Anaphylactic Reaction to Tranexamic Acid During Posterior Spinal Fusion: A Case Report.

CASE: We present a 20-year-old man who suffered anaphylactic shock during posterior spinal fusion for neuromuscular scoliosis with the offending agent later identified via intradermal testing to be tranexamic acid (TXA). CONCLUSION: TXA, although an increasingly common drug, can be the cause of sudden anaphylactic shock intraoperatively. This now represents the fifth reported case in the literature of patients ranging from 15 years to 80 years old with no previous exposure to the drug.

Anti-Xa assays: What is their role today in antithrombotic therapy?

Although some suggest anti-Xa assays should be the preferred method for monitoring intravenous unfractionated heparin therapy, which method is best is unknown owing to the lack of large randomized controlled trials correlating different assays with clinical outcomes. This article provides an overview of heparin monitoring and the pros, cons, and clinical applications of anti-Xa assays.

A novel Kunitz protein with proposed dual function from Eudiplozoon nipponicum (Monogenea) impairs haemostasis and action of complement in vitro.

Serine peptidases are involved in many physiological processes including digestion, haemostasis and complement cascade. Parasites regulate activities of host serine peptidases to their own benefit, employing various inhibitors, many of which belong to the Kunitz-type protein family. In this study, we confirmed the presence of potential anticoagulants in protein extracts of the haematophagous monogenean Eudiplozoon nipponicum which parasitizes the common carp. We then focused on a Kunitz protein (EnKT1) discovered in the E. nipponicum transcriptome, which structurally resembles textilinin-1, an antihemorrhagic snake venom factor from Pseudonaja textilis. The protein was recombinantly expressed, purified and biochemically characterised. The recombinant EnKT1 did inhibit in vitro activity of Factor Xa of the coagulation cascade, but exhibited a higher activity against plasmin and plasma kallikrein, which participate in fibrinolysis, production of kinins, and complement activation. Anti-coagulation properties of EnKT1 based on the inhibition of Factor Xa were confirmed by thromboelastography, but no effect on fibrinolysis was observed. Moreover, we discovered that EnKT1 significantly impairs the function of fish complement, possibly by inhibiting plasmin or Factor Xa which can act as a C3 and C5 convertase. We localised Enkt1 transcripts and protein within haematin digestive cells of the parasite by RNA in situ hybridisation and immunohistochemistry, respectively. Based on these results, we suggest that the secretory Kunitz protein of E. nipponicum has a dual function. In particular, it impairs both haemostasis and complement activation in vitro, and thus might facilitate digestion of a host's blood and protect a parasite's gastrodermis from damage by the complement. This study presents, to our knowledge, the first characterisation of a Kunitz protein from monogeneans and the first example of a parasite Kunitz inhibitor that impairs the function of the complement.

Discovery of novel mechanisms and molecular targets for the inhibition of activated thrombin activatable fibrinolysis inhibitor.

BACKGROUND: Thrombin activatable fibrinolysis inhibitor (TAFI) is an important regulator of fibrinolysis and an attractive target to develop profibrinolytic drugs. OBJECTIVE: To analyze the (inhibitory) properties of five monoclonal antibodies (mAbs) directed towards rat TAFI (i.e. MA-RT13B2, MA-RT30D8, MA-RT36A3F5, MA-RT36B2 and MA-RT82F12). METHODS AND RESULTS: Direct interference of the mAb with rat activated TAFI (TAFIa) activity was assayed using a chromogenic activity assay. This revealed reductions of 79% +/- 1%, 54% +/- 4%, and 19% +/- 2% in activity in the presence of a 16-fold molar excess of MA-RT13B2, MA-RT36A3F5, and MA-RT82F12, respectively whereas MA-RT30D8 and MA-RT36B2 had no direct inhibitory effect. Additionally, MA-RT13B2 and MA-RT36A3F5 reduced rat TAFIa half-life by 56% +/- 2% and 61% +/- 3%. Tissue-type plasminogen activator mediated in vitro clot lysis was determined using rat plasma. Compared to potato tuber carboxypeptidase inhibitor, MA-RT13B2, MA-RT30D8, MA-RT36A3F5, and MA-RT82F12 reduced clot lysis times by 86% +/- 14%, 100% +/- 5%, 100% +/- 10%, and 100% +/- 11%, respectively. During epitope mapping, Arg(227) and Ser(251) were identified as major residues interacting with MA-RT13B2. Arg(188) and His(192) contribute to the interaction with MA-RT36A3F5. Arg(227), Ser(249), Ser(251), and Tyr(260) are involved in the binding of MA-RT30D8 and MA-RT82F12 with rat TAFI(a). The following mechanisms of inhibition have been deduced: MA-RT13B2 and MA-RT36A3F5 have a destabilizing effect on rat TAFIa whereas MA-RT30D8 and MA-RT82F12 partially block the access to the active site of TAFIa or interact with the binding of TAFIa to the blood clot. CONCLUSIONS: The described inhibitory mAb towards rat TAFIa will facilitate TAFI research in murine models. Additionally, we reveal novel molecular targets for the direct inhibition of TAFIa through different mechanisms.

Plasma TAFI antigen variations in healthy subjects.

The Thrombin Activatable Fibrinolysis Inhibitor (TAFI) is a recently described inhibitor of fibrinolysis. The physiological variations of plasma TAFI antigen are not well known. We studied TAFI antigen values in healthy populations with a commercially available kit from Milan Analytica (Switzerland). Broad range of TAFI antigen values (from 41% to 259%) was found in a population of 249 healthy individuals. Gender as well as pregnancy did not influence mean values of TAFI antigen. There was a positive correlation between TAFI antigen and age in female (r = 0.28; p <0.05) but not in male populations. Mean TAFI antigen value of a black African male group [mean +/- SD (range): 87 +/- 23 (39-144%)] was significantly lower than the one of age matched Caucasian men [114 +/- 34 (52-259%)] (p <0.0001). TAFI antigen values were very stable within individuals, they did not significantly vary on day time or at several months period. Thus, in contrast to large inter-individual variations, TAFI antigen levels are quite stable within individuals.

Increased D-dimer levels in twin gestation.

In normal pregnancy, the hemostatic balance is displaced toward hypercoagulability. The elevation in plasma levels of coagulation factors VII, VIII, and X and fibrinogen and the increased concentrations of plasminogen activator inhibitors [1,2] may predispose individuals to thromboembolism, especially near term [1,3]. Because human multifetal gestation requires still greater physiological alterations, the imbalance in hemostasis is further exaggerated. It has been suggested that the changes in the coagulation system near term may even mimic low-grade disseminated intravascular coagulopathy [4]. However, for the majority of women with multifetal gestation, the coagulopathy observed in the laboratory is not clinically apparent [5]. Despite the large body of research on the physiological adaptation to pregnancy, relatively little is known of the biological adaptation in general and the hemostatic changes in particular associated with multiple gestation.

Exclusion and diagnosis of pulmonary embolism by a rapid ELISA D-dimer test and noninvasive imaging techniques within the context of a clinical model.

A negative rapid ELISA D-dimer test alone in out-patients with a low to moderate clinical probability (CP) on pulmonary embolism (PE) is predicted to safely exclude pulmonary embolism. The combination of a negative rapid ELISA D-dimer test and a low to moderate CP on PE followed by compression ultrasonography (CUS) for the detection of deep vein thrombosis (DVT) is safe and cost-effective as it reduces the need for noninvasive imaging techniques to about 50% to 60% of outpatients with suspected PE. A high probability ventilation-perfusion (VP) scan or a positive spiral CT consistent with PE and the detection of DVT by CUS are currently considered to be clear indications for anticoagulant treatment. Subsequent pulmonary angiography (PA) is the gold standard diagnostic strategy to exclude or diagnose PE in suspected outpatients with a negative CUS, a positive rapid ELISA D-dimer test, and a nondiagnostic VP scan or negative spiral CT to prevent overtreatment with anticoagulants. However, the willingness of clinicians and the availability of resources to perform PA is restricted, a fact that has provided an impetus for clinical investigators to search for alternative noninvasive strategies to exclude or detect venous thromboembolism (VTE). Serial CUS testing for the detection of DVT in patients with a low to moderate CP on PE and a nondiagnostic VP scan or negative spiral CT is predicted to be safe and will reduce the need for PA to less than 10% or even less than 5%. This noninvasive serial CUS strategy restricts the need for invasive PA to a minor group of patients (< 5%) with the combination of a low CP on PE and high probability VP scan or the combination of a nondiagnostic VP scan or negative spiral CT and a high CP on PE. Prospective evaluations are warranted to implement and to validate the advantages and the disadvantages of the various combinations of noninvasive strategies and to compare serial CUS testing versus PA in randomized clinical management studies of outpatients with suspected pulmonary embolism.

Development of a latex immunoturbidimetric assay for the automated measurement of alpha2 plasmin inhibitor-plasmin complex in human plasma.

We have developed a rapid, sensitive, and quantitative latex immunoturbidimetric assay for the measurement of alpha2 plasmin inhibitor-plasmin inhibitor complex (PIC) in human plasma. The method is based on the latex agglutination reaction using a suitable pair of monoclonal antibodies. One reacts with plasmin and the other reacts with alpha2 plasmin inhibitor. In this assay, we added 6-aminohexanoic acid to the reaction buffer in order to avoid the nonspecific latex agglutination caused by precursor proteins such as plasminogen. We used this method with an automatic analyzer HITACHI 7150 (Hitachi Ltd., Hitachi, Japan) and measured PIC within the range of 0.2 to about 50 mg/mL in only 15 minutes. The precision indices (CV%) of intra-assays and interassays were <4.4% and <3.4%, respectively. The influence of plasminogen or alpha2 plasmin inhibitor on plasma was negligible. Based on these results, it is considered that this method would be useful for evaluation of a broad spectrum of fibrinolytic disorders, particularly disseminated intravascular coagulation.

[Cutaneous hypersensitivity at the site of injection of vitamin K1]. / Hypersensibilité cutanée au point d'injection de vitamine K1.

INTRODUCTION: Skin reactions after vitamin K injections are uncommon and only seen with vitamin K1 (phytomenadione). Possible association with liver disease is debated. The pathophysiological mechanism would be related to hypersensitivity to phytomenadione. CASE REPORT: Two new cases of hypersensitivity reactions at the point of vitamin K1 injection are reported. Neither of the patients had liver disease. DISCUSSION: Injectable vitamin K1 can cause skin reactions whatever the dose and mode of injection. Two clinical presentations have been described: an acute eczematous aspect and a late onset sclerous and atrophic form. The first cases of hypersensitivity to vitamin K were reported in patients with liver disease. Several recent publications did not find such an association. Our two observations would confirm this hypothesis. The pathophysiological mechanism of the acute form would involve type IV allergy to phytomenadione as suggested by the delay between sensitization and reactivation, the histology, the patch tests which are positive with phytomenadione and negative with the carrier and the presence of reaction at rechallenge. However, the lack of the necessary sensitization phase and abnormally slow regression of eczematous lesions are unusual and might be explained by a particularly active antigenic effect of the phytomenadione molecule possibly related to the phytyl moiety.

The hemodynamic and fibrinolytic response to low dose epinephrine and phenylephrine infusions during total hip replacement under epidural anesthesia.

Lower rates of deep vein thrombosis have been noted following total hip replacement under epidural anesthesia in patients receiving exogenous epinephrine throughout surgery. To determine whether this is due to enhanced fibrinolysis or to circulatory effects of epinephrine, 30 patients scheduled for primary total hip replacement under epidural anesthesia were randomly assigned to receive intravenous infusions of either low dose epinephrine or phenylephrine intraoperatively. All patients received lumbar epidural anesthesia with induced hypotension and were monitored with radial artery and pulmonary artery catheters. Patients receiving low dose epinephrine infusion had maintenance of heart rate and cardiac index whereas both heart rate and cardiac index declined significantly throughout surgery in patients receiving phenylephrine (p = 0.0001 and p = 0.0001, respectively). Tissue plasminogen activator (t-PA) activity increased significantly during surgery (p < 0.005) and declined below baseline postoperatively (p < 0.005) in both groups. Low dose epinephrine was not associated with any additional augmentation of fibrinolytic activity perioperatively. There were no significant differences in changes in D-Dimer, t-PA antigen, alpha 2-plasmin inhibitor-plasmin complexes or thrombin-antithrombin III complexes perioperatively between groups receiving low dose epinephrine or phenylephrine. The reduction in deep vein thrombosis rate with low dose epinephrine is more likely mediated by a circulatory mechanism than by augmentation of fibrinolysis.

Identification of molecular forms of plasminogen and plasmin-inhibitor complexes in urokinase-activated human plasma.

Urokinase-activated human plasma was analysed by acetic acid/urea/polyacrylamide-gel electrophoresis. The bands representing plasminogen, the plasmin-alpha 2-plasmin inhibitor and plasmin-alpha 2-macroglobulin complexes were identified by immunoprecipitation with specific antibodies and by comparison with purified components. Plasminogen and the plasmin-inhibitor complexes were isolated from plasma or thrombin-clotted plasma containing 125I-labelled Glu-plasminogen (residues 1-790) and urokinase. The plasma was kept at 37 degrees C for 0.5 and 10 times the lysis time of the clotted plasma, the clotted plasma until lysis. The plasmin heavy chain from the plasmin-inhibitor complexes was subsequently prepared. Only in one case could a low-grade proteolytic conversion of Glu- forms into Lys/Met/Val-forms (residues 77-790, 68-790 and 78-790 respectively) during the preparations be detected. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and N-terminal sequence analysis of the purified plasminogen and plasmin heavy chain showed the following. The plasminogen in plasma was on the Glu- form. Glu-plasmin constituted 0.74 and 0.58 of the plasmin bound to the alpha 2-plasmin inhibitor in plasma after brief and prolonged activation respectively. The rest was Lys/Met/Val-plasmin. The clotted plasma contained about equal amounts of Glu-plasminogen and Lys/Met/Val-plasminogen, and predominantly Lys/Met/Val-plasmin complexed to alpha 2-plasmin inhibitor and alpha 2-macroglobulin. The results of the analysis of the purified material substantiated the identity of radioactive protein bands in the gel after acetic acid/urea/polyacrylamide-gel electrophoresis.