Rationale for development of low-molecular-weight heparins and their clinical potential in the prevention of postoperative venous thrombosis

The neutralization of heparan sulfate by heparin-binding copolymer as a potential therapeutic target

Besides regulating ligand–receptor and cell–cell interactions, heparan sulfate (HS) may participate in the development of many diseases, such as cancer, bacterial or viral infections, and their complications, like bleeding or inflammation. In these cases, the neutralization of HS could be a potential therapeutic target. The heparin-binding copolymer (HBC, PEG41-PMAPTAC53) was previously reported by us as a fully synthetic compound for efficient and safe neutralization of heparins and synthetic anticoagulants. In a search for molecular antagonists of HS, we examined the activity of HBC as an HS inhibitor both in vitro and in vivo and characterized HBC/HS complexes. Using a colorimetric Azure A method, isothermal titration calorimetry and dynamic light scattering techniques we found that HBC binds HS by forming complexes below 200 nm with less than 1 : 1 stoichiometry. We confirmed the HBC inhibitory effect in rats by measuring activated partial thromboplastin time, prothrombin time, anti-factor Xa activity, anti-factor IIa activity, and platelet aggregation. HBC reversed the enhancement of all tested parameters caused by HS demonstrating that cationic synthetic block copolymers may have a therapeutic value in various disorders involving overproduction of HS.

The neutralization of heparan sulfate (HS) by a heparin-binding copolymer (HBC) could be a promising treating option for bacterial or viral infections or bleeding related to overproduction of HS in cancer or other diseases.

Prevention of deep-vein thrombosis in ambulatory arthroscopic knee surgery: A randomized trial of prophylaxis with low--molecular weight heparin

PURPOSE

The risk of deep vein thrombosis (DVT) in patients undergoing arthroscopic knee surgery is not well known. The purpose of this study was to determine the incidence of DVT, to demonstrate the efficacy of a perioperative and postoperative prophylaxis against thromboembolism with use of low--molecular weight heparin (LMWH), and to show the safety and feasibility of LMWH administration.

TYPE OF STUDY

Prospective, single-blind, randomized clinical trial.

METHODS

There were 218 consecutive outpatients scheduled for ambulatory arthroscopic knee surgery eligible. Of these, 130 patients were randomized to a treatment group with LMWH (dalteparin: 2,500 IU less-than-or-equal70 kg and 5,000 IU >70 kg, started perioperatively and given once daily for 4 weeks; n = 66) and a control group (n = 64) with no prophylaxis. To detect DVT, all patients underwent bilateral compression ultrasonography before and 12 and 31 days after surgery.

RESULTS

Among the 130 patients studied, thromboembolism was significantly lower in the treatment than in the control group: 1 of 66 (1.5%) versus 10 of 64 (15.6%); 95% confidence interval, 7.8% to 26.8%; P =.004. Eighty percent of DVT occurred within the first 14 postoperative days. No severe side effects of LMWH were observed. Only 5% of patients refused continued subcutaneous LMWH injections.

CONCLUSIONS

In patients undergoing ambulatory arthroscopic knee surgery without antithrombotic prophylaxis, the risk of DVT is high. Perioperative and postoperative prophylaxis with dalteparin is an effective and safe means of reducing this risk.

Thromboprophylaxis, coagulation disorders, and regional anaesthesia

The surgery and trauma-induced modulation of the coagulation system includes a considerable risk of perioperative thromboembolic complications unless effective thromboprophylactic treatment is given. In the present survey the patient at risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) is characterized and the documented efficacy of different currently used thromboprophylactic regimens is summarized. Systemic thromboprophylactic treatment may include a risk of an increased bleeding tendency which may lead to haemorrhagic complications. In patients with a coagulation abnormality or in patients receiving anticoagulants for perioperative thromboprophylaxis there is a fear among anaesthesiologists that the use of regional anaesthesia (spinal or epidural) may be associated with spinal haemorrhagic complications, i.e. with spinal haematoma formation leading to compression of the spinal cord and severe neurologic sequelae. Present aspects on the risk of spinal haematoma formation at the combined use of pharmacological thromboprophylactic regimens and spinal or epidural anaesthesia/ analgesia are therefore summarized. Pregnancy is associated with changes in the haemostatic system, which in the preeclamptic or eclamptic patient may be rather pronounced and constitute a clinical problem since regional anaesthetic techniques are often preferred for obstetric anaesthesia/analgesia. The specific problems to be considered prior to the choice of regional anaesthesia/analgesia for a parturient with a suspected coagulation disorder are therefore commented on in more detail. Finally, recommendations are given for safe spinal and epidural analgesic and anaesthetic routines in patients with potential haemostatic disturbances due to thromboprophylactic treatment with anticoagulants or bleeding disorders.

Post-stent management with a pneumatic groin compression device and self injected low molecular weight heparin

BACKGROUND

The benefits of intracoronary stent implantation are offset by an increased risk of complications at the arterial puncture site and a prolonged hospital stay. Much of this morbidity can be attributed to the generally perceived need to achieve systemic anticoagulation after stent implantation.

AIM

To test a simplified protocol for post-stent management using the Femostop pneumatic groin compression device and low molecular weight (fractionated) heparin (LMWH) administered by subcutaneous injection.

PATIENTS

A case series of 100 consecutive patients, with stable angina pectoris, undergoing coronary stenting for a suboptimal result after conventional balloon angioplasty.

METHODS

All patients were managed with a new post-stent protocol using the Femostop pneumatic groin compression device and LMWH. The incidence of complications and the length of hospital stay were recorded.

RESULTS

The clinical course was uncomplicated in 92 patients and their discharge from hospital was achieved on the first post-procedural day for 44 patients and on the second for the remaining 48. The rate of vascular or bleeding complications was 6%.

CONCLUSIONS

LMWH administered by subcutaneous injection may provide a practical and effective alternative to the use of intravenous heparin when systemic anticoagulation is used after stent implantation.

Altering the course of proliferative nephritides: the challenge of the 1990s

There is considerable evidence based on experimental pathology that heparin/heparinoids will benefit the course of the various forms of human proliferative nephritis. An alternative to heparin may be pentosan polysulphate. Another possibility is the infusion of prostaglandin E1 because of its anti-inflammatory and potentially antiproliferative actions. Both these approaches mimic natural pathophysiological control mechanisms.

Deep vein thrombosis in stroke patients: An overview

Deep vein thrombosis (DVT) is prevalent both in the acute and the later phases of stroke. From previous studies using (125)I fibrinogen uptake, its peak incidence appears to occur during the first 10 days of stroke. Using venography and impedance plethymography, its prevalence is still high (between 30% and 40%) 1 1/2 to 6 months after stroke. The incidence of pulmonary embolism appear to diminish after the acute phase of stroke. Venous stasis is a widely accepted factor in the cause of DVT. More recently, venous injury as endothelial damage from excessive venodilation has been postulated. Increased venous size in hemiplegic limb has been reported. Further studies as to the role of decreased venous velocity and increased venous size and the effect of various modalities influencing these effects are needed. Routine screening of stroke patients appears indicated, but what protocol should be followed has yet to be determined. Selective screening by stratifying patients as to their clinical risk may be appropriate if found safe and cost-effective. Prophylactic treatment should be initiated in patients who are at increased risk of DVT. The prophylaxis of venous thrombosis in stroke patients remains uncertain. The use of low-molecular heparin may be a promising option if it is proven safe, efficacious, and causes less bleeding. Other prophylactic methods remain to be investigated.

An overview of venous thromboembolism prophylaxis

This symposium reviewed the risk factors and problems associated with venous thromboembolism in surgical patients, especially those patients having total hip replacement. The importance of venous thromboembolism prophylaxis was emphasized by a theoretical analysis indicating that venous thromboembolism in patients having hip replacement not only saves lives but is also effective. A discussion of the pharmacology of low-molecular-weight heparin (LMWH) included a review of its role, clinically and experimentally, in venous thromboembolism prophylaxis. Three of the discussants presented their favorable experiences with LMWH in reducing the incidence of venous thromboembolism in patients having hip replacement. It can be concluded that LMWH does reduce the incidence of venous thromboembolism in patients having hip replacement without causing an increase in blood loss. If its effectiveness and safety remain substantiated, LMWH may soon become the preferred agent for venous thromboembolism prophylaxis.