Flashcards in Primary Hemostasis and Related Bleeding Disorders Deck (49):
What are the 4 steps of primary hemostasis?
Step1- Transient vasoconstriction of damaged vessel
Step 2- Platelet adhesion to the surface of disrupted vessel
Step 3- Platelet degranulation
Step 4- Platelet aggregation
What are the two actions that mediate the transient vasoconstriction of a damaged blood vessel seen in the first step of primary hemostasis?
Reflex neural stimulation and endothelin release from the endothelial cells
What binds to the exposed subendothelial collagen when tissue damage occurs?
Von Willebrand factor
What binds to the Von Willebrand factor?
Platelets bind Von Willebrand factor through the use of what receptor?
Where is Von willebrand factor derived from? Hint: two separate locations
Weibel Palade bodies of endothelial cells
a-granules of platelets
What mediators are released during platelet degranulation, seen during primary hemostasis?
What is the purpose of ADP, released during platelet degranulation?
Promotes exposure of GPIIb/IIIa receptor on platelets
What is the purpose of TXA2, released during platelet degranulation?
Promotes platelet aggregation
During step 4 of primary hemostasis, platelet aggregation, What substance is used as a linking molecule at the site of injury?
What is expressed at the site of injury that allows for platelet aggregation to occur?
What stabilizes the weak platelet plug that is formed via primary hemostasis?
Coagulation cascade—secondary hemostasis
What are the common clinical features of disorders involving primary hemostasis?
Mucosal and skin bleeding
What are symptoms of mucosal bleeding seen with disorders of primary hemostasis?
Intracranial bleeding (with severe thrombocytopenia)
What are symptoms of skin bleeding seen with disorders of primary hemostasis?
Petechiae (1-2mm)→ sign of thrombocytopenia and not usually seen with qualitative disorders
What are the useful laboratory studies used when a patient is suspected of having a primary hemostasis disorder?
Bone marrow biopsy
What is the range for a normal platelet count and at what level do symptoms usually occur?
Why is a blood smear used to assess a patient with a primary hemostasis disorder?
Use to assess number and size of platelets
A disease involving autoimmune production of IgG against platelet antigens and is the most common cause of thrombocytopenia in children and adults…
Immune thrombocytopenic purpura (ITP)
Where are the autoantibodies produced in the disease immune thrombocytopenic purpura?
Produced by the plasma cells in the spleen
What is the mechanism for the development of thrombocytopenia in the disease immune thrombocytopenic purpura?
Antibody-bound platelets are consumed by splenic macrophages—leading to thrombocytopenia
Who are the most susceptible to the development of acute immune thrombocytopenic purpura?
A 4 year old patient presents with thrombocytopenia 1 week after having a viral infection. The thrombocytopenia resoled on its own after a few weeks of monitoring. What is the most likely cause of the thrombocytopenia in this patient?
Acute immune thrombocytopenic purpura
Acute immune thrombocytopenic purpura can present within a few weeks of a viral infection in children. What is another cause of acute immune thrombocytopenic purpura in children?
Who are most susceptible to the development of chronic immune thrombocytopenic purpura?
Women of childbearing age
What is found on laboratory results with respect to platelet count, PT/PTT and megkaryoctye number with immune thrombocytopenic purpura?
Decreased platelet count—often
What is the initial treatment for immune thrombocytopenic purpura?
What is used to raise the platelet count in symptomatic bleeding in patients with immune thrombocytopenic purpura?
IVIG—short lived effects
When patient present with refractory immune thrombocytopenic purpura and all other options have been exhausted, what procedure is performed to eliminate the primary source of antibody and the site of platelet production?
The pathologic formation of platelet microthrombi in small vessels…
Microangiopathic hemolytic anemia
What occurs to RBCs in a patient with microangiopathic hemolytic anemia?
RBCs are sheared—resulting in hemolytic anemia with schistocytes
What is found on biopsy of RBCs in patients with microangiopathic hemolytic anemia?
Microangiopathic hemolytic anemia is seen in what two diseases?
Thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS)
What enzyme is decreased in thrombotic thrombocytopenic purpura that normally cleaves von willebrand factor multimers into smaller monomers?
What occurs due to the decreased enzymatic activity of ADAMTS13 seen in thrombotic thrombocytopenic purpura?
Large, uncleaved multimers lead to abnormal platelet adhesion→ microthrombi
In what group of individuals is the decrease in ADAMTS13 usually seen?
What is the most common cause of the decrease of ADAMTS13 enzymatic activity seen in thrombotic thrombocytopenic purpura?
What is the cause of hemolytic uremic syndrome (HUS)?
Endothelial damage due to drugs or an infection
A 9 year old female presents with skin and mucosal bleeding, microangiopathic hemolytic anemia, fever, and renal insufficiency. She is found to have the stain of E coli O157:H7 caused by eating undercooked beef. What is the most likely diagnosis for this patient?
Hemolytic uremic syndrome (HUS)
What are the 5 clinical findings seen with thrombotic thrombocytopenic purpura and hemolytic uremic syndrome?
1) Skin and mucosal bleeding
2) Microangiopathic hemolytic anemia
4) Renal insufficiency
5) CNS Abnormalities
Of the 5 common clinical findings found in both thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, which one is most commonly seen with TTP?
Of the 5 common clinical findings found in both thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, which one is most commonly seen with HUS?
What are the laboratory findings seen with thrombotic thrombocytopenic purpura and hemolytic uremic syndrome with respect to t bleeding time, PT/PTT, and megakaryocyte count on bone marrow biopsy?
Thrombocytopenia with increased bleeding time
Anemia with schistocytes
Increased megakaryocytes on bone marrow biopsy
What is the treatment for both thrombotic thrombocytopenic purpura and hemolytic uremic syndrome?
Plasmapheresis and corticosteroids
A disease due to a genetic GPIb deficiency, leading to impaired platelet adhesion…
What is seen on the blood smear of a patient with Bernard-Soulier syndrome?
Mild thrombocytopenia with enlarged platelets
A disease due to a genetic GPIIb/IIIa deficiency, leading to impaired platelet aggregation…
What drug irreversibly inactivates cyclooxygenase, which leads to lack of TXA2, impairing platelet aggregation?