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Warkentin TE. Immunologic Effects of Heparin Associated With Hemodialysis: Focus on Heparin-Induced Thrombocytopenia. Semin Nephrol 2023; 43:151479. [PMID: 38195304 DOI: 10.1016/j.semnephrol.2023.151479] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Intermittent hemodialysis (HD) is almost invariably performed with heparin, and thus HD patients are at risk of developing the immune-mediated adverse effect heparin-induced thrombocytopenia (HIT), caused by anti-platelet factor 4/heparin IgG, which strongly activates platelets. HIT patients develop hypercoagulability with greatly increased risk of thrombosis, both venous and arterial. Certain HIT-associated complications are more likely to develop among HD patients, including hemofilter thrombosis despite heparin, intravascular catheter and/or arteriovenous fistula-associated thrombosis, post-heparin bolus anaphylactoid/anaphylactic reactions, and thrombotic stroke and acute limb artery thrombosis (reflecting the high frequency of underlying arteriopathy in many patients with renal failure). Management of HIT in HD usually requires use of an alternative (non-heparin) anticoagulant; for example, danaparoid sodium (outside the USA) or argatroban (USA and elsewhere). Whether heparin-grafted hemodialyzers (without systemic heparin) can be used safely in acute HIT is unknown. The HIT immune response is remarkably transient and usually not retriggered by subsequent heparin administration. Accordingly, since renal failure patients often require long-term HD, there may be the opportunity-following seroreversion (loss of platelet-activating HIT antibodies)-to restart heparin for HD, a practice that appears to have a low likelihood of retriggering HIT.
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Affiliation(s)
- Theodore E Warkentin
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada; Department of Medicine, McMaster University, Hamilton, Canada; Transfusion Medicine, Hamilton Regional Laboratory Medicine Program, Hamilton General Hospital, Hamilton Health Sciences, Hamilton, Canada; Service of Benign Hematology, Hamilton General Hospital, Hamilton Health Sciences, Hamilton, Canada.
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Warkentin TE. Heparin-induced thrombocytopenia (and autoimmune heparin-induced thrombocytopenia): an illustrious review. Res Pract Thromb Haemost 2023; 7:102245. [PMID: 38193057 PMCID: PMC10772877 DOI: 10.1016/j.rpth.2023.102245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 06/14/2023] [Indexed: 01/10/2024] Open
Affiliation(s)
- Theodore E. Warkentin
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada
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Aungraheeta R, FitzGibbon L, Reilly-Stitt C, Mumford AD. Differential effects of direct factor IIa and factor Xa inhibitors in protein C-deficient plasma detected using thrombin generation and viscoelastometry assays. Int J Lab Hematol 2019; 42:126-133. [PMID: 31756037 DOI: 10.1111/ijlh.13126] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 10/27/2019] [Accepted: 10/28/2019] [Indexed: 11/28/2022]
Abstract
INTRODUCTION Protein C (PC) deficiency results in dysregulated thrombin generation and increases thrombosis risk. METHODS In order to investigate the potential effects of anticoagulant drugs in PC deficiency, we evaluated the pharmacodynamic effect of selective direct factor (F) IIa inhibitors (dabigatran and argatroban), selective direct FXa inhibitors (rivaroxaban and apixaban) and an indirect FXa/FIIa inhibitor (enoxaparin) in commercial PC-deficient plasma using thrombin generation and viscoelastometry assays modified to reflect PC anticoagulant activity. RESULTS Endogenous thrombin potential (ETP) and peak thrombin concentration (PTC) were increased in PC-deficient plasma but this corrected completely with PC concentrate. Inhibition of FIIa and FXa with the selective inhibitors also corrected the increased ETP and PTC but required high drug concentrations. There was sustained low-level thrombin generation in PC-deficient plasma with FXa inhibitors but not with FIIa inhibitors. Adding PC concentrate to PC-deficient plasma anticoagulated with dabigatran had little additional effect on ETP or PTC. In contrast, addition of even small quantities of PC concentrate to PC-deficient plasma anticoagulated with rivaroxaban further diminished ETP, primarily by abolishing sustained thrombin generation. In the viscoelastometry assay, the coagulation time was shortened and α-angle increased in PC-deficient plasma. These abnormalities reversed with both dabigatran and rivaroxaban. CONCLUSION The selective direct FXa and FIIa inhibitors at high concentrations both counteracted the abnormal thrombin generation and clot formation observed in PC-deficient plasma, but with qualitative differences in their effects.
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Affiliation(s)
- Riyaad Aungraheeta
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol, UK
| | - Lucy FitzGibbon
- Department of Haematology, University Hospitals Bristol NHS Foundation Trust, Bristol, UK
| | | | - Andrew D Mumford
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol, UK.,Department of Haematology, University Hospitals Bristol NHS Foundation Trust, Bristol, UK
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Kamisato C, Furugohri T, Morishima Y. A direct thrombin inhibitor suppresses protein C activation and factor Va degradation in human plasma: Possible mechanisms of paradoxical enhancement of thrombin generation. Thromb Res 2016; 141:77-83. [PMID: 26974491 DOI: 10.1016/j.thromres.2016.03.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 03/02/2016] [Accepted: 03/02/2016] [Indexed: 11/16/2022]
Abstract
We have demonstrated that antithrombin (AT)-independent thrombin inhibitors paradoxically increase thrombin generation (TG) in human plasma in a thrombomodulin (TM)- and protein C (PC)-dependent manner. We determined the effects of AT-independent thrombin inhibitors on the negative-feedback system, activation of PC and production and degradation of factor Va (FVa), as possible mechanisms underlying the paradoxical enhancement of TG. TG in human plasma containing 10nM TM was assayed by means of the calibrated automated thrombography. As an index of PC activation, plasma concentration of activated PC-PC inhibitor complex (aPC-PCI) was measured. The amounts of FVa heavy chain and its degradation product (FVa(307-506)) were examined by western blotting. AT-independent thrombin inhibitors, melagatran and dabigatran (both at 25-600nM) and 3-30μg/ml active site-blocked thrombin (IIai), increased peak levels of TG. Melagatran, dabigatran and IIai significantly decreased plasma concentration of aPC-PCI complex at 25nM or more, 75nM or more, and 10 and 30μg/ml, respectively. Melagatran (300nM) significantly increased FVa and decreased FVa(307-506). In contrast, a direct factor Xa inhibitor edoxaban preferentially inhibited thrombin generation (≥25nM), and higher concentrations were required to inhibit PC activation (≥150nM) and FVa degradation (300nM). The present study suggests that the inhibitions of protein C activation and subsequent degradation of FVa and increase in FVa by antithrombin-independent thrombin inhibitors may contribute to the paradoxical TG enhancement, and edoxaban may inhibit PC activation and FVa degradation as a result of TG suppression.
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Affiliation(s)
- Chikako Kamisato
- Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
| | - Taketoshi Furugohri
- Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
| | - Yoshiyuki Morishima
- Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.
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Taneja R, Liaw PL, Al Ghazaly S, Priestap F, Murkin JM, Martin CM. Effect of cardiopulmonary bypass on thrombin generation and protein C pathway. J Cardiothorac Vasc Anesth 2013; 27:35-40. [PMID: 23312776 DOI: 10.1053/j.jvca.2012.09.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The purpose of this study was to evaluate the mechanisms of cardiopulmonary bypass (CPB)-induced dysregulation between thrombin and its regulatory anticoagulant activated protein C (APC). DESIGN A prospective observational cohort study. SETTING A tertiary care university hospital and associated research laboratory. PATIENTS Twenty patients undergoing elective coronary artery bypass surgery with (n = 10) or without CPB (n = 10). INTERVENTIONS Blood samples were collected at 7 time points: preinduction; after heparin; 1 hour after the institution of CPB (or the completion of distal anastomoses in off-CPB group); after protamine; and at 0, 4, and 18 hours in the Intensive care unit (ICU). Samples were analyzed for prothrombin fragments (F1+2), thrombin-antithrombin complexes, protein C (PC), APC, soluble thrombomodulin (sTM), and soluble endothelial protein C receptor (sEPCR). MEASUREMENTS AND MAIN RESULTS F1+2 levels increased significantly 1 hour after the initiation of CPB in comparison with baseline (2.7 ± 0.5 v 0.5 ± 0.2 nmol/L, p < 0.001) (mean ± standard deviation) and remained elevated until 4 hours after ICU admission (p < 0.001). In contrast, APC levels did not show any significant changes over time in either group. sEPCR, sTM, and PC levels did not change during CPB although sEPCR decreased significantly after the termination of CPB compared with baseline in the CPB group. CONCLUSIONS Exposure to CPB is associated with a distinct thrombin surge that continues postoperatively for 4 hours. The impaired ability to generate APC reflects a complex process that is not associated with increased levels of sEPCR and thrombomodulin during CPB. Further studies are required to evaluate the regulation of the host APC response in cardiac surgery.
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Affiliation(s)
- Ravi Taneja
- Centre for Critical Illness Research, Lawson Health Research Institute, London Health Sciences Centre, London, Ontario, Canada.
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Smoum R, Rubinstein A, Dembitsky VM, Srebnik M. Boron containing compounds as protease inhibitors. Chem Rev 2012; 112:4156-220. [PMID: 22519511 DOI: 10.1021/cr608202m] [Citation(s) in RCA: 300] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Reem Smoum
- The School of Pharmacy, Institute for Drug Research, The Hebrew University of Jerusalem, Faculty of Medicine, Jerusalem, Israel.
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Furugohri T, Sugiyama N, Morishima Y, Shibano T. Antithrombin-independent thrombin inhibitors, but not direct factor Xa inhibitors, enhance thrombin generation in plasma through inhibition of thrombin-thrombomodulin-protein C system. Thromb Haemost 2011; 106:1076-83. [PMID: 22012070 DOI: 10.1160/th11-06-0382] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 08/27/2011] [Indexed: 11/05/2022]
Abstract
There is increasing concern that some anticoagulants can paradoxically increase thrombogenesis under certain circumstances. Previously, we demonstrated that at certain doses a direct thrombin inhibitor, melagatran, worsens the coagulation status induced by tissue factor (TF) injection in a rat model. We utilised an in vitro thrombin generation (TG) assay to determine if direct thrombin inhibitors could enhance TG in human plasma, and whether inhibition of the negative-feedback system [thrombin-thrombomodulin (TM)-protein C] contributed to the TG enhancement. TG in human plasma was assayed by means of the calibrated automated thrombography. In this assay, direct factor Xa (FXa) inhibitors such as edoxaban and antithrombin (AT)-dependent anticoagulants such as heparin did not increase, but simply suppressed TG. AT-independent thrombin inhibitors (melagatran, lepirudin, and active site blocked thrombin (IIai)) increased peak levels of TG (2.0, 1.6, and 2.2-fold, respectively) in the presence of 12 nM recombinant human soluble TM (rhsTM). Melagatran and lepirudin at higher concentrations began to suppress TG. In the absence of rhsTM, the enhancement of peak TG by melagatran decreased to 1.2-fold. Furthermore, in protein C-deficient plasma, AT-independent thrombin inhibitors failed to enhance TG. In addition, a human protein C neutralising antibody increased the peak height of TG in the presence of rhsTM. These results suggest that AT-independent thrombin inhibitors may activate thrombogenesis by suppression of the thrombin-induced negative-feedback system through inhibition of protein C activation. In contrast, direct FXa inhibitors are more useful than AT-independent thrombin inhibitors in terms of lower possibility of activation of the coagulation pathway.
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Affiliation(s)
- Taketoshi Furugohri
- Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.
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van Sluis GL, Brüggemann LW, Esmon CT, Kamphuisen PW, Richel DJ, Büller HR, van Noorden CJF, Spek CA. Endogenous activated protein C is essential for immune-mediated cancer cell elimination from the circulation. Cancer Lett 2011; 306:106-10. [PMID: 21420234 DOI: 10.1016/j.canlet.2011.02.038] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/21/2011] [Accepted: 02/23/2011] [Indexed: 01/05/2023]
Abstract
Fibrinogen and platelets play an important role in cancer cell survival in the circulation by protecting cancer cells from the immune system. Moreover, endogenous activated protein C (APC) limits cancer cell extravasation due to sphingosine-1-phosphate receptor-1 (S(1)P(1)) and VE-cadherin-dependent vascular barrier enhancement. We aimed to study the relative contribution of these two mechanisms in secondary tumor formation in vivo. We show that fibrinogen depletion limits pulmonary tumor foci formation in an experimental metastasis model in C57Bl/6 mice but not in NOD-SCID mice lacking a functional immune system. Moreover, we show that in the absence of endogenous APC, fibrinogen depletion does not prevent cancer cell dissemination and secondary tumor formation in immune-competent mice. Overall, we thus show that endogenous APC is essential for immune-mediated cancer cell elimination.
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Affiliation(s)
- G L van Sluis
- Department of Vascular Medicine, Academic Medical Center, Amsterdam, The Netherlands
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Benedetto BJ, Houston MA. A case report of a new pulmonary embolism occurring in a patient receiving continuous infusion of recombinant activated protein C. World J Emerg Surg 2006; 1:23. [PMID: 16899129 PMCID: PMC1557485 DOI: 10.1186/1749-7922-1-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2006] [Accepted: 08/09/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND There are no guidelines governing the concomitant use of recombinant human activated protein C (rhAPC) and deep venous thrombosis/pulmonary embolism (DVT/PE) prophylaxis in critically ill patients. It is unknown if rhAPC provides any protection against DVT/PE in this population of patients. METHODS Case report. RESULTS This report describes the first case of a radiographically demonstrated pulmonary embolism occurring in a patient receiving continuous therapeutic infusion of rhAPC. CONCLUSION The administration of rhAPC alone may not be sufficient DVT/PE prophylaxis in high risk patients. The risks associated with concomitant anticoagulation and rhAPC therapy are unknown. Further research is necessary to determine the safest and most effective regimen for DVT/PE prophylaxis in patients receiving rhAPC.
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Affiliation(s)
- Bernard J Benedetto
- Rhode Island Hospital, Brown University School of Medicine, 2 Dudley Street, Providence, RI, USA
| | - Michael A Houston
- University of North Carolina Medical Center, University of North Carolina School of Medicine, Chapel Hill, NC, USA
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Furugohri T, Shiozaki Y, Muramatsu S, Honda Y, Matsumoto C, Isobe K, Sugiyama N. Different antithrombotic properties of factor Xa inhibitor and thrombin inhibitor in rat thrombosis models. Eur J Pharmacol 2005; 514:35-42. [PMID: 15878322 DOI: 10.1016/j.ejphar.2005.03.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Revised: 02/28/2005] [Accepted: 03/02/2005] [Indexed: 10/25/2022]
Abstract
We compared the antithrombotic properties of a factor Xa inhibitor (DX-9065a) with those of a thrombin inhibitor (melagatran) in a rat disseminated intravascular coagulation model and a rat venous thrombosis model. Rat disseminated intravascular coagulation and venous thrombosis models were produced by injection of tissue factor and platinum wire placement, respectively. DX-9065a exerted antithrombotic effects dose dependently in both models. Melagatran was also effective in the venous thrombosis model, whereas it showed an aggravation in the disseminated intravascular coagulation model at low but not high doses. In the in vitro study, DX-9065a decreased the C(max) of the thrombin generation curve in plasma irrespective of whether protein C was present or not. However, melagatran increased the C(max) at low concentrations when protein C was present. This increase was not detected in protein C-deficient plasma. These results suggest that, unlike DX-9065a, melagatran in low doses aggravates disseminated intravascular coagulation by increasing thrombin generation, which may be partly due to suppression of negative feedback by activated protein C.
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Affiliation(s)
- Taketoshi Furugohri
- New Product Research Laboratories II, Tokyo R & D Center, Daiichi Pharmaceutical Co. Ltd., 16-13, Kita-kasai 1-chome Edogawa-ku, Tokyo 134-8630, Japan
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Fourrier F. Recombinant human activated protein C in the treatment of severe sepsis: An evidence-based review. Crit Care Med 2004; 32:S534-41. [PMID: 15542961 DOI: 10.1097/01.ccm.0000145944.64532.53] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for recombinant human activated protein C that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and improve outcome in severe sepsis. DESIGN The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee. METHODS The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591. CONCLUSION Recombinant human activated protein C is recommended in patients at high risk of death (septic shock, sepsis-induced acute respiratory distress syndrome, Acute Physiology and Chronic Health Evaluation II score of >/=25, and sepsis-induced multiorgan failure) and no absolute contraindication related to bleeding risk or relative contraindication that outweighs the potential benefit. The presence or absence of disseminated intravascular coagulation should not influence the decision to administer recombinant human activated protein C. Heparin should be withheld during administration of recombinant human activated protein C.
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Affiliation(s)
- François Fourrier
- Département Universitaire de Réanimation et Urgences Médicales, Faculté de Médecine, Université de Lille 2, Lille, France
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Macias WL, Yan SB, Grinnell BW. The development of drotrecogin alfa (activated) for the treatment of severe sepsis. Int J Artif Organs 2004; 27:360-70. [PMID: 15202813 DOI: 10.1177/039139880402700504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- W L Macias
- Lilly Laboratory for Clinical Research, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
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Abstract
PURPOSE OF REVIEW An update on recent developments in diagnosis and treatment of disseminated intravascular coagulation. RECENT FINDINGS Disseminated intravascular coagulation is defined as a typical disease condition with laboratory findings indicating massive coagulation activation and reduction in procoagulant capacity. Clinical syndromes associated with the condition are consumption coagulopathy, sepsis-induced purpura fulminans, and viral hemorrhagic fevers. Consumption coagulopathy is observed in patients with sepsis, aortic aneurysms, acute promyelocytic leukemia, and other disseminated malignancies. Sepsis-induced purpura fulminans is characterized by microvascular occlusion causing hemorrhagic necrosis of the skin and organ failure. Viral hemorrhagic fevers result in massively increased tissue factor production in monocytes and macrophages, inducing microvascular thrombosis and consumption of platelets and coagulation factors. Current scoring systems do not distinguish between patients with asymptomatic disseminated intravascular coagulation, consumption coagulopathy and thrombotic syndromes. Patients with sepsis may be identified by activated partial thromboplastin time waveform analysis performed as part of routine coagulation testing. Drotrecogin alpha (activated) reduces mortality in patients with severe sepsis with and without disseminated intravascular coagulation and has been used in patients with sepsis-induced purpura fulminans. Tifacogin does not reduce mortality in severe sepsis associated with impaired coagulation. Patients with heterozygous factor V Leiden mutation and severe sepsis showed a lower 28-day mortality than patients without this mutation, supporting the assumption that an enhanced level of coagulation activation may be beneficial in patients with severe sepsis. SUMMARY Whereas antithrombin and tifacogin failed to improve clinical outcome in severe sepsis, drotrecogin alpha (activated) increased the chances of survival of patients with severe sepsis with and without disseminated intravascular coagulation.
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Affiliation(s)
- Carl-Erik Dempfle
- Department of Medicine, University Hospital of Mannheim, Mannheim, Germany.
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Macias W, Yan SB. Antithrombin and heparin may limit the activation of Protein C. Acta Anaesthesiol Scand 2004; 48:385. [PMID: 14982578 DOI: 10.1111/j.0001-5172.2004.0320b.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Vitamin K antagonists are effective oral anticoagulants, but they have limitations related to a narrow therapeutic range, food and drug interactions, slow onset of action and the need for routine coagulation monitoring. Ximelagatran is a promising new oral anticoagulant under investigation in advanced clinical trials. It is a prodrug that is converted after oral administration to melagatran, a direct thrombin inhibitor, with a peak effect after 2 hours and a half-life of approximately 3 hours with primarily renal excretion. Administration results in prolongation of coagulation tests, but routine monitoring is not required because of reliable absorption and predictable effects. A large clinical trials program has demonstrated effectiveness in prophylaxis of deep vein thrombosis (DVT) following major orthopedic surgery, treatment of symptomatic DVT, prevention of embolism in patients with atrial fibrillation, and prophylaxis of recurrent events after acute myocardial infarction. Bleeding complications have been similar to those with standard therapy, with no unexpected adverse effects except for elevation of serum transaminase levels in over 6% of patients beginning after 1 month of therapy. Ximelagatran may be an alternative oral anticoagulant for patients currently taking vitamin K antagonists.
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Affiliation(s)
- Charles W Francis
- Hematology/Oncology Unit, School of Medicine and Dentistry, University of Rochester, 601 Elmwood Avenue, Box 610, Rochester, NY, USA.
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Linder R, Frebelius S, Grip L, Swedenborg J. The influence of direct and antithrombin-dependent thrombin inhibitors on the procoagulant and anticoagulant effects of thrombin. Thromb Res 2003; 110:221-6. [PMID: 14512086 DOI: 10.1016/s0049-3848(03)00344-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
INTRODUCTION Clinical trials evaluating direct thrombin inhibitors in unstable coronary artery disease (CAD) have been disappointing. The hypothesis tested in the present study was that these agents may inhibit the anticoagulant effect of thrombin to a further extent than the procoagulant effect of thrombin. MATERIALS AND METHODS We studied both reversible and irreversible thrombin inhibitors and compared the effects of each inhibitor on activated protein C (APC) generation vs. the effect on fibrinopeptide A (FPA) generation. A mixture of protein C, thrombin inhibitor, fibrinogen, fibrin polymerisation blocker and thrombin was incubated with thrombomodulin (TM)-expressing human saphenous vein endothelial cells (HSVECs). The inhibitors investigated were melagatran, inogatran, hirudin, hirugen, D-Phe-D-Pro-D-arginyl chloromethyl ketone (PPACK), and antithrombin (AT) alone or in combination with unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). RESULTS All agents, except hirugen, inhibited APC and FPA generation in a dose-dependent manner. FPA inhibition/APC inhibition ratios, based on IC50 for inogatran, melagatran, hirudin, PPACK, AT, AT-UFH and AT-LMWH were 1.73, 0.85, 0.55, 2.1, 0.5, 0.65 and 3.1 respectively. CONCLUSIONS All agents, except hirugen, inhibited APC and FPA generation approximately to a similar extent. Thus, it can be inferred that the poor efficacy of thrombin inhibitors in recent clinical trials in patients with unstable CAD is unlikely to be a consequence of their effects on the protein C system.
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Affiliation(s)
- Rikard Linder
- Department of Cardiology, Karolinska Hospital, S-171 76, Stockholm, Sweden.
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