Haemostasis and Thrombosis Flashcards
is blood clotted in plasma
no (it is clotted in serum)
what is haemostasis
process by which blood loss is prevented
what is required for primary haemostasis
vWF, platelets
what is required for secondary haemostasis
fibrin
what should you administer if low VWF
cryoprecipitate- high in VWF
what blood product to give if platelets low
platelets
what blood product to give if missing clotting factors
FFP
what type of sample for haemostasis test
plasma sample
what does the APTT measure
intrinsic pathway (activated partial thromboplastin time)
what does the PT measure
extrinsic pathway (prothrombin time)
what if the APTT is abnormal and PT normal
problem in the intrinsic pathway
what if the PT is abnormal and the APTT is normal
problem in the extrinsic pathway
what if APTT and PT are abnormal
problem in the common pathway
what factors are involved in intrinsic pathway
XII, XI, IX, X
what factors involved in extrinsic pathway
VII, X
what is the fibrinogen assay for (clauss assay)
fibrinogen- fibrin (IIa- thrombin). see how long it takes fibrin to form
why do you need to test LFTs
as this is where coag factors are produced
what is the normal INR
2-3
what is INR based on
PT: PT patient/PT normal
what factors are affected by warfarin
2,7,9,10
how does warfarin work
blocks vitamin K cycle, which is needed for carboxylation of factors 2,7,9,10
what is the intrinsic pathway responsible for
fibrin production
which pathway is the initiation phase
extrinsic pathway- makes just enough thrombin to trigger- initiation, but not enough to make the fibrin
normal lifespan platelet
7-10 days
when is there reduced lifespan platelets
incr consumption- infection, thrombosis, splenic enlargement
normal conc platelets
140-400 x 10^9/l
what stimulates platelet production
TPO- thrombopoietin
what are coagulation inhibitory factors for
inhibit coag cascade and ensure action of thrombin is limited to site of injury
what are the coagulation inhibitory factors
antithrombin, proteins C and S , tissue factor pathway inhibitor
inherited disorders of vessel wall
hereditary haemorrhagic telangiectasia, Ehlers Danl;os, Marfan
acquired disorders vessel wall
vit C def (scurvy), steroids, normal ageing, amyloid, immune complex deposition
what is Henoch schlonein purpura
allergic vasculitis, after an infection- arthropathy, haematuria, GI
what is thrombocytopenia
decr platelets- below 140
congenital causes thrombocytopenia
fanconi (aplastic anaemia), rare selective congenital defects of platelet production
acquired causes thrombocytopenia
increased destruction- autoimmune, DIC, TTP, drugs, hypersplenism. failure production- bone marrow failure (leukaemia, myeloma, AA, HIV), infiltration (lymphoma, carcinoma)
treatment autoimmune thrombocytopenia
prednisolone, IV Ig, immunosuppressive therapy, splenectomy
what happens in TTP
thrombosis in small vessels, red cell fragmentation, haemolytic anaemia, thrombocytopenia
what happens to PT and APTT in TTP
normal
what is there a deficiency of in TTP
ADAMTS13- normally cleaves VWF
what is haemolytic uraemic syndrome
occurs in childhood. thrombosis in small vessels. follows infection- E coli..
treatment TTP
plasma exchange- FFP. antiplatelets, corticosteroids
target INR pulmonary embolism and DVT
2-3, 3.5 if recurrent
target INR AF
2-3
target INR prosthetic metallic heart valves for stroke prevention
3-4
anticoag in DVT/PE
at least 6 weeks for below knee DVT, at least 3 months for above the knee DVT or PE. at least 6 months if no cause found
what to do if INR is 4.5-6
reduce warfarin dose or omit.restart when INR
what to do if INR is 6-8
stop warfarin. restart when INR
what to do if INR is >8
if no bleeding stop warfarin. 0.5-2.5mg vitamin K if risk factors for bleeding
what to do with warfarin if any major bleed
stop warfarin. give prothrombin complex concentrate. FFP. vitamin K
problem with vitamin K
may take some hours to work and can cause prolonged resistance when restarting warfarirn so avoid if possible if need long term coag
