Clinical application of the chromogenic assay of factor VIII in haemophilia A, and different variants of von Willebrand's disease

Cofactors V and VIII after endotoxin administration to human volunteers

Coagulation factor V (FV) and factor VIII (FVIII) are usually decreased in septicemic DIC. Low doses of endotoxin administered to healthy volunteers stimulate activation of the fibrinolytic, contact and coagulation systems, but not clinical DIC. Following the administration of endotoxin (4 ng/kg) to normal volunteers (n = 15), we applied new assays for FV antigens using monoclonal antibodies to the activation peptide (C1) and to the light chain of FV. At 5 hours, FV coagulant activity was significantly decreased (64 +/- 9%), as was the FV light chain antigen (74 +/- 6%), without a change in factor V C1 antigen or total protein C. In contrast, FVIII coagulant activity was greater than preinfusion levels at 2-5 hours. The decrease in FV activity may be due to APC cleavage of FV heavy chain, but the loss of light chain antigen suggests that plasmin and/or calpain also contribute. APC may not be the only enzyme responsible for cofactor inactivation. FV is one of the most sensitive markers, even reflecting subclinical activation of coagulation.

Effect of acute desmopressin and of long-term thyroxine replacement on haemostasis in hypothyroidism

OBJECTIVE

Hypothyroidism can be complicated by bleeding symptoms such as easy bruising, menorrhagia and sometimes even a severe bleeding tendency with fatal outcome. Usually there is a prolonged bleeding time, or a low plasma concentration of coagulation factor VIII (FVIII) or von Willebrand factor (vWF). The aim of the present study was to investigate the acute haemostatic effect of desmopressin in hypothyroid patients. Another aim was to study the long-term effect of thyroxine replacement on the plasma concentrations of coagulation factors and to ascertain the duration of thyroxine treatment needed to restore haemostatic function.

DESIGN AND PATIENTS

The effects of desmopressin, given intravenously over 10 minutes at a dosage of 0.3 micrograms/kg, and thyroxine treatment on haemostatic function were studied prospectively in 10 patients with hypothyroidism.

RESULTS

Before treatment only five of the patients manifested bleeding symptoms; one had prolonged bleeding time, and one had low plasma concentrations of vWF:Ag. Desmopressin virtually immediately reduced bleeding time, enhanced platelet adhesiveness, and significantly increased plasma concentrations of FVIII and vWF. The plasma concentrations of FVIII and vWF showed a significant increase after 4 months, whereas 7 months treatment with thyroxine was needed to reduce bleeding time significantly.

CONCLUSION

Our results suggest that in hypothyroid patients desmopressin may be of value for the acute treatment of bleeding or as cover for surgery.

Pharmacokinetics and hemostatic effect of different factor VIII/von Willebrand factor concentrates in von Willebrand's disease type III

Four different plasma-derived concentrates composed of coagulation factor VIII (FVIII) and von Willebrand factor (vWF) of varying quality (Hemate-P, Behring; Profilate, Alpha; and F VIII-VHP-vWF, C.R.T.S Lille), or almost purified vWF (Facteur Willebrand, C.R.T.S Lille) and one recombinant F VIII concentrate (Recombinate, Baxter) were given, in doses of 30-60 IU VIII: C/kg or 70-110 IU RCof/kg, to five patients with von Willebrand's disease type III, in order to evaluate the role of the vWF in factor F VIII concentrates. All plasma concentrates except Profilate had a multimeric vWF pattern almost similar to that of normal plasma. Bleeding time (b.t.), VIII: C, vWF:Ag, ristocetin cofactor activity, and multimeric pattern of the plasma-vWF were followed for 72 h. Both Duke b.t. and the multimeric pattern in plasma normalized after infusion of Hemate-P, F VIII-VHP-vWF, and Facteur Willebrand and, to a lesser extent, after Profilate. As expected, in response to Recombinate there was no effect on primary hemostasis, and the half-life of F VIII procoagulant activity (VIII: C) was very short. Normalization of the vWF is important not only for improving the primary hemostasis, but also for maintaining the plasma F VIII concentration on a high level, both by reducing the elimination rate of infused F VIII and via a secondary release of endogenous F VIII. If a prompt hemostatic effect is required, we recommend a concentrate containing both F VIII and all vWF multimers, but for prophylactic treatment, pure vWF may be used.

Twenty-five years' experience of prophylactic treatment in severe haemophilia A and B

In Sweden, prophylactic treatment of boys with severe haemophilia has been practised since 1958 in an attempt to convert the disease from a severe to a milder form. The present study population consisted of 60 severe haemophiliacs (52 A, 8 B), aged 3-32 years. Treatment is started when the boys are 1-2 years of age, the regimens used being 24-40 IU F VIII kg-1 three times weekly in haemophilia-A cases (i.e. greater than 2000 IU kg-1 annually) and 25-40 IU F IX kg-1 twice weekly in haemophilia-B cases. The orthopaedic and radiological joint scores (maximum scores of 90 and 78, respectively) are evaluated as recommended by the World Federation of Haemophilia. Of those subjects aged 3-17 years, 29 out of 35 individuals had joint scores of zero. The oldest group had only minor joint defects. The VIII:C and IX:C concentrations had usually not fallen below 1% of normal. All 60 patients are able to lead normal lives. In conclusion, it appears to be possible to prevent haemophilic arthropathy by giving effective continuous prophylaxis from an early age, and preventing the VIII:C or IX:C concentration from falling below 1% of normal.

DDAVP-induced enhancement of platelet retention: its dependence on platelet-von Willebrand factor and the platelet receptor GP IIb/IIIa

Although DDAVP has been shown to be haemostatically efficacious in patients with various congenital or acquired platelet disorders, no reasonable explanation has been found for this effect. We have previously shown DDAVP to increase platelet adhesiveness as measured with a platelet retention test. The aim of the present study was to investigate the mechanism of action responsible for the increased platelet retention in response to DDAVP. Patients with vWD type III and type Ia, severe haemophilia and severe thrombasthenia, as well as healthy controls, were included in the study. The effect of different concentrations of vWF in plasma and platelets was explored, as was the effect on platelet function of apyrase and monoclonal antibodies against GP IIb/IIIa and GP Ib. We found the effect of DDAVP on platelet retention to be unaffected by changes in the plasma concentration of vWF. The enhanced platelet retention after DDAVP is apparently dependent on the presence of platelet-vWF and on a normal function of the GP IIb/IIIa. The effect is not mediated via ADP or thrombin. The platelet-stimulating effect of DDAVP may be one explanation for the positive haemostatic effect in patients with certain platelet disorders.

Blood loss and safety with desmopressin or placebo during aorto-iliac graft surgery

In a double blind, placebo controlled study in 50 patients undergoing aorto-iliac graft surgery, we studied the effects of desmopressin given prior to surgery on blood loss and blood transfusion requirements. Desmopressin reduced the number of patients with clinically significant bleeding. Blood loss volumes and transfusion requirements were lower in the desmopressin group, but this could not be verified statistically. Even if our study population has a high incidence of generalised arteriosclerotic disease, there were no clinical manifestations of venous thromboembolism, no increase of graft occlusions and no myocardial infarction during the operative or early postoperative period. Desmopressin may be used in patients with excessive peroperative bleeding or a prolonged preoperative bleeding time. In patients where desmopressin is considered to be haemostatically efficacious, it may be used with a maintained margin of safety.

Epinephrine and dDAVP administration in patients with congenital nephrogenic diabetes insipidus. Evidence for a pre-cyclic AMP V2 receptor defective mechanism

We recently showed that the administration of the antidiuretic V2 specific agonist, 1-desamino[8-D-arginine]vasopressin (dDAVP), to seven male patients with congenital nephrogenic diabetes insipidus (CNDI) did not cause a decrease in blood pressure nor an increase in plasma renin activity or factor VIIIc or von Willebrand factor release. In normal subjects, plasma renin activity, coagulation factors and plasma cyclic AMP are stimulated not only by dDAVP but also by the administration of epinephrine. In the present study, we measured tissue plasminogen activator (activity and antigenicity), von Willebrand factor multimers, plasma and urinary cyclic AMP concentrations following dDAVP or epinephrine administration. We infused epinephrine into three male patients with CNDI. Factor VIIIc and tissue plasminogen activator augmented by 75 to 100% and von Willebrand Factor multimers were increased; plasma renin activity and plasma cyclic AMP concentration increased by 200%. None of these values changed when the same subjects as well as eleven other male patients with CNDI received dDAVP. Furthermore, dDAVP administration increased plasma cyclic AMP concentrations in normal subjects, but not in 14 male patients with CNDI. These results demonstrate the specificity of the extrarenal V2 receptor defect expressed in our patients. The lack of a plasma cyclic AMP response to the administration of dDAVP would suggest an altered pre-cyclic AMP stimulation mechanism.

Effect of viscosity on the pharmacokinetics and biological response to intranasal desmopressin

The effect of viscosity on the nasal absorption and biological response to desmopressin was studied in humans. Nasal solutions of desmopressin with and without the addition of 0.25% (w/v) methylcellulose were administered by a precompression nasal spray pump to 10 volunteers. Plasma levels of desmopressin were assayed by radioimmunoassay and the biological response was measured by determination of the antihemophilia factors (Factor VIII and von Willebrand factor). The results showed that the addition of methylcellulose produced a more sustained and slower absorption, with a longer time to maximum plasma concentration (tmax). However, the areas under the plasma concentration-time curve were not different, indicating a similar total bioavailability. The biological response showed a similar effect. Peak Factor VIII activity was not different, but the presence of methylcellulose produced a slower onset of activity. These findings indicate that although the addition of a viscous agent to nasal formulations may produce a more sustained effect, it delays the onset of activity and no enhancement is achieved in the total bioavailability.