Exam 2 -- Hematology #3 Flashcards
How are platelets shaped?
Biconvex
What is the lifespan of a platelet?
About 8 days
What is the function of platelets?
Repair vascular endothelium, prevent excessive blood loss
What factors are involved in platelet activation?
Collagen, thrombin, ADP, epinephrine
What factor is involved with platelet adhesion?
Von Willebrand Factor
What factors stimulate platelet secretion?
ADP, serotonin, fibrinogen, thromboxane A2, growth factors
The clotting cascade, in a basic way, involves thrombin converting fibrinogen into fibrin. What are two cofactors important in this cascade?
Calcium and vitamin K.
Damage to the tissue and subsequent release of coagulation factors from the tissue itself is part of the __________ pathway (intrinsic/extrinsic)
Extrinsic
Damage to the blood vessel endothelium and subsequent release of coagulation factors is part of the ______________ pathway (intrinsic/extrinsic)
Intrinsic
All of the factors involved in the coagulation cascade are synthesized in the liver except one. Which is it, and where is it synthesized?
Von Willebrand Factor, which is synthesized in the blood vessel lining
What factor is incorporated into a clot for later fibrinolysis (clot breakdown)?
Plasminogen; it breaks down the clot after being converted to plasmin
Prothrombin time (PT) and Activated partial thromboplastin time (aPTT) are sometimes included in CBC and are tests that can be done to test the coagulation pathways. Which of these tests is for the intrinsic pathway? Which is for the extrinsic pathway?
PT is for the extrinsic pathway; aPTT is for the intrinsic pathway
What is a normal value for a PT?
~15 seconds
In order to try and standardize PT findings, the international normalized ratio (INR) was developed. What is a normal INR?
1
What is a normal value for an aPTT?
30-50 sec
Bleeding disorders can include what types of signs/symptoms?
Petechiae (broken capillaries), purpura (larger broken capillaries), ecchymosis (bruise), epistaxis (nosebleed), menorrhagia (heavy menstrual period), subconjunctival hemorrhages, gum bleeding.
Vitamin C (aka ascorbic acid) plays what important roles?
Aids in collagen synthesis, reduces free radicals, maintains plastaglandin/prostacyclin balance
Vitamin C deficiency (aka scurvy) takes how long to develop? How quickly can it resolve if the deficiency is resolved?
4-8 months to develop, days to weeks to resolve
What is the recommended daily intake of vitamin C?
75 mg
What can cause thrombocytosis (too many platelets)?
Splenectomy, polycythemia vera, inflammatory conditions (IBD), metastatic cancer, trauma
How would you treat thrombocytosis?
Hydroxyurea, aspirin
What can cause thrombocytopenia?
Aplastic anemia, spleen enlargement, alcohol*, vitamin deficiency, drugs (aspirin, warfarin, chemotherapy)
Hemophilia is a coagulation disorder. What is it caused by? What is its prevalence?
X-linked recessive disease (1/5000 males)*
Hemophilia causes a decrease in which coagulation factor? Which pathway is this factor a part of?
Factor VIII; intrinsic pathway
What are some of the signs/symptoms of hemophilia?
Spontaneous bleeding, hemoarthrosis (blood in joint) potentially leading to joint deformiity and crippling
Suppose a patient with hemophilia has a PT and aPTT done. What would be the results of these tests?
aPTT would be high, PT would be normal
What are some treatment options for hemophilia?
Factor VIII infusion, desmopressin (increases factor VIII and VWF), anti-fibrinolytic agents, gene therapy
Von Willebrand Factor participates in platelet adhesion to damaged endothelium. It also stabilizes which coagulation factor?
Factor VIII
What can cause Von Willebrand Disease?
Autosomal dominant or recessive diseases
How would levels of VWF and factor VIII be a patient with Von Willebrand Disease?
Both would be low
aPTT can be variable in a patient with Von Willebrand Disease. Why is this?
Enough factor VIII, even in the absence of VWF, can normalize aPTT measurements
What are some treatment options for Von Willebrand Disease?
VWF infusion, factor VIII infusion, desmopressin (increases factor VIII and VWF), anti-fibrinolytic agents, gene therapy
Vitamin K is a fat-soluble vitamin needed in the coagulation process. It is involved with several coagulation factors (II, VII, IX, X). Which of these factors was mentioned in class as being more dependent on vitamin K than the others?
Factor VII (extrinsic pathway)
What sorts of issues can cause vitamin K deficiency?
Cirrhosis, alcohol OD or chronic alcohol use (things that affect the liver, since vitamin K is stored there)
Suppose a patient with vitamin K deficiency has a PT and aPTT done. What would be the results of these tests?
PT would be high, aPTT could be high or normal
How would you treat vitamin K deficiency?
Oral or IV vitamin K (90mcg for women, 120mcg for men); discontinue anti-coagulants such as warfarin
Thrombus vs. embolus: which is a solid mass attached to a blood vessel wall? Which is a fragment that can travel throughout the BVs?
Thrombus is the solid mass attached to a BV wall; embolus is the traveling fragment
True or false: if a thrombus occurs in an artery, it is most commonly at a bifurcation
True.
If a venous thrombosis occurs, it is caused by valve stasis or venous obstructions. What are risk factors that increase the likelihood of this happening?
Increased weight, age, bed rest
Deep Vein Thrombosis (DVT) is when a thrombus occurs in a deep vein, often in the legs. If a fragment breaks from a DVT, where does it commonly end up?
Lungs
True or false: pulmonary embolisms are the most common preventable cause of hospital deaths
True.
What are symptoms of a pulmonary embolism?
Shortness of breath, chest pain, cough.
How would you treat a DVT or a pulmonary embolism?
Mobilization, elevate legs, use compression stockings, anti-coagulation meds
What are three different ways that thrombosis treatment drugs can work? Give a couple of examples of drugs in each category.
Inhibit platelets (aspirin, clopidogrel), break down clots (streptokinase), inhibit coagulation factors (heparin, warfarin, dabigatran)
Heparin and warfarin inhibit the coagulation cascade in different ways. How might you want to monitor a patient on heparin? On warfarin?
Heparin: monitor with aPTT since it inhibits the intrinsic pathway; warfarin: monitor with PT and INR since it inhibits the extrinsic pathway
Warfarin is contraindicated in what common condition?
Pregnancy
Patients will experience increase anti-coagulation if they take warfarin and they’re also on what other drugs?
Anti-depressants, anti-psychotics, sulfonamides, antibiotics, aspirin, alcohol
For a patient is on warfarin, be aware that AREDS (for AMD), omega-3, and alcohol may cause additional bleeding due to increased blood thinning properties
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