Cancer patients being treated with chemotherapeutic drugs designed to destroy rapidly dividing cells are monitored closely for changes in their red and white blood cell counts. Why so?
Hematopoiesis is a process involving fairly rapid cell production. Because chemothera-peutic drugs target cells exhibiting rapid turnover (rather than other specific properties of cancer cells), hemopoiesis is a target of chemotherapeutic drugs and must be carefully monitored. (p. 636)
Mary Healy, a young woman with severe vaginal bleeding is admitted to the emergency room. She is three months pregnant, and the physician is concerned about the volume of blood she is losing.
(a) What type of transfusion will be probably be given to this patient?
(b) What blood tests will be performed before starting the transfusion?
a. Mary would probably be given a whole blood transfusion. It is essential that she maintain sufficient O2-carrying capacity to serve fetal needs and blood volume to maintain circulation.
b. The blood tests that would be performed include tests for ABO and Rh group antigen and cross matching. (pp. 652–653)
Critical Thinking
Alan Forsythe, a middle-aged college professor from Boston, is in the Swiss Alps studying astronomy during his sabbatical leave. He has been there for two days and plans to stay the entire year. However, he notices that he is short of breath when he walks up steps and tires easily with any physical activity. His symptoms gradually disappear, and after two months he feels fine. Upon returning to the US, he has a complete physical exam and is told his erythrocyte count is higher than normal.
(a) Attempt to explain this finding.
(b) Will his RBC’s remain at this high level? Why or why not?
a. Polycythemia accounts for his higher erythrocyte count because of the need to produce more RBCs to increase his O2 binding and transport ability in the high-altitude (thinner air) environment of the Alps. Enhanced production of RBCs was prompted by an increased production of erythropoietin, in response to chronic hypoxia.
b. His RBC count will, with time, return to normal. This is because the conditions at lower altitudes make it easier for oxygen to enter the blood, resulting in elevated plasma O2. Elevated plasma O2, coupled with the high number of RBCs, inhibits erythropoietin production by the kidneys. (p. 640)
Critical Thinking
A young child is diagnosed as having acute lymphocytic leukemia. Her parents cannot understand why infection is a major problem for Janie when her WBC count is so high.
Can you provide an explanation for Janie’s parents?
As a consequence of acute lymphocytic anemia, Janie’s leukocytes are immature or abnormal and are incapable of defending her body in the usual way. (p. 639)
Critical Thinking
Mrs. Ryan, a middle-aged woman, appears at the clinic complaining of multiple small hemorrhagic spots in her skin and severe nosebleeds. While taking her history, the nurse notes that Mrs. Ryan works as a rubber glue applicator at a local factory. Rubber glue contains benzene, which is known to be toxic to red bone marrow.
Using your knowledge of physiology, explain the connection between the bleeding problems and benzene.
Red bone marrow is the site of hemopoiesis, and if it is destroyed by benzene, hemocy-toblasts will not be produced, which will reduce the production of megakaryocytes (the progenitor cells of platelets, which are involved in clotting). (p. 636)
Critical Thinking
A reticulocyte count indicated that 5% of Tyler’s red blood cells were reticulocytes. His blood test also indicated he had polycythemia and a hematocrit of 65%.
Explain the connection between these three facts.
Tyler is turning out a high rate of reticulocytes (immature red blood cells), which accounts for his polycythemia and high hematocrit. (p. 636)
Critical Thinking
In 1998, the US Food and Drug Administration approved the nation’s first commercial surgical glue to control bleeding during certain surgeries. This glue called Tisseel forms a flexible mesh over an oozing blood vessel to help stem bleeding within five minutes. This sealant is made from two blood proteins that naturally cause blood to clot when they react together.
Name these two proteins
Based on the description of the roles of various proteins in the clotting process, the two blood proteins are thrombin and fibrinogen. (p. 648)
Critical Thinking
Jenny, a healthy young woman, had a battery of tests during a physical for a new job. Her RBC count was at the higher end of normal range, but four weeks later it was substantially elevated beyond that. When asked if the circumstances had changed in her life she admitted to taking up smoking.
How might her new habit explain her higher RBC count?
An elevated RBC count could be related to smoking, due to the frequent hypoxia that results from inhalation of oxygen-poor cigarette smoke. Chronic hypoxia is a stimulus for the release of erythropoietin, which promotes RBC formation. (p. 640)
Critical Thinking
Mr Chu has been scheduled for surgery to have his arthritic hip replaced. His surgeon tells him he must switch from aspirin to acetaminophen for pain control before his surgery.
Why?
Aspirin is a mild anticoagulant, which could cause excessive bleeding during or after surgery. (p. 650)