Mechanism of Heparin Rebound

1979 ◽  
Author(s):  
I. Fabian ◽  
M. Aronson
Keyword(s):  
Clotting Time ◽  
Coagulation Time ◽  
Working Hypothesis ◽  
Plasma Enzymes

Heparin rebound is occasionally encountered following protamin sulfate administration for the neutralization of excess of heparin. In these situations the anticoagulatory properties of heparin are initially abolished, but within several hours the blood display again an increased clotting time. The purpose of this work was to try to reproduce the phenomenon under in vitro conditions, and to provide a working hypothesis for its explanation. Under the condition used the following parameters were obtained (according to the APTT method): clotting time of untreated plasma 50-55 seconds; with the addition of 4 units heparin/ml plasma>3 minutes; and with the addition of 50-100 μg of protamin to the heparinized plasma the clotting time reverts to 50-55 seconds. It was, however, found that incubation of heparin-protamin complex with the plasma at 37° for several hours, reduced the effectivity of the Protamin, in other words, a longer coagulation time was observed. Subsequently, we found by electrophoretical methods that (heparin bound) protamin is proteolitically degraded upon incubation in plasma, the anticoagulatory properties of the heparin remaining intact. In summary, our results are compatible with the hypothesis that heparin rebound can be explained by the degradation of Protamin by plasma enzymes and the release of this newly available heparin in to the circulation. The importance of this phenomenon in conjunction with other observations previously described by us are discussed.

Mechanism of Heparin Rebound

1979 ◽  
Author(s):  
I. Fabian ◽  
M. Aronson
Keyword(s):  
Clotting Time ◽  
Coagulation Time ◽  
Working Hypothesis ◽  
Plasma Enzymes

Heparin rebound is occasionally encountered following protamin sulfate administration for the neutralization of excess of heparin. in these situations the anticoagulatory properties of heparin are initially abolished, but within several hours the blood display again an increased clotting time. The purpose of this work was to try to reproduce the phenomenon under in vitro conditions, and to provide a working hypothesis for its explanation. Under the condition used the following parameters were obtained (according to the APTT method): clotting time of untreated plasma 50-55 seconds; with the addition of 4 units heparin/ml plasma>3 minutes; and with the addition of 50-100 μg of protamin to the heparinized plasma the clotting time reverts to 50-55 seconds. It was, however, found that incubation of heparin-protamin complex with the plasma at 37° for several hours, reduced the effectivity of the protamin, in other words, a longer coagulation time was observed. Subsequently, we found by electrophoretical methods that (heparin bound) protamin is proteolitically degraded upon incubation in plasma, the anticoagulatory properties of the heparin remaining intact. in summary, our results are compatible with the hypothesis that heparin rebound can be explained by the degradation of protamin by plasma enzymes and the release of this newly available heparin Into the circulation. The importance of this phenomenon in conjunction with other observations previously described by us are discussed.

Effect of i. v. and Oral Administration of Heparinoids G31150, G31150-A and of Nitrilotriacetic Acid on Blood Coagulation

1971 ◽  
Vol 25 (01) ◽  
pp. 187-200 ◽  
Author(s):  
C. L Jarrett ◽  
L. B Jaques
Keyword(s):  
Absorption Spectrum ◽  
Oral Administration ◽  
Blood Coagulation ◽  
Intravenous Injection ◽  
Anticoagulant Activity ◽  
Chelating Agent ◽  
Nitrilotriacetic Acid ◽  
Clotting Time ◽  
Coagulation Time

SummaryThe heparinoid G31150-A and nitrilotriacetic acid (NTA) were compared with heparinoid G31150 and heparin. In vitro the anticoagulant activity of NTA was 1/20000, G31150-A 1/8th and G31150, 1/10th of heparin. On intravenous injection in dogs, the degree and duration of hypocoagulability was about the same for the two heparinoids but less than predicted from the effects in vitro. Injection of 25 mg NTA/kg caused a slight increase in coagulation time lasting over 4 hours. When heparinoid G31150-A and NTA were given orally, there was an increase in clotting time of blood and metachromatic activity appeared in the urine. The greatest amount of activity was excreted with the highest dose of NTA alone. Microelectrophoresis of the urinary concentrate indicated the excreted material after NTA was not heparin, but another mucopolysaccharide; after G31150, a heparinoid. These results were confirmed by the resulting absorption spectrum of the dye obtained with added urinary concentrate. It is suggested that the effects produced when a chelating agent is given with oral heparin and heparinoids may be due to the release of a mucopolysaccharide.

The uncalibrated prothrombinase-induced clotting time test

2010 ◽  
Vol 30 (04) ◽  
pp. 212-216 ◽  
Author(s):  
R. Jovic ◽  
M. Hollenstein ◽  
P. Degiacomi ◽  
M. Gautschi ◽  
A. Ferrández ◽  
...  
Keyword(s):  
Factor Xa ◽  
Heparin Therapy ◽  
Thrombin Inhibitors ◽  
Coagulation Cascade ◽  
Diagnostic Tools ◽  
Direct Thrombin Inhibitors ◽  
Functional Assay ◽  
Clotting Time ◽  
Coagulation Time ◽  
Time Test

SummaryThe activated partial thromboplastin time test (aPTT) represents one of the most commonly used diagnostic tools in order to monitor patients undergoing heparin therapy. Expression of aPTT coagulation time in seconds represents common practice in order to evaluate the integrity of the coagulation cascade. The prolongation of the aPTT thus can indicate whether or not the heparin level is likely to be within therapeutic range. Unfortunately aPTT results are highly variable depending on patient properties, manufacturer, different reagents and instruments among others but most importantly aPTT’s dose response curve to heparin often lacks linearity. Furthermore, aPTT assays are insensitive to drugs such as, for example, low molecular weight heparin (LMWH) and direct factor Xa (FXa) inhibitors among others. On the other hand, the protrombinase-induced clotting time assay (PiCT®) has been show to be a reliable functional assay sensitive to all heparinoids as well as direct thrombin inhibitors (DTIs). So far, the commercially available PiCT assay (Pefakit®-PiCT®, DSM Nutritional Products Ltd. Branch Pentapharm, Basel, Switzerland) is designed to express results in terms of units with the help of specific calibrators, while aPTT results are most commonly expressed as coagulation time in seconds. In this report, we describe the results of a pilot study indicating that the Pefakit PiCT UC assay is superior to the aPTT for the efficient monitoring of patients undergoing UFH therapy; it is also suitable to determine and quantitate the effect of LMWH therapy. This indicates a distinct benefit when using this new approach over the use of aPPT for heparin monitoring.

Comparison of the Anticoagulant and Antithrombotic Effects of Synthetic Thrombin and Factor Xa Inhibitors

1990 ◽  
Vol 63 (02) ◽  
pp. 220-223 ◽  
Author(s):  
J Hauptmann ◽  
B Kaiser ◽  
G Nowak ◽  
J Stürzebecher ◽  
F Markwardt
Keyword(s):  
Factor Xa ◽  
Thrombin Inhibitors ◽  
Factor Xa Inhibitors ◽  
Venous Stasis ◽  
Clotting Time ◽  
Thrombosis Model ◽  
Activity Factor ◽  
Antithrombotic Effects

SummaryThe anticoagulant effect of selected synthetic inhibitors of thrombin and factor Xa was studied in vitro in commonly used clotting assays. The concentrations of the compounds doubling the clotting time in the various assays were mainly dependent on their thrombin inhibitory activity. Factor Xa inhibitors were somewhat more effective in prolonging the prothrombin time compared to the activated partial thromboplastin time, whereas the opposite was true of thrombin inhibitors.In vivo, in a venous stasis thrombosis model and a thromboplastin-induced microthrombosis model in rats the thrombin inhibitors were effective antithrombotically whereas factor Xa inhibitors of numerically similar IQ value for the respective enzyme were not effective at equimolar dosageThe results are discussed in the light of the different prelequisiles and conditions for inhibition of thrombin and factor Xa in the course of blood clotting.

The Effect of Lysed Platelets on Neutralization of Heparin In Vitro with Protamine as Measured by the Activated Coagulation Time (ACT)

1991 ◽  
Vol 66 (02) ◽  
pp. 213-217 ◽  
Author(s):  
Arthur P Bode ◽  
William J Castellani ◽  
Edna D Hodges ◽  
Susan Yelverton
Keyword(s):  
Platelet Rich Plasma ◽  
Coagulation Time ◽  
Platelet Factor ◽  
Platelet Suspension ◽  
Antiheparin Activity ◽  
Unit Increase ◽  
Heparin Anticoagulation ◽  
Heparin Activity ◽  
Activated Coagulation Time

SummaryThe effect of lysed platelets on the activated coagulation time (ACT) was studied in heparinized whole blood during titration with protamine. Frozen-thawed washed platelet suspension, or a chromatography fraction thereof, or autologous frozen-thawed platelet-rich plasma was added in various dilutions to freshly drawn blood anticoagulated with 3,000 USP units/1 heparin. After a 10 min incubation, the amount of protamine needed to restore the ACT to baseline ("protamine titration dose") was determined. We found that the protamine titration dose decreased in proportion to the amount of lysed platelet material added; expressed as a percentage of the total number of platelets present, each unit increase in lysed platelets produced a 1.7% ±0.8 (SD) reduction in the protamine dose needed to normalize the ACT. A heparin activity assay showed that this effect was not due to antiheparin activity of lysed platelets such as platelet factor 4 (PF4). Our data indicate that the procoagulant activity of platelet membranes reduced the sensitivity of the ACT to heparin. These findings suggest that membranous platelet microparticles may cause an inaccurate calculation, based on the ACT, of a protamine dose to reverse heparin anticoagulation in cardiopulmonary bypass procedures.

Effect of Temperature, Velocity Gradient and I.V. Heparin on in Vitro Blood Coagulation and Platelet Aggregation

1967 ◽  
Vol 17 (01/02) ◽  
pp. 112-119 ◽  
Author(s):  
L Dintenfass ◽  
M. C Rozenberg
Keyword(s):  
Blood Coagulation ◽  
Velocity Gradient ◽  
Elevated Temperatures ◽  
Morphological Changes ◽  
Effect Of Temperature ◽  
Clotting Time ◽  
Progressive Change ◽  
Aggregation Of Platelets ◽  
Microscopic Techniques

SummaryA study of blood coagulation was carried out by observing changes in the blood viscosity of blood coagulating in the cone-in-cone viscometer. The clots were investigated by microscopic techniques.Immediately after blood is obtained by venepuncture, viscosity of blood remains constant for a certain “latent” period. The duration of this period depends not only on the intrinsic properties of the blood sample, but also on temperature and rate of shear used during blood storage. An increase of temperature decreases the clotting time ; also, an increase in the rate of shear decreases the clotting time.It is confirmed that morphological changes take place in blood coagula as a function of the velocity gradient at which such coagulation takes place. There is a progressive change from the red clot to white thrombus as the rates of shear increase. Aggregation of platelets increases as the rate of shear increases.This pattern is maintained with changes of temperature, although aggregation of platelets appears to be increased at elevated temperatures.Intravenously added heparin affects the clotting time and the aggregation of platelets in in vitro coagulation.

The Flowing Clotting Time (Thrombus Formation Time) a Sensitive Test of Hypercoagulability

1969 ◽  
Vol 21 (03) ◽  
pp. 516-523
Author(s):  
H Engelberg ◽  
L. P Engelberg
Keyword(s):  
Thrombus Formation ◽  
Formation Time ◽  
Sensitive Test ◽  
Clotting Time ◽  
Reliable Test ◽  
Time Test ◽  
Plasma Heparin

SummaryThe addition of small amounts of extrinsic thromboplastin or of thrombin to blood in vitro accelerated coagulation more frequently and to a greater extent when determined by the flowing time test than when measured by the silicone clotting time, or by the blood or plasma heparin tolerance tests. Similar results were obtained when intrinsic thromboplastin formation was stimulated by contact with glass. However there was little or no acceleration of the flowing clotting time of plasma obtained from aliquots of the thromboplastin-containing blood. These results indicate that the flowing clotting time (thrombus formation time) of whole blcod is a more reliable test of hypercoagulability than previously described blood or plasma clotting time tests.

Fibrin Polymerization Defect in HIV-infected Patients-Evidence for a Critical Role of Albumin in the Prolongation of Thrombin and Reptilase Clotting Times

1995 ◽  
Vol 73 (03) ◽  
pp. 349-355 ◽  
Author(s):  
Pierre Toulon ◽  
Elyane Frere ◽  
Claude Bachmeyer ◽  
Nathalie Candia ◽  
Philippe Blanche ◽  
...  
Keyword(s):  
Critical Role ◽  
Human Albumin ◽  
Albumin Level ◽  
Final Concentration ◽  
Albumin Concentration ◽  
Clotting Time ◽  
Fibrin Polymerization ◽  
Small Series ◽  
Group 1

SummaryThrombin clotting time (TCT) and reptilase clotting time (RCT) were found significantly prolonged in a series of 72 HIV-infected patients drawn for routine coagulation testing. Both TCT and RCT were highly significantly correlated with albumin (r = -0.64, and r = -0.73 respectively, p<0.0001). TCT and RCT were significantly higher (p<0.0001) in a series of 30 other HIV-infected patients selected on their albumin level below 30.0 g/l (group l) than in 30 HIV-infected patients with albumin level above 40.0 g/l or in 30 HIV-negative controls; the two latter groups were not different. In vitro supplementation of plasma from group 1 patients with purified human albumin up to 45.0 g/l (final concentration) lead to a dramatic shortening effect on both TCT and RCT, which reached normal values. The TCT and RCT of the purified fibrinogen solutions (2.0 g/l final concentration) were not different in the three groups, and normal polymerization curves were obtained in all cases. This further ruled out the presence of any dysfibrinogenemia in the plasma from group 1 patients. Using purified proteins, highly significant correlations were demonstrated between the albumin concentration and the prolongations of both TCT and RCT, which were of the same magnitude order than those found in the patients plasma. These results suggest that hypo-albuminemia is responsible for the acquired fibrin polymerization defect reported in HIV-infected patients. The pathophysiological implication of the low albumin levels was suggested by the finding of decreased albumin levels (associated with prolonged TCT and RCT) in a small series of the eight HIV-infected patients who developed thrombotic complications.

Monitoring of r-Hirudin Anticoagulation during Cardiopulmonary Bypass – Assessment of the Whole Blood Ecarin Clotting Time

1997 ◽  
Vol 77 (05) ◽  
pp. 0920-0925 ◽  
Author(s):  
Bernd Pötzsch ◽  
Katharina Madlener ◽  
Christoph Seelig ◽  
Christian F Riess ◽  
Andreas Greinacher ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Whole Blood ◽  
Heart Surgery ◽  
Ex Vivo ◽  
Open Heart Surgery ◽  
Clotting Time ◽  
Blood Samples ◽  
Alternative Approach ◽  
Ecarin Clotting Time

SummaryThe use of recombinant ® hirudin as an anticoagulant in performing extracorporeal circulation systems including cardiopulmonary bypass (CPB) devices requires a specific and easy to handle monitoring system. The usefulness of the celite-induced activated clotting time (ACT) and the activated partial thromboplastin time (APTT) for r-hirudin monitoring has been tested on ex vivo blood samples obtained from eight patients treated with r-hirudin during open heart surgery. The very poor relationship between the prolongation of the ACT and APTT values and the concentration of r-hirudin as measured using a chromogenic factor Ila assay indicates that both assays are not suitable to monitor r-hirudin anticoagulation. As an alternative approach a whole blood clotting assay based on the prothrombin-activating snake venom ecarin has been tested. In vitro experiments using r-hirudin- spiked whole blood samples showed a linear relationship between the concentration of hirudin added and the prolongation of the clotting times up to a concentration of r-hirudin of 4.0 µg/ml. Interassay coefficients (CV) of variation between 2.1% and 5.4% demonstrate the accuracy of the ecarin clotting time (ECT) assay. Differences in the interindividual responsiveness to r-hirudin were analyzed on r-hirudin- spiked blood samples obtained from 50 healthy blood donors. CV- values between 1.8% and 6% measured at r-hirudin concentrations between 0.5 and 4 µg/ml indicate remarkably slight differences in r-hirudin responsiveness. ECT assay results of the ex vivo blood samples linearily correlate (r = 0.79) to the concentration of r-hirudin. Moreover, assay results were not influenced by treatment with aprotinin or heparin. These findings together with the short measuring time with less than 120 seconds warrant the whole blood ECT to be a suitable assay for monitoring of r-hirudin anticoagulation in cardiac surgery.

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