Chapter 14 Study Guide Flashcards
what is hemostasis?
hemostasis = the process to stop bleeding and prevent further blood loss
- hemostasis fails = bleeding continues
- excessive hemostasis = blood clotting
different stages of hemostasis
primary hemostasis
1. vasoconstriction = injured blood vessel constricts to reduce blood loss
2. platelet plug = complex of platelets and von Willebrand factor (VWF) → platelets stick to VWF
secondary hemostasis
3. coagulation cascade = formation of fibrin clot → fibrinogen is converted to fibrin
4. clot retraction = components of fibrin clot (platelet plug, fibrin, RBCs) get compacted to form a firm clot
after clot is not needed, it will be broken down
5. fibrinolysis = releases tpa (tissue plasminogen activator)
explain fibrinolysis
fibrinolysis = breaking down the blood clot/fibrin by releaseing tpa (tissue plasminogen activator)
plasminogen → plasmin → plasmin breaks down blood clot → D-dimers
- plasmin breaks down blood clot into D-dimers
- D-dimers = small pieces of broken down blood clot
what are D-dimers?
- what do high amount of D-dimers mean?
- what do low amount of D-dimers mean?
D-dimers = small pieces of broken down blood clot → it was broken down by plasmin
- high amount of D-dimers = there must be a blood clot in the body → bc body is trying to break it down
- low amount of D-dimers = no blood clots → this is normal
normally, we should have a very low amount of D-dimers in the body
what organ produces many of the coagulation factors?
liver produces many of the coagulation factors
- if a person has liver cirrhosis → they are unable to make coagulation factors
are clotting factors active or inactive?
clotting factors are always inactive by default
- clotting factors must be activated by the previous factor before them
what are 2 things that are a must need for hemostasis = coagulation cascade?
calcium and vitamin K = are critical for hemostasis / coagulation cascade
- vitamin K = makes a lot of clotting factors
- calcium = activates a lot of clotting factors
what pathways does calcium and vitamin K work on?
calcium and vitamin K work on all the pathway = intrinsic (platelet) pathway, extrinsic (tissue) pathway, and common pathway
how do we diagnose the pathways?
intrinsic (platelet) pathway = aPTT
- aPTT = activated partial prothromblastin time
extrinsic (tissue) pathway = PT/INR
- PT/INR = prothrombin time/international normalized ratio
what are main points of intrinsic vs extrinsic coagulation
intrinsic (platelet) pathway = contact activation → blood clot is activated from inside of cell = aPTT
extrinsic (tissue) pathway = cell injury from external trauma = PT/INR
what is the common pathway?
intrinsic and extrinsic pathway will both lead to the common pathway
common pathway = prothrombin → thrombin → fibrinogen → fibrin
what drug prolongs bleeding time?
aspirin
dysfunction of what organ can lead to clotting factor deficiency?
dysfunction of the liver can lead to clotting factor deficiency
- this is because the liver makes a lot of coagulation factors
hemophilia (2 types)
hemophilia = inherited (X-linked recessive) disease → male dominant disease
- hemophilia A = factor VIII deficiency
hemophilia A = factor 8 deficiency - hemophilia B = Christmas disease = factor IX deficiency
hemophilia B = Christmas disease = factor 9 deficiency
factor 8 and 9 are part of intrinsic (platelet) pathway = aPTT will be prolonged
- prolonged aPTT
- prolonged bleeding time
- normal platelet count
hemophilia
- bleeding time
- aPTT
- platelet count
hemophilia → intrinsic pathway deficiency
- aPTT = prolonged
- bleeding time = prolonged
- platelet count = normal → hemophilia doesn’t affect platelets
what causes thrombocytopenia?
thrombocytopenia = low platelets
- chemotherapy = bone marrow suppression
- alcohol ingestion
- recent immunizations
what is included in bleeding time?
bleeding time = platelet plug and all 3 pathways → intrinsic (platelet) pathway, extrinsic (tissue) pathway, common pathway
remember…
- intrinsic (platelet) pathway = aPTT
- extrinsic (tissue) pathway = PT/INR
vitamin K deficiency
- platelet count
- aPTT
- PT/INR
- bleeding time (BT)
vitamin k deficiency = less vitamin K → less clotting factors
- vitamin K is needed in both intrinsic (platelet) pathway and extrinsic (tissue) pathway
- normal platelet count
- prolonged/extended aPTT
- prolonged PT/INR
- prolonged bleeding time
vitamin k deficiency in newborn
newborn has melena, bleeding from umbilicus, and hematuria
- melena = black feces made of digested blood
- hematuria = blood in urine
DIC = disseminated intravascular coagulation
- platelet count
- aPTT
- PT/INR
- BT
- D-dimer
DIC = clotting and bleeding occur simultaneously
- there is too much coagulation (blood clot)
- too much bleeding
- DIC patients will have a very high amount of D-dimers
- low platelet count
- prolonged aPTT
- prolonged PT/INR
- prolonged BT
- increased D-dimers
if a patient has a lot of D-dimers in blood, what does that indicate?
very high amount of d-dimers = patient had DIC (disseminated intravascular coagulation)
- the patient has a blood clot
von Willebrand disease (vWD)
von Willebrand disease = inherited defect in von Willebrand factor → leads to excessive bleeding
- autosomal dominant = equal in male and demale population
- prolonged/extended aPTT
- extended bleeding time
- normal platelet count
- normal PT/INR
