general homeostasis Flashcards
What are the three natural clotting cascade inhibitors we have talked about?
1) TFPI
2) AT III
3) Proteins S and C
How does blood vessel constriction aid clotting?
1) decrease blood loss
2) bring platelets and clotting factors into contact
What are the two natural clot lysis agents we have talked about?
1) tPA
2) plasmin
What are the two types of granules in platelets and what do they contain?
alpha- fibrinogen and vWf
beta- serotonin, ADP, Ca 2+
What factors are involved in the (S)intrinsic pathway?
12, 11, 9, 8, 5
What factors are involved in the (S)extrinsic pathway?
TF, 7
What factors are involved in the common clotting pathway?
10, thrombin, fibrin
What steps of the (S)intrinsic pathway does protein C inhibit?
factors 5 and 8
TFPI inhibits tissue factor in which clotting pathway?
the (S)extrinsic pathway
What clotting inhibitor inhibits factors 11, 9, TF/ 7 complex, 10, and thrombin?
AT III
What is the only example of negative feedback in the clotting cascade?
activated factor 10 inhibits formation of the TF/ 7 complex
tPA promotes what?
conversion of plasminogen to plasmin
The agent which breaks up clots into Fibrin Degradation Products (FDPs) is what?
plasmin
Tissue factor (TF) is released from/present in what locations?
1) “hidden cells” of the sub-endothelium when they are revealed by damage
2) microparticles are always present in the blood
3) endothelial cells and monocytes during inflammation
What role do phospholipids in platelet membranes play in clotting?
activate coagulation factors
What does glycoprotein (GP) Ia do?
Ia binds collagen
Which glycoprotein (GP) binds vWf?
GP Ib
What does glycoprotein (GP) IIb/IIIa do?
binds fibrinogen
steps for platelet aggregation:
1) proteins exposed
2) platelets adhere
3) granules release
4) platelets aggregate
5) phospholipids exposed
steps for fibrin clot formation:
1) TF exposed
2) cascade begins
3) cascade makes fibrin
4) fibrin solidifies plug
What does a template bleeding time measure and what would an abnormal result indicate?
evaluates platelet response to injury;
a long bleeding time after incision would indicate a platelet disorder
Which platelet test would you use to calculate an “in vitro bleeding time?”
closure time with a platelet function analyzer
You would use a platelet function analyzer that measures how fast platelets occlude holes in a membrane to look for what types of platelet disorders?
aspirin related or von Willebrand factor deficiency platelet disorders
In a platelet aggregation test where aggregating agents are added singly to the patient sample what are you measuring?
a decrease in sample turbidity would indicate aggregation and thus a deficiency of that added factor in the patient sample
Of the two fibrin tests available, which is the more sensitive: FDP assay or fibrinogen assay?
FDP assay, used to rule OUT a minor clot or thrombi
What would a decreased fibrinogen assay result indicate?
DIC or a massive bleed
Of the two fibrin tests available, which is the more sensitive: FDP assay or fibrinogen assay?
FDP assay, used to rule OUT a minor clot or thrombi
What would a decreased fibrinogen assay result indicate?
DIC or a massive bleed
What are the steps for completing a coagulation test?
1) draw blood into citrate tube
2) spin tube and decant plasma,
3) add reagents to plasma
4) watch for fibrin formation
What factor is added to the patient plasma in a prothrombin time test?
thromboplasin: TF and phospholipids and
Ca +2
Where is factor 7 made and what cofactor does it need?
liver, potassium (inhibited by coumadin)
What pathway and conditions do we use INR, a corrected PT, to asses?
(S)extrinsic pathway
1) liver function
2) monitor coumadin levels
3) diagnose DIC
4) pre-op status
What would the addition of coumadin or heparin or a DIC sample do to prothrombin time (PT)?
an increased prothrombin time
What do we use INR, a corrected PT, to asses?
1) liver function
2) monitor coumadin levels
3) diagnose DIC
4) pre-op status
What factors are added to a patient plasma sample to calculate partial thromboplastin time?
phospholipid
What pathway and conditions do we use PTT to asses?
(S)intrinsic
1) abnormal bleeding
2) monitor heparin levels
3) diagnose DIC
4) diagnose anti-phospholipid antibody production
5) pre-op status
What are some conditions that increase PTT?
hemophilia A and B
DIC
presence of Heparin or coagulation pathway inhibitors
In which coag test is thrombin added to the patient plasma sample to measure the conversion of fibrinogen to fibrin and why would you run it?
Thrombin time;
if your PTT is prolonged to rule out fibrinogen problems
What would an increased Thrombin time indicate?
decreased fibrinogen or increased FDP
If your PTT is prolonged but your thrombin time is normal, what test should you order next?
a partial thrombloplastin time (PTT) mixing study
When you add pooled plasma and patient plasma to phospholipids for a PTT mixing study, what does it mean if it corrects? If it does not correct?
corrects: the patient is missing a coagulation factor
does not correct: there is an inhibitor in the patient’s plasma
