14. Pathophysiology of haemostasis (2) Flashcards
Why is a history most important in a patient with a bleeding disorder?
Required to see whether these problems are inherited or acquired - is this something that they have always had or has it recently come on?
How can a clinician determine whether a bleeding disorder is inherited or acquired?
Symptom duration - recent or life-long?
Age of patient at presentation?
Family history
Current situation - can clue to possibility of acquired disease i.e. on medications?
In what conditions may a patient develop an acquired bleeding disorder?
Deficiency of vitamin K - low levels of vitamin K dependent factors (II, VII, IX, X)
Liver disease - liver is responsible for the production of vitamin K
Renal disease
Snake bite
What tests can be carried out to determine acquired haemostatic defects?
Coagulation tests
Platelet count/blood film
Fibrinolysis
Why can liver disease result in bleeding disorders?
The liver is responsible for the production of vitamin K
Hence, liver disease results in low levels of vitamin K and low levels of vitamin K dependent factors (II, VII, IX, X)
Liver disease also results in the production of abnormal fibrinogen (required for production of fibrin to clot)
Why can renal disease result in bleeding disorders?
Patient cannot clear out toxic metabolites and so this can impair production of clotting factors
What is meant by ‘disseminated intravascular coagulation’ (DIC)?
Pathological condition where an underlying disorder activates the coagulation cascade and there is nothing to check it
Leads to the formation of blood clots in many arteries of the body
Results in microvascular thrombus and tissue damage and a consumption of coagulation factors and platelets and hence increased levels of bleeding
How can DIC arise?
Infection Malignancy Shock Liver disease Transplantation Snake bite Intravascular haemolysis
How can DIC be recognised from investigations?
Low platelet count Evidence of microvascular haemolysis Prolonged APTT, PT and TT Low fibrinogen Raised FDP and D-dimer
How is DIC treated?
Must treat the underlying disorder - the prognosis is related to this underlying disorder
Blood count replacement i.e. replace the missing components in the bleeding patient - transfusion
Anticoagulants are also very commonly used
What are the main components of haemostasis and why?
Platelets - form the clot
vWF - hold the platelets together to form a plug
Tissue factor - initiates the clotting cascade
Anticoagulent proteins - to ensure that one massive clot is not just formed
