Peripheral-T-cell lymphoma with hemophagocytic histiocytosis localised to the bone marrow associated with inappropriate secretion of antidiuretic hormone

A patient with high fever, loss of weight and profound pancytopenia is reported. Peripheral T-cell lymphoma with hemophagocytosis was diagnosed. Bone marrow was the only localisation of the lymphoma. At presentation there were (i) a coagulopathy consistent with hemophagocytic histiocytosis (ii) the features of the syndrome of inappropriate antidiuretic hormone secretion (SIADH). These different abnormalities disappeared after chemotherapy and reappeared during each of the 2 periods of disease progression. The patient died 6 months after diagnosis without ever achieving complete remission. As far as we are aware this is the first case report of T-cell lymphoma with hemophagocytic syndrome localised to the bone marrow and associated with SIADH.

[Hypersensitivity and resistance to antivitamins K]

During the initial phase or during treatment with oral anticoagulants, hypersensitivity or resistance may be observed, requiring significant changes in prescribed dosage. A thorough knowledge of the mode of action of vitamin K and its antagonists is useful to improve understanding of unexpected response to oral anticoagulant therapy. These abnormal responses may be due to poor compliance to treatment by the patient, insufficient or excessive vitamin K intake, interference with other drugs or abnormalities of the hepatic enzymes which are the target of oral anticoagulant drugs. The search for a cause is justified by the risks associated with these abnormal responses. It must be rigorously undertaken with an accurate interrogation, use of an anticoagulation monitoring leaflet and, if necessary, measurement of plasma concentrations and pharmacokinetics of the anticoagulant drug.

[Value of the determination of D-dimers in the diagnostic approach of venous thrombo-embolic disorders]

The aim of this study is to evaluate the usefulness of plasma measurements of D-dimer using ELISA method and latex agglutination test in the diagnostic approach of venous thromboembolism. Among 126 patients suspected of pulmonary embolism (80 pat.) or deep venous thrombosis of the legs (46 pat.), the diagnosis of acute venous thromboembolism has been confirmed using gold standard invasive techniques (pulmonary angiography and/or contrast venography) in 49% of them. The sensitivity, specificity, negative predictive value and positive predictive value of a D-dimer plasma concentration above 500 ng/ml, on admission day, for the diagnosis of venous thromboembolism are 98%, 66%, 97%, 74% respectively when using the ELISA method, and 87%, 70%, 85%, 74% respectively when using the latex assay. In the 51 patients with a lung scan showing an indeterminate probability of pulmonary embolism, the sensitivity of the ELISA method is very high (94%) but that of the latex assay is low (67%). The repetition of D-dimer measurement on days 2 and 4 following admission has no significant effect on the sensitivity of the ELISA and latex assays. Our results demonstrate that the measurement of plasma D-dimer concentration using latex assay should not be used in the diagnostic approach of venous thromboembolism because the sensitivity of this test is insufficient for ruling out the presence of the disease. On the opposite, a low concentration of plasma D-dimer measured by the ELISA method might be used to rule out acute venous thromboembolism, and avoid invasive radiological techniques, especially in patients with an indeterminate probability lung scan.

[Platelet collection by apheresis with reduced use of citrate: quantitative and qualitative evaluation of three protocols]

Three protocols of platelet collection by apheresis on Cobe Spectra with different citrate concentrations were compared. First we determined until what level we could diminish the ratio anticoagulant/whole blood flow to enhance the efficiency without clotting in the cell separator by platelet aggregates. We found that protocol 2 had a better platelet collection efficiency than the standard protocol 1: respectively 59% versus 52%. Protocol 3 had even a better efficiency but, due to the risk of clotting (5% of the procedures) we rejected it for routine use. We compared in vitro platelet functions of protocols 1 and 2 by aggregometry in vitro. The results with the different aggregating agents indicated that the less citrated environment kept the platelets more functional in vitro. A disadvantage of protocol 2 compared to the standard protocol is the more important number of platelet concentrates that contain more than 10(6) leucocytes.

Familial Dysfibrinogenemia and Thrombophilia

Approximately 250 cases of dysfibrinogenemia have been reported; 55% were asymptomatic (detected by chance), 25% had a tendency to bleeding, and 20% were reported to have a tendency to thrombosis.

To establish a possible association between familial dysfibrinogenemia and thrombophilia, data on cases with both affections were collected in a study within the framework of the SSC Subcommittee on Fibrinogen of the International Society on Thrombosis and Haemostasis. Registry forms of 51 cases were received. Twenty-six cases fulfilled the (arbitrarily chosen) criteria of familial dysfibrinogenemia and of thrombosis not due to other causes. Protein C and protein S deficiency and APC resistance as a cause of thrombosis could not be excluded in probands on anticoagulants or investigated before the discovery of the assays.

The prevalence of dysfibrinogenemia in patients with a history of venous thrombosis is low, i.e. 0.8%, as deduced from 9 studies in 7 countries on 2376 patients. The 26 cases fulfilling the criteria are characterized by predominantly venous thrombosis at a young age. Severe bleeding was rare and limited to bleeding post partum. Homozygosity was established in 2 cases (Marburg and Naples), hypodysfibrinogenemia (less than 1.5 mg antigen per ml) in 5 cases. A high incidence of problems related to pregnancy, in particular thrombosis post partum and spontaneous abortions was noted amongst the 15 women with thrombophilic dysfibrinogen

An association between dysfibrinogenemia and thrombophilia is indicated by studies on relatives of the 26 probands. Analysis of 187 investigated family members showed that thrombophilia affected 20 persons exclusively in the group of 99 relatives with dysfibrinogenemia, no thrombosis was reported in the group of 88 relatives without the defect. Convincing evidence for such an association became apparent for only 5 individual propositi of whom 2 or more family members had both the defect and thrombotic episodes at a young age (Caracas V, Frankfurt IV/Vlissingen, Melun, Naples and Paris V, also named Dusart).

Mainly two mechanisms to explain thrombosis as a consequence of malfunctioning fibrinogen have been suggested: a) A defective binding of thrombin to abnormal fibrin which leads to increased thrombin levels (Malmö, Naples, New York I, Pamplona II, Poitiers), b) A defective stimulatory function of abnormal fibrin in the t-PA mediated fibrinolysis (Argenteuil, Chapel Hill III, Date, New York I, Nijmegen, Pamplona II, Paris V).

Defects at the molecular level, elucidated in 15 out of the 26 cases fulfilling the criteria, were localised in the C-terminal part of the γ-chain (3 cases), in the N-terminal part of the Bβ-chain (3 cases) and in the Aα-chain (4 cases) of fibrinogen. Why a particular molecular defect leads to malfunction of fibrin(ogen) is still unknown.

Familial dysfibrinogenemia and thrombophilia. Report on a study of the SSC Subcommittee on Fibrinogen

Approximately 250 cases of dysfibrinogenemia have been reported; 55% were asymptomatic (detected by chance), 25% had a tendency to bleeding, and 20% were reported to have a tendency to thrombosis. To establish a possible association between familial dysfibrinogenemia and thrombophilia, data on cases with both affections were collected in a study within the framework of the SSC Subcommittee on Fibrinogen of the International Society on Thrombosis and Haemostasis. Registry forms of 51 cases were received. Twenty-six cases fulfilled the (arbitrarily chosen) criteria of familial dysfibrinogenemia and of thrombosis not due to other causes. Protein C and protein S deficiency and APC resistance as a cause of thrombosis could not be excluded in probands on anticoagulants or investigated before the discovery of the assays. The prevalence of dysfibrinogenemia in patients with a history of venous thrombosis is low, i.e. 0.8%, as deduced from 9 studies in 7 countries on 2376 patients. The 26 cases fulfilling the criteria are characterized by predominantly venous thrombosis at a young age. Severe bleeding was rare and limited to bleeding post partum. Homozygosity was established in 2 cases (Marburg and Naples), hypodysfibrinogenemia (less than 1.5 mg antigen per ml) in 5 cases. A high incidence of problems related to pregnancy, in particular thrombosis post partum and spontaneous abortions was noted amongst the 15 women with thrombophilic dysfibrinogen. An association between dysfibrinogenemia and thrombophilia is indicated by studies on relatives of the 26 probands. Analysis of 187 investigated family members showed that thrombophilia affected 20 persons exclusively in the group of 99 relatives with dysfibrinogenemia, no thrombosis was reported in the group of 88 relatives without the defect. Convincing evidence for such an association became apparent for only 5 individual propositi of whom 2 or more family members had both the defect and thrombotic episodes at a young age (Caracas V, Frankfurt IV/Vlissingen, Melun, Naples and Paris V, also named Dusart). Mainly two mechanisms to explain thrombosis as a consequence of malfunctioning fibrinogen have been suggested: a) A defective binding of thrombin to abnormal fibrin which leads to increased thrombin levels (Malmö, Naples, New York I, Pamplona II, Poitiers), b) A defective stimulatory function of abnormal fibrin in the t-PA mediated fibrinolysis (Argenteuil, Chapel Hill III, Date, New York I, Nijmegen, Pamplona II, Paris V).(ABSTRACT TRUNCATED AT 400 WORDS)

Laboratory monitoring of oral anticoagulant therapy

The safety and success of oral anticoagulant treatment are dependent on laboratory control by the prothrombin time test. Until recently, the therapeutic range in prothrombin ratios of 2.0 to 2.5 resulted in greatly different dosage regimes, because of the lack of standardization of the test, particularly its thromboplastin component. Low-dose warfarin was associated with responsive thromboplastin. In North America and many other countries, a high-dose regime from high international sensitivity index thromboplastin caused more bleeding.

French multicentric evaluation of recombinant tissue factor (recombiplastin) for determination of prothrombin time

Recombiplastin, a recombinant a human tissue factor, elaborated by Ortho Diagnostic Systems, produced by Baculovirus and relipidated with highly purified phospholipids, was tested as a new reagent for determining prothrombin time (PT) in a French multicentric study. Its intralaboratory performances, including sensitivity, repeatability, reproducibility and stability, were explored to establish whether its use would reduce the interlaboratory dispersion of PT values, and therefore improve the standardization of oral anticoagulant treatment. The 9 university hospital hematology laboratories involved in this study used the same type of instrument (KC 10). For 10 consecutive days, they determined PTS on a normal plasma pool, plasma dilutions of 1/2, 1/3 and 1/8, 3 identical lyophilized calibrated plasmas, as well as plasmas from 20 normal subjects, 50 patients on oral anticoagulant therapy with Recombiplastin which has an International Sensitivity Index (ISI) of 1, and 2 commercial thromboplastin extracts (ISI #1 or 2). In the patients on anticoagulants, factors VII, X and V were measured when results were conflicting. The intra and interlaboratory reproducibilities of Recombiplastin, calculated on the basis of either PTS expressed in seconds, or of the International Normalized Ratio (INR), were good, with coefficients of variation (CV) similar to those observed with the 5 other reagents used by the different laboratories (2% < CV < 8%). The stability of Recombiplastin was excellent, with no variation in PT after 72 h of incubation at 37 degrees C. A normal PT of 12 s was obtained with Recombiplastin, similar to the values found for the reagents with ISI #2.(ABSTRACT TRUNCATED AT 250 WORDS)

Small abnormal echos after mitral valve replacement with bileaflet mechanical prostheses: predisposing factors and effect on thromboembolism

Early transesophageal echocardiography (TEE) after mitral valve replacement can detect symptomless, non-obstructive thrombus on prosthetic valves and also small filamentous abnormal echoes (SAE). The object of this study is to evaluate their respective frequency and predisposing factors. Between October 1988 and June 1992, 129 consecutive patients underwent mitral valve replacement with a bileaflet prosthesis and had transesophageal echocardiography at an average of 15 +/- 7 days (range: 6-35 days) after surgery. Details of postoperative anticoagulation were analyzed in 99 patients from five surgical centers having comparable postoperative anticoagulation protocols. Among those patients presenting with SAE, 76% had a second transesophageal echocardiography at an average of 145 +/- 166 days after the first examination. Mean age was 56 +/- 13 years. Small filamentous echoes were found in 55 patients (43%). In univariate analysis, independent predictors were age, absence of systolic regurgitation across the mitral prosthesis as observed with continuous Doppler, and the presence of spontaneous echo contrast (SC) in the left atrium: 54 +/- 14 years in the absence vs. 59 +/- 10 in the presence of SAE (p < 0.05); 54% of systolic leak vs. 36% (p < 0.05); 43% of SC vs. 75% (p < 0.00001). In multivariate analysis, spontaneous echo contrast was the only independent predictor for SAE (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Problems of oral anticoagulation in an adult with homozygous protein C deficiency and late onset of thrombosis

We describe a 57-year-old woman with homozygous protein C deficiency and mild thrombotic manifestations consisting of three spontaneous distal deep vein thromboses occurring after the age of 45. Previous surgery and pregnancies had been uneventful. Low but detectable protein C antigen and activity levels (both 20%) were discovered on the occasion of skin necrosis induced by oral anticoagulation. This therapy was interrupted because of skin necrosis and several episodes of disseminated intravascular coagulation (DIC) at the initiation of treatment despite a cautious protocol. No recurrent thromboembolic event has occurred in our patient using prophylactic doses of low molecular weight heparin for 24 months. New therapeutic approaches might be the administration of low molecular weight heparin or oral anticoagulation associated with protein C replacement in the induction period. This case reflects the variability of expression of protein C deficiency as well as the potential hazards of antivitamin K anticoagulation in this disorder.

Comparative effects of enoxaparin and unfractionated heparin in healthy volunteers on prothrombin consumption in whole blood during coagulation, and release of tissue factor pathway inhibitor

In a randomized crossover study twelve healthy male volunteers (23.5 +/- of 4.8 years, 73.0 +/- 6.4 kg, 180.8 +/- 5.7 cm) received one subcutaneous injection of either enoxaparin (EN) at 40 mg or 1 mg kg-1, or unfractionated heparin (UH) at 5,000 IU at one week intervals. Area under curves (AUC) of Anti-Xa and Anti-IIa activities correlated with EN dose. The relative effectiveness of EN versus UH 5,000 U as assessed by AUC ratio (EN/UH) was 7 and 15 for Anti-Xa activity, 1.3 and 3.1 for Anti-IIa activity after sc injection of EN 40 mg (4,000 Anti-Xa IU and 1,200 Anti-IIa U) and 1 mg kg-1 (7,300 +/- 640 Anti-Xa IU and 2,190 +/- 290 Anti-IIa IU) respectively. In volunteers receiving EN, a dose dependent inhibition of thrombin generation rate in platelet depleted plasma (PDP), measured with a new and simple chromogenic thrombin generation assay, was observed when compared with baseline values. Similarly, intrinsic prothrombin activation in whole blood, evidenced by measuring residual factor II in serum 2 hours after clotting (prothrombin consumption test: PC), was inhibited in a dose dependent manner. In UH treated volunteers, although the inhibition of thrombin generation rate in PDP was similar to that observed with EN 40 mg, prothrombin consumption in whole blood was not significantly modified. Tissue factor pathway inhibitor (TFPI) activity release was increased similarly for UH and EN 40 (1.4 fold increase above baseline values) and 1.9 fold for the higher dose of EN. The discrepancy between prothrombin consumption in whole blood and inhibition of thrombin generation rate in PDP in the UH and not in the EN group strongly suggests that UH and not EN is influenced by the presence of a platelet component. This could be formed during thrombin induced platelet activation. Platelet factor 4 is a possible candidate. Another hypothesis involves the role of TFPI-UH complex anticoagulant activity which might be inhibited more during whole blood coagulation than the TFPI-EN complex.

Multicentric evaluation of a new assay for prothrombin fragment F1+2 determination

A multicenter study of a recently developed ELISA for the determination of prothrombin fragment F1+2 was performed in order to evaluate analytical and clinical aspects. Mean intra-assay and inter-assay reproducibility were found to be 11.0 and 12.6%, respectively. The measuring range covered by the calibration curve reaches from 0.04 to 10.0 nM/l F1+2. Testing 133 healthy subjects a reference range of 0.37 to 1.11 nM/l F1+2 (2.5-97.5 percentile) with a median of 0.66 nM/l F1+2 was calculated. Minor difficulties with blood sampling (venous occlusion for 2 min) did not affect F1+2 plasma concentrations. Significantly increased F1+2 levels were measured in patients with leukemia (p < 0.0001), severe liver disease (p < 0.005) and after myocardial infarction (p < 0.01). Elevated F1+2 concentration before the beginning of heparin therapy (1.25 nM/l) decreased to 0.77 nM/l (p < 0.0001) after 1 day of therapy. For patients in the stable phase of oral anticoagulant therapy decreasing F1+2 concentrations were measured with increasing INR. F1+2 levels were already significantly reduced in patients with INR < 2.0 (0.56 nM/l; p = 0.0005). Thus F1+2 determination may be helpful in identifying activation processes as well as in monitoring anticoagulant therapy.

[Hirudin and hirudin fragments]

Hirudin is a potent and specific thrombin inhibitor: compared with heparin thrombin inhibition occurs directly and does not require the presence of plasma cofactors. Recombinant hirudin is well tolerated in animals and in healthy volunteers. Its clearance half-life after IV administration range from 1 to 2 hours and its bioavailability after subcutaneous administration reaches 75%. In most of the experimental models the ratio of the haemorrhagic side effect against the antithrombotic efficacy is satisfactory. Hirudin analogs are mono or bivalent according to their recognition site on thrombin. Bivalent derivatives (Hirulogs) have been mostly evaluated: they exhibit pharmacologic properties similar experimental to that of recombinant hirudin and have been successfully used in several thrombosis models and in healthy volunteers. Taking into account these data the most appropriate use for hirudin and hirudin derivatives should be clinical situations where the role of thrombin is important or which are only partially controlled by heparin therapy.

Prevention of venous thromboembolism after surgery: a review of enoxaparin

This review discusses the problem of deep vein thrombosis (DVT) after operation and identifies three levels of risk of DVT: low (less than 10 per cent), moderate (10-40 per cent) and high (40-80 per cent). Special emphasis is placed on the most recent prophylactic treatment, low molecular weight heparins (LMWHs), particularly enoxaparin. Several LMWHs are now available, but they differ slightly and each must be evaluated on its own merits. In general, however, LMWHs are both effective and safe in those patients at moderate or high risk of DVT. Thromboprophylaxis is cost effective when analysed using health-economic methodology.

Acquired von Willebrand disease: correction of hemostatic defect by high-dose intravenous immunoglobulins

High-dose intravenous immunoglobulins (ivIG) were used in a 57-year-old patient with acquired von Willebrand disease in order to correct a hemostatic defect before pneumonectomy for lung carcinoma. IvIG induced a rapid and complete correction of factor VIII (F VIII) and von Willebrand factor (vWF) and allowed surgery without additional factor coverage. F VIII and vWF returned to baseline values within 10 days after ivIG.

[Elements of choice of thrombolytic agents in myocardial infarction]

Five thrombolytic agents have been used in the acute phase of myocardial infarction: streptokinase, recombinant tissue plasminogen activator (rt-PA) and its acyl enzyme (APSAC), urokinase and pro-urokinase. Experience with the latter two agents is much more limited. The antigenicity, biological half-life, fibrino-specificity and cost are important parameters to be taken into account when choosing a therapeutic agent. The doses expressed in different units or in milligrams vary with the product used. Large scale clinical trials have not shown improved efficacy of new thrombolytic agents. The role of associated treatments, aspirin and/or heparin and their respective doses, the timing of their administration are also important elements in the evaluation of efficacy judged by the frequency of coronary recanalisation and early reocclusion. The haemorrhagic risk is difficult to assess and seems more related to heparin therapy than the prescription of aspirin. Mutants of rt-PA obtained by genetic engineering and other new thrombolytics are currently under evaluation to try and obtain new, more effective and safer thrombolytic agents.

Correlation between anti-Xa and occurrence of thrombosis and haemorrhage in post-surgical patients treated with either Logiparin (LMWH) or unfractionated heparin. Post-surgery Logiparin Study Group

A total of 1290 patients (Pts) undergoing general surgery were enrolled in a randomized, multicentre double-blind study in order to investigate the efficacy and safety of two different doses of a low molecular weight heparin (LMWH) (Logiparin) for the prevention of deep vein thrombosis. Patients were randomized to either 5,000 IU unfractionated heparin twice daily, 2,500 anti-Xa or 3,500 anti-Xa units of Logiparin once daily. Each treatment was given subcutaneously two hours before surgery and continued for seven to ten days. All coagulation tests were performed blindly in a core laboratory. Blood samples were collected before surgery and then 3 hours after injection on Day 3 and 5 after surgery. Anti-Xa amidolytic activities were significantly higher in the two LMW Heparin groups than in the unfractionated heparin group (mean peak levels +/- s.e.m. on Day 3: 0.097 +/- 0.004; 0.152 +/- 0.004 and 0.034 +/- 0.003 IU respectively). As expected a significant correlation was observed between anti-Xa activity and the dose of LMW Heparin injected. The correlation coefficient was higher when the doses were expressed in anti-Xa units/kg body weight. However, the body weight accounts for only 16% of the interindividual variability of anti-Xa activity. Therefore, there is no clear evidence to suggest that weight-adjusted doses should be recommended when this LMW Heparin is used as prophylactic treatment in general surgery. A weak negative correlation was found between anti-Xa activity and thrombosis as demonstrated by a positive radiolabelled fibrinogen uptake test and confirmed by positive phlebography. No significant correlation was demonstrated between anti-Xa activity and the occurrence of postoperative bleeding.

Lupus anticoagulant associated with primary malignant lymphoplasmacytic lymphoma of the spleen: a report of four patients

Primary lymphoma of the spleen is characterized by predominant splenomegaly. Lymphoplasmacytic malignant lymphoma of the spleen, of low malignancy in the Kiel classification, low and intermediate grade in the National Cancer Institute Working Formulation (NCIWF), is rare. It is often associated with a monoclonal immunoglobulin M (IgM). Four patients presenting with primary splenic lymphoma of plasmacytic type associated with a high level of monoclonal IgM and a lupus anticoagulant (LA) are described. This association has not previously been reported. In contrast with the usual heterogeneity of LA, this LA is relatively homogeneous with an important prolongation of the prothrombin time (greater than 18 sec for a control of 12), more prolonged partial thromboplastin time (PTT) of the mixture patient + control plasma than PTT of the patient plasma. Despite the important coagulation abnormalities, none of these four patients has presented any hemorrhagic or thrombotic complications, even during major surgery such as splenectomy. The lupus-like anticoagulant effect ran parallel with the monoclonal IgM. Survival, after splenectomy and chemotherapy, appears to be favourable: three patients are alive with survivals of greater than or equal to 7 years. The follow-up is as yet too short for the last patient.

[Heparin in the treatment and secondary prevention of myocardial infarction. A critical review of the main trials]

The aim of this article is to assess the therapeutic value of standard heparin in the acute phase and secondary prevention of myocardial infarction. Only clinical trials with an adequate methodology have been analysed. In patients having undergone thrombolytic therapy associated with aspirin, heparin slightly reduces the mortality but only during the period of its administration. In a metaanalysis of approximately twenty clinical trials of patients not receiving thrombolytic or aspirin therapy, heparin was associated with a significant reduction of deep vein thrombosis, pulmonary embolism, recurrent myocardial infarction and cerebrovascular accidents. In the context of secondary prevention of myocardial infarction, the administration of a moderate dose of subcutaneous heparin resulted in a beneficial effect on morbidity and mortality in one published trial. The use of low molecular weight heparins for the prevention of coronary thrombosis merits attention because of the pharmacological and pharmacokinetic properties of these products.

Prevention of deep vein thrombosis after hip replacement: randomised comparison between unfractionated heparin and low molecular weight heparin

OBJECTIVE

To evaluate the efficacy and safety of two subcutaneous prophylactic regimens for postoperative deep vein thrombosis after total hip replacement.

DESIGN

Prospective open randomised multicentre trial.

SETTING

28 European departments of orthopaedic surgery.

INTERVENTION

All patients had bilateral phlebography 10 days after surgery. 31 patients receiving low molecular weight heparin and 29 receiving unfractionated heparin were excluded from the efficacy analysis for various reasons.

PATIENTS

349 patients undergoing total hip replacement between September 1988 and May 1989. 174 patients received subcutaneously a low molecular weight heparin (Fraxiparine) with anti-factor Xa activity of 41 IU/kg/day for three days, then 62 IU/kg/day from day 4 to day 10. 175 patients received subcutaneous unfractionated heparin at intervals of eight hours; doses were adjusted to maintain the activated thromboplastin time at two to five seconds above control values.

MAIN OUTCOME MEASURE

Total incidence of deep vein thrombosis and incidence of proximal deep vein thrombosis on bilateral phlebography.

RESULTS

The total incidence of deep vein thrombosis was 16% in patients receiving unfractionated heparin and 12.6% in patients receiving low molecular weight heparin (p = 0.45), and the incidence of thrombosis of the proximal veins was 13.1% and 2.9% respectively (p less than 0.001). Four patients receiving unfractionated heparin and one receiving low molecular weight heparin developed pulmonary embolism. The incidence of bleeding complications was low and comparable in the two groups.

CONCLUSION

Low molecular weight heparin is at least as effective as unfractionated heparin in preventing deep vein thrombosis and is more effective at preventing thrombosis of the proximal veins in patients undergoing hip replacement. Low molecular weight heparin is not more likely to cause bleeding complications and is simpler to give than unfractionated heparin.

Rapid aequorin loading into platelets in the presence of DMSO--characteristics of the responses (changes in light transmission and in calcium) to various agonists

We have looked at different parameters which could modify platelet behaviour during and after aequorin loading in the presence of DMSO. There is a decreased platelet reactivity in response to ADP, PAF and A-23,187 which appears to be mainly due to the exposure to EGTA during washing and loading and the 1 ml volume of the test suspension. All the studied agonists (including PMA) which elicit aggregation are able to induce an intracellular Ca2+ change detected with the aequorin probe. By contrast, epinephrine alone induces neither aggregation nor Ca2+ rise, but potentiates the responses to ADP. Different consecutive phases in Ca2+ changes after stimulation with ADP, PMA and A-23,187 can be evidenced. In the presence of external Ca2+, the second component of the Ca2+ change evoked with ADP is dependent on aggregation and the subsequent TXA2 synthesis. When the external medium is Ca2+ depleted, the two Ca2+ peaks induced by ADP disappear whereas a Ca2+ rise persists (endogenous mobilization) with the other agonists, being independent of TXA2 and ADP release. Ca2+ mobilization parallels activation with A-23,187 but not with low concentrations of thrombin.

Importance of plasminogen activator inhibitor type 1 (PAI-1) for preventing single chain urokinase plasminogen activator (scu-PA) conversion into two chain urokinase plasminogen activator (tcu-PA) in plasma in vitro

We have studied the effects of PAI-1 on the conversion of scu-PA into tcu-PA in vitro in plasma containing or not a 125I-fibrin clot by determining tcu-PA activity on S2444. Two preparations of PAI-1 have been used, a fraction of medium conditioned with the monkey Vero cells (Vero-Prep), the antiurokinase activity of which is inhibited at 83% by anti PAI-1 IgG, or purified human PAI-1 from HT 1080 fibrosarcoma cells. Scu-PA purified from human kidney cells has been treated with diisopropylfluorophosphate before use. In plasma, conversion of scu-PA into the tc form is accelerated by addition of anti PAI-1 IgG. In plasma containing a clot, generation of tcu-PA, is considerably delayed after addition of the Vero-Prep or human PAI-1. Clot lysis is also decreased but to a lesser extent than it would be expected from the level of tcu-PA activity. Addition of anti PAI-1 antibodies shortens the lag phase before tcu-PA appears and moderatly accelerates clot lysis. These results demonstrate the importance of PAI-1 for the stability of scu-PA in plasma in vitro by delaying its conversion into tcu-PA.

[Safety of donors, quality of products, how much to reduce the quantity of citrate]

We examined 1,053 blood samples from 48 donors, for the effect of gradual reduction of citrate. We observed that: 1--Platelet count does not show any significant variation between 1/8 to 1/18 ratio. 2--In 13.3% of the cases, platelet clumping starts at 1/18 ratio. 3--There was no significant variation of the thrombin plasma level between 1/8 to 1/16 ratio (by measuring thrombin/ATIII complex). Our results show clearly that we can reduce the citrate ratio to 1/14 without expecting any adverse effect. Therefore we designated 1/14 as the security ratio. Parallel to this we also found that the average level +/- SD of ionized calcium is 100 +/- 10 muMol at 1/14 ratio.

Pharmacokinetics and biodistribution of technetium 99m labelled standard heparin and a low molecular weight heparin (enoxaparin) after intravenous injection in normal volunteers

For a better understanding of low molecular weight heparin pharmacokinetics, 99m technetium labelled heparin and enoxaparin were injected intravenously to four normal volunteers, after approval by the Ethics Committee and preliminary animals studies. In vitro and in vivo, the labelled products proved to be stable and identical to the non-labelled drugs. Radioactivity curves in blood, organs and urines were similar for both products. Anti Xa plasma half-life was 3 times longer for enoxaparin than for heparin. Anti IIa plasma half-lives were similar. However, radioactivity persisted much longer than biological activities for both products. After chromatography, most of the radioactivity was bound to AT III, where an anti Xa activity peak was also detected. The anti Xa activity peak seen after adding AT III to plasma was much higher with heparin than with enoxaparin. In urine, biological activities, measured with AT III supplementation, were higher with enoxaparin than with heparin. These results suggest that phenomena other than biodistribution are responsible for the differences in pharmacokinetics observed between these two products. The two most likely explanations are differences in metabolism and/or a release of an endogenous factor.

Does increased platelet aggregation have a prognostic value in the deterioration of background diabetic retinopathy? The Damad Study Group

Many case-control studies have suggested that increased platelet aggregation (PA) could be involved in the pathogenesis of diabetic microangiopathy. However, longitudinal data are needed to support this hypothesis. We consider here such an approach in the placebo group (93 diabetic patients) of a controlled clinical trial on the effect of PA inhibitors in the treatment of diabetic retinopathy (Damad program). We have measured spontaneous PA and PA induced by ADP, collagen and arachidonic acid before treatment and yearly during a 3-year period. The assessment of retinopathy was based on the changes in the number of microaneurysms present in the macular field as seen on fluorescein angiograms during follow-up. PA was estimated by maximal decrease in optical density. The lowest ADP concentration still able to induce irreversible aggregation was also determined. No significant correlations between any baseline PA measurements and end point criterion were found (all correlation coefficients lower than 0.20). No significant changes in mean PA were observed during follow-up. Within-subject variation of PA was markedly large accounting for 61% to 98% of the total variance of various measurements. Allowances for the main characteristics of diabetes made no substantial difference to the results. These negative findings can be partly attributed to the lack of reliability of PA tests. In our study, we conclude that PA tests are not useful measures for the prediction of evolution of background diabetic retinopathy.

Aequorin-detected calcium changes in stimulated thrombasthenic platelets. Aggregation-dependent calcium movement in response to ADP

Calcium changes in normal and thrombasthenic platelets were recorded using the PICA-apparatus. Aequorin was loaded in the presence of DMSO, EGTA and PGE1. Platelets of three patients with type I thrombasthenia stimulated with A-23, 187, thrombin, PMA in the presence 1 mM Ca++ and 1 mM Mg++ were able to normally raise their calcium concentrations. The maximal values could be found below the normal range with collagen, ADP and PAF-acether. Calcium mobilization from internal stores in response to thrombin was normal. There were two calcium peaks in normal platelets stimulated with ADP. The second one was suppressed by omitting fibrinogen, stirring, or by adding aspirin, and was absent in thrombasthenic platelets. Thus the GP IIb-IIIa complex is not a prerequisite for calcium fluxes but is involved, when weak agonists such ADP are used, through an aggregation-dependent reinforcement of platelet activation.

Ultraviolet irradiation of platelet concentrates: feasibility in transfusion practice

Ultraviolet (UV)-B irradiation abolishes lymphocyte functions (the ability to respond and to stimulate) in mixed lymphocyte culture (MLC). This effect may have practical application in the prevention or reduction of transfusion-induced alloimmunization against HLA class I antigens. To study this, platelet concentrates (PCs) were obtained with a cell separator, suspended in autologous plasma in a final volume of 400 mL, and transferred into a large (22 X 30 cm) cell culture bag. This plastic showed a good transmittance of UV-B rays at 310 nm (54%). PCs were placed between two quartz plates (surface of irradiation = 25 X 37 cm), and the two sides were irradiated simultaneously. Energy delivered to the surface of the plastic bag was automatically monitored. The ability to respond (in MLC and to phytohemagglutinin) and to stimulate allogeneic lymphocytes was completely abolished with energy of 0.75 J per cm2 (irradiation time less than 3 min). The temperature increase during irradiation was negligible. Platelet aggregation (collagen, adrenalin, ADP, arachidonic acid, ristocetin) was not impaired if UV-B energy was below 3 J per cm2. Recovery and survival of autologous 111In-labeled platelets were studied in four volunteers; no differences were found between UV-B-treated (1.5 J/cm2) platelets and untreated platelets. These results show that a large-scale clinical trial using UV-B-irradiated PCs to prevent HLA alloimmunization is feasible.

In vitro effect on Heptest of low molecular weight heparin fractions and preparations with various anti-IIa and anti-Xa activities

The Heptest heparin assay has recently been introduced, and evaluated for the laboratory monitoring of patients receiving low molecular weight heparins (LMWH). The aim of the present study was to elucidate the relative role on the Heptest assay of the anti-factors Xa and IIa activities present in the three types of compounds that possess: 1. exclusively anti-Xa activity (LF1: LMWH fractions with MW ranging from 1,200 to 4,200 D.); 2. both anti-Xa and anti-IIa activities (LF2 with MW from 4,800 to 12,000 D.); 3. exclusive anti-IIa activity (Hirudin and Dermatan Sulfate). All compounds studied demonstrated dose-dependent activities in both amidolytic and clotting assays. The LF2 in contrast to the LF1, additionally enhanced the clotting times of Heptest. This enhancement was shown to be due to the anti-Factor IIa activity of the agents. Heptest does not exclusively reflect Anti-Xa activity since it is influenced by agents containing exclusive anti-IIa activity like Hirudin and Dermatan Sulfate. At low concentrations of LF2, Heptest measures predominantly the anti-factor Xa activity while at higher concentrations it is influenced by the combined activity of anti-factor Xa and anti-factor IIa. However, Heptest sensitivity to anti-factor IIa is significantly lower than for anti-Xa activity.

Factor VII activation and menopausal status

The incidence of coronary heart disease (CHD) is higher in postmenopausal or oophorectomised women than in premenopausal women of the same age. The difference cannot be explicable in terms of conventional CHD risk factors. Since factor VII may be relevant to the pathogenesis of CHD, we have investigated the menopause-related changes in factor VII activation in 228 healthy women aged 45-54 years. A standard factor VII clotting assay (FVIIc) and a factor VII antigen assay (FVIIag) were carried out on the same plasma samples. Both FVIIc and FVIIag levels were significantly higher in postmenopausal than in premenopausal women. Despite the strong correlation between the two assays (r = 0.80), the FVIIc/FVIIag ratio was positively and significantly associated with the menopause, suggesting that activated factor VII form might in part account for the high FVIIc levels in postmenopausal women. With respect to the type of menopause, the highest levels of both FVIIc and FVIIc/FVIIag ratio were found in women having undergone bilateral oophorectomy. These results suggest that raised factor VII coagulant activity may contribute to an increased risk of CHD in postmenopausal women.

Degradation of fibrinogen by tissue plasminogen activator. Consequences for fibrin polymerization

In patients treated with tissue plasminogen activator (t-PA), there was a marked increase in concentration of fibrinopeptide A (fpA). The purpose of this study was to analyse the activation of coagulation in plasma treated in vitro by pharmacological doses of t-PA. From our results, it appears that fpA release due to direct interaction of fibrinogen with t-PA, in the absence of plasminogen, is very low and not observed with pharmacological doses of t-PA. In contrast in the presence of plasminogen, the release of fpA is much higher and induces fibrin formation concomitantly to fibrinogen degradation.