Coagulation Testing Flashcards
when should you perform coagulation testing?
unexplained bleeding
pre-operative testing
monitoring anticoagulation
what is tissue factor?
potent coagulator, usually inside cells
release triggered by inflammation
what does PT test?
extrinsic pathway of coagulation
what does aPTT test?
intrinsic pathway of coagulation
what factor is in the extrinsic pathway?
factor VII
what are the commonly available coagulation tests?
prothrombin time (PT)
activated partial thromboplastin time (aPTT)
thrombin time
fibrinogen
platelet count
vWF assay
viscoelastic testing: thromboelastography, VCM
what should be avoided when collecting a sample to use for coagulation testing?
probing for vessel
excessive vacuum
when mixing citrate with blood, what is the correct ratio?
one part citrate
nine parts blood
what is mild thrombocytopenia?
150,000-200,000/ul
what is moderate thrombocytopenia?
100,000-150,000/ul
what is severe thrombocytopenia?
50,000-100,000/ul
what is profound thrombocytopenia?
<50,000/ul
what should you think about if you have platelet bleeding but a normal platelet count?
platelet function
what are some things that impact platelet function?
Von Willebrand’s disease
uremia
drugs
what can you use to test for platelet function?
buccal mucosal bleeding time
what does the extrinsic pathway start with?
tissue factor expression
why might a patient have a prolonged PT?
vitamin K deficiency
anticoagulant rodenticide toxicity
liver failure
what is factor VII dependent upon?
vitamin K
what test should you use to check for hemophilia?
aPTT
what might a prolonged aPTT mean?
acquired and hereditary disorders
hemophilia A and B
anticoagulation with heparin
what does thrombin time measure?
‘functional’ fibrinogen
what might cause hypofibrinogenemia?
DIC
liver failure
bleeding- consumption
what might a shortened PT/aPTT mean?
maybe hypercoagulable state
what are fibrinogen degradation products?
fibrin degradation product
D-dimer
what is D-dimer useful for?
if super high: maybe helpful
negative predictive value
what can a thromboelastography test tell us?
hemostatic changes
hypercoagulability
fibrinolysis
when might you see hyperfibrinolysis?
greyhounds
trauma
bleeding states (hemoperitoneum)
acute liver disease
what are some common coagulopathies?
thrombocytopenia
von willebrand’s disease
anticoagulant rodenticide
DIC
what are some less common coagulopathies?
dilutional
traumatic
hemophilia
drug-induced
what tests can you use to look for von willebrand’s disease?
index of suspicion
vWF assay or buccal mucosal bleeding time
what are the positives of doing a blood smear?
cage-side platelet count
inexpensive
rapid scan to look for clumping
immediate result
avoid delay in therapy
drive diagnostic planning
serial monitoring
how do we treat ITP?
immunosuppressives
vincristine
whole blood or packed red blood cell transfusions
should you do platelet transfusions in ITP?
only if bleeding out
when should you consider the potential role of hyperfibrinolysis?
bleeding: spontaneous or traumatic hemoabdomen
what does dilutional coagulopathy follow?
fluid resuscitation
when is dilutional coagulopathy most significant?
surgical diseases
do platelet blockers affect the platelet count?
no
what are the tests for monitoring anticoagulation?
aPTT
anti-Xa activity
what does anti-Xa activity test?
low molecular weight heparin
what can cause hypercoagulability?
systemic inflammation
empiric anticoagulation
what laboratory findings might point towards a hypercoagulable state?
shortened PT/aPTT
mild thrombocytopenia
fibrin(ogen) degradation products
D-dimers
what do cytokines stimulate?
hypercoagulable state
what are the endogenous anticoagulants?
protein C, antithrombin
decreased in inflammatory disease states
what is the D-dimer assay specific for?
FDP fragment
fibrin breakdown
fibrin formation has to have occurred for ________________ to be present
D-dimers
how can sodium citrate be reversed?
addition of excess calcium
what is the contact activator with activated clotting time?
diatomaceous earth
what are the normal values of activated clotting time in dogs and cats?
dogs <120 seconds
cats <180 seconds
what is activated clotting time used for?
titrate heparin in hemodialysis
when does hypofibrinogenemia occur?
DIC
liver failure
bleeding
is D-dimer or FDPs more specific for fibrinolysis?
D-dimer
what test can you use for hemophilia?
aPTT
what tests can you use for trauma testing coagulopathies?
PT
aPTT
TEG
what tests can you use for dilutional coagulation testing?
PT
aPTT
does the factor percent in hemophilia impact outcome?
no
what are some common causes of unexplained bleeding?
anticoagulant rodenticide toxicity
ITP
trauma
heatstroke
dilution
hemangiosarcoma
what should you do if dilutional coagulopathy is prolonged?
plasma transfusion
what anticoagulants get down-regulated by cytokines?
protein C
antithrombin
what does the test for fibrin degradation products measure?
breakdown of fibrin and fibrinogen: not specific
what do increased values of fibrin degradation products indicate?
fibrinolysis has occured
fibrin formation has to have occurred for ________________ to be present
D-dimers
