M103 T2 L6 Flashcards
What are the causes of bleeding?
Vascular disorders
Platelet disorders
Defective coagulation
What are the patterns of bleeding for vascular and coagulation disorders?
vascular - bleeding into mucous membranes and skin
coagulation - bleeding into joints and soft tissues
What types of vascular bleeding is there?
Inherited (rare) - haemophilia a & b
Acquired (common)
coagulation cascade defect
What is the normal range of platelets? In what range is thrombocytopenia?
150-400 x 10^9/L
thrombo - less than the lower range
What are the symptoms of thrombocytopenia?
Epistaxis
GI bleeds
menorrhagia
bruising
At what platelet level will symptomatic bleeding occur?
when the platelet level falls below 10 x 10^9/L
What are the common aquired causes of thrombocytopenia?
ITP
drug-related
DIC
How is immune thrombocytopenia treated?
steroids and/or intravenous immunoglobulins
thromboietin agonists
immunosuppression
splenectomy
What are the symptoms of immune thrombocytopenia and what are they caused by?
affected individuals can develop red or purple spots on the skin caused by bleeding just under the skin’s surface
What are the acquired causes of disorders of platelet function?
iatrogenic illness
drs prescribing aspirin, NSAIDs that are very effective anti-platelet agents
What is prothrombinase made up of?
factor 10
factor 5
calcium
pplpds (surface of the platelets)
Where does the coagulation happen?
at the surface of the membrane of the platelet - very convoluted
What are the clinical features of Haemophilia A & B?
Spontaneous bleeding into joints and muscle
Unexpected post-operative bleeding
Chronic debilitating joint disease
Family history in majority of cases
What are consequent conditions due to haemophilia?
major haematoma
haemarthrosis
chronic joint deformity
intra-cranial bleed
Describe the genetics of a haemophiliac family
mother carrier - sons will have haemophilia, daughters will be carriers
positive father - sons will be normal, daughters will be carriers
What are the tests of coagulation?
APTT
PT
TT
Fibrinogen level
Clotting factor assays (normal level 100%)
D-dimers - breakdown products of fibrin clot
Which tests are done to diagnose haemophilia?
Prolonged APTT
Normal PT
Low factor VIII or IX levels
<1% = severe; 1-5% = moderate; >5% = mild haemophilia
When measuring factor VIII or IX levels, what are the percentages for the three levels of severity of haemophilia?
<1% = severe 1-5% = moderate >5% = mild haemophilia
Why were high proportions of haemophiliac patients getting AIDS?
the treatments of these patients with infected with the clotting factors of infected blood products
What is the main treatment for severe haemophilia?
prophylactic doses of their missing clotting factors once or twice a week to prevent bleeding
Describe the von Villebrand disease genetically
Autosomal dominant
What are the effects of von Villebrand disease?
Mucocutaneous bleeds
nosebleeds
menorrhagia
What tests are used to diagnose von Villebrand disease?
Prolonged APTT Normal PT Low vWF antigen level and/or vWF function (von Villebrand factor) Low factor VIII level Prolonged bleeding time Defective platelet function
What factors does Prolonged APTT test for to take a measure of how long it takes for the placements clot?
tests factors VIII, IX, XI, XII in the intrinsic pathway
How is von Villebrand disease treated?
desmopressin (DDAVP)
anti-fibrinolytics
plasma products
How does desmopressin (DDAVP) work?
stimulates the release of VWF from the endothelial cells where it is stored
What are the acquired disorders of coagulation / haemophilia?
Liver disease
Vitamin K deficiency
Disseminated intravascular coagulation (DIC)
How does liver disease lead to haemophilia?
the liver is the site of synthesis for clotting factors
Deficient synthesis in the liver because of living disease will lead to impaired platelet function and fibrinolysis
Under what circumstances can infants develop acquired haemophilia?
if they don’t receive vitamin K at birth
if they have jaundrice, malabsorption
How does Disseminated intravascular coagulation (DIC) lead to haemophilia?
Release of pro-coagulant material into circulation
Results in consumption of clotting factors
Causes both bleeding and thrombosis to occur
What age groups does Meningococcal DIC affect?
mainly in children or sometimes adults
What happens when the clotting cascade is overactivated in Meningococcal DIC?
leads to disseminate intravenous coagulation
What is the cause of thrombosis or bleeding risk in Meningococcal DIC?
when all the clotting factors are used up = acquired coagulopathy
What do blood tests for Meningococcal DIC show?
prolongation of PT, APTT, TT
low fibrinogen and low platelets - everything gets used up due to the septosemic process
raised D-dimers or FDPs
What are the anticoagulant drugs that are iatrogenic causes of Meningococcal DIC when overprescribed?
Heparin c valves
DOACs
Direct thombin inhibitors (dabigatran, argatroban)
Factor Xa inhibitors (rivaroxaban, apixaban)
What condition do patients on warfarin usually get?
intracranial bleeds
GI bleeds
How are intracranial and GI bleeds caused by warfarin treated?
urgent reversal of the drug administeration
How does warfarin work?
by competing with / inhibating vitamin K
What is vitamin K required for?
the gamma-carboxylation of factors II, VII, IX, X
What groups of people have a deficiency in vitamin K and why?
jaundice people - need bile to absorb vitamin k - as vitamin K is fat soluble
babies born prematurely
What is done to try and prevent babies from being vitamin K deficient and why?
injected with vit K a few hours after birth
prevents complications - haemorrhagic disease of the newborn
What is the difference between PTT and aPTT?
THEY ARE THE SAME THING - both used to test for the same functions
BUT - in activated PTT, an activator is used that speeds up the clotting time and results in a narrower reference range
What are the factors of the intrinsic pathway?
VIII, IX, XI, XII
What does an increased PTT in a patient with a bleeding disorder indicate?
that a clotting factor may be missing or defective
What are PT blood tests used to test for?
the presence of bleeding problems
whether medicines that prevent blood clots are working
What is the difference between PTT and PT blood tests?
PT - EXtrinsic system
PTT - INtrinsic system
What is the normal PT value?
11 to 16 secs
What bacteria is responsible for septicemia?
meningococcaemia
What is sepsis caused by?
when a patient has septicemia, sometimes the body has an immune reaction to it
it releases lots of chemicals into the blood, triggering widespread inflammation that can lead to organ damage
