Hemostatic monitoring Flashcards
What is PROVETS?
Partnership on Rotational ViscoElastic Test Standardization?
How should samples be prepared before ROTEM or TEG analysis?
cirtrated 1:9 and wait at room temp for 30 min
What are the 3 phases of viscoelastic testing?
- Initiation - precoagulation - beginning of analysis until first strands of fibrin are formed
- stabilization - end of initiation until wides separation - formation of the clot
- lysis - fibrinolysis
What are CT/R and what are they influenced by?
Clotting time (ROTEM), Reaction time (TEG)
time from test activation until clot firmness of 2 mm
dogs
* hematocrits
* plasma FV, FVII, FIX, FX concentrations
What are CFT/K and what are they influenced by?
Clot formation time (ROTEM), K (TEG)
time from end of CT/R until clot firmness of 20 mm
dog
* hematocrit
* Platelet count
* plasma fibrinogen and FV concentrations
What is the alpha angle and what is it influenced by?
- 2mm to 20mm mark line as angle
dog:
* hematocrit
* platelet count
* plasma fibrinogen, FV and FIX
What is MCF/MA and what is it influenced by?
MCF (ROTEM), MA (TEG)
maximum amplitude of the clot, expressed in mm
dog:
* hematocrit
* platelet count
* plasma fibrinogen concentration
How is fibrinolysis quantified in TEG or ROTEM?
TEG: Ly30, Ly45, Ly60
ROTEM: Li30, Li45, Li60
percentage you get is how much of the clot is lyzed (how much of the clot firmness is lost)
What are the reference ranges for the coagulation index in dogs?
greater than 4 - hypercoagulable
less than - 4 hypocoagulable
What activators are added for exTEM or inTEM ROTEMs?
exTEM: Tissue factor
inTEM: ellagic acid
intrinsic pathway TEG: kaolin or ellagic acid
How reliable are viscoelastic tests to detect hyperfibrinolysis?
lack of sensitivity reported in comparison with D-dimer or FDP plasma cc
Can you use viscoelastic testing to monitor heparin therapy?
Not recommended
use of LMWH was not associated with significant alterations of TEG or ROTEM in dogs or cats
List 4 ways of measuring platelet counts
impedence analyzer
laser flow cytometers
quantitative buffy coat analyzers
peripheral blood smear
what values appear on a thrombogram?
- PLT count
- mean platelet volume (MPV) - increased values show increased production/young PLT, decreased can indicate immune mediated destruction
- Platelet distribution width - shows platelet anisocytosis
- platelet morphology
- thrombocrit (plateletcrit)
In what ways can impedence analyzers count platelets incorrectly
- separate cells based on size - large platelets or small RBC may overlapp and be counted wrongly - especially an issue in cats
- clumps of PLTs may be counted as leukocytes
flow cytometer is more reliable - measures cells according to internal complexity
What is a normal BMBT?
Other than primary hemostasis, what can alter the results?
less than 4 min in dogs, less than 1.5 min in cats (2 min in different reference)
severe anemia or polycythemia - change blood viscosity
What is the gold standard for assessing PLT function?
turbidimetric aggregometry
List all factors evaluated by PT.
- FVII
- FX
- FV
- FII
- FI
What is thromboplastin?
combination of phospholipids and TF
What factors are assessed by aPTT?
- FXI
- FXII
- FIX
- FVIII
- FX
- FV
- FII
- FI
How much factor activity may be lost before PT and aPTT appear prolonged?
60-70%
Is PT or aPTT prolonged in vWD and why?
aPTT - because FVIII is affected
What is the half-life of VII in dog and how soon after vitamin K antagonist ingestion is PT typically prolonged?
6.2 hours
24-36 hours later
How do machines measure PT/aPTT
clot is detected via light-emitting diode optical detectors
PT/aPTT recorded when movement of blood falls below predetermined value
What is added to the sample to measure PT or aPTT?
PT - thromboplastin, calcium
aPTT - contact pathway activator, phospholipods, calcium
List examples for contact pathway activators
- ellagic acid
- kaolin
- silica
What are differentials for a shortened PT?
- hypercoagulable stage
- inflammation causing high fibrinogen cc (will shorten aPTT too)
- TF increase in sample from venipuncture
- normal range for the patient
- excessive plasma-to-anticoagulant ratio
What does ACT evaluate?
intrinsic and common pathway
By what percentage do coagulation factor activities need to drop to causee increased ACT?
85-95%
What do grey-top vacutainers contain and what are they used for?
diatomaceous earth - ACT
What is whole-blood clotting time?
whole blood added to a glas tube without anticoagulants
normal animals - should clot within 3-13 minutes
once formed clot should retract to 50% within 1-2 hours
