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Chapter 3. Blood

A 61-year-old woman visits her family doctor complaining of severe fatigue, which has become progressively worse over the past 6 months. She is referred to a hematologist following the results of a complete blood cell count, which shows decreased hematocrit (24%), decreased hemoglobin concentration (8 g/dL), and decreased red blood cell count 2.6 x 1012/L. The mean cell volume and reticulocyte counts are normal. Which type of anemia does the patient have?

A Macrocytic anemia (large red cells)

B Microcytic anemia (small red cells)

C Normocytic, hypoproliferative anemia

D Normocytic, hyperproliferative anemia

E No anemia is present

C. Low hemoglobin concentration and hematocrit demonstrate the presence of anemia. Mean cell volume is normal because the red blood cell count is reduced in proportion to the reduced hematocrit; therefore a normocytic anemia is present. The reticulocyte count is not increased, as would occur, for example, in hemorrhage or hemolytic disease, indicating that the anemia is hypoproliferative (low red cell production).

A 21-year-old woman returns to the United States from a student exchange visit to Australia. The morning after her flight, she is awakened because she is experiencing a pain throughout her right leg, which is of pale blue color. She is taken to the emergency department, where a clinical diagnosis determines that she has deep vein thrombosis. Which of the following laboratory findings would be consistent with this history?

A Antithrombin III defect

B Decreased hematocrit

C Decreased fibrinogen

D Decreased platelet count

E Factor VIII defect

A. The patient is likely to be in a hypercoagulable state, predisposing her to deep vein thrombosis. Defects in anticoagulants, such as antithrombin III, produce a hypercoagulable state. Decreased platelets, fibrinogen, or factor VIII all oppose coagulation; hematocrit is not directly relevant.

The addition of sodium citrate to banked blood inhibits coagulation. By what mechanism do citrate ions inhibit coagulation?

A Antagonist to adenosine diphosphate

B Antagonist to thromboxane A2

C Binds to factor VII

D Binds to factor X

E Chelates Ca2+ ions

E. Citrate ions chelate Ca2+, which is required as a cofactor for several ...

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