7. Von Willebrand Factor
● Quantitative (types 1 and 3) and qualitative
(types 2A, 2B, 2M, and 2N) abnormalities of
vWF result in vWD.
● The 2 main functions of vWF are
– 1) to mediate platelet adhesion and aggregation
and
– 2) to act as a carrier protein for factor VIII,
protecting it from proteolytic inactivation
8. Disorders of Platelet Adhesion
Von Willebrand disease
Autosomal dominant
Spontaneous bleeding from mucous membranes, prolonged
bleeding from wounds, and menorrhagia in young females.
Bleeding may be exacerbated by aspirin or NSAID use
Hemarthrosis is uncommon.
Lab studies: Type 1 - a mild to moderate reduction in vWF
antigen (vWF:Ag) and activity
Type 3 - vWF is absent.
Healthy people with blood group O have vWF levels that are 25%
to 30% lower than in people with blood groups A, B or AB; thus,
they may receive a misdiagnosis of vWD. Therefore, ABO typing
should be part of the initial testing.
Normal platelet count, Normal PT,
Prolonged PTT, Prolonged bleeding time
9. Diagnostic: Abnormal platelet response to ristocetin
Normalizes after addition of normal plasma
Treatment: Desmopressin (ADH Analog)
Intravenous infusion of 0.3 mcg/kg body weight releases vWF
from its storage sites; levels should be measured 60 minutes after infusion.
Side effects include facial flushing, headache, mild decrease in blood pressure,
mild tachycardia, and hyponatremia. Repeated doses at intervals shorter than 24
hours may result in a decrease or loss of response (tachyphylaxis) and syndrome
of inappropriate antidiuresis (SIAD), leading to hyponatremia and seizures.
Type 3 vWF: purified plasma-derived vWF concentrates are the therapy of
choice
10.
Bernard-Soulier syndrome
Autosomal recessive
Lack of GpIb receptor.
Labs: Prolonged Bleeding Time, Thrombocytopenia
Abnormal ristocetin cofactor assay
Not correctable with normal plasma infusion
11. Platelet Aggregation
ADP and Thromboxane A2
Insertion of glycoprotein IIb/IIIa (GpIIb/GpIIIa)
receptors on the platelet surface.
Platelets bind to each other by binding to
fibrinogen using GPIIb-IIIa
12. Disorders of Platelet Aggregation
Uremia or Renal Failure
Accumulation of toxic products
Inhibition of platelet phospholipids
Prolonged Bleeding Time
Treatment: Dialysis & Desmopressin acetate
Glanzmann disease
Autosomal recessive
Gp IIb/IIIa receptor deficiency
Prolonged BT
13. Coagulation Cascade
Two Pathways
Extrinsic Pathway – Defect in PT
Intrinsic Pathway – Defect in PTT (25 to 40
seconds)
Activation of Factor II to IIa and Fibrinogen to Fibrin
Extrinsic Pathway
Trauma to the endothelium
Tissue Factor (factor III) and tissue phospholipids.
TF-FVII complex
Co-factors: Vitamin K, Calcium
14.
15.
Intrinsic Pathway
Activation of Factor XII
Collagen
Key Points:
Vitamin K dependent factors: II, VII, IX, X, Protein C
& S
All Vitamin K dependent factors require Calcium
Clinical: Neonates require Vitamin K
Constant activation of the coagulation system leads
to deficiency in I, II, V and VIII. (sepsis, DIC)
16. Anticoagulant System
Regulate clot formation
Two systems
Protein C & S
Vit. K dependent
Protein C activated by thrombomodulin.
Inactivates Factors Va, VIIIa
Protein S – cofactor for activated Protein C
Antithrombin
Serine protease inhibitor
Inhibits Factors Iia, VIIa, Ixa, Xa, Xia, Xiia
Heparin*
18. Lab Report of CBC
Hb – Concentration of Hb in the blood
Hct – Percentage Value of volume of RBCs in
the blood
MCV - average RBC volume; normal range is
80 to 100 fL
RDW - measure of the variation in width of
RBCs
MCHC – average concentration of Hb in RBCs.
Reticulocyte count - decreased RBC
production or decreased survival of RBCs
Corrected reticulocyte count = (measured
Hct/45) × reticulocyte count.
19. Approach to Anemia
Determine whether patient is anemic by looking
at the Hb.
Classify the anemia as microcytic, normocytic,
or macrocytic by looking at the MCV.
Determine whether the bone marrow is
compensating appropriately by looking at the
reticulocyte count (use correction formulas if
necessary).
23. Microcytic Anemia
Acquired – Iron Deficiency Anemia
Functional Iron – Hemoglobin, myoglobin,
Catalase and Cytochrome
Ferritin
Hemosiderin
Ferroportin
inhibited by hepcidin
Retention of Iron inside cells
Transferrin
TIBC – 300microgm/L
Saturation – 33%
24.
Iron Deficiency Anemia
Dietary deficiency - elderly populations,
children,poor, pregnant women
Decreased absorption
Generalized malabsorption
Post-gastrectomy
Chronic Blood loss
25. Stages of IDA
Decreased storage iron leading to Decreased
serum ferritin.
Decreased circulating iron.
Formation of microcytic/hypochromic anemia.
26. Pathophysiology of IDA
Clinical signs of IDA include the following:
Pallor, fatigue, shortness of breath
Glossitis—inflammation of the tongue
Koilonychia—concave or spoon-shaped nails
Pica—obsessive craving for nonnutritional
materials (e.g., ice, dirt)
Plummer Vinson Syndrome
27.
28.
29. Laboratory
Increased RDW
Hb, Hct, and MCV are decreased
Serum iron and Ferritin levels will be decreased
Iron saturation will be decreased
TIBC will be increased
Increased free erythrocyte protoporphyrin
(FEP)
31. Anemia of Chronic Disease
Iron being trapped in bone marrow
macrophages
Most common anemia in hospitalized patients
Chronic illness leads to continued released of
cytokines (Il-6)
IL-6 signals the liver to release Hepcidin
Increased retention of iron in cells