A new low molecular weight heparinoid Org 10172 as anticoagulant in hemodialysis

A low molecular weight heparinoid (Org 10172) was compared with unfractionated heparin in 36 patients on chronic hemodialysis in an open randomized cross-over study with three anti-coagulant treatment regimens for a single hemodialysis session. The anti-coagulant regimens were: a) standard heparin (3250-4750 I.U. heparin at start of hemodialysis followed by continuous infusion of 2000-2700 I.U. per hour); b) Org 10172 administered as a single intravenous bolus of 2400 anti-Xa units at start of dialysis; c) Org 10172 administered as a single bolus of 3200 anti-Xa units at start of dialysis. Plasma anti-Xa activity during hemodialysis was highest in regimen; d) and significantly lower when heparin was used. Mean beta-thromboglobulin concentrations changed to the same extent in the three groups. Plasma platelet factor 4 concentrations were higher after the use of heparin. The extracorporeal circuit was maintained patent in all groups; the volume of blood retained in the dialyzers did not differ markedly. Org 10172 proved safe and its anticoagulant effect was sufficient at the dose levels studied.     

Passage of commercial heparin and a low molecular weight fragment of heparin, CY 222, across the placenta of pregnant rabbits

Because of a further clinical use of low-molecular weight heparin fraction in prevention or treatment of venous thrombo-embolism, it was necessary to establish whether they cross the placenta. The studies were performed in pregnant rabbits. High doses of commercial unfractionated heparin (1 000 and 1 600 anti-Xa units per kg of body-weight) and high doses of a low molecular weight heparin fraction (1 000; 8 000 and 16 000 anti-Xa units per kg of body weight) were injected to animals at the end of gestation (term: 30 days). The placenta crossing was studied by drawing blood samples from the mother and foetus for assays of heparin blood level. There is no detectable levels of heparin in the foetus at any time after injection of commercial heparin at the dose of 1 000 anti-Xa units per kg; meanwhile heparin blood level is very low at the dose of 16 000 anti-Xa units/kg. The low molecular weight heparin fraction do not cross the placenta at the dose of 1 000 anti-Xa units/kg. However for higher doses (8 000 and 16 000 anti-Xa/kg) this heparin fraction gives a foetal heparin blood level upper than the one given by commercial heparin.     

Kinetics of anti-Xa activity during combined defibrotide-heparin administration in hemodialysis

Defibrotide, a polydesoxyribonucleotide derivative with antithrombotic and fibrinolytic activity, capable of inducing the release of PGI2 from vascular endothelia, was proposed as an alternative to standard heparin coverage during blood dialysis for patients at risk of bleeding. The original procedure featured the preliminary washing of the dialysis circuit with heparin, which was then recirculated and eliminated, and the two drugs, heparin and defibrotide, are known to interact with each other. The purpose of this present study was to explore the ex-vivo heparin activity (assessed as anti-Xa activity) in diverse hemodialysis models using defibrotide (800 mg intravenous, in 4 bolus injections) and various dosages of heparin. Anti-Xa activity is negligible in dialysis conducted with defibrotide alone. When the circuit was prewashed with heparin (5000 and 2500 IU), there was evident anti-Xa activity (0.3-0.5 U/ml) in the first 30-60 minutes of dialysis; continuous heparin infusion (500 U/hour) resulted in high anti-Xa activity levels at the end of dialysis. Thus the best hemodialysis procedure for patients at high risk of bleeding should be one utilizing only defibrotide, or defibrotide plus small amounts of calcium heparin infused at the rate of 500 U/hour for not more than two hours.     

The in vitro bleeding time while using a stable prostacyclin analogue during hemodialysis

A serious disadvantage of preventing clot formation by using prostacyclin (PGI2) to inhibit thrombocyte function during dialysis is that there exists no rapidly measurable monitoring parameter. The "in vitro bleeding time" (in vitro BT) is a new method for measuring primary hemostasis in vitro. Five chronic dialysis patients each underwent two dialyses: 1) with conventional full heparinization, and 2) with the stable PGI2 analogue CG 4203 and additional "low-dose" heparin. The predialytic in vitro BT is longer than normal values and values 1 h after the end of dialysis. While heparin has no significant effect on the in vitro BT, CG 4203 prolongs it concentration-dependently. Infusing CG 4203 at a rate of 25 ng/kg/min, the in vitro BT is extended beyond the measurable range of 800 microliter during the first approx. 150 min of dialysis. During the next approx. 90 min it steadily decreases.     

Subcutaneous low molecular weight heparin for management of anticoagulation in infants on excor ventricular assist device

Anticoagulation in infants and children on a ventricular assist device presents particular challenges. Unfractionated heparin has poor bioavailability; it can be difficult to achieve a stable anticoagulant effect; and, in the long-term, there is a risk of osteopenia. Long-term warfarin can be difficult to manage in infants on formula milk with vitamin K supplementation. We review our recent experience with subcutaneous low molecular weight heparin. Two patients received a left ventricular assist device (Excor, Berlin Heart AG) as a bridge to transplantation. Initial anticoagulation consisted of unfractionated heparin infusion beginning 6 hours after implantation to maintain an activated partial thromboplastin time of 70 seconds, checked every 4 to 6 hours. Platelet count (aim >80,000/microl) and thromboelastography were assessed daily. Antithrombin required substitution to maintain levels >70 IU/dl. To optimize anticoagulation, both infants were switched to subcutaneous low molecular weight heparin twice daily aiming for an anti-Xa activity between 0.5 and 1.0 IU/ml. Aspirin was added on day 4, checking platelet aggregation every 2 to 4 days, aiming at arachidonic acid stimulated aggregation 10% to 30% of baseline, collagen 100% of baseline. Dipyridamole was added once stability was reached if platelets count exceeded 150,000/microl. There were no clinical thromboembolic or bleeding events. Both patients had successful transplantation.     

Effect of unfractionated heparin and a low molecular weight heparin fragment on the DNA synthesis of human thymocytes

The effect of unfractionated heparin and a low molecular weight heparin fragment was tested on the DNA synthesis of human thymocytes cultured for 5 and 48 h. At 5 h, in the absence of serum, there was a stimulation with the highest concentration of unfractionated heparin, 11.1 mg/ml. At 48 h, there was an inhibition with the highest concentration of both the unfractionated heparin and the heparin fragment. In the presence of serum unfractionated heparin in the highest concentration gave an inhibitory effect at 48 h. With 0.01-1.0 mg/ml of unfractionated heparin, a stimulating effect was obtained instead.     

Prospective randomized clinical study in general surgery comparing a new low molecular weight heparin with unfractionated heparin in the prevention of thrombosis

A prospective, randomized, controlled clinical trial was performed comparing the antithrombotic efficacy of the low molecular weight heparin LMWH 21–23, (Braun) with an unfractionated heparin in elective general surgical patients over an observation period of 7 postoperative days. A total of 230 patients were admitted: 103 (group I) received low molecular weight heparin and 100 (group II) low-dose unfractionated heparin treatment given subcutaneously. In group I 41 patients (46%) were operated on for malignant disease and in group II 54 patients (54%). Due to the large amount of great abdominal procedures the intra- and perioperative application of hydroxyethyl starch was allowed for volume substitution. None of the patients died due to fatal pulmonary embolism. In group I four patients revealed positive ¹²⁵I-labeled fibrinogen uptake (3.9%); two patients belonged to the hydroxyethyl starch subgroup. In group II five patients displayed a positive fibrinogen uptake (5%); two belonged to the hydroxyethyl starch subgroup. The results of the hemostaseological investigations (e.g., prothrombin time, activated partial thromboplastin time, thrombin clotting time, fibrinogen, antithrombin III, protein C, plasminogen, ₂-antiplasmin , tissue-type plasminogen activator, plasminogen activator inhibitor) revealed no statistically significant differences between groups I and II or their subgroups, although a tendency to prolonged clotting times was observed. The antifactor Xa activity values, however, displayed a statistically significant difference between the two groups (P < 0.05). The antifactor Xa activity measured up to 0.16 U/ml for the low molecular weight heparin (group I) and 0.05 U/ml for the unfractionated heparin (group II) in the postoperative period. Major bleeding complications were not encountered in this study. Fundamental for the low incidence of thrombosis, the additive administration of hydroxyethyl starch appeared in almost one-third of the patients in both study groups.Abbreviations APTT activated partial thromboplastin time - aXa anti-factor Xa - DVT deep venous thrombosis - FUT ¹²⁵I-labeled fibrinogen uptake test - HES hydroxyethyl starch - LMWH low molecular weight heparin - PE pulmonary embolism - UFH unfractioned heparin     

Comparison of hemostasis with two high-flux hemocompatible dialysis membranes

Eight adults with chronic renal failure were dialyzed using polyacrylonitrile (AN 69) or polysulfone (PS) membranes with a high (HHR) or low (LHR) continuous non-fractionated heparin regimen--a total of either 90 or 50 IU/kg body weight. With the HHR, for a mean anti-Xa (aXa) activity of around 0.40 IU/ml, no plasma activation of coagulation was observed; fibrinopeptide A (FPA) was in agreement with the residual blood volume (RBV) and the state of the bubble trap, especially with the PS membrane. With the LHR, for a mean aXa below 0.21 IU/ml, there was only moderate activation of coagulation. The PS membrane gave different results from the AN 69 membrane, RBV values on the HHR and aXa being lower on both the HHR and LHR, with FPA values being regularly lower on the LHR. The decrease in plasma beta-TG on the LHR was more marked with the PS than with the AN 69 membrane due to loss on dialysis or adsorption, as shown by the arterio-venous difference. The increase in plasma PF4 was related to the effect of heparin. However, there was no platelet activation. On the LHR, platelet count and intraplatelet beta-TG and PF4 levels remained very stable. The two high-flux membranes were very hemocompatible and require only low doses of heparin, but the dialyzer with AN 69 membrane need its geometry improving.     

A comparison of the sensitivity of APTT reagents to the effects of enoxaparin, a low-molecular weight heparin

Low-molecular weight heparin (LMWH) is the product of enzymatic or chemical degradation of unfractionated heparin (UFH). It has been found to have better bio-availibility, more predictable dose response and can be used as an alternative to UFH for prophylaxis and treatment of thrombotic disorders. It is claimed that no laboratory monitoring is necessary for LMWH therapy; however, for the aged, renal impaired, obese or grossly underweight, monitoring of dose effect with anti-Xa assay is recommended. The activated partial thromboplastin time (APTT), which is the test of choice for UFH monitoring, is believed to be insensitive to the effect of LMWH. The sensitivity of the APTT to heparin lies in the APTT reagent used. In this study, eight different APTT reagents were used to compare the APTT with anti-Xa activity in ex vivo plasma from patients who were on enoxaparin (LMWH, Clexane) therapy. It was found that, as with UFH, APTT reagents show variable sensitivity to LMWH. The APTTs from all eight reagents were found to have a linear relationship to anti-Xa activity. The APTT results using three of the reagents gave an indication of the use of LMWH therapy. It was also found that patients who were lupus anticoagulant (LA)-positive had much more prolonged APTTs when on LMWH therapy; however, a linear correlation between APTT and anti-Xa was not present in these patients.     

Toxicity of plasma from hemodialysis patients treated with heparin or prostacyclin

Hemodialysis was performed in 6 uremic patients with either a bolus dose of 5 000 IU heparin or prostacyclin at a constant infusion rate of 5 ng/kg/min. Clinical data, plasma triglycerides (TG), free fatty acids (FFA), platelet aggregation, white blood cell count and plasma toxicity were measured prior to and during both procedures. No serious side-effects were recorded. Heparin induced a fall in plasma TG, a rise in FFA and increased plasma toxicity. Prostacyclin infusion had no effect on these parameters. During both tests a marked drop in white blood cell count was found 15 min after the start of hemodialysis. During heparin dialysis no clotting was observed in the extracorporeal circuit. During prostacyclin dialysis clotting was observed at the venous line in three cases.     

急性心肌梗死患者溶栓后不同肝素抗凝疗效分析

目的比较急性心肌梗死rt-PA溶栓治疗后普通肝素（UFH）和国产低分子肝素（商品名：海普宁Hiparin）不同抗凝辅助治疗方法的疗效和安全性。方法74名入院接受rt-PA溶栓治疗的ST段抬高型急性心肌梗死患者，随机分为常规UFH组和Hiparin组。UFH组溶栓治疗后每小时静脉滴注UFH 700～1000 U，持续滴注48h，维持活化的部分凝血活酶时间为正常对照的1．5～2．0倍，以后皮下注射UFH 7500 U，每12h一次，持续一周。Hiparin组予rt-PA溶栓后4h皮下注射Hiparin 5000 U，每12h一次，持续一周。终点事件：观察住院期间及随访期间（出院后2月内）心绞痛、心肌再梗死及心源性死亡事件。副作用观察指标：观察住院期间脑血管事件，出血事件发生情况。随访时间为60d。结果联合终点事件在Hiparin组明显下降（17．1％vs38．2％，P〈0．05），出血事件发生率低于UFH组（5．7％vs26．5％，P〈0．05）。结论急性心肌梗死rt-PA溶栓后辅助抗凝治疗Hiparin组观察时间内较UFH组更能减少心脏事件的再发生及出血事件。     

Modulating effects of heparin preparations on the DNA synthesis response of human peripheral blood T lymphocytes activated by mercuric chloride and nickel sulfate

The effect of unfractionated heparin and a low molecular weight heparin fragment was tested on the DNA synthesis response of human peripheral blood T lymphocytes from nickel-allergic patients, activated by mercuric chloride and nickel sulfate. An inhibition was found with unfractionated heparin at a concentration of 1.1 mg/ml, when added at 1 h after mercuric chloride and nickel sulfate and with the same concentration of the heparin fragment, when added at 1 h after nickel sulfate, no effect was seen after addition at 72 h after the salts. Both heparin preparations in concentrations of 0.0001-0.11 mg/ml stimulated the response to nickel sulfate and in concentrations of 0.001-0.11 mg/ml stimulated the response to mercuric chloride. Thus the heparin preparations seem to have different modulating effects on both nickel and mercury activation of lymphocytes dependent on both heparin concentration and the point of time when it was added in the course of the activation process.     

Evaluation of heparin assay for coagulation management in newborns undergoing ECMO

The objective was to identify the usefulness of heparin level by anti-factor Xa (anti-Xa) assay vs activated partial thromboplastin time (PTT) or activated clotting time (ACT) in neonates undergoing extracorporeal membrane oxygenation (ECMO). A retrospective record review of 21 patients in the neonatal intensive care unit (mean ECMO initiation age, 2 days; range, 0-4 days; male/female ratio, 1:1) undergoing ECMO from 2006 to 2008 was performed. Linear regression correlations between anti-Xa, PTT, and ACT were determined by extrapolating PTT and ACT therapeutic ranges that corresponded with the ECMO heparin target range of 0.3 to 0.6 U/mL. Pearson correlation coefficients between heparin levels and PTT (-0.903 to 0.984), PTT less than 40 seconds after correction using PTT-heparinase (-0.903 to 1.000), and ACT (-0.951 to 0.891) in this patient population were widely variable. Inconsistency of PTT and ACT therapeutic ranges corresponding to heparin levels of 0.3 to 0.6 U/mL prompts a multifactorial approach to ECMO management because no single laboratory test can be used to determine appropriate anticoagulation management.     

Stimulating effect of unfractionated heparin and a low molecular weight heparin fragment on the DNA synthesis response of human thymocytes to mercuric chloride

The effect of unfractionated heparin and a low molecular weight heparin fragment was tested on the DNA synthesis response of human thymocytes to mercuric chloride. In a concentration of 0.01-0.11 mg/ml, unfractionated heparin somewhat stimulated this response, while the heparin fragment at 11.1 mg/ml gave an evident stimulation of the response and a lower stimulation degree at 1.1 mg/ml.     

Heparin bonding of the extracorporeal circuit reduces thrombosis during prolonged lung assist in goats

This study investigated whether an artificial membrane lung of nonmicroporous polyolefin hollow fibers bonded with heparin could prolong venoarterial extracorporeal lung assist (ECLA) with low dose systemic heparin in goats. We compared heparin bonded circuits (Carmeda Bioactive Surface, "HB" group, n = 5) with non heparin bonded circuits ("NHB" group, n = 5) in venoarterial ECLA (V-A ECLA) for 7 days. Activated coagulation time (ACT) was maintained at approximately 130 sec by systemic infusion of small doses of heparin in the HB group, and at 200-230 sec in the NHB group. Thrombus formation was assessed by visual examination of the circuit, and possible cerebral embolization of thrombi was observed from behavioral abnormalities of the animals. The mean heparin dose given during ECLA was 20.4 +/- 3.6 U/kg per hr in HB, and 50.9 +/- 14.2 U/kg per hr in NHB, significantly less in HB than NHB (p < 0.01). Blood gas changes across the oxygenator, bypass flow rate, platelet aggregation activity, platelet counts, fibrin monomer (FM) test, and antithrombin-III (AT-III) activity did not differ between the two groups. In HB, thrombi were fewer and no abnormal neurologic symptoms were observed during ECLA. Numerous thrombi were observed in all oxygenators with NHB. One NHB goat developed convulsions and cerebral hemorrhage on the 6th day of ECLA. Nonmicroporous polyolefin hollow fibers can be bonded with heparin. An artificial membrane lung constructed of these fibers showed good anticoagulation by decreased thrombus formation with a small dose of infused heparin.     

An international survey of current practice in the laboratory assessment of anticoagulant therapy with heparin

AIMS: We conducted a survey of laboratory practice for assessment of heparin anticoagulant therapy by participants of the Royal College of Pathologists of Australasia Quality Assurance Program (RCPA QAP). METHODS: A questionnaire was sent to 646 laboratories enrolled in the Haematology component of the QAP, requesting details of tests used for monitoring heparin therapy. RESULTS: Seventy laboratories (10.8%) returned results that indicated that they performed laboratory monitoring of heparin therapy. Most laboratories (69/70 = 98.6%) use the activated partial thromboplastin time (APTT) to monitor unfractionated heparin, with eight (11.4%) also using the APTT for monitoring low molecular weight (LMW) heparin. Five (7.1%) laboratories use the thrombin time (TT) test to help monitor heparin therapy and 37 (52.9%) laboratories use an anti-Xa assay to monitor heparin (either LMW or unfractionated). Normal reference ranges (NRR) for APTT differed considerably between laboratories, even those using the same reagent. Therapeutic ranges (TR) also differed considerably between laboratories, for both APTT and the anti-Xa assay. Laboratory differences in NRR and TR using the same reagents could only be partly explained by the use of different instrumentation. CONCLUSIONS: There is a large variation in current laboratory practice relating to monitoring of heparin anticoagulant therapy. This finding is similar to that of a similar survey conducted by the RCPA QAP almost a decade ago. This study suggests that better standardisation is still required for laboratory monitoring of heparin therapy.     

Selective antimetastatic effect of heparins in preclinical human melanoma models is based on inhibition of migration and microvascular arrest

Use of heparin derivatives in several cancer types revealed that anticoagulant therapies have a beneficiary side effect: delay of tumor progression. Since there are no data on human melanoma, we have analyzed the effect of heparins in preclinical models. Neither unfractionated heparin (UFH), nor its low molecular weight derivative (LMWH) influenced in vitro or in vivo growth of HT168-M1 human melanoma cells. However, heparins significantly inhibited lung colony formation and liver metastasis development in the concentration range of 20–200 IU/kg, whereas recombinant hirudin was ineffective. The antimetastatic effect was due to an early (5–60 min) inhibition of tumor cell arrest in the lung microvasculature. Analysis of the molecular mechanism of the antimetastatic effect of heparins indicated a specific inhibition of tumor cell migration and matrix invasion. The presented experimental data suggest that heparins have specific antimetastatic effect in the case of human melanoma, which is independent from the coagulation cascade.     

Monitoring of heparin therapy and establishment of an optimal therapy scheme for thrombosis prophylaxis in a pig model for human catheter interventions

This study aims to investigate variables suitable for monitoring of unfractionated heparin (UFH) therapy and establishment of an optimal therapy scheme in pigs. This is a prospective study of 32 pigs undergoing catheterization for endovascular embolization of experimentally induced arteriovenous malformation. Pigs were assigned to four groups receiving different UFH treatment during catheter intervention. In groups?1 and 2, UFH was applied as a bolus of either 100?IU/kg (n?=?6) and 200?IU/kg (n?=?6). Groups?3 and 4 received a continuous infusion of 66?IU/kg/h?UFH (n?=?10) and 100?IU/kg/h (n?=?10), respectively, which was applied 20?min after an initial bolus of 100?IU/kg. Blood samples were taken 0, 10, 20, 40, 60, 100, and 140?min after starting catheterization (groups?1?+?2) and after 0, 10, 20, 30, 40, 50, 60, 80, 100, 120, and 140?min, respectively (groups 3?+?4). High/low range activated coagulation time (LR-ACT), activated partial thromboplastin time (aPTT), prothrombin time, fibrinogen, and anti-FactorXa activity (FXa) activity were assessed. Based on anti-FXa activity, bolus injection of 100 and 200?IU/kg UFH had a mean half-life of 28.43?±?8.85 and 57.05?±?12.42?min, however, an aPTT exceeding 999?s was present in four of seven pigs in group?2. In group?3, aPTT increased from baseline 15?±?2?s to a steady state ranging from 30 to 33?s. In group?4, there was an increase of aPTT to 58?±?23?s 140?min after initiation of treatment. Suitable variables for monitoring UFH therapy included anti-FXa activity, aPTT, and LR-ACT. An initial bolus of 100?IU/kg?followed by a continuous UFH infusion of 66?IU?UFH/kg/h can be recommended as antithrombotic therapy during catheterization.     

Frequency of anti-heparin-PF4 complex antibodies (HIT antibodies) in uremic patients on chronic intermittent hemodialysis

The aim of this study was to determine the frequency of heparin/platelet factor (PF) 4 complex antibodies in 305 uremic patients treated with chronic intermittent hemodialysis using unfractionated heparin or low-molecular-weight heparin for 3 months. Heparin-induced thrombocytopenia (HIT) antibodies were detected by ELISA in 7 patients (2.3%) who had no history of HIT. Two patients abruptly developed HIT associated with the formation of clots in the extracorporeal circuit after they were found to be carrying HIT antibodies. These patients were suspected to have a similar trigger: an increased dose of recombinant human erythropoietin (rHuEPO). The drug might induce parallel changes in hematocrit (Ht) levels and platelet counts until the onset of HIT. After the onset of HIT, a parallel phenomenon between Ht and platelet counts was not found because of the thrombocytopenia due to HIT. Although HIT onset has been reported during the initial phase of dialysis sessions, there have been few reports on the onset of HIT in uremic patients on dialysis with long-term heparin anticoagulation. In this study, HIT was observed in 2 uremic patients on chronic dialysis with intermittent use of heparin. In some patients on chronic intermittent dialysis carrying HIT antibodies, HIT may occur following rHuEPO treatment. The presence of HIT should be borne in mind in chronic dialysis patients carrying HIT antibodies for 3 months or more.     

Assessing heparin dosing in neonates on venoarterial extracorporeal membrane oxygenation

We studied 12 consecutive neonates placed on venoarterial extracorporeal membrane oxygenation (ECMO) in 2004-2005. Activated clotting times (ACT) and anti-factor Xa levels were measured, and the corresponding heparin drip rate was noted. The mean heparin drip rate was 42.2 +/- 10.9 (SD) U/kg/hour (range 20.0-69.5 U/kg/hour). There were 55 simultaneous ACT and anti-factor Xa samples drawn. The mean ACT was 167 +/- 20 seconds (range 128-227 seconds). There was no correlation between ACT levels and heparin dose (r = 0.21; p = 0.12). The mean anti-factor Xa activities were 0.73 +/- 0.19 U/ml (range 0.1-1.0 U/ml). There was a correlation (r = 0.75; p < 0.0001) between anti-factor Xa and heparin dose. We also examined the effect of day on ECMO on heparin drip rate, ACT, and anti-factor Xa. There was no correlation between day on ECMO and either heparin drip rate (r = 0.21, p = 0.12) or ACT (r = 0.002, p = 0.99). However, there was a positive correlation (r = 0.46, p < 0.0005) between day on ECMO and anti-factor Xa activities. In these neonatal patients on venoarterial ECMO, ACT was not a reliable indicator of heparin effect. Furthermore, the increase in anti-factor Xa levels with time on ECMO suggests that heparin accumulates and/or that anti-thrombin III levels decrease with time on ECMO.