Heparin-induced thrombocytopenia-alternative anticoagulation in pregnancy and lactation

Heparin-induced thrombocytopenia (HIT) appears rarely in pregnant patients who are being treated with heparin. When HIT is suspected, heparin treatment should be discontinued and alternative anticoagulation should be started. The heparinoid danaparoid appears to be the drug of choice for acute treatment and prophylaxis because of its low placental permeability. Between the 12th and 36th weeks of pregnancy, either danaparoid may be continued or warfarin may be used after recovery of platelet counts. Before and during delivery, danaparoid should be preferred over warfarin in order to avoid bleeding complications in mother and infant. Hirudin should only be used when either cross-reactivity with heparin-induced antibodies or cutaneous allergy against heparinoids are observed. Postpartum warfarin seems to be the treatment of choice because breast-feeding can be continued. Alternative treatment with either danaparoid or hirudin is possible, but data on treatment with these reagents in lactating mothers are very limited.

Risk factors and long-term follow-up of patients with the immune type of heparin-induced thrombocytopenia

Dispositional risk factors for developing the immune-type of heparin-induced thrombocytopenia (HIT) are yet unclear. This article presents a long-term follow-up of patients with HIT to define possible risk factors that may increase the risk of HIT. The clinical course of acute HIT was analyzed retrospectively in 52 patients with HIT. Thirteen patients died; 8 due to HIT. A follow-up investigation was performed in 28 of the remaining 39 patients 29 +/- 12 months after the onset of HIT, including genotyping for the factor V G1691A- and the prothrombin G20210A-mutation, measurement of antithrombin, protein C, protein S, factor VIII, and factor XII activity as well as the concentration of antiphospholipid antibodies. The results were compared to an age- and sex-matched control group. New thromboembolic events and re-exposure to heparin were also documented. No difference between patients and controls was observed concerning the factor V Leiden mutation, the prothrombin mutation, factor XII, antithrombin, protein S, or protein C deficiency and antiphospholipid antibodies. Increased factor VIII activity was found in 16 of 21 HIT patients compared to 4 of 21 controls (p=0.0005). New thromboembolic events developed in 5 patients within 9 months after HIT. One patient had been re-exposed to heparin 9 months after acute HIT without any complications. Increased factor VIII activity was frequently observed in patients in whom HIT developed. Thromboembolic complications within the first months after onset of HIT occurred often.

Incidence and clinical relevance of heparin-induced antibodies in patients with deep vein thrombosis treated with unfractionated or low-molecular-weight heparin

The frequency of heparin-induced thrombocytopenia (HIT) varies between different clinical treatment settings and remains unknown for patients treated with unfractionated (UFH) or low-molecular-weight heparin (LMWH) because of deep vein thrombosis. In this multicentre, open-label study, 1137 patients with deep vein thrombosis were randomly assigned to UFH for 5-7 d, reviparin, a LMWH, for 5-7 d (short-treated group) or reviparin for 28 d (long-treated group). Heparin-platelet factor 4 antibodies (HPF4-A) were determined on d 5-7 and d 21. Heparin-induced thrombocytopenia was defined by clinical evaluation. Two patients in the UFH group (incidence: 0.53%, 95% confidence interval (CI): 0.06-1.91) and two patients in the long-treated LMWH group (incidence: 0.53%, 95% CI: 0.06-1.92) had HIT, while no HIT was observed in the short-treated LMWH group. Pulmonary embolism developed in one of the HIT-patients, who had HPF4-A and was treated with UFH. On d 5-7 the incidence of HPF4-A was 9.1% in the UFH group, 2.8% in the short-treated LMWH group and 3.7% in the long-treated LMWH group, with a significant increase to 20.7% in the UFH group and to 7.5% in the long-treated LMWH group on d 21. Therefore the incidence of HPF4-A and heparin-induced thrombocytopenia was lower in patients treated with LMWH compared with UFH for the same duration of treatment.

MIXCON-LA: a precise, sensitive and specific aPTT-based assay for detection of lupus anticoagulant

Lupus anticoagulants (LA) are associated with an increased risk of thrombosis and laboratory detection is of major importance. Multiple tests are available for screening and confirmation, but they differ in sensitivity and specificity, frequently lacking the ability to discriminate between the presence of LA, heparin, and oral anticoagulants. Based on the test-principle of the Lupus Ratio-test, an automated, sensitive APTT-based assay, using mixtures of a lupussensitive and a lupusinsensitive APTT-reagent with normal plasma for detection of lupus anticoagulants was developed. Ninety-nine healthy volunteers, ten patients treated with unfractionated heparin intravenously, 19 patients taking stable oral anticoagulation, five patients with hemophilia A, and 15 patients with antiphospholipid-antibody-syndrome (APS) were investigated. In all patients, two APTTs were performed, one with each reagent, on 1:1 mixtures of test plasma and normal plasma (MIXCON-LA assay). The ratio between the two clotting times was divided by the corresponding ratio for the normal plasma. This final lupus ratio (LR) was used for evaluation. The within-series imprecision and the between-series imprecision were excellent with coefficients of variation between 1.5% and 1.9%. The mean +/- 2 SD of the LR of the 99 healthy volunteers was used as reference range (LR: 0.95-1.07). All patients treated either with heparin or oral anticoagulants remained negative in the MLXCON-LA assay (specificity, 100%), while one of five patients with hemophilia A, in whom a factor VIII-inhibitor developed, showed a false-positive result. In 13 of 15 patients with APS, an increased ratio was observed (sensitivity, 87%). This assay system allows precise, specific, and sensitive detection of lupus anticoagulants.

[Anticoagulation of pregnant women with mechanical heart valve prostheses]

Patients with a mechanical heart valve prosthesis (MHVP) are usually anticoagulated with oral anticoagulants (OAC) to prevent thromboembolic complications. Considering the paucity of published data, the management of women with MHVP of childbearing age, who wish to become pregnant, still remains difficult and complicated. OAC may cause embryopathy during the first trimester, while neurologic complications, stillbirth and fetal death may appear during the second and third trimester. While the application of unfractionated heparin (UFH) in pregnant patients with MHVP may fail to prevent thromboembolic complications even with therapeutic dosage, only little is known about the application of body weight adjusted therapeutic dosages of low molecular weight heparin (LMWH). We report on 8 female patients, 7 with MHVP, one with atrial fibrillation, who were treated with LMWH during the whole pregnancy. No malformations or major bleeding complications were observed, no valve thrombosis or thromboembolic complications occurred. Three patients developed moderate heart failure during the third trimester, which resolved after treatment. In three patients, cesarean section was necessary, while the other five patients delivered spontaneously. Therefore, anticoagulation with body weight adjusted LMWH seems to be an alternative, safe and efficient treatment for pregnant women with MHVP. Prospective, randomized studies are needed to further evaluate this new therapeutic approach. The underlying heart disease represents a serious comorbid condition that requires continuous interdisciplinary monitoring.

Use of a low-molecular-weight heparinoid (danaparoid sodium) for continuous renal replacement therapy in intensive care patients

The purpose of this study was to evaluate the efficacy and safety of danaparoid in the treatment of critically ill patients with acute renal failure and suspected heparin-induced thrombocytopenia (HIT) needing renal replacement therapy (RRT). We conducted a retrospective analysis of 13 consecutive intensive care patients with acute renal failure and suspected HIT who were treated with danaparoid for at least 3 days during RRT. In eight patients, continuous venovenous hemofiltration was performed. The mean infusion rate of danaparoid was 140 +/- 86 U/hour. Filter exchange was necessary every 37.5 hours. In five patients, continuous venovenous hemodialysis was used. A bolus injection of 750 U danaparoid was followed by a mean infusion rate of 138 +/- 122 U/hour. Filters were exchanged every 24 hours. In 7 of 13 patients, even a low mean infusion rate of 88 +/- 35 U/hour was efficient. Mean anti-Xa (aXa) levels were approximately 0.4 +/- 0.2 aXa U/mL. Persistent thrombocytopenia despite discontinuation of heparin treatment was observed in 9 of 13 patients, owing to disseminated intravascular coagulation (DIC). HIT was confirmed by an increase in platelet count and positive heparin-induced antibodies in 2 of 13 patients. No thromboembolic complications occurred, but major bleeding was observed in 6 of 13 patients, which could be explained by consumption of coagulation factors and platelets due to DIC in 5 of 6 patients. Nine of 13 patients died of multiorgan failure or sepsis, or both. In none of these patients was the fatal outcome related to danaparoid treatment. In critically ill patients with renal impairment and suspected HIT, a bolus injection of 750 U danaparoid followed by a mean infusion rate of 50 to 150 U/hour appears to be a safe and efficient treatment option when alternative anticoagulation is necessary.

Determination of heparin-platelet factor 4-IgG antibodies improves diagnosis of heparin-induced thrombocytopenia

Only a few patients with heparin-induced antibodies develop heparin-induced thrombocytopenia (HIT). In this study, we investigated whether different immunglobulin classes can be used to differentiate between antibody-positive patients with and without HIT. Four different patient populations were investigated: 32 patients with the immune type of HIT with thromboembolic complications, 13 patients with HIT without thromboembolism, 24 patients with heparin-platelet factor 4 (PF4) antibodies without clinical symptoms of HIT, and 20 heparin-treated patients with thrombocytopenia caused by other reasons. In all patients the immunglobulin mixture of IgG, IgM and IgA, and the single immunglobulin classes of heparin-PF4 antibodies, were investigated. No significant differences between HIT patients with thromboembolic complications and patients with isolated HIT were found concerning the different immunglobulin classes. Antibody-positive patients with HIT had significantly higher levels of IgG antibodies than those without HIT (P < 0.05), while they did not differ concerning IgM and IgA antibodies. By determining IgG antibodies, the specificity of the enzyme-linked immunosorbent assay (ELISA) system was increased without loss of sensitivity. Heparin-PF4-IgG antibodies can identify patients at risk of developing life-threatening HIT. Future ELISAs should only include this immunglobulin class, as the determination of the antibody mixture may lead to overestimation of HIT.

[Removal of lepirudin used as an anticoagulant in mechanical autotransfusion with Cell-Saver 5]

Former studies demonstrated that small amounts of heparin might remain in the prepared retransfusion blood during intraoperative autotransfusion. This could lead to serious complications in patients suffering from heparin-induced-thrombocytopenia type II (HIT II). Lepirudin is an approved anticoagulant in HIT II-patients. We studied to what extent lepirudin is washed out during the preparation of retransfusion blood, when it is used as anticoagulant for the autotransfusion device cell saver 5.

METHODS

We investigated four different concentrations of lepirudin solutions, 5 mg, 10 mg, 20 mg and 30 mg per litre normal saline. In order to imitate a clinical situation, each lepirudin solution was mixed with human blood in a 1:5-ratio and put into the reservoir of the cell saver. The device was started in the automatic mode using 1000 ml saline as washing solution. Several runs were carried out (five times using the 5 mg/l solution, ten times the 10 mg/l, eleven times the 20 mg/l and eleven times the 30 mg/l solution). The lepirudin concentration in the prepared retransfusion blood was measured.

RESULTS

The median percentage reduction of the lepirudin content from the reservoir blood to the retransfusion blood was 100% for the 5 mg/l, 90.4% for the 10 mg/l, 94.3% for the 20 mg/l and 86.3% for the 30 mg/l solution. The differences of percentage reduction are not significant. But the different lepirudin concentrations in the anticoagulant solution have a significant influence on the lepirudin concentration in the retransfusion blood. The lepirudin concentration (median) in the retransfusion blood was 0.00 microgram/ml for the 5 mg/l, 0.16 microgram/ml for the 10 mg/l, 0.19 microgram/ml for the 20 mg/l and 0.66 microgram/l for the 30 mg/l lepirudin solution.

CONCLUSION

Lepirudin as an anticoagulant for intraoperative autotransfusion is effectively eliminated using the cell saver 5 device in the automatic mode with 1000 ml saline as washing solution. A clinically relevant disturbance of coagulation is not to be expected, even if the highest concentration of lepirudin anticoagulant solution investigated in this study is used.

[Danaparoid (Orgaran) as an antiocoagulant for mechanical autotransfusion with Cell Saver 5 (Hemonetics)]

We investigated Danaparoid Sodium (Orgaran) as anticoagulant using three different concentrations (9, 4,5 or 3 U/ml anticoagulant solution) for the use in the autotransfusion device Cell Saver 5 (Haemonetics). Fresh units of whole blood packs were mixed in the reservoir in a proportion of 5:1 with the anticoagulant solution. Having started the Cell Saver 5 in the automatic mode, the amount of Danaparoid in the retransfusion blood was determined (chromogenic Antifactor-Xa test). The lowest concentration of the anticoagulant was applied in 4 patients with Heparin-induced Thrombocytopenia Type II undergoing total hip arthroplasty. There was a correlation between the concentration in the reservoir and in the retransfusion blood. None of the patients showed a disturbance of his coagulation system. One of them had slight clotting in the reservoir. We recommend the use of the lower concentrations tested: 4,5 U/ml or, particularly for patients with renal insufficiency or low body weight or expected high retransfusion volumes, 3 U/ml as anticoagulant concentrations. If the autotransfusion device is used according to the manufacturer's instructions there may be virtually no risk of clotting in the Cell Saver or of inhibition of the coagulation system in the patient.

Hirudin determination in plasma can be strongly influenced by the prothrombin level

Recombinant hirudin is increasingly used for therapeutic and prophylactic anticoagulation. Several laboratory methods are available to measure r-hirudin, including clot-based and amidolytic methods. The snake venom ecarin converts prothrombin to meizothrombin. Hirudin inhibits meizothrombin, causing a prolongation of the ecarin clotting time (ECT). Because the ECT depends on prothrombin levels in plasma, it was compared with a chromogenic substrate assay (CSA) for the determination of r-hirudin levels in prothrombin deficient plasma samples. R-hirudin (0.0-2.0 microg/mL) was added to plasma samples with decreasing prothrombin concentrations (100-0%). Using the ECT, false high r-hirudin levels were observed even in r-hirudin-free plasma, when prothrombin levels were below 50%. This effect was more pronounced with increasing r-hirudin levels. Additionally, r-hirudin (0.5 microg/mL) was added to plasma of patients with acquired prothrombin deficiency due to oral anticoagulation. Hirudin levels were also overestimated in these plasma samples using ECT. In plasma samples of patients treated with r-hirudin, because of suspected heparin-induced thrombocytopenia (HIT), hirudin levels were already measured falsely high, when the prothrombin levels were below 70%. The chromogenic substrate assay (CSA) determined correct values in all prothrombin-deficient plasma samples. Therefore, the CSA should be used for hirudin level determination, if overestimation due to prothrombin deficiency should be avoided.

[Current management of thromboembolism in pregnancy and puerperium]

Venous thromboembolism (VTE) remains the leading cause of maternal death. Today, various risk factors and conditions are known to increase the risk for VTE associated with pregnancy. Having identified the individual risk of a pregnant women, appropriate preventive measures can be taken. If VTE occurs during pregnancy, an appropriate immediate diagnostic work-up is essential in order to avoid further complications. For deep vein thrombosis (DVT) the diagnostic tool of choice is color-coded duplex-sonography, for pulmonary embolism (PE) perfusion/ventilation lung scan can be used. Integrating a detailed individual and family history, the presence of thrombophilia or other risk factors, a risk stratification can be undertaken. These risk categories are defined in the present paper and the appropriate treatment measures are described. As oral anticoagulants cross the placenta and may cause embryopathy in any trimester, oral anticoagulants should be avoided throughout pregnancy. Therefore, heparin is the anti-coagulant of choice for pregnant women, with low molecular weight heparins (LMWH) having distinctive pharmacological advantages over unfractionated heparins. Besides a potential for bleeding, the main side effects of heparin include heparin-induced thrombocytopenia which prompts for platelet monitoring, especially in the first weeks of heparin treatment, and, secondly, heparin-induced osteoporosis, which is a potential sequel of long-term heparin administration. Even though there are abundant reports in the literature on the use of LMWH in pregnant women, that show that they are safe and effective, LMWH are not specifically licensed for the use in pregnancy.

A prospective study on the incidence and clinical relevance of heparin-induced antibodies in patients after vascular surgery

The heparin-platelet factor 4-antibody assay, polyanion-platelet factor 4-antibody assay and heparin-induced platelet activation test are used for laboratory diagnosis of the immune form of heparin-induced thrombocytopenia. Fifty consecutive patients receiving heparin treatment for more than 5 days after vascular surgery were prospectively screened for heparin-induced thrombocytopenia antibodies, thrombocytopenia (daily platelet counts), deep-vein thrombosis (color-coded duplex sonography), and arterial reocclusion (clinical assessment). None of the patients developed thrombocytopenia or thrombosis in association with formation of heparin-induced thrombocytopenia antibodies. Despite the absence of clinical evidence of heparin-induced thrombocytopenia, many patients formed heparin-induced thrombocytopenia antibodies: 34% of the patients were positive in the heparin-platelet factor 4-antibody assay, 28% in the polyanion-platelet factor 4-antibody assay, 14% in the heparin-induced platelet activation test, and 54% with any of these tests. Patients predominantly developed IgM (24%) and IgA antibodies (16%), whereas IgG antibodies were found in 12% of patients. Whereas the majority of patients with positive ELISA assays had IgM and IgA antibodies, patients with a positive functional assay (heparin-induced platelet activation test) predominantly had IgG antibodies. We conclude that a high percentage of patients develop heparin-induced antibodies after vascular surgery without any clinical symptoms of heparin-induced thrombocytopenia. None of the assays therefore is predictive of the clinical manifestation of heparin-induced thrombocytopenia in asymptomatic patients. Therefore, the diagnostic specificity of both antigen and activation assays for heparin-induced thrombocytopenia appears to be relatively low in the vascular surgery patient population.

Hirudin treatment in a breastfeeding woman

We report on a breastfeeding woman with deep venous thrombosis treated with hirudin because of heparin-induced thrombocytopenia, in whom hirudin was not detectable in human breastmilk.

[Ambulatory treatment of an acute pulmonary artery embolism in fresh thigh vein thrombosis using low-molecular-weight heparin]

HISTORY AND CLINICAL FINDINGS

A 39 year-old man presented with dyspnoea and calf pain. Aside from two long-distance flights there were no triggering events for deep vein thrombosis (DVT). 6 years before the patient had had a spontaneous DVT. Family history concerning DVT was negative.

INVESTIGATIONS

The patient presented with tachypnoea but no significant dyspnoea at rest. Color-coded duplex scan revealed a free floating thrombus in the left femoral vein, lung perfusion scan exhibited perfusion defects on the right side with a high probability for pulmonary embolism (PE). Echocardiography showed no signs of right ventricular failure. Thrombophilia screening was normal including prothrombin and factor V gene analysis.

TREATMENT AND COURSE

As the patient refused hospital admission, after informed consent he was treated on an out-patient basis with low molecular weight heparin (LMWH) with the dosage adjusted to body weight, despite of the pending licensing of most LMWH for PE. Compression therapy was initiated and patient education on self-injection was performed. On the second day, oral anticoagulation was initiated. The further course was uneventful and long-term oral anticoagulation was continued.

CONCLUSION

LMWH is at least as safe and effective as unfractionated heparin for the treatment of DVT, and it had been demonstrated that out-patient treatment of patients with DVT is safe. For PE however, most LMWHs are not yet licensed in Germany, even though recent studies show that they are safe and effective in the same doses regimen. As data on out-patient treatment of PE are sparse, out-patient treatment of symptomatic PE seems not generally advisable at present, although--as shown in the present case--it is feasible under particular circumstances.

Heparin-induced thrombocytopenia type II: perioperative management using danaparoid in a coronary artery bypass patient with renal failure

An 84-year-old patient with heparin-induced thrombocytopenia (HIT), global cardiac decompensation, and acute renal failure underwent a cardiosurgical intervention using an extracorporeal circuit. For systemic anticoagulation danaparoid (Orgaran) was applied as a heparin substitute preoperatively and maintained for systemic anticoagulation during ECC despite it being eliminated by the kidney. The postoperative recovery was prolonged due to bleeding complications. During cardiopulmonary bypass (216 min) the target level of anti-factor Xa was 1.5 UI/ml. This required continuous infusion and an occasional bolus of danaparoid. Coagulation in the extracorporeal circuit was observed twice at plasma levels below 1.4 IU/ml. There were no thromboembolic or neurologic events. We did not retransfuse blood from the extracorporeal circuit or the cardiotomy reservoir after bypass, but because elimination of danaparoid was impaired in this patient and there is no neutraliser available antifactor Xa postoperatively exceeded 0.6 IU/ml for 30 hours. Diffuse bleeding with tamponade resulted. Weaning the patient from the respirator was achieved 12 hours after the last re-exploration. From the 4th postoperative day 750 IU of danaparoid were administered twice daily subcutaneously for thrombosis prevention. On the 6th postoperative day discharge from the ICU was possible. We conclude that the application of danaparoid for cardiopulmonary bypass in patients suffering from acute renal failure may be complicated by hemorrhage.

[Significance of hereditary thrombophilia for risk of thrombosis with oral contraceptives]

Oral contraceptives increase the natural incidence of venous thromboses of 1-2/10,000 women per year 3-to 4fold. Recent investigations have shown that during intake of desogestrel or gestodene containing formulations the risk is twice that with older low-dose ovulation inhibitors. This difference is larger in first time users than in women who had previously used an oral contraceptive. During pregnancy, the incidence of thromboses rises up to 10/10,000 women-years and post partum up to 40/10,000 women-years. In about 60 % of thromboses no causal explanation can be found. It is suggested that in 40 % of all cases an inherited thrombophilia is present. Among the hereditary types of thrombophilia, the resistance against activated protein C (APC-resistance) represents nearly 50 %, while altogether 15 to 20 % is based on a deficiency of antithrombin III, protein C or protein S. APC-resistance the prevalence of which is 3-5 % in the general population, increases the risk of thrombosis 8fold and in users of oral contraceptives 35fold. Protein C-deficiency (prevalence 0.1-0.5 %) increases the risk of thrombosis 9fold and in users of oral contraceptives 15fold, while antithrombin III-deficiency (prevalence 0.02-0.05 %) enhances the risk in pill-users 8fold. Ovulation inhibitors do not influence risk of thrombosis in women with protein S-deficiency. Antiphospholipid-antibodies the concentration of which may increase during treatment with oral contraceptives, represent a considerably enhanced risk of thrombosis, too. A positive family history (before age of 40 years) indicates an inherent thrombophilia. In these risk groups, the cost/benefit ratio of a selective screening is unfavorable, as at most 70 % of the hereditary thrombophilias can be diagnosed by laboratory analysis, and only very few patients will actually experience a thrombotic event: only 3 of 1000 carriers of APC-resistance will suffer from thrombosis during oral contraception per year. On the other hand, a negative result of laboratory tests does not exclude a hereditary thrombophilic disorder which as yet cannot be substantiated. It is not yet clarified whether a selective screening is superior to a careful assessment of individual and family history. A general screening cannot be justified because of the unfavorable cost/benefit ratio. If the individual or family history or pathological laboratory parameters indicate an enhanced risk of thrombosis, this risk has to be carefully weighed against the consequences of discontinuation of pill use. Those few individuals with risk factors who will experience a thrombosis, cannot be identified in advance. If in patients with thrombophilic disorders and/or other risk factors the use of oral contraceptives represents a particularly high risk, other contraceptive methods should be taken into consideration. If a patient with risk factors decides for the use of oral contraceptives, she has to be informed that in the case of symptoms indicating a thrombosis, the physician has to be consulted immediately. The earlier an appropriate therapy is initiated, the more effectively an acute pulmonary emboli or permanent damages, e.g. the post-thrombotic syndrome, can be prevented.

Regression of deep vein thrombosis by i.v.-administration of a low molecular weight heparin--results of a pilot study

Twenty-five patients with phlebographically confirmed deep vein thrombosis of the lower limb were treated with intravenous infusions of low molecular weight heparin for 7 to 29 days. The mean dosage was 15.2 +/- 3.0 Uanti-Xa (equivalent 7.6 +/- 1.5 U-aPTT). Phlebograms were taken before, during and after the treatment with low molecular weight heparin and evaluated using the score system of Marder. Nearly complete recanalization of the occluded veins was found in six (24%) patients, improvement of the Marder score of 60 to 90% was found in four patients and of 30 to 60% in seven patients, while eight patients remained unchanged. With an average dose of 15.2 I.U./kg/h the heptest was prolonged to 70 to 120 seconds while the aPTT-level did not significantly increase. tPA-antigen-levels increased significantly in most of the patients after the third day of treatment, while PAI-activity remained unchanged. A positive conclusion between the decrease of the Marder score and the duration of treatment was found. Thus the low molecular weight heparin used in this investigation proved to be effective and safe in treating deep vein thrombosis.