Initiation Of Thromboprophylaxis Research Articles

Risk factors and distribution of symptomatic venous thromboembolism in total hip and knee replacements: prospective study

Venous thromboembolism (VTE) is a common complication of orthopaedic surgery in the industrialised world; though there may be variability between population groups. This study aims to define the incidence and risk factors for symptomatic VTE following primary elective total hip and knee arthoplasty surgery in a single centre in Eastern Europe. This prospective study included 499 adult patients undergoing total hip and knee arthroplasty for symptomatic osteoarthritis over a two-year period at the Clinic of Orthopaedic Surgery and Traumatology, Belgrade. The overall rate of confirmed symptomatic VTE during hospitalisation was 2.6%. According to the univariate logistic regression, an age greater than 75years (OR = 3.08; 95%CI = 1.01-9.65), a family history of VTE (OR = 6.61; 95% CI = 1.33-32.90), varicose veins (OR = 3.13; 95% CI = 1.03-9.48), and ischemic heart disease (OR = 4.93; 95% CI = 1.61-15.09) were significant risk factors for in-hospital VTE. A family history of VTE and ischemic heart disease were independent risk factors according to multivariate regression analysis. Preoperative initiation of pharmacological thromboprophylaxis (p = 0.03) and a longer duration of thromboprophylaxis (p = 0.001) were protective for postoperative DVT. Though thromboprophylaxis was safe, with very few patients suffering major haemorrhage or heparin-induced thrombocytopenia, there was a general reluctance by our local surgeons to use prolonged thromboprophylaxis. VTE is common following hip and knee arthroplasty surgery. Orthopaedic patients with a family history of VTE, heart failure and coronary heart disease are at a considerable risk of thromboembolic complications in the postoperative period. There may be a role for preoperative thromboprophylaxis in addition to prolonged postoperative treatment.

The Timing of Drug Administration for Thromboprophylaxis Following Orthopaedic Surgery: Evidence and Controversies Related to Treatment Initiation and Duration

Patients undergoing major orthopaedic surgery of the lower extremities or spine are at increased risk of venous thromboembolism (VTE). Although consensus exists as to the need for routine thromboprophylaxis in high risk patients, some aspects of this approach, such as the timing of the first dose and overall duration of the anticoagulation regimen, are subject to debate. Reviewing the available literature, there appears to be little evidence to support initiation of thromboprophylaxis more than 12 hours before surgery. Perioperative thromboprophylaxis (2 hours pre to 6 hours post -op) has been associated with an increased risk of bleeding complications whilst initiating prophylaxis more than 12 hours after surgery appears to increase the incidence of subsequent thromboembolic complications. Overall evidence would appear to support initiation of thromboprophylaxis 6 to 9 hours postoperatively, though further confirmatory studies investigating this variable in isolation would be useful to guide clinical decision making. Although evidence exists supporting extended duration thromboprophylaxis after major orthopaedic procedures, further evidence is required, using clinically important end points, prior to adoption of such an approach in all patients. Stratification of prophylaxis duration, based on risk factors for thromboembolic or bleeding complications, would seem a more rational approach than strict adherence to guidelines.

Preoperative versus postoperative initiation of thromboprophylaxis following major orthopedic surgery: safety and efficacy of postoperative administration supported by recent trials of new oral anticoagulants.

In European countries, low-molecular-weight heparin is generally initiated preoperatively for thromboprophylaxis in hip or knee replacement surgery. The objective of this review is to compare pre- and postoperative thromboprophylaxis strategies using available evidence, and discuss the challenges and issues that arise. Surgery is the first step in the process of thrombus formation, but thrombosis is not an instant process and the formation and growth of the thrombus can take several days or weeks. Hence, it may be possible to stop this process if thromboprophylaxis is initiated after surgery. Meta-analyses or systematic reviews comparing pre- and postoperative initiation of therapy have found no consistent differences in efficacy and similar safety (bleeding rates) between the two strategies. The recently available oral anticoagulant dabigatran etexilate provides thromboprophylaxis when administered postoperatively and is as safe as preoperative enoxaparin. Further support for the use of postoperative oral thromboprophylaxis in hip or knee replacement surgery has been provided by the phase III clinical trials of rivaroxaban and apixaban versus preoperative enoxaparin. Postoperative thromboprophylaxis offers the opportunity to change management practices in Europe. As postoperative initiation may have a clinical benefit in some settings (e.g. for neuraxial anesthesia) and practical advantages (e.g. allowing same-day admission), it is a worthwhile thromboprophylactic strategy for hip or knee replacement surgery.

Management strategies in patients with high bleeding and clotting risk

Patients undergoing major orthopaedic surgery are at high risk of venous thromboembolism (VTE), with morbid and potentially fatal consequences. Anticoagulant VTE prophylaxis reduces rates of postoperative deep vein thrombosis by up to 60-70% in these patients. Therefore, pharmacological prophylaxis with low-molecular-weight heparins (LMWHs), vitamin K antagonists, or fondaparinux and now new oral anticoagulants, is recommended by current guidelines. However, there remains an ongoing debate regarding when to initiate prophylaxis, and the optimal duration for prophylaxis. The benefit-to-risk ratio associated with pre- and postoperative initiation of thromboprophylaxis in cases of neuraxial anaesthesia has to be debated. As the main route of elimination for many anticoagulants is via the kidney, some patients with impaired renal function receiving thromboprophylaxis may experience increased surgical bleeding, which may have a detrimental effect on clinical and functional outcome. Age also influences bleeding risk. Older patients have more co-morbidities and an increased risk of venous and arterial thromboembolic complications and death compared with younger patients. At the same time, there is an inverse relationship between renal function and age. Therefore, an appropriate antihaemostatic dosing regimen appears to be particularly pertinent for these patients. Providing optimal thromboprophylaxis throughout the critical thrombosis period where a patient is at risk for VTE will ensure the best possible reductions in VTE related morbidity and mortality.

Clinical Experience with Bemiparin

Subcutaneous bemiparin has been evaluated for the prevention of venous thromboembolism (VTE) in moderate to high-risk patients undergoing surgery, and for the acute and long-term treatment of established VTE. General and orthopaedic surgery is associated with VTE incidence rates of 15-60% in the absence of thromboprophylaxis and this can be reduced by over 70% with appropriate thromboembolic prophylaxis. Bemiparin was as effective as unfractionated heparin (UFH) in the prevention of VTE, when both were initiated preoperatively, but was associated with significantly fewer bleeding episodes than UFH. Bemiparin prophylaxis initiated postoperatively was at least as effective as bemiparin initiated preoperatively and was associated with a lower incidence of bleeding complications than preoperative initiation. In terms of patients with cancer undergoing abdominal or pelvic surgery, preliminary results from a recent study with bemiparin showed that extended prophylaxis for 4 weeks significantly reduced the rate of major VTE, without increasing bleeding risk, compared with prophylaxis for one week. Bemiparin, initiated postoperatively, was as effective as enoxaparin, initiated preoperatively, in the prevention of VTE in patients undergoing total knee replacement. The incidence of bleeding complications was similar between groups, although the incidence of injection site haematoma was significantly higher with enoxaparin than with bemiparin. Postoperative initiation of bemiparin thromboprophylaxis minimized the risk of spinal haematoma in patients using neuraxial anaesthesia (approximately 93% of patients). In addition, postoperative initiation is likely to reduce the total costs, because patients do not need to be admitted to hospital the day before surgery. Bemiparin was more effective than intravenous UFH in the acute treatment of established deep vein thrombosis (DVT) and was as effective as oral warfarin in the subsequent secondary prevention of VTE over 3 months of therapy, while bleeding complications over 3 months of therapy were similarly low. In a European study, acute treatment of DVT with bemiparin for one week followed by 12 weeks' secondary prevention with bemiparin (i.e. bemiparin/bemiparin) was associated with a cost saving of &U20AC;908 per patient compared with UFH/warfarin. Similarly, bemiparin/warfarin produced a cost saving of &U20AC;769 compared with UFH/warfarin. The savings were predominantly the result of reduced hospital stays during acute treatment with bemiparin. Bemiparin was also associated with increased quality-adjusted life expectancy. Observational studies in routine clinical practice demonstrated that outpatient treatment of acute VTE was as effective as inpatient treatment, but with lower costs, and bemiparin was as effective as vitamin K antagonists over 3 months for secondary prevention, with VTE recurrence rates of 0% and 0.3% over 3 months in separate studies. Bemiparin is thus an effective, well tolerated agent for thromboprophylaxis in surgery, and for the acute and long-term treatment of established VTE, having advantages over UFH and particular benefits as a result of initiating therapy postoperatively.

The ‘‘Critical Thrombosis Period’’ in Major Orthopedic Surgery: When to Start and When to Stop Prophylaxis

Patients undergoing major orthopedic surgery are at high venous thromboembolism (VTE) risk, with morbid and potentially fatal consequences. Anticoagulant VTE prophylaxis reduces rates of postoperative deep vein thrombosis by up to 60% to 70% in these patients. Therefore, pharmacological prophylaxis with low-molecular-weight heparins (LMWHs), vitamin K antagonists, or fondaparinux is recommended by current guidelines. However, there remains an ongoing debate regarding when to initiate and the optimal duration for prophylaxis. Here, we discuss the mechanisms underlying thrombus formation in patients undergoing major orthopedic surgery, and we review the current literature on the benefit-to-risk ratio associated with preoperative and postoperative initiation of thromboprophylaxis and also the benefit-to-risk ratio in cases of neuraxial anesthesia. We also discuss the duration of postoperative VTE risk following major orthopedic surgery and assess the ''critical thrombosis period'' when prophylaxis should be provided. Current literature reflects the need to balance the improved efficacy of initiating prophylaxis close to the surgery with increased risk of perioperative bleeding. Evidence from pathology, epidemiology, and clinical studies suggests the risk period for VTE begins at surgery and extends well beyond hospitalization-a crucial issue when considering how long to give prophylaxis-and, in the case of total hip arthroplasty, for at least 3 months after surgery. Literature supports the greater use of ''just-in-time'' thromboprophylaxis initiation and after-discharge continuation of optimal prophylaxis in orthopedic surgery patients. Providing optimal thromboprophylaxis throughout the critical thrombosis period where a patient is at VTE risk will ensure the best reductions in VTE-related morbidity and mortality.

Live Term Birth and Two Ongoing Viable Pregnancies with Therapeutic Enoxaparin and Aspirin After Failure of Prophylactic Enoxaparin and Aspirin in Two Women with Thrombophilia and Recurrent Pregnancy Loss.

Abstract 4184The combination of prophylactic heparin and low-dose aspirin was shown in the 1990s to improve pregnancy outcome in patients with antiphospholipid antibodies and recurrent pregnancy loss (RPL). Antiphospholipid antibodies induce placental thrombosis. When associations between hereditary thrombophilias and RPL were reported in the early 2000s, we and other physicians (Rodger MA J Obstr Gyn Canada 2002) began empirically prescribing prophylactic low molecular weight heparin, low-dose aspirin, or the combination to pregnant women with thrombophilia and unexplained RPL. We observed high live birth rates. Data emerged showing live birth rates of 70.2-94% in pregnant women with RPL treated with low-dose low molecular weight heparin and/or low-dose aspirin. Only one report has addressed treatment after failure of low-dose low molecular weight heparin: Brenner and colleagues (Thromb Haemost 2000) treated 3 pregnant women with multiple thrombophilic defects with enoxaparin 60 mg x 2/day after failure of enoxaparin 40 mg x 2/day; all 3 pregnancies yielded live births. We report cases of a live term birth and two ongoing viable pregnancies with therapeutic enoxaparin,1.5 mg/kg SC, (TEP) and aspirin after failure of prophylactic enoxaparin, 40 mg SC, (PEP) and aspirin in two women with thrombophilia and RPL.A 33 year-old woman with a history of 2 unexplained miscarriages at 6 weeks (Patient 1) and a 42 year-old woman with a history of 3 unexplained miscarriages at 8 weeks (Patient 2) presented in April 2006 and in August 2007 respectively. Uterine malformations, acquired uterine defects, and hormonal abnormalities were ruled out. Parental karyotypes were normal. Thrombophilia evaluation included: factor V Leiden, prothrombin gene mutation, methylene tetrahydrofolate reductase (MTHFR) gene mutation, fasting homocysteine, protein C, protein S, antithrombin, IgG anticardiolipin antibody, IgM anticardiolipin antibody, lupus anticoagulant, plasminogen activator inhibitor-1 (PAI-1), and PAI-1 4G/5G polymorphism. Positive results were: one copy each of the C677T and A1298C MTHFR mutations in Patient 1 and Patient 2; PAI-1 120 ng/mL and PAI-1 4G/4G polymorphism in Patient 2. The following describes the clinical course in both patients.Patient 1 was started on aspirin 81 mg daily and on clomiphene citrate to improve fertility. She conceived but miscarried at 7 weeks in June 2006. She underwent in vitro fertilization (IVF) in December 2006 while continuing on aspirin. She started on PEP daily within 24 hours of egg retrieval. She miscarried twins at 6 and 8&1/2 weeks. In May 2007, she conceived through IVF while continuing on aspirin. She started on TEP daily within 24 hours of egg retrieval. Anti-Xa level was monitored monthly. Enoxaparin was adjusted to maintain the anti-Xa level between 0.6 and 1.2 ui/mL. She delivered a healthy term baby on January 10, 2008. She continued to take aspirin daily. She conceived naturally in February 2009. She started on TEP daily with monthly anti-Xa monitoring when her pregnancy was confirmed. She currently has a live 24-week gestation.Patient 2 was started on aspirin 81 mg daily. She conceived through IVF in May 2008. She started on PEP daily within 24 hours of egg retrieval. She miscarried in a few weeks. She conceived through IVF in October 2008 while continuing on aspirin. She started on PEP daily within 24 hours of egg retrieval. After two weeks when her pregnancy was confirmed PEP was increased to TEP. She miscarried in a few weeks. She conceived in May 2009 through IVF while continuing on aspirin. TEP with monthly anti-Xa monitoring was started prior to IVF when she started her ovarian stimulation medications. She currently has a live 16-week gestation.Our report corroborates the findings by Brenner and colleagues of a benefit of an increased enoxaparin dose after failure of a low dose. It is possible that the higher dose leads to better control of a placental thrombotic state. While the timing of initiation of thromboprophylaxis has been established for natural pregnancies (aspirin is started pre-conception; enoxaparin is started at pregnancy confirmation or at detection of the fetal heartbeat), optimal time for initiation of thromboprophylaxis in IVF pregnancies has not been determined. Ovarian stimulation for IVF leads to a hyperestrogenic state which increases thrombotic risk. It is possible that starting TEP at the time of initiation of ovarian stimulation in Patient 2 enabled her ongoing viable second-trimester pregnancy by optimizing placental conditions. Disclosures:Off Label Use: Aspirin and enoxaparin during pregnancy to prevent recurrent fetal loss.

Thromboprophylaxis and Peripheral Nerve Blocks in Patients Undergoing Joint Arthroplasty

This study was designed to assess the risk of hematoma related to the combination of peripheral nerve blocks and thromboprophylaxis. A total of 3588 patients undergoing joint arthroplasty were included. Blocks performed included continuous lumbar plexus, continuous femoral, and continuous or single sciatic. The perineural catheters were removed on postoperative days 2 or 3. A total of 6935 blocks were performed in patients receiving warfarin (50.0%), fondaparinux (12.8%), deltaparin (11.6%), enoxaparin (1.8%), and aspirin (23.8%). In this patient population, no perineural hematoma was recorded. Our data provide evidence that continuous/single peripheral nerve blocks can be safely performed before thromboprophylaxis initiation, and perineural catheters can be safely removed while the patient is receiving thromboprophylaxis and/or aspirin.

New versus Established Drugs in Venous Thromboprophylaxis

European surgeons generally administer thromboprophylaxis with low-molecular-weight heparins (LMWHs) at high doses 12 hours preoperatively in response to findings that surgery-related deep-vein thrombosis typically originates at the time of major orthopedic surgery or shortly afterwards. North American surgeons, in contrast, generally administer LMWHs at an almost 50% higher dose than that given in Europe 12-24 hours postoperatively, even though both pre- and postoperative administration are considered suitable in current guidelines. This review therefore examines how close to major orthopedic surgery thromboprophylaxis is administered, and the subsequent effect of timing on clinically relevant efficacy and safety parameters. The trials examined involve fondaparinux sodium (fondaparinux) and (xi)melagatran, in comparison with the established LMWHs enoxaparin sodium (enoxaparin) and dalteparin. In key trials, fondaparinux reduced the risk of asymptomatic and clinical venous thromboembolism (VTE) by 55% compared with enoxaparin, at the expense of a 1.6-fold higher risk of bleeding. While the studies were not designed to compare efficacy endpoints based on clinical outcomes, no significant difference was demonstrated for symptomatic VTE. The fact that the enoxaparin regimen was started at the upper limits of its recommended initiation timeframe may have significantly influenced the results of comparative studies, given that several meta-analyses found that the timing of LMWH initiation significantly influenced its effectiveness on asymptomatic VTE and major bleedings. Compared with once-daily LMWH in European trials, early postoperative doses/regimens of twice-daily (xi)melagatran did not increase severe bleeding and was significantly less effective at preventing asymptomatic total VTE in patients who had undergone total hip-replacement surgery. When used according to the 'knife-to-skin' protocol, the melagatran regimen was superior to enoxaparin in preventing major asymptomatic VTE, but at the cost of a higher rate of major bleeding. In North America, the delayed postoperative administration of (xi)melagatran (oral only) was less effective than the postoperative twice-daily enoxaparin regimen with regard to asymptomatic total and major VTE. Our analysis highlights the fact that differences in efficacy and safety data in clinical trials of thromboprophylaxis might also be linked to differences in the timing of initiation. However, it is not possible to assess the importance of this 'time effect' among other factors considered as drug-specific properties (pharmacokinetics, mode of action, dosage) and evaluate their respective contribution in the observed differences. To avoid unbiased comparison in further studies, the possible effect of timing should be taken into account and, when feasible, both therapies started at the same time. For instance, harmonizing the initiation of thromboprophylaxis 6-8 or 12 hours postoperatively could be two acceptable harmonized options for scheduling in clinical trials.

Orthopaedic Surgery as a Model for Drug Development in Thrombosis

Venous thromboembolism after total hip replacement or total knee replacement represents a significant complication of these surgical techniques, with profound clinical and economic consequences. As the detection of venous thromboembolism is particularly difficult in this setting, its prevention with thromboprophylactic agents is the most appropriate strategy. The anticoagulants currently used for thromboprophylaxis in orthopaedic surgery are injectable low-molecular-weight heparins (LMWHs) and oral coumarin derivatives such as warfarin. Orthopaedic surgery provides a good model with which to investigate the antithrombotic potential of novel agents, because of the relatively high venous thromboembolism event rates, and the opportunity to detect and quantify bleeding. This paper provides an overview of the clinical burden of venous thromboembolism in orthopaedic surgery and the benefits and limitations of current thromboprophylactic modalities. In addition, geographical differences in treatment regimens regarding the choice of agent, timing of initiation and duration of thromboprophylaxis, and how these influence the incidence of venous thromboembolism, will be discussed.

Venous thromboembolism prophylaxis in a South Australian teaching hospital.

Venous thromboembolism (VTE) is relatively common among hospitalized patients, is often clinically silent, and is associated with substantial morbidity and mortality. Risk stratification and routine use of thromboprophylaxis for patients at moderate to high risk for VTE are key strategies that can be used to prevent VTE. To assess the appropriateness of the selection and implementation of thromboprophylactic measures for prevention of VTE within a South Australian teaching hospital. Guidelines for risk stratification and prophylaxis were compiled from a range of studies, consensus statements, and tertiary references. Using prospective, observational methodology, data collection was performed through case note audit for 130 inpatient admissions over a 4-week period. The decisions regarding the usage of thromboprophylaxis were considered inappropriate in 32% of cases in the study cohort. Suboptimal practices were also observed with respect to factors including the choice between mechanical and pharmacologic methods and the timing of initiation and cessation of thromboprophylaxis. These findings provide evidence suggesting that the selection and implementation of thromboprophylaxis require improvement and that appropriate means to facilitate this improvement need to be developed and evaluated through future research.

Epidural analgesia for pain relief following hip or knee replacement.

Hip and knee replacement are common operative procedures to improve mobility and quality of life. Adequate pain relief is essential in the postoperative period to enable ambulation and initiation of physiotherapy. Lumbar epidural analgesia is a common modality for pain relief following these procedures. However, there is no systematic review of the evidence comparing the efficacy of epidural analgesia with other postoperative analgesic modalities. As the use of epidural analgesia may delay the initiation of anticoagulant thromboprophylaxis due to the potential risk of epidural hematoma, a synthesis of the evidence is necessary to determine whether or not alternative analgesic modalities are worse, equivalent, or better than epidural analgesia. Our objective is to answer the question: "Is lumbar epidural analgesia more efficacious than systemic analgesia or long-acting spinal analgesia for postoperative pain relief in patients after elective hip or knee replacement?" MEDLINE, EMBASE, CINAHL, LILACS, and the Cochrane Controlled Trials Register were searched from their inception to June 2001. Reference lists of review articles and included studies were also reviewed for additional citations. A study was included if it was a randomized or pseudo randomized controlled clinical trial of patients undergoing hip or knee replacement, in which postoperative lumbar epidural analgesia was compared to other methods for pain relief. Study selection was performed unblinded in duplicate. Data were collected unblinded in duplicate. Information on the patients, methods, interventions, outcomes (pain relief, postoperative function, length of stay) and adverse events were recorded. Methodological quality was assessed using a validated 5-point scale. Meta-analysis was conducted when sufficient data existed from two or more studies. Heterogeneity testing was performed using the Breslow-Day method. The fixed effects model was used unless heterogeneity was present, in which case, a random effects model was used. Continuous data were summarized as weighted mean differences (WMD) or standardized mean differences (SMD) with 95% confidence intervals (CI). Dichotomous data were summarized as odds ratios (OR) and numbers-needed-to-treat (NNT) or numbers-needed-to-harm (NNH) with their respective 95% CI. Graphical representation of continuous data used the MetaView program. In the first four to six hours after surgery, patients receiving epidural analgesia had less pain at rest, based on visual analog scores (VAS), than patients receiving systemic analgesia (SMD -0.77; 95% CI -1.24 to -0.31). This effect was not statistically significant by 18 to 24 hours (SMD -0.29; 95% CI -0.73 to 0.16). These observations were based only on studies evaluating populations consisting of total knee replacements alone or mixed populations of total hip or total knee replacements. For pain relief with movement after surgery, patients receiving epidural analgesia reported lower pain scores than patients receiving systemic analgesia in all four studies examining these outcomes. The choice of epidural agents may also influence the extent to which epidural analgesia differs from systemic analgesia. The differences between epidural analgesia and systemic analgesia in the frequency of nausea and vomiting (OR 0.95; 95% CI 0.60 to 1.49) or depression of breathing (OR 1.07; 95% CI 0.45 to 2.54) were not statistically significant. Sedation occurred less frequently with epidural analgesia (OR 0.30; 95% CI 0.09 to 0.97) with a number-needed-to-harm of 7.7 (95% CI 3.5 to 42.0) patients for the systemic analgesia group. Retention of urine (OR 3.50, 95% CI 1.63 to 7.51; NNH 4.5, 95% CI 2.3 to 12.2), itching (OR 4.74, 95% CI 1.76 to 12.78; NNH 6.8, 95% CI 4.4 to 15.8), and low blood pressure (OR 2.78, 95% CI 1.15 to 6.72; NNH 6.7, 95% CI 3.5 to 103) were more frequent with epidural analgesia compared to systemic analgesia. There were insufficient numbers to draw conclusions on the edural analgesia compared to systemic analgesia. There were insufficient numbers to draw conclusions on the effect of epidural analgesia on serious postoperative complications, functional outcomes, or length of hospital stay. Epidural analgesia may be useful for postoperative pain relief following major lower limb joint replacements. However, the benefits may be limited to the early (four to six hours) postoperative period. An epidural infusion of local anesthetic or local anesthetic-narcotic mixture may be better than epidural narcotic alone. The magnitude of pain relief must be weighed against the frequency of adverse events. The current evidence is insufficient to draw conclusions on the frequency of rare complications from epidural analgesia, postoperative morbidity or mortality, functional outcomes, or length of hospital stay.

Unresolved issues in the prevention and treatment of venous thromboembolism.

Venous thromboembolism (VTE) is a major health problem. Anticoagulation can significantly decrease the morbidity and mortality associated with VTE. Heparin and coumarin derivatives have been the standard of care for the last 50 years, and the development of low-molecular-weight heparin preparations has significantly improved the prevention and treatment of venous thromboembolic disease. With these advances, investigators are now able to address some of the unresolved issues in antithrombotic therapy, including the search for the optimal antithrombotic agent in high-risk patients, the optimal timing of thromboprophylaxis initiation in the surgical population, and the duration of prophylaxis for the prevention of initial and recurrent VTE events. Clinical trials have begun to investigate many of these issues, and the resulting data have already contributed to improving the management of patients with a high risk of VTE.

Low molecular weight heparin: biochemistry, pharmacology, perioperative prophylaxis regimens, and guidelines for regional anesthetic management.

Low molecular weight heparin: biochemistry, pharmacology, perioperative prophylaxis regimens, and guidelines for regional anesthetic management.

95/05196 The preparation of climatic data and its application to building and civil engineering

Prothrombin time-international normalized ratio (PT-INR) is widely utilized to guide plasma therapy and initiation of thromboprophylaxis after a hepatectomy. Thrombelastography (TEG) monitors shear elasticity, which is sensitive to cellular and plasma components in blood, allowing for functional assessment of the life of the clot. The objective of this study was to prospectively compare PT-INR and TEG in liver resection patients.Forty patients were enrolled before undergoing an elective hepatectomy. Patients underwent a liver resection utilizing a low central venous pressure (CVP) anaesthetic technique and intermittent Pringle manoeuver. PT-INR and TEG were drawn prior to incision, post-operatively, and post-operative days 1, 3 and 5.All post-operative PT-INR values increased significantly when compared with pre-operative PT-INR (P < 0.01). The time of onset to clot (R-value) decreased significantly at the post-operative time point (P = 0.04), consistent with a relative hypercoagulability. Subsequent R-values were not different compared with the pre-operative R-value. The strength of the clot (maximum amplitude, MA) was unchanged when comparing pre- and post-operative time points.In spite of an elevation in PT-INR, patients undergoing a liver resection demonstrated a brief hypercoagulable state, followed by normal coagulation function based on TEG. These data call into question the practice of utilizing PT-INR to guide plasma transfusion and timing of prophylactic anticoagulation after a liver resection.