Coagulopathies Flashcards
What are coagulopathies
Diseases in which there is an abnormal coagulation cascade
What are the three main coagulopathies
Hemophilia
Vitamin K deficiency
Test of platelet function
Small cut to patient’s arm
Filter paper applied and removed at regular intervals until bleeding stops
Rarely done in modern era
What is this done to test
Bleeding time
Test of platelet function
Small cut to patient’s arm
Filter paper applied and removed at regular intervals until bleeding stops
Rarely done in modern era
What is this done to test
Bleeding time
Which test tests the intrinsic pathway of activating the coagulation cascade
Activated partial thromboplastin time
How is PTT done
Add plasma to (-) charge substance (silica). Silica activates factor 12 to initiate the intrinsic pathway. Record time it takes for blood to clot. Normal is about 30s
What test is the test of the extrinsic pathway
Prothrombin time
How is PT done
Add plasma you want to assess, add tissue factor. Tissue factor then initiates the extrinsic pathway and you measure the time it takes for a fibrin to clot to form. Normal is about 10s
Most labs convert the PT to an INR (international normalized ratio). INR = Patient’s PT/Control PT. Normal is 1 and therapeutic on coumadin for example is about 2-3
How is thrombin time performed
Add thrombin to sample and record the time it takes to clot
Because thrombin is very far down the cascade, the only way this test would be and normal is if there is an inhibitor of thrombin in the plasma or if the patient has a very low fibrinogen level
What is the characteristic finding when bleeding is as a result of abnormal platelets
Petechiae on the skin
Bleeding caused by abnormal platelets present with
Mucosal bleeding
Skin bleeding
Petechiae
Bleeding due to abnormal coagulation factors presents with
Joint bleeding, deep tissue bleeding
(Bleeding as a result of abnormal coagulation factors tend to be deeper)
X-linked recessive diseases
Gene mutations: Run in families, also occur de novo
Also called Christmas disease
What condition could I be
Hemophilia B
Which hemophilia is caused by a deficiency in factor VIII
Hemophilia A
Which hemophilia is caused by a deficiency in factor IX
Hemophilia B
What type of hemophilia is less common
Hemophilia B
What is the most common presentation of hemophilia
Joint bleeds
What are the presentations of hemophilia
Spontaneous or easy bruising
Recurrent joint bleeds
What is the screening for hemophilia
PTT will be prolonged because factors 8 and 9 are both part of the intrinsic pathway
PT, bleeding time, platelet count are all normal
How is hemophilia treated
Replacement factor 8 and 9
Desmopressin (dDAVP) - used in mild hemophilia A, analogue of vasopressin with no press or activity, increases vWF and factors 8 levels, releases VIII from Weibel-Palade bodies (endothelial cells), also has vasodilating properties
Aminocaproic acid- antifibrinolytic drug, inhibits plasminogen activation to plasmin thus there’s less breakdown of formed clots allowing factors 8 and 9 to work more effectively because plasmin is not breaking down whatever fibrin clots can be formed
Cryoprecipitate
What bodies are vWF and factor 8 stored in
Weibel-Palade bodies
Besides treating hemophilia, what are some other uses of the drug desmopressin
Treating:
von Wilebrand disease
Central diabetes insipidus (mimics ADH)
Bed wetting (decrease urine volume)
What are the key side effects of desmopressin
Flushing and headache
Obsolete therapy for hemophilia A
Precipitate that forms when fresh frozen plasma is thawed and is separated from plasma by centrifugation
Contains lots of factor 8 and fibrinogen
Also contains some factor 13 and vWF
Often used as a source of fibrinogen
Used in conditions like DIC and massive trauma with blood transfusions
What therapy could this be
Cryoprecipitate
What study differentiates hemophilia A from bleeding caused by coagulation factor inhibitors
Mixing study
Antibodies that are directed against the clotting factor
Inhibit activity or increase clearance of clotting factor
Inhibitors of factor 8 most common
Often occurs in association with some disorders
Can be treated with prednisone as an immunosuppressant
What could this be
Clotting factor inhibitors
What conditions are associated with clotting factor inhibitors
Malignancy
Post-partum
Autoimmune disorders
Presentations of coagulation factor inhibitors and hemophilia can be similar
True or false
True
What principle is a mixing study based on
When clotting factors are 50% of normal, you will get a normal PT or PTT level
Results in bleeding
Deficiency of vitamin-K dependent factors 2, 7, 9 and 10
What condition might this be
Vitamin K deficiency
What are the key lab findings in a vitamin K deficiency
Elevated PT/INR(because factor 7 of the extrinsic pathway will be the first to decrease or fall)
Can see elevated PTT (less sensitive)
Normal bleeding time
Which factor level would be the first to fall in a vitamin K deficiency due its relatively shorter half-life
Factor 7
Why is a dietary deficiency of vitamin K very rare
GI bacteria produce sufficient quantities of vitamin K
What are some common causes of vitamin K deficiency
Warfarin
Antibiotics (deplete GI bacteria)
Newborns (sterile GI tract)
Malabsorption (Vitamin K is fat soluble)
What is another potential cause for coagulopathies
Often treated with fresh frozen plasma (plasma which contains all clotting factors)
Blood transfusion
