CHAPTER 1 - HEMOSTASIS PART 7 Flashcards
must be avoided
Hemolysis
Rbc contains(platelet activator)
ADP
May cause premature activation of
platelet if released in the plasma
Hemolysis
is the anticoagulant of choice (except for glass bead retention test)
Citrate
pH is very critical and easily affected by recapping method
Citrate
pH is best controlled by this buffer
Citrate
glass bead retention test should
contain
heparin
sample (anticoag) → 60-100 x g → 10 minutes Plasma → plastic/siliconized test tube
Platelet Rich Plasma (PRP) preparation
stored in RT (not refrigerated nor incubated)
Platelet Rich Plasma (PRP) preparation
red cell contamination = hemolysis = release of ADP
Platelet Rich Plasma (PRP) preparation
upper layer that is not touching the red cell
Platelet Rich Plasma (PRP) preparation
sample (remains) → 2000 x g for 10 minutes Plasma → plastic/siliconized test tube
Platelet Poor Plasma (PPP) preparation
layer almost in contact w/ the red cell
Platelet Poor Plasma (PPP) preparation
upper 3⁄4 layer
Platelet Poor Plasma (PPP) preparation
-samples are centrifuged at 2-4 deg celcius
beta-Thromboglobilin (bTG) and PF4 determinations
cold (not RT)
beta-Thromboglobilin (bTG) and PF4 determinations
most stable b/w:
30 minutes to 3 hours
performed 1st
-Ristocetin
plt responds to ristocetin will decerase as the pH of the plasma changes
-Ristocetin
as soon as blood is exposed to air after centri, blood pH will start to decrease, hence aggregation will be affected
-Ristocetin
performed last
Epinephrine
response w/ plt increases w/ time
Epinephrine
tales 60 mins to take effect
Epinephrine
: more sensitive to aggregating agents than @ 37 deg cel
platelets @ room temp
sensitive to RT making them more aggregatable than inside the body
platelets @ room temp
plts prepared for aggregation studies
due to sensitivity to various
aggregating agents
platelets @ room temp
spontaneous aggregation
platelets @ 0-4 deg
beta-Thromboglobilin (bTG) and PF4
determinations
platelets @ 0-4 deg
Measures the ability of the small blood vessels to control bleeding after injury
. Bleeding time
Factors affecting BT
: number of platelets and the ability of platelets to form (?); Thickness and vascularity of the skin and the ability of the blood vessels to (?) may also affect results.
plugs
constrict
Prolonged: when platelet count is lower than (?)or when platelets are dysfunctional.
: in Vwd
: after ingestion of aspirin/aspirin-containing compounds, anti-inflammatory, anticoagulants, and some antibiotics
30 - 50, 000/uL
Puncture is done on the earlobe. bleeding ceases.
Duke method
Reference value: 1 - 3 mins
Duke method
Done on the forearm; Standard pressure applied is 40 mmHg
Ivy method
• Reference value: 1 - 7 mins.
Ivy method
Uses a template containing a standardized slit
Template BT (by Mielke)
Platelet adhesiveness/Retention Test
→ Reference values:
26% - 60%
3 substances required by platelet to adhere successively:
Ionized Calcium, Fibrinogen, ADP
- (?) is not required in vitro/initial adhesion, but required for longer retention and accurate measurement, along w/ ADP
VWF
: involves the formation of plt aggregates in the column (long rubber tubing) where platelet adhesion test will take place; measurement of retained platelets
- Retention