Blood 3 Flashcards
what is purpose of homeostasis?
to prevent blood loss
when does the process of haemostasis start ?
as soon as blood vessel ruptured severed or damaged
what is the process of haemeostasis?
- vascular spasms
- platelet activation
- platelet aggregation
- platelet plug
what happens at the same time when platelet activation occurs
coagulation cascade thru intrincs and extrinsic pathway which leads to the final common pathway = prodcution of fibrin plug = blood clot is then propagated with fibroblasts and monocytes and WBC which turn the blood clot into a fibrous scar to price permanaet seal to the blood vessel
what is warfarin?
- interfers at red arrows
- old med
- anti coagulation med
- interfers with vit k metabolism
- Vit K = used by liver to produce factors 2 7 9 10
what are the new DOAC meds?
apixban
rivaroxaban
edoxaban
dabigatran
what are the advantages of taking DOAC?
- fast (once a day or half a day) due to short half life and specific reliable and predictable
- no food or drug interactions compared to warfarin
what does the endothelial lining on vessel wall prevent?
- prevent activation of clotting factors
what happens when we get a rupture to vessel wall?
- exposed collagen fibres
- end their layers disappears
- foreign material that activates intrinsic and extrinsic pathway
blood clot control
plasmin breaks clot down
example 1 management
- do not stop warfarin = this can cause more harm than it solves (SDCEP)
- check INR
- if stable check 72hrs before
- if unstable check 24 hrs before
- INR needs to be 4 or less to do extraction
what is abnormal bleeding ?
bleeding that has continued after a time when normal bleeding would’ve stopped
what are the vast majority of abnormal bleeds due to ?
iatrogenic - caused by pt taking out the anti platlete or anti coagulatant drugs
give some eg of anti platelets
*Aspirin
* Dipyridamole (Persantin)
* Clopidogrel (Plavix)
* Ticlopidine (Ticlid)
* Others…… see BNF
egs of anti coagulants
- Warfarin
- Dabigatran etexilate
- Apixaban
- Rivaroxaban
how does formation of a platelet plug occur ?
how do aspirin and clopidogrel work?
- Aspirin irreversibly binds to platelets
- It inactivates platelet COX (cyclooxygenase) required for thromboxane A2 mediated aggregation
- Clopidogrel binds to the P2Y12 receptor irreversibly and prevents Adenosine Di Phosphate (ADP) mediated aggregation
- Platelets are renewed over about 10 days
- Ibuprofen binds to platelets reversibly
why do ppl who have had a stroke or heart attack take aspirin and clopidogrel?
- rlly good at preventing platelet activation and aggregation and that it lasts a long time meaning if somebody has been taking aspirin there’s no point stopping aspirin as it won’t have an affect
Which patients are likely to be taking clopidogrel or aspirin?
- Vascular disease
- Including ischaemic heart disease
- Or thromboembolic disease
- Or stroke
- Or peripheral vascular disease
- In whom thrombi (platelet aggregations) are likely to form within the vascular system
what is the management of pts on aspirin ?
Do not stop the aspirin
Takes weeks for effect to be reversed
Risk of stopping is greater than risk of continuing
Not stop: bruising, bleeding,
Stop: reduced bleeding but severe complications
what is the normal platelet count?
150,000-450,000
why can thrombocytopenia occur?
due to some medicines (anticonvulsants, sulpha-antiobiotics), hereditary, pregnancy leukaemia
what should we do if we are faced with a pt that has a low platelet count?
consult the haematologist
what is the management of pts with low platelets?
*>80,000/microlitre safe
*Check with haematologist
*May require steroids (ITP)
*Or platelet transfusion
who is warfarin prescribed to?
pts with: Atrial fibrillation;
- Previous pulmonary embolus (P.E.) or deep venous thrombosis (D.V.T.);
- Prosthetic heart valves……
what does warfarin do?
- Antagonises the synthesis of vitamin-K dependent clotting factors (factors II, VII, IX and XI) in the liver.
