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Name the 4 things for Laboratory Evaluation of Primary Hemostasis
•Ivy bleeding time
What are the pros and cons of a platelet count?
- Simple test order to evaluate hemostasis. Quick to obtain, accurate, reproducible.
- Only tells you quantity, doesn’t tell you function.
Normal platelet count is Normal count 150,000-400,000. What if the level is below 150,000, what is it called?
if the levels below 150000 it’s considered thrombocytopenia
At what platelet count do we become concerned for spontaneous bleeding? What about intra-op bleeding??
Spontaneous bleeding is unlikely as long as platelet count is greater than 10,000-20,000,
Intra-op if the count is 40,000-70,000 bleeding can be severe.
How do we obtain an Ivy bleeding time?
- Get paper disc, take a lancet and poke on arm or leg, start timer, take disc and scrape blood off onto paper. Basically taking scraping.
- Inflate BP cuff and small cut on forearm and blot Q30sec. Just absorbing blood until bleeding stops or until it gets excessive
What does Ivy bleeding tell us about platelets?
- Used to try to determine if platelet are functioning properly.
- So prolonged bleeding time may be d/t thrombocytopenia or platelet dysfunction or vascular abnormalities as well
What is a normal Ivy bleeding time?
Normal is 6-9min.
What are the cons of the Ivy bleeding time?
- Much less reliable than platelet count and less reproducible.
- Also require a normal count to get a normal bleeding time.
What is the platelet aggregometry test?
- Testing platelet hemostasis.
- Quantifies platelet aggregation.
- Standardized but time consuming and needs fresh blood.
- Not usually used.
What is the clot retraction test?
- Clot retraction: function of platelet that can be assess grossly and also by thromboelastography.
- If clot is maintained at body temp then clot should retract in 2-4hrs.
What is the Thromboelastogram (TEG)?
- Quantitative version of clot retraction. Evaluation of mechanical properties of the evolving clot.
- Requires integration of platelet aggregation, clotting cascade and fibrinolysis all together. Several parameters can be looked at.
What is R in the Thromboelastogram?
- Reaction time (R) is the interval until the clot starts to form.
- This requires thrombin.
- And prolongation (R increased) it’s usually because of deficiency of intrinsic pathway factor.
What is K in the Thromboelastogram?
- K is the clot formation time.
- It means the time after R until it gets to that width of 20mm.
- An increased K is likely be d/t decreased thrombin. Which then causes decreased fibrinogen and decreased fibrin.
What is the alpha angle in the thromboelastogram?
- Measure of the speed of clot formation (just like K)
- So a decrease in the angle is the same thing as a decrease in K.
- Mainly decrease in thrombin.
What is MA in the thromboelastogram?
Width of the clot (MA) max amplitude of the clot is a measure of the strength of the clot. There is ratio (MA + 60/MA) that’s apparently used widely if it’s less than 0.85 there is abnormal fibrinolysis
What is F in the thromboelastogram?
- F is the interval of MA of the clot to zero amplitude.
- Measure of the rate of fibrinolysis. How quickly the clot is being lysed.
- In normal patient this interval is pretty long the test is usually stopped before it gets to that point
According to Barash, what is important about the tear drop shaped TEG?
In clinical practice, esp. during liver transplants, if you see tear drop is used more to support dx of fibrinolysis rather than numerical values
A TEG is sent during a liver transplant, when would you give FFP, platelets or antifibinolytics?
- Liver transplants if there were to be an increased R that would prompt FFP administration.
- Whereas a decreased MA would trigger platelet administration.
- And if you were to get teardrop pattern then antifibrinolytics would be administered.
In hemophilia, what type of TEG would you see?
Increased R and increased K, takes a long time to clot.
When would we send a TEG?
major cardiac surgery, liver transplant, major trauma.
What type of TEG would we see in thrombocytopenia?
Thrombocytopenia, there’s not enough platelets so there’s not the right amplitude and the clot doesn’t begin as quickly.
PT. What pathway does the it test, what facotors are involved, what is normal?
- Pathway: Extrinsic
- Factors: I, II, V, VII, X
- Normal: 10 -12 sec. or 12-15 sec.
- Misc: INR, Nl = 0.8 – 1.2
aPTT. What pathway does the it test, what facotors are involved, what is normal?
- Pathways: Intrinsic & common
- Factors: I, II, V, VIII, IX, X, XI, XII
- Normal: 25 – 39 sec.
- Misc: Prolonged if ↓ or abn. of all factors except VII, XIII
What factors are invovled in TT and what is the normal?
- Factors: Fibrinogen activity
- Normal: 10-15 sec.
ACT. What pathway is involved & what is normal?
- Pathway: Intrinsic
- Normal: 90 – 120 sec.
- Misc: Point of care & Effects of heparin
Factors must decrease by ___% before the PT is prolonged.
Which factors is PT most and least sensitive to ?
- Most sensitive to decrease in factor 7
- Least sensitive to decrease in factor 2 (prothrombin).
If the PT is abnormal & the aPTT is normal, it’s most likely d/t a factor __ deficiency.
factor 7 deficiency
The aPTT is prolonged if there is problem w/all factors except __ and __.
7 & 13
The aPTT is most sensitive to deficiencies in what two factors?
Most sensitive to deficiencies in 8 and 9 but again these levels have to reduced to about 30% of normal before the test is prolonged.
Besides factors 8 and 9, what else is aPTT sensitive too???
- Really sensitive to inhibition of thrombin as can occur w/ unfractionated heparin.
- So w/ heparin therapy and direct thrombin inhibitors, it's the aPTT that will be prolonged
TRUE or FALSE. Heparin therapy if it goes on for long period of time will also prolong the PT but initially only effects the PTT.
What is the TT measuring??
- measure of the ability of thrombin to covert fibrinogen to fibrin.
- It can also be inhibited by heparin and the direct thrombin inhibitors