Oral contraceptive pills and hormonal replacement therapy and thromboembolic disease.

The risk of thromboembolic complications with the use of second and third generation oral contraceptives is minimal and probably related to underlying congenital or acquired thrombophilic states. Estrogen dose-dependency leads to increased thrombin generation and increased plasmin generation. There is no convincing evidence that the balance between clotting and fibrinolysis is disturbed. The risk of venous thromboembolism with pregnancy is greater than with oral contraceptives. Hormone replacement therapy is safe for healthy women, and the benefits far outweigh the potential risks.

Disseminated intravascular coagulation (DIC).

DIC is a life-threatening complication of several disease states. It is characterized by systemic activation of the hemostasis system. In many instances the release of tissue factor (TF) from endothelial cells or other circulating cells triggers the system. Initially, the increased activation can be compensated for by the natural inhibitor systems, a state referred to as compensated DIC. As the trigger persists, inhibitors will be consumed leading to more coagulation. In this process many clotting factors, most notably fibrinogen and platelets are consumed, resulting eventually in a complete breakdown of the hemostasis system. This results in a profuse and diffuse bleeding tendency or decompensated DIC. The term consumptive coagulopathy denotes this process. Of crucial importance is the fate of fibrin that is formed from fibrinogen by thrombin. If the fibrinolytic system is insufficiently activated, fibrin will be deposited in the microcirculation leading to MODS. This will not occur if the fibrinolytic system is fully activated. The clinical suspicion of DIC must be confirmed by laboratory tests and decreasing fibrinogen levels and platelet counts support the diagnosis. The determination of D-dimer, fibrin(ogen) split products (FSP) and soluble fibrin monomer (FM) further support the diagnosis. FM suggest the presence of thrombin, FSP the generation of plasmin, and D-dimer, both thrombin and plasmin. While the tests are not specific for DIC, they can be helpful, in the proper clinical setting, to diagnose decompensated or acute DIC. The tests are not useful for the diagnosis of compensated DIC, except for D-dimer, FSP, and FM if elevated. Compensated DIC can be diagnosed by molecular markers of in vivo hemostasis activation, such as thrombin-antithrombin (TAT) complexes, prothrombin fragment 1 + 2 (F 1 + 2), or plasmin-antiplasmin (PAP) complexes. For the treatment of DIC it is imperative to remove the triggering underlying disease. The consumption of coagulation constituents can be corrected by cryoprecipitate, platelet concentrates, and fresh frozen plasma, if needed. This may reduce the bleeding tendency. Arrest of the activated hemostasis system by heparins, either subcutaneous in low doses or intravenous in therapeutic doses, is only recommended in patients with compensated DIC. If the patient bleeds, heparins should not be given. The administration of concentrates of natural anticoagulants, i.e., antithrombin, protein C, or tissue factor pathway inhibitor are safer than heparins since they do not exacerbate the bleeding tendency. These concentrates were found to be very effective in animal models of DIC; human experience is still limited. Generally, the earlier treatment is initiated, the better the patient's prognosis.

Sticky platelet syndrome.

The sticky platelet syndrome (SPS) is an autosomal dominant platelet disorder associated with arterial and venous thromboembolic events. It is characterized by hyperaggregability of platelets in platelet-rich plasma with adenosine diphosphate (ADP) and epinephrine (type I), epinephrine alone (type II), or ADP alone (type III). Clinically, patients may present with angina pectoris, acute myocardial infarction (MI), transient cerebral ischemic attacks, stroke, retinal thrombosis, peripheral arterial thrombosis, and venous thrombosis, frequently recurrent under oral anticoagulant therapy. Clinical symptoms, especially arterial, often present following emotional stress. Combinations of SPS with other congenital thrombophilic defects have been described. Low-dose aspirin treatment (80 to 100 mg) ameliorates the clinical symptoms and normalizes hyperaggregability. The precise etiology of this defect is at present not known, but receptors on the platelet surface may be involved. Normal levels of platelet factor 4 (PF4) and beta-thromboglobulin in plasma suggest that the platelets are not activated at all times; they appear to become hyperactive upon ADP or adrenaline release. In vivo clumping could temporarily or permanently occlude a vessel, leading to the described clinical manifestations. The syndrome appears to be prominent especially in patients with unexplained arterial vascular occlusions.

The effects of a low-dose monophasic preparation of levonorgestrel and ethinyl estradiol on coagulation and other hemostatic factors.

OBJECTIVE: This study was undertaken to evaluate the effects on hemostatic factors of a low-dose preparation of levonorgestrel and ethinyl estradiol in a 12-cycle study. STUDY DESIGN: Thirty healthy women began taking 100 microg levonorgestrel and 20 microg ethinyl estradiol on the first day of the menstrual cycle, continued to take the preparation for the next 21 days, and then took placebo for 7 days. Mean changes in prothrombin time, partial thromboplastin time, and levels of factors VII and X, antithrombin, plasminogen, fibrinogen, protein S, thrombin-antithrombin complexes, and D-dimer were analyzed at baseline and at cycles 3, 6, and 12 with paired Student t tests. RESULTS: Factor X, plasminogen antigen and activity, and D-dimer levels were significantly increased (P

Usefulness of subcutaneous low molecular weight heparin (ardeparin) for reduction of restenosis after percutaneous transluminal coronary angioplasty.

In addition to its anticoagulant effects, heparin is known to have antiproliferative effects on vascular smooth muscle cells. Ardeparin is a partially depolymerized (low molecular weight) heparin that has a longer half-life than unfractionated heparin. Following successful coronary balloon angioplasty, 565 patients were randomized to treatment with twice-daily subcutaneous ardeparin 50 anti-Xa U/kg (low dose) or 100 anti Xa U/kg body weight (high dose), or placebo for 3 months. Follow-up angiography was performed in 415 patients at 4 months, or earlier if clinically indicated. Additionally, patients underwent treadmill exercise electrocardiography at 2 weeks and 4 months. This study was designed to test the hypothesis that 3 months of subcutaneous dosing of ardeparin would reduce angiographic restenosis after coronary balloon angioplasty. Ardeparin had no effect on the incidence of angiographic restenosis (prespecified definition: > or = 50% luminal diameter narrowing plus a loss of 50% of initial gain or absolute decrease of 20% of luminal diameter). Neither the mean luminal diameters nor mean percent diameter stenoses were different among the treatment groups before, after, or 4 months after balloon angioplasty. On exercise electrocardiography at 2 weeks and 4 months, patients in all treatment groups had similar exercise tolerance, incidence of angina, and frequency of ST depression. Thus, ardeparin treatment given subcutaneously for 3 months after successful balloon angioplasty does not reduce either angiographic or clinical measures of restenosis.

Low molecular weight heparins and heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) and HIT thrombosis syndrome (HITTS) are immune-mediated complications of clinical use of unfractionated heparin (UFH). The antibody/antigen complex is composed of heparin and platelet factor 4. This complex not only activates platelets but also the clotting system leading to thrombin generation. This explains the thrombosing tendency of these patients, and venous and arterial thromboembolisms are encountered with a morbidity and mortality of about 25-37%. The incidence of HIT is about 3% when UFH is administered therapeutically. The diagnosis is at this time based on clinical observations, especially a sudden, unexplained drop in platelet counts without other reasons. Laboratory tests can be used to confirm the clinical diagnosis, but none of the available tests is 100% reliable. There is no test that will predict HIT and no test that will signal the development of HITTS. Treatment consists of discontinuation of UFH in any form and anticoagulation with danaparoid or r-hirudin, if needed. The use of low molecular weight heparins instead of UFH could largely (not totally) alleviate the problem.

Therapeutic use of antithrombin concentrate in sepsis.

Sepsis and its associated complications of disseminated intravascular coagulation (DIC) and multiple organ dysfunction syndrome (MODS) continue to be a major cause of morbidity and mortality. Improved detection of all forms of DIC is essential to assure earlier diagnosis. Studies already indicate that the therapeutic use of antithrombin (AT) concentrate may produce a more positive outcome for sepsis-associated DIC. If DIC could be identified earlier and AT concentrate could then be given earlier in the sepsis continuum, study results for the use of AT concentrate in humans might reveal a statistically significant difference versus placebo, and the efficacy of AT concentrate for this syndrome is more likely to be proved. Fixed-bolus doses of AT concentrate based on body weight are currently preferred, but improved, user-friendly assays for plasma AT levels would permit more rapid turnaround time for AT results and could help fine-tune the use of AT concentrate to the specific needs of each patient. Clinical trials involving the therapeutic use of AT concentrate in sepsis should continue, and it can be hoped that their design will reflect the concepts and conclusions offered by this panel of investigators.

PFA-100 system: a new method for assessment of platelet dysfunction.

The PFA-100 system is a platelet function analyzer designed to measure platelet-related primary hemostasis. The instrument uses two disposable cartridges: a collagen/epinephrine (CEPI) and a collagen/ADP (CADP) cartridge. Previous experience has shown that CEPI cartridges detect qualitative platelet defects, including acetylsalicylic acid (ASA)-induced abnormalities, while CADP cartridges detect only thrombocytopathies and not ASA use. In this seven-center trial, 206 healthy subjects and 176 persons with various platelet-related defects, including 127 ASA users, were studied. The platelet function status was determined by a platelet function test panel. Comparisons were made as to how well the defects were identified by the PFA-100 system and by platelet aggregometry. The reference intervals for both cartridges, testing the 206 healthy subjects, were similar to values described in smaller studies in the literature [mean closure time (CT) 132 s for CEPI and 93 s for CADP]. The use of different lot numbers of cartridges or duplicate versus singleton testing revealed no differences. Compared with the platelet function status, the PFA-100 system had a clinical sensitivity of 94.9% and a specificity of 88.8%. For aggregometry, a sensitivity of 94.3% and a specificity of 88.3% were obtained. These values are based on all 382 specimens. A separate analysis of sensitivity by type of platelet defect, ASA use versus congenital thrombocytopathies, revealed for the PFA-100 system a 94.5% sensitivity in identifying ASA users and a 95.9% sensitivity in identifying the other defects. For aggregometry, the values were 100% for ASA users and 79.6% for congenital defects. Analysis of concordance between the PFA-100 system and aggregometry revealed no difference in clinical sensitivity and specificity between the systems (p > 0.9999). The overall agreement was 87.5%, with a Kappa index of 0.751. The two tests are thus equivalent in their ability to identify normal and abnormal platelet defects. Testing 126 subjects who took 325 mg ASA revealed that the PFA-100 system (CEPI) was able to detect 71.7% of ASA-induced defects with a positive predictive value of 97.8%. The overall clinical accuracy of the system, calculated from the area under the ROC curve, was 0.977. The data suggest that the PFA-100 system is highly accurate in discriminating normal from abnormal platelet function. The ease of operation of the instrument makes it a useful tool to use in screening patients for platelet-related hemostasis defects.

Prospective double-arm study of fibrinolysis in surgical patients.

BACKGROUND: During surgery, the balance between thrombosis and fibrinolysis is altered. Methods reported to increase fibrinolysis, such as compression devices, may reduce venous thrombosis. However, there are no prospective studies comparing methods and the effect on fibrinolysis. MATERIALS AND METHODS: In a prospective study, general surgical patients were randomized to either sequential compression devices (Group 1) or subcutaneous heparin (Group 2), and fibrinolysis factors were measured in order to determine the effect on the fibrinolysis system. Blood samples were drawn at a similar time of the day with the tourniquet off. Specifically, t-PA antigen, plasminogen activator inhibitor-1 (PAI-1), and D-dimer were measured preoperatively (preop) and on Postoperative Days (POD) 1 and 7 by the ELISA method. Fibrinolysis factors were reported as the mean +/- SD and as percentage change from preoperative values. Noninvasive vascular studies were performed preop, and on POD 1, 7, and 30, by an examination of the infrainguinal venous system and external iliac veins in bilateral lower extremities. Nonambulatory patients were excluded from the study and DVT prophylaxis methods were initiated at surgery and used through POD 2. RESULTS: For the 136 patients in the study, there were no differences in clinical characteristics such as age, surgical time (all > 60 min), anesthesia type (general or spinal), type of surgical procedure, or other risk factors for DVT. Two DVTs occurred at POD 1 and 30 (both Group 2), and one pulmonary embolism in each group (POD 7 for Group 1; POD 1 for Group 2). For subjects without thrombosis, D-dimer changes were parallel for both groups, increasing through POD 7. Similarly, t-PA antigen levels rose from baseline on POD 1 in both groups, with a return toward baseline by POD 7. The PAI-1 levels increased on POD 1 in both groups, but severalfold more in Group 1 (compression devices). The elevation in PAI-1 decreased by 50% in Group 1 by POD 7, while values returned to normal in Group 2. These changes were not significant using the Mann-Whitney test. Only three patients had thrombotic episodes so that data on changes in fibrinolysis factors are difficult to compare with the larger group. CONCLUSIONS: This is the first report of a prospective, randomized comparison of fibrinolysis factors using sequential compression devices in comparison to low dose unfractionated heparin in general surgical patients, and comparing postoperative values to preop. Both groups showed an enhanced fibrinolysis by elevation in t-PA antigen and D-dimer on POD 1, as expected when fibrinolysis occurs. While PAI-1 and t-PA work in parallel, the marked elevation of PAI-1 on POD 1 (although only slightly above reference values) and continuing into POD 7 for subjects using compression devices requires further inquiry. The elevation of PAI-1 in the face of elevated t-PA and D-dimer has been reported, but the comparison between patients using sequential compression devices and mini-dose heparin has not been reported. The reason for the elevation requires additional study into other influences on the synthesis, secretion, and/or function of PAI-1 that do not affect t-PA.

Antithrombin: its physiological importance and role in DIC.

Antithrombin (AT) is a single-chain glycoprotein in plasma and belongs to the family of the serpins. It is synthesized in liver parenchymal cells, and its plasma concentration is between 112-140 mg/L. AT is a unique inhibitor of the clotting system and neutralizes most of the enzymes generated during activation of the clotting cascade, especially thrombin, factors Xa and IXa. Equimolar, irreversible complexes are formed between AT and the enzymes. The interaction between AT and the activated clotting factors is at least 1,000-fold increased in the presence of heparins. Heparins bind to multiple sites of the AT molecule resulting in a steric reconfiguration. Heparins contain a specific pentasaccharide unit which is the minimum requirement for AT binding. The glycosaminoglycan (GAG) heparan sulfate found on endothelial cell surfaces also contains this pentasaccharide and can thus "activate" AT. It is believed that much of the physiological inactivation of enzymes by AT occurs on the endothelium, mediated by heparan sulfate. The binding of AT to the GAGs also releases prostacyclin which possesses strong antiinflammatory properties. Deficiencies of AT are inherited or acquired. Only acquired defects due to increased consumption are discussed, most notably AT in DIC, especially DIC in sepsis. During acute DIC, clotting factors and inhibitors are consumed faster than they can be reproduced. This consumption of AT is of great significance in DIC and sepsis, and plasma AT levels predict outcome. AT levels drop early in sepsis and laboratory signs of DIC can already be found in patients with SIRS and early sepsis. The important role of AT in DIC and sepsis is the basis for considering antithrombin concentrates as an additional therapeutic modality.

The haematological manifestations of sepsis.

Haematological changes in the septic patient are, primarily, neutropenia or neutrophilia, thrombocytopenia and disseminated intravascular coagulation (DIC). Thrombocytopenia frequently arises from DIC although inhibition of thrombopoiesis or immunological platelet damage also occur. DIC contributes to bleeding and microvascular thrombosis, leading to multiple organ failure. Tissue factor release, primarily mediated by tumour necrosis factor, activates the clotting system; fibrinolysis is initially activated, but later becomes inhibited by the release of plasminogen-activator inhibitor (PAI-1), further fostering multiple organ failure. Most septic patients have compensated, chronic DIC, detectable by assays of molecular markers; the earliest signs are already found during the systemic inflammatory response syndrome. Compensated DIC later becomes decompensated with rapid consumption of factors including inhibitors such as antithrombin III (AT III) and proteins C and S. AT III concentrations of < 60-70% of the normal values predict outcome. Management of DIC must address the underlying disease, interrupt the activated haemostasis system and replace consumed coagulation constituents. Interruption of haemostasis with heparin may be attempted, but bleeding may worsen. Administration of a natural anticoagulant, such as AT III, may arrest clotting without concomitant risk of bleeding. In several animal models of DIC, AT III concentrates shortened the duration of DIC and reduced multiple organ failure and mortality. Similar benefits have been reported in early studies of patients with DIC, especially in the absence of sepsis. Studies are under way to determine whether outcome will improve if patients with sepsis are treated before the development of shock and plasma AT III concentrations are maintained at 100-150% of normal.

Absolute and comparative subcutaneous bioavailability of ardeparin sodium, a low molecular weight heparin.

Ardeparin sodium (Normiflo, Wyeth-Ayerst) is a low molecular weight heparin undergoing clinical evaluation as an antithrombotic agent. The objective of this study was to evaluate the absolute and comparative bioavailability of ardeparin following subcutaneous administration of three different formulations [two formulations of ardeparin at 10,000 anti-factor Xa (aXa) U/ml, but with different preservatives, and a 20,000 aXa U/ml formulation]. The study was conducted using a randomized 4-period crossover design (three subcutaneous treatments and one intravenous treatment) in 24 healthy subjects, and the pharmacokinetics of ardeparin were characterized by plasma anti-factor IIa (aIIa) and anti-factor Xa (aXa) activities. The mean absolute bioavailability of ardeparin based on aIIa activity ranged from 62% to 64% and the mean absolute bioavailability based on aXa activity ranged from 88% to 97%. Based on bioequivalence testing criteria, the three ardeparin formulations were bioequivalent.

Effects of warfarin on markers of hypercoagulability in patients with heart failure.

Heart failure is associated with a hypercoagulable state. A single-center, randomized, double-blind, placebo-controlled trial was performed to test the hypothesis that warfarin will modify a hypercoagulable state in heart failure. This study included 76 patients with heart failure. At baseline, patients had evidence for a hypercoagulable state with elevated plasma levels of thrombin/antithrombin III (TAT) complexes (3.4 +/- 2.0 ng/ml), prothrombin fragment F1 + 2 (1.5 +/- 0.9 nmol/L), and D-dimers (630 +/- 401 ng/ml). Warfarin therapy (international normalized ratio [INR] 2.7 +/- 1.3) significantly decreased plasma levels of TAT complexes (p < 0.002), F1 + 2 (p < 0.001), and D-dimers (p < 0.001) when compared with baseline values at 1, 2, and 3 months of therapy. In contrast, patients receiving placebo had persistent elevation of TAT complexes (p = not significant [NS]), F1 + 2 (p = NS), and D-dimers (p = NS) during follow-up at 1, 2, and 3 months. The two treatment groups followed different trends over time for all three markers (p < 0.001). The effect of low-intensity warfarin (INR 1.3 +/- 0.08) versus moderate-intensity warfarin (INR 2.3 +/- 1.1 ) on markers of hypercoagulability was evaluated in 14 patients. When compared with baseline, low-intensity warfarin administration decreased plasma levels of TAT complexes (p = NS), F1 + 2 (p = 0.05), and D-dimers (p = 0.04). In these patients F1 + 2 was further reduced with moderate-intensity warfarin (p < 0.001). Our findings suggest that a hypercoagulable state in heart failure can be modified by warfarin therapy.

In vitro platelet function in controlled ovarian hyperstimulation cycles.

OBJECTIVE: To determine the effects of elevated endogenous E2 levels on in vitro platelet function in patients undergoing controlled ovarian hyperstimulation (COH). DESIGN: Women with normal ovulatory cycles and patients undergoing COH on cycle day 3 and near ovulation (preovulatory follicles were at least 16 mm in diameter) were studied. Serum E2, Thrombostat 4000, (V. d. Goltz, Seeon, Germany), von Willebrand factor antigen (vWF-Ag), and platelet aggregation and adenosine triphosphate (ATP) release to adenosine diphosphate (ADP), collagen (COL), and arachidonic acid (AA) were measured. SETTING: University-based outpatient infertility clinic. PATIENT(S): Twenty-two consenting infertile women undergoing COH cycles and 14 women with documented ovulatory cycles. MAIN OUTCOME MEASURE(S): Whole blood platelet aggregation with ADP, COL, AA, and Thrombostat 4000. RESULTS(S): Estradiol levels rose significantly at peak times (P = 0.011). No changes were noted in in vitro platelet function measured by the Thrombostat 4000 and by whole blood platelet aggregation with ADP and AA and in ATP release with ADP, COL, or AA. Aggregation with collagen was increased because of likely elevations in vWF-Ag levels. CONCLUSION(S): No significant changes in in vitro platelet function were noted in 19 women undergoing COH with E2 levels two to three times that observed in oral contraceptive or hormone replacement therapy users, suggesting no increased risk for arterial thromboembolism.

Antithrombin levels related to infections and outcome.

Antithrombin (AT) was measured in the plasma of 59 trauma patients at Detroit Receiving Hospital from July 1987 through December 1992 to determine how well low AT levels correlated with the outcome and development of later infections. The average lowest AT measured was 74 +/- 14% (SD) (normal = 75 to 120%). The mean lowest AT of the 11 trauma patients who developed sepsis (45 +/- 13%) was significantly lower than that of the 15 who developed an infection without sepsis (66 +/- 12%) (p < 0.001) and of the 33 who did not develop an infection (87 +/- 15%) (p <0.001). No patient with an AT always > or = 70% became septic or died, and no patient with an AT always > or = 90% developed an infection. In the 33 patients who did not develop infections, the mean AT levels rose progressively from 75 +/- 17% during the first 48 hours after admission to 91 +/- 11% during the next 48 hours. In contrast, the mean AT levels in the 26 patients who later developed infections were significantly lower (48 +/- 24%) during the first 48 hours and 60 +/- 16% during the next 48 hours (p < 0.016 and p <0.001). Of 10 patients with an AT < 60% in the first 96 hours, 9 (90%) developed an infection later. Low levels of AT, thus, may be of help in predicting infection, outcome, or both in severely injured patients.

The dose proportionality of the pharmacokinetics of ardeparin, a low molecular weight heparin, in healthy volunteers.

Ardeparin is a low molecular weight heparin currently being evaluated as an antithrombotic agent. The objective of this investigation was to assess the effects of dose on the pharmacokinetics of ardeparin after subcutaneous administration. Eighteen healthy subjects received doses of 30 U/kg, 60 U/kg, and 100 U/kg antifactor Xa (aXa) of ardeparin by subcutaneous injection. Plasma antifactor IIa (aIIa) activity levels after the 30- and 60-U/kg doses of ardeparin were too low to reliably characterize the disposition of the drug. However, the pharmacokinetics of ardeparin could be characterized by using pharmacodynamic measurements of plasma aXa activity. The rate of absorption of ardeparin after subcutaneous administration did not change with increasing dose. The volume of distribution (Vd) of ardeparin was small, reflecting minimal distribution outside the intravascular space, and was independent of dose. The total clearance of ardeparin, however, decreased with increasing dose, and half-life (t1/2) was prolonged at the higher doses. Within the observed dose range, a doubling of the ardeparin dose resulted in an area under the plasma aXa activity-versus-time curve (AUC) that was approximately 25% greater than expected on the basis of linear disposition. The differences in AUC and clearance between the three doses suggest that the mechanism of elimination of ardeparin is saturable.