Heparin preserves antithrombin III biological activity from hyperglycemia-induced alterations in insulin-dependent diabetics

Alteration in antithrombin III (ATIII) biological activity, despite its normal plasma concentration, in diabetic subjects is shown in this report. This alteration is glycemia level-dependent, there existing an inverse correlation between fluctuations of daily blood glucose level, labile glycosylated hemoglobin and ATIII activity. The subcutaneous and endovenous heparin administration restores ATIII activity, but does not modify its plasma concentration in diabetics. Moreover, heparin treatment preserves ATIII activity from glycemia-induced alterations. These data suggest a role for glucose, probably through a labile nonenzymatic glycation process, in determining the alteration of ATIII biological activity. Moreover, showing the possibility by heparin administration to restore ATIII activity and preserve its biological function from effects of glycemia variations, stress the hypothesis that glucose and heparin compete in vivo, both against the same catalytic residue of ATIII.     

No transplacental passage of standard heparin or an enzymatically depolymerized low molecular weight heparin

In 21 women who had an abortion by hysterotomy between the 15th and 23rd week of pregnancy, the possibility that unfragmented heparin or low molecular weight heparin (LMWH) passed the placental barrier to the foetus was studied. Laboratory analyses included amidolytic assays of factor Xa inhibitory activity (XaI), antithrombin III (ATIII) and a direct measurement of heparin-like substances in plasma with a competitive binding assay. The ATIII concentration in foetal plasma was about 20% of that in normal human plasma and varied considerably between individuals (2-27%). The XaI activity did not differ between the two treated groups, but the mean XaI activity of the combined groups differed from zero (P less than 0.05). If the XaI activity was corrected for the ATIII concentration, the heparin activities no longer differed significantly from zero. As the concentration of heparin-like substances were above the detection limit (0.35 microgram/ml) in 6/16 analysable samples of foetal plasma, a further 15 women who had not received any heparin were included as controls. In 12/14 analysable foetal plasmas heparin-like substances in concentrations above 0.35 micrograms/ml could be detected. Determination of heparin activity in foetal plasma is thus difficult due to the influence of endogenous ATIII on heparin assays. In conclusion, this study did not demonstrate any evidence for the passage of heparin or LMWH across the placental barrier. No differences were detected whether unfragmented heparin or LMWH had been given to the mothers. Our results also indicate the presence of an endogenous glycosaminoglycan in foetal plasma.     

Low molecular weight heparin in extracorporeal circulation. 1st clinical applications

The haemorrhagic complications inherent to the use of heparin during cardiac surgery led us, after a pilot experimental study, to try out a low molecular weight heparin (LMWH), PK 10169, which has weaker haemorrhagic effects in vitro. Our initial experience was confined to 23 patients with differing pathologies, undergoing cardiopulmonary bypass lasting 30 to 165 minutes. The modes of injection of YK 10169 varied according to the results, especially with respect to the limitation of peaks of anti-Xa activity; 8 patients were given one bolus intravenous injection, 9 were given a bolus injection and a continuous infusion, and 6 were only given the continuous infusion. Biological monitoring of anticoagulation was based on anti-Xa activity. Analysis of the biological results showed that the principal feature was the partial correction, and occasionally the non-correction of anti-Xa activity by protamine sulphate, with no correlation between this anti-Xa activity and postoperative bleeding. The authors report cases of severe postoperative bleeding despite the supposed theoretical and experimental weakly haemorrhagic properties of LMWH, and also discuss the inefficacy of protamine sulphate. The indications for LMWH for cardiopulmonary bypass which were retained, were the rare cases of heparin-induced thrombocytopaenia. In conclusion, it is possible to use LMWH during cardiac surgery but we do not advise using it routinely as its theoretical advantages are not confirmed in practice.     

Occurrence of thrombosis and haemorrhage, relationship with anti-Xa, anti-IIa activities, and D-dimer plasma levels in patients receiving a low molecular weight heparin, enoxaparin or tinzaparin, to prevent deep vein thrombosis after hip surgery

Studies in experimental animal models and in patients receiving low molecular weight heparin (LMWH) to prevent thromboembolic events after surgery have not demonstrated a clear relationship between anti-Xa and anti-IIa activities in plasma and either bleeding or prevention of thrombosis. The relationship between these clinical outcomes and ex vivo anti-Xa and anti-IIa activities, activated partial thromboplastin time (APTT) and D-dimers were evaluated in 440 patients undergoing total hip replacement and given prophylaxis once daily with a LMWH (tinzaparin or enoxaparin) in a multicentre double-blind randomized study. 221 patients received 4500 anti-Xa IU of tinzaparin; 219 patients received 40 mg (4000 anti-Xa IU) of enoxaparin. Both regimens were administered subcutaneously once daily. Blood samples for anti-IIa, anti-Xa, D-dimers levels and APTT were taken at baseline, on day 1, day 5 and on the day of discharge (days 8-14) and clinical assessments were performed dafly until day 14. All patients had bilateral venography between days 8 and 14. All coagulation tests were performed in central laboratories. A significant correlation was observed between anti-IIa activity and anti-Xa activity and the dose of each LMWH injected. The anti-Xa activity was significantly higher with enoxaparin and the anti-IIa activity was significantly higher with tinzaparin. No clear relationship between these two activities and the clinical outcomes was observed. This was also true with regards to APTT. Before and after surgery, D-dimers were significantly higher in patients with deep vein thrombosis (DVT) than in those without DVT but had no predictive value. Interestingly, a significant post-operative increase of D-dimers persisted in both groups of patients during the whole observation period, possibly suggesting that a longer duration of prophylactic treatment may be appropriate.     

Determination of the levels of unfractionated and low-molecular-weight heparins in plasma: their effect on thrombin-mediated feedback reactions in vivo. Preliminary results after subcutaneous injection.

We define a standard independent unit (SIU) of heparin as that amount that, in plasma containing 1 mumol of ATIII, raises the (pseudo-)first-order breakdown constant of factor Xa by 1 min-1. These units measure all material with a high affinity for ATIII (HAM); only material above the critical chain length of 17 monosaccharide units (above critical chain length material; ACLM) catalyzes the inactivation of thrombin. An SIU of ACLM is therefore analogously defined as the amount that, in plasma containing 1 mumol of ATIII, will raise the (pseudo-)first-order breakdown constant of thrombin by 1 min-1. Of any given heparin preparation one can determine the specific HAM and ACLM activities in terms of SIU/mg. On the basis of the factor Xa and thrombin breakdown constants found in a plasma sample one can then determine the levels of HAM and ACLM. Preliminary experiments were carried out in plasma samples obtained after subcutaneous injection of unfractionated heparin (UFH) and of two types of low-molecular-weight heparin (LMWH). About three times more of UFH activity than of LMWH activity has to be injected to obtain the same levels of ACLM in the plasma. Only with the LMWHs significant amounts of BCLM are found, which rises higher and persists longer than the ACLM. We determined the course of thrombin generation in platelet-rich plasma (PRP) and in platelet-poor plasma (PPP), as well as in the PPP factor Xa generation curve and the course of prothrombin conversion. The observed inhibitions correlated much better with the levels of ACLM than with those of below critical chain length material. The difference between UFH and LMWHs can therefore not be explained in terms of antithrombin and anti-factor-Xa activity. The essential difference between UFH and LMWH appears in the feedback effect of thrombin in PRP, where thrombin generation is both inhibited and retarded by LMWH, while it is only retarded but hardly inhibited by UFH.     

Low molecular weight heparin (Alfa LHWH) compared with unfractionated heparin in prevention of deep-vein thrombosis after hip fractures

Efficacy and safety of a low molecular weight heparin (Alfa LMWH) was compared with unfractionated heparin (UFH) in the prevention of post-operative venous thromboembolism after hip fractures. Forty-nine patients were randomized to treatment with Alfa LMWH 7500 anti-Xa coagulometric units twice daily or with UFH 5000 IU t.i.d. Screening for thrombosis was performed with 125-I-fibrinogen leg scanning and strain-gauge plethysmography. Positive results were confirmed by venography. Five patients in the Alfa LMWH group (20 per cent) developed venographycally proven deep vein thrombosis (DVT) versus seven (29 per cent) in the UFH group. One pulmonary embolism and two deaths occurred in the UFH group and none in the LMWH group. No differences in haemorrhagic complications and blood loss indices were observed. Alfa LMWH appears to be a promising drug for prevention of venous thromboembolism after orthopaedic surgery. A "flexible" schedule of administration is proposed on the basis of the results of plasma anti-Xa assays.     

M118, a novel low-molecular weight heparin with decreased polydispersity leads to enhanced anticoagulant activity and thrombotic occlusion in ApoE knockout mice

Heparin and low-molecular weight heparin (LMWH) are complex, heterogeneous polysaccharides used in the treatment of arterial and venous thrombosis. M118 is a novel LMWH with low polydispersity and pronounced anti-Xa and anti-thrombin (IIa) activity as compared to current LMWHs. To determine if M118 is effective in preventing thrombosis in the setting of a vascular plaque, apolipoprotein E knockout mice fed a high fat diet were injected with M118, enoxaparin, unfractionated heparin, or saline control and examined for arterial thrombosis using a rose bengal laser induced carotid artery injury model. M118 significantly increased the time to occlusion as compared to control and unfractionated heparin but not compared to enoxaparin although fewer M118 treated animals had any vascular occlusion present at the time of protocol completion. Platelet-neutrophil aggregates were studied by flow cytometry and were found to be decreased with M118 as compared to enoxaparin. This is the first published report examining M118, a novel LMWH designed to have low polydispersity and enhanced anticoagulant activity. In an animal model of vascular plaque, M118 is a potent inhibitor of arterial thrombosis and, despite lower in vivo anti-Xa and anti-IIa activity levels, M118 was superior to UFH in the prevention of arterial thrombosis.     

Effect of patient weight on the anticoagulant response to adjusted therapeutic dosage of low-molecular- weight heparin for the treatment of venous thromboembolism.

Data evaluating the safety of using weight-based dosing of low-molecular-weight heparin (LMWH) in obese patients are limited. Some manufacturers have recommended a maximum daily dose of LMWH not to be exceeded. The purpose of this study was to determine if body weight influenced the anticoagulant response to a weight-based dose of LMWH for the treatment of venous thromboembolism. Patients with serum creatinine levels < 150 micromol/l receiving the LMWH, dalteparin 200 anti-Xa IU/kg based on actual body weight subcutaneously once daily for the treatment of deep vein thrombosis or pulmonary embolism, were eligible for the study. Patients received a minimum of 5 days LMWH treatment. Patients had peak anti-Xa levels (IL Test Chromogenic assay) measured 3-4 h following their day 3 injection and trough anti-Xa levels measured immediately prior to injections on day 3 and 5. No dose adjustments were made on the basis of the anti-Xa levels. Patients were a priori stratified into three weight classes: (A) within 20% of ideal body weight (IBW) (n = 13); (B) 20-40% of IBW (n = 14), and (C) greater than 40% of IBW (n = 10). The largest patient weighed 190 kg and had a body mass index of 58. Mean daily LMWH doses were 14,030, 17,646 and 23, 565 IU for groups A, B and C, respectively. Mean (SD) trough anti-Xa levels on day 3 were 0.12 (0.05) anti-Xa IU/ml for group A, 0.11 (0.03) anti-Xa IU/ml for group B and 0.11 (0.03) anti-Xa IU/ml for group C (p > 0.2). Similar trough anti-Xa levels were observed on day 5. Mean (SD) peak anti-Xa levels on day 3 were 1.01 (0.20) anti-Xa IU/ml, 0.97 (0.21) anti-Xa IU/ml and 1.12 (0.22) anti-Xa IU/ml for groups A, B and C, respectively (p > 0.2). No thromboembolic or bleeding complications occurred during LMWH therapy in any patients. These findings suggest that body mass does not appear to have an important effect on the response to LMWH up to a weight of 190 kg in patients with normal or near normal renal function.     

The management of antenatal venous thromboembolism in the UK and Ireland: a prospective multicentre observational survey

This prospective observational study reports on 126 women from 25 UK centres with image-proven antenatal venous thromboembolism (VTE), 62% deep vein thrombosis and 38% pulmonary embolism. Thrombophilia screening was of limited benefit except to identify antithrombin deficiency. Sixteen (13%) patients had previous VTE, all but one was related to previous pregnancy or combined oral contraceptive and 12 received no thromboprophylaxis in the index pregnancy, the other four thus received inadequate low molecular weight heparin (LMWH) doses. Treatment was with dalteparin in 25%, enoxaparin in 47%, tinzaparin in 25% and unfractionated heparin alone in 3%. 66% of patients received once-daily LMWH. Anti-activated factor X (anti-Xa) monitoring was performed at 90% of centres, with a wide range of target values. Thus current management of antenatal VTE, despite widely diverse clinical practice, appeared effective and safe, for there were no recurrent events and postpartum haemorrhage was not increased when compared to known rates. Larger studies are required to confirm this. The need for twice as opposed to once daily LMWH and for anti-Xa monitoring is questioned by this study. The importance of clinical risk assessment and adherence to the Royal College of Obstetricians and Gynaecologists guidelines on antenatal thromboprophylaxis, with adequate LMWH dosing is confirmed.     

Low molecular weight heparins in everyday practice]

Standard nonfractioned heparin has been used for fifty years in the treatment of thromboembolic accidents, and for fifteen years, since Kakkar's works, in the prevention of thromboembolic complications in a surgical and medical context [5]. The antithrombotic efficacy of nonfractioned heparin (NFH) is accompanied by hemorrhagic complications occurring in about 10% of the patients receiving a "curative" treatment at hypocoagulating doses and in about 5% of the patients receiving the low-dose "preventive" treatment. The interest raised by low molecular weight heparins (LMWH), prepared as early as 1970, was based on a concept that is currently called into question: their anti-Xa activity, accounting for the antithrombotic activity, is high, while the anti-IIa (antithrombin) activity, producing the hemorrhagic risks, is lower. The pharmacokinetic properties, including longer-lasting action and better bioavailability with subcutaneous delivery relative to standard heparin, have greatly facilitated their use in the clinical field by allowing the reduction of the daily number of injections. Extensive clinical trials have confirmed that the antithrombotic efficacy of the LMWH is at least equal, if not superior, to that of nonfractioned heparin, though without reducing the frequency of hemorrhagic complications in the prevention of postoperative phlebitis. A limited number of randomized clinical trials suggests that the LMWH might also be as effective as NFH, as expected at doses about 3 times as high as those used for prophylaxis.     

Laboratory evaluation of the effect of prophylaxis for thromboembolism with fractionated heparin in patients undergoing laparoscopic cholecystectomy.

OBJECTIVE: We studied the effect of prophylaxis for thromboembolism with low-molecular-weight heparin (LMWH) during hospitalization on the biological hemostasis system in patients who had undergone laparoscopic cholecystectomy. METHODS: This was a prospective paired cohort study without a control group (i.e., a before-after study). The subjects were 20 patients operated on laparoscopically for uncomplicated cholelithiasis. All patients received LMWH 2 h before the operation and 24 h after the first dose. Mean duration of surgery was 70 min. Pneumoperitoneum was accomplished at 14 mmHg, and all patients were operated on in the inverted Trendelenberg position (30 degrees). Patients were mobilized within 24 h, and were discharged within 48 h after surgery. As parameters of hemostasis we studied anti-Xa factor activity (anti-Xa), antithrombin III (AT III), partial active thromboplastin time (PTT) and fibrinogen. Samples were taken for laboratory analyses under basal conditions the day before the operation (first determination), 1 h after the first preoperative dose of LMWH was given (second), at the end of the operation (third), 24 h after surgery (fourth), and on postoperative day 7 (fifth). RESULTS: Mean basal values of all parameters were within the normal range. Mean anti-Xa activity was significantly higher in the second and third determinations than in the first and fifth measurements (p < 0.05). Mean PTT was significantly elevated on the second determination and decreased thereafter; however, none of the results differed significantly from the normal value. Mean AT III was significantly lower in the third determination in comparison with the first and fifth measurements. Fibrinogen was significantly higher in the fourth and fifth determinations than in the second and third measurements. Among all parameters and sampling times, the only values outside the normal range were anti-Xa activity on the second, third and fourth determinations. CONCLUSIONS: Plasma anti-Xa factor activity was increased preoperatively, and remained elevated for 24 h after surgery, returning to basal values on postoperative day 7. Partial thromboplastin time was slightly prolonged after the first dose of LMWH, indicating good antithrombotic action.     

Haemorrhagic effect of enoxaparin, a low molecular weight heparin. Comparison with unfractionated heparin in humans.

The haemorrhagic effects of unfractionated heparin (UFH) and the low molecular weight heparin (LMWH) enoxaparin were investigated and compared in the gastric mucosa (haemorrhage induced by biopsy) and skin (haemorrhage induced by Simplate) of 12 healthy volunteers. Administration of UFH and LMWH (given in a dose of 75 anti-Xa U/kg intravenously) increased median gastric bleeding time (3.5 min) and geometric mean blood loss (11.5 microliters) to 19 min (p = 0.00003) and 54.1 microliters (p = 0.0021) after UFH and to 13 min (p = 0.008) and 29.0 microliters (p = 0.275) after LMWH. Median skin bleeding time (4.25 min) increased to 6.0 min after UFH (p = 0.003) and to 6.75 min after LMWH (p = 0.0008). Mean heparin activity in plasma was 20% higher after LMWH than after UFH. The calculated gastric bleeding time to heparin activity ratio was significantly lower for LMWH than for UFH (p < 0.05).     

Intraduodenal absorption in the rabbit of a novel heparin salt.

The intraduodenal absorption of a new low-molecular-weight heparin (LMWH) diamine salt (ITF 1331) was compared with the parent compound ITF 1060 and with sodium LMWH, in anaesthetized rabbits. The administration of either salt, but not of sodium LMWH, resulted in a dose-related increase in plasma anti-Xa activity. In this respect ITF 1331 was slightly superior to ITF 1060, and in acute-toxicity studies the counterion itself (ITF 258) was less toxic than that in ITF 1060 (counterion No. 4). These data confirm that a tertiary diamine within the counterion is an important structural requirement for the bioavailability of heparin by the intraduodenal route, and suggest that ITF 1331 may represent an important advance in the search for an oral heparin.     

Prevention of venous thromboembolism in surgery, in laparoscopic surgery, in venous surgery and in urology

The article summarizes published data regarding the prophylaxis of venous thromboembolism in surgery, in laparoscopic surgery, in venous surgery and in urology. In surgical patients with low risk, no specific thromboprophylaxis is needed. Patients with moderate risk levels are the candidates for administration of subcutaneous low molecular weight heparin (LMWH) at doses under 3 400 anti-Xa units a day and patients with increased risk at doses higher than 3 400 anti-Xa units a day during the period of higher risk. In order to decrease the risk of bleeding, a half dose 2 hours prior or 4-6 hours after the operation can be administered. Under the highest risk conditions, there is a recommendation to combine LMWH over 3 400 anti-Xa units with elastic panty-hose or, alternatively, with intermittent pneumatic compression (IPC). At moderate risk levels, subcutaneous administration of unfractionated heparin at the doses of 5 000 units twice a day is also possible and at increased risk levels, a TID administration (LDUH) over the increased risk period. In patients with a significant bleeding risk, the physical method of thromboprophylaxis can be used and pharmacological prophylaxis can set in after the risk of bleeding has passed. Fondaparinux is the alternative to LMWH in people with a history of heparin induced thrombocytopenia over the past three months. The sole use of acetylsalycilic acid is not recommended. While undertaking epidural anaesthesia or analgesia, it is necessary to follow strictly the guidelines of the use of pharmacological thromboprophylaxis. Thromboprophylaxis with LMWH, LDUH, elastic panty-hose or IPC is indicated only in those patients who undergo laparoscopic surgeries and who moreover display the additional thrombosis factors. Patients with additional risk thrombosis factors undergoing major venous reconstructions require prophylaxis with LMWH (or LDUH). Uncomplicated patients undergoing transurethral or other low risk urologic surgery require no specific thromboprophylaxis. If they undergo a major intervention and/or they display additional risk thrombosis factors, they require the administration of LMWH or LDUH. Elastic panty-hose and/or intermittent pneumatic compression have the same indication as in abdominal surgeries.     

Beneficial effect of JTV-803, a new synthetic inhibitor of activated factor X, against both lipopolysaccharide-induced and tissue factor-induced disseminated intravascular coagulation in rat models.

We examined whether JTV-803, a specific activated factor X inhibitor independent of antithrombin III (ATIII), is effective against disseminated intravascular coagulation (DIC) in rat models induced by tissue factor (TF) or lipopolysaccharides (LPS). In male Wistar rats, DIC was induced by a 4 h infusion of thromboplastin (3.75 U/kg) or LPS (50 mg/kg). The rats were given JTV-803 (0.3 or 3 mg/kg, bolus intravenously) (JTV-803 groups) or low molecular weight heparin (LMWH groups) (200 U/kg, bolus intravenously) prior to an injection of TF or LPS. The results showed that JTV-803 was dose-dependently effective against DIC in both TF-induced and LPS-induced rat models. This anti-DIC effect of JTV-803 at higher doses was almost equivalent to that of LMWH in both types of DIC. Plasma ATIII activity was more prominent in the group treated with JTV-803 than in that treated with LMWH. None of rats died in the TF-induced DIC model with or without drug administration. On the contrary, seven of 22 rats died (mortality rate, 31.8%) in the LPS-induced DIC model without drug administration. Although the mortality rate of rats induced with LPS and treated with LMWH was quite high (6/16, 37.5%), none of the LPS-induced rats treated with JTV-803 died. These findings suggested that JTV-803 can treat both TF-induced and LPS-induced DIC models, and that this drug has greater potential in preserving ATIII and in improving the prognosis of DIC.     

Efficacy of enoxaparin,certoparin and dalteparin in preventing cardiac catheter thrombosis: an in vitro approach

Owing to its beneficial pharmacological profile, the low-molecular-weight heparin (LMWH) enoxaparin is increasingly being taken as an alternative to UFH in the treatment of ACS with an early invasive strategy and in elective percutaneous coronary interventions (PCI). Insufficient anticoagulation increases the risk of catheter thrombus formation during PCI. The aim of the present study was to test in vitro the hypotheses that (i) inhibiting thrombin or thrombin generation by administering LMWH is a critical intervention in preventing catheter thrombus formation and (ii) other LMWH such as certoparin or dalteparin are as effective as enoxaparin. Blood pre-treated with the anticoagulants of interest was continuously circulated through a guiding catheter by using a roller pump for a maximum experimental period of 60 min or until the catheter became occluded. Overall thrombus weight, anti-Xa activity and electron microscopic features such as deposits of platelets, erythrocytes and fibrin on the catheter surface were quantified as endpoints. All LMWH tested significantly reduced catheter thrombus generation comparable to UFH treatment whereas there was no difference between the specific LMWH with respect to catheter thrombus formation or deposition of platelets, erythrocytes and fibrin. Thrombus generation was found to negatively correlate with anti-Xa activity. The additional use of eptifibatide did not affect thrombus formation. These data suggest that modulating plasmatic coagulation by employing LMWH is critical for preventing catheter thrombus formation and at the same time offer a potential for administering LMWH other than enoxaparin, such as certoparin or dalteparin, in the setting of PCI.     

Prevention of venous thromboembolism: generally accepted guidelines

This article summarizes the published data on the prevention of venous thromboembolism. Routine thromboprophylaxis is the best way to lower the risk. It is recommended to sort patients according the thrombosis risk and to make use of the standard prophylactic modes. In low risk patients, no specific thromboprophylaxis is needed. Patients with moderate risk levels are candidates for administration of subcutaneous low molecular weight heparin (LMWH) at doses under 3 400 anti-Xa units a day and patients with increased risk at doses higher than 3400 anti-Xa units a day during the period of higher risk. In order to decrease the risk of bleeding, a half dose 2 hours prior or 4-6 hours after the operation can be administered. Under the highest risk conditions, there is a recommendation to combine LMWH over 3 400 anti-Xa units with elastic panty-hose or, alternatively, with intermittent pneumatic compression. At moderate risk levels, subcutaneous administration of unfractionated heparin at the doses of 5 000 units twice a day is also possible and at increased risk levels, a TID administration over the increased risk period. In patients with a significant bleeding risk, the physical method of thromboprophylaxis can be used and pharmacological prophylaxis can set in after the risk of bleeding has passed. Fondaparinux is the alternative to LMWH in people after major orthopaedic surgeries and with a history of heparin induced thrombocytopenia over the past three months. An alternative to the administration of LMWH even after the end of the hospitalization can be warfarin in certain situations. The sole use of acetylsalicylic acid or Rheodextran is not recommended. While undertaking epidural anaesthesia or analgesia, it is necessary to follow strictly the guidelines of the use of pharmacological thromboprophylaxis.     

Haemorrhagic Effect of Enoxaparin,a Low Molecular Weight Heparin: Comparison with Unfractionated Heparin in Humans

The haemorrhagic effects of unfractionated heparin (UFH) and the low molecular weight heparin (LMWH) enoxaparin were investigated and compared in the gastric mucosa (haemorrhage induced by biopsy) and skin (haemorrhage induced by Simplate) of 12 healthy volunteers. Administration of UFH and LMWH (given in a dose of 75 anti-Xa U/kg intravenously) increased median gastric bleeding time (3.5 min) and geometric mean blood loss (11.5 l) to 19 min (p = 0.00003) and 54.1 l (p = 0.0021) after UFH and to 13 min (p = 0.008) and 29.0 l (p = 0.275) after LMWH. Median skin bleeding time (4.25 min) increased to 6.0 min after UFH (p = 0.003) and to 6.75 min after LMWH (p = 0.0008). Mean heparin activity in plasma was 20% higher after LMWH than after UFH. The calculated gastric bleeding time to heparin activity ratio was significantly lower for LMWH than for UFH (0.05).     

Use of high intensity adjusted dose low molecular weight heparin in women with mechanical heart valves during pregnancy: a single-center experience

The use of standard dose low molecular weight heparin (LMWH) to anticoagulate women with mechanical valves in pregnancy is associated with morbidity and mortality. We conducted a prospective audit of the use of adjusted dose high intensity LMWH in 12 pregnancies in 11 women with prosthetic heart valves. LMWH ± low-dose aspirin was started at therapeutic-dose with monitoring of anti-Xa levels to achieve a target level of 1.0–1.2 IU/mL (0.8–1.2 in the first 3/12 pregnancies). This necessitated a mean increase in the dose of LMWH of 54.4% (SD±33.2) over initial dose. Eleven of 12 pregnancies resulted in live births, with one intrauterine fetal death at 37 weeks. One non-fatal valve thrombosis occurred at 26 weeks gestation associated with subtherapeutic anti-Xa levels. Three patients experienced major bleeding. This regime provides a therapeutic option for women with mechanical heart valves during pregnancy, provided anti-Xa levels are kept within the target range. These patients require close surveillance for bleeding and thrombotic complications within a multi-disciplinary setting.     

Fixed-dose versus adjusted-dose low molecular weight heparin for the initial treatment of patients with deep venous thrombosis

Patients with acute deep vein thrombosis (DVT) were treated with a body-weight independent dosage of 2 x 8000 aXa IU low-molecular-weight heparin (LMWH) Certoparin. After the subcutaneous administration of 8000 IU Certoparin, pharmacodynamic parameters did not differ between patients and healthy volunteers, and the AUC of the anticoagulant effects were not related to body weight. Two clinical trials demonstrated a greater regression of thrombi and a lower occurrence of recurrent venous thromboembolism (VTE), major bleeding, and mortality within 14 days of initial therapy compared with intravenous heparin. D-dimer decreased, and anti-Xa activity increased in those patients with a regression of thrombosis. The benefit of the reduced occurrence of recurrent VTE, major bleeding, and mortality was maintained up to 6 months. Major bleeding was not related to the body weight in either treatment group. Treatment of acute DVT in adults with fixed dose of 2 x 8000 aXa IU LMWH Certoparin is more effective and safer than heparin.