Coagulation- A surgical perspective Flashcards
the 3 phases of normal hemostasis:
- vascular phase
- platelet plug
- coagulation phase
What is the vascular phase of hemostasis?
vasconstriction occurs
-diminish the blood flow to the damaged area
What happens during the platelet phase of hemostasis?
- exposed collagen binds and activates platelets
- release of platelet factors
- attract more platelets
- aggregate into platelet plug
What do the platelets bind to at the site of injury?
collagen
What causes platelets to change their shape?
presence of fibrinogen
What does the conformational change of platelets allow?
aggregation to form a primary platelet plug
which pathway is longer (extrinsic or intrinsic)?
intrinsic
What factor is the beginning of the common pathway?
Factor X
Common pathway of coagulation:
Factor X
-prothrombin to thrombin
fibrinogen to fibrin
What does fibrin do to the platelet plug?
allows for tight binding and forms a more stable hemostatic plug
What is clot dissolution?
partial of complete dissolution of a hemostatic plug by plasma
What are some factors that affect normal hemostasis mechanism?
-vessel wall integrity
-adequate number of platelets
-proper functioning platelets
-adequate levels of clotting factors
-proper function of fibrinolytic pathway
What are common lab tests done to test hemostasis?
-platelet count (in a CBC)
-bleeding time
-coagulation profile
* PT- prothrombin time
* APTT- activated partial thromboplastin time
* INR- international normalized ratio
What is a platelet function test?
test done to identify platelet dysfunction
-may be recommended for those that bruise easily, bleed excessively, or take medications that can alter platelet function
What is a clotting factor assay?
test that measures the level or functional activity of one or more coagulation factors
What is a normal platelet count?
150,000-400,000 cells/ mm
What level of platelets is considered thrombocytopenia?
100,000-140,000
What level of platelets is considered mild thrombocytopenia?
50,000-100,000
What level of platelets is consider severe thrombocytopenia?
<50,000
What level of platelets is considered spontaneous bleeding?
<20,000
What is a normal bleeding time?
2-9 minutes
What is a bleeding time considered to have platelet dysfunction?
9-15 minutes
What does a prothrombin time test measure?
effectiveness of extrinsic pathway
-conversion of VII to VIIa
What is a normal prothrombin time?
12-13 seconds
Common causes of prolonged prothrombin time:
-warfarin use
-vitamin K deficiency
-liver disease
What does an activated partial prothrombin time test measure?
effectiveness of intrinsic and common pathway
-more sensitive than PTT
What is a normal aPTT result?
30-40 seconds
What aPTT level signifies spontaneous bleeding?
more than 70 seconds
What are common causes of prolonged aPTT?
-congenital deficiency of intrinsic clotting factors
-von Willebrand disease
-liver cirrhosis
-Vitamin K deficiency
-heparin therapy
How to calculate international normalized ratio:
What is a normal INR?
0.8-1.2
What is an INR of someone on anticoagulants?
2-3.5
Why would an INR range of 2-3 be ideal?
if the patient has a history of
-atrial fibrillation
-ischemic stroke
-systemic embolism
-mitral stenosis
-planned cardioversion
-following open heart surgery
Are acquired or congenital bleeding disorders more common?
acquried
What three congenital bleeding disorders account for 90% of congenital bleeding disorders?
Hemophilia A and B and Von Willebrand’s disease
What causes hemophilia A?
deficiency in clotting factor VIII
What causes hemophilia B?
deficiency in clotting factor IX
Prevalence of Hemophilia A
1 in 10,000
Prevalence of Hemophilia B
1 in 50,000
How is hemophilia inherited?
x linked recessive
-25% have no family history?? weirddddd
Does hemophilia affect males or females more?
males
Three levels of hemophilia:
mild
moderate
severe
Characteristics of Mild hemophilia:
-only have issues have serious injury, trauma, or surgery
-first episode may not occur until adulthood
Characteristics of Moderate hemophilia:
-15% of hemophilia population
-tend to have bleeding episodes after injury
-may have ‘spontaneous bleeding episodes’
Characteristics of Severe hemophilia:
60% of hemophilia population
-frequent spontaneous bleeding episodes
-often in the joints and muscles
Treatment for patients with hemophilia:
A- cyroprecipitate and factor VIII concentrate
B- factor IX concentrate
What is cyroprecipitate?
only adequate fibrinogen concentrate available for intravenous use
-made from plasma and contains fibrinogen, von Willebrand factor, factor VIII, factor XIII, and fibronectin
What type of anesthesia should be avoided in patients with hemophilia?
block local anesthetic
in mild hemophilia, what can be used to increase factor VIII coagulant activity?
vasopressin analogue- desmopressin
What can be used to extract teeth in patients with hemophilia?
epsilon-aminocaproic acid or tranexamic acid
what does epsilon-aminocaproic acid and tranexamic acid do?
inhibit fibrinolysis
What is von Willebrand disease?
bleeding disorder where von Willebrand factor is missing or does not function properly
-does not allow proper platelet interactions
von Willebrand disease type 1
shortage of von Willebrand factor
-mild
-70-80% of cases
-most common
von Willebrand disease type 2
flawed von Willebrand factor
-usually mild
-2 types 2A and 2B
-20-25% of cases
von Willebrand disease type 3
complete lack of von Willebrand factor
-more severe
-very rare
-1 in 500,000 people
Are there blood tests to determine von Willebrand disease?
yes
-bleeding time
-VWF activity level
-VWF antigen levels
-genetic testing
Why is demsopressin given to those with VWD?
increases production of von willebrand factor
What type of von Willebrand disease should not be treated with desmopression?
type 2B
What can cause thrombocytopenia ?
decreased platelet production or increased platelet destruction
What causes decreased platelet production?
myelosuppresion due to antieoplastic agents as well as radiation treatment
Local measures to achieve hemostasis
-suture the wound
-pressure with oral packs
What can cause acquired bleeding disorders?
drugs, alcohol, virus induced liver disease, vitamin K deficiency from antibiotic use, acquired platelet function defect, multiple myeloma, oral anticoagulants, antiplatelets, leukemia, chemotherapy, HIV patients, and kidney failure
What needs to be done to treat a patient with a bleeding disorder?
-medical consult
-assess lab test results
-refer to oral surgery
-stop using anticoagulants/antiplatelets prior to surgery
-bridging therapy
-local measures to control bleeding
Examples of anti platelet medications
-plavix
-aspirin
-effient
Examples of anticogulant medication?
-warfarin
-lovenox
-pradaxa
-eliquis
-xarelto
Can a dentist tell a patient to stop taking their antiplatelet/anticoagulants?
no
-the prescribing physician is in charge of these decisions
What can be used to irrigation of wound for those with bleeding disorders ?
tranexamic acid mouth wash
