Bleeding Disorders Flashcards
what is primary haemostasis
formation of a platelet plug
what is secondary haemostasis
formation of a fibrin clot
failure of what aspects of haemostasis usually cause bleeding disorders
primary and secondary haemostasis
problems with fibrinolysis and anticoag defences less likely
what can cause platelet plug formation failure
vascular (collagen loss, hereditary, acquired)
platelets:
- reduced number (thrombocytopenia- marrow problem, ITP)
-reduced function (drugs e.g. aspirin, anti-inflammatories)
von willebrand factor (hereditary deficiency)
what is thrombocytopenia
reduced platelets
what inheritance is VWF deficiency
AD
affects men and women equally
why does collagen loss cause failure of primary haemostasis
vessel less efficient, more leaky
what hereditary conditions can cause vascular abnormalities
hereditary deficiencies in collagen: marfans, disorders of hyperflexibilty
what are the acquired causes of vascular abnormalities causing failure of primary haemostasis
vasculitis: inflammation of vessel, makes it more leaky
e. g. HSP
scurvy (vit c needed to make collagen)
age- senile purpura
what are the features of henoch schonlein purpura
seen in children
triggered by viral infection
Antibodies to virus stick to vessel wall and make them leaky
mucosal bleeding- purpura on lower limbs
supportive Tx, usually self limiting, occasionally need transfusion
where is purpura most commonly seen
on lower limbs (gravity effect)
can be seen on chest if have cough
fundi on ophthalmoscope
blood blisters in mouth
is hereditary or acquired thombocytopenia more common
acquired
what are the causes of acquired thrombocytopenia
reduced production:
-marrow problem (viral infection, aplastic anaemia, malignancy (mets or blood), chemo, alcohol) (will also have anaemia and low wbc)
increased destruction (most common cause)
- usually autoimmune (ITP)
- coagulopathy (DIC)
- hyperplenism
what is the normal lifespan of a platelet
7 days (in increase peripheral destruction will last couple of hours)
what is seen on blood film in increased peripheral destruction of platelets
large platelets (immature forms)
what is usually the Tx for thrombocytopenia caused by increased peripheral destruction
(treat cause)
usually self limiting problem
Tx in children is to observe
Tx can involve steroids in adults
what causes DIC
(disseminated intravascular coagulation)
trigger (trauma, RTA, sepsis, incompatible transfusion, cancer) that results in tissue damage activates both primary and secondary haemostasis
this uses up clotting factors (prolonged PT and APTT)
blood clots block small blood vessels causing hypoxia which triggers more clots
body recognises this and activated fibrinolysis but this only causes more tissue damage and destroys clotting factors
how does hypersplenism affect platelets
caused by e.g. liver disease, cancer
blood cant get into liver due to cirrhosis and spleen engorges
this then increases transit time of blood through spleen, increasing destruction of platelets
what are the causes of platelet functional defects
hereditary (VWF def)
acquired
- drugs; aspirin, NSAIDs
- renal failure
are NSAIDs antiplatelets or anticoagulants
anti platelets
why does renal failure affect platelets function
due to build up of urea and in blood
what are the causes of VWF deficiency
acquired (autoimmune, antibody to VWF (rare))
hereditary (common, AD, variable severity- generally mild)
what does hereditary VWF def tend to cause
primary haemostatic problems: nose bleeds, gum bleeds, menorrhagia, bleeding after surgery/ dental extraction
(all these mucosal bleeds)
what is the commonest cause of primary haemostatic failure
thrombocytopenia
this is usually acquiredL marrow failure (pancytopenia), peripheral destruction (ITP)
what is the treatment for thrombocytopenia
transfusion (unless caused by increased peripheral destruction)
what is ITP
immune thrombocytopneic purpura
autoimmune disorder with increased platelet destruction and reduced prodcution (can be idiopathic or due to another AI condition, viral infections, H. pylori infections, medications and lymphproliferative disorders)
can occur in adults and children
what can cause a failure in fibrin clot formation
multiple clotting deficiencies (usually acquired e.g. DIC (destroyed), liver failure (not produced))
single clotting factor deficiency (generally hereditary - Heamophilia A and B)
what can cause multiple clotting factor deficiencies
liver failure vit K deficiency/ warfarin therapy complex coagulaopathy (DIC)
how do you measure liver production
albumin
what is the role of vit K
allow carboxylase to make clotting factors negative so they can stick to +ve platelets
WHAT CLOTTING FACTORS ARE MADE WITH VIT K IN EXAMS LEARN THIS
2,7,9 and 10
what antagonises vit k
warfarin
what clotting tests are affected in a multiple factor deficiency
both PT and APTT increased
where are all coagluation factors synthesised
in hepatocytes (reduced in liver failure)
what clotting factors are carboxylated by vit K IN EXAMS
2,7,9,10
what are the sources of vit K
diet intestinal synthesis (made by bacterial in bowl)
where is vit K absorbed and what is needed
in upper intestine
need bile salts to absorb it
why do babies get haemorrhagic disease of the new born
as deficient in vit k- none in breast milk and very little bowel bacterial to make any
what are all babies given at birth
vit k injection
what can cause decreased vit k absorption
bowel disease obstructive jaundice (gallstones)
what are the causes of vit k deficiency
poor diet malabsorption obstructive jaundice vit K antagonists (warfarin) haemorrhagic disease of the new born
what are the dietary sources of vit K
leafy green veg
what causes the clinical features of DIC
excessive and inappropriate activation of haemostasis (primary, secondary and fibrinolysis)
microvascular thrombus formation = end organ failure
clotting factor and platelet consumption= bruising, purpura and generalised bleeding
what are the screening tests for fibrin clot formation
if CF deficiency (multiple- DIC, liver disease, warfarin) then PT and APTT will both be affected
fibrin degredation products (e.g. D-dimers)
what clotting factors are affected by warfarin
2,7,9 and 10
which clotting test is most sensitive
PT and measures CF & which has the shortest half life
what can cause DIC
sepsis (tissue damage due to infection or later shock)
obstetric emergencies (placenta v rich in phospholipid and tissue factor, things like abruption can cause placenta to die causing coagulation)
cancer
hypovolaemic shock
what is the treatment of DIC
treat underlying cause (sepsis 6, fluids)
replacement therapy:
-platelet transfusions
-plasma transfusions (TTP to replace clotting factors)
-fibrinogen replacement (cryoprecipitate)
what is haemophilia
X linked hereditary disorder that causes loss of amplification (CF 8 and 9) process in haemostasis
abnormally prolonged bleeding recurs episodically at one/ few sites on each occasions
does haemophilia affect males or females
males (females can be carriers)
what are the types of haemophilia
A- factor 8 deficiency (most common)
B- factor 9 deficiency
how does haemophilia present
no abnormality of primary haemostasis (fine with small cuts)
mucosal bleeding less common
bleeding will be from medium to large vessels
get target joints- bleeding into ankle, knee and elbow joints causes synovitis which then causes neovascularisation in synovium which are friable and also bleed
what are the severities of haemophilia
mild (>5% CF, only issues after trauma)
mod 2-5% CF
severe <2% CF
what screening tests for haemophilias
APTT will be affected (v prolonged)
looks at CF 8 and 9
what are the clinical features of haemophilia
recurrent haemarthoses
recurrent soft tissue bleeds (bruising in toddlers)
prolonged bleeding after dental extractions/ invasive procedures
(usually FHx, 1/3rd new mutation)
what Tx for haemophilia
prophylactic CF injections every 2nd day
may need joint replacements
