[How much dosage of heparin do you administer? The relationship between heparin dosage and activated coagulation time (ACT) value during cardiovascular surgery: a multi center investigations].

BACKGROUND: In cardiac surgery, unfractionated heparin is widely used for anticoagulation. There are differences of heparin dosages among institutions for cardiac surgery with and without cardiopulmonary bypass (CPB). The aim of this clinical investigation is to find out the optimal dosage of heparin for initiation of CPB. METHODS: In cardiac cases with CPB, patients' weight, initial dosage of heparin, ACT values after heparin administration, product name of heparin and ACT measurement devices were recorded. RESULTS: There were significant differences in initial dosages of heparin, basal ACT values and increment of ACT values per units of heparin among institutions. CONCLUSIONS: A significant difference was revealed among institutions regarding the initial heparin dosage for CPB, in spite of the same target of ACT. There was no evidence to determine the optimal dosage of heparin for initiation of CPB.

Heparin Modulates the Kinetics of Zinc-Induced Aggregation of Amyloid-ß Peptides.

Zinc-induced aggregation of amyloid-ß peptides (Aß) is considered to contribute to the pathogenesis of Alzheimer's disease. While glycosaminoglycans (GAGs) that are commonly present in interneuronal space are known to enhance Aß self-aggregation in vitro, the impact of GAGs on the formation of zinc-induced amorphous Aß aggregates has not yet been thoroughly studied. Here, employing dynamic light scattering, bis-ANS fluorimetry, and sedimentation assays, we demonstrate that heparin serving as a representative GAG modulates the kinetics of zinc-induced Aß42 aggregation in vitro by slowing the rate of aggregate formation and aggregate size growth. By using synthetic Aß16 peptides to model the Aß metal-binding domain (MBD), heparin was found to effectively interact with MBDs in complex with zinc ions. We suggest that heparin adsorbs to the surface of growing zinc-induced Aß42 aggregates via electrostatic interactions, thus creating a steric hindrance that inhibits further inclusion of monomeric and/or oligomeric zinc-Aß42 complexes. Furthermore, the adsorbed heparin can interfere with the zinc-bridging mechanism of Aß42 aggregation, requiring the formation of two zinc-mediated interaction interfaces in the MBD. As revealed by computer simulations of the zinc-Aß16 homodimer complexed with a heparin chain, heparin can interact with the MBD via polar contacts with residues Arg-5 and Tyr-10, resulting in a conformational rearrangement that hampers the formation of the second zinc-mediated interaction in the MBD interface. The findings of this study suggest that GAGs, which are common in the in vivo macromolecular environment, may have a substantial impact on the time course of zinc-induced Aß aggregation.

Structure-activity relationships of heparin. Independence of heparin charge density and antithrombin-binding domains in thrombin inhibition by antithrombin and heparin cofactor II.

To better understand how heparin structure affects its activity the relationships between the functional domains for inhibitor binding and charge density were investigated to determine how these domains affect heparin-mediated thrombin inhibition by two different heparin-dependent protease inhibitors, antithrombin (AT) and heparin cofactor II (HC II). A series of heparins, fractionated systematically by charge density, was further fractionated on antithrombin agarose to isolate more homogeneous subfractions that were either inactive or highly active with respect to thrombin inhibition by AT. With AT, the activities of the AT-active subfractions increased sharply with heparin charge density, while those with little or no affinity for AT were virtually inactive. In contrast, with HC II inhibitor, the activities of the heparins depended only upon their charge densities and were independent of AT affinity. At any given charge density, the heparin before fractionation by AT affinity and the fractions that were highly active and inactive with AT were all equally active with HC II. The two inhibitors also differed in their reactivity with heparan sulfate and dermatan sulfate. A charge-density effect with the subfractions having similar high affinity for AT demonstrates that charge density represents a heparin functional domain that is independent of the AT-binding domain. The behavior of the AT-inactive heparins, being fully active with HC II, demonstrates the functional domain necessary for AT binding is not needed to produce HC II activity.

[Relevance of some growth factors to cardiovascular disease in maintenance hemodialysis patients]. / Niektóre czynniki wzrostowe a choroby ukladu krazenia u pacjentów hemodializowanych.

Hepatocyte growth factor, activin A and follistatin compose an intricate, pleiotropic and mostly antagonistic cytokine network. They have a crucial impact on the cardiovascular system, including the development of atherosclerosis and its ischemic complications. We reviewed the significance of the above growth factors in maintenance hemodialysis patients, and stressed their likely causative role in the acceleration of cardiovascular disease progression. Recent clinical trials showing marked activation of the growth factors by heparin administered during hemodialysis procedures also were discussed, including the distinct effects of unfractionated heparin vs low-molecular-weight heparin enoxaparin.

Heparin and anticoagulation.

Heparin, a sulfated polysaccharide, has been used as a clinical anticoagulant for over 90 years. Newer anticoagulants, introduced for certain specialized applications, have not significantly displaced heparin and newer heparin-based anticoagulants in most medical procedures. This chapter, while reviewing anticoagulation and these newer anticoagulants, focuses on heparin-based anticoagulants, including unfractionated heparin, low molecular weight heparins and ultra-low molecular weight heparins. Heparin's structures and its biological and therapeutic roles are discussed. Particular emphasis is placed on heparin's therapeutic application and its adverse effects. The future prospects are excellent for new heparins and new heparin-based therapeutics with improved properties.

Heparin clearance during continuous veno-venous haemofiltration.

OBJECTIVE: To determine whether premature clotting of haemofiltration circuits could be related to heparin removal across the filter membrane into the ultrafiltrate. DESIGN: Randomised study using either unfractionated (n = 8) or low molecular weight (n = 7) heparin for anticoagulation of the haemofiltration circuit at 1000 and 600 U/h respectively. Samples were drawn at 1 and 2 h from arterial and venous limbs of the haemofilter circuit for measurement of plasma heparin (as anti-Factor Xa activity), antithrombin III and haematocrit. Ultrafiltrate samples were collected at the same time for measurement of anti-Xa activity. SETTING: Intensive care unit. PATIENTS: Patients in acute renal failure requiring haemofiltration. RESULTS: Both unfractionated and low molecular weight heparin plasma levels were within the range required for therapeutic anticoagulation in all but one patient at 2 h. Ultrafiltrate anti-Xa levels were insignificant. Antithrombin III levels in these critically ill patients were subnormal in 11 of the 15 studies. CONCLUSIONS: Despite their small sizes, neither unfractionated nor low molecular weight heparins cross the haemofilter membrane into the ultrafiltrate in any measurable quantity. Both heparins were present in plasma at a level suitable for therapeutic anticoagulation. Subnormal levels of antithrombin III may be an important factor in determining filter longevity.

Comparison between a low molecular weight and standard heparin for anticoagulation during extracorporeal CO2 removal in the dog.

Anticoagulant properties towards an artificial surface of a chemically depolymerized low molecular weight heparin (LMWH) have been compared to those of a standard heparin (SH). The experimental model consisted in a seven hours extracorporeal veno-venous bypass for CO2 removal (EC-CO2R) using a membrane lung. Four animals received 150 anti-FXa U/kg followed by 40 anti-FXa U/kg/h of LMWH or 300 IU/kg followed by 100 IU/kg/h of SH. Mean Factor Xa inhibition was 49% in LMWH group and 28.5% in SH group. Mean Factor IIa inhibition was 31% and 49% respectively. After three hours of bypass fibrin deposition occurred in the reservoir in three out of four dogs receiving LMWH while none was observed under SH. No statistically significant difference between the two groups was found for any of the coagulation parameters tested (fibrinogen, factor V, antithrombin III, plasminogen, alpha 2-antiplasmin, platelet counts). At the end of bypass 5000 U protamine abolished both anti-FXa and anti-FIIa activities in the SH group but failed to neutralize more than half of the anti-FXa activity in the LMWH group. These results suggest that high anti-FIIa activities are required to prevent fibrin formation induced by artificial surfaces and that equivalent amounts of anti-FXa activities are ineffective for this purpose. In addition the use of LMWH may raise problems when emergency neutralization procedures are required.

Heparin with low affinity to antithrombin III inhibits the activation of prothrombin in normal plasma.

Standard unfractionated heparin is known to have two actions on blood clotting. Unfractionated heparin enhances the rates at which antithrombin III inactivates activated clotting factors, and inhibits the activation of both Factor X and prothrombin by disrupting the calcium and phospholipid dependent assembly of the Factor X and prothrombin activator complexes. This latter inhibitory action of heparin occurs independently of antithrombin III. A heparin fraction with low affinity to antithrombin III was prepared from standard heparin by affinity chromatography on antithrombin-III-Sepharose and its properties compared with unfractionated heparin. The low affinity heparin fraction and the unfractionated heparin had equivalent inhibitory effects on prothrombin activation in antithrombin III depleted plasma. In normal plasma, the low affinity fraction inhibited the activation of prothrombin. Unlike the unfractionated heparin, however, the fraction of heparin with low affinity to antithrombin III did not enhance the inactivation of either Factor Xa or thrombin. This antithrombin III independent inhibition of the activation of prothrombin was also evident when activated platelets were used as the source of the procoagulant phospholipids. The antithrombin III independent effect of heparin is unlikely to be important therapeutically, however, if this property of heparin is shared by other naturally occurring glycosaminoglycans, it could be important in maintaining the fluidity of blood under physiological conditions.

A heparin binding synthetic peptide from human HIP / RPL29 fails to specifically differentiate between anticoagulantly active and inactive species of heparin.

Despite extensive progress in determining structures within heparin and heparan sulfate (Hp/HS) and the discovery of numerous proteinaceous binding partners for Hp/HS so far; the only detailed characterization of a specific protein-glycosaminoglycan interaction is antithrombin III (ATIII) binding to a Hp pentasaccharide containing a unique 3-O-sulfated glucosamine residue. Previously, it was reported from our laboratories that a 16 amino acid synthetic peptide derived from the C-terminus of human HIP/RPL29 (HIP peptide-1) enriched for ATIII-dependent anticoagulant activity, presumably by specifically binding the ATIII pentasaccharide. Herein, we demonstrate that HIP peptide-1 cannot enrich ATIII-dependent anticoagulant activity from a starting pool of porcine intestinal mucosa Hp through a bio-specific interaction. However, a HIP peptide-1 column can be used to enrich for anticoagulantly active Hp from a diverse pool of glycosaminoglycans known as Hp byproducts by a mechanism of nonspecific charge interactions. Thus, HIP peptide-1 cannot recognize Hp via bio-specific interactions but binds glycosaminoglycans by non-specific charge interactions.

Heparin brand is associated with postsurgical outcomes in children undergoing cardiac surgery.

BACKGROUND: We sought to determine whether the use of specific unfractionated heparin brands during cardiopulmonary bypass for pediatric cardiac surgery was associated with differences in postoperative outcomes, especially regarding the incidence of bleeding and thromboembolic complications. METHODS: We compared postoperative outcomes for pediatric cardiac surgeries performed with Hepalean (Organon Teknika) to those performed with PPC heparin (Pharmaceutical Partners of Canada). Differences in clinical outcomes were determined in multivariable logistic and linear regression models adjusted for patients and surgery characteristics. RESULTS: In all, 903 operations were reviewed, 289 (32%) using Hepalean and 614 (68%) using PPC heparin. Patient demographics and surgical variables were comparable between groups. In multivariable regression models, adjusted for patients' characteristics, heparin use and choice of antifibrinolytic agents, the use of PPC heparin was associated with greater use of red blood cell transfusions in the first 48 postoperative hours (estimates +1.6 mL/kg, p<0.001), increased odds of bleeding complications (odds ratio 3.8, p=0.04), thromboembolic complications (odds ratio 4.7, p=0.01), early unplanned reoperation (odds ratio 6.9, p=0.03), longer postoperative intensive care unit stay (estimate +3.2 days, p<0.001), and longer hospital stay (estimate +3.6 days, p<0.001). CONCLUSIONS: Brand of unfractionated heparin used during cardiopulmonary bypass for pediatric cardiac surgery was associated with bleeding complications and clinical outcomes. Different brands of unfractionated heparin should not be considered equivalent without proper validation in formal trials.

Avaliação técnico-regulatória dos requisitos de qualidade para registro de medicamentos biológicos e biossimilares humanos: perspectivas e desafios no Brasil / Technical and regulatory evaluation of quality requirements for the registration of human biological and biosimilar drugs: perspectives and challenges in Brazil

Medicamentos biológicos são obtidos a partir de fluidos biológicos ou tecidos de origem animal por procedimentos biotecnológicos e, a partir do vencimento das suas patentes, surge a possibilidade da produção de suas cópias, os chamados biossimilares. Este tema, além de polêmico, por ainda apresentar divergências de entendimento da classe científica, também engloba 4 das 5 classes terapêuticas de medicamentos mais vendidas, e apresenta evolução crescente no mercado farmacêutico. Com o aumento da demanda, cresce o interesse na produção de medicamentos biológicos de alta qualidade, com a mesma eficácia, porém a preços mais baixos. Dessa forma, é possível entender a responsabilidade das regulamentações, principalmente no que diz respeito aos biossimilares, a fim de que eles respeitem os requisitos mínimos necessários para serem comparáveis ao seu medicamento biológico novo. Assim, este trabalho teve como objetivo avaliar questões técnico-regulatórias e os requisitos de qualidade para registro de medicamentos biológicos e biossimilares humanos frente a diferentes Autoridades Sanitárias mundiais. A análise foi baseada em três moléculas biológicas, sendo a clássica heparina e moléculas novas, filgrastim e infliximabe. Foi constatado que na teoria, a legislação brasileira é baseada em regulamentos internacionais, especialmente da Federal and Drug Administration (FDA) e European Medicines Agency (EMA), e que na prática, o Brasil tem se mostrado mais conservador na extrapolação de indicação e na aprovação dos biossimilares. Ainda, foi possível notar que independente do país, as Farmacopeias ainda necessitam de aprimoramento com relação a este tema, pois em sua maioria, não existe padronização dos parâmetros e testes a serem realizados. Pesquisa demonstrou que o conhecimento sobre biossimilares ainda não está consolidado entre profissionais médicos e que, portanto, há necessidade de programas para esclarecimentos, com a finalidade de estimular seu uso, quando possível e com custos mais interessantes

Biological drugs are obtained from biological fluids or animals tissues by biotechnological procedures and, from the expiration of their patents, the possibility of producing their "copies", the so-called biosimilars, arises. In addition to being a controversial subject, as it still presents divergences of understanding by the scientific class, it also encompasses 4 of the 5 therapeutic classes of best-selling drugs, and it presents an increasing evolution in the pharmaceutical market. As demand increases, interest in the production of high-quality biological drugs with the same effectiveness, but at lower prices, also increases. In this way, it is possible to understand the responsibility of regulations, especially with regard to biosimilars, so that they comply with the minimum requirements needed to be comparable to their reference biological medicine. Thus, the objective of this project was to evaluate technical and regulatory topics, as well as quality requirements for the registration of human biological and biosimilar medicines under the perspective of different Health Authorities around the world. The analysis was based on three biological molecules, being the classic heparin and new molecules, filgrastim and infliximab. It was found that in theory, Brazilian regulation is based on international regulations, especially the Federal and Drug Administration (FDA) and the European Medicines Agency (EMA), and that in practice, Brazil has been more conservative in the extrapolation of indication and approval of biosimilars. Also, it was possible to note that, regardless the country, Pharmacopoeias still need to be improved for this topic, since in general, there is no standardization of the parameters and tests to be performed. Research showed that the knowledge about biosimilars is not yet consolidated among doctors and that, therefore, there is a need for clarification programs, with the purpose of stimulating their use, when possible and at lower costs

Historia de la heparina / History of heparin

No disponible

Aneurisma da artéria carótida interna / Aneurysm of the internal carotid artery

Os aneurismas de artéria carótida interna (ACI) extracraniana são raros. Há poucos relatos na literatura médica quanto à sua etiologia, relacionando-os à doença aterosclerótica, às arterites e alterações decorrentes do trauma ou após procedimento cirúrgico. A história natural da doença ainda não está bem estabelecida. Entretanto, o potencial risco de embolia originário do aneurisma ou mesmo de sua ruptura indica necessidade de intervenção. Apresentamos o relato de caso de uma mulher de 71 anos diagnosticada com aneurisma de 3 cm de diâmetro da ACI extracraniana direita com queixas de cefaleia pulsátil. Após tentativa sem sucesso de tratamento endovascular, optou-se pelo tratamento cirúrgico com aneurismectomia e anastomose primária término-terminal próximo à base do crânio.

Aneurysms of the extracranial internalcarotid artery are rare. There are few reports in the medical literature about the etiology of this disease, relating it to atherosclerosis, arteritis and alterations due to trauma or after a surgical procedure. The natural history of this disease has not been defined. However, the potential risk of embolism or rupture creates a need for intervention. We will present the case of a 71 year old woman with pulsatile headaches who was diagnosed a 3 cm aneurysm of the right extracranial internal carotid artery. After an unsuccessful attempt at endovascular treatment, we performed an aneurysmectomy and primary arterial anastomosis near the cranium base.

Electrofocusing of heparin: Presence of 21 monomeric and dimeric molecular species in heparin preparations.

Electrofocusing of heparins and subsequent polyacrylamide gel electrophoresis has shown that two types of heparins are present in different tissues. One of the types (from beef lung tissues) gives only a single band in agarose gel electrophoresis and 21 molecular species after electrofocusing and polyacrylamide gel electrophoresis. The other type of heparin (from pork intestinal mucosa) gives two bands in agarose gel electrophoresis and 42 molecular species after electrofocusing and polyacrylamide. Ascorbic acid treatment of the pork intestinal mucosa heparin reduced the number of molecular species to 21. A suggestion is made that some heparins exist as monomeric or dimeric molecular species forming single or double helixes.

The force-driven conformations of heparin studied with single molecule force microscopy.

Using single molecule force spectroscopy we examine the response of heparin chains to mechanical stretching. We find that at forces below 200 pN heparin behaves as a simple entropic spring. At approximately 200 pN heparin displays a large enthalpic elasticity, which is evident as a pronounced plateau in the force-extension relationship. We determine that this enthalpic elasticity is produced by sugar rings of heparin flipping to more energetic and more extended conformations. We estimate that in vivo, the forces which stretch heparin are comparable to the forces that trigger conformational transitions in our single molecule atomic force microscopy measurements. We hypothesize that these conformational transitions have biological significance in that they provide a mechanism to finely regulate the affinity of various ligands toward heparin, for example, in secretory granules undergoing exocytosis and during the mechanical interactions between cells and the extracellular matrix.