批發(fā)和零售貿(mào)易零售業(yè)-閱讀頁
2025-01-12 05:39本頁面
【正文】 ? Vascular disease (eg., scurvy) can prolong BT (humans, guinea pigs) Considerations for Blood Collection Clean/smooth surfaces ? Want to avoid platelet clumping or activation of factor XII ? Use plastic or siliconized glass for sample collection ? Animal blood clots faster than human blood prime needle with anticoagulant Collect sample from an endotheliallined vessel and careful venipuncture ? Want avoid contamination with tissue juice (factor III) ? Small clot activates coagulation system invalidating results ? Samples from indwelling catheters are usually unacceptable Sample Handling/Anticoagulants Plasma samples separated from cells within 30 minutes ? Perform analyses immediately ? Plasma samples may be quickly frozen (dry ice/alcohol or liquid nitrogen) and stored at 70o for analysis at a later date ? Activity of factors V and VIII is lost rapidly in samples held at room temperature Citrate (trisodium salt) is the anticoagulant of choice. ? Oxalate anticoagulants are acceptable not monly used ? Heparin unacceptable ? EDTA unacceptable (except for indirect evaluation of fibrinogen concentration by heat precipitation and refractometry) Evaluation cont. Activated Coagulation Time (ACT) in vivo test ? Measures (seconds) time to clot formation in fresh whole blood ? Careful attention to sample collection/handling ? Platelet counts 10,000 cause slight increase in ACT ? Results from lack of platelet phospholipid for test ? Increased ACT suggests factor deficiency in intrinsic or mon pathways ? Deficiency must be 5% of normal to prolong ACT Activated Partial Thromboplastin Time (APTT) ? Measures (seconds) time to clot formation in citrated plasma ? Increased APTT factor deficiency in intrinsic or mon pathways ? Deficiency must be 30% of normal to prolong APTT ? Fibrinogen 50 mg/dL will prolong APTT。 human origin reagent gives longer PT times ? Increased PT factor deficiency in factor VII or mon pathway ? Deficiency must be 30% of normal to prolong PT ? Fibrinogen 50 mg/dL will prolong PT ? Sensitivity increased with salinediluted plasma Russel’s Viper Venom Time (RVVT) ? Measures (seconds) time to clot formation in citrated plasma ? Increased RVVT in or mon pathway but insensitive to factor VII deficiency ? Deficiency must be 30% of normal to prolong RVVT ? Fibrinogen 50 mg/dL will prolong RVVT ? Sensitivity increased with salinediluted plasma Evaluation cont. Thrombin Clotting Time (TCT) ? Measures (seconds) time to clot formation in citrated plasma ? Increased TCT decreased fibrinogen concentration (100 mg/dL), dysfibrinogenemia, increased FDP concentration, heparin therapy Fibrinogen Concentration (factor I) ? In most species, fibrinogen is 100 400 mg/dL ? Fibrinogen decreases in DIC, severe liver insufficiency and hereditary hypofibrinogenemia ? Inflammation can increase fibrinogen concentration Evaluation cont. FibrinFibrinogen Degradation Products (FDP) ? Measures, by latex agglutination, the concentration of products of fibrinolys
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