anti-Xa Activity (anti-xa + activity)

Distribution by Scientific Domains


Selected Abstracts


ANTICOAGULANT EFFECTS OF LOW MOLECULAR WEIGHT HEPARIN IN HEALTHY CATS

JOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue S1 2004
AJ Alwood
Objectives: 1) Validate a chromogenic assay to measure Factor Xa inhibitory activity (anti-Xa activity) in normal feline plasma and following administration of low molecular weight heparins and unfractionated heparin. 2) Compare the effects of two commercially available low molecular weight heparins (LMWH), unfractionated heparin (UFH), and placebo on TEG, anti-Xa activity, PT/aPTT, PCV/TS and platelet count in healthy cats. Methods: Our study consisted of two phases: 1) the evaluation of a commercially available chromogenic anti-Xa assay (Rotachrom Heparin, Diagnostic Stago) for use in cats, and 2) the evaluation of hemostatic effects of LMWH in healthy cats. Phase 1: The anti-Xa assay was validated for use in cats using feline plasma and serial dilutions of the plasma spiked with UFH, enoxaparin, and dalteparin. Phase 2: Five healthy cats were included in a randomized Latin Squares model crossover-design to compare the effects of UFH and LMWH in cats. The cats then received one of the following subcutaneously: 1) 250 IU/kg UFH QID, 2) 100 IU/kg dalteparin BID, 3) 1 mg/kg enoxaparin BID, 4) 0.25 mL/kg 0.9% saline (placebo) QID. A minimum of a two-week washout period separated each treatment period. Each drug was administered for 5 days. Blood samples were obtained to measure anti-Xa, TEG, PT/aPTT, platelet count, and PCV/TS on Days 1, 3, 5, and 6 of each treatment cycle. Samples were collected at time 0 on each sample day for all parameters and on select days at hours 4, 8, and 12 for anti-Xa and TEG. Results: Preliminary results using the validated anti-Xa assay (from the first part of this study) demonstrate that LMWH treatment results in peak anti-Xa activity at the 4-hour sampling time that returned toward baseline by 8 hours (in 5/6 cats treated with LMWH thus far). Similar anticoagulant effects were noted in the TEG parameters of cats receiving LMWH (i.e., peak effects were noted at 4 hours). Analysis of current data by linear regression identifies a relationship between anti-Xa measurements and TEG parameters for cats treated with all heparin therapies (p<0.001). A similar relationship exists between anti-Xa and aPTT. Conclusions: Preliminary results suggest an anticoagulant effect of LMWH in cats that may not be uniform across individuals. Anti-Xa activity or TEG may provide useful tools for monitoring LMWH. [source]


Low molecular weight heparin (dalteparin) for the treatment of venous thromboembolism in pregnancy

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 2 2003
Anne Flem Jacobsen
Objective To evaluate the effect and dose of dalteparin given to pregnant women with acute venous thromboembolism. Design An observational study of pregnant women in Norway. Setting Delivery and haematological departments in Norway. Population Twenty women, aged 22,41 years, with acute venous thromboembolism verified by objective means. Methods Patients were treated with dalteparin from diagnosis until delivery. Treatment was monitored with anti-activated factor Xa (anti-Xa) activity, and the dose was adjusted to achieve target 0.5,1.0 U/mL 2,3 hours post-injection. Main outcome measure Anti-Xa activity and side effects. Result None of the patients suffered recurrent venous thromboembolism or major bleeding complications. In 9 of 13 women starting with conventional dose of dalteparin (100 iu/kg bd), dose escalation was necessary to reach target anti-Xa activity. None of the six women who started with 105,118 iu/kg bd required dose escalation. One woman who started with 133 iu/kg bd required dose reduction. Bioaccumulation of dalteparin was not observed. Conclusion Our study suggests that dalteparin may be used for the treatment of acute venous thromboembolism in pregnancy. Approximately 10,20% higher doses of dalteparin may be needed as compared with non-pregnant individuals. [source]


ANTICOAGULANT EFFECTS OF LOW MOLECULAR WEIGHT HEPARIN IN HEALTHY CATS

JOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue S1 2004
AJ Alwood
Objectives: 1) Validate a chromogenic assay to measure Factor Xa inhibitory activity (anti-Xa activity) in normal feline plasma and following administration of low molecular weight heparins and unfractionated heparin. 2) Compare the effects of two commercially available low molecular weight heparins (LMWH), unfractionated heparin (UFH), and placebo on TEG, anti-Xa activity, PT/aPTT, PCV/TS and platelet count in healthy cats. Methods: Our study consisted of two phases: 1) the evaluation of a commercially available chromogenic anti-Xa assay (Rotachrom Heparin, Diagnostic Stago) for use in cats, and 2) the evaluation of hemostatic effects of LMWH in healthy cats. Phase 1: The anti-Xa assay was validated for use in cats using feline plasma and serial dilutions of the plasma spiked with UFH, enoxaparin, and dalteparin. Phase 2: Five healthy cats were included in a randomized Latin Squares model crossover-design to compare the effects of UFH and LMWH in cats. The cats then received one of the following subcutaneously: 1) 250 IU/kg UFH QID, 2) 100 IU/kg dalteparin BID, 3) 1 mg/kg enoxaparin BID, 4) 0.25 mL/kg 0.9% saline (placebo) QID. A minimum of a two-week washout period separated each treatment period. Each drug was administered for 5 days. Blood samples were obtained to measure anti-Xa, TEG, PT/aPTT, platelet count, and PCV/TS on Days 1, 3, 5, and 6 of each treatment cycle. Samples were collected at time 0 on each sample day for all parameters and on select days at hours 4, 8, and 12 for anti-Xa and TEG. Results: Preliminary results using the validated anti-Xa assay (from the first part of this study) demonstrate that LMWH treatment results in peak anti-Xa activity at the 4-hour sampling time that returned toward baseline by 8 hours (in 5/6 cats treated with LMWH thus far). Similar anticoagulant effects were noted in the TEG parameters of cats receiving LMWH (i.e., peak effects were noted at 4 hours). Analysis of current data by linear regression identifies a relationship between anti-Xa measurements and TEG parameters for cats treated with all heparin therapies (p<0.001). A similar relationship exists between anti-Xa and aPTT. Conclusions: Preliminary results suggest an anticoagulant effect of LMWH in cats that may not be uniform across individuals. Anti-Xa activity or TEG may provide useful tools for monitoring LMWH. [source]


Treatment of Immune-Mediated Hemolytic Anemia with Individually Adjusted Heparin Dosing in Dogs

JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 3 2010
S.E. Helmond
Background: A major cause of death in dogs with immune-mediated hemolytic anemia (IMHA) is thromboembolism. Previous studies suggest unfractionated heparin (UH) is not effective in preventing thromboembolism in IMHA; however, subtherapeutic dosing could explain the seeming lack of efficacy. Hypothesis: Providing therapeutic plasma concentration of UH by individually adjusting doses based on antifactor Xa activity would improve survival in IMHA. Animals: Fifteen dogs with primary IMHA. Methods: Randomized, prospective, controlled clinical trial. Dogs received standardized therapy for IMHA and either constant dose (CD) (150 U/kg SC) (n = 7) or individually adjusted dose (IAD) (n = 8) UH, monitored via an anti-Xa chromogenic assay, adjusted according to a nomogram. UH was administered every 6 hours until day 7, and every 8 hours thereafter. UH dose was adjusted daily in IAD dogs until day 7, weekly until day 28, then tapered over 1 week. Dogs were monitored for 180 days. Results: At day 180, 7 dogs in the IAD group and 1 in the CD group were alive (P= .01). Median survival time for the IAD group was >180 days, and 68 days for the CD group. Thromboembolic events occurred in 5 dogs in the CD group and 2 dogs in the IAD group. Doses of UH between 150 and 566 U/kg achieved therapeutic anti-Xa activity (0.35,0.7 U/mL). Conclusions and Clinical Importance: This study suggests that IAD UH therapy using anti-Xa monitoring reduced case fatality rate in dogs with IMHA when compared with dogs receiving fixed low dose UH therapy. [source]


Antithrombotic Effect of Enoxaparin in Clinically Healthy Cats: A Venous Stasis Model

JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010
C.M. Van De Wiele
Background: Systemic arterial thromboembolic events are a serious complication of cardiac disease in cats. Objectives: To determine if enoxaparin induces an antithrombotic effect in cats at a dosage of 1 mg/kg SC q12h and if this antithrombotic effect is predicted by anti-Xa activity. Animals: Fourteen clinically healthy cats were divided into 3 groups: control (4 cats), treated and assessed at 4 hours (5 cats), and treated and assessed at 12 hours (5 cats). Methods: A venous stasis model was used and the extent of thrombus formation estimated by measuring thrombus weight and accretion of 125I-fibrinogen. Plasma anti-Xa activity was measured in treated cats. Results: There was a significant reduction in thrombus formation in the 4 h group compared with control (median weight, 0.000 versus 0.565 mg/mm, P < .01; median %125I-fibrinogen accretion, 0.0 versus 42.0%, P < .01). There was a reduction in thrombus formation in the 12 h group (median weight, 0.006 mg/mm, P= .09; median %125I-fibrinogen accretion, 3.83%, P= .09) but this reduction was not significant. The median percent thrombus inhibition for treated cats was 100.0% at 4 hours and 91.4% at 12 hours. Plasma anti-Xa activity was not significantly correlated with thrombus formation. Conclusions and Clinical Importance: This pilot study demonstrates that enoxaparin, when administered at a dosage of 1 mg/kg SC q12h, produces an antithrombotic effect in a venous statsis model in clinically healthy cats. Furthermore, this study demonstrates that anti-Xa activity is a poor predictor of enoxaparin's antithrombotic effect. [source]


Low molecular weight heparin (dalteparin) for the treatment of venous thromboembolism in pregnancy

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 2 2003
Anne Flem Jacobsen
Objective To evaluate the effect and dose of dalteparin given to pregnant women with acute venous thromboembolism. Design An observational study of pregnant women in Norway. Setting Delivery and haematological departments in Norway. Population Twenty women, aged 22,41 years, with acute venous thromboembolism verified by objective means. Methods Patients were treated with dalteparin from diagnosis until delivery. Treatment was monitored with anti-activated factor Xa (anti-Xa) activity, and the dose was adjusted to achieve target 0.5,1.0 U/mL 2,3 hours post-injection. Main outcome measure Anti-Xa activity and side effects. Result None of the patients suffered recurrent venous thromboembolism or major bleeding complications. In 9 of 13 women starting with conventional dose of dalteparin (100 iu/kg bd), dose escalation was necessary to reach target anti-Xa activity. None of the six women who started with 105,118 iu/kg bd required dose escalation. One woman who started with 133 iu/kg bd required dose reduction. Bioaccumulation of dalteparin was not observed. Conclusion Our study suggests that dalteparin may be used for the treatment of acute venous thromboembolism in pregnancy. Approximately 10,20% higher doses of dalteparin may be needed as compared with non-pregnant individuals. [source]