Coags Flashcards
intrisnic pathway
XII, XI, IX, VIII
extrisnic pathway
III and VII
Common pathway (where they converge)
X, V, prothrombin (II), fibrinogen (I)
measures extrinsic and common pathways
prothrombin time (PT): factor I, II, V, VII, X
normal prothrombin time (PT)
11-13.5s
Critical PT time
> 20 seconds
prolonged PT can suggest
deficiencies in extrinsic pathway factors (VII) or presence of inhibitors (warfarin, liver disease)
What can cause a factor deficiency?
hepatocellular disease, obstructive biliary disease, oral anticoagulant, hereditary factor deficiency
or
alcohol, diet high in fat or leafy vegetables, allopurinol, ASA, barbiturates, beta lactam antibiotics, glucagon, heparin, massive blood transfusion, DIC
PT may be elevated or may be 1.5x normal in
fully anticoagulated patient
What can cause a shortened PT
PT = Vit-K dependent factors, anabolic steroids, Vit K, digitalis, benadryl, OCPs
aPTT normal range
25-35s
activated partial thromboplastin time measures
intrinsic and common pathways
critical aPTT value is
> 70 seconds
aPTT is used to monitor
heparin therapy
a in aPTT stands for
activator
prolonged aPTT can stand for
intrinsic pathway issues (hemophilia, factor deficiencies) or presence of inhibitors (heparin, lupus anticoagulant)
decreased aPTT could be
early stages of DIC, extensive cancer
What can interfere with aPTT?
antihistamines, ascorbic acid, heparin, salicylates
standard method of expressing PT to monitor warfarin therapy
INR
normal INR
.8-1.2
Critical INR
> 5
high INR =
risk for bleeding
measures the conversion of fibrinogen to fibrin
thrombin time
abnormalities in TT could be from
fibrinogen deficiency or presence of inhibitors (anticoagulants)
Normal activated clotting time
70-120s
on anticoagulant = 150-699s
When do you need ACT?
measure anticoagulant effect of heparin or other thrombin inhibitors
- cardiac angioplasty
- hemodialysis
- cardiopulmonary bypass surgery
ACT measures
time it takes for whole blood to clot after addition of particulate activators
What can monitor the response of unfractionated heparin therapy and determine amount of protamine sulfate needed to reverse heparin effectS?
ACT
What can interfere with ACT?
- hypothermia, hemodilution, platelet # and function, pharmacokinetics of heparin
increased = heparin, clotting factor deficiencies, cirrhosis, coumadin, lupus inhibitors
decreased = thormbosis
ACT is more useful than
aPTT when high doses are used (during cardiopulm bypass surgery)
ACT is ___ expensive
less, be done more easily
normal D dimer
<.4
D-dimer indications
intravascular clotting
what assesses both thrombin and plasmin activity
d-dimer:
degrades product of fibrin as plasmin acts on clot
What interferes with a D-dimer?
decreased in lipemic patients, increased if rheumatoid factor (RF) is >50, normal <20
What can increase a d-dimer
-DIC
-primary fibrinolysis
-DVT
-PE
-arterial thromboembolism
-sickle cell anemia w or w/o crisis
-malignancy, pregnancy, surgery
monitoring warfarin
PT/INR
monitoring heparin
aPTT
