Comparison of Bivalirudin Versus Unfractionated Heparin for Anticoagulation in Adult Patients on Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) contributes to coagulopathy, necessitating systemic anticoagulation to prevent thrombosis. Traditionally, unfractionated heparin (UFH) has been the anticoagulant of choice, however, due to many inadequacies new evidence suggests benefit with the use of direct thrombin inhibitors. This retrospective cohort sought to evaluate the safety and efficacy of bivalirudin compared to UFH in ECMO patients. Primary endpoints included incidence of bleeding and thrombosis. Percent time in therapeutic range (TR), time to achieve TR and number of dose titrations required to maintain TR were calculated to assess efficacy of institutional protocols. Overall incidence of thrombosis was low, with one event in the bivalirudin group and no events in the UFH group. No difference was found in rates of bleeding between groups (6% vs . 10%, P = 0.44). Bivalirudin yielded higher percent time in TR (86% vs. 33%, P < 0.001), faster time to TR (2 vs . 18 hr, P < 0.001) and required fewer dose adjustments to maintain TR (2 vs . 11, P < 0.001) compared to UFH. These results suggest bivalirudin and UFH are associated with similar rates of bleeding and thrombosis in patients requiring ECMO support. Our results demonstrate the favorable pharmacokinetic profile of bivalirudin, and its ability to consistently maintain TR when compared to UFH.

Artificial intelligence based identification of the functional role of hirudin in diabetic erectile dysfunction treatment

Diabetic erectile dysfunction (DED) hugely affected the patients' sexual life quality. However, there are no satisfactory therapeutic methods and intervention targets for this subtype of erectile dysfunction (ED). Inspired by the clinical practice of traditional Chinese medicine (TCM), we found that hirudin, the main active ingredient in the leech, could ameliorate the ED symptoms of the DED mouse model. To further reveal the underlying mechanism of hirudin, we designed a novel strategy to discover potential targets based on the diagnostic system of TCM, and found that myeloperoxidase (MPO) was a promising target of hirudin. Hirudin directly interacts with MPO and inhibits its activity, thus further decreases the content of oxidized low-density lipoprotein (ox-LDL) in serum. Our results demonstrated that the hirudin could ameliorate the symptoms of DED, and revealed the underlying mechanism of hirudin in regulating the activity of MPO.

Effect of hirudin on serum matrix metalloproteinase-9 of acute cerebral infarction: A protocol of systematic review and meta-analysis

BACKGROUND

This study aims to check the effect of hirudin on serum matrix metalloproteinase-9 (SMMP9) in patients with acute cerebral infarction (ACI).

METHODS

For acquisition of obtained data of included studies, we will undertake comprehensive search from the following electronic databases: MEDLINE, Embase, Cochrane Library, CINAHL, WANGFANG database, VIP database, CBM database, and China National Knowledge Infrastructure from their inceptions to the March 31, 2020. No restrictions of language and publication status will be applied to all database sources. Two investigators will independently undertake study selection, data extraction, and study quality. Any different opinions between 2 investigators will be solved by a third investigator through consultation. Study quality will be assessed using Cochrane risk of bias tool, and level of evidence for outcome results will be identified using the Grading of Recommendations Assessment, Development, and Evaluation method. We will use RevMan 5.3 software for statistical analysis.

RESULTS

From this study, we will evaluate the effect of hirudin on SMMP9 in patients with ACI.

CONCLUSION

The findings of this study will provide evidence to ensure the effect of hirudin on SMMP9 in patients with ACI.

[Effect of natural hirudin on revascularization of ischemic skin flaps in rats by Micro-CT]

OBJECTIVE

To investigate the effect of natural hirudin on revascularization of ischemic skin flap in rats using Micro-CT and three-dimensional (3D) reconstruction.

METHODS

Thirty-two Sprague Dawley rats were prepared a ischemic skin flap (8.0 cm×1.8 cm) model on the back and randomly divided into hirudin group and control group (16 rats in each group). At immediate and within 3 days after operation, the rats were treated with hypodermic injection of natural hirudin 0.3 mL (including natural hirudin 6 ATU) every day in hirudin group and the equal amount of normal saline in control group. At 6 days after operation, the survival rate of skin flap was evaluated, histological changes were observed by HE staining, and the volemia, length of blood vessels, and number of blood vessels were analyzed with Micro-CT 3D reconstruction.

RESULTS

Both groups of rats survived to the end of the experiment without infection. Different degrees of necrosis occurred in the distal part of the skin flaps in both groups at 6 days after operation, but the flap survival rate of the hirudin group (72.11%±8.97%) was significantly higher than that of control group (58.94%±4.02%) ( t=3.280, P=0.008). Histological observation showed that the histological hierarchy of the hirudin group was clearer than that of the control group, with more microangiogenesis and less inflammatory response and inflammatory cell infiltration. Micro-CT 3D reconstruction showed that the flap vessels in the hirudin group were more and denser, and the volemia, length of blood vessels, and number of blood vessels were significantly higher than those in the control group ( P<0.05).

CONCLUSION

Natural hirudin can reduce the inflammation of tissue, promote the regeneration and recanalization of blood vessels in ischemic skin flap, so as to improve the survival rate of the flap.

Heparin-induced Thrombocytopenia and the Use of r-Hirudin during Cardiopulmonary Bypass

We report the successful use of r-hirudin (lepirudin) for cardiopulmonary bypass in a 67-year-old man who developed heparin-induced thrombocytopenia type II during heparin treatment of an extensive deep venous thrombosis. Lepirudin was monitored by the modified ecarin clotting time in a “mobile laboratory” set up next to the cardiac theatre, aiming for lepirudin levels of 3.5 to 4.5 μg/ml during bypass.

[Lipid peroxidation and endogenous intoxication during hirudotherapy for gonarthrosis]

The time course of changes in lipid peroxidation and the characteristics of endogenous intoxication were studied in the treatment of patients with gonarthrosis. The findings suggest the positive changes in the biochemical parameters that characterize endogenous intoxication and recovery of the body's antioxidant status despite the activation of prooxidative processes.

Prevention of hyperacute xenograft rejection through direct thrombin inhibition with hirudin

BACKGROUND

Hyperacute xenograft rejection (HXR) is characterized by complement activation and intravascular thrombosis. The pathogenesis of HXR is attributed to antibodies binding to α-Gal-epitopes on the endothelial cells (EC) of the xenograft, activating complement and thrombin-mediated coagulation mechanisms. Our aim was to evaluate the influence of thrombin inhibition upon HXR and tissue integrity in an ex-vivo working heart model.

MATERIAL/METHODS

Eighteen isolated porcine hearts were perfused with human whole blood in a working heart model. The blood was treated with heparin (n=9) in group G-I and with heparin and additionally recombinant hirudin (0.012 mg/ml bolus, afterwards 4.5 µg/ml/h continuously) in group G-II (n=9). The experiments were terminated at end of cardiac output. Histological analysis was performed after the experiments.

RESULTS

Working heart time of G-II was significantly longer (712.0±37.8 vs. 125.0±31.4 min, p<0.01). Heart weight increase in G-II was lower (0.05±0.01 vs. 0.30±0.06%/min, p<0.01). Stroke work index and specific coronary flow improved significantly in G-II after 120 minutes. Histological analysis revealed increased tissue damage and thrombosis phenomena in G-I. Moreover, immunohistochemistry showed increased C3 and C5b-C9 upon EC of G-I.

CONCLUSIONS

Direct thrombin inhibition with Hirudin could be a successful strategy in primate xenotransplantation experiments to prevent tissue damage thus improving the graft survival.

Dabigatran: new drug. Continue to use heparin, a better-known option

(1) The standard anticoagulant for preventing thromboembolic events after hip or knee replacement surgery is a subcutaneous low-molecular-weight heparin such as enoxaparin; (2) Dabigatran, a specific thrombin inhibitor, was recently licensed for oral prophylaxis in this setting, as dabigatran etexilate (mesilate), a prodrug; (3) The clinical evaluation of dabigatran in this indication is based on two comparative double-blind trials with similar protocols, comparing dabigatran 150 mg or 220 mg/day versus enoxaparin in 3494 patients undergoing hip replacement surgery and 2101 patients undergoing knee replacement surgery. The results were virtually identical: compared with enoxaparin, dabigatran did not reduce overall mortality (almost zero in the different groups), the frequency of symptomatic pulmonary embolism (almost zero in the different groups), or the frequency of symptomatic deep venous thrombosis (0.1% to 1.2%); (4) There was no difference between the groups with respect to the frequency of severe bleeding (about 1.5%), hepatic disorders (about 4%), or acute coronary events (a few cases). But dabigatran was associated with surgical wound seepage in 7% of patients, versus 4.7% with enoxaparin; (5) The anticoagulant effect of dabigatran, and therefore the frequency of haemorrhage, increases with age and in cases of renal failure. However, clinical trials included relatively few elderly patients and/or patients with renal failure, who nonetheless represent a large proportion of the candidates for hip or knee replacement; (6) Dabigatran becomes more potent when combined with P-glycoprotein inhibitors or with drugs that impair renal function. Combination with other antithrombotic drugs should be avoided. (7) Dabigatran is administered orally, while enoxaparin requires daily subcutaneous injections. Dabigatran therapy does not necessitate laboratory monitoring, while the platelet count must be monitored with enoxaparin. There is no known antidote for dabigatran overdose; (8) In summary, for the prevention of venous thromboembolic events after orthopaedic surgery, it is better to continue to use heparins, at least pending more thorough evaluation of dabigatran.

Pathogenesis, diagnosis, and management of disseminated intravascular coagulation: a literature review

BACKGROUND

Disseminated Intravascular Coagulation (DIC) is an acquired syndrome characterized by systemic intravascular activation of coagulation, leading to deposition of fibrin in the circulation, occurring in the course of severe diseases.

OBJECTIVE

To review literature for articles that focus on the pathogenesis, diagnosis, and management of DIC.

INFORMATION SOURCES

Selected articles from the Index Medicus data base.

STATE OF THE ART

Recent studies have elucidate the pathogenic pathways that can trigger DIC. However, clinical and laboratory diagnosis of the syndrome remains difficult, as there is no single laboratory test, sensitive and specific enough, to allow a definitive diagnosis of DIC. Cornerstone for the treatment of DIC remains the optimal management of the underlying disorder. However, therapeutic interventions based on our present knowledge of the pathogenesis of DIC may be appropriate.

CONCLUSION

Recent research on DIC, resulted in the development of diagnostic algorithms for the diagnosis of the syndrome and better supportive therapeutic strategies.

Recombinant hirudin for cardiopulmonary bypass anticoagulation: a randomized, prospective, and heparin-controlled pilot study

BACKGROUND

Lepirudin, a recombinant hirudin, is a direct acting thrombin inhibitor that has been used as a heparin alternative in patients with heparin-induced thrombocytopenia requiring on-pump cardiac surgery. To evaluate the efficacy, safety, and clinical utility of lepirudin as a cardiopulmonary bypass (CPB) anticoagulant, we compared lepirudin with heparin in a routine CPB setting.

METHODS

Twenty patients were randomly assigned to receive lepirudin (0.25 mg/kg b. w. bolus and 0.2 mg/kg b. w. added to the CPB priming) or heparin (400 U/kg b. w. bolus) with protamine reversal. Lepirudin and heparin anticoagulation during CPB was monitored using the ecarin clotting time or ACT, respectively and additional lepirudin (5 mg) or heparin (5000 U) boluses were administered.

RESULTS

The CPB circuit was performed in both groups without thromboembolic complications. Median blood loss during the first 36 hours was statistically higher ( P = 0.007) in the lepirudin group (1.226 +/- 316 ml) compared to the heparin group (869 +/- 189 ml). One patient of the lepirudin group developed pulmonary embolism 24 hours after surgery. This patient was tested homozygous for the FV-Leiden mutation.

CONCLUSION

Lepirudin provides effective CPB anticoagulation but induces a higher postoperative blood loss than heparin. Lepirudin should be restricted to patients undergoing CPB who cannot be exposed to heparin.

Antithrombotic and anticoagulant effects of the direct thrombin inhibitor dabigatran, and its oral prodrug, dabigatran etexilate, in a rabbit model of venous thrombosis

BACKGROUND

Oral anticoagulant therapies targeted at thrombin are being developed to overcome limitations associated with current standard therapies.

OBJECTIVES

This study was undertaken to assess and compare the antithrombotic and anticoagulant effects of the novel, selective and reversible, direct thrombin inhibitor (DTI), dabigatran, and its oral prodrug dabigatran etexilate, to that of unfractionated heparin (UFH), hirudin and melagatran using a rabbit model of venous thrombosis.

METHODS

A rabbit model of venous thrombosis consisting of endothelial damage with blood flow reduction was used with minor modifications.

RESULTS

All compounds demonstrated a dose-dependent reduction in thrombus formation following i.v. administration with complete or almost complete inhibition at the highest doses. Dabigatran (in the dose range 0.03-0.5 mg kg(-1)) had a 50% effective dose of 0.066 mg kg(-1). By comparison, UFH (5-50 U kg(-1)), hirudin (0.01-0.05 mg kg(-1)) and melagatran (0.01-0.3 mg kg(-1)) had a 50% effective dose of 9.8 U kg(-1), 0.016 mg kg(-1) and 0.058 mg kg(-1), respectively. Similarly, oral dabigatran etexilate (1-20 mg kg(-1)) inhibited thrombus formation in a dose-dependent manner. Maximum inhibition was achieved within 1 h of administration, suggesting a rapid onset of action. For both routes of administration, inhibition of thrombus formation directly correlated with prolongation of the activated partial thromboplastin time.

CONCLUSIONS

These findings demonstrate the potent anticoagulant and antithrombotic activity of dabigatran as a selective thrombin inhibitor in a rabbit model of venous thrombosis. Notably, dose-dependent and long-lasting antithrombotic efficacy was observed after application of its oral form dabigatran etexilate, which is currently undergoing phase III clinical development.

Hirudin treatment for multiple thromboses in a preterm infant with inherited thrombophilia

Thromboembolic events in preterm infants constitute a serious problem in neonatal intensive care. In most cases, treatment with low-molecular-weight heparin offers a sufficient therapy of thrombotic events. We report the case of a severely sick male preterm infant with a heterozygous factor V Leiden mutation and protein C deficiency. The infant developed multiple thromboses despite adequate anticoagulation with enoxaparin and was in a life-threatening situation. Treatment with hirudin prevented the occurrence of new thromboses without causing bleeding complications. After 2 weeks hirudin was discontinued and low-molecular-weight heparin therapy was started again. A successive recanalization of the vast majority of affected vessels was observed within the following 6 months. Despite some minor neurologic sequelae and a slight delay in neuro-motor development, the 2.5-year-old boy is in a healthy condition. This case demonstrates that hirudin can be an effective alternative anticoagulant in neonates and infants refractory to heparin treatment. Efficacy and safety issues of hirudin treatment, however, need to be evaluated in randomized trials.

Hirudo medicinalis-Anwendungen in der plastischen und rekonstruktiven Mikrochirurgie - eine Literaturübersicht

Medical leech therapy has enjoyed a renaissance in the world of reconstructive microsurgery during recent years. Especially venous congestion is decreased using hirudo medicinalis application such as following replantation of amputated fingers or congested flaps. They provide a temporary relief to venous engorgement whilst venous drainage is re-established. Living in symbiosis with Aeromonas hydrophila, who can digest the sixfold blood meal related to their body weight, and a broad number of anticoagulant agents such as the thrombin inhibitor hirudin, apyrase as well as collagenase, hyaluronidase, Factor Xa inhibitor and fibrinase I and II, leeches decrease venous congestion. Laser Doppler flowmetry could demonstrate a significant increase in superficial skin perfusion following leech application 16 mm around the biting zone. Following the initial blood meal accounting for about 2.5 ml, the anticoagulant effect of the various leeches enzymes follows within the next 5-6 hours, which both account for the beneficial effects. Infection associated with leech therapy is a documented complication of leech application, with reported incidences ranging from 2.4 to 20 % and a chinolone antibiotic is currently recommended to face the potential Aeromonas hydrophila infection. Anemia is a second adverse effect during medicinal leech application which has to be taken account with repetitive blood samples. Besides the successful applications of leeches in various applications in plastic and reconstructive microsurgery, randomized-controlled trials are pending to elucidate the value of hirudo medicinalis according to evidence-based criteria above from case series and case studies.

Modified plasma-based ecarin clotting time assay for monitoring of recombinant hirudin during cardiac surgery

Recombinant hirudin (r-hirudin) is being used increasingly for therapeutic anticoagulation in patients with heparin-induced thrombocytopenia undergoing cardiovascular surgery. Although multiple laboratory methods are available for measuring r-hirudin, the ecarin clotting time (ECT) is the most commonly used for this purpose. Ecarin (extracted from snake venom) converts prothrombin to meizothrombin, which promotes clot formation. Direct thrombin inhibitors, like r-hirudin, bind meizothrombin and yield a linear, dose-dependent prolongation of ECT. Low levels of prothrombin and fibrinogen in plasma samples can lead to higher ECT; suggesting falsely elevated r-hirudin levels. A modified ECT assay with prothrombin and fibrinogen in excess was optimized using an orthogonal array method to eliminate the variations in patients' plasma prothrombin and/or fibrinogen levels for accurate determinations of plasma r-hirudin levels. By using the modified ECT assay, falsely elevated r-hirudin levels can be avoided in patients undergoing cardiopulmonary bypass, thus providing reliable and accurate r-hirudin monitoring in this clinical setting.

[Heparin-induced thrombocytopenia in hemodialysis. Case report and review of the literature]

Thrombocytopenia is a potential complication of heparin therapy. There are two forms of heparin-induced thrombocytopenia (HIT). Type-I HIT is characterized by a mild decrease in platelet count that occurs within the first 2-4 days after heparin initiation. The platelet count often returns to normal without stop heparin treatment. The mechanism of thrombocytopenia appears to be due to a direct effect of heparin on platelet activation. The second form (type-II) is an immune-mediated disorder characterized by severe thrombocytopenia, which may include both arterial and venous thrombosis. We present a case of type-II HIT occurred in a hemodialysis patient resulting in acute pulmonary embolism and peripheral venous thrombosis, and review the literature.

Inhibition of thrombin: relevance to anti-thrombosis strategy

Thromboembolism is a common cause of death and disability. Heparin or warfarin, the current standard management for thromboembolism may cause serious bleeding complications. Thrombin is the key enzyme of coagulation. Hirudin, the most potent natural thrombin-specific inhibitor, was first isolated from leech salivary fluid. Synthetic thrombin-specific inhibitors are rationally designed based on the knowledge on the structures of the activate site of thrombin. Thrombin-specific inhibitors are the current best choice for the treatment of heparin-induced thrombocytopenia (HIT). Recombinant hirudins (such as desirudin) were also approved for the prevention of thrombosis after hip or knee surgery. Bivalirudin (hirulog-1 or Angiomax), in adjunct to aspirin, was approved for prevention of thrombosis in patients with unstable angina following angioplasty. Argatroban has been used for the treatment of HIT, peripheral and cerebral thrombotic diseases. The benefit of using thrombin-specific inhibitors alone in acute myocardial infarction or unstable angina remains uncertain. Some of thrombin-specific inhibitors which are small molecules are orally active. The major concern for the use of thrombin-specific inhibitors is bleeding complication. The efficacy, safety, stability and oral bioavailability may be considerably improved through structural optimization. A growing line of evidence suggests that statins, the most commonly prescribed cholesterol lowering drug, may inhibit thrombin generation. Statins do not cause bleeding and have an outstanding safety profile. The findings suggest that further development of thrombin-specific inhibitors and exploration of the potential applications of non-specific thrombin inhibitors, including statins, may improve the prevention and management of thromboembotic events.

Hirudin-based anticoagulant strategy during isolated limb perfusion in a patient with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a rare but potentially fatal complication of heparin therapy. The administration of heparin in patients with HIT causes platelet aggregation, thromboembolism and thrombocytopenia. Therefore, an alternative anticoagulant is recommended in these patients. We describe the use of recombinant hirudin (r-hirudin; Refludan, Pharmion Germany GmbH, Hamburg, Germany) as an anticoagulant in a patient with HIT requiring isolated limb perfusion (ILP) for in-transit metastases of malignant melanoma of the leg; r-hirudin was used in both the extracorporeal and systemic circuits. The coagulation monitoring included the activated partial thromboplastin time (aPTT) and ecarin clotting time (ECT). There were no thrombotic or bleeding complications. The dosage regimen and the strategy of monitoring of the anticoagulant activity are described. It can be concluded that ILP in patients with suspected or confirmed HIT can be safely performed with the use of r-hirudin in both the extracorporeal and systemic circuits. Monitoring of the anticoagulation effect is necessary and should preferably be performed using ECT.

Congestive heart failure complicating non-ST segment elevation acute coronary syndrome: incidence, predictors, and clinical outcomes

There are limited data regarding the incidence and clinical significance of congestive heart failure (CHF) in patients with non-ST segment elevation acute coronary syndromes (ACS). The objectives of this study were to examine the incidence, predictors, and clinical outcomes in patients with ACS without ST elevation who develop CHF. We studied patients with unstable angina or non-ST segment elevation myocardial infarction (NSTEMI) randomized to hirudin or unfractionated heparin in the Organisation to Assess Strategies for Ischemic Syndromes (OASIS-2) trial. The diagnosis of CHF was based on a combination of clinical and radiographic features. Patients were followed for 6 months. Of 10 141 randomized patients, 501 (4.9%) developed CHF within the first week and 643 (6.3%) during 6 months of followup. Independent predictors for the development of CHF were older age, female sex, diabetes, prior MI, prior CHF, and NSTEMI at presentation. Compared with patients who did not develop CHF, patients who developed CHF were at increased risk of death (odds ratio (OR) 3.4, 95% CI 2.7-4.3), new MI (OR 2.8, 95% CI 2.2-3.6), and the need for intra-aortic balloon pump insertion (OR 5.4, 95% CI 3.5-8.4) at 7 days and 6 months. There was no increase in use of cardiac catheterization (OR 0.8, 95% CI 0.7-1.0) or revascularization (OR 0.9, 95% CI 0.7-1.1) in patients who developed CHF. CHF is a common complication in patients presenting with non-ST segment elevation ACS and is strongly associated with adverse clinical outcomes including new MI and death. Despite this worse prognosis, patients with ACS developing CHF are less likely to be referred for invasive management.

Thoughts and Progress. Protracted Bleeding After Hirudin Anticoagulation for Cardiac Surgery in a Patient With HIT II and Chronic Renal Failure

Heparin-induced thrombocytopenia type II (HIT II) requires alternative anticoagulation. Hirudin has been effectively used in patients with HIT II scheduled for cardiac surgery. However, bleeding complications were observed in patients with renal impairment. In vitro hemodialysis (HD) has been questioned over its efficacy in eliminating hirudin. Another approach to stop bleeding is the application of recombinant factor VIIa (rFVIIa). We report on a patient with HIT II and chronic renal failure who suffered from severe hirudin-induced bleeding after cardiac surgery who was safely treated with a combined approach of surgical hemostasis, substitution of blood products, HD, and rFVIIa to stop finally bleeding.

By what mechanism do leeches help to salvage ischaemic tissues? A review

The therapeutic use of leeches in medicine dates back to 50 b.c. and was cited by ancient authors. The medicinal leech, Hirudo medicinalis, has been used with increasing frequency during the past few years by reconstructive surgeons to help salvage ischaemic tissues. We aim to summarise the anatomy, physiology, and pharmacological mechanisms of action of leeches to provide reconstructive surgeons with a theoretical basis for their use.

Optimizing management of hirudin anticoagulation

Accurate anticoagulation monitoring, critical during cardiac surgery (CS), is especially important for novel therapeutics such as hirudins, for which there are no known antidotes. The activated clotting time (ACT), which is standard for heparin monitoring, has been reported to be insufficiently sensitive to high levels of hirudins. A simple, accurate, and sensitive assay is needed to monitor hirudins at the levels required for CS. During the REPLACE/II clinical trials, the HEMOCHRON Jr. Signature ACT+ was used to monitor Angiomax during percutaneous cardiac intervention (PCI) procedures and was observed to lose sensitivity at bivalirudin concentrations greater than 8-10 microg/mL. A new assay, the ACTT, was developed to increase the linear sensitivity of the ACT+ over the range of 15-30 microg/mL bivalirudin to extend the clinical utility of the assay to CS levels. Both in vitro and ex vivo studies were performed using the ACTT and ACT+. In vitro ACT+ and ACTT clotting times, identical for bivalirudin levels up to approximately 5 microg/mL, diverged from each other near 10 microg/mL. The ACTT showed excellent linearity to bivalirudin at concentrations up to 30 microg/ mL. Reproducibility was also superior with coefficients of variation <15% across 13 donors at clotting times <760 seconds. The ACTT was evaluated for monitoring bivalirudin during PCI in 67 patients. The ex vivo comparison of ACTT to ACT+ <340 seconds, showed a slope near 1.0 and an average difference between the tests of 5%. At higher clotting times this slope increased to near 3.0, with an average difference between tests of 20%. These data suggest that the ACTT displays increased sensitivity to high levels of bivalirudin.

[Use of ecarin clotting time in whole blood for monitoring recombinant hirudine treatment during cardiopulmonary bypass in patients with heparin-induced thrombocytopenia]

Lepirudin (Refludan is a recombinant hirudin, approved for anticoagulation treatment of heparin-induced thrombocytopenia patients with thrombosis. We report here our method for laboratory monitoring with ecarin clotting time (ECT) of hirudin therapy as anticoagulation for cardiac surgery. Ecarin is extracted from the Echis carinatus snake venom and directly converts prothrombin to its intermediate, meizothrombin. This one binds in a stoechiometric way to hirudin to be proportioned in whole blood. The activation of coagulation starts up only when the totality of the hirudin is bound to the meizothrombin. To minimize the effect of dilution related to the CEC on the prothrombin and fibrinogen levels, thus lengthening the ECT, the specimen to be tested is diluted with normal whole blood. In 1997, when we have performed our first surgery with cardiopulmonary bypass, only one team (Pötzsch et al., 1997) had described the use of the ECT in whole blood. We describe in this work our assay to dose hirudin with ECT after dilution in whole blood. This assay was used during 8 CEC among 7 patients affected with HIT (n = 6) or potentially sensitized with heparin (n = 1). Experimental conditions and interpretation of the assay are reported here. This test is fast enough to provide useful information for adjusting the dose during cardiopulmonary bypass.

Treatment of Patients with a History of Heparin-Induced Thrombocytopenia and Anti-Lepirudin Antibodies with Argatroban

Patients with heparin-induced thrombocytopenia (HIT) type II require anticoagulation with non-heparin immediate acting anticoagulants. Danaparoid may cross react with HIT-antibodies and lepirudin may generate anti-lepirudin antibodies influencing anticoagulation. We hypothesised, that the synthetic small molecular thrombin inhibitor argatroban does not induce immunoglobulins reacting towards lepirudin in patients with anti-lepirudin antibodies in the history and that titration of the anticoagulation may be easier with argatroban. We report on the treatment of four patients of a study, which was terminated prematurely due to official warnings for a repeated use of lepirudin. Two patients each received argatroban and lepirudin intravenously. A blinded assessor adjusted the doses of the anticoagulants to 1.5-3.0 fold prolongation of the aPTT. Ecarin clotting time (ECT), concentrations of lepirudin (ELISA) and of argatroban (gas-chromatography with mass spectrometry), and the generation of lepirudin antibodies (ELISA) were measured. APTT-adjusted dosages for argatroban was 2.0-2.6 microg/kg.min and for lepirudin 48-149 microg/kg.h. ECT was prolonged 2.1 to 4.5-fold with lepirudin and 4 to 7-fold with argatroban. The concentration of lepirudin ranged between 750 and 1500 ng/ml and of argatroban between 400 and 1100 ng/ml. Patients on argatroban did not generate immunoglobulin IgG reacting towards lepirudin in contrast to both patients on lepirudin who developed anti-lepirudin antibodies. Both treatments were well tolerated. Despite the low number of patients argatroban seems to lead to a more stable anticoagulant response than lepirudin resulting in a lower variability of the dosage for prophylaxis or treatment of thromboembolism of patients with a history of HIT and lepirudin antibodies.

Clinician update: direct thrombin inhibitors in acute coronary syndromes

Antithrombotic therapy has become the cornerstone of the treatment for atherosclerotic cardiovascular disease. Unfractionated heparin (UFH) has been the thrombin inhibitor of choice for decades. UFH, however, has its deficiencies. To overcome these problems several direct thrombin inhibitors (DTIs) have been developed. These agents are capable of inactivating clot-bound thrombin more efficiently, and provide more predictable and safer anticoagulation in patients with of acute coronary syndromes (ACS). The initial studies of hirudin and bivalirudin in the clinical settings of acute myocardial infarction (AMI), unstable angina (UA) and percutaneous coronary interventions (PCI) conducted in the early 1990s proved to be disappointing. As the knowledge of more appropriate use of these drugs progressed, there is a renewed interest in DTIs. Herein we will review the clinical studies assessing hirudin, bivalirudin and argatroban in the settings of AMI, UA and PCI.

Dynamic prognostication in non-ST-elevation acute coronary syndromes: insights from GUSTO-IIb and PURSUIT

BACKGROUND

Risk assessment in patients with non-ST-elevation acute coronary syndromes (NSTE-ACS) traditionally focuses on and is limited to admission findings. The objective of the current study was to develop an approach to predicting outcome in NSTE-ACS that could account for the changing nature of risk.

METHODS

In 7294 of 8010 patients with NSTE-ACS and complete electrocardiographic data in the GUSTO-IIb trial, we predicted the mortality probability at days 0-2, 0-30, 3-30, 5-30, and 7-30 using multiple logistic regression. Resulting risk estimates were incorporated into a composite, dynamic model to estimate the effects of changing probabilities over time. These models were validated against an independent sample of 9461 patients from the PURSUIT trial.

RESULTS

As time passed after admission, the risk of 30-day death declined in stable patients. This risk, which was 3.72% at baseline, declined to 1.92% in 6-day survivors, and the risk reduction was greatest for those with the highest baseline risk. Importantly, however, the development of inhospital complications modified these trends. The use of dynamic models not only allowed us to estimate early (<48 h) mortality with a high degree of accuracy (C-index of 0.87), but also to continuously update the longer-term prognosis with increasing accuracy: the C-index increased from 0.75 for the day 0-30 model to 0.81 and 0.82 for the composite and day 7-30 models, respectively.

CONCLUSIONS

Dynamic risk assessment is feasible and reliable. This approach can improve risk assessment and provide valuable guidance for management of patients with NSTE-ACS.

Direct Antithrombins: New Perspectives in Cardiovascular Medicine

Thrombin converts fibrinogen to fibrin and is the most powerful activator of platelets thus playing a crucial role in arterial and venous thrombosis. The limitations of heparin, largely used in the therapy of arterial and venous thromboembolism, has prompted the development of new antithrombotic drugs, able to directly inhibit thrombin. They comprise hirudin, bivalirudin and argatroban, which are antithrombins for parenteral use, and the orally active ximelagatran which, once absorbed, is converted to the active compound melagatran. Hirudin is a polypeptide able to irreversibly block both the active site and the fibrin(ogen) binding site of thrombin; bivalirudin, a synthetic hirudin derivative, has the same binding sites of hirudin to thrombin but has a shorter pharmacological action and is safer for clinical use. Several clinical trials which tested these drugs in acute coronary syndromes, coronary angioplasty and venous thromboembolism. demonstrate that hirudin and bivalirudin are superior to heparin in significantly reducing cardiac major events. The advantage of hirudin and bivalirudin over heparin was also confirmed in adjuncts to thrombolytic therapy as well as in percutaneous angioplasty relating to thrombotic events but not to restenosis. Hirudin was also significantly better than both unfractionated heparin and low molecular weight heparin (LMWH) in the prophylaxis of venous thromboembolism in patients undergoing elective arthroplasty. Major bleeding associated to hirudin was not different from that observed with heparin. Preliminary data also indicate that melagatran/ximelagatran may be used in the prophylaxis of venous thromboembolism and in the prevention of arterial embolism in patients with non-valvular atrial fibrillation.

Drugs for the prevention and treatment of thrombosis in patients with heparin-induced thrombocytopenia

Most patients with heparin-induced thrombocytopenia (HIT), a serious adverse effect of heparin mediated by platelet-activating heparin-dependent antibodies, require alternative anticoagulation. This is because HIT is highly prothrombotic and is characterized by markedly increased thrombin generation. Unfractionated heparins seem to induce HIT more often than low molecular weight heparins. There are three anticoagulants for which there is an emerging consensus for their efficacy in management of HIT, and which are currently approved for treatment of HIT in several countries: the recombinant hirudin, lepirudin, a direct thrombin inhibitor; the synthetic direct thrombin inhibitor, argatroban; and the heparinoid, danaparoid sodium, mainly exhibiting antifactor-Xa activity. Recommendations for optimal use of these drugs in HIT are given in this review stressing the need for immediate treatment of patients with HIT without awaiting laboratory diagnosis. Hirudin, the drug for which most data from prospective trials exists, can be safely and effectively used in patients with HIT, its dramatically increased elimination half-life in patients with renal failure being the most important drawback. Argatroban, which is mainly eliminated by the liver, could be used preferentially in such patients with renal impairment. Interference with the international normalized ratio makes oral anticoagulation, which is necessary in many patients with HIT, problematic. Activated partial thromboplastin time is sufficient to monitor lepirudin and argatroban treatment in most cases. Danaparoid sodium, with an antifactor-X activity half-life of about 24 hours seems to be best suited for thrombosis prophylaxis in patients with HIT. In some patients monitoring by determining antifactor-Xa activity is necessary. No antidote is available for any of the drugs discussed, and bleeding complications are the most important adverse effects. In situations such as hemodialysis or cardiopulmonary bypass, not only the characteristics of the drug in use itself, but also availability of monitoring methods play an important role. Adjunctive treatments have not been systematically evaluated and should be used cautiously. Recent data suggest that re-exposure of patients with a history of HIT with heparin, for example during cardiopulmonary bypass, can be well tolerated provided no circulating HIT antibodies are detectable at the time of re-exposure, and heparin is strictly avoided pre- and postoperatively.

Direct thrombin inhibitors in cardiac disease

Most acute coronary syndromes (ACS) are triggered by platelet-rich thrombus superimposed on disrupted atherosclerotic plaque. Thrombin and platelets both play a role in this process. Whereas unfractionated heparin and aspirin have served as cornerstones in the treatment of ACS, several limitations of heparin provide the impetus to seek out better anticoagulants. Direct thrombin inhibitors such as bivalirudin, hirudin, and argatroban offer several pharmacologic advantages over heparin. Additionally, bivalirudin also appears to provide clinical advantages over unfractionated heparin therapy in ACS patients and those undergoing percutaneous coronary intervention.

Historical perspective of the development of thrombin inhibitors

Progress in molecular biology has stimulated interest in the structure and function of thrombin. It has improved our understanding of its central role in thrombogenesis and has clarified the molecular events of inhibitor binding. This development has resulted in the production of recombinant hirudins and hirudin analogues. It has also allowed the molecular design of synthetic antithrombins, and encouraged the development of these products for clinical use. All pharmacological aspects speak in favor of the use of direct thrombin inhibitors as antithrombotic agents, especially in the potential indications where thrombin plays a crucial pathogenetic role. If their apparent advantages compared with heparin can be definitely demonstrated, the direct thrombin inhibitors may become the drug of choice for certain indications.

Heparin-induced thrombocytopenia and thrombosis syndrome after cardiac surgery

A case report of multisystem organ failure and limb loss associated with coronary artery bypass is reported. Heparin-induced thrombocytopenia and thrombosis syndrome (HITTS) occurs in 1% to 2% of patients suffering from thrombocytopenia associated with heparin or heparinoid use, which amounts to less than 1.4% of the cardiac surgical population. It carries a risk of significant comorbidity and mortality. Providers involved in the care of such patients should be well versed in the etiology and potential complications of HITTS, the treatment options, and alternative modalities of anticoagulation available for use.

Heparin-induced thrombocytopenia and cardiac surgery

Unfractionated heparin given during cardiopulmonary bypass is remarkably immunogenic, as 25% to 50% of postcardiac surgery patients develop heparin-dependent antibodies during the next 5 to 10 days. Sometimes, these antibodies strongly activate platelets and coagulation, thereby causing the prothrombotic disorder, heparin-induced thrombocytopenia. The risk of heparin-induced thrombocytopenia is 1% to 3% if unfractionated heparin is continued beyond the first postoperative week. When cardiac surgery is urgently needed for a patient with acute or subacute heparin-induced thrombocytopenia, options include an alternative anticoagulant (bivalirudin, lepirudin, or danaparoid) or combining unfractionated heparin with a platelet antagonist (epoprostenol or tirofiban). As heparin-induced thrombocytopenia antibodies are transient, unfractionated heparin alone is appropriate in a patient with previous heparin-induced thrombocytopenia whose antibodies have disappeared.

Delayed-type hypersensitivity skin reactions due to heparins and heparinoids. Tolerance of recombinant hirudins and of the new synthetic anticoagulant fondaparinux

Eczema-like, infiltrated plaques at subcutaneous heparin-injection sites are well-documented side effects of these anticoagulants. They are due to delayed-type hypersensitivity. In 4 patients, patch, intradermal and subcutaneous tests were performed with a panel of unfractionated heparins (UFHs), low-molecular-weight heparins (LMWHs), heparinoids, recombinant hirudins and a new synthetic pentasaccharide anticoagulant fondaparinux sodium, to find safe alternatives. 3 patients were sensitized to all the UFHs and LMWHs. The LMWH tinzaparin sodium and the heparinoid pentosan polysulfate were found to be a possible substitute in patient no. 1 and 2, respectively. The recombinant hirudins and fondaparinux sodium were tolerated without any side effects in all patients tested. Fondaparinux is a synthetic copy of a pentasaccharide sequence in the heparin molecule. It is the first in a new class of antithrombotic agents. Our study suggests that it is a new safe alternative in patients with eczema-like, infiltrated plaques at subcutaneous heparin-injection sites.

Direct thrombin inhibitors for non-ST-segment elevation acute coronary syndromes: what, when, and where?

BACKGROUND

Unfractionated heparin has been the cornerstone of antithrombin therapy in the treatment of non-ST-segment elevation acute coronary syndromes for more than a decade. Several new anticoagulants have emerged in recent years and have been studied extensively in patients with unstable coronary syndromes and in the percutaneous coronary intervention setting.

METHODS

Direct thrombin inhibitors comprise a family of agents with promising properties that offer several potential advantages over unfractionated heparin. Hirudin has been studied in patients with ST-elevation myocardial infarction, non-ST-elevation coronary syndromes, and coronary angioplasty. Bivalirudin has been studied in patients undergoing percutaneous coronary revascularization, with very promising efficacy and safety profile compared with unfractionated heparin.

RESULTS

The clinical trials of direct thrombin inhibitors in non-ST-elevation acute coronary syndromes and coronary angioplasty are reviewed.

Heparin-induced thrombocytopenia and cardiac surgery

Unfractionated heparin given during cardiopulmonary bypass is remarkably immunogenic, as 25% to 50% of postcardiac surgery patients develop heparin-dependent antibodies during the next 5 to 10 days. Sometimes, these antibodies strongly activate platelets and coagulation, thereby causing the prothrombotic disorder, heparin-induced thrombocytopenia. The risk of heparin-induced thrombocytopenia is 1% to 3% if unfractionated heparin is continued throughout the postoperative period. When cardiac surgery is urgently needed for a patient with acute or subacute heparin-induced thrombocytopenia, options include an alternative anticoagulant (bivalirudin, lepirudin, or danaparoid) or combining unfractionated heparin with a platelet antagonist (epoprostenol or tirofiban). As heparin-induced thrombocytopenia antibodies are transient, unfractionated heparin alone is appropriate in a patient with previous heparin-induced thrombocytopenia whose antibodies have disappeared.

Heparin-induced thrombocytopenia--recognition and treatment

Heparin, an important agent for the prophylaxis and treatment of venous and arterial thromboembolism, also can cause heparin-induced thrombocytopenia (HIT). This medication-induced immune-mediated syndrome is characterized by thrombocytopenia and life- or limb-threatening thrombotic events. The initial presentation of HIT is a decrease in platelet count with or without thrombosis. Heparin-induced thrombocytopenia frequently is overlooked in hospital settings, and it must be distinguished from other causes of thrombocytopenia. New therapies include the use of direct thrombin inhibitors argatroban and hirudin.

Current anticoagulation options in percutaneous intervention: designing patient-specific strategies

Anticoagulation during percutaneous coronary intervention is critical to prevent abrupt and subacute closure. Although heparin has been the primary anticoagulant used for this purpose, a number of new drugs are now available. Low molecular weight heparin (LMWH) offers some advantages over unfractionated heparin, and clinical trials have shown its superiority. However, the longer half-life and lack of monitoring of LMWH make its use more difficult. The direct thrombin inhibitors also have been shown to have advantages in the treatment of patients with heparin-induced thrombocytopenia.

Management of heparin resistance during cardiopulmonary bypass: the effect of five different anticoagulation strategies on hemostatic activation

OBJECTIVE

Attenuation of hemostatic activation is a central goal during CPB. However, this poses a problem in patients insensitive to heparin. The present investigation was performed to assess different strategies of managing patients with heparin resistance during CPB.

DESIGN

A randomized, prospective clinical investigation.

SETTING

A major European heart center.

PARTICIPANTS

Five groups with 20 patients each were investigated.

INTERVENTIONS

The groups were handled as follows: (1). maintenance of a target ACT, (2). maintenance of the target unfractionated heparin (UFH) level and supplementation of a UFH level-based strategy with (3). AT III, (4). the direct thrombin inhibitor r-hirudin, or (5). the short-acting platelet glycoprotein (GP) IIb/IIIa antagonist tirofiban. Platelet count and generation of contact factor XIIa, thrombin, and soluble fibrin were assessed. Samples were obtained before CPB and after CPB before protamine infusion.

MEASUREMENTS AND MAIN RESULTS

There were no differences observed in the generation of factor XIIa. The UFH-based strategy and supplementation with AT III, r-hirudin, and tirofiban resulted in significantly reduced (p < 0.05) thrombin generation compared with ACT management. A significant reduction of fibrin formation was seen only in patients who received AT III, r-hirudin, or tirofiban supplementation to the UFH. The administration of tirofiban resulted in a significant preservation of the platelet count compared with the other groups. There were no significant differences in the postoperative blood loss.

CONCLUSIONS

Activation of hemostasis during CPB in heparin-resistant patients most likely has to be attributed to stimulation of the tissue factor pathway. Even the sole use of high concentrations of UFH does not effectively inhibit this activation. Therefore, in these patients anticoagulation during CPB with UFH should be supplemented with either AT III, a short-acting direct thrombin inhibitor, or a short-acting platelet glycoprotein IIb/IIIa antagonist.

Anticoagulation in acute cardiac care in patients with chronic kidney disease

The number of patients with coexisting chronic kidney disease (CKD) and cardiovascular disease is growing rapidly. Treatment of these patients is challenging, primarily because of a lack of pharmacokinetic and clinical trial data associated with these combined disease entities. In this report, we discuss the cardiovascular disease risk associated with CKD and review the use of anticoagulation for acute cardiovascular disease in patients with CKD. We evaluate the potential role of direct thrombin inhibitors in patients with renal disease who have acute coronary syndromes, with particular focus on the clinical efficacy of bivalirudin. We conclude that direct thrombin inhibitors, including bivalirudin and argatroban, may be promising alternatives to heparin in patients who have renal insufficiency and are therefore at an increased risk for bleeding. In the treatment of patients with advanced renal insufficiency and cardiovascular disease, however, these agents should be used with dose modification to account for altered excretion.

The benefit-to-risk profile of melagatran is superior to that of hirudin in a rabbit arterial thrombosis prevention and bleeding model

Although hirudin is better than heparin at preventing recurrent ischemia in patients with unstable angina, hirudin produces more bleeding. The purpose of this study was to use a rabbit arterial thrombosis prevention and ear bleeding model to determine whether for equivalent efficacy, melagatran, a synthetic direct thrombin inhibitor, is safer than hirudin. A combination of balloon injury and stasis was used to induce thrombosis in the distal aorta, and patency and blood flow were continuously monitored with ultrasonic flow probes. Rabbits were randomized to melagatran (in total doses of 78-313 nmol kg(-1)), hirudin (in total doses of 18-107 nmol kg(-1)), or saline over 90 min. To assess safety, blood loss from standardized ear incisions was measured. Both melagatran and hirudin produced dose-dependent increases in patency and blood flow. At doses that maintained the highest levels of patency, however, melagatran produced 2-3-fold less bleeding than hirudin. Thus, at maximally effective doses, melagatran causes less bleeding than hirudin in this model. These findings raise the possibility that some direct thrombin inhibitors are safer than others.

The return of the leech

Medicinal leeches (Hirudo medicinalis) have been used in medicine for thousands of years to treat a wide range of ailments. Nowadays, leeches are used successfully for only a few conditions, notably in the field of reconstructive or microsurgery, to salvage tissue flaps and skin grafts whose viability is threatened by venous congestion. The anticoagulant properties of hirudin, contained in leech saliva, may lead to wider therapeutic applications in the prevention and treatment of thromboembolic disease. Optimal care is needed when applying leeches, because their use can be complicated by serious bacterial infections.

[Treatment and prevention of venous thromboembolic events: present and future antithrombotic agents]

Two new classes of anticoagulants are actually developed which would change in the near future our strategies for the prevention and the treatment of venous thromboembolic events. These two classes are the anti-factor Xa and anti-factor IIa (direct antithrombin) agents. Among the anti factor Xa, the pentasaccharides are initiating their clinical use. Fondaparinux is a synthetic form of the natural pentasaccharide, its pharmacokinetics allows one s.c. administration/24 hours. It is active in prevention and treatment of venous thromboembolic and coronary thrombotic events. A modified form (idraparinux) whose pharmacokinetics allows one administration only once a week should have the same type of efficacy. Among direct antithrombin agents, hirudin and derivatives have been developed in the past decade with a limited use due to several drawback. More recently synthetic direct antithrombins modified to allow oral route have been developed, the most advanced in development, melagatran, is active in the prevention and treatment of venous thromboembolic and coronary thrombotic events. It could allow (if confirmed by clinical trials) a complete oral treatment of deep vein thrombosis without any biological monitoring. Melagatran is also active in the prevention of arterial thromboembolic events on atrial fibrillation. But other molecular forms of synthetic orally active direct antithrombin are also in development. Besides these important changes in our therapeutics which should appear in a near future, molecules aimed at other target are also tested: the most advanced are those antagonizing the initial phase of tissue factor activation of factor VII but other strategies are being tested such as stimulation of fibrinolysis. These new drugs at our disposal to treat venous thromboembolism should modify completely our handling of the patients. But additionally the numerous clinical trials necessary to prove the efficacy of the drugs, modify our understanding in the implication of the coagulation and in the physiopathogeny of thrombotic events.