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Vett 117 wk 10
Clin Path I Hemostasis
| Question | Answer |
|---|---|
| Hemostasis | Glossary def: in text: the ability of the body's systems to maintain the integrity of the blood and blood vessels, involving a number of complex pathways, platelets, and coagulation factors. |
| D-dimers | Glossary def: A protein fragment that is formed from the breakdown of fibrin |
| Fibrin degradation products | Glossary def: Protein fragments formed from the breakdown of fibrin. In text: |
| Microparticles | Microparticles are membrane-bound cytoplasmic fragments that are released from platelets, leukocytes, and endothelial cells that serve to increase the surface area on which coagulation complexes can form |
| Phosphatidylserine | When platelets are activated, phosphatidylserine (PS) is exposed on the outer surface of the membrane. PS acts as a binding site for the complexes of the coagulation cascade, which activate Factor X and prothrombin (Factor II), respectively |
| Thrombin | Glossary def: An enzyme that is formed from prothrombin, calcium, and thromboplastin in plasma during the clotting process. Thrombin causes fibrinogen to change to fibrin, which is essential during the formation of a clot |
| von Willebrand factor | Glossary: vW Disease is an inherited disorder characterized by abnormally slow coagulation of blood & spontaneous epistaxis and gingival bleeding. Caused by a deficiency of a component of factor VIII. Excessive bleeding is common after injury or sx |
| What is the molecule that platelets express on their surface when they are activated? | phosphatidylserine (PS) |
| What molecule binds to tissue factor in the plasma to initiate the coagulation reactions? | Factor VIII - Tissue factor binds to Factor VIII in the plasma to initiate the coagulation reactions, and Factors I through XI serve to amplify the cascade |
| What functions to stabilize the platelet plug? | von Willebrand factor - The adhesion of platelets to each other and to the endothelium also requires von Willebrand factor, which serves to stabilize the platelet plug |
| What factor is activated as a result of the formation of coagulation complexes? | Factor X and prothrombin (Factor II), respectively |
| What substance is involved in the breakdown of the clot? | tissue plasminogen activator (tPA) and plasmin |
| mechanical phase | initiated when a blood vessel is ruptured or torn |
| platelets are attracted to this surface | the exposed blood vessel subendothelium is a charged surface |
| As platelets congregate at the site they do what | Platelets adhere to each other as well as to the blood vessel endothelium |
| chemical phase | referred to as the coagulation cascade, and it involves a number of coagulation factors. |
| what triggers the chemical phase of hemostasis | adhesion and aggregation of platelets also cause the platelets to release the initiating factor for the chemical phase of hemostasis |
| blood vessel endothelium | a thin layer of cells that lines the inner surface of all blood vessels, including arteries, veins, and capillaries. Regulates blood clotting by releasing factors that promote or inhibit platelet aggregation and fibrin formation. |
| chemical phase pathways | Intrinsic and extrinsic pathways - Regulates blood clotting by releasing factors that promote or inhibit platelet aggregation and fibrin formation. |
| end result of the coagulation cascade is | the formation of a mesh of fibrin strands that forms the clot |
| final phase of hemostasis | the degradation of the fibrin clot |
| Factor I | Fibrinogen |
| Factor II | Prothrombin |
| Factor III | Tissue factor |
| Factor IV | Calcium |
| Factor V | Proaccelerin |
| Factor VI | (There is no Factor VI.) |
| Factor VII | Proconvertin |
| Factor VIII | Antihemophilic factor |
| Factor IX | Christmas factor, plasma thromboplastin |
| Factor X | Stuart factor |
| Factor XI | Plasma thromboplastin antecedent |
| Factor XII | Hageman factor |
| Factor XIII | Fibrin-stabilizing factor, prekallikrein |
| Key Points/Synopsis | Intentionally Blank |
| Hemostasis requires platelets, a number of coagulation factors, and complex reaction pathways. (No flip side) | Intentionally Blank |
| Hemostasis proceeds through mechanical and chemical pathways. (No flip side) | Intentionally Blank |
| The term mechanical hemostasis refers to the aggregation and adhesion of platelets to exposed blood vessel endothelium. (No flip side) | Intentionally Blank |
| The mechanical and chemical phases of hemostasis are interrelated and interdependent. (No flip side) | Intentionally Blank |
| Activated platelets expose phosphatidylserine on their surface and release microparticles that also contain phosphatidylserine. (No flip side) | Intentionally Blank |
| Coagulation complexes attach to phosphatidylserine on the surfaces of microparticles and platelets. (No flip side) | Intentionally Blank |
| Thrombin serves to enhance the recruitment and activation of platelets. (No flip side) | Intentionally Blank |
| Fibrinogen is converted first to a soluble form and then to an insoluble form. (No flip side) | Intentionally Blank |
| The breakdown of fibrin requires plasmin and tPA. (No flip side) | Intentionally Blank |
| Fibrin is broken down into soluble FDPs, insoluble FDPs, and D-dimers. (No flip side) | Intentionally Blank |
| End of Synopsis (No flip side) | Intentionally Blank |
| What anticoagulant is preferred for platelet testing? | EDTA - Ethylenediaminetetraacetic acid (EDTA) is the preferred anticoagulant for platelet counts |
| What is the preferred anticoagulant for most plasma assays of coagulation? | Sodium Citrate - The preferred anticoagulant for most coagulation tests is sodium citrate |
| What is the proper ratio of blood to citrate anticoagulant, used for coagulation testing? | 1:9 - The proper ratio of citrate to blood is 1 part citrate to 9 parts whole blood |
| What type of technology is used in the Coag Dx™ analyzer to evaluate coagulation? | An analyzer that uses cartridges that contain the required reagents for a variety of coagulation tests. Light-emitting diode optical detectors are used to evaluate the rate of blood flow, which will decrease when a clot forms |
| What type of technology is used in the PFA-100 analyzer to evaluate coagulation? | Uses a cartridge w/ a collagen-coated membrane w/ a small aperture. Blood is drawn thru the aperture & platelets adhere to the membrane. When a sufficient number of platelets have adhered & aggregated, blood can't flow through aperture. Time is recorded |
| Thrombocytopenia | A condition that involves a decrease in the number of circulating platelets |
| Thrombopathia | Glossary: A condition in which there is a deficiency of clotting ability for reasons other than thrombocytopenia; In text: abnormal or alteration in platelet function |
| Platelets | Irregular, disc-shaped fragments of megakaryocytes in the blood that assist with blood clotting |
| Thrombin | Enzyme formed from prothrombin, calcium & thromboplastin in plasma during the clotting process. Causes Fibrinogen to change to fibrin, which is essential to form a clot |
| Thrombocytes | aka Platelets; cytoplasmic fragments of bone marrow megakaryocytes |
| Thrombocytosis | A condition that involves an increase in the number of circulating platelets |
| Thrombopoiesis | The production of platelets |
| Platelet count | performed with automated hematology analyzers |
| What can cause an automated analyzer to give an inaccurate platelet count? | Platelet clumping and platelet/RBC overlap |
| What blood sample should be used when performing platelet counts? | Freshly collected EDTA |
| Results from automated analyzers should be verified with with what | peripheral blood film aka blood smear |
| Morphologic changes in platelets include what? | Aggregation and giant platelets. These abnormalities will not be evident with automated analyzers and must be detected on blood smear |
| What blood tube is usually drawn first? | The citrate tube is generally drawn first so that it is not contaminated with gel activators or anticoagulants from other tubes |
| polycythemia | the blood has a higher-than-normal concentration of red blood cells |
| The volume of citrate to use is based on the expected plasma volume | Citrate volume should be adjusted accordingly for patients with significant abnormalities of the red cell mass |
| If blood is added in the 1 : 9 ratio, anemic samples will be what? Resulting in what? | Undercitrated which will result in shortened clot times |
| If blood is added in the 1 : 9 ratio, polycythemic samples will be what? Resulting in what? | Overcitrated, which will result in prolonged clot times |
| Samples should never be collected through indwelling catheters why? | Small amounts of fibrinogen, fibrin, and platelets are generally found around the catheter |
| Patient excitement during sample collection can do what? | Can increase the platelet count in addition to activating platelets/clotting mechanisms. |
| The volume of citrate required can be calculated | Volume of Citrate required = 0.00185 x blood volume to be collected x (100 - Hematocrit %) |
| (Citrate) tubes should be stored how? | Room temperature, upright with vibrational trauma avoided (not on rocker) |
| When should most tests be performed? | Within 2 hours, or centrifuged and plasma then frozen |
| fibrometer | When the reagent is dispensed from the pipette, the timer is triggered, and the unit drops a pair of small wires into the sample cup. The wires move back and forth through the sample cup until a clot is detected. No longer in widespread use. |
| thromboelastography | Eval. of the entire clotting process, from the formation of the initial clot through fibrinolysis. Results are usu. graph & used to identify if pt is hypercoagulable or hypocoagulable Google: test assesses the ability of blood to clot & dissolve clots |
| thromboelastograph measures what? | measures the time required for clot formation, the evaluation of the strength of the clot, and the time required for the breakdown of the clot |
| 1. hypercoagulable 2. hypocoagulable | 1. Characterized by abnormally increased coagulability. 2. Characterized by abnormally decreased coagulability |
| Monovette | One of the best ways to eliminate at least some platelet activation is to use a Vacutainer or a Monovette (Fig. 15.1), rather than a syringe and needle to collect the sample |
| Patient excitement and excessive venous stasis can later coagulation test results | Intentionally Blank |
| Most coagulation tests involve the use of sodium-citrate–anticoagulated plasma. | Intentionally Blank |
| EDTA-anticoagulated samples are preferred for the evaluation of platelet numbers. | Intentionally Blank |
| For coagulation testing, the proper ratio of citrate to blood is 1 part citrate to 9 parts whole blood. | Intentionally Blank |
| Platelet evaluation includes what? | a platelet count, platelet indices, and tests of platelet function. |
| Platelet estimates can be performed in a variety of ways using the blood smear from the differential blood cell count. | Intentionally Blank |
| Specialized tests for reticulated platelets and antiplatelet antibodies are performed at reference laboratories. | Tests not suitable for the general practice lab |
| Platelet indices include what? | plateletcrit, platelet distribution width, and mean platelet volume. |
| Platelet numbers should be evaluated in a monolayer area of the blood film. How many fields should be counted? | The numbers of platelets in a minimum of 10 microscopic fields should be counted |
| How many platelets per oil-immersion field are seen in a normal patient?Blank | Generally, 8 to 10 platelets per oil-immersion field are seen in normal patients |
| Multiplying the estimated platelet number (as averaged over 10 fields) by | 15,000 or 20,000 is also used as an indirect measure of the platelet count. |
| Platelet estimates are performed with the use of the blood smear used for the differential blood cell count | Intentionally Blank |
| Patients with thrombocytopenia may have larger than normal platelets called | Megaplatelets |
| Reticulated platelets | Reticulated platelets represent newly released platelets, and they contain high levels of RNA (Fig. 16.2). They are analogous to reticulocytes in that they demonstrate bone marrow responsiveness. |
| Mean Platelet Volume | MPV is the mathematical average of the size of the individual platelets, measured in femtoliters |
| An increased MPV may be expected in situations in which | the increased loss, destruction, or consumption of platelets is accompanied by megakaryocytic hyperplasia |
| Accelerated thrombopoiesis tends to result in the release of | larger platelets |
| What species tends to have larger platelets in healthy animals? | Cats have larger platelets therefore Mean Platelet Volume may not be a useful value |
| Analyzers may count larger platelets as? | White Blood Cells (WBCs) |
| Which canine breed tends to have larger platelets? | Cavalier King Charles Spaniels |
| A high MVP in dogs indicates what? | Adequate bone marrow response |
| An increased MPV may be expected in situations in which | the increased loss, destruction, or consumption of platelets is accompanied by megakaryocytic hyperplasia |
| Accelerated thrombopoiesis tends to result in the release of | larger platelets |
| What species tends to have larger platelets in healthy animals? | Cats have larger platelets therefore Mean Platelet Volume may not be a useful value |
| Analyzers may count larger platelets as? | White Blood Cells (WBCs) |
| Which canine breed tends to have larger platelets? | Cavalier King Charles Spaniels |
| A high MVP in dogs indicates what? | Adequate bone marrow response |
| Plateletcrit | aka thrombocrit, is a measure of the percentage of the total blood volume that is comprised of platelets. Comparable to PCV (hematocrit) for RBCs |
| thrombocrit | aka plateletcrit is a measure of the percentage of the total blood volume that is comprised of platelets. Comparable to PCV (hematocrit) for RBCs |
| How is the plateletcrit/thrombocrit determined? | By multiplying the total platelet count by the MPV. |
| The value of the plateletcrit/thrombocrit for most mammals is what percent? | Typically less than 1% |
| Platelet Distribution Width | assesses variations in the size of the platelets |
| Larger platelets may be seen in patients with | thrombocytopenia |
| Platelet width may be altered depending on | how recently the platelet was released from the bone marrow |
| Platelet width is also increased when | platelets are activated |
| platelet–large cell ratio | a measure of the percentage of platelets that are larger than normal |
| Antiplatelet antibody assays | immunoassays designed to identify antibodies that have adhered to the surface of platelets. Not practical for performance in the practice laboratory. |
| What is the term to describe the average size of individual platelets in a sample? | Mean Platelet Volume (MPV) |
| What is the term for the percentage of the total blood volume that is comprised of platelets? | plateletcrit/thrombocrit |
| What test evaluates the variability in the size of platelets? | Platelet Distribution Width |
| What test provides a measure of the percentage of platelets that are larger than normal? | platelet–large cell ratio |
| What is the term to describe newly released platelets that contain high levels of RNA? | Reticulated platelets |
| What coagulation test uses a collection tube containing diatomaceous earth? | Activated Clotting Time |
| What coagulation test evaluates the extrinsic coagulation pathway? | Prothrombin time (PT) tests |
| What are D-dimer and FDP tests used to evaluate? | aids in identifying the presence of DIC and to provide diagnostic information in cases of liver failure, trauma, and hemangiosarcoma |
| What is the PIVKA test used to evaluate? | differentiate rodenticide toxicity from primary hemophilia |
| What test represents a primary assay for the evaluation of platelet number and function? | Buccal Mucosa Bleeding Time (BMBT) |
| Buccal Mucosa Bleeding Time (BMBT) | a primary assay for the detection of abnormalities in platelet function |
| Activated Clotting Time (ACT) | The activated clotting time (ACT) test can evaluate every clinically significant clotting factor except factor VII. |
| Whole Blood Clotting Time | performed via the Lee–White method, is an older test of the intrinsic clotting mechanism. Whole blood clotting time tests are not commonly performed, because the ACT is more sensitive. |
| Activated Partial Thromboplastin Time (APTT) | Evaluates the intrinsic and common clotting mechanisms. The time that it takes to form fibrin is determined |
| Prothrombin Time Test which are also referred to as one-stage prothrombin time tests (OSPT) | Evaluates the extrinsic and common coagulation pathways |
| Clot Retraction Test | An older, crude but simple test that allows for the evaluation of platelet number and function and of intrinsic and extrinsic pathways. Abnormalities in the test result do not provide information regarding the cause or source of the coagulopathy |
| Fibrinogen Determination | The fibrinogen estimate is then calculated with the use of the following equation, with all values given in milligrams per deciliter: total solids nonincubated minus total solids incubated = fibrinogen mg/dL |
| PIVKA | Proteins induced by vitamin K deficiency or antagonists; the nonfunctional precursor forms of vitamin-K–dependent coagulation factors. |
| D-Dimer and Fibrin Degradation Products | are formed as a clot is degraded. These tests are therefore useful aids in identifying the presence of DIC and to provide diagnostic information in cases of liver failure, trauma, and hemangiosarcoma |
| Von Willebrand Factor (vWF) | required for platelet adhesion. When platelet function defects are evident, a vWF assay is generally performed. |
| Coagulation Factor Assays | can be used to identify specific factor deficiencies are performed in reference laboratories, and they are generally performed to identify specific hereditary factor deficiencies. |
| This test may help to differentiate rodenticide toxicity from primary hemophilia when activated clotting time is prolonged | PIVKA testing or by the Thrombotest |
| The normal whole blood clotting time for dogs is; for horses, it is 4 to 15 minutes, and for cattle it is 10 to 15 minutes. | 2 to 10 minutes |
| The normal whole blood clotting time for horses is | 4 to 15 minutes |
| The normal whole blood clotting time for cattle is | 10 to 15 minutes. |
| This test involves the use of a citrated plasma sample to which tissue thromboplastin reagent is added. A reagent that has been designed to recalcify the sample is then added | Prothrombin time (PT) tests |
| von Willebrand Disease | Inherited disorder characterized by the abnormally slow coagulation of blood as well as spontaneous epistaxis and gingival bleeding. It is caused by a deficiency of a component of factor VIII. Excessive bleeding is common after injury or surgery. |
| What coagulation assay is a good screening test for rodenticide ingestion? | The prothrombin time is generally the first coagulation test to increase, followed by activated partial thromboplastin time and activated clotting time. The PIVKA test has also been suggested as a diagnostic aid |
| What is the most common inherited coagulation disorder of dogs? | Hemophilia A |
| What term describes the presence of pinpoint hemorrhage? | Petechia |
| What is usually found on a blood smear from patients with DIC? | Schistocytes are often present on the blood film |
| Deficient or defective production of what coagulation factor results in hemophilia A? | Factor VIII deficiency |
| What is the most common coagulation disorder of domestic animals? | von Willebrand disease (vWD). The disease results from the decreased or deficient production of von Willebrand factor |
| What are the vitamin-K dependent coagulation factors? | Factors II, VII, IX, and X |
| What is the primary site for the production of coagulation factors? | The liver - The liver is the primary site for the production of coagulation factors |
| Bleeding disorders may be caused by congenital or acquired defects in | coagulation proteins, platelets, or the vasculature |
| Most bleeding disorders found in veterinary species are | secondary to some other disease process |
| Primary coagulation disorders are rare, and they are usually the result of | an inherited defect in the production of coagulation factors |
| Signs of deficiencies in coagulation proteins | usually involve delayed deep-tissue hemorrhage and hematoma formation. |
| Signs of deficiencies of platelets include | superficial petechial and ecchymotic hemorrhages, epistaxis, melena, and prolonged bleeding at injection and incision sites |
| ecchymotic hemorrhages | a bruise |
| petechial hemorrhages | small, pinpoint-sized red or purple spots that appear on the skin or mucous membranes due to bleeding from capillaries |
| The majority of congenital coagulation factor disorders in veterinary species involve | a deficiency or abnormality of a single factor. |
| clinical signs usually appear before the animal reaches | 6 months of age |
| Hemophilia | A genetic abnormality of hemostasis that results from the deficient production of certain coagulation factors. |
| Hemophilia A | is the most common inherited coagulation factor deficiency in dogs, and it is caused by Factor VIII deficiency |
| Hemophilia B, which is also called | Christmas disease, results from Factor IX deficiency |
| von Willebrand factor (vWF) is | a large glycoprotein that circulates with Factor VIII and functions to assist with platelet aggregation at the initiation of the coagulation pathways |
| von Willebrand factor (vWF)occurs with relative frequency in | Dobermans |
| disseminated intravascular coagulation (DIC) | An acquired secondary coagulation disorder characterized by the depletion of thrombocytes & coagulation factors. Also referred to as consumption coagulopathy and defibrination syndrome |
| disseminated intravascular coagulation (DIC) may manifest as | systemic hemorrhage or microvascular thrombosis |
| thrombosis | a medical condition where a blood clot forms within a blood vessel, blocking blood flow |
| Fibrinolysis | the natural process of dissolving blood clots |
| disseminated intravascular coagulation (DIC) | DIC is a consumptive coagulopathy that occurs secondary to other disease conditions |
| 1. Melena 2. Epistaxis | 1. Blood in the stool 2. Nose bleed |
| Aspirin and acetaminophen are common toxins implicated in thrombocytopenia and do what? | These medications may destroy or permanently inhibit the circulating platelets, so clinical signs may not resolve until undamaged platelets begin to be released from the bone marrow |
| Actual Quiz Question: Which of the following clinical signs of a bleeding disorder refers to blood in the stool? | Melena |
| Actual Quiz Question: Which term best describes a process that requires platelets, a number of coagulation factors, and complex reaction pathways? | Hemostasis |
| Actual Quiz Question: Which manual blood coagulation test requires the use of a Vacutainer tube that contains an additive such as diatomaceous earth or kaolin? | activated clotting time (ACT) test |
| Actual Quiz Question: Which of the following coagulation tests uses a citrated sample in a tube to which thromboplastin reagent is added followed by a reagent designed to recalcify the sample, forming a clot within 6 to 20 seconds? | Prothrombin time (PT) test |
| Actual Quiz Question: Which of the following medications may destroy or inhibit the platelets in peripheral blood so significantly that improvements in clinical signs will not be evident until undamaged platelets are released from the bone marrow? | Acetaminophen |
| Actual Quiz Question: Why do most automated hematology analyzers have a high rate of inaccuracy in platelet counts? | Platelet clumping and overlapping with RBCs |
| Actual Quiz Question: Which type of coagulation analyzer can use either whole blood or citrated samples and the results are usually provided graphically, including the clotting time, and length of the time to break down the clot? | Thromboelastograph |
| Actual Quiz Question: Which of the following is attracted to the charged surface of the blood vessel endothelium when the vessel is ruptured? | Platelets |
| Actual Quiz Question: Which is generally the first coagulation test run if vitamin K deficiency is suspected? | Prothrombin time |
| Actual Quiz Question: Which of the following statements is true regarding most bleeding disorders in veterinary species? | They are secondary to some other disease process |
| Actual Quiz Question: Which Vacutainer tube should be collected first when multiple sample types are needed from the same patient? | Blue-top |
| Actual Quiz Question: What is another name for hemophilia B? | Christmas disease |
| Actual Quiz Question: Which of the following could result if a tourniquet is in place over a blood vessel for too long prior to collecting a blood sample? | The platelet count may be elevated in the blood sample |
| Actual Quiz Question: Which term describes a decrease in the amount of platelets circulating in peripheral blood? | Thrombocytopenia |
| Actual Quiz Question: Which of the following is required to stabilize the platelet plug over a ruptured blood vessel? | von Willebrand factor |
| Actual Quiz Question: Which condition is characterized by microvascular thrombi that consume platelets and the coagulation factors that lead to systemic hemorrhage? | Disseminated intravascular coagulation |
| Actual Quiz Question: Which type of coagulation analyzer uses wires that gently move back and forth through the sample cup to detect clot formation? | Fibrometer |
| Actual Quiz Question: Which of the following is likely to occur when collecting a blood sample from a very excited patient that is struggling during restraint for blood collection? | The platelet count may be elevated in the blood sample |
| Actual Quiz Question: Which type of coagulation analyzer uses disposable cartridges when a collagen-coated membrane and measures the adhesion and aggregation of the platelets? | Platelet function analyzer |
| Actual Quiz Question: Which term refers to the body's ability to maintain the integrity of the blood and the blood vessels? | Hemostasis |
| Actual Quiz Question: Which term best describes a process that requires platelets, a number of coagulation factors, and complex reaction pathways? | Hemostasis |
| Actual Quiz Question: Which term refers to a decreased number of platelets and is the most common acquired coagulation disorder in domestic animals? | The book really fucks this up but the answer on the quiz is either thrombocytopenia or hemophilia. who knows |
| Actual Quiz Question: Which term refers to the membrane-bound cytoplasmic fragments released from platelets that increase the surface area to aid in coagulation? | Microparticles |
| Actual Quiz Question: |
Created by:
shawamber