Chapter 13: Alterations in Oxygen Transport

What are the functions of RBCs?

* Transport oxygen to tissues
* Remove carbon dioxide from the tissues
* Buffer blood pH (contain carbonic anhydrase)

How are RBCs produced?

Through hematopoiesis: two-stage process involving

* Mitotic division (proliferation)
* Maturation (differentiation)

What is the role of erythropoietin?

Hormone from kidney that stimulates erythrocyte production

Where does RBC destruction occur?

* 80-90% of RBCs get digested by macrophages in spleen and liver


* 10-20% inside blood vessels

What is the mechanism for RBC destruction?

* As RBCs age, enzyme activities decrease
* Amount of membrane lipids decrease
* Cell loses ability to deform and becomes fragile
* HbA levels increase
* Heme is reduced to bilirubin


* Globin and iron portions are conserved and reused
* Bilirubin is then degraded to the urobilinogen and excreted primarily in the feces and in the urine

What is the product of RBC destruction?

Bilirubin

What are the basic etiologic classifications for anemia?

* Under production of RBC
* Over production of RBC (hemolysis)
* Blood loss

What is aplastic anemia?

Stem cell disorder characterized by reduction of hematopoietic tissue, fatty marrow replacement

What is the pathogenesis of aplastic anemia?

Caused by toxic, radiant, or immunologic injury to the bone marrow stem cells

What are the laboratory features for aplastic anemia?

* Pancytopenia (low RBC, WBC, and platelets)


* Low WBC is important for prognosis (low leukocytes = susceptibility

What is vitamin B12 and folate-deficiency anemia?

* Pernicious anemia
* Disruption in DNA synthesis of blast cells produces megaloblasts (macrocytic)
* Folate deficiencies are associated with neural tube defects

What is the etiology and pathogenesis of anemia due to renal failure?

* Primarily from failure of the renal endocrine function, which causes impaired erythropoietin (EPO) production
* Secondarily from failure of renal excretory function
* Leads to hemolysis, bone marrow cell depression and blood loss

What are the laboratory features and clinical manifestations of anemia due to renal failure?

* Low RBC count
* Low hematocrit
* Low hemoglobin
* Some grossly deformed RBC
* General signs and symptoms of anemia usually manifest when hematocrit decreases to

What is pernicious anemia?

lack of intrinsic factor results in inability to absorb vitamin B12, which plays a role in RBC formation

What are the laboratory features of vitamin B12 or folate deficiency anemia?

* Low RBC, WBC, and platelet counts with increased MCV; megaloblastic dysplasia
* Macrocytic and hypersegmented neutrophils

What is iron deficiency anemia?

* Most common
* Results in the unavailability of iron for hemoglobin synthesis

What are the laboratory features of iron deficiency anemia?

* Smaller and paler RBC
* Low red cell indices: MCV, MCH, MCHC
* Decreased serum ferritin

What is thalassemia?

* Increased RBC destruction (hemolysis) resulting in decreased RBC survival rates
* Associated with mutant genes that suppress the rate of globin chain synthesis
* Classified by the polypeptide chain(s) with deficient synthesis)
* Most clinically severe from: thalassemia major (homozygous)
* Thalassemia minor (heterozygous) is less severe

What are the laboratory features of thalassemia?

* Hypochromic, microcytic RBCs
* Low MCV, MCH, and MCHC
* Erythroblastic hyperplasia (bone marrow)

What is sickle cell anemia?

* Genetically determined defect of hemoglobin synthesis resulting in hemoglobin instability and insolubility
* In Hemoglobin S, a single amino acid substitution causes the structural abnormality
* Sickled cells cause vascular occlusion

What are the laboratory features of sickle cell anemia?

Sickled RBC present in blood smear

What is polycythemia?

Excess RBC, which results in increased blood viscosity, leading to clinical symptoms, such as hypertension.

What is primary polycythemia?

* Absolute increase in RBC mass, leukocytosis, thrombocytosis
* Increased uric acid because of excess proliferation
* Oxygen saturation is normal

What are signs and symptoms of increased viscosity of blood?

* Hypertension
* Thrombosis
* Congested spleen and liver

What is secondary polycythemia?

Increased RBC production without increase in WBCs or platelets