Exam #2: Hemodynamics III Flashcards
What is the difference between a PT, PTT, & INR?
PT= Prothrombin time, extrinsic pathway, warfarin
INR= International Normalized Ratio–a way to compensate for differences in tissue factor; normally you’ll order a PT/INR
PTT= Partial thromboplastin time, intrinsic pathway, heparin
*****Note that a good PT/INR when you want a patient to be anticoagulated is 2-3
How do you figure out if a person has a factor deficiency or an inhibitor?
- Make a 50:50 mixture of patient plasma and normal plasma
- Factor= clotting will occur
- Inhibitor= no clotting
What are the does dependent effects of Heparin and Warfarin?
- Low dose heparin= PTT prolonged
- Low dose warfarin= PT prolonged
BOTH will be prolonged at HIGH doses
What are the special considerations regarding anticoagulation and the elderly?
- Increased age= increased sensitivity
- Increased drug interactions
Possibly increased bleeding independent of other factors
What are the contraindications to warfarin therapy?
1) Pregnancy
2) Risk of hemorrhage>benefit
E.g.
- uncontrolled alcohol or drug abuse
- unsupervised dementia/ psychosis
What are the signs of warfarin overdose?
Any unusual bleeding
- Melena or hematochezia
- Hematuria
- Excessive menstrual bleeding
- Bruising
- Excessive nosebleeds or bleeding gums
- Persistent bleeding from superficial injuries
- Bleeding from a tumor, ulcer, or other lesion
What is Warfarin Necrosis?
This is a condition seen 3-5 days s/p warfarin therapy initiation; patients develop skin lesions that progress from localized pain and erythema to a necrotic eschar.
What causes Warfarin Necrosis?
- Warfarin Necrosis is most commonly seen in patients with low levels of Protein C
- Protein C normally has anticoagulant & fibrinolytic activity
- Synthesis of Protein C is Vitamin K dependent
- Warfarin causes depletion of already low Protein C, leading to an acutely hypercoabuable state prior to anticoagulation
- Thrombosis occurs in dermal vessels
*****Because of this, patients should be started on Heparin & then given warfarin i.e. Lovenox (low molecular weight heparin)
What is Heparin-induced Thrombocytopenia?
This is a potential complication of heparin therapy that leads to a prothromic state, even in the face of thrombocytopenia & heparin.
- More common with unfractionated heparin than low molecular weight heparin
- Immune system forms antibodies against heparin and Platelet Factor 4 (the receptor for heparin on platelets)/ Heparin complexes, which has three effects:
1) Platelet activation
2) Platelet aggregation
3) Platelet consumption
Thus, a thrombocytopenia (low platelets) develops from platelet consumption & a prothrombic state is developed . Can lead to extensive venous thrombosis, venous limb gangrene, and secondary skin ulcer
What are the platelet abnormalities?
1) Bernard-Soulier Disease
2) Glanzmann’s Thromboasthenia
3) Thrombotic Thryomctopenic Purpura (TTP)
4) Idiopathic Thrombocytopenic Purpura
5) Aplastic Anemia–Pancytopenia
What are the coagulopathies?
Von Willebrand’s Disease
- Deficiency in vWF in the ECM such that platelet binding by GpIb is prevented
*Mom
What is Bernard-Soulier Disease?
This is an autosomal recessive disorder caused by a defect in platelet adhesion, specifically, glycoprotein Ib.
- This is the glycoprotein on platelets that binds to vWF in the ECM
What is Glanzmann’s Thrombasthenia?
This is a defect in platelet aggregation caused specifically by a defect in glycoprotein IIb & IIIa.
- I.e. this disease prevents fibrinogen cross-bridging & platelet aggregation
What is Thrombotic Thrombocytopenic Purpura (TTP)?
This is a disease caused by antibodies directed against the von Willebrand factor cleaving protease, ADAMTS-13
- Can’t split vWF & platelets
- At risk for bleeding as well as thrombi
What is Idiopathic Thrombocytopenic Purpura (ITP)?
This is a disease caused by autoantibodies to platelets
- Splenomegaly
*****Treated with thrombopoetin
