Haemostasis and thrombosis Flashcards
Desribe the 2 clotting mechanisms
Intrinsic — occurs when blood passes over roughened damaged endothelium causing collagen to be exposed e.g due to hypertensive damage
Results in release of clotting factors
Extrinsic - occurs when damage to tissue e.g via cut releases thromboplastin
What occurs after activation of factor X is the same for both :
Prothrombin —> thrombin + factor XIII (via factor X)
Thrombin converts fibrinogen —> fibrin
Factor XIII converts fibrin to stable fibrin
Mediated by serine proteases
Describe the action of platelets
Clotting factors and platelets work in conjunction
Adhere to damaged smooth muscle below endothelial cell of damaged/disease vessel via vWF
Release aggregation factors - ADP and thromboxane (vasoconstrictor)
This leads to expression of glycoproteins IIb-IIIa which allow cross-linking of platelets via fibrinogen and vWF
Describe the lab tests used to investigate platelet dysfuncton and thrombocytopenia (not enough platelets)
Incision to forearm with venous cuff
Increased time for coagulation to occur (denoted by INR)
Healthy INR is 1
Also measure liver function as liver produces many clotting factors
Compare venous and arterial thrombosis
Venous thrombosis are a problem of the coagulation factors event due to blood stasis - anticoagulants used
Arterial thrombosis are a platelet event due to atheroma - antiplatelet drugs
What is a transient ischaemic attack*
Temporary reduction of blood flow to brain
Vascular cause
Symptoms last <24h
No evidence of infarction on imaging
pathophysiology of AF
Spontaneous firing of non pacemaker cells in atria
Abnormal discoordination of ventricular contraction
Disrupted SAN —> AVN conduction
Haemophilia What is it Causes Symptoms Treatment
Genetic - males predominantly affected and female carries
Low/no factor VIII of clotting cascade
Haemorrhage and prolonged bleeding risk
Treated with factor VIII from blood donors or analogue of vasopressin (this increases factor VIII release) ; new monoclonal antibody drug available now as well
Von willebrands disease What is it Causes Symptoms Treatment
Hereditary lack or defect of vWF
Symptoms - increasing bruising, nose bleeds, mucosal bleeding
Treatment - analogue of vasopresssin, factor VIII or vWF from donors
Liver disease can result in reduced synthesis of ____ ____
This leads to increased _____
Clotting factors
Bleeding
Thrombocytopenia
What is it
Causes
Symptoms
Reduced platelet number
Spontaneous skin bleeding
Causes - idiopathic, viral, drug-induced, toxins
What is disseminated intravascular coagulation
Large amount of fibrin made by procoagulant material such as amniotic fluid/infection or massive trauma
Results in widespread haemorrhage and large consumption of platelets/clotting factors but also may be thrombosis
Treat by giving platelets and fresh plasma
What condition increases risk of venous thrombosis
Factor V Leiden mutation
Why does atheroma formation only occur in arteries
Low pressure of blood in veins ; less turbulence
What are the different types of ischaemic strokes ?
Small vessel disease
Large artery atherosclerosis
Cardio-embolic stroke (due to AF)
Unknown causes
Haemorrhagic stroke
Causes
Symptoms
Caused by rupture of artery in brain
Intracebral or subarachnoid (on surface)
Symptoms - headache, nausea, vomiting, reduced consciousness/weakness in one part of body
