Lab eval of Hemostasis Flashcards
(26 cards)
Hemostasis is dependent upon?
- vessel wall integrity
- adequate number of platelets
- proper functioning platelets
- adequate levels of clotting factors
- Proper function of firbinolytic pathway
What are the lab tests used to evaluate hemostasis?
- Platelet count (plt)
- Bleeding Time (BT)
- Prothrombin Time (PT/INR)
- Activated Partial Thromboplastin Time (aPTT)
- Thrombin Time
What is platelet count? What are the various methods for finding this value?
- number of platelets
- on CBC
- manual platelet count
- automated cell counters (Optical and flow cytometric)
What is normal platelet count? Considered Thrombocytopenia? Severe? Bleed by blink?
-150,000-400,000/mm^3: no sx
-
What conditions cause platelets to be high?
-acute phase rxn
(Group of physiological process right after onset of severe infection, trauma, inflamm processes, malignancy,
Most dramatic change in acute phase reaction–CRP levels will be high, fever, increased vascular permeability )
- early CML
- essential thrombosis
- polycythemia vera
- post splenectomy
What conditions cause platelets to be low?
- DIC
- hemolytic anemia
- Hypersplenism
- ITP
- Leukemia
- Prosthetic heart valve
- recent transfusion
What is Bleeding Time? What does it really measure?
- a measurement of the time required for bleeding from a superficial puncture to stop.
- how well platelets interact w/ blood vessel walls to form blood clots.
What screening test is used for platelet dysfunction?
-bleeding time
Bleeding time is useful in the dx of what disorder?
-dx of vonWillebrands
How to perform the bleeding time test? What a normal time?
- puncture forearm making a 5mmx1mm deep cut
- blot incision q 30seconds until bleeding stops
normal time is 3-8mins
What conditions cause bleeding time to be high?
- platelet dysfunction
- DIC
- leukemia
- liver disease
- thrombocytopenia
- vonWillebrands
- Vasculitis
Prothrombin Time measures what?
When is this commonly used?
Vit K dependent clotting ability and the extrinsic pathway
- to screen for bleeding disorders
- to monitor warfarin
*INR has been introduced to reduce inter lab variabliity in reporting PT
PT synonyms
PT/INR
INR
Protime
What are some of the PT/INR values?
- normal
- DVT prophylaxis
- Mechanical Valve
- Anti-phosphoplipid aby syndrome
Normal Adult: 11-13 secs 1-2
DVT prophylaxis INR: 2-3
Mechanical Valve and Anti-phospholipid aby syndrome INR: 2.5-3.5
Reasons for High PT
anti-phospholipid aby syndrome
DIC
Liver Disease
Vit K deficiency
Factor II, V, VII, or X deficiency
What is Partial Thromboplastin Time?
-measure of the time taken for a clot to form in citrated blood following addition of calcium and a phospholipid platelet substitute.
PTT mesaures the effectiveness of which pathway? Used to monitor which type of theapy?
- Intrinsic
- Heparin
What are some of the values of PTT?
- normal
- pt on anti-coagulation therapy
- peds
Normal: 25-35secs
*on anticoagulant therapy: 1.5-2.5x the control value
Peds:
Newborns: 31-54sec
1-6years: 24-36sec
When would there be high levels of PTT?
- Hemophilia
- DIC
- Liver Disease
- Vit K
- Heparin Therapy
What lab test is ordered and what drug does this monitor when looking at the intrinsic pathway? Extrinsic?
- Intrinsic pathway, order PTT, monitors heparin therapy
- Extrinsic pathway, order PT, monitors warfarin therapy
Which factors in the coagulation cascade are vit K dependent?
-VII, X, and prothrombin (II) are vit. k dependent and are altered by warfarin.
What is thrombin time? Whats a normal time?
- the rate of conversion of fibrinogen to fibrin
- 15-20sec
What are some disorders of high Thrombin Time?
- DIC
- Liver Disease
- Dysfibrinogenemia
- Paraproteinemia
- Uremia
What are some disorders of low thrombin time?
- erythrocytosis
- dysfibrinogenemia
