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Biomedical subjects

U Hedner

Publications and source records attributed to U Hedner.

At least 37 records · Page 2Linked to original sources
PubMed2000

Correlation between different intensities of anti-vitamin K treatment and coagulation parameters.

In order to study the effect of different intensities of anti-vitamin K treatment on coagulation parameters, 23 patients with venous thromboembolism were given, after the initial treatment period, warfarin at doses giving an International Normalised Ratio of 1.3-2.0 for 4 weeks, and of 1.1-1.3 for another 4 weeks. Blood samples were taken at the end of each of these periods and 4 weeks after the end of warfarin treatment. The vitamin K-dependent coagulation factors VII, IX, and X, as well as the inhibitor protein C and its cofactor protein S, all showed a highly significant correlation with treatment intensity. This was to some extent also true for the coagulation activation markers, prothrombin fragment 1+2 and thrombin-antithrombin complex. Ratios of pro- and anticoagulant factors in some instances showed a decrease at therapeutical (International Normalised Ratio) levels, and also sometimes with reduced warfarin treatment intensity. Taken together, our results encourage further research addressing issues of varying treatment intensity with warfarin and alternative methods for monitoring of anti-vitamin K treatment.

Adult↗
PubMed2000

Recombinant coagulation factor VIIa: from the concept to clinical application in hemophilia treatment in 2000.

The development of factor VIII and factor IX concentrates markedly improved the management of hemophilia A and B and made home therapy possible. However, treatment of hemophilic patients with acquired inhibitors remained difficult. The preparation of prothrombin complex concentrates, nonactivated or activated, addressed this difficult clinical problem, but their use was associated with serious side effects. Factor VIIa was found to be a safer treatment modality. Factor VIIa per se is inactive and needs tissue factor (TF) to become biologically active. TF serves as the receptor for factor VIIa. TF is expressed from vessel walls only upon injury. Treatment of inhibitor patients with plasma-derived factor VII was found to be successful. This led to the development of recombinant factor VIIa, which was also found to be successful in managing hemophilia patients with inhibitors. Up to this point, large numbers of patients have been treated and few serious side effects have been noted. Because of its unique effects on the hemostasis system, recombinant factor VIIa will be useful for other indications as well, including patients with congenital factor VII deficiency, patients with bleeding and liver function impairment, patients with quantitative and qualitative platelet defects, and individuals who have sustained multiple trauma. The development of recombinant factor VII is reviewed in detail.

Factor VII↗
PubMed2000

Development of tinzaparin: a heparinase-digested low-molecular-weight heparin.

Although heparin and its properties had been discovered in the early 1920s, the different characteristics associated with different molecular-weight fractions of heparin were only recognized in the late 1970s. Tinzaparin is a low-molecular-weight heparin (LMWH) produced by heparinase digestion of heparin. Preclinical research on tinzaparin established that there were no differences in the antithrombotic activity compared with heparin. Clinical studies evaluating tinzaparin vs. standard heparin for thromboprophylaxis of deep-vein thrombosis in general and orthopedic surgery found that tinzaparin was as effective as standard heparin. Tinzaparin was also evaluated vs. standard heparin in the treatment of acute proximal vein thrombosis; time-to-event curves suggested that this LMWH could be more effective than standard heparin.

Animals↗
PubMed2000

Measurement of the procoagulant activity of factor VII in patients with liver cirrhosis and normal prothrombin activity: evaluation of the bleeding risk.

Patients with liver cirrhosis and diminished prothrombin activity (PA) have decreased levels of factor (F)VII coagulation activity (FVII:C) and an increased bleeding tendency. Whether this is also true of cirrhotic patients with normal PA is unknown. This study measured FVII:C levels in such patients and investigated the correlation between altered FVII:C levels and bleeding tendency. Fifteen of 41 patients (37%) had decreased FVII:C levels. Of these, the Child-Pugh score of liver function was A (n = 9), B (n = 5) and C (n = 1), compared to A (n = 25) and B (n = 1) in patients with normal FVII:C values (chi2 = 8.88, P = 0.012). Bleeding time was significantly prolonged in 9/15 patients (60%) with impaired FVII:C activity, compared to 3/26 (12%) patients with normal FVII:C values (relative risk: 5.2, 95% CI: 1.7-16.6; P = 0.003). In conclusion, liver cirrhosis patients may show impaired FVII:C levels despite normal PA. In those with decreased FVII:C activity, prolonged bleeding time is hypothesized to arise from an alteration in platelet activation due to FVII deficiency and diminished platelet count. Bleeding risk should be evaluated, regardless of platelet count, before these patients are subjected to invasive diagnostic or surgical procedures.

Adult↗
PubMed2000

NovoSeven as a universal haemostatic agent.

Initiation of haemostasis involves the formation of a complex between tissue factor (TF) and activated factor VII (FVIIa) following injury. TF is found in the deeper layers of the vessel wall, in atherosclerotic plaques and in some types of tumour cell and is only exposed to circulating blood after tissue damage. Likewise, FVII is only enzymatically active when complexed with TF (TF/FVIIa). It has recently been shown that the administration of recombinant activated FVII (rFVIIa) in high doses (approximately 100 microg/kg) can induce haemostasis in the absence of FVIII and FIX. In addition, from in-vitro studies it appears that rFVIIa can bind with low affinity to the activated platelet surface and, independently of TF, induce the thrombin burst needed for haemostasis. The ability of rFVIIa to compensate for FVIII/FIX deficiency has been proven clinically in haemophilia patients with life- and limb-threatening bleeds. In addition, patients with congenital FVII deficiency have been successfully treated for bleeds with rFVIIa. Recombinant FVIIa has been used in patients with platelet disorders; five patients with Glanzmann's thrombasthenia and one with Bernard-Soulier's thrombasthenia have had bleeding episodes managed effectively. Recombinant FVIIa has also been shown to normalize prothrombin time in patients with liver disease and in warfarin-treated individuals.

Blood Coagulation↗
PubMed2000

NovoSeven in warfarin-treated patients.

Haemorrhages represent a major complication of treatment with vitamin K antagonists. In cases of severe bleeding, a prompt effect on the increased International Normalized Ratio value is vital to achieve haemostasis. As conventional treatment, that is plasma or plasma-derived concentrates, carries the risk of blood-borne virus transmission, new treatments are needed. An open, multicentre pilot trial is currently under way to determine the effect of recombinant activated factor VII (rFVIIa; NovoSeven) administered to patients experiencing a bleeding episode after receiving vitamin K antagonists. When rFVIIa was given to a patient with a warfarin-induced nosebleed, it had an immediate haemostatic effect and the International Normalized Ratio value virtually normalized.

Anticoagulants↗
PubMed2000

Effect of locally-applied active site-blocked activated factor VII (ASIS) on experimental arterial thrombosis.

The starting point of blood coagulation in vivo is the formation of a complex between tissue factor (TF), which is exposed following vascular disease or trauma, and activated blood coagulation factor VII (FVIIa). This blinded, random, paired study evaluates whether active site-blocked activated FVII (FVIIai, ASIS), which binds avidly to TF but is unable to initiate the coagulation processes, inhibits experimental thrombosis. Arteriotomy and deep vessel wall trauma were performed in the central arteries of rabbits' ears. The topical administration of ASIS (0.5 mg in 200 microl vehicle) resulted in a distinct antithrombotic effect compared to vehicle alone. Patency rates at 30 and 120 min after reperfusion were 85% and 75% in the ASIS group and 45% and 30% in the vehicle group, respectively (P = 0.008 and P = 0.004). In contrast, intravenous administration of ASIS (4 mg/kg) produced no antithrombotic effect. Arteriotomy bleeding times were 1.5 min in the ASIS group and 2.0 min in the vehicle group (medians, P = 1). Local application of ASIS produces a pronounced antithrombotic effect in rabbits without giving rise to antihaemostatic side-effects. This mode of treatment may have a potential for a variety of clinical interventions in injured or diseased vessels.

Animals↗
PubMed2000

Plasma lipoproteins enhance tissue factor-independent factor VII activation.

The effect of plasma lipoprotein fractions (large very-low-density lipoprotein, small very-low-density lipoprotein, intermediate-density lipoprotein, and low-density lipoprotein) on initiation of blood coagulation by supporting factor VII activation or by stimulating monocytes to express tissue factor was investigated in vitro. Endotoxin-free preparations of lipoprotein fractions did not induce functional tissue factor in monocytes, whereas all lipoprotein fractions enhanced tissue factor-independent activation of factor VII by factor Xa and by factors Xa/Va. In contrast, no or only slight enhancement of factor IXa-, factor IXa/VIIIa-, factor XIa-, or thrombin-mediated factor VII activation was observed. The effect of small very-low-density lipoprotein was less than that of large very-low-density lipoprotein, and intermediate-density and low-density lipoproteins caused an even lower but still significant increase of factor Xa- and factor Xa/Va-mediated factor VII activation. When the data were normalized for apolipoprotein B-100 content, differences remained between lipoprotein fractions. In contrast, when phospholipid content was used for normalization, differences between lipoprotein fractions in factor Xa- and factor Xa/Va-mediated factor VII activation disappeared, indicating that phospholipids were involved in factor VII activation. This was supported by enhancement of factor Xa-mediated factor VII activation by synthetic phospholipid vesicles containing negatively charged phospholipids.

Blood Coagulation↗
PubMed2000

Future possibilities in the regulation of the extrinsic pathway: rFVIIa and TFPI.

Following vessel wall injury, tissue factor (TF) is being exposed and forms complexes with the already activated FVII (FVIIa) present in the circulating blood, providing a limited amount of thrombin molecules that activate a number of coagulation proteins as well as the platelets. As a result of activation with thrombin the platelet surface exposes negatively charged phospholipids to which activated coagulation proteins bind tightly, and full thrombin generation occurs, resulting in the conversion of fibrinogen into fibrin. After the first FXa is formed, the tissue factor pathway inhibitor (TFPI) forms a complex with FXa. In the next step a quaternary complex is being formed, TF/FVIIa/FXa/TFPI, which inhibits the first step of the haemostatic pathway. Recombinant FVIIa (rFVIIa) has been developed for use as a haemostatic agent (NovoNordisk A/S, Denmark). Inactivated rFVIIa (rFVIIai) has also been prepared, and it has similar binding capacity to TF as rFVIIa but it blocks the catalytic activity of the TF complex. In various animal models rFVIIai has been demonstrated to prevent or diminish immediate thrombus formation at the site of vessel wall injury (athroplasty or other forms of mechanical injury) as well as the development of long-term intima thickening. Also, topical application of rFVIIai was found to block the formation of a thrombus. rFVIIai was shown to have an anti-inflammatory effect in lipopolysaccharide (LPS)-induced sepsis, and postischaemic reperfusion injury was found to be reduced by the administration of rFVIIai. In a limited number of patients undergoing percutaneous transluminal coronary angioplasty (PTCA), rFVIIai was observed to allow PTCA to be performed at lower doses of heparin than what has been reported previously. Recombinant TFPI has been shown to attenuate the lethal inflammatory and coagulopathic response. Furthermore, topical application of rFVIIai has been found to increase the patency rate in a model of graft surgery.

Animals↗
PubMed1999

Use of recombinant, activated factor VII in the treatment of congenital factor VII deficiencies.

BACKGROUND AND OBJECTIVES: Factor VII (FVII) deficiency is a rare coagulation disorder, historically treated with prothrombin complex concentrates or plasma-derived FVII concentrates. We treated such patients (n = 17) with a recombinant, activated FVII preparation. MATERIALS AND METHODS: Twenty-seven spontaneous bleeding episodes were treated and 7 major and 13 minor surgical interventions were carried out. The dosages employed ranged from 8.08 to 70.5 Ig/kg body weight. RESULTS: A mean dose between 22 and 26 Ig/kg was sufficient to normalise the prothrombin time. Fifteen haemarthroses were treated with single doses and results were excellent in 13 cases. In 5/6 bleeding episodes of other types, the treatment gave either excellent or at least effective results. Haemostasis was secured in the 7 major and 13 minor surgical interventions. One patient developed antibodies 4-5 weeks after an extremely high dose. Otherwise, there were no side effects and no evidence of a thrombotic tendency. CONCLUSION: This recombinant concentrate is efficacious in FVII-deficient patients. It is safe since any risk of transmission of blood-borne viruses is eliminated.

Adult↗
PubMed1998

Active site inhibited factor VIIa (DEGR VIIa) attenuates the coagulant and interleukin-6 and -8, but not tumor necrosis factor, responses of the baboon to LD100 Escherichia coli.

Antitissue factor antibody attenuated the coagulopathic and lethal responses to LD100 Escherichia coli, whereas active site inhibited factor Xa inhibited only the coagulopathic response. In this study, we wished to determine: (1) whether active site inhibited factor VIIa blocks the coagulopathic and/or attenuates the lethal effects of LD100 E coli and (2) whether these effects are accompanied by attenuation of the inflammatory cytokine response to LD100 E coli. Eight baboons infused for 2 hours with LD100 E coli also were given five bolus infusions of DEGR VIIa of 280 microg/kg at T = -10 minutes, +2, 4, 6, and 8 hours and observed for changes in vital signs, and the concentrations of hemostatic components (fibrinogen, platelets, fibrin degradation products) and inflammatory mediators (tumor necrosis factor [TNF], interleukin-6 [IL-6], IL-8) at T = 0, 1, 2, 4, 6, and 8 hours. Eight control baboons were also infused with LD100 E coli alone and followed as described above. Four of the eight baboons treated with DEGR VIIa were permanent 7-day survivors versus none in the control group. The mean survival times for the treated and control groups were 116 +/- 22 and 26 +/- 8 hours, respectively. These values differed significantly from each other, (P = .0008). The decrease in platelet and fibrinogen concentrations and the increase in fibrin degradation products observed in the control group were significantly attenuated in the treated group, as was thrombosis of renal glomerular capillaries. Treatment with DEGR VIIa showed no effect on the peak TNF response to LD100 E coli at T = 2 hours (170 +/- 32 v 120 +/- 35 ng/mL). DEGR VIIa, however, did attenuate the IL-6 and IL-8 responses at T = 8 hours (ie, the IL-6 concentrations were 81 +/- 10 for treated and 1,256 +/- 236 for the control groups and the IL-8 concentrations were 28 +/- 3.9 for the treated and 60 +/- 8.2 for the control group). These values for IL-6 and IL-8 differed significantly from each other between the treated and control groups (P = .0001 and .0074, respectively). It should be noted that the initial responses of IL-6 and IL-8 up to T = 4 hours were not attenuated. We concluded that DEGR VIIa treatment attenuates inflammatory, as well as hemostatic system responses to LD100 E coli. We hypothesize that this occurs through interference with the assembly and/or interactions of tissue factor/VIIa complexes.

Animals↗
PubMed1998

Clinical use of recombinant FVIIa (rFVIIa).

Haemostasis is initiated by the complex formed by TF and FVIIa present in the blood (1% of the FVII protein). Recombinant FVIIa, which is active only after having formed complex with TF exposed following tissue damage, has been demonstrated to induce haemostasis in haemophilia patients with life- and limb-threatening bleedings with an efficacy rate of 76-84% in patients having failed on other treatment. Several had proven septicaemia but only one patient developed consumption coagulaopathy during extensive surgical manipulation and removal of myonecrotic tissue. No antibody formation against FVII has been seen in haemophilia patients. In 13 major surgical episodes complete intra- and post-operative haemostasis was achieved. rFVIIa has been used successfully in FVII-deficient patients and has been found to normalise the PT in patients with liver disease and in warfarin treated individuals. Single patients with platelet defects and with vWillebrand's disease type 3 achieved haemostasis with rFVIIa.

Factor VIIa↗
PubMed1998

Local application of recombinant active-site inhibited human clotting factor VIIa reduces thrombus weight and improves patency in a rabbit venous thrombosis model.

OBJECTIVE: To study whether locally administered recombinant inactivated human coagulation factor VIIa (FFR-rFVIIa) would reduce the thrombus formation and improve patency in an experimental venous thrombosis model without inducing systemic changes in the coagulation. DESIGN: Experimental double-dummy randomised study. MATERIALS: In 20 healthy New Zealand White rabbits both jugular veins were exposed under general anaesthesia. METHODS: The thrombi were induced in a 10 mm long jugular vein segment with a combination of chemical destruction of the intima and a restriction of the bloodflow. Each segment was treated with either FFR-rFVIIa or placebo injected directly into the vein. RESULTS: 1.5 mg topically applied FFR-rFVIIa significantly reduced the thrombus weight (p < 0.001). The 30 and the 120 min patency tests were significantly improved (p < 0.05 and p < 0.001, respectively) Plasma analyses (APTT, dilute-TF time, FVII protein) were evaluated as baseline, 3 min after declamping and at sacrifice. No prolongation of the clotting times were seen. FFR-rFVIIa protein was detected in minute amounts (ng/ml); however, this was not enough to prolong the dilute-TF time. CONCLUSIONS: Local application of recombinant active-site inhibited human FVIIa reduced both thrombus weight and improved patency significantly in an experimental venous thrombosis model without affecting the systemic clotting times.

Anesthesia, General↗
PubMed1998

Clinical experience with recombinant factor VIIa.

Recombinant factor VIIa (rFVIIa) represents a major therapeutic advance in the treatment of haemophilia patients with inhibitors. The efficacy and safety of rFVIIa has been extensively studied in over 1900 surgical and non-surgical bleeding episodes in over 400 patients with haemophilia A or B (with or without inhibitors) or acquired haemophilia. Of 103 evaluable surgical bleeding episodes, the response to treatment with rFVIIa was considered to be either excellent or effective in 81%, 86% and 92% of major, minor and dental bleeding episodes, respectively. Treatment has been evaluated in 518 serious bleeding episodes and the response was considered either excellent or effective in 62% of muscle, 80% of ear, nose and throat, 88% of central nervous system, 76% of joint, and 75% of internal or retroperitoneal bleeding episodes. An excellent safety profile has also been demonstrated: of 1957 treatments with rFVIIa, only 16 serious adverse events have been reported that were considered to be possibly, but not necessarily, related to treatment.

Clinical Trials as Topic↗
PubMed1998

The effect of recombinant factor VIIa (NovoSeven) in healthy volunteers receiving acenocoumarol to an International Normalized Ratio above 2.0.

Vitamin K antagonists are most commonly used in long-term thrombosis prophylaxis and the use in patients with cardiovascular disease seems to be increasing. By interfering with the normal hemostatic mechanism, an increased risk of bleeding will arise and administration of human plasma or prothrombin complex concentrates may be necessary. It can be difficult to normalize hemostasis using plasma and prothrombin complex concentrates, because these may be associated with thromboembolic side-effects. The level of factor VII, one of the vitamin-K-dependent coagulation factors, decreases during oral anticoagulant therapy and the administration of recombinant factor VIIa normalizes the prolonged prothrombin time in warfarin-treated rats. After administration of acenocoumarol (International Normalized Ratio > 2), decreased levels of factor X and factor IX (19-46%), protein C (2-20%) and factor VII (4-17%) were found in 28 healthy volunteers. After one dose of recombinant factor VIIa (5, 10, 20, 40, 80, 120, 160, 240, or 320 microg/kg) the International Normalized Ratio and prothrombin time normalized, which may imply an effect on bleeding in individuals receiving oral anticoagulant therapy. The lowest dose (5 microg/kg) normalized the International Normalized Ratio for 12 h and doses > 120 microg/kg normalized it for 24 h. Fragment 1+2 stayed within its normal range in all dose groups, indicating that no systemic coagulation occurred.

Acenocoumarol↗
PubMed1998

The effects of activated factor VII in a cell-based model for tissue factor-initiated coagulation.

The importance of activated factor VII (FVIIa) in coagulation initiated by tissue factor (TF) was illustrated by competition of active site-inhibited FVIIa (FFR-FVIIa; FVIIa treated with D-Phe-Phe-Arg-chloromethyl ketone) with FVIIa in various cell-based assays mimicking TF-initiated coagulation. FFR-FVIIa inhibited the overall initiation process as measured by platelet activation and large-scale thrombin generation on the activated platelet surface. When the individual steps in the initiation process were separated, FFR-FVIIa affected only the reactions taking place on TF-bearing cells, demonstrating that FVIIa takes part only in the very first step in the initiation process. The dissociation constant (Kd) for FVIIa binding to TF and the inhibition constant (Ki) for FFR-FVIIa competing with FVIIa in binding to TF, measured in a factor X activation assay, were both around 10 pmol/l, showing that FVIIa and FFR-FVIIa bound to TF in the extrinsic pathway tenase complex with the same affinity.

Amino Acid Chloromethyl Ketones↗
PubMed1998

Recombinant activated factor VII as a universal haemostatic agent.

Haemostasis is initiated by the complex formed by tissue factor (TF) and activated factor VII (FVIIa) present in the blood [1% of the factor VII (FVII) protein]. Recombinant FVIIa (rFVIIa), enzymatically active only after complex formation with TF exposed following tissue damage, has been demonstrated to induce haemostasis in haemophilia patients with life- and limb-threatening bleedings with an efficacy rate of 76-84% in patients having failed on other treatment. rFVIIa has been successfully used in patients with congenital FVII deficiency and has been demonstrated to normalize the prolonged prothrombin time in patients with liver disease and in warfarin-treated individuals. In patients with thrombocytopenia, rFVIIa shortened the prolonged bleeding time in 50% of the patients treated and a haemostatic effect on acute bleeds in eight patients was demonstrated. One patient with Glanzmann's thrombasthenia and three with Type III von Willebrand's disease were successfully treated with rFVIIa. By exploiting the binding capacity of FVIIa to platelets, rFVIIa, may also be used to enhance normal haemostasis in patients without coagulation defects but suffering from bleedings in organs or at sites with limited possibilities for mechanical haemostasis.

Blood Coagulation Disorders↗