Laboratory Evaluation of Hemostasis Flashcards
Hemostasis is dependent upon which factors?
5
- Vessel Wall Integrity
- Adequate Numbers of Platelets
- Proper Functioning Platelets
- Adequate Levels of Clotting Factors
- Proper Function of Fibrinolytic Pathway
Which three ways does the body achieve and make a stable hemostatic plug?3
- Blood Vessel Constriction (vasoconstriction)
- Platelet Aggregation (ahesion and activation too)
- Coagulation Cascade
What lab tests do we want to do for evaluation of hemostasis?
5
PLATELET COUNT (plt) BLEEDING TIME (BT) PROTHROMBIN TIME (PT/INR) ACTIVATED PARTIAL THROMBOPLASTIN TIME (aPTT) THROMBIN TIME (TT)
What is the platelet count measuring?
What tube is it collected in?
The number of platelets per cubic millimeter of whole blood
Its on the CBC
Lavender top (EDTA)
What are the different ways to count platelets?
- Manual platelet counting
- Automated cell counter methods
- Optical counting methods
- Flow cytometric methods - Platelet count ratio method for platelet function testing
Whats a normal platelet count?
What platelet count is considered thrombocytopenia?
What is considered mild thrombocytopenia?
What is consodered severe thrombocytopenia?
Adults: 150,000-450,000/mm3
Peds: 150,000-350,000 /mm3
Below 150,000
50,000-99,999 Mild
At what platelet count do you start experiencing symtpoms?
What count is potentially life threatening?
At what count are you at high risk for spontaneous bleeding and intracranial hemorrhage?
50,000 - 20,000: first symptoms
20,000-10,000
Below 10,000
If you have a high platelet count what could be happening?
5
- Acute phase reaction (most prominent is C reaction protein CRP)
- Early CML
- Essential thrombocytosis
- Polycythemia vera
- Post splenectomy (very common)
If you have a low platelet count what could be happening?
7
- DIC (sepsis and trauma)
- Hemolytic anemia
- Hypersplenism
- ITP
- Leukemia
- Prosthetic heart valve
- Recent transfusion
What does bleeding time measure?
Whats it a screening test for?
What is it useful for and what is it not useful for?
A measurement of the time required for bleeding from a superficial puncture to stop.
Platelet funtion
Not a reliable predictor of post-op bleeding
Useful in the diagnosis of Von Willebrand’s
What does bleeding time really measure?
how well platelets interact with blood vessel walls to form blood clots.
How often should we blot in a bleeding time test?
Blot incision q 30 seconds until bleeding stops
What should we avoid 2 weeks prior to a bleeding time test?
Whats the normal bleeding time?
Avoid aspirin 2 weeks prior to test
Normal: 3-8 minutes
What could indicate a high bleeding time?
7
- Platelet dysfunction
- DIC (but probably won’t do the test here)
- Leukemia
- Liver disease
- Thrombocytopenia
- Von Willebrand’s
- Vasculitis
What does prothrombin time measure?
Measures vitamin K dependent clotting ability, and extrinsic pathway
What is PT used to screen and monitor?
2
Used to screen for bleeding disorders
Used to monitor patients on warfarin
What is prothrombin time lab filled in and how do we need to fill it?
Light blue top (citrate)
Fill tube completely
Avoid prolonged tourniquet use (hemoconcentration, hemolysis, lactic acid buildup. no more than 1 minute)
Correct ratio of blood to citrate is critical
prolonged storage of plasma shortens PT
Whats a normal PT?
For DVT prophylaxis what do we want the INR to be?
For Mechanical valve and anti-phospholipid antibody syndrome what do we want the INR at?
What should we treat pregnant women with?
What should AFIB pts INR be at?
Adults PT/INR: 11-13 seconds 1-2
DVT prophylaxis (INR): 2-3
2.5-3.5
(can cause a lot of complications in pregnancy. treat with warfarin or aspirin but in pregnant women go for heparin)
2-3
What conditions would be indicated with a high PT/INR?
5
- Anti-phospholipid antibody syndrome
- DIC
- Liver disease
- Vitamin K deficiency
- Factor II, V, VII, or X deficiency
What is PTT?
What does it measure?
Which is generally measuring what?
ACTIVATED PARTIAL THROMBOPLASTIN TIME
A measure of the time taken for a clot to form in citrated blood following the addition of calcium and a phospholipid platelet substitute.
Effectiveness of the intrinsic pathway
What is PTT used to work up, monitor, and screen?
3
Used to work up bleeding disorders
Used to monitor heparin therapy
Screen for lupus anticoagulant
What do we collect PTT in and what do we need to remember to do while filling it?
Light blue top (citrate) Fill tube completely Avoid prolonged tourniquet use Correct ratio of blood to citrate is critical prolonged storage of plasma shortens PTT
Whats the normal PTT in adults?
What about on antocoagulation therapy?
What is the normal PTT in peds?
Newborns:
1-6 yrs old:
Adults: 25-35 secs
On anticoagulant therapy: 1.5-2.5 x the control value
Newborn: 31-54 secs
1-6 yrs: 24-36
What conditions would be indicated in a high PTT?
5
Hemophilia DIC Liver disease Vitamin K deficiency Heparin therapy
What lab is associated with the intrinsic pathway and what factors is it associated with?
4
Think PTT (partial thromboplastin time) Think VIII, IX, XI, and XII
What lab is associated with the extrinsic pathway and what factors is it associated with?2
Think PT(INR) (prothrombin time) Think II and VII
What factors are vitamin K dependent?
Factors VII, X, and prothrombin (Factor II)
What is thrombin time measuring?
Whats the normal thrombin time?
The rate of conversion of fibrinogen to fibrin in the final stage of coagulation as measured by the addition of thrombin to citrated blood.
Fibrinolytic pathway
15-20 secs
What do we collect thrombin time in?
Light blue top (citrate)
Fill tube completely
Avoid prolonged tourniquet use
Correct ratio of blood to citrate is critical
What would indicate a high thrombn time?
6
- DIC
- Liver disease
- Dysfibrinogenemia (abnirmal fibrinogen funtion- could cause
- bleeding or thrombosis)
- Paraprotienemia-monoclonal gammapathy
- Uremia
What would a low thrombin time?
2
Erythrocytosis
Dysfibrinogenemia
Indications to order coagulation studies ?
5
- Work-up of suspected bleeding disorders
- Screening before major surgery, part of pre-op evaluation
- Monitoring of medications (warfarin, heparin)
- Monitoring of bleeding disorders
- Monitoring of liver disease
What pathway are we monitoring with heparin?
intrinsic/pt
What pathway are we monitoring with warfarin?
extrinsic and ptt
Whatdo we really want to know when someone presents with abnormal bleeding?
What is the bleeding site?
Multiple vs single sites Joints Deep muscle Superficial cut Skin or mucus membrane Epistaxis Gingivae Urine, GI tract, Menstrual
Platelet/cellular deficiency or malfunction will show bleeding where?
5
What will be normal and abnormal?
2
Gum bleeding Easy bruising Epistaxis Petechiae Prolonged bleeding from minor cuts
Abnormal bleeding time, normal PT/PTT
Factor deficiencies (hemophilia)
will show bleeding where?
5
What will normal and abnormal in the lab tests?
2
Hemarthroses Easy bruising Delayed bleeding Postop hemorrhage Muscle hematoma
Normal bleeding time, abnormal PTT
