Publications by authors named "Lars M Asmis"

33 Publications

The Excretory/Secretory and Surface Proteome Contains Putative Modulators of the Host Coagulation.

Front Cell Infect Microbiol 2021 2;11:753320. Epub 2021 Nov 2.

Institute of Parasitology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.

is a cardiopulmonary nematode of canids and is, among others, associated with bleeding disorders in dogs. The pathogenesis of such coagulopathies remains unclear. A deep proteomic characterization of sex specific excretory/secretory proteins (ESP) and of cuticular surface proteins was performed, and the effect of ESP on host coagulation and fibrinolysis was evaluated . Proteins were quantified by liquid chromatography coupled to mass spectrometry and functionally characterized through gene ontology and pathway enrichment analysis. In total, 1069 ESP (944 from female and 959 from male specimens) and 1195 surface proteins (705 and 1135, respectively) were identified. Among these were putative modulators of host coagulation, e.g., von Willebrand factor type D domain protein orthologues as well as several proteases, including serine type proteases, protease inhibitors and proteasome subunits. The effect of ESP on dog coagulation and fibrinolysis was evaluated on canine endothelial cells and by rotational thromboelastometry (ROTEM). After stimulation with ESP, tissue factor and serpin E1 transcript expression increased. ROTEM revealed minimal interaction of ESP with dog blood and ESP did not influence the onset of fibrinolysis, leading to the conclusion that ESP and surface proteins are not solely responsible for bleeding in dogs and that the interaction with the host's vascular hemostasis is limited. It is likely that coagulopathies in infected dogs are the result of a multifactorial response of the host to this parasitic infection.
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http://dx.doi.org/10.3389/fcimb.2021.753320DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8593241PMC
November 2021

Management of bleeding events and invasive procedures in patients with haemophilia A without inhibitors treated with emicizumab.

Swiss Med Wkly 2020 Dec 18;150:w20422. Epub 2020 Dec 18.

Department of Haematology and Central Haematology Laboratory, Inselspital, Bern University Hospital, University of Bern, Switzerland.

Introduction: Emicizumab (Hemlibra®, Hoffmann-La Roche, Switzerland) is now available for haemophilia A patients with or without factor VIII inhibitors. Management of bleeding events and replacement therapy for invasive procedures have to be adapted.

Objective: To provide a practical guidance for the management of breakthrough bleeding events and elective or urgent surgery in adult and paediatric patients with haemophilia A without inhibitors treated with emicizumab.

Methods: Based on the available literature and the experiences collected from adult and paediatric patients treated in Switzerland, the Working Party on Haemostasis of the Swiss Society of Haematology and the Swiss Haemophilia Network worked together to reach a consensus on the management of bleeding events and invasive procedures.

Results And Conclusion: Minor bleeding events and invasive procedures associated with low bleeding risk can be treated without factor replacement therapy in most cases, whereas major bleeding events and high-risk surgery require additional factor VIII replacement at usual doses, at least for the first days. Emicizumab treatment should be continued throughout the procedure and during the postoperative period. Elective major surgery should be planned according to emicizumab dosing for patients with a once-a-month posology. Of note, so far only few data are available on the management of major bleeds and surgery in patients with haemophilia A treated with emicizumab and this practical guidance will have to be regularly updated with growing experience.  .
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http://dx.doi.org/10.4414/smw.2020.20422DOI Listing
December 2020

Assessment of platelet function utilizing viscoelastic testing.

Transfusion 2020 10;60 Suppl 6:S10-S20

Centre for Perioperative Thrombosis and Haemostasis, Zurich, Switzerland.

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http://dx.doi.org/10.1111/trf.16081DOI Listing
October 2020

Efficacy of a new pathogen-reduced cryoprecipitate stored 5 days after thawing to correct dilutional coagulopathy in vitro.

Transfusion 2019 05 4;59(5):1818-1826. Epub 2019 Feb 4.

Department of Anaesthesia, Zurich University Children's Hospital, Zurich, Switzerland.

Background: Fibrinogen supplementation during bleeding restores clot strength and hemostasis. Cryoprecipitate, a concentrated source of fibrinogen, has prolonged preparation time for thawing, a short shelf life resulting in frequent wastage, and infectious disease risk. This in vitro study investigated the efficacy of a new pathogen-reduced cryoprecipitate thawed and stored at room temperature for 5 days (PR Cryo) to treat dilutional hypofibrinogenemia, compared to immediately thawed standard cryoprecipitate (Cryo) or fibrinogen concentrate (FC).

Study Design And Methods: Ten phlebotomy specimens from healthy volunteers were diluted 1:1 with crystalloid and supplemented with PR Cryo and Cryo (at a dose replicating transfusion of two pooled doses [10 units]) and FC at a dose replicating 50 mg/kg. Changes in clot firmness (thromboelastometry) and in coagulation factor activity were assessed at baseline, after dilution, and after supplementation.

Results: Clinical dosing was used, as described above, and consequently the FC dose contained 24% and 36% more fibrinogen versus PR Cryo and Cryo, respectively. At baseline, subjects had a median FIBTEM maximum clot firmness of 13.5 mm, versus 6.5 mm after 50% dilution (p = 0.005). After supplementation with PR Cryo, a median FIBTEM maximum clot firmness of 13 mm was observed versus 9.0 mm for Cryo (p = 0.005) or 16.5 mm for FC (p = 0.005). Median factor XIII was higher after PR Cryo (64.8%) versus Cryo (48.3%) (p = 0.005). Fibrinogen activity was higher after FC (269.0 mg/dL) versus PR Cryo (187.0 mg/dL; p = 0.005) or Cryo (193.5 mg/dL; p = 0.005); the difference between PR Cryo and Cryo supplementation (p = 0.445) was not significant.

Conclusion: PR Cryo used 5 days after thawing effectively restores clot strength after in vitro dilution.
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http://dx.doi.org/10.1111/trf.15157DOI Listing
May 2019

Comparison of the efficacy of two human fibrinogen concentrates to treat dilutional coagulopathy in vitro.

Scand J Clin Lab Invest 2018 05 15;78(3):230-235. Epub 2018 Feb 15.

c Centre for Perioperative Thrombosis and Haemostasis , Zurich , Switzerland.

Both congenital and acquired fibrinogen deficiency can be safely treated with administration of fibrinogen concentrate. The aim of this study was to test the efficacy of a new fibrinogen product (Fibryga) compared to a licensed product (Haemocomplettan) in an in vitro model of dilutional coagulopathy. Ten blood specimens from healthy volunteers were diluted 1:1 with balanced crystalloid solution and subsequently supplemented with each fibrinogen concentrate at a dose replicating in vivo supplementation (50 mg kg). Changes in clot firmness (FIBTEM and EXTEM assay), as well as changes in the fibrinogen antigen level, fibrinogen activity, factor XIII level and fibronectin levels were assessed at baseline, after dilution and after adding fibrinogen concentrate. There was no significant difference between the drugs in their in vitro ability to improve clot firmness in the FIBTEM assay (Fibryga: mean MCF 14.4 mm (SD 3.4 mm) vs. Haemocomplettan: MCF 14.1 mm (2.4); p = .584). Fibryga led to significantly higher clot firmness in EXTEM MCF: 56.7 mm (3.8) vs. 53.7 mm (3.7); p < .001). Distinct differences between FXIII levels (significantly higher in Fibryga; mean 40.9% (6.2%) vs. 31.0% (6.2%); p < .001) and fibronectin levels (significantly higher in Haemocomplettan; mean 0.008 g L (SD 0.002 g L) vs. 0.002 g L (SD 0.002 g L; p < .001) were observed between products. This is the first study to demonstrate that Fibryga and Haemocomplettan have similar efficacy in improving clot firmness in a dilutional hypofibrinogenemia model in vitro.
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http://dx.doi.org/10.1080/00365513.2018.1437645DOI Listing
May 2018

Influence of cryoprecipitate, Factor XIII, and fibrinogen concentrate on hyperfibrinolysis.

Transfusion 2017 10 21;57(10):2502-2510. Epub 2017 Jul 21.

Department of Anesthesia, Zurich University Children's Hospital, Zurich, Switzerland.

Background: Hyperfibrinolysis is a potentially life-threatening condition associated with poor clot integrity and excessive bleeding. Although antifibrinolytics are an effective treatment, more liberal use of these drugs may lead to a prothrombotic risk, and an earlier and potentially safer treatment option would be desirable. Hyperfibrinolysis has been shown to be attenuated by in vitro supplementation of purified human Factor (F)XIII concentrate. Cryoprecipitate represents an alternative source of FXIII and the only approved source of concentrated FXIII in some countries. The aim of this study was to investigate whether cryoprecipitate, FXIII, and fibrinogen concentrate mitigate hyperfibrinolysis.

Study Design And Methods: Ten citrate blood specimens from healthy subjects were spiked with tissue plasminogen activator (t-PA) and subsequently supplemented with cryoprecipitate, FXIII, fibrinogen concentrate, and ɛ-aminocaproic acid (EACA). Thromboelastometry tests were performed at baseline, after t-PA, and after supplementation. Hyperfibrinolysis was assessed using the clot lysis index at 60 minutes (LI60; reciprocal of maximum lysis).

Results: The LI60 was significantly improved (fibrinolysis attenuated) after cryoprecipitate supplementation compared to t-PA alone and compared to FXIII and fibrinogen concentrate. Hyperfibrinolysis was only fully reversed using EACA. In addition, cryoprecipitate demonstrated the least variability in the attenuation of hyperfibrinolysis among 10 healthy subjects, compared to FXIII and fibrinogen concentrate.

Conclusion: This is the first study to show that cryoprecipitate is able to significantly mitigate hyperfibrinolysis in an in vitro model. Further investigations are warranted to determine whether cryoprecipitate may have a previously unrecognized benefit and should be administered earlier in resuscitation protocols.
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http://dx.doi.org/10.1111/trf.14259DOI Listing
October 2017

Impact of rivaroxaban on point-of-care assays.

Thromb Res 2017 May 21;153:65-70. Epub 2017 Mar 21.

Department of Haematology, Inselspital, Bern University Hospital, Department of Clinical Research, University of Bern, CH-3010 Berne, Switzerland; Department of Clinical Research, University of Berne, CH-3000 Berne, Switzerland. Electronic address:

Background: Point-of-care testing (POCT) is regularly used to assess haemostasis in various clinical settings. The impact of rivaroxaban on those POCT is still elusive. We aimed to study the effects of rivaroxaban on most commonly used POCT assays.

Methods: Blood samples were taken before, 3h, and 24h after administration of 20mg rivaroxaban to 20 healthy volunteers as part of a prospective, multicenter validation study (clinicaltrials.govNCT01710267). Blood samples were analysed with thromboelastometry (ROTEM®), two platelet function assays (INNOVANCE® PFA-200 and Multiplate®), and the CoaguChek® XS. Rivaroxaban plasma levels were determined using liquid chromatography-mass spectrometry.

Results: Rivaroxaban significantly modified some thromboelastometry parameters (CT INTEM: mean difference 56.1s, 95% CI: 41.8, 70.3; CT EXTEM: 47.5s, 95% CI: 37.8, 57.1; CT HEPTEM: 50.1s, 95% CI: 34.7, 65.6), and CoaguChek® XS parameters (prothrombin time: mean difference 3.8s, 95% CI: 3.3, 4.2; INR: 0.32, 95% CI: 0.27, 0.38; prothrombin ratio: -36.1%, 95% CI: -32.3, -39.9). CT EXTEM and INR showed a moderate correlation with rivaroxaban plasma levels (r=0.83; 95% CI 0.69, 0.9 and r=0.83; 95% CI 0.70, 0.91, respectively) and a high sensitivity to detect rivaroxaban treatment at peak levels (0.95; 95% CI: 0.76, 1.0 and 0.90, 95% CI 0.70, 0.99, respectively).

Conclusions: Rivaroxaban 20mg treatment significantly alters ROTEM® and CoaguChek® XS parameters. Even though POCT do not allow precise quantification of rivaroxaban plasma concentration, CT EXTEM and CoaguChek XS detect the presence of rivaroxaban at peak level with a high sensitivity.
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http://dx.doi.org/10.1016/j.thromres.2017.03.019DOI Listing
May 2017

Is viscoelastic coagulation monitoring with ROTEM or TEG validated?

Scand J Clin Lab Invest 2016 Oct 29;76(6):503-7. Epub 2016 Jun 29.

c Institute of Anesthesiology, University and University Hospital of Zurich , Zurich , Switzerland.

Recent years have seen increasing worldwide interest in the use of viscoelastic coagulation monitoring tests, performed using devices such as ROTEM and TEG. The use of such tests to guide haemostatic therapy may help reduce transfusion of allogeneic blood products in bleeding patients and is supported in European guidelines for managing trauma and severe perioperative bleeding. In addition, viscoelastic tests form the basis of numerous published treatment algorithms. However, some publications have stated that viscoelastic tests are not validated. A specific definition of the term validation is lacking and regulatory requirements of the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) have been fulfilled by ROTEM and TEG assays. Viscoelastic tests have been used in pivotal clinical trials, and they are approved for use in most of the world's countries. Provided that locally approved indications are adhered to, the regulatory framework for clinicians to use viscoelastic tests in routine clinical practice is in place.
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http://dx.doi.org/10.1080/00365513.2016.1200136DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5152534PMC
October 2016

Direct oral anticoagulants (DOACs) versus "new" oral anticoagulants (NOACs)?

Authors:
Lars M Asmis

Semin Hematol 2014 Apr 21;51(2):87-8. Epub 2014 Mar 21.

Unilabs Coagulation Laboratory and Center for Perioperative Thrombosis and Hemostasis Zurich, Switzerland. Electronic address:

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http://dx.doi.org/10.1053/j.seminhematol.2014.03.003DOI Listing
April 2014

A brief review of 50 years of perioperative thrombosis and hemostasis management.

Semin Hematol 2013 Apr 11;50(2):79-87. Epub 2013 Jun 11.

Blood Transfusion Department, Areteion Hospital, Athens University Medical School, Athens, Greece.

Perioperative thrombosis and hemostasis management has changed dramatically over the past 50 years. From two anticoagulants and one anti-aggregant, the number of currently available drugs has recently increased several-fold, leaving clinicians with the problem of choosing the optimal agent. Individualized preoperative assessment of bleeding risk based on bleeding history and testing limited to high-risk patients is an emerging concept. Based on the identification of risk factors for venous thromboembolism (VTE), pharmacologic and non-pharmacologic strategies for perioperative VTE prophylaxis have had a major impact on patient outcome. For patients undergoing surgery who are treated with anticoagulants and anti-aggregants, "bridging" strategies have been proposed. Bleeding management strategies have shifted focus from replacing lost blood volume to new approaches aimed at preventing blood loss, reducing the potential complications of blood loss, and preventing the transfusion of blood products. For some areas of perioperative thrombosis and hemostasis management, randomized controlled trial (RCT) data are emerging, but the database remains insufficient to date. Clearly, more RCTs need to be published for perioperative thrombosis and hemostasis management to become an evidence-based approach.
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http://dx.doi.org/10.1053/j.seminhematol.2013.04.001DOI Listing
April 2013

FIBTEM PLUS provides an improved thromboelastometry test for measurement of fibrin-based clot quality in cardiac surgery patients.

Anesth Analg 2013 Nov;117(5):1054-62

From the *Department of Anesthesiology and Intensive Care, Salzburger Landeskliniken SALK, Salzburg, Austria; †CSL Behring, Marburg, Germany; ‡Department of Cardiothoracic and Vascular Anesthesia and Intensive Care, IRCCS Policlinico San Donato, Milan, Italy; §Haemostasis Research, Ludwig Boltzmann Institute for Experimental and Clinical Traumatology and AUVA Research Centre, Vienna, Austria; ‖Department of Anesthesiology and Intensive Care, AUVA Trauma Hospital of Salzburg, Salzburg, Austria; and ¶Laboratory Medicine, Unilabs Coagulation Laboratory, Zurich, Switzerland.

Background: The viscoelastic functional fibrinogen (FF) and FIBTEM assays measure the contribution of fibrin to clot strength. Inhibition of platelet function is a necessary precondition for these tests to work. We investigated a novel test for measuring fibrin-based clotting, FIBTEM PLUS, in cardiac surgery and compared it with FF and FIBTEM.

Methods: A prospective, observational study was performed which included 30 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Blood samples were drawn at the beginning of surgery (pre-CPB), approximately 20 minutes before weaning from CPB and 5 minutes after heparin neutralization. FF, FIBTEM, and FIBTEM PLUS tests were performed in duplicate for all blood samples. Additional coagulation parameters, including platelet count, plasma fibrinogen levels, factor XIII activity, and heparin concentration, were also recorded for each sample.

Results: At all time points, the lowest mean maximum clot firmness (MCF) was observed with FIBTEM PLUS, although a statistically significant difference between FIBTEM and FIBTEM PLUS was observed only at baseline (mean values 22 vs 19 mm, P = 0.01; FF value for comparison: 27.7 mm). FF maximum amplitude (MA) values were significantly higher than FIBTEM MCF and FIBTEM PLUS MCF pre-CPB, during CPB and after heparin neutralization (P ≤ 0.001 for FF MA versus FIBTEM MCF and for FF MA versus FIBTEM PLUS MCF at all time points). The difference between FIBTEM MCF and FIBTEM PLUS MCF correlated with platelet count (r = 0.46;P < 0.001), whereas differences between FF MA and FIBTEM MCF, or FF MA and FIBTEM PLUS MCF did not (r = -0.07, P = 0.51; r = 0.16, P = 0.12, respectively). Differences between the assays were unrelated to heparin levels, which decreased considerably after protamine administration compared with heparin levels recorded before weaning from CPB (decrease from 2.1 to 0.1 U/mL and from 2.8 to 0.2 U/mL for anti-factor IIa and anti-factor Xa, respectively). Agreement between duplicate measurements was similar with FIBTEM and FIBTEM PLUS assays and lower with FF. Significant positive correlations were found between MCF or MA and fibrinogen concentration (all P < 0.001); the highest correlation was with FIBTEM PLUS MCF (r = 0.70).

Conclusion: The FIBTEM PLUS assay produces precise results. At baseline, it provides greater inhibition of platelets than FIBTEM, but there is no meaningful difference between FIBTEM PLUS and FIBTEM in patients with low platelet counts.
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http://dx.doi.org/10.1213/ANE.0b013e3182a1afacDOI Listing
November 2013

Variability between laboratories performing coagulation tests with identical platforms: a nationwide evaluation study.

Thromb J 2013 Mar 7;11(1). Epub 2013 Mar 7.

Division of Hematology and Central Hematology Laboratory, Luzerner Kantonsspital, Lucerne 16 CH-6000, Switzerland.

Background: While the assessment of analytical precision within medical laboratories has received much attention in scientific enquiry, the degree of as well as the sources causing variation between them remains incompletely understood. In this study, we quantified the variance components when performing coagulation tests with identical analytical platforms in different laboratories and computed intraclass correlations coefficients (ICC) for each coagulation test.

Methods: Data from eight laboratories measuring fibrinogen twice in twenty healthy subjects with one out of 3 different platforms and single measurements of prothrombin time (PT), and coagulation factors II, V, VII, VIII, IX, X, XI and XIII were analysed. By platform, the variance components of (i) the subjects, (ii) the laboratory and the technician and (iii) the total variance were obtained for fibrinogen as well as (i) and (iii) for the remaining factors using ANOVA.

Results: The variability for fibrinogen measurements within a laboratory ranged from 0.02 to 0.04, the variability between laboratories ranged from 0.006 to 0.097. The ICC for fibrinogen ranged from 0.37 to 0.66 and from 0.19 to 0.80 for PT between the platforms. For the remaining factors the ICC's ranged from 0.04 (FII) to 0.93 (FVIII).

Conclusions: Variance components that could be attributed to technicians or laboratory procedures were substantial, led to disappointingly low intraclass correlation coefficients for several factors and were pronounced for some of the platforms. Our findings call for sustained efforts to raise the level of standardization of structures and procedures involved in the quantification of coagulation factors.
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http://dx.doi.org/10.1186/1477-9560-11-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3599351PMC
March 2013

Perioperative diclofenac application during video-assisted thoracic surgery pleurodesis modulates early inflammatory and fibrinolytic processes in an experimental model.

Eur Surg Res 2013 15;50(1):14-23. Epub 2013 Feb 15.

Division of Thoracic Surgery, University Hospital Zürich, Zürich, Switzerland.

Background/purpose: It has been substantiated that the quality of pleurodesis is reduced when non-steroidal anti-inflammatory drugs (NSAIDs) are used perioperatively. The effects of NSAID administration on the early inflammatory and fibrinolytic processes after mechanical pleurodesis were investigated in an established pig model.

Methods: Left-sided mechanical pleural abrasion was performed on 24 pigs assigned to either an NSAID or a control group. Pleural fluid and blood samples were analysed over a 24-hour period. Histological evaluation of neutrophil influx at the site of pleural abrasion was performed.

Results: The volume of pleural effusion was significantly decreased in the diclofenac group at 10 and 24 h, and the protein content was significantly lower. The diclofenac group at 24 h had a diminished total number of white blood cells and a reduced content of transforming growth factor-β. Moreover, the diclofenac group had a reduced percentage of neutrophils at 6 h. Significantly increased levels of D-dimers and tissue plasminogen activator were measured at 6 h and of interleukin-10 at 24 h. Neutrophils at the site of pleural abrasion were significantly reduced.

Conclusions: Systemic application of diclofenac led to a local enhancement of fibrinolysis and attenuation of pro-inflammatory and fibrotic processes necessary for adhesion formation in our model.
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http://dx.doi.org/10.1159/000341670DOI Listing
February 2014

[The new Anticoagulants - Relevant Facts for the GP].

Authors:
Lars M Asmis

Praxis (Bern 1994) 2011 Aug;100(16):971-6

Unilabs Gerinnungslabor Zürich und Zentrum für perioperative Thrombose und Hämostase, Zürich.

Goal of this article is to select three molecules from all the candidates currently under clincial development and to present and comapre their characteristics. Dabigatran is a direct thrombin (FIIa) inhibitor, whereas Rivaroxaban and Apixaban are direct factor Xa (FXa) inhibitors. All three represent small molecules thatreversibly, rapidly and directly bind to their target, the active center of the respective activated coagulation factor. Phase III data have been published for venous thromboembolism prophylaxis for each of these three drugs. Interestingly, VTE prophylaxis is initiated postoperatively with these products. Rivaroxaban currently holds the only accepted indication in Switzerland. For the indications VTE, atrial fibrillation and acute coronary syndrome promising phase III data have been or are in the process of being published. Monitoring is not necessary for any of these three new anticoagulants.
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http://dx.doi.org/10.1024/1661-8157/a000627DOI Listing
August 2011

Immunomodulatory drugs increase endothelial tissue factor expression in vitro.

Thromb Res 2011 Mar 14;127(3):264-71. Epub 2010 Dec 14.

Division of Hematology, University Hospital of Zurich, CH 8091 Zurich, Switzerland.

Introduction: Immunomodulatory compounds such as thalidomide (THL) and lenalidomide (LEN) represent treatment options for multiple myeloma. Venous thromboembolism is a potential complication of immunomodulatory treatment in myeloma patients. The optimal thromboprophylactic strategy to prevent this drug-induced hypercoagulable state is debated. It is the aim of this study to investigate i) the effect of immunomodulatory treatment on endothelial cell tissue factor (TF) expression and function, ii) the regulation of the observed TF activity, and iii) the modulating effect of low molecular weight heparin and aspirin on TF activity in vitro.

Materials And Methods: These aims were addressed in an in vitro culture model, human umbilical vein endothelial cells, using TF activity and antigen assays as well flow cytometry, real time PCR and electron microscopy.

Results: At THL and LEN concentrations resembling those observed in myeloma patients in vivo and in the presence of tumor necrosis factor-α (TNFα) we observed significantly increased TF activity in human umbilical vein endothelial cells in vitro. Concordant changes were detected for tissue factor mRNA and TF whole cell antigen. Dalteparin and a mixture of monoclonal anti-TF antibodies inhibited TF activity by 100% and more than 80% respectively, while aspirin's inhibitory effect was only approximately 30%. In the presence of TNFα we detected the generation of endothelial cell-derived microparticles which expressed TF activity.

Conclusions: Our in vitro data support the hypothesis that THL and LEN induce a hypercoagulable state through increased endothelial TF expression.
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http://dx.doi.org/10.1016/j.thromres.2010.11.018DOI Listing
March 2011

In vitro factor XIII supplementation increases clot firmness in Rotation Thromboelastometry (ROTEM).

Thromb Haemost 2010 Aug 29;104(2):385-91. Epub 2010 Apr 29.

Institute of Anesthesiology, University Hospital Zurich, Zurich, Switzerland.

Factor XIII (F XIII) is an essential parameter for final clot stability. The purpose of this study was to determine the impact of the addition of factor (F)XIII on clot stability as assessed by Rotation Thromboelastometry (ROTEM). In 90 intensive care patients ROTEM measurements were performed after in vitro addition of F XIII 0.32 IU, 0.63 IU, 1.25 IU and compared to diluent controls (DC; aqua injectabile) resulting in approximate F XIII concentrations of 150, 300 and 600%. Baseline measurements without any additions were also performed. The following ROTEM parameters were measured in FIBTEM and EXTEM tests: clotting time (CT), clot formation time (CFT), maximum clot firmness (MCF), maximum lysis (ML), maximum clot elasticity (MCE) and alpha-angle (alphaA). Additionally, laboratory values for FXIII, fibrinogen (FBG), platelets and haematocrit were contemporaneously determined. In the perioperative patient population mean FBG concentration was elevated at 5.2 g/l and mean FXIII concentration was low at 62%. The addition of FXIII led to a FBG concentration-dependent increase in MCF both in FIBTEM and EXTEM. Mean increases in MCF (FXIII vs. DC) of approximately 7 mm and 6 mm were observed in FIBTEM and EXTEM, respectively. F XIII addition also led to decreased CFT, increased alphaA, and reduced ML in FIBTEM and EXTEM. In vitro supplementation of FXIII to supraphysiologic levels increases maximum clot firmness, accelerates clot formation and increases clot stability in EXTEM and FIBTEM as assayed by ROTEM in perioperative patients with high fibrinogen and low FXIII levels.
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http://dx.doi.org/10.1160/TH09-12-0858DOI Listing
August 2010

Hypercoagulability in the perioperative period.

Best Pract Res Clin Anaesthesiol 2010 Mar;24(1):133-44

Drexel University College of Medicine, Department of Anesthesiology, Philadelphia, Pennsylvania 19102, USA.

One of the greatest disappointments associated with a successful surgical procedure is a thrombotic or thrombo-embolic complication in the postoperative period. Morbidity and mortality of the perioperative period are related, to a relevant degree, to perioperative thrombo-embolic events. Ranging from simple deep venous thrombosis to pulmonary embolism or arterial thrombosis, this class of complication invariably increases length of hospital stay or may result in mortality. The purpose of this review is to identify the procedures and patient populations noted to have thrombophilia in the postoperative period, link the changes in circulating and in situ haematological/biochemical substrates most likely responsible for morbidity, identify the clinical diagnostic modalities that detect recent/impending thrombosis and, lastly, consider the rational therapeutic approaches recommended for minimising postoperative thrombotic complications.
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http://dx.doi.org/10.1016/j.bpa.2009.09.012DOI Listing
March 2010

Two different hematocrit detection methods: different methods, different results?

BMC Res Notes 2010 Mar 9;3:65. Epub 2010 Mar 9.

Surgical Intensive Care Medicine, University Hospital of Zurich, CH 8091 Zurich, Switzerland.

Background: Less is known about the influence of hematocrit detection methodology on transfusion triggers. Therefore, the aim of the present study was to compare two different hematocrit-assessing methods. In a total of 50 critically ill patients hematocrit was analyzed using (1) blood gas analyzer (ABLflex 800) and (2) the central laboratory method (ADVIA® 2120) and compared.

Findings: Bland-Altman analysis for repeated measurements showed a good correlation with a bias of +1.39% and 2 SD of +/- 3.12%. The 24%-hematocrit-group showed a correlation of r2 = 0.87. With a kappa of 0.56, 22.7% of the cases would have been transfused differently. In the-28%-hematocrit group with a similar correlation (r2 = 0.8) and a kappa of 0.58, 21% of the cases would have been transfused differently.

Conclusions: Despite a good agreement between the two methods used to determine hematocrit in clinical routine, the calculated difference of 1.4% might substantially influence transfusion triggers depending on the employed method.
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http://dx.doi.org/10.1186/1756-0500-3-65DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845149PMC
March 2010

Rotation thromboelastometry (ROTEM) stability and reproducibility over time.

Eur J Cardiothorac Surg 2010 Mar 10;37(3):677-83. Epub 2009 Sep 10.

Institute of Anesthesiology, University Hospital Zurich, CH - 8091 Zurich, Switzerland.

Background: Thromboelastometry is a whole blood assay performed to evaluate the viscoelastic properties during blood clot formation and lysis. Rotation thromboelastography (ROTEM), Pentapharm GmbH, Munich, Germany) has overcome some of the limitations of classic thromboelastography. So far, no clinical validation on reproducibility (inter- and intra-assay variability) and sample stability over time has been published.

Methods: To evaluate the pre-analytic aspects, sample stability over time was assessed in 48 patients in eight age groups. Citrated blood was stored at room temperature. Tests measured every 30 min from T 0 min up to T 120 min on two ROTEM devices were INTEM (ellagic acid activated intrinsic pathway), EXTEM (tissue factor-triggered extrinsic pathway) and FIBTEM (with platelet inhibitor (cytochalasin D) evaluating the contribution of fibrinogen to clot formation). Precision by intra- and inter-assay variability was evaluated at two points of time in 10 volunteers. Finally, reference intervals and effect of age and sex were evaluated.

Results: Blood was stable over 120 min and no significant differences in ROTEM results were found. Maximum clot firmness measurements had a coefficient of variation of <3% for EXTEM, <5% for INTEM and <6% for FIBTEM. For clot formation time, the coefficient of variation was <4% for EXTEM and <3% for INTEM. Coefficient of variation for angle alpha was <3% for EXTEM and <6% for INTEM. The coefficient of variation for clotting time was <15% for both EXTEM and INTEM. Small but significant differences between ROTEM devices were found for maximum clot firmness in FIBTEM and INTEM as well as clot formation time and alpha angle in INTEM.

Conclusions: ROTEM yields stable results over 120 min with a minimal variability on the same ROTEM device. However, small but significant differences between ROTEM devices were observed. Analysis should be performed on the same ROTEM device if small differences are of importance for treatment.
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http://dx.doi.org/10.1016/j.ejcts.2009.07.038DOI Listing
March 2010

Kinetics of D-dimer after general surgery.

Blood Coagul Fibrinolysis 2009 Jul;20(5):347-52

Department of Surgery, University Hospital Zurich, Switzerland.

D-dimers may be elevated after surgery. However, the kinetics of postoperative D-dimers remains unknown hampering the use of D-dimer testing in surgical patients with suspected venous thromboembolism. D-dimer levels were prospectively measured in 154 patients after general surgery at predefined time points (kinetics were determined in an initial cohort of 108 patients; for validation, these findings were applied to a second cohort of 46 patients). Clinical factors influencing the peak of D-dimers were analyzed using multivariate regression. Surgical operations were stratified based on severity (type I: not entering abdominal cavity; type II: intraabdominal; type III: retroperitoneal/liver surgery). D-dimer levels increased postoperatively reaching a peak on day 7. After type I surgery, peak D-dimer levels did not exceed normal range (300 ng/ml, 100-500). After type II procedures, peak D-dimer level was 1500 ng/ml (200-7800) and returned to normal values after 25 days (+/-14). Peak level was 4000 ng/ml (500-14 400) after type III surgery normalizing within 38 days (+/-11). Clearance of D-dimer was exponential after having reached the peak with 6.0% per day (95% confidence interval 4.8-7.1%). By this clearance, D-dimer values could be adequately predicted in the validation cohort after day 7 (r2 = 0.63). Peak D-dimer levels were independently influenced by the type of surgery (P < 0.001), the operation time (P < 0.001) and by preoperatively elevated D-dimer levels (P < 0.001). Based on this data, duration of postoperative D-dimer elevation after abdominal surgery is predictable. This study indicates for the first time when D-dimers may be used again in the diagnostic algorithm for venous thromboembolism exclusion after surgery in patients with low or moderate clinical probability.
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http://dx.doi.org/10.1097/MBC.0b013e32832a5fe6DOI Listing
July 2009

Heparin-induced antibodies and cardiovascular risk in patients on dialysis.

Thromb Haemost 2008 Sep;100(3):498-504

Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.

The clinical relevance of heparin-induced antibodies (HIA) in the absence of thrombocytopenia remains to be defined. The aims of this study were (i) to determine the prevalence of HIA in patients treated by dialysis, (ii) to determine the prevalence of thrombocytopenia and heparin-induced thrombocytopenia (HIT), and (iii) to test whether HIA are associated with adverse outcomes. Sera from 740 patients treated by hemodialysis (HD, n=596) and peritoneal dialysis (PD, n=144) were tested for HIA (IgG, IgA or IgM) by masked investigators at approximately six months after enrolment in the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease (CHOICE) study. We assessed, with time-to-event Cox proportional hazards models, whether the presence of HIA predicted any of four clinical outcomes: arterial cardiovascular events, venous thromboembolism, vascular access occlusion and mortality. HIA prevalence was 10.3% overall. HIA positivity did not predict development of thrombocytopenia or any of the four clinical outcomes over a mean follow-up of 3.6 years, with hazard ratios for arterial cardiovascular events of 0.98 (95% confidence interval 0.70-1.37), venous thromboembolism 1.39 (0.17-11.5), vascular access occlusion 0.82 (0.40-1.71), and mortality 1.18 (0.85-1.64). Chronic intermittent heparin exposure was associated with a high seroprevalence of HIA. In dialysis patients these antibodies were not an independent risk factor for cardiovascular events and mortality. Our data do not suggest that dialysis patients should be monitored for HIA antibodies in the absence of thrombocytopenia.
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September 2008

Treatment of midgestational placental haemorrhage with recombinant factor VIIa.

Thromb Haemost 2008 Jul;100(1):154-5

Clinic of Obstetrics, Department of Obstetrics and Gynaecology, University Hospital Zurich, Frauenklinikstrasse 10, CH 8091 Zurich, Switzerland.

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http://dx.doi.org/10.1160/TH08-01-0048DOI Listing
July 2008

In vitro norepinephrine significantly activates isolated platelets from healthy volunteers and critically ill patients following severe traumatic brain injury.

Crit Care 2008 18;12(3):R80. Epub 2008 Jun 18.

Surgical Intensive Care Medicine, University Hospital Zuerich, Raemistrasse 100, CH 8091 Zuerich, Switzerland.

Introduction: Norepinephrine, regularly used to increase systemic arterial blood pressure and thus improve cerebral perfusion following severe traumatic brain injury (TBI), may activate platelets. This, in turn, could promote microthrombosis formation and induce additional brain damage.

Methods: The objective of this study was to investigate the influence of norepinephrine on platelets isolated from healthy volunteers and TBI patients during the first two post-traumatic weeks. A total of 18 female and 18 male healthy volunteers of different age groups were recruited, while 11 critically ill TBI patients admitted consecutively to our intensive care unit were studied. Arterial and jugular venous platelets were isolated from norepinephrine-receiving TBI patients; peripheral venous platelets were studied in healthy volunteers. Concentration-dependent functional alterations of isolated platelets were analyzed by flow cytometry, assessing changes in surface P-selectin expression and platelet-derived microparticles before and after in vitro stimulation with norepinephrine ranging from 10 nM to 100 microM. The thrombin receptor-activating peptide (TRAP) served as a positive control.

Results: During the first week following TBI, norepinephrine-mediated stimulation of isolated platelets was significantly reduced compared with volunteers (control). In the second week, the number of P-selectin- and microparticle-positive platelets was significantly decreased by 60% compared with the first week and compared with volunteers. This, however, was associated with a significantly increased susceptibility to norepinephrine-mediated stimulation, exceeding changes observed in volunteers and TBI patients during the first week. This pronounced norepinephrine-induced responsiveness coincided with increased arterio-jugular venous difference in platelets, reflecting intracerebral adherence and signs of cerebral deterioration reflected by elevated intracranial pressure and reduced jugular venous oxygen saturation.

Conclusion: Clinically infused norepinephrine might influence platelets, possibly promoting microthrombosis formation. In vitro stimulation revealed a concentration- and time-dependent differential level of norepinephrine-mediated platelet activation, possibly reflecting changes in receptor expression and function. Whether norepinephrine should be avoided in the second post-traumatic week and whether norepinephrine-stimulated platelets might induce additional brain damage warrant further investigations.
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http://dx.doi.org/10.1186/cc6931DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2481479PMC
September 2008

Contact system activation in human sepsis - 47kD HK, a marker of sepsis severity?

Swiss Med Wkly 2008 Mar;138(9-10):142-9

Division of Haematology and Central Haematology Laboratory, Inselspital, Berne, Switzerland.

Aim: This pilot study seeks to determine whether contact system activation (CSA) occurs in human sepsis patients and to characterise blood levels of the 47kD light chain of high-molecular weight kininogen (47kD HK).

Methods: Six consecutive patients with clinical suspicion of sepsis were evaluated on days 1, 2, 3 and 6-8 for 47kD HK blood levels expressed in U/ml of whole blood and as percent of total HK. 47kD HK was measured in whole blood by quantitative immunoblot analysis.

Results: On study day 1 or 2, analysis of 47kD HK in U/ml of whole blood identified CSA in 3/6 patients. When 47kD HK levels were expressed as percent of total HK, 4/6 patients were identified with CSA before day 3. The degree of CSA as assayed by the presence of 47kD HK correlated with the severity of the systemic inflammatory syndrome (SIRS), i.e. mean CSA increased progressively from basal levels in healthy controls (0.08 U/ml or 10.4%) to patients without SIRS (0.10 U/ml or 15.1%), to patients with sepsis (0.12 U/ml or 15.0%), and finally to patients in a combined category of severe sepsis and septic shock (0.13 U/ml or 17.4%).

Conclusion: CSA, defined by increased 47kD HK, occurred early on in the course of sepsis in a subset of sepsis patients. 47kD HK levels, an indicator of bradykinin release, correlated with sepsis severity. Future larger studies will need to evaluate the role of 47kD HK as a biomarker for both prognosis and treatment response in human sepsis..
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http://dx.doi.org/2008/09/smw-11788DOI Listing
March 2008

[Mechanism of action of old and new anticoagulants].

Herz 2008 Feb;33(1):4-12

Kardiovaskuläre Forschung, Physiologisches Institut, Universität Zürich, Schweiz.

Atrial fibrillation, venous thromboembolism, and valvular heart disease are the most common indications for treatment with anticoagulants. Regarding the high incidence of these diseases, it can be assumed that about 1% of the population takes oral anticoagulants. Approximately one third of the patients hospitalized in a surgical clinic receive vitamin K antagonists. Hence, general practitioners and specialists in hospitals as well as in private practice are constantly faced with different options of anticoagulatory treatment. In numerous situations, inhibitors of coagulation exhibit a substantial benefit. However, this is only achieved by accepting an increased risk of bleeding. To walk the tightrope between too much and insufficient anticoagulatory action is an important challenge in clinical practice. Knowledge of the mechanisms underlying pharmacological anticoagulation is crucial in order to evaluate the indications for and efficiently manage anticoagulant therapy. Ideally, the aim of an adequate anticoagulation should be to guarantee sufficient hemostasis in combination with simultaneous prevention of thrombus formation. This article intends to provide an overview of the coagulation system and established as well as novel pharmacological targets.
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http://dx.doi.org/10.1007/s00059-008-3065-9DOI Listing
February 2008

Engineered living blood vessels: functional endothelia generated from human umbilical cord-derived progenitors.

Ann Thorac Surg 2006 Oct;82(4):1465-71; discussion 1471

Clinic for Cardiovascular Surgery, University Hospital Zurich, Switzerland.

Background: Tissue-engineered living blood vessels (TEBV) with growth capacity represent a promising new option for the repair of congenital malformations. We investigate the functionality of TEBV with endothelia generated from human umbilical cord blood-derived endothelial progenitor cells.

Methods: Tissue-engineered living blood vessels were generated from human umbilical cord-derived myofibroblasts seeded on biodegradable vascular scaffolds, followed by endothelialization with differentiated cord blood-derived endothelial progenitor cells. During in vitro maturation the TEBV were exposed to physiologic conditioning in a flow bioreactor. For functional assessment, a subgroup of TEBV was stimulated with tumor necrosis factor-alpha. Control vessels endothelialized with standard vascular endothelial cells were treated in parallel. Analysis of the TEBV included histology, immunohistochemistry, biochemistry (extracellular matrix analysis, DNA), and biomechanical testing. Endothelia were analyzed by flow cytometry and immunohistochemistry (CD31, von Willebrand factor, thrombomodulin, tissue factor, endothelial nitric oxide synthase).

Results: Histologically, a three-layered tissue organization of the TEBV analogous to native vessels was observed, and biochemistry revealed the major matrix constituents (collagen, proteoglycans) of blood vessels. Biomechanical properties (Young's modulus, 2.03 +/- 0.65 MPa) showed profiles resembling those of native tissue. Endothelial progenitor cells expressed typical endothelial cell markers CD31, von Willebrand factor, and endothelial nitric oxide synthase comparable to standard vascular endothelial cells. Stimulation with tumor necrosis factor-alpha resulted in physiologic upregulation of tissue factor and downregulation of thrombomodulin expression.

Conclusions: These results indicate that TEBV with tissue architecture and functional endothelia similar to native blood vessels can be successfully generated from human umbilical cord progenitor cells. Thus, blood-derived progenitor cells obtained before or at birth may enable the clinical realization of tissue engineering constructs for pediatric applications.
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http://dx.doi.org/10.1016/j.athoracsur.2006.05.066DOI Listing
October 2006

Molecular mechanism of glutathione-mediated protection from oxidized low-density lipoprotein-induced cell injury in human macrophages: role of glutathione reductase and glutaredoxin.

Free Radic Biol Med 2006 Sep 3;41(5):775-85. Epub 2006 Jun 3.

Graduate Center for Nutritional Sciences, University of Kentucky, Lexington, KY 40506, USA.

Macrophage death is a hallmark of advanced atherosclerotic plaque, and oxidized low-density lipoprotein (OxLDL) found in these lesions is believed to contribute to macrophage injury. However, the underlying mechanisms of this phenomenon are only poorly understood. Here we show that in human monocyte-derived macrophages, OxLDL depleted intracellular glutathione (GSH) and inhibited glutathione reductase, resulting in a marked diminution of the glutathione/glutathione disulfide ratio. In the absence of OxLDL, an 80% depletion of intracellular GSH levels did not affect cell viability, but glutathione depletion dramatically increased OxLDL-induced cell death. Conversely, supplementation of intracellular GSH stores with glutathione diethyl ester substantially diminished OxLDL toxicity. OxLDL also promoted protein-S-glutathionylation, which was increased in macrophages pretreated with the glutathione reductase inhibitor BCNU. Knockdown experiments with siRNA directed against glutathione reductase and glutaredoxin showed that both enzymes are essential for the protection of macrophages against OxLDL. Finally, the peroxyl-radical scavenger Trolox did not prevent GSH depletion but completely blocked OxLDL-induced protein-S-glutathionylation and cell death. These data suggest that OxLDL promotes ROS formation and protein-S-glutathionylation by a mechanism independent from its effect on GSH depletion. Neither mechanism was sufficient to induce macrophage injury, but when stimulated concurrently, these pathways promoted the accumulation of protein-glutathione mixed disulfides and cell death.
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http://dx.doi.org/10.1016/j.freeradbiomed.2006.05.029DOI Listing
September 2006

Adriamycin promotes macrophage dysfunction in mice.

Free Radic Biol Med 2006 Jul 18;41(1):165-74. Epub 2006 Apr 18.

Division of Nephrology, University of Texas Health Science Center at San Antonio and South Texas Veterans Health Care System, 7703 Floyd Curl Drive, MSC 7882, San Antonio, TX 78229, USA.

Impaired wound healing contributes to the morbidity and mortality associated with adriamycin chemotherapy. Macrophages are essential for tissue repair and loss of macrophage function leads to impaired wound healing. We recently showed that adriamycin is a potent inducer of thiol oxidation and cell injury in cultured macrophages (FASEB J. 19:1866-1868; 2005). Here we tested the hypothesis that adriamycin also promotes oxidative stress and macrophage dysfunction in vivo. We treated FVB mice twice a week either with low doses of adriamycin (4 mg/kg) or with the same volume of saline by tail vein injection for a total of 8 injections. Wound healing was significantly delayed in adriamycin-treated mice. The number of resident peritoneal macrophages was decreased by 30% and macrophage recruitment in response to thiogycolate stimulation was decreased by 46% in mice treated with adriamycin. LPS-induced TNFalpha and IL-1beta secretion from macrophages of adriamycin-treated mice was decreased by 28.7 and 29.5%, respectively, compared to macrophages isolated from saline-injected mice. Peritoneal macrophages isolated from adriamycin-treated mice also showed increased formation of reactive oxygen species and enhanced protein-S-glutathionylation. In summary, our results show that low cumulative doses of adriamycin are sufficient both to promote sustained thiol oxidative stress and macrophage dysfunction in vivo and to delay tissue repair, suggesting that macrophage dysfunction contributes to impaired wound healing associated with adriamycin chemotherapy.
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http://dx.doi.org/10.1016/j.freeradbiomed.2006.03.027DOI Listing
July 2006
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