Usual Heparin Research Articles

Safety and Dose-Finding Study of Activated Protein C (Drotrecogin Alfa Activated) as an Anticoagulant in End-Stage Renal Disease Patients Treated with Hemodialysis

Background/Aims: End-stage renal disease (ESRD) patients treated with hemodialysis (HD) experience a high risk of death. ESRD patients with elevated levels of pro-inflammatory cytokines are at increased risk of death from cardiovascular events and infection. HD is often facilitated by the use of an anticoagulant. We hypothesized that the use of an anticoagulant that also possessed anti-inflammatory qualities without significant immunosuppressive effects may reduce the risk of death. In this pilot study, we sought to determine the optimal dose of activated protein C (APC) to achieve adequate regional anticoagulation for HD and determine if the drug can be safely used in ESRD patients treated with HD. Methods: Twelve stable HD patients were enrolled into this safety and dose-finding study. Varying doses of APC were administered in place of usual heparin at varying doses to determine the range of APC that can be used for extracorporeal circuit anticoagulation. Partial thromboplastin time was assessed at fixed intervals during the HD treatment. Results: The average age of study patients was 49 ± 12 years. 75% of patients were African-American and 66.7% were male. The optimal dose of APC to induce adequate anticoagulation was 24-30 μg/kg/h. No patients experienced any serious adverse events. One patient had their infusion stopped early due to refractory intradialytic hypertension. Conclusions: For ESRD patients undergoing HD, an initial starting dose of 24-30 μg/kg/h achieves a target partial thromboplastin time that should be adequate for circuit anticoagulation. This dose appears safe and was well tolerated.

Heparin-triggered release of camouflaged tissue plasminogen activator for targeted thrombolysis

A targetable, heparin-triggered release system for tissue plasminogen activator (tPA) was designed to prevent the excessive ‘lytic’ state associated with the current tPA therapy for acute thrombotic conditions, such as myocardial infarction (MI). The strategy is, upon target accumulation, to trigger tPA release from a prodrug construct by a usual heparin dose. A relatively inactive form of tPA was constructed by conjugating tPA with low-molecular weight heparin followed by complexation with albumin-protamine conjugate, termed ‘camouflage’. The modified tPA was ~ 97% as active as native tPA. The prodrug construct of tPA significantly masked the enzymatic activity, which was fully recovered upon heparin addition. The camouflaged tPA was stable in human blood for at least 30 min and was able to trigger enzyme activation in vitro at heparin level of 0.4 U/mL. In vivo studies on jugular vein rat thrombosis model showed that the clot lysis of the heparin-triggered camouflaged tPA group was equivalent to the tPA + heparin group without prolongation of activated partial thromboplastin time (aPTT) before and after the treatment. This proof-of-principle study suggests that the activity of the tPA prodrug construct can be triggered at the thrombus site at therapeutic heparin concentration conjunctively used for MI with reduced bleeding risk.

Incidence of Heparin-Induced Thrombocytopenia and Therapeutic Strategies in Pediatric Cardiac Surgery

We identified the incidence of heparin-induced thrombocytopenia and the antiheparin-platelet factor 4 (PF4) antibody in pediatric patients undergoing cardiac surgery and documented the differences in the anticoagulation management for the extracorporeal circulation. Between January 2001 and September 2003, 559 cardiac procedures with extracorporeal circulation in 415 patients with congenital heart defects were performed in our institution. Because the development of heparin-induced thrombocytopenia requires previous exposition to heparin, only the 144 patients undergoing a scheduled second procedure on extracorporeal circulation were screened preoperatively. Of these 144 patients, 41 underwent also a third procedure and were screened before each procedure for presence of antiheparin-PF4 antibodies and for clinical signs of heparin-induced thrombocytopenia. The incidence of antiheparin-PF4 antibodies during the study period was 1.4% (2 of 144 patients). Patients with clinically significant heparin-induced thrombocytopenia could not be identified. Outside the study protocol, 2 more patients with antiheparin-PF4 antibodies were found. In these 4 patients, surgery was performed using lepirudin (Schering, Berlin, Germany) instead of the usual heparin management for extracorporeal circulation. Three of these 4 patients had an uneventful procedure and postoperative course. In 1 patient after total cavopulmonary connection, a reoperation was necessary on the seventh postoperative day owing to partial thrombosis of the lateral tunnel. The incidence of heparin-induced thrombocytopenia and of antiheparin-PF4 antibodies in patients undergoing repeated cardiac surgery is low. In antiheparin-PF4 antibody positive patients, the complete avoidance of heparin can be achieved and may account for an uneventful perioperative course.

Near Fatal Pulmonary Embolism

A case of a 79-year-old female admitted to the hospital with a hip fracture and suffering a near-fatal embolism, is presented. The article then reviews the epidemiology of deep venous thrombosis and pulmonary embolism in the setting of hip fracture and orthopedic surgery and outlines the diagnostic approach to a critically ill patient with pulmonary embolism. The use of thrombolysis as an adjunct to usual heparin therapy is examined, as are the potential benefits versus the absolute risks of thrombolysis. Finally, practical recommendations outlining a reasonable approach to this group of patients, based on available evidence, are proposed.

Thromboembolic disease and present oral contraception.

Since their introduction, oral contraceptives have been linked to an increased incidence of thromboembolic events. Epidemiologic studies have shown that women who use third-generation oral contraceptives containing desogestrel, gestodene, or norgestimate have a higher risk of venous thrombosis than women who use second-generation oral contraceptives containing levonorgestrel. Women who use oral contraceptives are significantly less sensitive to activated protein C. From January 1996 to December 2001, 17,577 patients were hospitalized in our department, 177 of them (1%) had confirmed diagnosis of venous thromboembolism and 15 of those (177) were women on oral contraceptive therapy. Oral contraceptives were taken from 28 days to 18 months. No other potential congenital or acquired causes of thrombosis were present before thromboembolic events occurred in these women. The discontinuation of the pill combined with usual heparin (in one patient thrombolysis) and coumarin therapy was effective in all cases. After the discontinuation of coumarin (3-6 months), every patient was screened for hereditary thrombophilia. All women on oral contraceptive therapy had confirmed hereditary risk factors for venous thrombosis. Acquired resistance to activated protein C may explain the epidemiologic observation of increased risk of venous thrombosis in oral contraceptive users, especially in women using third-generation oral contraceptives who had other risk factors (hereditary or acquired) for venous thrombosis.

Heparina de alto peso molecular. Uma alternativa nas operações com circulação extracorpórea: estudo experimental

Introduction: In surgical procedures, with cardiopulmonary bypass, hemorrhagic syndromes during and after pump constitute a major concern and a great number of cases they are heparin-related, a substance still without substitute. Most authors point out the anticoagulant action of heparin as the main problem bleeding situations and research is developing on antifibrinolytic or platelet-like- drugs to try to substitute for usual heparin. Experience with low-molecular weight heparin, without anticoagulant properties, cardiopulmonary bypass, was disastrous. High dosage was accompanied by high tube drainage suggesting that postoperative bleeding does not happen just because of the anticoagulant effect of heparin. Material and Methods: Believing the vascular component of hemostasis and that low-molecular weight heparin non-neutralized by protamin is responsible for the paralysis of small vessels during and after cardiopulmonary bypass surgery, we isolated a high-molecular weight heparin ( modal weight of 25.000 Daltons) to be tested in vitro and in vivo. Results: Its specific anticoagulant activity, by mass, was superior to usual heparin ( modal weight of 15.000 Daltons) in vitro (273 ui/mg against 181 ui/mg, respectively) as in vivo, dogs, utilizing cardiopulmonary bypass and measuring its activity by activated clotting time, APTT and heparin blood levels. In the experimental laboratory the half-life of usual heparin was of 60 minutes, while for high-molecular weight heparin was above 90 minutes. Conclusion: We believe that this unprecedented experience will lead to its future use anima nobile to further test its neutralization by protamin as well as to confirm the decreased prevalence of bleeding phenomena with its use.

Isolated Iliac Vein Thrombosis During Oral Contraceptive Therapy in Three "Normal" Women

Isolated iliac vein thrombosis appears to be a rare clinical entity. It is usually due to extrinsic compression on the iliac vein with consequent stasis. Diagnosis may be difficult since compression ultrasonography is usually negative. Only phlebography is surely diagnostic. This procedure should be carried out whenever there is a discrepancy between the clinical evaluation and a negative sonography. We report three women on oral contraceptive therapy in whom a diagnosis of isolated iliac vein thrombosis was suspected clinically and confirmed phlebographically. No other congenital or acquired potential cause of thrombosis was present in the propositae but for the oral contraceptives. Oral contraceptives had been taken for 12, 3, and 2 months respectively for three patients before thrombosis occurred. Two of the propositae were 25 years old and the third was 54. The latter patient had been given oral contraceptives to "prevent osteoporosis" after menopause. The discontinuation of the pill together with usual heparin and coumarin therapy were effective in every instance. A specific pathogenic role of the oral contraceptives may be surmised. In fact, no isolated iliac vein thrombosis was found in a control group of 20 women of fertile age we showed to have idiopathic deep vein thrombosis of the legs. This article emphasizes once again the importance of a careful clinical evaluation in the suspicion of deep vein thrombosis. Key Words: Oral contraceptive therapy-Deep vein thrombosis-Iliac vein thrombosis.

Preparative countercurrent chromatography for isolation of charge density-fractionated heparin.

A preparative method is described for continuous flow fractionation of heparin according to charge density in two-phase systems of butanol-hexadecylpyridinium chloride/aquaous NaCl. The separation is carried out on a "Slowly-Rotating Coil" device for countercurrent chromatography with 6 coil units and a sample capacity of 80 mg heparin. A turbidometric method is described which can be used to rapidly quantify the distribution of heparin. Characterization of fractions showed that linear charge density, binding constant for acridine orange, and specific activities in a "global" plasma anticoagulant assay and in a specific activities in a specific biochemical thrombin-inhibition assay varied with the NaCl concentration in the eluting phase. Some partial resolution of the two functional activities was observed. The fractions are much more homogeneous in composition than are the usual heparin preparations and may be useful as standards or in structure-function studies.

A comprehensive evaluation of the heparin–manganese precipitation procedure for estimating high density lipoprotein cholesterol

The accurate quantitation of high density lipoproteins has recently assumed greater importance in view of studies suggesting their negative correlation with coronary heart disease. High density lipoproteins may be estimated by measuring cholesterol in the plasma fraction of d > 1.063 g/ml. A more practical approach is the specific precipitation of apolipoprotein B (apoB)-containing lipoproteins by sulfated polysaccharides and divalent cations, heparin-Mn(2+) being the most commonly used combination. The present heparin-Mn(2+) procedure was found to be reasonably specific and not often subject to large errors; however, 9% (primarily hypertriglyceridemic samples) of the 966 plasma samples treated with heparin-Mn(2+) had obvious supernatant turbidity, indicating incomplete sedimentation of apoB-associated lipoproteins. Furthermore, 48% of the nonturbid supernates contained more than 1 mg/dl (mean 2.5 mg/dl) of apoB-associated cholesterol when measured by a radial immunodiffusion procedure, indicating slight overestimation of HDL cholesterol. Determination of the extent of the unprecipitated apoB-associated lipoproteins by sensitive radioimmunoassay and of the amount of precipitated high density lipoprotein by radial immunodiffusion assay of apolipoproteins A-I and A-II at various heparin and Mn(2+) concentrations indicated that the usual heparin level (approximately 1.3 mg/ml) was adequate. However, a twofold increase in Mn(2+) concentration to 0.092 M improved precipitation of the apoB-associated lipoproteins without excessive precipitation of high density lipoprotein from plasma. This increased Mn(2+) level also provided improved sedimentation of the apoB-associated lipoproteins from hypertriglyceridemic plasma. Additional observations suggested that, for convenience, the heparin and Mn(2+) can be added simultaneously as a combined reagent, that samples can be incubated for 10 minutes at room temperature before centrifugation, and that turbid supernates from hypertriglyceridemic samples can usually be made free of apoB-associated lipoproteins by centrifugation at 12,000 g for 10 minutes.