The British Society for Haematology Guidelines on the use and monitoring of heparin 1992: second revision. BCSH Haemostasis and Thrombosis Task Force

Perioperative management of laparoscopic surgery in a patient with protein S deficiency complications: A case report

Patients with protein S deficiency are prone to developing thrombosis. During laparoscopic surgery in patients with protein S deficiency, there is a risk of deep venous thromboembolism. In the present case, the patient was a 66-year-old man. He was diagnosed with colon cancer, and surgery was planned. Because of the presence of protein S deficiency, he required careful perioperative management for laparoscopic surgery. Surgery was successfully performed. On postoperative assessment, no thrombi were observed. Our approach of perioperative management might help in the treatment of patients with protein S deficiency.

Anticoagulation therapy in children

Thromboembolic disease (TED) is increasingly recognized as a major cause of morbidity and mortality in tertiary pediatrics. Children younger than 1 year of age and teenage girls are at greatest risk of thromboembolism. Although anticoagulation therapy is the treatment of choice for TED, the treatment strategy is often difficult, especially in children. Treatment relies largely on anticoagulation with heparin and warfarin. Recommendations for antithrombotic therapy in children have been loosely extrapolated from recommendations for adults; however, it is likely that optimal treatment of children with TED differs from adults because of important ontogenic features of hemostasis that affect both the pathophysiology of the thrombotic processes and the response to antithrombotic agents. Until recently, the primary treatment for TED has been unfractionated heparin (UFH) in conjunction with warfarin. Warfarin, the most commonly used oral anticoagulant, acts through inhibition of the vitamin K-dependent transcarboxylation reactions that convert precursors of clotting factors into their active form. Appropriate use of UFH and warfarin requires close patient monitoring and dosage adjustments to ensure tolerability and efficacy. In recent years, low molecular weight heparins (LMWH) have become available as alternatives to UFH and warfarin, for both the prevention and treatment of TED. Potentially, LMWH have significant advantages. They have superior pharmacokinetics, which results in minimal laboratory monitoring, offering important benefits to children with poor venous access. Based on available data, LMWHs are at least as effective and well tolerated as UFH, and are more convenient. Although LMWHs are more expensive than UFH, the expense is likely to be offset by savings from a reduced hospital stay.

Treatment and prophylaxis of venous thromboembolism during pregnancy

The treatment and prevention of deep vein thrombosis (DVT) and pulmonary embolism (PE) in pregnant patients is challenging for several reasons. Coumarins can cause embryopathy and other adverse effects in the fetus. Although unfractionated heparin and low-molecular-weight heparins, the cornerstones of initial therapy, are safe for the fetus, they can have significant maternal side effects, including osteoporosis and thrombocytopenia. Because they must be given parenterally, long-term administration is inconvenient. Further, although low-molecular-weight heparins probably cause less maternal osteoporosis and thrombocytopenia than unfractionated heparin, the appropriate dosing regimens for prevention and treatment of thrombosis during pregnancy have not been established. In addition, there is a paucity of reliable information on the incidence of venous thromboembolism and the risk of recurrent thrombosis during pregnancy. This paper briefly reviews the areas of controversy and provides recommendations for the treatment and prophylaxis of acute deep vein thrombosis and pulmonary embolism in pregnant patients.

Coagulation activation markers do not correlate with the clinical risk of thrombosis in pregnant women

OBJECTIVE

Because coagulation activation markers have been shown to indicate an increased risk of thrombosis, we tested whether thrombin-antithrombin III complexes and D-dimers correlated with the risk assessment in pregnant women on the basis of clinical data.

STUDY DESIGN

We divided a group of 261 pregnant women (305 pregnancies) into low- and high-risk groups according to the personal and family histories of thrombosis and the presence of a hereditary or an acquired thrombophilia. Women with a thrombotic event in the current pregnancy formed a separate group. All pregnancies with or without heparin therapy were closely monitored with thrombin-antithrombin III and D-dimer values for the entire course of the pregnancy. Retrospectively, the data were then correlated with the different groups and subgroups.

RESULTS

The course of the mean thrombin-antithrombin III values of all 305 pregnancies was close to or slightly above the upper cutoff line, whereas the D-dimer values were well within the normal range. Independent of heparin, there was no difference in the course of the thrombin-antithrombin III and D-dimer values between the low- and high-risk groups. Only women with ongoing thrombosis during pregnancy had significantly higher thrombin-antithrombin III and D-dimer values with or without heparin therapy. Among those individuals with elevated thrombin-antithrombin III or D-dimer values, there were no specific, recognizable patients who had elevated markers more often than others.

CONCLUSIONS

Thrombin-antithrombin III and D-dimer values do not correlate with a risk stratification assessed by clinical criteria. There are many women at low clinical risk who have elevated markers, and there are many women at very high clinical risk who have normal markers. Thus thromboprophylaxis would often be used inadequately if the indication were based on coagulation markers.

Dermatan sulfate versus unfractionated heparin for the prevention of venous thromboembolism in patients undergoing surgery for cancer. A cost-effectiveness analysis

BACKGROUND

In a recent clinical trial, dermatan sulfate was found to be more effective than unfractionated heparin (UFH), but equally well tolerated, for the prevention of deep vein thrombosis (DVT) after major surgery for cancer.

OBJECTIVE

To perform a cost-effectiveness analysis of dermatan sulfate versus UFH in this clinical setting.

DESIGN AND SETTING

This was a retrospective economic analysis using data from a randomised clinical trial, and was performed from the hospital perspective.

METHODS

Clinical event rates were extrapolated from the observed venographic DVT rates, using appropriate assumptions from the scientific literature. The economic effects of switching DVT prophylaxis from UFH to dermatan sulfate and the potential lives saved were assessed by a predictive decision model.

RESULTS

The per patient cost, including the burden of residual thromboembolic events and major bleeding complications, was estimated to be 154 euros (EUR) for dermatan sulfate and EUR185 for UFH (1998 values). With reference to a potential target population of 60,000 patients/year undergoing surgery for cancer in Italy, the total prophylaxis-associated cost was EUR9,258,000 for dermatan sulfate and EUR11,096,000 for UFH, whereas the potential deaths from prophylaxis failure were 204 and 392, respectively. This represented a saving of EUR1,838,000 and 188 potential lives per year with the dermatan sulfate option. The final costs and effects were mainly sensitive to variations in the rates of DVT and pulmonary embolism, and to the possible need for 1 extra day of hospitalisation because of the earlier preoperative initiation of dermatan sulfate prophylaxis.

CONCLUSION

Dermatan sulfate is more cost effective than UFH for the prevention of postoperative venous thromboembolism in patients with cancer. If the hospital stay needs to be prolonged, then the dermatan sulfate option may involve a small additional cost (EUR47) per potential life saved.

Safety of withholding heparin in pregnant women with a history of venous thromboembolism. Recurrence of Clot in This Pregnancy Study Group

BACKGROUND

Women with a history of venous thromboembolism may be at increased risk for venous thromboembolic events during pregnancy. In these women, the decision to give or withhold heparin in the antepartum period is controversial, because accurate estimates of the frequency of recurrent thromboembolic events if antepartum heparin is withheld are not available.

METHODS

We prospectively studied 125 pregnant women with a single previous episode of venous thromboembolism. Antepartum heparin was withheld, but anticoagulant therapy was given for four to six weeks post partum. Our primary objective was to determine the rate of antepartum recurrence of venous thromboembolism. Laboratory studies were performed to identify thrombophilia in 95 women.

RESULTS

Three of the 125 women (2.4 percent) had an antepartum recurrence of venous thromboembolism (95 percent confidence interval, 0.2 to 6.9 percent). There were no recurrences in the 44 women who had no evidence of thrombophilia and who also had a previous episode of thrombosis that was associated with a temporary risk factor. Among the 51 women with abnormal laboratory results or a previous episode of idiopathic thrombosis, or both, 3 (5.9 percent) had an antepartum recurrence of venous thromboembolism (95 percent confidence interval, 1.2 to 16.2 percent).

CONCLUSIONS

The risk of recurrent antepartum venous thromboembolism in women with a history of venous thromboembolism is low, and therefore routine antepartum prophylaxis with heparin is not warranted.

Treatment and prevention of venous thromboembolic disease in pregnancy

Pulmonary embolism is a major, but potentially preventable, cause of maternal mortality in North America and Europe. Because venous thromboembolism is an infrequent cause of maternal morbidity, there are few randomized clinical trials to guide clinical decision-making with respect to treatment, prevention, and evaluation of innovative management modalities such as low molecular weight heparin. This article focuses on the evidence supporting the current guidelines for the pharmacologic management of venous thromboembolic disease in pregnancy.

Outpatient Therapy of Deep Vein Thrombosis

The initial treatment of acute venous thrombosis using low-molecular-weight heparin (LMWH) in the outpatient setting has been shown to be feasible, effective, and safe for selected patients when compared with in-hospital treatment using continuous intravenous heparin. There will always be a significant population of patients, however, who require in-hospital treatment with either LMWH or unfractionated heparin. It is clear that substantial cost savings can be achieved with the out-of-hospital treatment of venous thrombosis, but several logistic problems require solutions before these savings can be realized. Numerous strategies, including the development of anticoagulation management clinics, are under review, especially for the management of arterial or venous thrombosis with LMWH. It is likely that the outpatient management of venous thrombosis will vary, depending on the referral base of the institution involved.

Hazards of heparin: allergy, heparin-induced thrombocytopenia and osteoporosis

Heparin is the commonest mode of thromboprophylaxis used in pregnancy. It does not cross the placenta but has potential adverse effects on the mother, of which the most important is heparin-induced osteoporosis. The hazards of heparin, including bleeding, skin reactions, heparin-induced thrombocytopenia and osteoporosis are discussed and the relevant literature reviewed. Low-molecular-weight heparins have certain advantages over standard unfractionated heparins, especially in obstetrics. Their longer half-life and increased bioavailability enable once-daily injections, making them more convenient and acceptable. They are as effective as standard heparin but have a theoretically more favourable side-effect profile, providing less anticoagulant relative to antithrombotic activity. Current evidence suggests a lower incidence of heparin-induced thrombocytopenia. A reduced risk of osteoporosis is suggested but not yet proven. Although thrombo-embolism is currently the leading cause of maternal mortality in the UK, antenatal heparin prophylaxis is not given to all women with previous thrombo-embolism because of continued fears concerning heparin-induced osteoporosis. A protocol is presented with guidelines for different levels of obstetric prophylaxis depending on the perceived level of risk.

Current concepts of anticoagulant therapy in pregnancy

The optimal use of anticoagulants during pregnancy will continue to be controversial until appropriate randomized controlled and prospective trials with adequate sample sizes are completed. The relative low frequency of thromboembolic events, the concerns about maternal and fetal safety of both treatment and withholding treatment, and the reservations about prospectively enrolling pregnant women in treatment trials has sadly dissuaded the appropriate study of this life-threatening condition. North American trials that enroll pregnant women to evaluate the efficacy of LMWH are of preeminent importance owing to their superior bioavailability, ease in dosing, longer half-life, and side effect profile. Similarly, trials evaluating the optimal management of women of childbearing age with valvular disease are critical to reduce the considerable maternal and fetal morbidity and mortality associated with these pregnancies. Such definitive studies will need to be multicenter in design and it is hoped that the National Institutes of Health initiative to enroll pregnant women in clinical trials will at last be realized in the near future.

Economic evaluation of the use of nadroparin in the treatment of deep-vein thrombosis in Switzerland

OBJECTIVE

To compare the cost implications, from the payer's perspective, of the use of nadroparin instead of unfractionated heparin in the initial treatment of deep-vein thrombosis.

DESIGN

Cost-minimization study.

SETTING

Switzerland.

MATERIAL

Survey of clinical practice in six Swiss hospitals used to model three treatment regimens.

MAIN OUTCOME MEASURES

Cost of treatment ($ US) per patient.

RESULTS

Treatment with nadroparin instead of unfractionated heparin would reduce costs by $153 per patient. Treatment with nadroparin instead of subcutaneous unfractionated heparin would reduce costs by $109 per patient.

CONCLUSIONS

The cost of initial treatment of deep-vein thrombosis is considerably lower with nadroparin than with either of the alternative regimens. Nadroparin reduces costs through greater ease of administration and by reducing the amount of laboratory monitoring. Treatment with nadroparin might also allow patients to be discharged from the hospital more quickly than is possible with intravenous infusion of unfractionated heparin.

Prevention and treatment of venous thromboembolism

All patients at moderate to high risk for the development of venous thromboembolism should receive prophylaxis. The approaches of proven value include low dose heparin, low molecular weight heparin, oral anticoagulants and intermittent pneumatic compression. The use of one of the cited heparin nomograms will ensure that all patients are rapidly brought within the therapeutic range. Because of the varying sensitivities of thromboplastins, each laboratory should establish a therapeutic range using the activated partial thromboplastin time (APTT) which will correspond to 0.2 to 0.4 U/ml of heparin. Constant vigilance and a high level of suspicion are necessary to establish the clinical diagnosis of heparin-induced thrombocytopenia, and to institute appropriate therapy. Physicians should be aware of the sensitivity of the thromboplastin being used in the performance of the International Normalised Ratio (INR). Care must be taken to ensure that patients are maintained within the target therapeutic range for INR (in most cases 2 to 3) by frequent determination of the INR and appropriate adjustments of warfarin dosage. Low molecular weight heparin is the recommended approach to the initial management of venous thromboembolism where these agents are available. Patients with an acute episode of venous thromboembolism should receive warfarin therapy for at least 3 months. At the present time it is reasonable to treat the first recurrence with oral anticoagulants for a period of 12 months and indefinitely for more than 1 recurrence. For selected patients with acute massive pulmonary embolism, thrombolytic therapy with one of the available agents is recommended. However, the role of thrombolytic therapy in patients with proximal venous thrombosis remains unclear. In selected patients with acute venous thromboembolism who have contraindications to anticoagulant therapy or who-have objectively documented recurrent disease while on adequate therapy, the insertion of an inferior vena cava filter is recommended.

Management of suspected acute venous thromboembolism in a general and maternity hospital

A retrospective study of the management of patients with suspected acute deep venous thrombosis (DVT) and pulmonary thromboembolism (PTE) in a general and maternity hospital was conducted over a two month period in 1992. Ninety six patients with suspected DVT/PTE were identified, of whom only two were pregnant. Forty four patients had suspected DVT and confirmatory investigations were performed in 84%. The most common risk factor for DVT was intra-venous drug (IVD) use. Unfractionated heparin was prescribed to all patients except one with acute DVT at an average daily dose of 25,000 iu. In patients receiving heparin, 68% had measurements of the activated partial thromboplastin time (APTT) ratio and on 38% of occasions the result was subtherapeutic. Complications of heparin therapy were infrequent. Fifty two patients had suspected PTE and 50 underwent ventilation/perfusion (V/Q) scanning. No patient underwent pulmonary angiography. The management of patients with normal, low and high probability V/Q scans was in keeping with the guidelines, but only 8% [corrected] of patients with an intermediate V/Q scan result had further investigations and 33% received heparin. This study revealed suboptimal anticoagulation of patients with acute DVT and scope for improvement in the management of patients with an intermediate V/Q scan result.

Heparin levels to guide thromboembolism prophylaxis during pregnancy

OBJECTIVE

Our purpose was to determine the dose of heparin required in pregnant women to achieve the same heparin levels as standard doses of 5000 units given subcutaneously every 12 hours in the nonpregnant population.

STUDY DESIGN

Fourteen pregnant women placed on heparin prophylaxis for a history of thromboembolism had blood drawn for 64 anti-Xa level determinations in the second and third trimesters. Heparin doses were adjusted in an attempt to achieve a midinterval or peak level of 0.05 to 0.25 U/ml, which corresponds to the range seen in nonpregnant patients given standard doses of 5000 units subcutaneously every 12 hours.

RESULTS

A standard heparin dose of 5000 units given subcutaneously every 12 hours was inadequate to achieve the desired range in this pregnant population. In five of nine second-trimester pregnancies 7500 units given subcutaneously every 12 hours was inadequate to attain this range. In six of 13 third-trimester pregnancies, > 10,000 units subcutaneously every 12 hours was needed.

CONCLUSIONS

Heparin requirements may increase and are highly variable in patients during pregnancy. Until appropriate clinical outcomes trials can determine optimal dosing, measuring anti-Xa activity may be useful to guide therapy.

Thrombosis and embolism

Prevention offers the best approach to limiting morbidity and mortality from deep vein thrombosis and pulmonary embolism in obstetric patients. The use of anticoagulant drugs during pregnancy, however, can be problematic, from the maternal or the fetal point of view. Deciding on the best management is further limited by the lack of controlled clinical trials in the obstetric setting. From the data available, it can be recommended that anticoagulant prophylaxis should be targeted at groups of patients at high risk of thrombosis during pregnancy and the puerperium. Heparin is the agent of choice in most situations during pregnancy for the prophylaxis of venous thrombosis, while warfarin is still the most effective agent for the prevention of systemic embolism from artificial cardiac valves. Prophylactic measures against venous thrombosis are probably underused in the puerperium. Controlled clinical studies are urgently required to optimize prophylaxis of venous thromboembolism associated with pregnancy, and large studies may be more feasible in the puerperium when the incidence of thromboembolism is highest.

Maintaining blood flow in the extracorporeal circuit: haemostasis and anticoagulation

OBJECTIVES

To review the methods and developments in maintaining extracorporeal circuits in critically ill patients.

DESIGN

The review includes details of the pathophysiological processes of haemostasis and coagulation in critically ill patients, methods of maintaining blood flow in the extracorporeal circuit and methods of monitoring anticoagulation agents used.

SETTING

Information is relevant to the management of critically ill patients requiring extracorporeal renal and respiratory support and cardiopulmonary bypass.

CONCLUSIONS

Heparin is the mainstay of anticoagulation for the extracorporeal circuit although the complex abnormalities of the coagulation system in critically ill patients are associated with a considerable risk of bleeding. Alternative therapeutic agents and physical strategies (prostacyclin, low molecular weight heparin, sodium citrate, regional anticoagulation, heparin bonding and attention to circuit design) may reduce the risk of bleeding but expense and difficulty in monitoring are disadvantages.

Role of Low Molecular Weight Heparins in the Prevention and Treatment of Venous Thromboembolism after Surgery

Objective:

To examine the effectiveness of low molecular weight heparins (LMWHs) in the prevention and treatment of deep venous thrombosis (DVT) and pulmonary embolism (PE) following surgery.

Design:

A review of the results of randomized controlled trials of LMWHs in which LMWH was compared with placebo, dextran or unfractionated heparin.

Methods:

Published data from journals indexed in Index Medicus (Medline CD Rom) since 1984 or found in the reference lists of such journals.

Main outcome measures:

Incidence of DVT as assessed by isotope scanning and/or venography and the incidence of PE and bleeding complications.

Results:

Prophylaxis with LMWH causes a significant reduction in the incidence of DVT compared with placebo, dextran and unfractionated heparin in high-risk patients undergoing orthopaedic operations, but there is no conclusive evidence that they are better than unfractionated heparin in general surgery. There was inconclusive evidence that LMWHs reduced the incidence of PE compared with dextran or unfractionated heparin. LMWHs were at least as safe as unfractionated heparin in terms of major haemorrhage or postoperative blood loss.

Conclusions:

Current evidence suggests the use of LMWHs in high-risk orthopaedic patients as a means of thromboprophylaxis is cost-effective. More trials are necessary to justify the use of LMWHs over unfractionated heparin in general surgery.