Thrombosis research
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Thrombosis research · May 1994
Comparative StudyAssessment of hypercoagulability in patients with cancer using the Sonoclot Analyzer and thromboelastography.
Patients with cancer have an increased incidence of thrombosis and abnormal haemostasis detectable by sophisticated laboratory tests. Whether abnormalities in such highly sensitive assays is clinically relevant to bleeding or thrombosis is not clear. The thromboelastograph (TEG) and Sonoclot analyzers assess the coagulation process in whole blood and may therefore be physiologically more relevant than assays of isolated haemostatic components. ⋯ There were no significant coagulation changes in patients with benign colon or breast disease. In conclusion, hypercoagulability was detected in a high proportion of breast and colorectal cancer patients by both techniques. The clot rates of the TEG and Sonoclot were significantly correlated but the latter was abnormal in a greater proportion of cancer patients.
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Thrombosis research · Mar 1994
Comparative StudyMasking of heparin activity in the activated coagulation time (ACT) by platelet procoagulant activity.
The effect of platelet procoagulant activity in the Activated Coagulation Time (ACT) was measured in whole blood anticoagulated with various levels of heparin before or after reversal with protamine. Similar studies were carried out on blood anticoagulated with hirudin to distinguish procoagulant activity from heparin neutralization in platelet preparations. At 0.5-1.0 units/mL antithrombin activity with heparin or hirudin, the ACT was lowered progressively by the addition of increasing concentrations of lysed platelets to as much as 20 seconds below the baseline clotting time obtained with unanticoagulated blood samples. ⋯ An increase in platelet microparticles was associated with a decrease in the amount of protamine needed to reach the baseline ACT in blood samples removed from the circuit at various time points during recirculation. A chromogenic anti-Factor Xa assay of heparin did not show a change with increasing microparticle concentration during recirculation. These findings indicate a masking of heparin activity by the procoagulant activity of platelet membrane microparticles that could affect reversal of heparin based on the ACT.
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Thrombosis research · Jan 1994
Neutralization of the anticoagulant activity of low molecular weight heparin LU 47311 (Clivarin) in man by protamine chloride.
Bleeding induced by unfractionated heparin (UFH) can be antagonized by protamine as shown by normalization of thrombin time and aPTT. In order to learn about the neutralization capacity of protamine against the anticoagulant effects of LU 47311 a comparison study vs UFH was performed in 12 healthy male volunteers. ⋯ A rebound phenomenon of LU 47311 after protamine chloride was not detected. The platelet system remained unchanged.
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Thrombosis research · Dec 1993
SIN-1 partially and RGDS totally counteracts platelet aggregation as assessed in vitro by two independent whole blood methods.
The cyclic GMP stimulant SIN-1 and the GP IIB/IIIA receptor antagonist RGDS were compared with regard to platelet antiaggregatory effects as measured in vitro by filtragometry and by whole blood aggregometry. In filtragometry platelet aggregation is measured as the time to partial occlusion of a filter in the test unit. Beta-thromboglobulin concentrations increased over the filter (p < 0.002) indicating that in filtragometry part of the mechanism of aggregation could be platelet activation across the filter. ⋯ Maximal SIN-1 platelet antiaggregatory effects were less (p < 0.04, filtragometry and p < 0.01, whole blood aggregometry) than for RGDS. SIN-1 concentrations in the 10(-4) M range had no further antiaggregatory effects. In conclusion, with two principally different methods for the assessment of whole blood platelet aggregation, SIN-1 was found to be a partial antagonist while RGDS a total antagonist.
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Thrombosis research · Apr 1993
Evaluation of a low molecular weight heparin as an anticoagulant in a model of cardiopulmonary bypass surgery.
Heparin, the classically used anticoagulant in cardiopulmonary bypass surgery, has several disadvantages such that alternate anticoagulants are being sought. Previous reports have described questionable safety with the clinical use of low molecular weight (LMW) heparin in cardiac surgery. The dog cardiopulmonary bypass model described herein may provide a useful means to study the pharmacology of new drugs prior to clinical use. ⋯ Post-operative blood loss and fibrin deposition in the arterial line filters were measured. Our findings showed there was no significant blood loss (heparin 452 +/- 67 gms; LMW heparin 289 +/- 82 gms) and no significant fibrin deposition (heparin 22 +/- 3 gms; LMW heparin 28 +/- 7 gms) with the LMW heparin. These findings suggest that this LMW heparin should be safe and effective at the studied bolus dose as an anticoagulant for use in cardiopulmonary bypass surgery, and that protamine should be used to reverse the anticoagulant response after surgery.