Blood Coagulation and Bleeding Disorders Flashcards
% make up of blood (plasma, WBC/ platelts, RBCs)
plasma: 55%
RBCs: 45%
WBC and platelets:
stages when there is damage to blood vessel wall (see diagrams) 7
- collagen and tissue factor TF exposed
- von willebrand factor VWF binds collagen
- platelets adhere to VWF-collagen
- platelets are activated (PRIMARY HAEMOSTASIS, PLATELET PLUG)
- TF and platelets activate clotting factors to make thrombin (CLOTTING CASCADE)
- thrombin converts fibrinogen to fibrin clot
- stable fibrin-platelet clot is formed
consequences of failure of haemostasis
inc bleeding
2 things that increase bleeding in mouth
- oral mucosa highly vascular
- saliva contains fibrinolytic substances and rich in bacteria
2 categories of things that can go wrong with haemostasis
- abnormal primary haemostasis (less platelet number/ function or less VWF)
- abnormal coagulation pathway (reduced clotting factors)
- identify causes of pictures*
a. what are petechiae
b. what is epistaxis
c. what is menorrhagia
a. small bruises
b. nose bleeds
c. abnormally heavy periods
p= primary haemostasis disorders c= coagulation factor disorders write p, c or both for these symptoms: a. bleeds in to joints b. soft tissue joints c. petechiae/ bruising d. epistaxis e. gum bleeding f. menorrhagia g. GI/ CNS
a. bleeds in to joints: c
b. soft tissue joints: c
c. petechiae/ bruising: p
d. epistaxis: p
e. gum bleeding:p
f. menorrhagia: p
g. GI/ CNS: c+p
3 parts of clinical evaluation to identify patients with abnormal haemostasis
- bleeding history after previous dental tx/ surgery/ minor trauma
- general medical history
- drug history (anticoagulants)
2 lab tests used to identify patients with abnormal haemostasis
- full blood count (counts platelets BUT not function- could miss some abnormalities)
- clotting screen (proothrombin time PT and aPTT)
does abnormality inc or dec PT and aPTT
increase
what is INR ratio of
patient PT to normal PT
name 2 heritable disorders
- von willebrand disease
- haemophilia A (factor VIII deficiency)
name 4 acquired disorders
- reduced platelet number (eg AITP, leukaemia)
- liver disease
- kidney disease
- anti-coagulant/ antiplatelet drugs
inheritance ofVWs disease
autosomal –> 1/100, M=F
treatment of VWs disease 3
-desmopressin (DDAVP)- releases endogenous fVIII/ VWF. sc or in
-tranexamic acid- reduces clot breakdown. po or mouthwash
exceptional circumstances: VWF transfusion
usual cause and explain immune thrombocytopenia
idiopathic or 2’ eg infection
autoantibodies attack platelets –> reduced platelet number –> abnormal primary haemostasis
common symptom of immune thrombocytopenia
skin purpura on lower limbs
what causes a purpura
capillary-level bleed in to skin
2 categories of treatment of immune thrombocytopenia and examples
- long term disease control (immunosuppression with steroids/ iv immunoglobulin, splenectomy)
- treatment of bleeding: tranexamic acid, platelet transfuion (emergencies only, will just be destroyed by autoantibodies)
how does immunoglobulin work to treat immune thrombocytopenia
coats reticuloendothelial cells in spleen –> prevents binding and destruction of platelets
effects of liver disease in blood coagulation
EVERYTHING:
- reduced production of all coagulation factors
- low platelet count
- abnormal primary haemostasis
- abnormal coagulation pathway
treatment of bleeding in liver disease 3
-tranexamic acid
-vit K
fresh frozen plasma for emergency tx of bleeding
2 types of drugs that affect haemostasis and how they work and diseases they’re used with
PLATELETS-ARTERIES, COAG-VEINS
- anti-platelets: inhibit arterial thrombosis (IHD, PVD, CD)
- anti-coagulants: inhibit coagulation pathway/ venous thrombosis (DVT, PE, CVA in AF, CVA from mechanical heart valves, CPB
name antiplatelet types 2/ examples
- permanently inhibit platelet activation: aspirin/ clopidogrel
- unintentional platelet effects: NSAIDS, SSRIs, statins etc
how to overcome antiplatelet effect of drugs when not wanted
stop medication and wait 5-7 days for synthesis of new platelets
name main anticoagulant and how it works
warfarin
prevents synthesis of clotting factors II, VII, IX, X –> inc PT, aPTT
what is warfarin used to control
long term tx / prevention of venous and arterial thrombosis
what should INR be between
2-3
how often is INR checked
4-6 weekly
what INR is too high
5
what is LMW and unfractioned heparin used for
prevention of venous and arterial thrombosis (urgent tx and pregnancy)
how are the following administered
a. LMW heparin
b. unfractioned heparin
a. LMW heparin: subcutaneous injection
b. unfractioned heparin: IV
how are the following monitored
a. LMW heparin
b. unfractioned heparin
a. LMW heparin: does not require monitoring
b. unfractioned heparin: using aPTT
how do LMW heparin and unfractioned heparin work
inhibit coagulation factors
3 dental procedures relevant to pts with bleeding disorders
- multiple extractions
- ID block
- maxillofacial surgery
what to do differently with warfarinised pts
INR 2-3 normally fine
what to do differently for pts with inherited haemostatic disorders
discuss with haematologist and devise management plan
