D-CAT: Density and Clustering Annotation Tool for three dimensional electron microscopic volumes.

Three dimensional (3D) electron microscopy techniques have become valuable tools for investigating cellular architecture and the processes that govern it. A vast amount of information is available in every 3D tomogram but the options for presenting this information in a clear and visually appealing way are limited. To address this, we developed D-CAT; a MatLab-application to accurately visualize the distribution of membrane proteins and/or membrane-bound structures. Presence (density) and distribution (clustering, depletion) are presented as color-coded areas on membranes. By using IMOD models both as input and output format, we ensure that the application fits within workflows common in the field of 3D electron microscopy.

Acute Lower Extremity Fracture Management in Chronic Spinal Cord Injury: 2022 Delphi Consensus Recommendations.

Our objective was to develop a clinical practice guideline (CPG) for the treatment of acute lower extremity fractures in persons with a chronic spinal cord injury (SCI). Methods: Information from a previous systematic review that addressed lower extremity fracture care in persons with an SCI as well as information from interviews of physical and occupational therapists, searches of the literature, and expert opinion were used to develop this CPG. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system was used to determine the quality of evidence and the strength of the recommendations. An overall GRADE quality rating was applied to the evidence. Conclusions: Individuals with a chronic SCI who sustain an acute lower extremity fracture should be provided with education regarding the risks and benefits of operative and nonoperative management, and shared decision-making for acute fracture management should be used. Nonoperative management historically has been the default preference; however, with the advent of greater patient independence, improved surgical techniques, and advanced therapeutics and rehabilitation, increased use of surgical management should be considered. Physical therapists, kinesiotherapists, and/or occupational therapists should assess equipment needs, skills training, and caregiver assistance due to changes in mobility resulting from a lower extremity fracture. Therapists should be involved in fracture management as soon as possible following fracture identification. Pressure injuries, compartment syndrome, heterotopic ossification, nonunion, malunion, thromboembolism, pain, and autonomic dysreflexia are fracture-related complications that clinicians caring for patients who have an SCI and a lower extremity fracture may encounter. Strategies for their treatment are discussed. The underlying goal is to return the patient as closely as possible to their pre-fracture functional level with operative or nonoperative management.

Small cargo proteins and large aggregates can traverse the Golgi by a common mechanism without leaving the lumen of cisternae.

Procollagen (PC)-I aggregates transit through the Golgi complex without leaving the lumen of Golgi cisternae. Based on this evidence, we have proposed that PC-I is transported across the Golgi stacks by the cisternal maturation process. However, most secretory cargoes are small, freely diffusing proteins, thus raising the issue whether they move by a transport mechanism different than that used by PC-I. To address this question we have developed procedures to compare the transport of a small protein, the G protein of the vesicular stomatitis virus (VSVG), with that of the much larger PC-I aggregates in the same cell. Transport was followed using a combination of video and EM, providing high resolution in time and space. Our results reveal that PC-I aggregates and VSVG move synchronously through the Golgi at indistinguishable rapid rates. Additionally, not only PC-I aggregates (as confirmed by ultrarapid cryofixation), but also VSVG, can traverse the stack without leaving the cisternal lumen and without entering Golgi vesicles in functionally relevant amounts. Our findings indicate that a common mechanism independent of anterograde dissociative carriers is responsible for the traffic of small and large secretory cargo across the Golgi stack.

Energy requirements for the action of staphylococcin 1580 in Staphyloccus aureus.

1. Starved cells of a glucose-grown strain of Staphylococcus aureus are resistant to the action of staphylococcin 1580. Reinitiation of sensitivity is readily obtained upon the addition of glucose, but only weakly with L-lactate, although the latter induces higher ATP levels and supports L-glutamic acid uptake better than glucose does. The NADH/NAD+ ratio correlates with the staphylococcin sensitivity. 2. Starved pyruvate-grown cells remain partially susceptible and full sensitivity is restored both in the presence of glucose and L-lactate. 3. Arsenate but not dicyclohexylcarbodiimide (DCCD) blocks the reinitiation of sensitivity in the presence of glucose. Both arsenate and DCCD block sensitivity in the presence of L-lactate. 4. Aerobically grown cells are sensitive to staphylococcin 1580 under anaerobic conditions. Anaerobically grown cells are less susceptible, but sensitivity can be restored by glucose and also by L-lactate plus nitrate when cells are previously induced for nitrate reductase. 5. Starved cells of a mutant strain defective in the maintenance of a high-energy state of the membrane are normally sensitive in the presence of glucose, but resistant in the presence of L-lactate. A strain lacking a functional respiratory chain (men-) is also sensitive with glucose but resistant in the presence of L-lactate. 6. It is concluded that the initiation of the staphylococcin 1580 action is under control of a mechanism regulating the energy flow in the cell, and involving the presence of a high-energy phosphorylated compound.

Purification and properties of 5,10-methylenetetrahydromethanopterin dehydrogenase and 5,10-methylenetetrahydromethanopterin reductase, two coenzyme F420-dependent enzymes, from Methanosarcina barkeri.

5,10-Methylenetetrahydromethanopterin dehydrogenase and 5,10-methylenetetrahydromethanopterin reductase have been purified to homogeneity by a factor of 86 and 68, respectively, from methanol-grown Methanosarcina barkeri cells. The dehydrogenase was isolated as a hexamer of a single 35 kDa subunit, whereas the reductase was composed of four identical 38 kDa subunits. The purified oxygen-stable enzymes catalyzed the oxidation of 5,10-methylenetetrahydromethanopterin and methyltetrahydromethanopterin with Vmax values of 3000 and 200 mumol min-1 mg-1, respectively. The methanogenic electron carrier coenzyme F420 was a specific electron acceptor for both enzymes. Steady state kinetics for the two enzymes were in agreement with ternary complex (sequential) mechanisms. Methylene reductase and methylene dehydrogenase are proposed to function in the methanol oxidation step to CO2.

Lobular patterns of expression and enzyme activities of glutamine synthase, carbamoylphosphate synthase and glutamate dehydrogenase during postnatal development of the porcine liver.

Carbamoylphosphate synthase and glutamine synthase show a complementary distribution in the liver lobule of the rat. In the human liver lobule, which is approximately 2-fold larger than that of the rat, an intermediate, 'empty' zone is present between the periportal carbamoylphosphate synthase-positive and the pericentral glutamine synthase-positive zone. To investigate whether these differences in gene expression can be attributed to the size of the liver lobule, we investigated the patterns of expression of carbamoylphosphate synthase, glutamine synthase and glutamate dehydrogenase during postnatal development of the pig, a species in which the total number of lobules does not increase after birth. We demonstrate that lobular size increases 3-fold between 1 week and 8 months after birth. In the same developmental period the number of hepatocytes on the porto-central axis increases 2-fold, resulting in a 3-fold increase in cellular volume. However, the lobular patterns of expression of carbamoylphosphate synthase, glutamate dehydrogenase and glutamine synthase do not change anymore after 1 month, i.e., when lobular diameter is comparable to that in rat liver, showing that lobular size is not a major determinant of the heterogeneous patterns of expression of these enzymes. The adult patterns of expression of glutamine synthase, glutamate dehydrogenase and, in particular carbamoylphosphate synthase in the porcine liver resemble those of man. Changes in the enzyme activities of glutamate dehydrogenase and carbamoylphosphate synthase are not related to the lobular size. However, the 70% decrease of GS activity in the 8-month-old pigs corresponds with the gradual 2-3-fold decrease in the size of the GS-positive compartment during postnatal development. During adulthood GS activity increases again to values observed 1 week after birth demonstrating a 2-fold increase in cellular glutamine synthase content. The present data show that the pig is an excellent model to study the regulation and functional implication of zonation of gene expression in the human liver.

cDNA sequence of the long mRNA for human glutamine synthase.

Screening a human liver cDNA library in lambda ZAP revealed several clones for the mRNA of glutamine synthase. The longest clone was completely sequenced and consists of a 109 bp 5' untranslated region, a 1119 bp protein coding region, a 1498 bp 3' untranslated region and a poly(A) tract of 12 bp.

Predictors of the post-thrombotic syndrome during long-term treatment of proximal deep vein thrombosis.

BACKGROUND: The post-thrombotic syndrome is a chronic, poorly understood complication of deep venous thrombosis (DVT). OBJECTIVES: To evaluate predictors of the post-thrombotic syndrome, including intensity of long-term anticoagulation, and to assess the impact of the post-thrombotic syndrome on quality of life. PATIENTS AND METHODS: The setting was 13 Canadian hospitals and one US hospital. One hundred and forty-five patients with an unprovoked episode of proximal DVT who were initially treated with 3 months of conventional-intensity warfarin [target International Normalized Ratio (INR) of 2.5] then participated in a trial comparing two intensities of long-term warfarin therapy (target INR 2.5 vs. INR 1.7). Post-thrombotic syndrome was assessed at the end of the trial using a validated clinical scale. Generic and venous disease-specific quality of life was compared in patients with and without the post-thrombotic syndrome. Multivariable regression analyses were performed to identify predictors of the post-thrombotic syndrome and of its severity. RESULTS: After an average follow-up of 2.2 years, the prevalence of post-thrombotic syndrome was 37% and of severe post-thrombotic syndrome was 4%. Quality of life was worse in patients with the post-thrombotic syndrome compared with patients who did not have it. The presence of factor (F)V Leiden or the prothrombin gene mutation was an independent predictor of both a lower risk (P = 0.006) and reduced severity (P = 0.045) of the post-thrombotic syndrome. Intensity of anticoagulation did not influence the risk of developing the post-thrombotic syndrome. CONCLUSIONS: The post-thrombotic syndrome is a frequent and burdensome complication of proximal DVT, even among patients maintained on long-term oral anticoagulation. While the presence of FV Leiden or prothrombin gene mutation appears to be associated with a reduced risk of post-thrombotic syndrome, this finding requires further evaluation in prospective studies.

Neither baseline tests of molecular hypercoagulability nor D-dimer levels predict deep venous thrombosis in critically ill medical-surgical patients.

OBJECTIVE: Predicting patients who are harboring asymptomatic deep venous thrombosis (DVT), or who are at particular risk of developing DVT, is a desirable clinical goal since prevention or early treatment of DVT might reduce the risk of fatal pulmonary embolism. Thus validation of simple laboratory tests that reliably predict venous thromboembolism (VTE) would be clinically very important. Tests that might be useful for these applications include markers of hypercoagulability (predicting patients at risk of DVT) and D-dimer (predicting which patients may have acute DVT). METHODS: In a prospective cohort study we measured a panel of hypercoagulability markers at the time of ICU admission, and six commercial D-dimer assays were performed serially during the ICU stay in medical-surgical ICU patients who were screened for DVT with biweekly lower limb compression ultrasonography. Ultrasonography was also performed at the time of any clinically suspected DVT events. We matched cases with DVT with controls without DVT for length of stay in the ICU to generate receiver operating characteristics (ROC) curves. RESULTS: One hundred ninety-seven patients were enrolled. Blood was collected on a total of 763 occasions (median number of occasions per patient: 3, range 1-21). None of the assays predicted DVT, as indicated by the areas under the ROC curves, that did not differ significantly from 50%. CONCLUSION: In critically ill patients, neither tests of hypercoagulability nor D-dimer levels predict patients at risk of DVT and thus they should not be used to guide diagnostic testing for DVT.

Economic analysis of low-dose heparin vs the low-molecular-weight heparin enoxaparin for prevention of venous thromboembolism after colorectal surgery.

BACKGROUND: Low-dose heparin and low-molecular-weight heparin are effective strategies for preventing venous thromboembolism in colorectal surgery. The economic attractiveness of these 2 strategies in North America is unknown. We conducted an economic analysis of low-dose heparin calcium compared with enoxaparin sodium, a low-molecular-weight heparin, for thromboembolism prophylaxis after colorectal surgery. METHODS: We used decision analysis, with an economic perspective of a third-party payer. Efficacy data were obtained from the Canadian Multicentre Colorectal Deep Vein Thrombosis Prophylaxis Trial and a literature review. Canadian costs for diagnosis and treatment of deep vein thrombosis (DVT), pulmonary embolism (PE), and major bleeding were obtained from chart review and a national hospital database of colorectal surgery; American costs were obtained from published literature. The main outcomes were incremental benefits (symptomatic DVTs, symptomatic PEs, and major bleeding events avoided) and incremental costs for every 1000 patients treated. RESULTS: In the Canadian Colorectal Trial, the relative risk of DVT and PE for enoxaparin compared with low-dose heparin was 1.0 (95% confidence interval, 0.7-1.5), and the relative risk of major bleeding was 1.8 (95% confidence interval, 0.8-3.9). With the use of these data in the baseline analysis, a strategy of enoxaparin prophylaxis was associated with equal numbers of symptomatic DVTs and PEs, and an excess of 12 major bleeding episodes for every 1000 patients treated, with an additional cost of $86 050 (Canadian data) or $145 667 (US data). In a sensitivity analysis using optimal assumptions for efficacy and safety of enoxaparin (relative risk of DVT, 0.8; relative risk of PE, 0.4; relative risk of major bleeding, 1.0), a strategy of enoxaparin prophylaxis was associated with 0.8 fewer symptomatic DVT, 3 fewer symptomatic PEs, and equal numbers of major bleeding episodes for every 1000 patients treated, with an additional cost of $15 217 (Canadian data) or $107 614 (US data). CONCLUSION: Although heparin and enoxaparin are equally effective, low-dose heparin is a more economically attractive choice for thromboembolism prophylaxis after colorectal surgery.

The incidence of symptomatic venous thromboembolism during and after prophylaxis with enoxaparin: a multi-institutional cohort study of patients who underwent hip or knee arthroplasty. Canadian Collaborative Group.

BACKGROUND: Despite low molecular weight heparin prophylaxis, the incidence of venographically detected, residual deep vein thrombosis after hip and knee arthroplasty remains high, at approximately 15% and 30%, respectively. Most of these thrombi are asymptomatic and of unknown clinical significance. Nevertheless, because they have the potential to grow, limiting prophylaxis to the in-hospital period may provide inadequate protection. METHODS: We studied a cohort of 1984 consecutive patients who had hip or knee arthroplasty at 1 of 28 participating hospitals. Patients received enoxaparin prophylaxis, 30 mg subcutaneously every 12 hours for up to 14 days, and underwent predischarge compression ultrasonography. Study end points were symptomatic deep vein thrombosis or pulmonary embolism during and after prophylaxis, asymptomatic venous thrombosis detected by predischarge compression ultrasonography, and major hemorrhage. The duration of follow-up was 84 days. RESULTS: Enoxaparin treatment was started a mean (+/- SD) of 17.9 +/- 10.4 hours after the completion of surgery and was given for a mean of 18.0 +/- 6.9 doses. Eighty-two patients (4.1%; 95% confidence interval, 3.3%-5.0%) developed venous thromboembolism. The rates of thromboembolic events during and after prophylaxis were 2.1% and 2.0%, respectively. Only 3 patients (0.15%) had abnormal predischarge compression ultrasonography. Three patients (0.15%) died of pulmonary embolism. Major hemorrhage occurred in 58 patients (2.9%; 95% confidence interval, 2.2%-3.7%). CONCLUSIONS: Postoperative prophylaxis with enoxaparin for a mean of 9 days is associated with a clinically acceptable rate of symptomatic venous thromboembolism and major hemorrhage. Predischarge compression ultrasonography cannot be justified.

Deep vein thrombosis and its prevention in critically ill adults.

BACKGROUND: Our objective was to systematically review the incidence of deep vein thrombosis (DVT) and the efficacy of thromboprophylaxis in critically ill adults, including patients admitted to intensive care units and following trauma, neurosurgery, or spinal cord injury. METHODS: Two authors independently searched MEDLINE, EMBASE, abstract databases, and the Cochrane database. Data were extracted independently in triplicate. RESULTS: Ten percent to 30% of medical and surgical intensive care unit patients develop DVT within the first week of intensive care unit admission. The use of subcutaneous low-dose heparin reduced the rate by 50% compared with no prophylaxis. Approximately 60% of trauma patients developed DVT within the first 2 weeks of admission. Use of unfractionated heparin appears to decrease the incidence of DVT by only 20%, whereas low-molecular-weight heparin decreases the incidence by a further 30%. The estimated prevalence of DVT in neurosurgical patients not given prophylaxis is 22% to 35%. Mechanical prophylaxis is efficacious, with a pooled odds ratio in 5 randomized trials of 0.28. Use of low-molecular-weight heparin has been investigated as an adjunct to mechanical prophylaxis with a pooled odds ratio of 0.59 compared with graduated compression stockings alone. The incidence of DVT without prophylaxis in acute spinal cord injury patients is likely in excess of 50% to 80%. Studies of prophylaxis in these patients are too sparse to come to any definitive conclusion. CONCLUSIONS: Critically ill patients commonly develop DVT, with rates that vary from 22% to almost 80%, depending on patient characteristics. Methods of prophylaxis proven in one group do not necessarily generalize to other critically ill patient groups. More potent prophylactic regimens other than unfractionated or low-molecular-weight heparins alone may be needed with higher-risk groups.

Comparison of 1 month with 3 months of anticoagulation for a first episode of venous thromboembolism associated with a transient risk factor.

BACKGROUND: The risk of recurrence is lower after treatment of an episode of venous thromboembolism associated with a transient risk factor, such as recent surgery, than after an episode associated with a permanent, or no, risk factor. Retrospective analyses suggest that 1 month of anticoagulation is adequate for patients whose venous thromboembolic event was provoked by a transient risk factor. METHODS: In this double-blind study, patients who had completed 1 month of anticoagulant therapy for a first episode of venous thromboembolism provoked by a transient risk factor were randomly assigned to continue warfarin or to placebo for an additional 2 months. Our goal was to determine if the duration of treatment could be reduced without increasing the rate of recurrent venous thromboembolism during 11 months of follow-up. RESULTS: Of 84 patients assigned to placebo, five (6.0%) had recurrent venous thromboembolism, compared with three of 81 (3.7%) assigned to warfarin, resulting in an absolute risk difference of 2.3%[95% confidence interval (CI) - 5.2, 10.0]. The incidence of recurrent venous thromboembolism after discontinuation of warfarin was 6.8% per patient-year in those who received warfarin for 1 month and 3.2% per patient-year in those who received warfarin for 3 months (rate difference of 3.6% per patient-year; 95% CI - 3.8, 11.0). There were no major bleeds in either group. CONCLUSION: Duration of anticoagulant therapy for venous thromboembolism provoked by a transient risk factor should not be reduced from 3 months to 1 month as this is likely to increase recurrent venous thromboembolism without achieving a clinically important decrease in bleeding.

Image analysis and image processing as tools to measure initial rates of enzyme reactions in sections: distribution patterns of glutamate dehydrogenase activity in rat liver lobules.

To analyze regional differences in the activity of glutamate dehydrogenase in rat liver in situ, we developed an image recording and processing system for monitoring the formation of a colored final reaction product in time. All absorbance measurements of test and control reactions in time in consecutive sections were used to fit the data to a quadratic curve, with the derivative at t = 0 representing the initial velocity of formazan formation. The images of sections incubated for test and control reactions were topographically matched with an affine transformation using the positions of vessels as fiducials. Specific enzyme activity was calculated by subtracting the coefficients representing the initial velocity at corresponding locations in the test and control reactions and appeared to be 8 and 4 mumoles glutamate converted per min per cm3 of tissue at 20 degrees C in pericentral and periportal zones of fasted female rats, respectively. Those values are in agreement with biochemical data. The ability to construct two-dimensional images of cellular distribution patterns of enzyme activity in liver lobules is particularly useful for the study of metabolic zonation in this organ.

Complementary distribution of carbamoylphosphate synthetase (ammonia) and glutamine synthetase in rat liver acinus is regulated at a pretranslational level.

We studied the distribution of the mRNAs for carbamoylphosphate synthetase (ammonia) and glutamine synthetase in frozen sections of adult rat liver by in situ hybridization to [35S]-labeled cDNA probes. The density of silver grains resulting from hybridization to the labeled cDNA probe for carbamoylphosphate synthetase is highest around the portal venules, decreases towards the central venule, and is virtually absent from an area two to three cells wide that lines the central venules in which mRNA for glutamine synthetase is predominantly localized. Therefore, both mRNAs show the same complementary distribution within the liver acinus that was found for the proteins they encode, demonstrating that compartmentalization of the expression of these enzymes is controlled at a pretranslational level. In addition, we found that carbamoylphosphate synthetase mRNA is present mainly in the epithelium of the crypts of the proximal part of the small intestine, whereas carbamoylphosphate synthetase protein is present in the epithelium of both crypts and villi.

Gender-dependent regulation of glutamate dehydrogenase expression in periportal and pericentral zones of rat liver lobules.

We studied the level(s) at which glutamate dehydrogenase (GDH; EC 1.4.1.2) expression is regulated in the livers of fed male and female rats. The cellular content of GDH mRNA, protein, and enzyme activity was determined quantitatively using image analysis for measurement of the absorbance in consecutive serial sections that were processed for in situ hybridization, immunohistochemistry, and enzyme histochemistry. In both males and females, GDH protein and activity patterns were similar, with pericentral values being twice as high as periportal values. GDH mRNA distribution patterns in female liver lobules reflected those of GDH protein and activity, but GDH mRNA distribution patterns in male rat livers were found to be homogeneous owing to a more than twofold lower cellular mRNA content in pericentral zones than in female rats. We conclude that gender affects GDH expression selectively in pericentral zones at posttranscriptional and pretranslational levels.

In situ measurement of glutamate concentrations in the periportal, intermediate, and pericentral zones of rat liver.

We developed a quantitative histochemical assay for measurement of local glutamate concentrations in cryostat sections of rat liver. Deamination of glutamate by glutamate dehydrogenase (GDH) was coupled to the production of formazan and formazan precipitation was used for colorimetric visualization. The method was tested and validated with gelatin model sections with known glutamate concentrations. Calibration graphs showed linear relationships with high correlation coefficients (> 96%) between glutamate concentrations or section thickness and absorbance values. The method was reproducible, with a constant percentage of 60 +/- 5% of glutamate being converted in gelatin model sections containing glutamate concentrations of 2 mM and higher. Glutamate concentrations were estimated in periportal, intermediate, and pericentral zones of liver lobules that contain low, intermediate, and high GDH activity, respectively. In fed adult male rat livers, periportal zones contained the highest concentrations of glutamate (approximately 14 mM) and intermediate and pericentral zones approximately 13 and 9 mM, respectively. On starvation, glutamate concentrations increased only in the small rim of pericentral cells that express glutamine synthetase, to approximately 15 mM. In livers of fetal and newborn rats, glutamate was homogeneously distributed, with a concentration of approximately 5 mM. In suckling rat liver, distribution of glutamate was still homogeneous but the concentration was increased to approximately 8 mM. These glutamate distribution patterns were in agreement with those detected immunohistochemically.

The occurrence of subsequent malignancy in patients presenting with deep vein thrombosis: results from a historical cohort study.

BACKGROUND: Several studies have reported that patients who present with idiopathic deep vein thrombosis (DVT) have an increased risk of subsequently developing cancer. A clinical trial had previously been conducted examining the optimal duration of oral anticoagulant therapy following initial heparin treatment in patients with proximal DVT. METHODS: A historical cohort study was performed on patients enrolled in the duration of anticoagulant trial. Patients known to have cancer at the time of entry into the trial were excluded. The qualifying DVTs were classified as idiopathic (no known associated risk factors) or secondary without knowledge of subsequent recurrent venous thrombosis or cancer. The patients were then followed for the development of cancer. RESULTS: Thirteen (8.6%) of the 152 patients in the idiopathic cohort subsequently developed cancer compared to eight (7.1%) of 112 patients in the secondary cohort, P = 0.86. Two (5.4%) of 37 patients with recurrent venous thromboembolism and 19 (8.4%) of 227 patients without recurrent thromboembolism developed cancer, P = 0.7. CONCLUSION: Our study did not detect an increased risk of subsequent cancer in patients presenting with idiopathic DVT compared to secondary DVT; nor did we detect an increased incidence of cancer in patients with recurrent venous thromboembolism. Further studies are required prior to pursuing a policy of aggressive screening for cancer in patients with idiopathic venous thromboembolism.

Prevention of deep vein thrombosis after major knee surgery--a randomized, double-blind trial comparing a low molecular weight heparin fragment (enoxaparin) to placebo.

Consecutive patients undergoing knee arthroplasty or tibial osteotomy at four participating hospitals received either enoxaparin, 30 mg subcutaneously every 12 h (n = 66) or an identical-appearing placebo (n = 65). All study medications started the morning after the operation and were continued up to a maximum of 14 days. Patients underwent surveillance with 125I-fibrinogen leg scanning and impedance plethysmography. Bilateral contrast venography was performed routinely at Day 14 or at time of discharge, if sooner. Deep vein thrombosis was detected by venography in 35 of 54 patients (65%) in the placebo group and in 8 of 41 patients in the enoxaparin group (19%), a risk reduction of 71%, P less than 0.0001. For the entire study group, deep vein thrombosis was detected by either venography of non-invasive tests in 37 of 64 patients (58%) in the placebo group and in 11 of 65 patients (17%) in the enoxaparin group, a risk reduction of 71%, P less than 0.0001. Proximal vein thrombosis was found in 19% of the placebo patients and in none of the enoxaparin patients, a risk reduction of 100%, P less than 0.001. Bleeding complications occurred in 5 of 65 patients (8%) in the placebo group and in 4 of 66 patients (6%) in the enoxaparin group, P = 0.71. There were no differences in the amount of blood loss, minimum hemoglobin levels and number of units of packed red cells given between the two treatment groups. We conclude that a fixed dose regimen of enoxaparin, started post-operatively, is an effective and safe regimen for reducing the frequency of deep vein thrombosis after major knee surgery.

Optimal duration of oral anticoagulant therapy: a randomized trial comparing four weeks with three months of warfarin in patients with proximal deep vein thrombosis.

The optimal duration of oral anticoagulant therapy for patients with acute proximal deep vein thrombosis (DVT) is uncertain. Based on the hypothesis that a normal impedance plethysmogram (IPG) following DVT defines a group of patients at low risk of recurrent venous thromboembolism (VTE), a trial was conducted to evaluate the efficacy of only four weeks of warfarin. Patients with venographically confirmed acute proximal DVT who had received four weeks of warfarin after initial heparin and whose four week IPG was normal were allocated to either continue warfarin (targeted International Normalized Ratio 2.0 to 3.0) for a further eight weeks or receive placebo. Patients with an abnormal four week IPG received warfarin for a further eight weeks. Based on clinical characteristics at the time of the qualifying thrombosis, all patients were classified as having either continuing or transient risk factors for recurrent VTE. During the eight weeks following randomization, nine (8.6%) of the 105 placebo patients developed recurrent VTE compared to one (0.9%) of the 109 warfarin patients, P = 0.009. Over the entire 11 months of follow-up, 12 placebo patients developed recurrence compared to seven warfarin patients, P = 0.3. Nineteen of the 192 patients with an abnormal four week IPG experienced recurrence during the nine months after discontinuing warfarin. In the 301 patients who received three months of warfarin in the randomized trial or in the cohort study, all 26 recurrent events were in the 212 patients with continuing risk factors.(ABSTRACT TRUNCATED AT 250 WORDS)