Antithrombotic therapy for venous thromboembolic disease

Poly-ion complex (PIC) formation of heparin and polyamines: PIC with tetrakis (3-aminopropyl) ammonium allows sustained release of heparin

Physical mixtures of cationic polymers and heparin have been developed to overcome the limitations of unfractionated heparin. In this study, we found that heparin associates with natural polyamines in water, resulting in the generation of a poly-ion complex (PIC). PIC formation (or stability) was influenced by the concentration and ratio of heparin and polyamines, molecular weight of heparin, nature of polyamines, and pH conditions. Interestingly, the PIC obtained when heparin and tetrakis (3-aminopropyl) ammonium (Taa) were mixed exhibited stability and was sticky in nature. PIC formation was due to an electrostatic interaction between heparin and Taa. Heparin-Taa PIC was administered subcutaneously to mice, and the time to maximum heparin concentration within the therapeutic range of heparin was markedly increased compared to that after a single dose of heparin. These results suggest that the quaternary ammonium structure of Taa is critical for the preparation of a stable PIC, thereby allowing the sustained release of heparin into the blood.

Effectiveness of Inferior Vena Cava Filters in Patients With Stable and Unstable Pulmonary Embolism and Trends in Their Use

BACKGROUND

Trends in the use of inferior vena cava (IVC) filters in patients with pulmonary embolism (PE) who are stratified according to whether they are stable or unstable (in shock or ventilator dependent) may show where improvements of management could be made according to the best evidence that we now have.

METHODS

This was a retrospective cohort study based on administrative data, 1999-2014, from the National (Nationwide) Inpatient Sample.

RESULTS

In-hospital all-cause mortality in unstable patients who received an IVC filter was lower in each year of investigation and in all age groups. Mortality from 1999 to 2014 was 10,140 of 35,230 (28.8%) with an IVC filter compared with 54,018 of 116,642 (46.3%) without a filter (P <0.0001). In stable patients from 1999 to 2014, mortality with an IVC filter was 31,909 of 546,858 (5.8%) with an IVC filter compared with 220,443 of 3,367,783 (6.5%) without a filter (P <0.0001). In patients ages > 80 years, mortality in stable patients with an IVC filter was 7,438 of 114,457 (6.5%) with an IVC filter compared with 64,113 of 567,348 (11.3%) without an IVC filter (P <0.0001). The number of stable patients who received an IVC filter decreased from 2010 to 2014, but even in those years the largest number of IVC filters was inserted in stable patients, 194,502 of 212,611 (91.5%).

CONCLUSIONS

Mortality is markedly reduced in unstable patients who receive an IVC filter. Despite this, the proportion of unstable patients who receive an IVC filter is decreasing. The largest number of IVC filters continues to be inserted in stable patients, although there is no evidence of a clinically meaningful reduced mortality with IVC filters in stable patients unless age >80 years.

Use and Removal of Inferior Vena Cava Filters in Patients With Acute Brain Injury

Background

Few data exist regarding the rate of inferior vena cava (IVC) filter retrieval among brain-injured patients.

Methods

We conducted a retrospective cohort study using inpatient claims between 2009 and 2015 from a nationally representative 5% sample of Medicare beneficiaries. We included patients aged ≥65 years who were hospitalized with acute brain injury. The primary outcome was the retrieval of IVC filter at 12 months and the secondary outcomes were the association with 30-day mortality and 12-month freedom from pulmonary embolism (PE). We used Current Procedural Terminology codes to ascertain filter placement and retrieval and International Classification of Diseases, Ninth Revision, Clinical Modification codes to ascertain venous thromboembolism (VTE) diagnoses. We used standard descriptive statistics to calculate the crude rate of filter placement. We used Cox proportional hazards analysis to examine the association between IVC filter placement and mortality and the occurrence of PE after adjustment for demographics, comorbidities, and mechanical ventilation. We used Kaplan-Meier survival statistics to calculate cumulative rates of retrieval 12 months after filter placement.

Results

Among 44 641 Medicare beneficiaries, 1068 (2.4%; 95% confidence interval [CI], 2.3%-2.5) received an IVC filter, of whom 452 (42.3%; 95% CI, 39.3%-45.3) had a diagnosis of VTE. After adjusting for demographics, comorbidities, and mechanical ventilation, filter placement was not associated with a reduced risk of mortality (hazard ratio [HR], 1.0; 95% CI, 0.8-1.3) regardless of documented VTE. The occurrence of pulmonary embolism at 12 months was associated with IVC filter placement (HR, 3.19; 95% CI, 1.3-3.3) in the most adjusted model. The cumulative rate of filter retrieval at 12 months was 4.4% (95% CI, 3.1%-6.1%); there was no significant difference in retrieval rates between those with and without VTE.

Conclusions

In a large cohort of Medicare beneficiaries hospitalized with acute brain injury, IVC filter placement was uncommon, but once placed, very few filters were removed. IVC filter placement was not associated with a reduced risk of mortality and did not prevent future PE.

Anti-coagulation Drug Warfarin Contributes to Severe Adverse Outcomes in Prolonged Unsupervised Use: A Double-edged Sword

Anti-coagulation medications are widely used in clinical practice, especially in the United States as cardiac-related emergencies are on the rise. An overarching caveat in using anti-coagulation drugs as a long-term treatment regimen, such as warfarin, is that patients are closely monitored by their primary care provider. Routine monthly laboratory examinations are strictly required to assess the international normalized ratio (INR) which measures prothrombin time (PT), providing insight into how long it takes for blood to clot. A 58-year-old Caucasian male presented with non-traumatic acute quadriplegia with cord compression starting at the 3rd cervical (C3) level and continuing throughout the entire spinal cord. Radiological studies revealed severe cervical stenosis from C3 to C7 resulting from a posterior spinal mass, thoracic and lumbar spine studies revealed a compressive posterior acute epidural hematoma (EDH) compressing the thoracic spinal cord from T6 to T10 with signal change, as well as a L4-S1 posterior acute epidural hematoma compressive of the cauda equina. Upon detailed review of our patient’s history it became evident that our patient had been on a prolonged and unsupervised warfarin (Coumadin) regimen for congestive heart failure without primary care follow-up or routine laboratory testing. Our patient was a prime surgical candidate for an immediate two-stage decompression, hematoma evacuation and instrumentated fusion surgery. Post-operatively, our patient regained leg strength to 2/5 and arm strength to 4+/5.

Effect of pathological heterogeneity on shear wave elasticity imaging in the staging of deep venous thrombosis

Background

We aimed to observe the relationship between the pathological components of a deep venous thrombus (DVT), which was divided into three parts, and the findings on quantitative ultrasonic shear wave elastography (SWE) to increase the accuracy of thrombus staging in a rabbit model.

Methods

A flow stenosis-induced vein thrombosis model was used, and the thrombus was divided into three parts (head, body and tail), which were associated with corresponding observation points. Elasticity was quantified in vivo using SWE over a 2-week period. A quantitative pathologic image analysis (QPIA) was performed to obtain the relative percentages of the components of the main clots.

Results

DVT maturity occurred at 2 weeks, and the elasticity of the whole thrombus and the three parts (head, body and tail) showed an increasing trend, with the Young's modulus values varying from 2.36 ± 0.41 kPa to 13.24 ± 1.71 kPa; 2.01 ± 0.28 kPa to 13.29 ± 1.48 kPa; 3.27 ± 0.57 kPa to 15.91 ± 2.05 kPa; and 1.79 ± 0.36 kPa to 10.51 ± 1.61 kPa, respectively. Significant increases occurred on different days for the different parts: the head showed significant increases on days 4 and 6; the body showed significant increases on days 4 and 7; and the tail showed significant increases on days 3 and 6. The QPIA showed that the thrombus composition changed dynamically as the thrombus matured, with the fibrin and calcium salt deposition gradually increasing and the red blood cells (RBCs) and platelet trabecula gradually decreasing. Significant changes were observed on days 4 and 7, which may represent the transition points for acute, sub-acute and chronic thrombi. Significant heterogeneity was observed between and within the thrombi.

Conclusions

Variations in the thrombus components were generally consistent between the SWE and QPIA. Days 4 and 7 after thrombus induction may represent the transition points for acute, sub-acute and chronic thrombi in rabbit models. A dynamic examination of the same part of the thrombus may be helpful for improving the sensitivity and reproducibility of SWE for DVT diagnosis and staging.

Evaluation of costs and outcomes associated with pharmacological thromboprophylaxis (unfractionated heparin and low molecular weight heparins) of venous thromboembolism at orthopedic ward in Clinical Hospital Stip

Clinical trials have shown Low-molecular weight heparins (LMWHs) to be at least as safe and efficacious as unfractionated heparin (UFH) for preventing venous thromboembolism (VTE) in patients undergoing major orthopedic surgery who are at highest risk of developing VTE. The retrospective study was conducted at orthopedic department in Clinical Hospital – Stip for period of 12 months (January-December 2013), where LMWHs and UFH are accepted thromboprophylaxis options. 320 patients (144 males and 157 females, medium age 58 years and 70 years, respectively) were hospitalized for various types of major orthopedic surgical interventions. 212 (66%) patients were admitted because of hip or knee fractures, 26 (8%) had conditions after hip or knee fractures and 82 (26%) were hospitalized for removal or implanting of osteosynthetic devices. After the surgical intervention, patients were subjected to anticoagulant prophylaxis (UFH or LMWHs). Which type of prophylaxis will be used depended exclusively on the surgeon’s decision. VTE complications resulting death were observed in 8 (2.5%) out of 13 patients. Death because of PE occurred in 2 (25%) out of 8 patients, compared to 6 (75%) patients who had fatal DVT complications. The average hospital cost for patients treated with LMWHs prophylaxis as first line thromboprophylaxis option was 52831.92 MKD/patient compared to 70082.24 MKD/patient for UFH first line thromboprophylaxis option. We observed that LMWHs thromboprophylaxis, applied in recommended doses subcutaneously once a day, is potentially more effective and cost saving option compared to UFH and should be considered as pharmacological treatment of first choice for the prevention of VTE (DVT and PE) in patients recovering from major orthopedic surgery at the orthopedic department in Clinical Hospital Stip. Keywords: Thromboprophylaxis, major orthopedic surgery, LMWHs, UFH

A Survey of Physicians' Knowledge and Management of Venous Thromboembolism

A review of all patients diagnosed with venous thromboembolism (VTE) at an academic medical center from 1996 to 1998 revealed a wide variation in management and subsequent patient outcomes and a 30% increase in utilization of the vascular laboratory from the previous 2-year period. The purpose of this study was to determine physicians' knowledge and management strategies before the implementation of integrated care pathways for VIE. Mail surveys were sent to 650 physicians covering 3 academic medical centers. The disciplines targeted were from those physicians who had previously referred patients for any VTE screening examination. One-hundred and twenty-eight physicians (20%) completed the survey. Only 12% of the physicians were able to correctly identify all of the veins routinely imaged as either deep or superficial veins. Fifty-nine percent of the physicians incorrectly identified the superficial femoral vein of the thigh as a superficial vein, and 23% believed the popliteal vein to be a superficial vein. Only 17% of the respondents correctly classified the tibial-peroneal veins as deep veins. Approximately 70% of the physicians stated that they would not treat symptomatic isolated calf vein thrombosis, and, of those, only 42% said that they would obtain serial duplex scans to monitor for proximal propagation. Physicians underestimated the charges for all diagnostic screening tests, and only 14% were able to correctly identify the range of charges for a venous duplex scan. This survey of physicians demonstrated a lack of basic knowledge regarding lower extremity venous anatomy, charges for the different diagnostic tests used to diagnose VIE, and, most importantly, current treatment standards for VTE.

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.

Thrombocytopenia in Critical Care Patients

Thrombocytopenia is a common laboratory finding in the intensive care unit (ICU) patient. Because the causes can range from laboratory artifact to life-threatening processes such as thrombotic thrombocytopenic purpura (TTP), identifying the cause of thrombocytopenia is important. In the evaluation of the thrombocytopenia patient, one should incorporate all clinical clues such as why the patient is in the hospital, medications the patient is on, and other abnormal laboratory findings. One should ensure that the patient does not suffer from heparin-induced thrombocytopenia (HIT) or one of the thrombotic microangiopathies (TMs). HIT can present in any patient on heparin and requires specific testing and antithrombotic therapy. TMs cover a spectrum of disease ranging from TTP to pregnancy complications and can have a variety of presentations. Management of disseminated intravascular coagulation depends on the patient’s condition and complication. Other causes of ICU thrombocytopenia include sepsis, medication side effects, post-transfusion purpura, catastrophic anti phospholipid antibody disease, and immune thrombocytopenia.

Incidence and risk factors for venous thromboembolism following surgical treatment of fractures below the hip: a meta-analysis

Venous thromboembolism (VTE) is a common complication after surgical treatment of fractures, which is associated with significant morbidity and mortality. Identifying the risk factors for VTE is important for preventive strategies to reduce the incidence of VTE. Therefore, we conducted a meta-analysis to evaluate the incidence of VTE and the risk factors influencing the development of VTE in patients who underwent surgery for fractures below the hip. PubMed, Embase, Web of Science, SinoMed (Chinese BioMedical Literature Service System, China) and CNKI (National Knowledge Infrastructure, China) databases were systematically searched to identify cohort or case-control studies that investigated the incidence and risk factors for VTE following surgical treatment of fractures below the hip. VTE risk ratios (RRs) were pooled by use of a fixed-effect model or a random-effect model, depending on the heterogeneity among the included studies. Heterogeneity between the studies was assessed by I² statistics. Twenty-three studies with a total of 191 294 patients who met the inclusion criteria were included in this meta-analysis. Our results demonstrated that age (≥60 years) (RR = 1·85, 95% confidence interval (CI): 1·34, 2·55; P = 0·000), previous VTE(RR = 5·25, 95% CI: 2·77, 9·96; P = 0·000), heart failure (RR = 1·74, 95% CI: 1·34, 2·27; P = 0·000), current smoking status (RR = 1·23, 95% CI: 1·07, 1·41; P = 0·004), hypertension (RR = 1·62, 95% CI: 1·27, 2·06; P = 0·000), hyperlipidaemia (RR = 2·16, 95% CI: 1·79, 2·62; P = 0·000), diabetes mellitus (RR = 1·46, 95% CI: 1·27, 1·68; P = 0·000), obesity (RR = 1·58, 95% CI: 1·35,·1·85; P = 0·000), multiple fractures (RR = 2·14, 95% CI: 1·00, 4·60; P = 0·050), varicose veins (RR = 3·07, 95% CI: 1·12, 8·47; P = 0·030), prolonged operation time (weighted mean differences (WMD) = 1·22, 95% CI: 0·63, 1·81; P = 0·000) and prolonged bed rest time (WMD = 3·12, 95% CI: 2·96, 3·29; P = 0·000) were associated with an increased risk of developing VTE. The other variables, including age (<60 years), previous smoking, immobility, pregnancy, cancer, open fractures and combination with trauma were not identified as significant risk factors for VTE. Almost all the risk factors mentioned above are in line with the known risk factors for VTE following surgery for fractures below the hip. Thus, surgeons should pay close attention to patients with these medical conditions in order to reduce the incidence of VTE following surgical treatment of fractures below the hip.

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.

Incidence and Factors Predicting Venous Thromboembolism After Surgical Treatment of Fractures Below the Hip

OBJECTIVES

This study was designed to investigate the incidence and risk factors of postoperative venous thromboembolism (VTE) in a series of patients with fractures below the hip. In addition, we sought to examine the rates of VTE before and after introduction of thromboprophylaxis.

DESIGN

Retrospective review.

SETTING

University-based academic medical center.

PATIENTS

Nine hundred one consecutive patients met the inclusion criteria. Of the 901 patients, 337 (37.4%) were treated before the initiation of institutional guidelines for thromboprophylaxis and 564 (62.6%) received thromboprophylaxis in accordance with our hospitalization protocol.

INTERVENTION

Surgical intervention for fractures occurring in the lower extremity below the hip.

MAIN OUTCOME MEASUREMENTS

Symptomatic thromboembolic events within 90 days of surgery and risk factors of postoperative VTE.

RESULTS

Of the 901 patients, 25 (2.7%) had confirmed symptomatic deep vein thrombosis and 13 (1.4%) had symptomatic pulmonary embolism. The overall incidence of symptomatic VTE was significantly different between the patients not receiving thromboprophylaxis (6.8%; 23 of 337) and those receiving thromboprophylaxis (2.3%; 13 of 564). Of the 31 variables tested for an association with VTE, an advanced age of more than 60 years, cardiovascular disease, and chronic lung disease were independent risk factors.

CONCLUSIONS

Clinically detectable VTE in fractures of the lower extremity below the hip are not uncommon, and thromboprophylaxis seemed to decrease the incidence of postoperative VTE.

LEVEL OF EVIDENCE

Prognostic Level II. See the guidelines for authors for a complete description of levels of evidence.

Canadian consensus recommendations on the management of venous thromboembolism in patients with cancer. Part 2: treatment

Patients with cancer are at increased risk of venous thromboembolism (vte). Anticoagulation therapy is used to treat vte; however, patients with cancer have unique clinical circumstances that can often make decisions surrounding the administration of therapeutic anticoagulation complicated. No national Canadian guidelines on the management of established cancer-associated thrombosis have been published. We therefore aimed to develop a consensus-based, evidence-informed guideline on the topic. PubMed was searched for clinical trials and meta-analyses published between 2002 and 2013. Reference lists of key articles were hand-searched for additional publications. Content experts from across Canada were assembled to review the evidence and make recommendations. Low molecular weight heparin is the treatment of choice for cancer patients with established vte. Direct oral anticoagulants are not recommended for the treatment of vte at this time. Specific clinical scenarios, including the presence of an indwelling venous catheter, renal insufficiency, and thrombocytopenia, warrant modifications in the therapeutic administration of anticoagulation therapy. Patients with recurrent vte should receive extended (>3 months) anticoagulant therapy. Incidental vte should generally be treated in the same manner as symptomatic vte. There is no evidence to support the monitoring of anti-factor Xa levels in clinically stable cancer patients receiving prophylactic anticoagulation; however, levels of anti-factor Xa could be checked at baseline and periodically thereafter in patients with renal insufficiency. Follow-up and education about the signs and symptoms of vte are important components of ongoing patient care.

Neuroprotective effect of 2-(4-methoxyphenyl)ethyl-2-acetamido-2-deoxy-β-D-pyranoside against sodium nitroprusside-induced neurotoxicity in HT22 cells

2-(4-Methoxyphenyl) ethyl-2-acetamido-2-deoxy-β-D-pyranoside (GlcNAc-Sal), the salidroside analog was synthesized and shown to inhibit hypoglycemia and serum limitation induced apoptosis in PC12 cells. This study investigated the protective effects of GlcNAc-Sal on sodium nitroprusside (SNP)-induced cytotoxicity in HT22 cells. Cell viability tests and Hoechst 33342 staining comfirmed that GlcNAc-Sal pretreatment attenuated SNP-stimulated apoptotic cell death in HT22 cells in a concentration-dependent manner. The measurements of reactive oxygen species (ROS), nitric oxide (NO) production and apoptosis-related gene and protein expression suggest that the protection of GlcNAc-Sal, shown in this study, might be mediated by inhibiting intracellular ROS and NO production, and regulating apoptosis-related gene and protein expression during SNP stimulation. Perhaps, this study might contribute to the development of GlcNAc-Sal as an agent for preventing and/or treating a variety of NO-induced brain diseases.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Positive selection in the chromosome 16 VKORC1 genomic region has contributed to the variability of anticoagulant response in humans

VKORC1 (vitamin K epoxide reductase complex subunit 1, 16p11.2) is the main genetic determinant of human response to oral anticoagulants of antivitamin K type (AVK). This gene was recently suggested to be a putative target of positive selection in East Asian populations. In this study, we genotyped the HGDP-CEPH Panel for six VKORC1 SNPs and downloaded chromosome 16 genotypes from the HGDP-CEPH database in order to characterize the geographic distribution of footprints of positive selection within and around this locus. A unique VKORC1 haplotype carrying the promoter mutation associated with AVK sensitivity showed especially high frequencies in all the 17 HGDP-CEPH East Asian population samples. VKORC1 and 24 neighboring genes were found to lie in a 505 kb region of strong linkage disequilibrium in these populations. Patterns of allele frequency differentiation and haplotype structure suggest that this genomic region has been submitted to a near complete selective sweep in all East Asian populations and only in this geographic area. The most extreme scores of the different selection tests are found within a smaller 45 kb region that contains VKORC1 and three other genes (BCKDK, MYST1 (KAT8), and PRSS8) with different functions. Because of the strong linkage disequilibrium, it is not possible to determine if VKORC1 or one of the three other genes is the target of this strong positive selection that could explain present-day differences among human populations in AVK dose requirement. Our results show that the extended region surrounding a presumable single target of positive selection should be analyzed for genetic variation in a wide range of genetically diverse populations in order to account for other neighboring and confounding selective events and the hitchhiking effect.

Novel incentive-based approaches to adherence

BACKGROUND

Adherence to medications for chronic conditions is often very low, limiting the benefit to patients, even when the medications are effective and have favorable side effect profiles.

PURPOSE

This article reviews some of the prior work on treatment adherence, introduces novel concepts from behavioral economics that can be used to design interventions to improve adherence, and proposes new approaches for clinical trials.

METHODS

Relevant experience of the authors and insights from the literature were combined to identify key issues and propose methodological improvements. Specific examples regarding adherence to warfarin are provided.

RESULTS

Several new approaches to trial design can be effectively applied in the context of medication adherence. These include tailored intervention strategies and sequential multiple assignment randomized trial (SMART) designs.

LIMITATIONS

While we have proposed to use these new approaches for ongoing studies of adherence in behavioral health, practical experience with their application is still somewhat limited.

CONCLUSIONS

Behavioral economics offer a variety of concepts that, when used in the design of interventions to improve adherence, may be more successful than traditional approaches. New clinical trial designs can also be adopted to improve the efficiency of studies that assess these approaches.

Laser-engineered dissolving microneedles for active transdermal delivery of nadroparin calcium

There is an urgent need to replace the injection currently used for low molecular weight heparin (LMWH) multidose therapy with a non- or minimally invasive delivery approach. In this study, laser-engineered dissolving microneedle (DMN) arrays fabricated from aqueous blends of 15% w/w poly(methylvinylether-co-maleic anhydride) were used for the first time in active transdermal delivery of the LMWH nadroparin calcium (NC). Importantly, an array loading of 630IU of NC was achieved without compromising the array mechanical strength or drug bioactivity. Application of NC-DMNs to dermatomed human skin (DHS) using the single-step 'poke and release' approach allowed permeation of approximately 10.6% of the total NC load over a 48-h study period. The cumulative amount of NC that permeated DHS at 24h and 48h attained 12.28±4.23IU/cm(2) and 164.84±8.47IU/cm(2), respectively. Skin permeation of NC could be modulated by controlling the DMN array variables, such as MN length and array density as well as application force to meet various clinical requirements including adjustment for body mass and renal function. NC-loaded DMN offers great potential as a relatively low-cost functional delivery system for enhanced transdermal delivery of LMWH and other macromolecules.

Synthesis and biological evaluation of two salidroside analogues in the PC12 cell model exposed to hypoglycemia and serum limitation

Salidroside is a phenylpropanoid glycoside isolated from Rhodiola rosea L., a traditional Chinese medicinal plant, and has displayed a broad spectrum of pharmacological properties. In this paper, two analogues were prepared with the glucosamine and N-acetylglucosamine as glycosyl donor, 2-(4-hydroxyphenyl)ethanol as glycosyl acceptor. The effects of them over PC12 cell model exposed to hypoglycemia and serum limitation were assessed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Flow Cytometry and Western blot analysis.

Model-based reconstructive elasticity imaging using ultrasound

Elasticity imaging is a reconstructive imaging technique where tissue motion in response to mechanical excitation is measured using modern imaging systems, and the estimated displacements are then used to reconstruct the spatial distribution of Young's modulus. Here we present an ultrasound elasticity imaging method that utilizes the model-based technique for Young's modulus reconstruction. Based on the geometry of the imaged object, only one axial component of the strain tensor is used. The numerical implementation of the method is highly efficient because the reconstruction is based on an analytic solution of the forward elastic problem. The model-based approach is illustrated using two potential clinical applications: differentiation of liver hemangioma and staging of deep venous thrombosis. Overall, these studies demonstrate that model-based reconstructive elasticity imaging can be used in applications where the geometry of the object and the surrounding tissue is somewhat known and certain assumptions about the pathology can be made.

Modest response in translation to home management of deep venous thrombosis

BACKGROUND

years may elapse between the publication of results of rigorous randomized trials and changes in clinical practice. It is not often that a definitive time interval can be identified that shows the time taken for published clinical trials to affect clinical practice. In the present study, we track the timelines of evidence for home treatment of deep venous thrombosis and its eventual impact on hospitalizations and early discharge.

METHODS

the number of patients discharged from short-stay hospitals throughout the United States between 1979 and 2006 with a principal diagnosis of deep venous thrombosis and the proportion discharged in ≤ 2 days was determined from The National Hospital Discharge Survey. We also attempted to identify all published articles that reported home treatment of deep venous thrombosis in unselected populations.

RESULTS

eleven years after demonstration of the safety and efficacy of home treatment, there was only a 21% decrease in the population-based incidence of hospitalizations of patients with a principal diagnosis of deep venous thrombosis. The proportion of patients with a principal diagnosis of deep venous thrombosis who were discharged in ≤ 2 days began to increase prominently after the 1996 publication of trials showing the safety and efficacy of home treatment, and continued to increase through 2006. However, the proportion discharged early remained modest (21% to 25%).

CONCLUSIONS

whether the slow implementation of home treatment reflects a cautious approach accompanied by a gradual testing of shortened hospitalization for deep venous thrombosis or other factors is uncertain.

Thrombocytopenia and other hot topics

A frequent issue in the management of cancer patients with thrombosis is thrombocytopenia, whether related to chemotherapy, heparin, or other drugs. The oncologist will have multiple new anticoagulants to choose from in the future, but for now, the effect of these experimental agents on cancer thrombosis is unknown. Despite the effectiveness of anticoagulation in cancer patients, survival benefit remains controversial. Given the ongoing clinical questions and new drugs, anticoagulant therapy in patients with cancer promises to have an exciting future.

Ethnic differences in warfarin maintenance dose requirement and its relationship with genetics

Warfarin is a highly efficacious drug, but management of warfarin is difficult, in part because of the large interindividual maintenance dose differences. Warfarin dose requirements differ by race and it has been suggested that some of these differences are owing to genetic diversity. For example, persons of African descent have lower allele frequencies of the CYP2C9*2 and *3 and VKORC1 1173T allele, which have been associated with lower warfarin dose requirements in Caucasians. Since there is currently debate whether genetic information should be used in clinical practice to determine the starting dose for a warfarin initiator, it is of great importance to determine whether everyone will benefit from this knowledge.

A test of financial incentives to improve warfarin adherence

Background

Sub-optimal adherence to warfarin places millions of patients at risk for stroke and bleeding complications each year. Novel methods are needed to improve adherence for warfarin. We conducted two pilot studies to determine whether a lottery-based daily financial incentive is feasible and improves warfarin adherence and anticoagulation control.

Methods

Volunteers from the University of Pennsylvania Anticoagulation Management Center who had taken warfarin for at least 3 months participated in either a pilot study with a lottery with a daily expected value of $5 (N = 10) or a daily expected value of $3 (N = 10). All subjects received use of an Informedix Med-eMonitor™ System with a daily reminder feature. If subjects opened up their pill compartments appropriately, they were entered into a daily lottery with a 1 in 5 chance of winning $10 and a 1 in 100 chance of winning $100 (pilot 1) or a 1 in 10 chance of winning $10 and a 1 in 100 chance of winning $100 (pilot 2). The primary study outcome was proportion of incorrect warfarin doses. The secondary outcome was proportion of INR measurements not within therapeutic range. Within-subject pre-post comparisons were done of INR measurements with comparisons with either historic means or within-subject comparisons of incorrect warfarin doses.

Results

In the first pilot, the percent of out-of-range INRs decreased from 35.0% to 12.2% during the intervention, before increasing to 42% post-intervention. The mean proportion of incorrect pills taken during the intervention was 2.3% incorrect pills, compared with a historic mean of 22% incorrect pill taking in this clinic population. Among the five subjects who also had MEMS cap adherence data from warfarin use in our prior study, mean incorrect pill taking decreased from 26% pre-pilot to 2.8% in the pilot. In the second pilot, the time out of INR range decreased from 65.0% to 40.4%, with the proportion of mean incorrect pill taking dropping to 1.6%.

Conclusion

A daily lottery-based financial incentive demonstrated the potential for significant improvements in missed doses of warfarin and time out of INR range. Further testing should be done of this approach to determine its effectiveness and potential application to both warfarin and other chronic medications.

Warfarin therapy: in need of improvement after all these years

BACKGROUND

Warfarin therapy has been used clinically for over 60 years, yet continues to be problematic because of its narrow therapeutic index and large inter-individual variability in patient response. As a result, warfarin is a leading cause of serious medication-related adverse events, and its efficacy is also suboptimal.

OBJECTIVE

To review factors that are responsible for variable response to warfarin, including clinical, environmental, and genetic factors, and to explore some possible approaches to improving warfarin therapy.

RESULTS

Recent efforts have focused on developing dosing algorithms that included genetic information to try to improve warfarin dosing. These dosing algorithms hold promise, but have not been fully validated or tested in rigorous clinical trials. Perhaps equally importantly, adherence to warfarin is a major problem that should be addressed with innovative and cost-effective interventions.

CONCLUSION

Additional research is needed to further test whether interventions can be used to improve warfarin dosing and outcomes.

Oral low molecular weight heparin delivery by microparticles from complex coacervation

As low molecular weight heparins exhibit limited oral absorption they usually have to be administered parenterally. Their strong negative charge appears to be one of the biggest hurdles to overcome in order to increase oral absorption. Complex coacervation has been proposed as a microencapsulation technique for increased oral drug absorption on the basis of charge compensation. Optimized tinzaparin/acacia gum mixture were coacervated with either gelatin A or B leading to microparticles with monodispersed size distribution, good fluidity and high encapsulation rates (>90%), while mean particle size varied between 5 and 20 microm, respectively, depending on the gelatin type. Tinzaparin was homogeneously distributed throughout the particle matrix and anti-Xa activity was maintained during preparation and storage. Drug release occurred in dependency of the pH triggering the dissociation between tinzaparin/acacia and gelatin. Cell binding experiments on Caco-2 led to slightly increased adhesion of gelatin A microparticles compared to gelatin B (A: 3.5+/-0.3%; B: 2.5+/-0.3%; solution: 1.9+/-0.1%), while drug transport did not differ from free tinzaparin solution. In-vivo results demonstrated an oral bioavailability of about 4.2+/-2.9% with gelatin B particles while gelatin A led to no absorption of tinzaparin. In conclusion, tinzaparin microparticles exhibited excellent particle properties in vitro and demonstrate potential for a formulation increasing the oral bioavailability of low molecular weight heparins.

Guidelines for the Early Management of Adults With Ischemic Stroke

Purpose— Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

Methods— Members of the panel were appointed by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council’s Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

Results— Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

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.

Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists

PURPOSE

Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

METHODS

Members of the panel were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council's Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

RESULTS

Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

African American race was associated with an increased risk of complications following venous thromboembolism

OBJECTIVE

Limited data exist on the quality of care for patients with venous thromboembolism (VTE), and it is unknown whether the processes and outcomes of care for this illness differ between African Americans and whites.

STUDY DESIGN AND SETTING

We retrospectively studied 168 patients hospitalized for VTE in two Veterans Affairs hospitals during fiscal years 2000-2002. Patient characteristics, information about processes of care, and medical outcomes at 90 days after the index VTE event were abstracted from medical records. We used logistic regression to explore associations between race, processes of care, and the overall 90-day complication rate (i.e., death, bleeding, or recurrent VTE), adjusting for patient baseline characteristics.

RESULTS

Multivariable analysis demonstrated that administration of warfarin within 1 day of starting heparin (odds ratio [OR] 0.20, 95% confidence interval [CI]: 0.05-0.42) and overlap of heparin and warfarin treatment >or=4 days (OR 0.09, 95% CI: 0.02-0.50) were associated with a lower complication rate, and African American race was associated with a higher complication rate (OR 5.2, 95% CI: 1.3-21.6). Race was not significantly associated with the performance of processes of care in multivariable analysis.

CONCLUSION

Although African Americans had an increased risk of complications following VTE, race was not independently associated with the use of processes of care for VTE.

Management patterns of thrombosis prophylaxis and related costs in hip and knee replacement in Germany

The objective of the study was to depict treatment strategies, health care utilisation and cost evaluation of hip and knee replacement surgery in Germany, with a particular emphasis on thrombosis prophylaxis (TP) for the prevention of deep vein thrombosis (DVT). In this multi-centre prospective cohort study, medical record data (socio-demographics, risk factors for thrombosis, thrombosis prophylaxis, course of hospital stay) were collected for patients undergoing either total hip replacement (THR) or total knee replacement (TKR). One and three months post-operatively, post-operative outcomes and health care resource use were documented by patient and physician questionnaires. A total of 309 patients participated in the study (59% female, mean age 66 [SD 10] years). Parenteral anticoagulation was administered for a mean of 38 (SD 16) days. 27 (9%) patients received subsequent oral anticoagulation for a mean of 38 (SD 21) additional days. Symptomatic DVT was reported by four (1.3%) patients. Mean overall direct costs associated with surgery from baseline to 3 months were EUR 11 264 (median 11 564, SD 2 481). Hospital and rehabilitation accounted for 97% of direct costs; costs for medications, physical therapy, physician office visits, out-of-pocket expenses, as well as complication costs accounted for an additional 3% of direct costs. Within these direct costs, a mean of EUR 348 (SD 361) was related to thrombosis prophylaxis, accounting for 3% of direct costs. Mean overall cost was EUR 11 926 (SD 2 481), including 6% indirect costs of productivity loss. Extended thrombosis prophylaxis was observed in the usual care setting of the study and associated with low incidence of symptomatic DVT. Thrombosis prophylaxis is — within the considerable economic burden of joint replacement surgery — a relatively small cost component.

Established treatments for acute ischaemic stroke

This article reviews the recommended management of patients presenting to accident and emergency departments with acute ischaemic stroke, and focuses on thrombolysis. The review includes initial management, recommended clinical, laboratory, and radiographic examinations. Appropriate general medical care, consisting of monitoring of oxygenation, fever, blood pressure, and blood glucose concentrations are examined. Criteria for thrombolysis with intravenous recombinant tissue plasminogen activator (rt-PA) are discussed. Complications of rt-PA therapy, such as haemorrhagic transformation and angio-oedema, are reviewed. An approach to management of rt-PA complications is outlined. Only a small percentage of acute ischaemic stroke patients meet criteria for rt-PA; therefore, alternative acute treatment strategies are also discussed. Acute medical and neurological complications in stroke patients are analysed, along with recommendations for treatment.

Atypical warfarin-induced skin necrosis

Warfarin-induced skin necrosis (WISN) is a disorder of unclear etiology that predominantly affects obese women. Although WISN typically occurs within the first 10 days of warfarin therapy, some patients develop the complication several years after warfarin exposure. We describe the case of a 43-year-old Caucasian woman with a history of recurrent thromboembolic disorders, protein S deficiency, and multiple exposures to warfarin who came to the emergency room with complaints of worsening dermatitis that had progressed over a 15-hour period. Examination revealed multiple, diffuse "lace-like" erythematous eruptions with superimposed lesions that were tender, ulcerated, and crusted. A biopsy was performed, and histopathologic findings were consistent with WISN. Based on the Naranjo adverse drug reaction probability scale, a probable causal relationship existed between warfarin and skin necrosis in this patient. Since treatment is generally supportive, prompt and prudent evaluation of suspicious skin lesions is necessary to prevent the serious sequelae associated with WISN.

The prevalence of nontherapeutic and dangerous international normalized ratios among patients receiving warfarin in the emergency department

STUDY OBJECTIVE

We determine the prevalence of nontherapeutic and coagulopathic international normalized ratios (INRs) among patients receiving warfarin and presenting to an emergency department (ED). As a secondary goal, we aim to determine whether a simple decision aid composed of physical examination and historical features could be predictive of INR greater than 5.

METHODS

This was a prospective, observational study at 2 associated urban academic centers from February 2003 through May 2004, using a convenience sample of patients identified by direct questioning and contemporaneous medical record review in the ED as receiving long-term warfarin therapy. Inclusion criteria were warfarin therapy and self-reported compliance. Patients were enrolled by trained researchers. The primary outcome measure was the percentage of patients within appropriate therapeutic range for their condition according to accepted national guidelines. Descriptive statistics were used, and multivariate regression analysis was performed to identify associations.

RESULTS

One thousand nineteen patients were enrolled. INR values were obtained in 77% (782/1019) of patients. Of these patients, 72% (95% confidence interval 67% to 76%) were outside the desired range. Values were less than 2 in 43% of patients and greater than 3 in 29% of patients. INR greater than 5 was present in 11% (86/782) of patients, and 40% (34/86) of these patients exhibited gross bleeding. Emergency therapy was administered in 12% (96/782) of patients: fresh frozen plasma in 7% of patients, heparin in 5% of patients. Intracranial hemorrhage was found in 12 patients, 5 with INR greater than 3. Ischemic stroke or venous thromboembolism occurred in 51 patients known to be receiving warfarin specifically for prevention of the event that occurred. Of these patients, 49% (25/51) had INR less than 2. Regression analysis indicated no sensitive or specific constellation of features, though 2 factors were associated with INR greater than 5: gross hemorrhage (P=.006) and increasing duration of therapy (P=.047).

CONCLUSION

The prevalence of undesirable INR in the ED is higher than in warfarin populations previously studied, and a significant number of nontherapeutic levels were associated with thromboembolism, stroke, or hemorrhage. Given the prevalence and established danger of subtherapeutic and supratherapeutic levels, a low threshold should be maintained for testing and addressing INR levels in patients receiving warfarin in the ED.

Critical care clotting catastrophies

Coagulation problems are very common in intensive care patients. It is important to recognize potential problems, perform a rapid assessment, and start therapy. The author reviews general clinical and laboratory approaches to diagnosis and treatment of the bleeding patient and to correction of coagulopathies. This review outlines a set of often catastrophic coagulation problems, which may present both thrombotic and bleeding challenges. These include heparin induced thrombocytopenia, thrombotic thrombocytopenic purpura, and disseminated intravascular coagulation.

Patterns of Venous Insufficiency after an Acute Deep Vein Thrombosis

BACKGROUND

The purpose of this study was to investigate patterns of venous insufficiency during a 12-month period after an acute deep vein thrombosis.

STUDY DESIGN

Seventy limbs in 67 patients with an acute deep vein thrombosis (DVT) involving 147 anatomic segments were evaluated with duplex scanning at 1 month, 3 months, 6 months, and 1 year. Venous segments were examined whether they were occluded, partially recanalized, or totally recanalized, and the development of venous reflux was evaluated.

RESULTS

The segments investigated were the common femoral vein (38 segments), femoral vein (33 segments), popliteal vein (36 segments), and calf veins (40 segments). There were 35 limbs with isolated DVT and the remaining 35 had multisegment DVT. At 1 year, thrombi had fully resolved in 76% of the segments, 20% remained partially recanalized, and 5% were occluded. The venous occlusion was most predominant in the femoral vein (21%) at 1 year. On the contrary, rapid recanalization was obtained in calf veins than in proximal veins at each examination (p < 0.01). Deep vein insufficiency was detected as early as 1 month after development of DVT, and the reflux was most predominant in popliteal veins (56%), followed by femoral veins (18%). No reflux was found in calf veins. Multisegment DVTs had a significantly higher incidence of deep vein insufficiency than single segment DVTs at 1 year. Development of superficial venous insufficiency was found in 5 limbs (7%) and perforating vein insufficiency in 5 (7%).

CONCLUSIONS

Lower extremity venous segments showed different proportions of occlusion, partial recanalization, and total recanalization. Calf veins showed more rapid recanalization than proximal veins. Venous reflux was noted as early as 1 month. The limbs involving multisegment DVTs on initial examination had a higher incidence of deep vein insufficiency and could require much longer followup studies.

Neuraxial Anesthesia and Low-Molecular-Weight Heparin Prophylaxis in Major Orthopedic Surgery in the Wake of the Latest American Society of Regional Anesthesia Guidelines

In May 2003, the Second American Society of Regional Anesthesia Consensus Conference statement was issued partly in response to continued safety concerns over the use of regional anesthesia--in particular, neuraxial techniques--with low-molecular-weight heparin (LMWH) prophylaxis in major orthopedic surgery. As the 2003 Consensus statement makes clear, regional anesthesia may be used safely with LMWH prophylaxis. The key to optimizing patient safety, however, depends on a careful calibration of the total daily dose and the timing of the first and subsequent doses of the LMWH drug with the timing and management of the regional anesthetic procedure. Because the challenge of successfully providing regional anesthesia in the presence of LMWH thromboprophylaxis is a clinical one, anesthesiologists should do what they can to ensure that every member of the surgical team has an understanding of current literature and practice guidelines such as those recently published by the American Society of Regional Anesthesia.

Quantitative assessment of thrombus burden predicts the outcome of treatment for venous thrombosis: a systematic review

PURPOSE

Clot-burden change in patients receiving anticoagulant therapy, by predicting subsequent recurrent venous thromboembolism, may provide a clinically relevant surrogate endpoint of prognostic importance. The validity of this objective measure is yet to be established.

METHODS

A PubMed search was performed to retrieve articles published up to December 2003. We identified 11 randomized trials reported from 1990 to 2003 that met our study identification and selection criteria. Anticoagulant therapy subsequently approved by regulatory affairs was assessed by clot-burden change and the validated outcome measure, long-term venous thromboembolism. Two additional randomized trials, partly meeting the inclusion criteria, were included in the sensitivity analysis.

RESULTS

Individual studies suggested a predictive relationship between clot-burden change and likelihood of recurrent venous thromboembolism irrespective of the particular anticoagulant. The summary treatment effects strongly favored the therapy under evaluation and were in harmony for improved clot-burden (relative risk 0.82; 95% CI, 0.76-0.88; P <0.001) and for recurrent venous thromboembolism (relative risk 0.56; 95% CI, 0.42-0.76; P <0.001). The aggregate data show a striking predictive correlation for clot-burden change and subsequent recurrent venous thromboembolism using meta-regression analysis; (correlation = 0.81, P = 0.005) validating quantitative clot-burden assessment.

CONCLUSION

Clot-burden change predicts long-term outcome, providing clinically relevant, patient-specific prognostic findings that may guide duration of anticoagulant therapy as well as provide a valid surrogate endpoint for clinical trials of innovative antithrombotic therapy, allowing more efficient trials exposing far fewer patients to the hazards of ineffective therapy than is required for outcome studies. Noninvasive assessment (duplex ultrasonography) of clot-burden change is currently being deployed for use in clinical trials.

Current options in the prevention of thromboembolic disease

Significant advances in the pharmacological prophylaxis of venous thromboembolism have occurred since warfarin and unfractionated heparin were introduced for this indication nearly 60 years ago. Despite these advances, coumarin derivatives such as warfarin remain the only orally active anticoagulants available for prophylaxis in venous thromboembolism. Although administered orally, coumarin derivatives are not convenient to use, because they have narrow therapeutic indexes and require routine coagulation monitoring and dose adjustment. This is inconvenient for patients and physicians and costly for the healthcare system. Low-molecular-weight heparins, which are administered in fixed or weight-adjusted doses and do not require monitoring, are widely used for the prevention of venous thromboembolism in patients in both the hospital and the outpatient setting. However, these drugs must be given subcutaneously, which can be difficult for outpatients and resource-intensive for in-hospital use. Likewise, fondaparinux, the synthetic pentasaccharide, must be administered subcutaneously. Consequently, there remains a need for new orally active anticoagulants that can be given in fixed doses and do not have a narrow therapeutic index, so that coagulation monitoring is unnecessary. Because such agents would be more convenient for patients and physicians, they would probably expand the use of prophylaxis in venous thromboembolism in those at risk, and would simplify treatment of patients with established venous thromboembolism.