Henry is 77 years old and lives with his daughter and son-in-law. ...

[Coya19@aol.com]

Henry is 77 years old and lives with his daughter and son-in-law. He has chronic renal failure, but likes to get out whenever he can to work in his daughter's backyard garden.
 
  Over the last few months, he began to go outside less often. He said he was feeling unusually tired and he was running out of breath doing the simplest of tasks. He also said his head ached and he often felt dizzy. His daughter took him to his doctor who performed a complete physical examination and diagnosed Henry with anemia.
 
  From what you know of Henry's history, what type of anemia do you suspect he has? How would Henry's red blood cells appear on a peripheral blood smear?
 
  What is the physiological basis that would explain why Henry's anemia would cause him to have the symptoms he is experiencing?
 
  Predict the cellular adaptations erythrocytes undergo when chronic hypoxia is present. How would this be evident on an oxygen-hemoglobin dissociation curve?

Question 2

Bertha is 81 years old and was admitted to hospital after contracting community-acquired pneumonia. She had been bedridden for 3 days, so her nurse arranged for a physiotherapist to assist her out of bed to help her slowly regain her mobility.
 
  Bertha decided not to wait for the physiotherapist, and after arising in the morning, she eased herself out of the bed and stood up. Suddenly Bertha's vision dimmed and she felt light-headed and dizzy. A passing nurse saw her fall back to the bed and rushed to help her. The nurse comforted Bertha, and then suspecting orthostatic hypotension, went to find a sphygmomanometer to check her blood pressure.
 
  Prolonged bed rest decreases plasma levels and vasomotor tone, which can both lead to orthostatic hypotension. How do changes in vascular resistance and radius affect blood flow? Assuming Bertha is otherwise healthy, how does her heart activity change in an attempt to compensate for the orthostatic hypotension she experienced?
 
  Considering the venous circulation, how is blood from the lower extremities returned to the heart?
 
  Why did Bertha's capillary fluid pressure (or hydrostatic pressure) change when she moved from a lying to standing position?

[flexer1n1]

Answer to Question 1

Henry has anemia of deficient red blood cell production as a result of his chronic renal failure (or chronic disease anemia). The chronic renal failure causes a reduction in erythropoietin production. Furthermore, increased serum levels of nitrogen and uremic toxins interfere with erythropoietin activity and red blood cell survival. On a smear, the red blood cells would appear normocytic and normochromic.

Chronic disease anemia involves a decrease in circulating erythrocytes and oxygen-carrying capacity of the blood. As a result, tissue hypoxia ensues and creates the symptoms of weakness, fatigue, and dyspnea. Central nervous system hypoxia leads to headaches and dizziness. In the elderly individual, cognitive impairment and depression are also indications of hypoxic change in the central nervous system.

There is an increased production of 2,3-DPG by erythrocytes in an attempt to lower hemoglobin affinity with oxygen. The result is that oxygen is more readily released by red blood cells at areas where it is needed most. This is evidenced by a shift to the right on the oxygen-hemoglobin dissociation curve.

Answer to Question 2

According to the law of Laplace, the greater the pressure change between two ends of a vessel, the greater the blood flow. A weaker pressure differential decreases blood flow. A very small change in vessel radius has a powerful effect on the movement of blood, and the relationship is inversely proportional: a decrease in vessel radius increases blood flow, and an increased radius decreases flow. Because blood flow is determined by PVR and CO, Bertha's heart rate (and therefore CO) would increase to compensate for the hypotension she experienced when she stood up.

Venous circulation is maintained by a variety of mechanisms. Valves exist in the veins of the lower extremities to resist retrograde flow and pooling. Skeletal muscle lies in close proximity to veins and helps to move venous blood. Finally, low intrathoracic and intra-abdominal pressures assist to pull venous blood from the lower extremities to the heart.

Capillary fluid pressure (or hydrostatic pressure) is influenced by gravity and is increased by the weight of blood in the vascular column during standing. When recumbent, blood vessels lie at the level of the heart, and hydrostatic pressure is therefore low.