Antithrombotic therapy for venous thromboembolic disease

Antithrombotics and new interventions for venous thromboembolism: Exploring possibilities beyond factor IIa and factor Xa inhibition

Direct oral anti-activated factor X and antithrombin agents have largely replaced vitamin K antagonists as the standard of care in treatment of venous thromboembolism. However, gaps in efficacy and safety persist, notably in end-stage renal disease, implantable heart valves or assist devices, extracorporeal support of the circulation, and antiphospholipid syndrome. Inhibition of coagulation factor XI (FXI) emerges as a promising new therapeutic target. Antisense oligonucleotides offer potential advantages as a prophylactic or therapeutic modality, with one dose-finding trial in orthopedic surgery already published. In addition, monoclonal antibodies blocking activation and/or activity of activated factor XI are investigated, as are small-molecule inhibitors with rapid offset of action. Further potential targets include upstream components of the contact pathway such as factor XII, polyphosphates, or kallikrein. Finally, catheter-directed, pharmacomechanical antithrombotic strategies have been developed for high- and intermediate-risk pulmonary embolism, and large randomized trials aiming to validate their efficacy, safety, and prognostic impact are about to start.

A haemodynamic concept in the management of superficial non-saphenous vein thrombosis

Objective

Through the analysis of the haemodynamic model in the development of superficial non-saphenous vein thrombosis, the authors propose a therapeutic approach which is based on an ultrasound study of the superficial and perforating venous system of the lower limbs.

Methods

The authors propose the development of a haemodynamic model in the evolution of superficial non-saphenous vein thrombosis. They analyse three cases to highlight the importance of venous haemodynamics in the development of this condition and its possible complications, such as the progression of thrombosis in the deep vein system through the perforating veins.

Results

The evolution of a thrombosis in the venous network of the lower limbs from the peripheral collateral veins to the deep vein can be haemodynamically explained through this model involving the perforating vein system.

Conclusions

In the management and treatment of superficial non-saphenous vein thrombosis, it is essential to perform an accurate ultrasound evaluation of the superficial venous system, the deep venous system and the perforator system, according to venous haemodynamic principles. This study proposes a new model to be used in the ultrasonic management and treatment of superficial non-saphenous vein thrombosis.

Analyzing a Health-System's Use of Unfractionated Heparin to Ensure Optimal Anticoagulation

Background:

Although unfractionated heparin (UH) dosing nomograms have proven to be superior to standard dosing, the latter remains the mainstay at our institution. We hypothesize that the incorporation of technology integrated with a decision support algorithm will facilitate the use of a UH nomogram by clinicians.

Objective:

To critically appraise the steps involved with the use of UH, create a decision support algorithm to aid in the management of UH, and determine whether the use of this algorithm can improve achievment of rapid and safe anticoagulation compared with the current standard of care.

Methods:

We analyzed the steps involved with the use of UH and subsequently reviewed the medical literature for risk factors for bleeding that patients may harbor when initiating UH. Based on this information, we designed a computerized physician order entry (CPOE), factor-based, weight-adjusted decision support algorithm with the primary goal of minimizing the risk of bleeding while optimizing and ensuring optimal anticoagulation. We compared the CPOE strategy with our current standard of care.

Results:

The CPOE factor–based dosing strategy significantly improved the rates and decreased the time to achieving an initial activated partial thromboplastin time (aPTT) that was ≥60 seconds compared with the control group. At the time of first aPTT measurement, the CPOE factor-based group achieved a 92.9% therapeutic rate compared with the standard heparin dosing group, which achieved a 60.8% therapeutic rate (p < 0.01).

Conclusions:

The institution of a CPOE factor-based dosing strategy in collaboration with pharmacists' interventions optimizes anticoagulation treatment with UH.

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux.

Oral drug delivery systems using chemical conjugates or physical complexes

Oral delivery of therapeutics is extremely challenging. The digestive system is designed in a way that naturally allows the degradation of proteins or peptides into small molecules prior to absorption. For systemic absorption, the intact drug molecules must traverse the impending harsh gastrointestinal environment. Technologies, such as enteric coating, with oral dosage formulation strategies have successfully provided the protection of non-peptide based therapeutics against the harsh, acidic condition of the stomach. However, these technologies showed limited success on the protection of therapeutic proteins and peptides. Importantly, inherent permeability coefficient of the therapeutics is still a major problem that has remained unresolved for decades. Addressing this issue in the context, we summarize the strategies that are developed in enhancing the intestinal permeability of a drug molecule either by modifying the intestinal epithelium or by modifying the drug itself. These modifications have been pursued by using a group of molecules that can be conjugated to the drug molecule to alter the cell permeability of the drug or mixed with the drug molecule to alter the epithelial barrier function, in order to achieve the effective drug permeation. This article will address the current trends and future perspectives of the oral delivery strategies.

Management of pregnant women with cardiac diseases at potential risk of thromboembolism--experience and review

Over a 7-year period, the chart records of six pregnant women with cardiac diseases at potential risk of thromboembolism were reviewed. All six patients survived and recovered well eventually. LMWH and beta-adrenergic blocker were effective to deal with atrial fibrillation. Digitalis and dobutamine were beneficial to prevent heart failure resulted from degenerated porcine valve and dilated cardiomyopathy. In a patient with mechanical mitral valve, low-dose warfarin did not cause fetal malformation, and was effective to prevent thrombus formation. Protamine sulfate was safely administered to neutralize intravenous heparin effect before vaginal delivery. Life-threatening postpartum pulmonary hemorrhage occurred as a result of pulmonary hypertension with an aberrant right pulmonary artery, absolutely necessitating a long-term cardiopulmonary bypass resuscitation. Patient with primary pulmonary hypertension gave birth safely with forceps assistance under epidural anesthesia. From literatures reviewed and successful experiences presented here, prenatal correction of the underlying cardiac malformation, precise switch of anticoagulant administration, optimizing cardiac function, early delivery prior to heart failure, postpartum fluid restriction, minimized peripartum blood loss, and meticulously intensive cares are essential to achieve satisfactory outcomes.

A newly developed oral heparin derivative for deep vein thrombosis: Non-human primate study

The development of orally active heparin will have tremendous clinical importance since it can be used to effectively prevent deep vein thrombosis (DVT) in a long-term chronic treatment. We developed in this study a new orally active heparin derivative (Db-LHD), which has heparin chemically conjugated with deoxycholic acid and DMSO molecules by secondary interactions. Db-LHD was prepared in the powder form in soft capsules. When we administered Db-LHD capsules to monkeys, its oral physiological availability was increased up to 16.6%. The maximum anti-FXa activity at 5 mg/kg of Db-LHD was more than twice the minimum effective anti-FXa activity (MEC, 0.1 IU/mL) for preventing DVT, and the anti-FXa activity in plasma was maintained for 10 h above the MEC in monkeys. Also, we evaluated anti-thrombogenic effect of Db-LHD in a rat thrombosis model. A subcutaneous administration of enoxaparin (100 IU/kg), which was the highest recommended dose for the prevention of venous thromboembolism, reduced thrombus formation by 38.9+/-14.2%. On the other hand, 5 mg/kg (425 IU/kg) of orally administered Db-LHD reduced thrombus formation by 51.0+/-2.0. We propose a new orally active heparin, Db-LHD, in a solid dosage form to effectively prevent DVT and PE.

The quality of oral anticoagulant therapy and recurrent venous thrombotic events in the Leiden Thrombophilia Study

BACKGROUND

The International Normalized Ratio (INR) target range is a relatively narrow range in which the efficacy of oral anticoagulant treatment, i.e. prevention of extension and recurrence of thrombosis, is balanced with the risk of hemorrhagic complications. Over the years, different INR target ranges have been implemented for individual indications, depending on their thrombotic potential. In most of the studies defining these INR targets, the treatment of the patients was aimed at a certain INR range, but in the analysis no account was taken of the time that the patients spent within this range in reality.

METHODS

The Leiden Thrombophilia Study (LETS) is a population-based case-control study on risk factors for venous thrombosis, in which many genetic and acquired factors have been investigated. Our aim was to investigate the effect of the quality of the oral anticoagulant therapy for the initial venous thrombosis and its relationship with recurrence of thrombosis. Quality of anticoagulation was defined as the time spent at various INR levels during treatment, and we focused on the effect of sustained intensities above a certain INR in preventing recurrences later on.

RESULTS

Two hundred and sixty-six patients with a total follow-up of 2495 patient-years were studied. The mean duration of the initial anticoagulant therapy was 194.5 days (range 48-4671). During follow-up, 58 recurrences were diagnosed (cumulative recurrence rate of 21.8% over 9 years). The mean INR during initial therapy was 2.90, with 90.3% [95% confidence interval (CI) 88.4-92.3%] of the time being spent above an INR of 2.0, and 39.1% (95% CI 35.5-42.7%) above an INR of 3.0. Patients who spent more time below the target range, or who had a shorter duration of anticoagulation, did not experience a higher risk of recurrence after the initial period of anticoagulation had passed.

CONCLUSION

Provided that oral anticoagulant treatment is adequately managed, according to international guidelines, recurrent thrombosis cannot be ascribed to variation in the primary treatment. Further attempts to reduce the risk of recurrence should therefore be aimed at identifying other explanatory factors, and subsequently fine-tuning the target ranges.

Absorption study of deoxycholic acid-heparin conjugate as a new form of oral anti-coagulant

The oral delivery of macromolecules is a topic of much interest as this would undoubtedly improve patient acceptance and compliance with chronic regimens. Heparin and insulin are perhaps among the first candidates that should be considered for oral macromolecule delivery systems. Heparin is the most potent anti-coagulant known for the prevention of deep vein thrombosis and pulmonary embolism, and an orally active heparin would undoubtedly effectively reduce chronic thrombotic events. Here, we report on the development of an orally administrable chemical conjugate of heparin and hydrophobic deoxycholic acid (DOCA), which we refer to as LHD. LHD was pre-formulated with dimethyl sulfoxide (DMSO) as solubilizer to further improve its oral bioavailability (9.1% in monkey). LHD was found to be absorbed mainly in the jejunum and ileum of the small intestine, although it is in the ileum that the absorption is most notable. From the mechanism studies of LHD absorption using Caco-2 cell monolayers for mimicking the intestine, we found that LHD highly permeated by passive diffusion through the transcellular route and its permeation was partially affected by bile acid transporters. This study demonstrates the feasibility of chemically modified heparin for long-term oral administration as an effective therapy for venous thromboembolism in clinical trials.

Site and clinical outcome of deep vein thrombosis of the lower limbs: an epidemiological study

Clinical outcomes of patients diagnosed with venous thromboembolic disease (VTED) have rarely been assessed on large series of patients from single institutions. This was work based on our practice to routinely screen all suspected pulmonary embolism (PE) and deep venous thrombosis (DVT) patients with bilateral proximal and distal venous US was designed to evaluate survival, recurrence and cancer occurrence in patients diagnosed with symptomatic or asymptomatic DVT and to assess their relationship with the site of the DVT (proximal vs. distal, bilateral vs. unilateral). Our study is based on the cross-matching of the VTED register of the Grenoble University Hospital with the local Cancer Register and community mortality data. Survival analyses were performed with the Kaplan-Meier method; prognostic variables were tested using the log-rank test. A total of 1913 patients with a DVT of the lower limbs from 1993 to 1998 were included (57% women; mean age, 69 years). Of these, 1018 patients were diagnosed with proximal DVT (156 bilateral) and 895 distal DVT (112 bilateral). PE was associated in 760 patients. Patients with PE and no detected DVT were not included. At 2 years, adjusted survival rates were 80% in patients with unilateral-distal DVT, 67% in bilateral-distal, 72% in unilateral-proximal and 65% in bilateral-proximal DVT patients. The cumulated VTED recurrence rates were 7.7% in unilateral-distal DVT, 13.3% when DVT was bilateral-distal, 14% when unilateral-proximal and 13.2% when bilateral-proximal. The rate of new cancer was 6.4% in unilateral-distal DVT, 10.8% when it was bilateral-distal, 6.5% when unilateral-proximal and 6.1% when bilateral-proximal. Based on a large series of unselected patients, our results show that the site of the DVT and principally the bilaterality provides important prognostic information that may be used in the setting up of medical strategies.

Outpatient treatment of venous thromboembolic disease based in an emergency department

PURPOSE

The efficacy, safety, and patient satisfaction of an emergency department (ED)-based outpatient program providing treatment for venous thromboembolic disease (VTD) were studied.

METHODS

A prospective cohort study of patients enrolled in a hospital outpatient VTD treatment program was conducted from June 1999 to September 2003. Endpoints included recurrent VTD at three and six months following discharge from the program, minor and major bleeding, and thrombocytopenia during the acute phase of therapy. Patient satisfaction was assessed with an 18-question survey that was mailed to all patients following discharge from the program.

RESULTS

A total of 162 patients were included. Of the 142 evaluable patients, no patient experienced recurrent VTD at three months, while at six months, 2 patients (1.4%; 95% confidence interval [CI], 0.2-5.0%) had recurrence. No patient experienced major bleeding or thrombocytopenia, while 4 (2.5%; 95% CI, 0.8-6.2%) had minor bleeding. Ninety-seven percent of the patients were comfortable having their condition treated on an outpatient basis, and 85.1% felt it was more convenient to return to the hospital daily for medications and assessment than to be admitted to the hospital. Overall, 97.7% of the respondents were satisfied or very satisfied with the treatment received in the outpatient program, and 94.0% said they would enroll again if future treatment was indicated.

CONCLUSION

An ED-based outpatient VTD treatment program was safe and effective and appeared to achieve a high level of patient satisfaction.

Low molecular weight heparin in pregnancy: current issues

Low molecular weight heparin (LMWH) is now the most commonly used anticoagulant for prophylaxis and treatment of venous thromboembolism in pregnancy and the puerperium in the UK. The reliable pharmacokinetics of LMWHs and their long half-life, resulting in the need for less frequent injections than unfractionated heparin (UFH), makes them attractive for practical use in the 9 months of pregnancy. Widespread use over the last 10 years has shown that LMWHs are safer than UFH in pregnancy. There is, however, poor consensus and wide disparity of views among experts with regard to the appropriate dose for the varying indications, the duration of treatment, and whether and how LMWH should be monitored because of the lack of an evidence base. These areas of uncertainty reflect the fact that clinical practice has grown largely through the publication of small trials, observational studies, personal experience and anecdote. Good clinical trials are urgently required.

The association between air travel and deep vein thrombosis: systematic review & meta-analysis

Background

Air travel has been linked with the development of deep vein thrombosis (DVT) since the 1950s with a number of plausible explanations put forward for causation. No systematic review of the literature exploring this association has previously been published.

Methods

A comprehensive search was undertaken (Data bases searched were: MEDLINE, EMBASE, Cochrane Library) for studies that estimated both the incidence and the risk of DVT in air travellers relative to non-air travellers.

Results

In total 254 studies were identified but only six incidence studies and four risk studies met inclusion criteria justifying their use in a systematic review. Incidence of symptomatic DVT ranged from (0%) in one study to (0.28%) which was reported in pilots over ten years. The incidence of asymptomatic DVT ranged from (0%) to (10.34%). Pooled odds ratios for the two case control studies examining the risk of DVT following air travel were 1.11 (95% CI: 0.64–1.94). Pooled odds ratios for all models of travel including two studies of prolonged air travel (more than three hours) were 1.70 (95% CI: 0.89–3.22).

Conclusion

We found no definitive evidence that prolonged (more than 3-hours) travel including air travel, increases the risk of DVT. There is evidence to suggest that flights of eight hours or more increase the risk of DVT if additional risk factors exist.

Dosing errors may impact the risk of rt-PA for stroke: the multicenter rt-PA acute stroke survey

Intravenous recombinant tissue plasminogen activator (rt-PA) is given for acute ischemic stroke using a weight-based dosing regimen, and potential medication dosing errors may impact the relative risks and benefits of this therapy. Weight is frequently estimated by the patient, the family, the nurse, or the treating physician. Discrepancies between actual and estimated weight result in an incorrect dose, but errors of this type have not been previously studied in clinical practice. We hypothesized that such errors may impact the risks and benefits of rt-PA for stroke. The Multicenter rt-PA Acute Stroke Survey included data on 1205 acute stroke patients treated in routine clinical practice with intravenous rt-PA. We calculated the actual unit dose (in mg/kg) by dividing the dose of rt-PA given by the actual weight, and correlated this with risk of intracerebral hemorrhage (ICH) and likelihood of good recovery (modified Rankin score of 0 or 1). Seven hundred and sixty-nine patients (64%) had data on both weight and rt-PA dosage. Forty-one patients (5.4%) had a symptomatic hemorrhage while 51 (6.6%) had an asymptomatic hemorrhage. There were non-significant trends towards increased risk of any ICH as the degree of overdosage increased, particularly in the highest dose quintile compared to the four lower quintiles (15.8% v 11.0%, P = .097). Adjustment for age, baseline NIHSS, and major early computed tomography (CT) changes strengthened this association (16.5% v 9.3%; P = .025). There was no association between actual dose and likelihood of good recovery (P = .57). Overdosage of rt-PA cause by an overestimation of weight resulted in a modest increase in the risk of ICH in the highest quintile, but there did not appear to be any reduction in effectiveness caused by underdosing. Every effort should be made to obtain the most accurate weight.

Simultaneous testing of the heparin effect on the soluble phase and platelet component of hemostasis

BACKGROUND

This study assessed the anticoagulant effect of heparin on both platelet activity and soluble phase coagulation.

METHODS AND RESULTS

Blood samples were collected from 32 patients undergoing cardiac catheterization before and 5 minutes after a heparin injection (2000 U). Activated clotting time (ACT), activated partial thromboplastin time (aPTT), and whole blood platelet aggregation [adenosine diphosphate (ADP) and collagen] were compared with the flow device variables platelet hemostasis time (PHT) and collagen-induced thrombus formation (CITF). Before heparin, all patients had a normal aPTT and all but 1 had a normal ACT. After heparin, all patients showed a prolonged aPTT and ACT. In contrast, the flow device showed considerable variability after heparin. Only 47% of patients increased both PHT and CITF above the upper limit of normal, and 13% did not prolong either. After heparin, enhanced platelet aggregation to ADP and collagen occurred in 53% and 63% of patients, respectively.

CONCLUSIONS

Although patients seem to have an anticoagulant effect after heparin based on ACT and aPTT results, the flow device identified a lack of any hemostatic impairment in 25 to 41% of patients. These findings probably reflect the variable effect of heparin on platelet function and may explain the poor heparin effect or, alternatively, the excessive bleeding after heparin administration that occurs in some patients.

Validity of index of suspicion for pulmonary embolism after hip arthroplasty

Pulmonary embolism after total hip arthroplasty is problematic, and intravenous heparin treatment in the absence of pulmonary embolism carries risk. Algorithms for treating pulmonary embolism often cite clinical index of suspicion as a basis for initiating intravenous heparin, but most information regarding variables to predict pulmonary embolism originate from studies of patients rather than only from patients who had arthroplasty. We studied the hypothesis that a more homogenous subpopulation, patients who had total hip arthroplasty, may have findings more accurately predictive of pulmonary embolism. One hundred fifty records of patients who had total hip arthroplasty who were suspected of having pulmonary embolism and who were evaluated for pulmonary embolism were assessed. Complaints, physical findings, heparinization status, and test results were analyzed with univariate and multivariate assessments to determine predictors of pulmonary embolism. No significant differences were found between patients with or without pulmonary embolism regarding subjective complaints, physical examination, blood gas results, electrocardiogram findings, radiographs of the chest, and imaging of the veins of the legs. All attempts to model these variables into an index of suspicion that accurately predicted pulmonary embolism were unsuccessful. We advise adherence to established treatment algorithms rather than clinical suspicion when deciding whether to initiate heparin therapy.

Prevention and management of venous thromboembolism in pregnancy

Pulmonary thromboembolism is a major cause of maternal mortality. DVT causes significant morbidity in pregnancy and in later life owing to the post-thrombotic syndrome. Obstetricians must have an understanding of the risk factors for VTE, the appropriate use of prophylaxis, the need for objective diagnosis in women with suspected VTE, and the appropriate use of anticoagulant therapy. Greater use of prophylaxis is needed after vaginal delivery. Because acute VTE is relatively uncommon, greater use of proposed guidelines [24,84,85] may be of value in improving management, but the involvement of clinicians with expertise in the management of these cases is also important.

Low molecular weight heparin for the treatment of venous thromboembolism in pregnancy: a case series

OBJECTIVES

To assess the use of low molecular weight heparin for the treatment of venous thromboembolism in pregnancy.

DESIGN

A prospective observational study.

SETTING

The maternity units in two university teaching hospitals and one district general teaching hospital.

POPULATION

Thirty-six consecutive women presenting with objectively diagnosed venous thromboembolism during pregnancy and the immediate puerperium.

METHODS

Treatment with the low molecular weight heparin enoxaparin, approximately 1 mg/kg s.c., twice daily, based on early pregnancy weight.

MAIN OUTCOME MEASURES

Peak anti-Xa activity (three hours post-injection), alterations in treatment, side effects and the use of regional anaesthesia.

RESULTS

In 33 women, the initial dose of enoxaparin provided satisfactory peak anti-Xa activity (median 0.8 u/mL, range 0.44-1.0 u/mL) and was continued. Three women required dose reduction since peak anti-Xa activities were above the therapeutic range (1.2, 1.2 and 1.1 u/mL). No woman developed thrombocytopaenia, haemorrhagic complication or further thromboembolic episode. Two women developed allergic skin reactions on enoxaparin and were changed to tinzaparin. Fifteen women had regional anaesthesia for delivery, with a reduced dose of enoxaparin (40 mg once daily), all without complication.

CONCLUSIONS

Enoxaparin is a safe and effective treatment for venous thromboembolism during pregnancy and confers a major advantage over unfractionated heparin through its simplified regimen of administration.

Primary pulmonary hypertension and cor pulmonale

Primary pulmonary hypertension and cor pulmonale represent forms of precapillary pulmonary hypertension due to intrinsic lung disease. In the case of primary pulmonary hypertension, this is due to disease of the pulmonary vasculature while cor pulmonale is related to diseases of the pulmonary vasculature, airways, or interstitium. Patients present with signs and symptoms of right ventricular dysfunction and low cardiac output including dyspnea, chest pain and peripheral edema. Therapy is directed at the underlying disease and may include supplemental oxygen for diseases causing chronic hypoxemia and anticoagulation for thrombotic disease. Vasodilator therapy has variable efficacy for pulmonary vascular disorders. Postacyclin by continuous infusion has been a major advance in the therapy of primary pulmonary hypertension and has prolonged survival and delayed the need for lung transplantation. Bosentan, an endothelin receptor blocking agent is the first oral medication approved for the therapy of pulmonary hypertension.

Manual aspiration versus chest tube drainage in first episodes of primary spontaneous pneumothorax: a multicenter, prospective, randomized pilot study

Although there is no agreement on the optimal treatment of patients presenting with a first episode of primary spontaneous pneumothorax, the majority of physicians prefer chest tube drainage for air evacuation. Manual aspiration of air has been proposed by some, but lack of sound comparative data and safety data has limited its use. In this first randomized, prospective, multicenter pilot study, 60 patients with a first episode of primary spontaneous pneumothorax were randomly allocated to manual aspiration (n = 27) or chest tube drainage (n = 33). Immediate success was obtained in 16 out of 27 (59.3%) in the manual aspiration group, and in 21 out of 33 (63.6%) in the chest tube drainage group (p = 0.9). One-week success rates were 25 out of 27 (93%) in the intention-to-treat manual aspiration group and 28 out of 33 (85%) in the chest tube drainage group (p = 0.4). Fourteen of 27 manual aspiration patients (52%) were hospitalized, versus 100% of the chest tube drainage patients (p < 0.0001). Recurrence rates with at least 1-year follow-up were 7 out of 26 (26%) in the manual aspiration group, and 9 out of 33 (27.3%) in the chest tube drainage group (p = 0.9). There were no complications associated with manual aspiration. Although statistical power is insufficient to formally confirm therapeutic equality, this pilot study suggests that in first episodes of primary spontaneous pneumothorax, manual aspiration seems equally effective as chest tube drainage and is safe, well tolerated, and feasible as an outpatient procedure in the majority of patients.

The acute management of venous thromboembolism in pregnancy

Pulmonary thromboembolism is the leading cause of maternal death in the UK. Optimal management of deep venous thrombosis and pulmonary thromboembolism requires an appreciation of risk factors, particularly thrombophilia, and signs or symptoms suggestive of venous thromboembolism, along with objective diagnosis and treatment with anticoagulants. Low molecular weight heparins are now replacing unfractionated heparin for the treatment of deep venous thrombosis and pulmonary thromboembolism in pregnancy because of the lower risk of side effects, ease of administration and reduced need for monitoring.

Diagnosis of pulmonary embolism

Pulmonary embolism (PE) is a common, lethal yet treatable disease. The clinical diagnosis of PE remains to be a problem due to the nonspecific presenting signs, symptoms, electrocardiographic findings, arterial blood gas abnormalities and chest X-ray changes. Despite these nonspecific clinical findings, clinicians are adept at assigning pretest probability using overall clinical assessment. Clinical models have been developed to improve the accuracy of pretest probability assessment. D-dimers are becoming a widely available clinical tool useful in the diagnostic management of suspected PE. The limitations of the imaging modalities for PE [ventilation-perfusion (V/Q) scanning, spiral computerised tomography, pulmonary angiography and venous leg imaging] necessitate the use of these tests in series and in combination with clinical pretest probability assessment and D-dimer in diagnostic management algorithms. These algorithms permit safe diagnostic management of patients with suspected PE while limiting invasiveness, inaccessibility and expense.

Recurrence of idiopathic thromboembolism during anticoagulant therapy

Patients with acute pulmonary embolism and venous thromboembolism are usually treated with anticoagulant therapy for at least 3 months as the optimum duration. A patient with recurrent idiopathic venous thromboembolism at the eighth month during anticoagulation (warfarin to target international normalized ratio of 2.0-3.0) is described. The case suggests that patients with idiopathic venous thromboembolism have a high risk of recurrence, even if a strict anticoagulant regimen is followed.

Management of venous thromboembolism in pregnancy

Pulmonary thromboembolism (PTE) is the major cause of maternal death in the UK, with recent trends showing an increase in the numbers of deaths. Underlying PTE is the problem of deep venous thrombosis (DVT). An appreciation of risk factors, particularly, thrombophilia, and signs or symptoms suggestive of thromboembolism, coupled with objective diagnosis and treatment should reduce mortality and morbidity. There are particular considerations with regard to the management of thrombosis in pregnancy, especially the use of anticoagulants. Low-molecular-weight heparins are now replacing unfractionated heparin for the treatment of DVT and PTE in pregnancy.

The effects of heparin and oral anticoagulants on thrombus propagation and prevention of the postphlebitic syndrome: a critical review of the literature

Based on a comprehensive literature search, this report aims to examine the effects of heparin and oral anticoagulants on thrombus propagation and prevention of the postphlebitic syndrome. The effects on recurrence of thromboembolic disease have not been addressed. It is concluded that published reports of serial venograms and ultrasound examinations of patients treated with conventional anticoagulant therapy for deep venous thrombosis show either no change or thrombus extension in the first few months in approximately 50% of cases. Approximately two thirds of patients will have damage to the venous valves, leading to incompetence or other hemodynamic changes. More than one third of patients so treated may have oedema, leg pain, or other severe symptoms on long-term follow-up. The consistency with which these outcomes have been observed, particularly in many large, recent, prospective trials, adds to the credibility of these figures. The results of prospective controlled trials have failed uniformly to show any significant local benefits of anticoagulant therapy for deep vein thrombosis compared with other treatments or placebo. There does not seem to be any convincing evidence that heparin exerts a favorable influence on pulmonary embolism in situ or on portal vein thrombosis. Use of anticoagulant therapy to limit thrombus propagation therefore cannot be said to be "evidence based." These generally poor outcomes with regard to postphlebitic complications should lead to an active exploration of alternative methods of management. Substantial uncertainties surrounding many fundamental aspects of the treatment of this disease remain, and further placebo-controlled trials are needed.

Looking forward in the treatment of deep-vein thrombosis

Clinical guidelines developed by the American College of Chest Physicians (ACCP) for the management of venous thromboembolism (VTE) are based on current evidence from randomized clinical trials and amended in response to emerging results. The standard treatment for VTE comprises in-hospital treatment with dose-adjusted unfractionated heparin (UFH) for a minimum of 5 days and oral anticoagulants for at least 3 months. Recent clinical studies show that subcutaneous low-molecular-weight heparins (LMWHs) in fixed doses according to body weight are as effective and safe as intravenous UFH in the initial treatment of deep-vein thrombosis, with or without pulmonary embolism. There is also evidence that the optimal duration of secondary thromboprophylaxis depends on assessable thromboembolic risk factors. The 1998 ACCP guidelines take account of this new evidence by advocating LMWHs as an alternative to standard UFH for the initial treatment of VTE and risk stratification of patients to guide duration of secondary thromboprophylaxis. Outpatient treatment of VTE with LMWHs has been shown to be feasible and is increasingly used in clinical practice, offering substantial economic benefits. Certain LMWHs appear to be effective at a once-daily dose. Evidence is now emerging that may clarify the role of inferior vena cava filters and thrombolysis in VTE management. Future versions of the ACCP guidelines may be expected to reflect new data from ongoing trials.

Clinical and economic aspects of managing venous thromboembolism in the outpatient setting

Low-molecular-weight heparins (LMWHs) are at least as effective and safe as unfractionated heparin (UFH) in the prevention and initial treatment of venous thromboembolism (VTE), and their fixed-dose, once- or twice-daily dosing regimen without laboratory monitoring makes them suitable for outpatient use. Postoperative thromboprophylaxis usually continues until hospital discharge, but evidence demonstrates that the VTE risk persists for several weeks. Economic pressures, changes in clinical practice, and patient preferences make hospital stays shorter. As a result, outpatient thromboprophylaxis with LMWH has been investigated. LMWH self-administered at home once daily for up to 4 weeks after hospital discharge is safe and well tolerated and significantly reduces the incidence of postdischarge VTE after hip replacement. Targeted appropriately, extended thromboprophylaxis may be cost effective, and the development of an autoinjection device may increase the proportion of patients eligible for home management. LMWHs may also be of value as long-term secondary thromboprophylaxis in patients with contraindications to oral anticoagulants. Standard initial treatment for VTE comprises intravenous UFH administered to the patient in the hospital. However, three large-scale studies have demonstrated the efficacy and safety of outpatient treatment of acute VTE using LMWHs. The economic benefits of shortening or eliminating inpatient therapy are substantial, but successful home treatment requires careful patient selection, intensive education and a comprehensive system of professional support to optimize compliance and safety.

Mechanical thrombectomy in patients with deep venous thrombosis

PURPOSE

To report our experience with mechanical thrombectomy in proximal deep vein thrombosis (DVT).

METHODS

Eighteen patients with a mean (+/- SD) age of 37.6 +/- 16.1 years who presented with DVT in the iliac and femoral vein (n = 3), inferior vena cava (n = 5), or inferior vena cava and iliac vein (n = 10), were treated with the Amplatz Thrombectomy Device after insertion of a temporary caval filter.

RESULTS

Successful recanalization was achieved in 15 of 18 patients (83%). Overall, the percentage of thrombus removed was 66 +/- 29%: 73 +/- 30% at caval level and 55 +/- 36% at iliofemoral level. Complementary interventions (seven patients) were balloon angioplasty (n = 2), angioplasty and stenting (n = 2), thrombo-aspiration alone (n = 1), thrombo-aspiration, balloon angioplasty, and permanent filter (n = 1), and permanent filter alone (n = 1). There was one in-hospital death. Follow-up was obtained at a mean of 29.6 months; three patients had died (two cancers, one myocardial infarction); 10 had no or minimal sequelae; one had post-phlebitic limb.

CONCLUSION

Mechanical thrombectomy is a potential therapeutic option in patients presenting with proximal DVT.

Inferior vena cava filters for HIV infected patients with pulmonary embolism and contraindications to anticoagulation

OBJECTIVES

To describe the mode of presentation, interventions, and outcome of HIV infected patients with pulmonary embolism and a contraindication to anticoagulation, who were treated with a bird's nest filter.

METHODS

Retrospective review of case records and imaging department database at UCL Hospitals, London, UK.

RESULTS

Three patients had pulmonary embolism and contraindications to anticoagulation. Contraindications were concomitant intracerebral pathology in two patients (one also had bleeding from gastric Kaposi's sarcoma and the other was cognitively impaired with HIV associated dementia complex) and alcohol induced liver disease/binge drinking in the third patient. Anticoagulation was avoided by introducing a bird's nest filter into the inferior vena cava via the common femoral vein. During follow up (7, 8, and 21 months) no complications or recurrent pulmonary emboli occurred.

CONCLUSION

The bird's nest inferior vena cava filter has a role in preventing further pulmonary emboli in HIV infected patients with contraindications to anticoagulation.

Emerging concepts in the diagnosis and management of venous thromboembolism during pregnancy

Multiple changes in the coagulation system occur during pregnancy and account for the hypercoagulable state of pregnancy. Consequently, pregnant women are five times more likely to experience venous thromboembolism than non-pregnant women. Although the estimated rates of such events are low, venous thromboembolic disease is a leading cause of maternal death. The administration of intravenous or subcutaneous unfractionated heparin is the treatment and prophylaxis of choice. Warfarin is safe and efficacious following delivery, but should be avoided during pregnancy. LMWH is a promising alternative for treatment and prophylaxis, but further clinical experience is required.

Treatment of deep vein thrombosis using temporary vena caval filters after allogeneic bone marrow transplantation

Bone marrow transplant (BMT) recipients have risk factors for deep vein thrombosis (DVT) including venous stasis caused by immobilization in the sterile unit, vessel wall damage caused by preparative regimen or indwelling catheters, and hypercoagulability caused by decreased natural anticoagulants. We successfully treated a patient who developed massive DVT in the superior vena cava after BMT with anticoagulation and the use of temporary vena caval filters. Considering the delayed complications, permanent filter is not appropriate for BMT recipients, because the risk factors for DVT associated with BMT are transient. We considered that temporary vena caval filter is a safe and useful device to prevent pulmonary embolism after DVT in BMT recipients.

Orally administered unfractionated heparin with carrier agent is therapeutic for deep venous thrombosis

BACKGROUND

Orally administered heparin (OHEP) is unreliable because of poor absorption. Sodium N-(8[2-hydroxybenzoyl]amino) caprylate (SNAC) is an amido acid that facilitates the gastrointestinal absorption of heparin. We evaluated the effectiveness of OHEP combined with SNAC (OHEP/SNAC) in the treatment of deep-vein thrombosis (DVT).

METHODS AND RESULTS

An internal jugular DVT was produced in 54 male Sprague-Dawley rats. Animals were assigned to 6 different groups for 7 days of treatment: untreated control, subcutaneous heparin (SC HEP) (300 U/kg SC TID), SNAC only (300 mg/kg PO TID), OHEP only (30 mg/kg PO TID), low-molecular-weight heparin (LMWH) (enoxaparin 5 mg/kg SC QD), and OHEP/SNAC (30 mg/kg:300 mg/kg PO TID). The activated partial thromboplastin time (aPTT) and anti-factor X (anti-Xa) levels were measured. The incidence of residual DVT after 1 week of treatment was 100% (9 of 9) in the control group versus 10% (1 of 10) in the OHEP/SNAC and 10% (1 of 10) in the LMWH groups (P<0.001). There was also a significant reduction in clot weights between these groups. Compared with controls, there were no significant differences in the residual DVT in the SNAC-only (6 of 6), OHEP-only (9 of 9), or SC HEP (8 of 10) groups. Combination OHEP/SNAC was as effective in the resolution of the clot and reducing clot weight as LMWH. The aPTT levels in the OHEP/SNAC group peaked at 30 minutes and were significantly higher than in all other groups (P<0.01). Anti-Xa levels were elevated at 15 minutes after dosing in the OHEP/SNAC group and remained significantly elevated at 4 hours (P<0.001).

CONCLUSIONS

OHEP combined with a novel carrier agent (SNAC) successfully treated DVT in this rat model.

The use of low molecular weight heparin in pediatric patients: a prospective cohort study

OBJECTIVE

Low molecular weight heparins (LMWHs) offer several advantages over standard anticoagulant therapy (unfractionated heparin/warfarin) including predictable pharmacokinetics, minimal monitoring, and subcutaneous administration. Our objective was to determine the safety and efficacy of LMWHs in children.

METHODS

A prospective cohort of children treated with the LMWH enoxaparin (Rhone Poulenc Rorer) was monitored at the Hospital for Sick Children, Toronto, Canada, from March 1994 until July 1997.

RESULTS

There were 146 courses of LMWH administered for treatment and 31 courses for prophylaxis of thromboembolic events (TEs). Clinical resolution of TEs occurred in 94% of children receiving therapeutic doses of LMWH, and 96% of children receiving prophylactic doses of LMWH had no symptoms of recurrent or new TEs. Major bleeding occurred in 5% of children receiving therapeutic doses. Recurrent or new TEs occurred in 1% and 3% of children receiving therapeutic and prophylactic doses of LMWH, respectively.

CONCLUSION

LMWH appears to be efficacious and safe for both management and prophylaxis of TEs. The results of this cohort study justify a randomized controlled trial comparing LMWH with standard therapy for the management of TEs in children.

Non-haemorrhagic obstetric shock

The causes of non-haemorrhagic obstetric shock (pulmonary thromboembolism, amniotic fluid embolism, acute uterine inversion and sepsis) are uncommon but responsible for the majority of maternal deaths in the developed world. Clinically suspected pulmonary thromboembolism should be treated initially with heparin and objective testing should be performed. If the diagnosis is confirmed, heparin is usually continued until delivery, following which anticoagulation in the puerperium is achieved with either warfarin or heparin. Amniotic fluid embolism is a rare complication of pregnancy, occurring most commonly during labour. The management of amniotic fluid embolism involves maternal oxygenation, the maintenance of cardiac output and blood pressure, and the management of any associated coagulopathy. Acute uterine inversion arises most commonly following mismanagement of the third stage of labour. The shock in uterine inversion is neurogenic in origin, although there may also be profound haemorrhage. The management of this condition includes maternal resuscitation and replacement of the uterus either manually, surgically or by hydrostatic pressure. Genital tract sepsis remains a significant cause of maternal death, the most common predisposing factor being prolonged rupture of the fetal membranes. The management of septic shock in pregnancy includes resuscitation, identification of the source of infection and alteration of the systemic inflammatory response.

Direct measurement of unfractionated heparin using a biochemical assay

A number of investigations have noted that functional biological assays for heparin are not always reliable and may not reflect the actual biochemical level of heparin in patients receiving anticoagulant therapy. This creates the possibility that patients receiving anticoagulant treatment may have an excess or deficiency of circulating levels of heparin. To address this problem, we have developed a direct biochemical measurement of heparin. The heparin assay uses fluorophore-assisted carbohydrate electrophoresis (FACE) to directly measure the predominate disaccharide of unfractionated heparin. In this study, unfractionated heparin was measured in vitro throughout a wide range of heparin concentrations in plasma. Seven in vivo pharmacokinetic studies in five normal subjects given 3,000 USP units of unfractionated heparin intravenously showed a three-phase elimination process with higher peak plasma levels and shorter elimination times than predicted from previous studies. At these doses, heparin is largely eliminated intact through urinary excretion. Body weight has a significant effect on heparin kinetics. When we compared the direct biochemical assay with two biological clotting assays, we found the latter can overestimate biochemical heparin concentrations. The FACE assay, due to its sensitivity, is also able to measure circulating levels of endogenous heparin in plasma and urine. Direct heparin measurement using the FACE technique is practical and useful for studies of the correlation of biochemical and biological activities.

The use of heparin in patients in whom a pulmonary embolism is suspected after total hip arthroplasty

BACKGROUND

The morbidity and mortality associated with pulmonary embolism are well known, as is the benefit of the use of heparin in patients who have a pulmonary embolism. However, the patterns of heparin use as well as its undesirable effects, especially in patients who have recently had a total hip arthroplasty, have been less well studied. Thus, concern arises regarding the use of heparin in patients who have no firm evidence of a pulmonary embolism. The purpose of the current study was to track the use of heparin and associated orthopaedic complications in patients in whom a pulmonary embolism was suspected after a total hip arthroplasty.

METHODS

The records of 150 patients in whom a pulmonary embolism had been suspected after a total hip arthroplasty were reviewed retrospectively. The rates of individual complications (such as stroke, infection, and hematoma) and those of groups of complications (such as medical complications, orthopaedic complications, and all complications combined) were recorded and then were stratified according to the treatment (with or without heparin), the presence or absence of pulmonary embolism, and other variables.

RESULTS

Thirty-two (47 percent) of sixty-eight patients who were managed with heparin had complications compared with sixteen (20 percent) of eighty-two patients who were not thus managed (p = 0.0006). Specifically, patients who were managed with heparin were more likely to have gastrointestinal bleeding, hematological complications, a loose prosthesis, a hematoma, or an early revision arthroplasty (p<0.05 for all). With the numbers available, the use of heparin was not found to be significantly associated with an increased risk of death, stroke, or infection at the site of the prosthesis. Interestingly, thirty-one (31 percent) of ninety-nine patients who had ventilation-perfusion scans that demonstrated normal findings or findings indicating a low probability of pulmonary embolism were given heparin before the diagnosis of a pulmonary embolism was excluded, and sixteen (52 percent) of these thirty-one had complications.

CONCLUSIONS

Given this risk profile, we advise against the use of heparin before the diagnosis of pulmonary embolism is established in patients who have had a total hip arthroplasty. This recommendation is supported by algorithms, in widely read medical texts, pertaining to the use of heparin in patients in whom a pulmonary embolism is suspected.

Correlation of activated clotting time and activated partial thromboplastin time to plasma heparin concentration

STUDY OBJECTIVE

To determine the correlation between activated clotting time (ACT) or activated partial thromboplastin time (aPTT) and plasma heparin concentration.

DESIGN

Two-phase prospective study.

SETTING

University-affiliated community hospital.

PATIENTS

Thirty patients receiving continuous-infusion intravenous heparin.

INTERVENTIONS

Measurement of ACT, aPTT and plasma heparin concentrations.

MEASUREMENTS AND MAIN RESULTS

Linear and log linear correlations were determined between clotting time tests and heparin concentrations. Linear correlations yielded r values of 0.58 for ACT (p=0.008) and 0.89 for aPTT (p=0.0001). Log linear correlations yielded r values of 0.60 for ACT (p=0.005) and 0.88 for aPTT (p=0.0001). A decision analysis was performed to determine possible consequences of dosage adjustments based on either test in relationship to the decision based on plasma heparin concentration. The decision analysis based on ACT disagreed with corresponding decisions based on plasma heparin concentration in 15 of 30 patients; 13 disagreements may have increased the risk of bleeding, and the other 2 may have increased the risk of thrombosis. Decisions based on aPTT disagreed with corresponding decisions based on plasma heparin concentration in 13 of 30 patients; 2 disagreements may have increased the risk of bleeding, and the other 11 may have increased the risk of thrombosis.

CONCLUSION

There are significant statistical linear and log linear correlations between both clotting time tests and plasma heparin concentrations, with aPTT showing stronger correlation than ACT. However, decisions regarding heparin therapy based on ACT may increase a patient's risk of bleeding, whereas decisions based on aPTT may increase the risk of thrombus progression or rethrombosis.

Thrombolytic therapy of pulmonary embolism: a comprehensive review of current evidence

Pulmonary embolism (PE) is a common disorder that is accompanied by significant morbidity and mortality. Although anticoagulation is the standard treatment for PE, thrombolytic therapy, with its ability to produce rapid clot lysis, has long been considered an attractive alternative. Although many studies have been performed over the past three decades, however, the indications for the use of thrombolytic agents in patients with PE remain controversial. In this article, we review the medical literature and provide evidence-based guidelines for the use of thrombolytic therapy. We will also discuss the practical aspects of PE thrombolysis.