Medicina de Buenos Aires. Instituto de Investigaciones Hematológicas "Mariano R. Castex"; Argentina

Desmopressin, or DDAVP, the vasopressin analogue, can be used to reduce blood loss in patients with congenital and acquired hemostatic disorders (1) and also when such disorders have been induced by drugs used in relation with surgery (2). It is a potent antidiuretic drug, although there seems to be a physiological compensation of this effect in patients undergoing surgery (3). The polysaccharide dextran, which is used for plasma expansion and thromboprophylaxis, has an additive effect with desmopressin on the blood volume in healthy volunteers (3). Desmopressin does not impair the effect of dextran to prevent postoperative thromboembolism (4). In order to further elucidate possible desmopressin-dextran interactions we have studied how desmopressin affects the pharmacokinetics of dextran.

DDAVP, an analog of vasopressin, has been shown to have hemostatic activity. Although it has been used clinically to control bleeding, there have been very few attempts to characterize this agent in experimental animals. We describe a new animal model which is fast, reliable and inexpensive, and which may be used to screen novel analogs of the peptide. Under sodium pentobarbital anesthesia, rats were bilaterally nephrectomized and implanted with indwelling intravenous cannulae. The next day they were re-anesthetized, a standardized cut was made in the tail and the tail was allowed to bleed into warm isotonic saline (25ml). After 10 min., the tail was removed from the saline and the blood loss was measured either by laser nephelometry or by colorimetric analysis. DDAVP was then injected intravenously and the rat was allowed to rest quietly for 30 min., after which time a second incision was made in the tail and blood loss again measured for 10 min. Unlike bleeding time which was highly variable, blood loss proved to be a reliable index of the hemostatic activity. Thus we were able to demonstrate that DDAVP reduced blood loss in the uremic rats, whereas it was without effect in intact rats.

1-Deamino-8 D-arginine vasopressin (DDAVP) has been used effectively to normalize the bleeding time in various hemostatic disorders. In von Willebrand disease the reduction in bleeding time is due to the preferential release of large multimers of von Willebrand factor from endothelial cells. However, since the bleeding time correction in patients with uremia and liver disease is independent of the release of von Willebrand antigen and activity, other mechanisms of action of DDAVP need to be considered. Endothelial cells generate several thromborepellant factors including 13-hydroxyoctadecadienoic acid (13-HODE), an inhibitor of platelet adhesion to subendothelium. Using cultured fetal bovine aortic endothelial cells (FBAECs), we have investigated whether DDAVP modulates the production of 13-HODE. We have demonstrated that 14C-linoleic acid labeled FBAECs release several oxygenated derivatives of linoleic acid following a 120 min incubation in the presence of serum. One of these products was identified by chromatographic procedures as 13-HODE. The production of 13-HODE was decreased significantly by DDAVP (1-100 ng/ml) with maximal reduction (approx. 25%) seen at 1 ng/ml of DDAVP. While vehicle treated control FBAECs generated 6780 +/- 690 cpm of 13-HODE per 10(6) cells (mean +/- SE, n = 8), DDAVP treated FBAECs produced 4950 +/- 310 (P0.01), 5390 +/- 390 (P0.01), and 5720 +/- 410 cpm (P0.05) of 13-HODE at 1, 10, and 100 ng/ml DDAVP respectively. Our findings of a decrease in 13-HODE would explain the previously observed morphologic changes of increased platelet adhesion to subendothelium following DDAVP infusion and contributes to our understanding of the mode of action of this therapeutic agent in hemostatic disorders.

Nine healthy volunteers and 23 patients with various types of von Willebrand disease were studied before and after DDAVP infusion. We investigated the behaviour of factor VIII/von Willebrand factor measurements, and of tissue plasminogen activator and urokinase-type plasminogen activator. In mild von Willebrand disease the increase of both plasminogen activators was similar to that seen in normal controls. A different fibrinolytic behaviour was found in the type I platelet low and in the type III von Willebrand disease patients. An impaired and absent fibrinolytic response to DDAVP was seen in the former and in the latter von Willebrand disease, respectively. A close relation between either u-PA and t-PA or von Willebrand factor was observed. The possibility of a linkage among these three proteins was discussed.

Aggregation of human platelets by vasopressin is potently inhibited by 1-[beta mercapto-(beta, beta'-cyclopentamethylene propionic acid)]-L-arginine vasopressin, a selective vasopressor (V1) antagonist. 1-Desamino-8-D-arginine-vasopressin, a selective anti-diuretic (V2) agonist failed to induce aggregation and acted as a weak antagonist. Vasopressin analogues which lacked the N-terminal amino group or which contained an uncharged amino acid residue at position 8 acted as partial agonists for the human platelet. The response to such partial agonists could be enhanced by increasing the cytosolic Ca2+ concentration but not by altering the level of cyclic-3', 5'-AMP. These observations provide further evidence indicating that the platelet vasopressin receptor is of the V1 sub-type.

A highly concentrated new vasopressin, 1-deamino-8-D-arginine vasopressin, DDAVP was dripped intranasally to normal subjects, mild hemophilia A and von Willebrand's disease patients. Intranasal administration of DDAVP shortened act PTT and increased VIII:C, VIIIR:AG and VIIIR:WF. Tooth extraction, hematuria and joint pain in those patients were controlled well by this method without administration of factor VIII. An intranasal drip of DDAVP seems to be an applicable way to control hemorrhagic tendencies of hemophilia patients.

In 37 patients with prolonged bleeding time, where thrombocytopenia, von Willebrand's disease or deficiency of other coagulation factors could be excluded, we have evaluated the effect of a DDAVP-infusion (0.2 ug/kg) together with tranexamic acid (10 mg/kg). Patients with acquired impairment of primary hemostasis were not included, except two cases where this could have been a contributing factor: The bleeding time was completely normalized in 27 cases and partially corrected in three more patients . The predominant feature among those, who did not respond, was a pattern compatible with thrombasthenia or cyclooxygenase deficiency, as assessed by platelet aggregation studies. Among the patients, in whom DDAVP was effective, this drug was thereafter successfully used as an alternative to blood products in 8 cases during and after surgery or delivery.

The mechanism of aggregation induced by arginine vasopressin (AVP) was studied in human platelet rich plasma. AVP--over the range of 1.8-113.6 mU/ml--caused a dose-dependent aggregation with a concomitant stimulation of thromboxane B2 (TXB2) formation. d(CH2)5Tyr (Me)AVP did not by itself affect platelet aggregation or TXB2 release, but completely inhibited the action of AVP. DDAVP up to the concentration of 280 pM/ml had no effect on aggregation. Pretreatment of platelets with verapamil, trifluoroperazine or methylimidazole, a thromboxane synthetase blocker, prevented AVP-induced aggregation and TXB2 release. Neither phenidone in lower concentration nor nordihydroguaiaretic acid inhibited the ability of AVP to induce aggregation and TXB2 release. These results are consistent with the hypothesis that human platelets possess AVP receptor of the calcium-dependent vasopressor (V1) subtype and suggest that AVP-induced platelet aggregation is mediated via thromboxane release.

The effect of D.D.A.V.P. (desamino-cys'-D-arg8-Vaso-pressin) on the survival characteristics of transfused VIII concentrate was studied in six severe, adolescent, haemophiliacs (VIII:C 1 iu/dl). D.D.A.V.P. was administered at a concentration of 0.3 ug/kg immediately following or 24 hours post infusion. No significant alteration in the half disappearance (1/2 d) or biological half-life (t 1/2) was detected for either VIII procoagulant (VIII:C) or its antigenic counterpart VIII:C Ag. As anticipated there was a significant (if sub-optimal) increase in VIII:R Ag within 2-4 hours of D.D.A.V.P. administration.

In a pilot study on 9 patients with acute deep venous thrombosis of the leg the fibrinolytic response and the possible thrombolytic effect of desmopressin (DDAVP), when given supplementary to standard heparin treatment, was examined. Six injections of 0.3-0.4 microgram DDAVP/kg b.w. at 12 hours intervals were given. No serious side effects were observed. The fibrinolytic variables that followed showed that plasma levels of t-PA increased significantly and most pronounced after the first injection. Rephlebography 4-7 days after hospitalization showed partial thrombolysis in 7 out of 9 patients. The phlebographic score according to Marder was reduced from 22.7 +/- 12.1 to 18.4 +/- 10.1 (p = 0.018), corresponding to a thrombus size reduction of 19%. No correlation between the level of the fibrinolytic variables measured and the degree of thrombolysis in the individual patients, could be demonstrated in this small number of patients.

8 healthy volunteers, 15 patients with mild haemophilia A and 14 patients with von Willebrand's disease received an infusion of DDAVP (0,4 μg/kg bodyweight). Shortly after infusion, in all normals and in all haemophiliacs a marked increase of fibrinolytic activity was observed. In 6 out of 14 patients with von Willebrand's disease, however, activation of fibrinolysis was absent or only slight. In these patients, venous occlusion did also not induce activation of fibrinolysis. Fibrinolytic response was normal in the remaining 8 patients with von Willebrand's disease. A combined endothelial cell deficiency is discussed for a sub-group of von Willebrand patients, resulting in impaired production/release of F VIII and impaired production/release of vascular plasminogen activator.

A radioimmunoassay (RIA) has been set up using purified human melanoma tissue plasminogen activator and a specific antiserum raised against it. Concentration of antigen in citrated plasma of resting human subjects was found to be 7.1 ± 1.6 ng/ml (mean ± S.D.) while the lower limit of sensitivity of the RIA was 2 ng/ml. After venous occlusion or DDAVP infusion the levels of antigen were invariably elevated and a significant increase in the proportion of antigen having fibrin binding properties was observed. Decay studies in vitro and gel filtration of post-stimulus plasma indicated that the RIA detects active and inactive forms of antigen and the possible nature of the inactive antigen is discussed.

A set of fibrinolytic parameters was measured in 40 healthy subjects before and after a venous occlusion (VO) test lasting 10 min. After VO, plasma levels of tissue-type plasminogen activator (t-PA) antigen increased in all subjects, t-PA activity increased only in 25 subjects who were considered responders and remained unchanged in 15 (non-responders). High levels of plasminogen activator inhibitor (PAI) in the non-responder group explain this discrepancy. The non-responders had basal levels of PAI activity and t-PA antigen higher than responders (p less than 0.0001) and their basal levels of t-PA activity were lower (p less than 0.001). DDAVP infusion elicited good responses in 7 of 9 non-responders to VO with a fall of PAI activity to 0. Our data indicate that a high proportion of healthy subjects do not have a fibrinolytic response after VO, that a lack of fibrinolytic response to VO is due to high plasma levels of PAI and that DDAVP infusion appear to be more selective than VO for detecting non-responders.

Evaluation of the extent of response on factor XII and factor XI, and factor VIII coagulant activity, von Willebrand factor antigen and ristocetin cofactor after desamino-8-D-arginine vasopressin stimulation. Coagulation studies were performed on normals, thrombophilic patients and on a group of subjects affected by congenital factor XII and factor XI deficiencies

The intravenous infusion of desmopressin acetate (DDAVP), a synthetic vasopressin analogue, has been shown to cause a sustained increase in all Factor VIII related properties (VIII-C, VIIIR-Ag, VIIIR-WF) in patients with mild to moderate hemophilia and von Willebrand's disease. This study examines the effect of high doses of intranasal DDAVP (0.4 μg/kg BiD) in four patients with hemophilia A and one patient with von Willebrand's disease. In spite of a physiologic response with a decrease in urine volume and increase in urine osmolality, there was no effect on the Factor VIII complex.

This study evaluates how plasminogen activator (PA) behaves in response to intravenous (i. v. ) and intranasal (i. n. ) DDAVP in healthy subjects. Five volunteers received in random order four i.v. DDAVP doses (0.1–0.4 μg/Kg) and saline. Changes in PA (euglobulin lysis time) were measured from baseline after 30, 120 and 360 min. PA increased significantly with dose and reached a seven-fold mean rise at 0.4 μg/Kg. Five other subjects, similarly treated with i. n. DDAVP (1–4μg/Kg), showed a significant increase (two-fold over baseline values) but no clear dose-response relationship. To evaluate the rate of PA return to baseline values, seven subjects received a single i.v. DDAVP dose (0.4 μg/Kg) and PA changes were measured at various post-infusion intervals. The pattern of PA clearance from the circulation was clearly bimodal. The mean half-disappearance time of the rapid component was 62 min, that of the slower component, 457 min. Finally, to assess the consistency of PA response following repeated treatment, five healthy subjects were given five daily i.v. doses of DDAVP (0.4 μg/Kg). Even though there was a progressive reduction in the response, a significant increase over baseline was still observed after the last dose.

A radioimmunoassay for 6-keto-prostaglandin F1alpha was developed and validated. The apparent concentration of 6-keto-prostaglandin F1alpha in human venous plasma was found to be less than 50 pg/m1. A rise in plasma 6-keto-prostaglandin F1alpha was detected on infusion of prostacyclin or of DDAVP in human subjects. Various methods of organic extraction were applied to plasma samples prior to radioimmunoassay. Organic extraction and silicic acid chromatography introduced marked and unacceptable nonspecific interference on subsequent radioimmunoassay. This interference was abolished by high pressure liquid chromatography of eluates and extracts prior to assay. Using these methods, a very low concentration of 6-ketoprostaglandin F1alpha in human venous plasma was confirmed.

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Suppression of the fibrinolytic system is a well-known phenomenon in patients with Behcet's disease regardless of whether they present thrombotic complications. This finding has been related to impaired production and/or release of plasminogen activators from the vascular endothelium. In previous studies a diminished release of PF4 upon heparin stimuli was observed in plasma from patients with Behcet's disease and interpreted as an additional indicator for endothelial cell dysfunction. In the present investigations, 12 patients and 10 healthy volunteers received DDAVP infusions and euglobulin clot lysis time, factor VIII activities and 6-keto-PGF1 alpha levels in plasma were repeatedly determined before and after infusions. At different times following DDAVP infusion, euglobulin clot lysis time was significantly longer and levels of F.VIII R:Ag were lower in patients than in normals. F. VIII:C activity increased in both groups, whereas no changes were seen in the plasma levels of 6-Keto-PGF1 alpha either in normals or in patients. It is concluded that the disseminated damage of endothelial tissue associated with Behçet's disease correlates with multiple endothelial cell dysfunctions and subsequent hemostatic abnormalities.

Evidence is presented that 1-deamino-8-d-arginine vasopressin (DDAVP), a vasopressin analog, has a direct effect on isolated vessel segments. The most significant finding is increased platelet adhesion and spreading at injury sites. An isologous human umbilical vein perfusion model was used to compare effects of DDAVP with those of epinephrine or zero drug controls. Scanning electron microscopy, in conjunction with morphometry, permitted quantification of platelet adhesion to subendothelium exposed by minimal injury in the model. In addition, umbilical vein effluents were tested for levels of factor VIII moieties (F VIII:C, F VIII:Rag, F VIII:RCof) and the prostanoids, 6 keto PGF1 alpha (stable metabolite of prostacyclin) and TXB2 (stable metabolite of thromboxane A2. Only F VIII:C from DDAVP treated segments was significantly (p less than 0.01) changed from controls.

When compared to man, the rabbit shows marked prolongation of the dilute whole blood clot lysis time and an attenuated increase in plasminogen activator (PA) after the infusion of desmopressin (DDAVP). The levels of specific components of the plasma fibrinolytic system of the rabbit were compared to those in human plasma to ascertain their role in the differences between species. PA activity and plasminogen levels were similar in the two species. Anti-plasmin and plasminogen activator inhibitor (PAI) activity were lower in the rabbit than in man. The rabbit PAI, apparently similar to that described in man, was not increased by DDAVP infusion. The disparity between man and rabbit with respect to the lysis times of dilute blood clots and response to DDAVP cannot be explained by differences in functional plasma levels of inhibitors or activators of the fibrinolytic system.