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Hemostasis Tim
J Sarge Hemostasis
| Question | Answer |
|---|---|
| Factor I | Fibrinogen |
| Factor II | Prothrombin |
| Factor III | Tissue factor |
| Factor IV | Ca++ |
| Factor V | Labile factor |
| Factor VII | Stable factor |
| Factor VIII | Antihemophilic factor |
| Factor IX | Christmas factor |
| Factor X | Stuart-Prower factor |
| Factor XI | PTA (plasma thromboplastin antecedent |
| Factor XII | Hageman factor |
| Factor XIII | FSF (fibrin-stabilizing factor) |
| HMWK | High-molecular-weight kininogen, Fitzgerald factor |
| PF3 | Platelet factor 3 |
| VWF | von Willebrand factor (carries VIII) |
| Prekallikrein | Fletcher factor, PK |
| What are platelets? | Fragmentation of megakaryocyte cytoplasm originating in the bone marrow |
| What divides in a megakaryocyte, the nucei or the cytoplasm? | Nuclei |
| How many nuclei will a Promegakaryocyte have? | 2-4 |
| How many nuclei should there be before we call the cell a megakaryocyte? | 8-32 |
| How many platelets may a maegakaryocyte produce? | 2,000 to 7,000 |
| Are some megakaryocytes stored in the lungs? | yes |
| Where are about 1/3 of all platelets stored? | In the Spleen |
| Splenomegaly will do what to the platelets? | Will induce large number of plateleats to be stored |
| Hypersplenism invariably results in what? | Thrombocytopenia |
| What can be done to correct thrombocytopenia? | Remove the spleen |
| How long do platelets survive? | 7-10 days |
| What is normal platelet number in the peripheral blood? | 150K-350k/uL |
| Do platelets have nuclei? | No |
| What are the four main components of hemostasis? | Vascular system, Primary Hemostasis, Secondary Hemostasis, Fibrinolytic system |
| What is the role of the vascular system? | Regulation of the rate of blood flow |
| What is the role of primary hemostasis? | Platelets interact with vascular endothelium, formation of primary hemostatic plug which may initiate clotting cascade, maintain vascular integrity |
| What is the role of secondary hemostasis? | Coagulation system, fibrin is the end product, blood clot. Composed of a series of plasma proteins and cofactors interacting. Extrinsic and Intrinsic Cascades |
| What is the function of the fibrinolytic system? | Clot dissolution. Includes specific set of plasma proteins tasked with prevention of hypercoagulability |
| Describe the different layers of the vessel wall. | Intima (inner), media (middle), adventitia (outer) |
| How does the vascular system prevent bleeding? | Vascontriction, Diversion of blood flow, Initiation of contact activation of platelets, Contact activation of the coagulation system |
| What is fibrinolysis? | The action of removing unwanted fibrin deposits and gradually breaking down fibrin into soluble fragments |
| What mediates fibrinolysis? | Plasmin which is generated by t-PA |
| What does plasmin do? | Splits fibrin into smaller pieces until it gets 2 D fragments and an E fragment. (Fibrin Split or Degradation products- FDPs |
| What can we test for to determine if fibrinolysis has occured? | D dimers or FDPs which include the larger pieces (X and Y) |
| Coagulation is usually measure by what tests? | Prothrombin Time (PT) and Partial Tissue Thromboplastin Time (PTT) |
| What test measures the extrinsic pathway? | Prothrombin Time (PT) |
| What test measures the intrinsic pathway? | Partial Tissue Thromboplastin Time (PTT) |
| The PT test is more sensitive to loss of Factor? than to Factor II? | Factor VII |
| The PT test is inhibited by what drug which inhibits Vitamin K uptake by liver cells? | Coumadin |
| The normal range for the PT test is? | 10-13 seconds |
| What is INR when discussing PT time? | International normalized ratio. This is reported in the PT result and allows standardized comparisons of values. |
| The PTT test is inhibited by? | Heparin |
| The PTT test is most sensitive to intrinsic deficiencies occurring in the cascade prior to Factor? | Factor II |
| When the PT test is prolonged by coumadin, will the PTT test be affected? | Yes, it is also prolonged |
| When an unexplained prolonged PT and/or PTT is encountered clinically, what might be suspected? | A Factor deficiency or circulating inhibitor |
| What might be done to detect a factor deficiency? | Different combinations of serum or plasma containing known Factors are added back to the specimen to correct the deficiency |
| What are the role of platelets? | Provide a negatively charged phospholipid surface for fX and pthrombin activation. Release substances that mediate vasocontriction, platelet aggregation, coagulation, and vascular repair. Provide surface membrane glycoproteins which attach to other p-lets |
| What activates a platelet? | Disruption of vascular endothelium. Exposure of collagen in basement membrane attracts and stimulates circulating platelets |
| Is adhesion reversible? | Yes |
| What does a platelet need to initially adhere to exposed collagen? | von Willenbrand Factor, Collagen and GPIb |
| What happens after the initial adherence to exposed collagen? | Release of ADP from dense bodies.Other platelets are activated through interaction of collagen or other mediators (thrombin, ADP , or TXA2) Immediate shape change and pseudopodia. Formation of primary hemostaic plug |
| Is aggregation reversible? | No |
| Steps in aggregation 1... | Release of more ADP form dense bodies; attraction of adjacent platelets initiating aggregation. Need ATP for energy and Ca++, GPIIb, IIIa and fibrinogen. Fibrinogen activates the GPIIb/IIIa complex. Release of PF3 which further simulates coag process |
| Steps in aggregation 2... | Release of PF4 and other factors promoting clot formation. Initiation of coag cascades and formation of fibrin. Formation of secondary hemostatic plug-irreversible process |
| What platelet granules secrete factors throughout the whole process? | Alpha granules |
| Here are other secretions that are essential for clot formation. | Beta-throboglobulin, PF4, thrombospondin, and PDGF are some of the factors secreted and are used as activation markers. |
| What is Brecker-Cronkite Method? | A manual platelet counting method. 1:100, phase-microscopy and 1% ammonium oxalate. est 11-15% error |
| What is Rees-Ecker Method? | A manual platelet counting method. 1:200, light microscopy and sodium citrate, est 16-25% error |
| What are some reasons for false high platelet counts from automated instrumentation? | Presents of abnormal proteins; macroglobulinemia, uremia, multiple myeloma. Patient undergoing chemotherapy or irradiation may be high due to leukocyte or platelet fragmentation. Contamination from bacteria or other particulate matter. |
| What are some reasons for false low platelet counts from automated indtrumentation? | Sample containing platelet aggultinins and/or cold agglutinins. Satellite phenomenon. Platelet aggregates may be counted as platelets,or not counted at all. Giant platelets counted as RBCs |
| What is a Bleeding Time Test? | The amount if time required for a standard sized wound to stop bleeding |
| Describe the Simplate-Template method for a bleeding time test. | Normaltime is 2.5-9.5 minutes; uses a BP cuff to 40mm/Hg; cut on forearm and bleeding is timed; uses a spring-loaded blade (most commonly used) |
| What factors are in the fibrinogen group? | 1, 5, 8 13 |
| What factors are in the contact group? | 11 and 12 |
| What factors are in the prothrombin group? | 2, 7, 9, 10 |
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