Conventional versus restricted anti-Xa-guided heparin protocol in adult patients undergoing extracorporeal membrane oxygenation.

OBJECTIVE: The optimal intensity of anticoagulation for adult patients supported with extracorporeal membrane oxygenation (ECMO) remains uncertain. The objective of this study was to evaluate the effectiveness and safety of two anticoagulation protocols using conventional (0.3-0.7 IU/ml) versus restricted (0.2-0.5 IU/ml) anti-factor Xa (anti-Xa) targets for the management of unfractionated heparin (UFH) in adult ECMO patients. METHODS: This retrospective before-after cohort study compared two groups of ECMO patients who received UFH for at least 24-h from March 2016 to May 2019. The primary outcome was the composite rate of major bleeding or thrombotic events per ECMO day. Secondary outcomes included the mean amount of blood products transfused per ECMO day, the proportion of patients who were within the target anti-Xa at 24-h, the time to achieve target anti-Xa, and the number of heparin infusion adjustments to reach target anti-Xa. RESULTS: Forty-one patients were included in this analysis (conventional, n = 25; restricted, n = 16). There was no difference in the composite rate of major bleeding or thrombotic events per ECMO day (p = .090). The restricted group had lower rates of packed red blood cells (pRBC) transfusion per ECMO day (mean 1 ± 1 vs 3 ± 2 units, p = .003) and required fewer heparin infusion adjustments to reach the target (p = .007). There was no difference between the groups in the number of patients who achieved target anti-Xa at 24-h (p = .940). CONCLUSION: In adult ECMO patients, anticoagulation with a restricted anti-Xa target was associated with lower pRBC transfusions and did not provoke an excess of thrombotic events.

Enoxaparin titrated by anti-Xa levels reduces venous thromboembolism in trauma patients.

BACKGROUND: Trauma is a major risk factor for the development of a venous thromboembolism (VTE). After observing higher than expected VTE rates within our center's Trauma Quality Improvement Program data, we instituted a change in our VTE prophylaxis protocol, moving to enoxaparin dosing titrated by anti-Xa levels. We hypothesized that this intervention would lower our symptomatic VTE rates. METHODS: Adult trauma patients at a single institution meeting National Trauma Data Standard criteria from April 2015 to September 2019 were examined with regards to VTE chemoprophylaxis regimen and VTE incidence. Two groups of patients were identified based on VTE protocol-those who received enoxaparin 30 mg twice daily without routine anti-Xa levels ("pre") versus those who received enoxaparin 40 mg twice daily with dose titrated by serial anti-Xa levels ("post"). Univariate and multivariate analyses were performed to define statistically significant differences in VTE incidence between the two cohorts. RESULTS: There were 1698 patients within the "pre" group and 1406 patients within the "post" group. The two groups were essentially the same in terms of demographics and risk factors for bleeding or thrombosis. There was a statistically significant reduction in VTE rate (p = 0.01) and deep vein thrombosis rate (p = 0.01) but no significant reduction in pulmonary embolism rate (p = 0.21) after implementation of the anti-Xa titration protocol. Risk-adjusted Trauma Quality Improvement Program data showed an improvement in rate of symptomatic pulmonary embolism from fifth decile to first decile. CONCLUSION: A protocol titrating prophylactic enoxaparin dose based on anti-Xa levels reduced VTE rates. Implementation of this type of protocol requires diligence from the physician and pharmacist team. Further research will investigate the impact of protocol compliance and time to appropriate anti-Xa level on incidence of VTE. LEVEL OF EVIDENCE: Therapeutic/care management, Level IV.

COVID-19-related laboratory coagulation findings.

The alterations in the hemostatic balance in COVID-19 patients are strongly disturbed and contribute to a high prothrombotic status. The high rate of venous thromboembolism in COVID-19 patients goes along with derangements in coagulation laboratory parameters. Hemostasis testing has an important role in diagnosed COVID-19 patients. Elevated D-dimer levels were found to be a crucial laboratory marker in the risk assessment of thrombosis in COVID-19 patients. The diagnostic approach also includes prothrombin time and platelet count. Fibrinogen might give an indication for worsening coagulopathy. Other markers (activated partial thromboplastin time (aPTT), fibrinolysis parameters, coagulation factors, natural anticoagulants, antiphospholipid antibodies and parameters obtained by thromboelastography or thrombin generation assays) have been described as being deranged. These may help to understand the pathophysiology of thrombosis in COVID-19 patients but have currently no place in diagnosis or management in COVID-19 patients. For monitoring the heparin anticoagulant therapy, the anti-Xa assay is suggested, because the severe acute-phase reaction (high fibrinogen and high factor VIII) shortens the aPTT.

Filter clotting with continuous renal replacement therapy in COVID-19.

Coronavirus disease 2019 (COVID-19) appears to be associated with increased arterial and venous thromboembolic disease. These presumed abnormalities in hemostasis have been associated with filter clotting during continuous renal replacement therapy (CRRT). We aimed to characterize the burden of CRRT filter clotting in COVID-19 infection and to describe a CRRT anticoagulation protocol that used anti-factor Xa levels for systemic heparin dosing. Multi-center study of consecutive patients with COVID-19 receiving CRRT. Primary outcome was CRRT filter loss. Sixty-five patients were analyzed, including 17 using an anti-factor Xa protocol to guide systemic heparin dosing. Fifty-four out of 65 patients (83%) lost at least one filter. Median first filter survival time was 6.5 [2.5, 33.5] h. There was no difference in first or second filter loss between the anti-Xa protocol and standard of care anticoagulation groups, however fewer patients lost their third filter in the protocolized group (55% vs. 93%) resulting in a longer median third filter survival time (24 [15.1, 54.2] vs. 17.3 [9.5, 35.1] h, p = 0.04). The rate of CRRT filter loss is high in COVID-19 infection. An anticoagulation protocol using systemic unfractionated heparin, dosed by anti-factor Xa levels is reasonable approach to anticoagulation in this population.

Impact of implementation of an individualised thromboprophylaxis protocol in critically ill ICU patients with COVID-19: A longitudinal controlled before-after study.

INTRODUCTION: An individualised thromboprophylaxis was implemented in critically ill patients suffering from coronavirus disease 2019 (COVID-19) pneumonia to reduce mortality and improve clinical outcome. The aim of this study was to evaluate the effect of this intervention on clinical outcome. METHODS: In this mono-centric, controlled, before-after study, all consecutive adult patients with confirmed COVID-19 pneumonia admitted to ICU from March 13th to April 20th 2020 were included. A thromboprophylaxis protocol, including augmented LMWH dosing, individually tailored with anti-Xa measurements and twice-weekly ultrasonography screening for DVT, was implemented on March 31th 2020. Primary endpoint is one-month mortality. Secondary outcomes include two-week and three-week mortality, the incidence of VTE, acute kidney injury and continuous renal replacement therapy (CRRT). Multiple regression modelling was used to correct for differences between the two groups. RESULTS: 46 patients were included in the before group, 26 patients in the after group. One month mortality decreased from 39.13% to 3.85% (p < 0.001). After correction for confounding variables, one-month mortality was significantly higher in the before group (p = 0.02, OR 8.86 (1.46, 53.75)). The cumulative incidence of VTE and CRRT was respectively 41% and 30.4% in the before group and dropped to 15% (p = 0.03) and 3.8% (p = 0.01), respectively. After correction for confounding variables, risk of VTE (p = 0.03, 6.01 (1.13, 32.12)) and CRRT (p = 0.02, OR 19.21 (1.44, 255.86)) remained significantly higher in the before group. CONCLUSION: Mortality, cumulative risk of VTE and need for CRRT may be significantly reduced in COVID-19 patients by implementation of a more aggressive thromboprophylaxis protocol. Future research should focus on confirmation of these results in a randomized design and on uncovering the mechanisms underlying these observations. REGISTRATION NUMBER: NCT04394000.

Anti-Factor Xa Activity of Fixed-Dose Fondaparinux in Low-Body-Weight Patients With Acute Coronary Syndrome.

BACKGROUND: Fixed-dose 2.5 mg of fondaparinux subcutaneous injection once daily has been recommended in treatment of non-ST-segment elevation acute coronary syndrome (NSTE-ACS) irrespective of body weight (BW). However, data on anti-factor Xa (anti-FXa) activity of fondaparinux are scarce in low-BW patients. OBJECTIVE: We aimed to assess anti-FXa activity of fondaparinux in low-BW patients (BW < 50 kg) compared with normal-BW patients (BW ≥ 50 kg) who presented with NSTE-ACS. METHODS: This is a prospective cohort study of patients with NSTE-ACS receiving fondaparinux. Anti-FXa activity was measured 4 hours after 2.5 mg subcutaneous injection of fondaparinux after the first 2 doses. RESULTS: Among 87 enrolled patients, 18 (21%) had BW <50 kg. Patients in the low-BW group were older and had lower creatinine clearance. Median duration of fondaparinux therapy was 3 (IQR 2-4) days. Anti-FXa activity after the first dose of fondaparinux was similar between the low-BW and normal-BW groups (0.40 ± 0.15 vs 0.40 ± 0.17 mg/L, P = 0.914). However, anti-FXa activity after the second dose of fondaparinux was significantly higher in the low-BW group as compared with the normal-BW group (0.53 ± 0.10 vs 0.44 ± 0.16 mg/L, P = 0.011). Multivariate analysis showed that BW was the only independent factor that inversely correlated with anti-FXa activity. There was only 1 bleeding event during hospitalization in the normal-BW group and none in the low-BW group. CONCLUSION AND RELEVANCE: Anti-FXa activity of the second dose of fondaparinux was higher in low-BW patients but still within the expected range.

Circulating heparan sulfate chains and body weight contribute to anti-Xa levels in cancer patients using the prophylactic dose of enoxaparin.

Hospitalized cancer patients are at increased risk of thrombosis and prophylaxis with heparin is recommended. Heparanase is a protein capable of degrading heparan sulfate (HS) chains. The first objective of the study was to examine the effects of weight on anti-Xa levels in cancer patients treated with a fixed dose of enoxaparin as thromboprophylaxis. The second aim was to assess a potential correlation between plasma pre-treatment coagulation parameters and anti-Xa levels in an assumption that heparanase degradation activity towards heparins and HS chains could affect anti-Xa levels. Two blood samples (prior to and 3 h after drug injection) of 76 cancer patients with an indication for prophylaxis with enoxaparin (40 mg) were evaluated for coagulation markers. Sub-prophylactic levels of anti-Xa (< 0.2 U/ml) were found in 16/76 (21%) patients; in 13/76 (13%) patients the values were supra-prophylactic (> 0.5 U/ml). In the subgroup of patients weighing > 80 kg, 7/14 (50%) individuals had a sub-prophylactic level. Overall, anti-Xa levels appeared to correlate with patient's weight (r = - 0.48, p < 0.0001), pre-treatment partial thromboplastin time (PTT), D-dimer, HS, heparanase levels and procoagulant activity. We concluded that plasma anti-Xa levels correlated with patient's weight. A substantial portion of cancer patients receiving enoxaparin prophylaxis was undertreated. For patients > 80 kg, a weight-adjusted prophylactic dose of enoxaparin could be considered. Elevated enoxaparin anti-Xa levels correlated with pre-treatment parameters of coagulation system activation. High pre-treatment HS and elevated plasma anti-Xa levels may potentially serve as biomarkers for the identification of patients at increased thrombosis risk.

Pharmacokinetic Comparison of Subcutaneous and Intravenous Nadroparin Administration for Thromboprophylaxis in Critically Ill Patients on Vasopressors.

INTRODUCTION: Critically ill patients are exposed to a high risk of developing thromboembolism. Moreover, standard prophylaxis with subcutaneous (SC) heparin is less efficient in patients requiring vasopressors. The aim is a comparison of pharmacokinetics between SC and intravenous (IV) applied nadroparin. METHODS: Thirty-eight ventilated ICU patients requiring vasopressor support were randomized into a single dose of nadroparin 3,800 IU (0.4 mL) subcutaneously (SC group) or 1,900 IU (0.2 mL) intravenously (IV group). Anti-factor Xa activity (anti-Xa) was observed over 24 h; data are stated as median (IQR). RESULTS: Peak anti-Xa was significantly higher in the IV group 0.42 (0.39-0.43) IU/mL than in the SC group 0.16 (0.09-0.18) IU/mL (p < 0.001). There was a trend towards higher area under the curve (AUC) of anti-Xa in the SC group 1.41 (0.41-1.80) IU/mL × h than in the IV group 1.04 (0.93-1.13) IU/mL × h (p = 0.08). In the SC group, there was a negative correlation between anti-Xa AUC and both capillary refill time Xa (r = -0.86) and norepinephrine dose (r = -0.68). In the IV group, anti-Xa decrease half-life was 1.6 (1.4-2.0) h. CONCLUSIONS: IV administration of 1,900 IU of nadroparin led to a predictable effective peak anti-Xa. After SC administration, anti-Xa was heterogeneous and significantly influenced by peripheral perfusion.

Cirrhosis, Thrombosis, Finding FaXts about Doses: Dosing of Unfractionated Heparin for Venous Thromboembolism in Cirrhosis.

Background: Despite known disease-specific alterations to anti-factor Xa (AXA) levels, the physiological response of patients with cirrhosis to unfractionated heparin (UFH) infusions is not well established in clinical settings. Objective: The purpose of this study was to characterize the dosing and safety profile of UFH in patients with varying degrees of cirrhosis when treated for venous thromboembolism (VTE). Methods: This retrospective observational study was conducted at a single academic medical center in the United States. Patients with a diagnosis of cirrhosis who received UFH infusions for greater than 48 hours for treatment of VTE were included. Comparisons between heparin infusion rates, AXA levels, and safety outcomes based on severity of cirrhosis were made to define differences between those groups. Results: When compared by compensation status or by Child-Turcotte-Pugh (CTP) class, patients with more severe disease trended toward lower initial AXA levels on heparin initiation and higher heparin requirements to achieve therapeutic levels and were significantly less likely to achieve therapeutic levels than patients with less severe disease (P = 0.001 for compensation, P = 0.017 for CTP). Additionally, bleeding rates were higher in patients with more severe disease, without reaching statistical significance. Conclusion and Relevance: Patients with severe cirrhosis required higher doses of heparin to achieve the same therapeutic AXA levels, but also tended to have higher rates of bleeding compared with less severe cirrhosis. These results represent further evidence of changes in heparin response as cirrhosis severity increases and may suggest that current monitoring methods are suboptimal in this patient population.

Bodyweight-adjusted rivaroxaban for children with venous thromboembolism (EINSTEIN-Jr): results from three multicentre, single-arm, phase 2 studies.

BACKGROUND: Rivaroxaban has been shown to be efficacious for treatment of venous thromboembolism in adults, and has a reduced risk of bleeding compared with standard anticoagulants. We aimed to develop paediatric rivaroxaban regimens for the treatment of venous thromboembolism in children and adolescents. METHODS: In this phase 2 programme, we did three studies to evaluate rivaroxaban treatment in children younger than 6 months, aged 6 months to 5 years, and aged 6-17 years. Our studies used a multicentre, single-arm design at 54 sites in Australia, Europe, Israel, Japan, and north America. We included children with objectively confirmed venous thromboembolism previously treated with low-molecular weight heparin, fondaparinux, or a vitamin K antagonist for at least 2 months or, in children who had catheter-related venous thromboembolism for at least 6 weeks. We administered rivaroxaban orally in a bodyweight-adjusted 20 mg-equivalent dose, based on physiologically-based pharmacokinetic modelling predictions and EINSTEIN-Jr phase 1 data in young adults, in either a once-daily (tablets; for those aged 6-17 years), twice-daily (in suspension; for those aged 6 months to 11 years), or three times-daily (in suspension; for those younger than 6 months) dosing regimen for 30 days (or 7 days for those younger than 6 months). The primary aim was to define rivaroxaban treatment regimens that match the target adult exposure range. The principal safety outcome was major bleeding and clinically relevant non-major bleeding. Analyses were per-protocol. The predefined efficacy outcomes were symptomatic recurrent venous thromboembolism, asymptomatic deterioration on repeat imaging at the end of the study treatment period. These trials are registered at ClinicalTrials.gov, numbers NCT02564718, NCT02309411, and NCT02234843. FINDINGS: Between Feb 11, 2013, and Dec 20, 2017, we enrolled 93 children (ten children younger than 6 months; 15 children aged 6 months to 1 year; 25 children aged 2-5 years; 32 children aged 6-11 years; and 11 children aged 12-17 years) into our study. 89 (96%) children completed study treatment (30 days of treatment, or 7 days in those younger than 6 months), and 93 (100%) children received at least one dose of study treatment and were evaluable for the primary endpoints. None of the children had a major bleed, and four (4%, 95% CI 1·2-10·6) of these children had a clinically relevant non-major bleed (three children aged 12-17 years with menorrhagia and one child aged 6-11 years with gingival bleeding). We found no symptomatic recurrent venous thromboembolism in any patients (0%, 0·0-3·9). 24 (32%) of 75 patients with repeat imaging had their thrombotic burden resolved, 43 (57%) patients improved, and eight (11%) patients were unchanged. No patient deteriorated. We confirmed therapeutic rivaroxaban exposures with once-daily dosing in children with bodyweights of at least 30 kg and with twice-daily dosing in children with bodyweights of at least 20 kg and less than 30 kg. Children with low bodyweights (<20 kg, particularly <12 kg) showed low exposures so, for future studies, rivaroxaban dosages were revised for these weight categories, to match the target adult exposure range. 61 (66%) of 93 children had adverse events during the study. Pyrexia was the most common adverse event (ten [11%] events), and anaemia and neutropenia or febrile neutropenia were the most frequent grade 3 or worse events (four [4%] events each). No children died or were discontinued from rivaroxaban because of adverse events. INTERPRETATION: Treatment with bodyweight-adjusted rivaroxaban appears to be safe in children. The treatment regimens that we confirmed in children with bodyweights of at least 20 kg and the revised treatment regimens that we predicted in those with bodyweights less than 20 kg will be evaluated in the EINSTEIN-Jr phase 3 trial in children with acute venous thromboembolism. FUNDING: Bayer AG, Janssen Research and Development.

Safety and Efficacy of Tinzaparin Anticoagulation during Nocturnal Hemodialysis.

BACKGROUND: The safety and efficacy of low-molecular-weight heparin in the prevention of extracorporeal dialysis circuit clotting among in-center extended duration nocturnal hemodialysis (INHD) patients are unknown. The aim of this study was to determine the safety and efficacy of 2 doses of tinzaparin, among INHD patients receiving 6-8 h hemodialysis, 3 times per week. METHODS: We conducted a retrospective cohort study to examine antifactor Xa levels at time 0, 2 h, 4 h mid-hemodialysis (mid-HD), 6 h, and at end of each INHD session for 4 weeks and to determine extracorporeal dialysis circuit clotting and bleeding events after switching from unfractionated heparin to tinzaparin, using a standard protocol of tinzaparin delivery at the initiation and midpoint of HD. RESULTS: All 16 patients in The Ottawa Hospital INHD program were converted to tinzaparin and followed for 177 INHD sessions. Mean antifactor Xa level at 2 h of HD was 0.41 ± 0.21 (SD) IU/mL, at 4 h (mid-HD) 0.19 ± 0.17 IU/mL, at 6 h 0.44 ± 0.21 IU/mL, and at dialysis end 0.26 ± 0.14 IU/mL. Antifactor Xa levels were undetectable at the start of INHD, suggesting no tinzaparin accumulation. Five patients required an increase in tinzaparin due to extracorporeal dialysis circuit clotting. There were no bleeding events. One patient required a switch to fondaparinux due to an adverse reaction. CONCLUSION: Tinzaparin was safe and efficacious for most INHD patients without accumulation or bleeding. The conversion from unfractionated heparin to tinzaparin required an increased tinzaparin dose for 31% of INHD patients.

Evaluation of prophylactic dosages of Enoxaparin in non-surgical elderly patients with renal impairment.

BACKGROUND: Thromboprophylaxis dosing strategies using enoxaparin in elderly patients with renal disease are limited, while dose adjustments or monitoring of anti-Xa levels are recommended. We sought to evaluate the efficacy and safety of enoxaparin 20 mg versus 30 mg subcutaneously daily by comparing anti-Xa levels, thrombosis and bleeding. METHODS: We conducted a prospective, single-blinded, single-center randomized clinical trial including non-surgical patients, 70 years of age or older, with renal disease requiring thromboprophylaxis. Patients were randomized to receive either 20 mg or 30 mg of enoxaparin. The primary endpoint was peak anti-Xa levels on day 3. Secondary endpoints included trough anti-Xa levels on day 3, achievement of within range prophylactic target peak anti-Xa levels and the occurrence of hemorrhage, thrombosis, thrombocytopenia or hyperkalemia during hospitalization. RESULTS: Thirty-two patients were recruited and sixteen patients were randomized to each arm. Mean peak anti-Xa level was significantly higher in 30 mg arm (n = 13) compared to the 20 mg arm (n = 11) 0.26 ± 0.11, 95%CI (0.18-0.34), versus 0.14 ± 0.09, 95CI (0.08-0.19) UI/ml, respectively; p = 0.004. Mean trough anti-Xa level was higher in 30 mg arm (n = 10) compared to the 20 mg arm (n = 16), 0.06 ± 0.03, 95CI (0.04-0.08) versus 0.03 ± 0.03, 95CI (0.01-0.05) UI/ml, respectively; p = 0.044. Bleeding events reported in the 30 mg arm were one retroperitoneal bleed requiring multiple transfusions, and in the 20 mg arm one hematuria. No thrombotic events were reported. CONCLUSION: Peak anti-Xa levels provided by enoxaparin 20 mg were lower than the desired range for thromboprophylaxis in comparison to enoxaparin 30 mg. TRIAL REGISTRATION: The trial was retrospectively registered on ClinicalTrials.gov identifier: NCT03158792 . Registered: May 18, 2017.

Utilizing Plasma Composition Data to Help Determine Procoagulant Dynamics in Patients with Thermal Injury: A Computational Assessment.

INTRODUCTION: The development of methods that generate individualized assessments of the procoagulant potential of burn patients could improve their treatment. Beyond its role as an essential intermediate in the formation of thrombin, factor (F)Xa has systemic effects as an agonist to inflammatory processes. In this study, we use a computational model to study the FXa dynamics underlying tissue factor-initiated thrombin generation in a small cohort of burn patients. MATERIALS AND METHODS: Plasma samples were collected upon admission (Hour 0) from nine subjects (five non-survivors) with major burn injuries and then at 48 hours. Coagulation factor concentrations (II, V, VII, VIII, IX, X, TFPI, antithrombin (AT), protein C (PC)) were measured and used in a computational model to generate time course profiles for thrombin (IIa), FXa, extrinsic tenase, intrinsic tenase and prothrombinase complexes upon a 5 pM tissue factor stimulus in the presence of 1 nM thrombomodulin. Parameters were extracted from the thrombin and FXa profiles (including max rate (MaxRIIa and MaxRFXa) and peak level (MaxLIIa and MaxLFXa)). Procoagulant potential was also evaluated by determining the concentration of the complexes at select times. Parameter values were compared between survivors and non-survivors in the burn cohort and between the burn cohort and a simulation based on the mean physiological (100%) concentration for all factor levels. RESULTS: Burn patients differed at Hour 0 (p < 0.05) from 100% mean physiological levels for all coagulation factor levels except FV and FVII. The concentration of FX, FII, TFPI, AT and PC was lower; FIX and FVIII were increased. The composition differences resulted in all nine burn patients at Hour 0 displaying a procoagulant phenotype relative to 100% mean physiological simulation (MaxLIIa (306 ± 90 nM vs. 52 nM), MaxRIIa (2.9 ± 1.1 nM/s vs. 0.3 nM/s), respectively p < 0.001); MaxRFXa and MaxLFXa were also an order of magnitude greater than 100% mean physiological simulation (p < 0.001). When grouped by survival status and compared at the time of admission, non-survivors had lower PC levels (56 ± 18% vs. 82 ± 9%, p < 0.05), and faster MaxRFXa (29 ± 6 pM/s vs. 18 ± 6 pM/s, p < 0.05) than those that survived; similar trends were observed for all other procoagulant parameters. At 48 hours when comparing non-survivors to survivors, TFPI levels were higher (108 ± 18% vs. 59 ± 18%, p < 0.05), and MaxRIIa (1.5 ± 1.4 nM/s vs. 3.6 ± 0.7 nM/s, p < 0.05) and MaxRFXa (13 ± 12 pM/s vs. 35 ± 4 pM/s, p < 0.05) were lower; similar trends were observed with all other procoagulant parameters. Overall, between admission and 48 hours, procoagulant potential, as represented by MaxR and MaxL parameters for thrombin and FXa, in non-survivors decreased while in survivors they increased (p < 0.05). In patients that survived, there was a positive correlation between FX levels and MaxLFXa (r = 0.96) and reversed in mortality (r= -0.91). CONCLUSIONS: Thrombin and FXa generation are increased in burn patients at admission compared to mean physiological simulations. Over the first 48 hours, burn survivors became more procoagulant while non-survivors became less procoagulant. Differences between survivors and non-survivors appear to be present in the underlying dynamics that contribute to FXa dynamics. Understanding how the individual specific balance of procoagulant and anticoagulant proteins contributes to thrombin and FXa generation could ultimately guide therapy and potentially reduce burn injury-related morbidity and mortality.

Placental Pathological Findings following Adjusting Enoxaparin Dosage in Thrombophilic Women: Secondary Analysis of a Randomized Controlled Trial.

OBJECTIVE: Randomized trials showed no improvement in pregnancy outcomes with the use of low molecular weight heparin (LMWH) to prevent placenta-mediated pregnancy complications (PMPCs) among thrombophilic women. However, the effect of treatment on placental findings was not examined. We aimed to examine the occurrence of placental vascular lesions in thrombophilic women treated with LMWH dose adjusted according to anti-factor Xa compared with a fixed dose. STUDY DESIGN: This study was a secondary analysis of a randomized trial designed to examine whether LMWH dose adjusted according to anti-factor Xa levels compared with a fixed dose would reduce the risk of PMPC. Eligible women were randomly allocated in a 1:1 ratio to either a fixed dose of 40 mg daily LMWH (fixed dose group) or adjusted dose according to anti-factor Xa levels (adjusted dose group). Placentas were examined by the same perinatal pathologist who was blinded to group allocation. The primary outcome for this analysis was the incidence of maternal placental vascular lesions. RESULTS: During the study period, 88 placentas were examined; 41 and 47 from the fixed and adjusted dose groups, respectively. Demographics, obstetrics and types of thrombophilias were similar between the groups. Maternal placental vascular lesions were observed in 23 (56.1%) and 21 (44.68%) placentas (p = 0.28) and foetal placental vascular lesions in 2 (4.88%) and 1 (2.13%) placentas (p = 0.59) in the fixed and adjusted groups, respectively. CONCLUSION: Adjusted dose of enoxaparin according to anti-factor Xa levels compared with a fixed dose did not affect placental vascular lesions in thrombophilic women.

Biomarkers of Thrombosis in ST-Segment Elevation Myocardial Infarction: A Substudy of the ATOLL Trial Comparing Enoxaparin Versus Unfractionated Heparin.

BACKGROUND: The aim was to compare the peri-procedural biomarkers of coagulation and platelet activation in patients randomly allocated to intravenous enoxaparin or unfractionated heparin (UFH) in the ATOLL randomized trial (NCT00718471). METHODS AND RESULTS: A total of 129 patients (n = 58 enoxaparin and n = 71 UFH) admitted for ST-segment elevation myocardial infarction (STEMI) treated by percutaneous coronary intervention (PCI) were included in this substudy of the ATOLL trial. Activated partial thromboplastin time ratio, anti-Xa activity, von Willebrand factor antigen, prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin complex (TAT), tissue factor pathway inhibitor and soluble CD40 ligand were measured at sheath insertion (T1) and at the end of the PCI (T2) and correlated with 1-month clinical outcomes. Target anticoagulation levels at T2 were more readily achieved in patients receiving enoxaparin compared to those receiving UFH (80.3 vs 18.2%, p < 0.0001). Increased levels of F1 + 2 and TAT measured at T2 were associated with the incidence of the composite ischemic endpoint (p = 0.04 and p = 0.03) and all-cause mortality (p < 0.0001 and p = 0.002). Release of F1 + 2 between T1 and T2 also predicted the composite ischemic endpoint (312 ± 513 vs 37 ± 292, p = 0.04) and net clinical outcome (185 ± 405 vs 3.2 ± 278, p = 0.03). CONCLUSIONS: During primary PCI, enoxaparin achieved therapeutic levels more frequently than UFH. Higher level of thrombin generation measured at the end of the PCI procedure was associated with more frequent ischemic events.

Increased Enoxaparin Dosing Requirements for Treatment of Deep Vein Thrombosis in a Severely Burned Patient: Case Report and Literature Review.

Dosing of enoxaparin for deep vein thrombosis (DVT) prophylaxis in acutely burned patients has been shown to result in anti-Xa levels below target range. We describe the first case report, to our knowledge, of a severely burned patient who, despite prophylactic dosing of enoxaparin 30 mg subcutaneously twice daily, developed an acute DVT that required high-dose enoxaparin (100 mg [1.5 mg/kg] subcutaneously every 8 hours) to maintain anti-Xa levels within the therapeutic range (0.6-1 IU/ml). Pharmacokinetic evaluations were performed using anti-Xa levels measured throughout the patient's hospital stay to validate the appropriateness of this high-dose regimen based on established therapeutic anti-Xa level ranges. These results suggest that routine anti-Xa level monitoring, regardless of enoxaparin dosing, is necessary for burn patients who are receiving enoxaparin given their hypermetabolic state following injury.