8. Haemostasis cont. Flashcards
coagulation inhibitors
- Tissue Factor pathway inhibitor
- Antithrombin III (inhibits Xa and thrombin)
- Protein C and S
what do protein c and s do
PS inactivates 5a and 8a
PC enhances PS
PC also enhaces fibrinolysis
what are PS and PC dependent on
vitamin K
what is antithrombin enhanced by
heparin
what does tissue plasminogen activator (tPA) do
involved in fibrinolysis
= activates plasminogen to PLASMIN
= which degrades fibrin
what is fibrin degraded into
fibrin degradation products (FDPs)
how does protein C enhance fibrinolysis
inactivates tPA inhibitor
what can FDP number tell us
if abnormal number of clots are being made
e.g. DVT
what else promotes plasminogen breakdown into plasmin
factor 12a
what is streptokinase
drug to break down plasminogen into plasmin
used to breakdown clots
what is used to control plasminogen into plasmin
plasminogen activator inhibitor (PAI-1)
= blocks tPA and factor 12
AND
alpha 2 - antiplasmin = inactivates plasmin
4 types of lab tests done to test haemostatic function
- bleeding time
- platelet count and function
- prothrombin time (PT)
- activated partial thromboplastin time (APTT)
Bleeding time
- bp cuff
- incision made
- bleeding time measured
- # normal is 3-8 mins
- only done if suspected and tests already been done
- tests for low platelet plug formation (thrombocytopenia)
- not fibrin clot
platelet count and function
- full blood count
- bone marrow examination done IF issue with platelet count = shows production of platelets
- PLATELET AGGREGOMETRY
what is platelet aggregometry
measures change in light absorbance as platelets aggregate
= can see if any problems with aggregation that could be from a mutation in glycoproteins
von willebrand assay
can be done to see number of vWB molecules and the type from platelet function tests
which factors does PT test for
factors 7, 10, 5, prothrombin and fibrinogen
normal PT time
10-14 seconds
what can prolong PT time
- liver disease
- oral anticoagulant treatment (OAT) e.g. warfarin
what is INR
international normalised ratio
= standardised version of PT
people taking warfarin need to test this often
what does APTT test
everything PT does
AND 10, 5, prothrmobin and fibrinogen
peolpe on which medication need to test APTT
heparin
what is done to see the specific factor affected
both PT and APTT
- then by seeing which is prolonged, it can narrow down where problem lies
- then specific assays can be done
