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 since they contain carbonic anhydrase
How are RBCs produced?
Through hematopoiesis: a 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% of RBCs are destructed inside blood vessels
What is the mechanism for RBC destruction?
As RBCs age, enzyme activities decrease and amount of membrane lipids decrease
The cell loses its 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 urine
What is the product of RBC destruction?
Bilirubin
What are the basic etiologic classifications for anemia?
Under production of RBC
Overproduction 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 immunological injury to the bone marrow stem cells
What is pancytopenia?
Low RBC, WBC, and platelets
What are the laboratory features of aplastic anemia?
Pancytopenia
Low WBC is important for prognosis (low leukocytes = susceptibility
Folate deficiencies are associated with neural tube defects
Pernicious anemia is characterized by the lack of intrinsic factor, resulting in the inability to absorb vitamin B12, which plays a role in RBC formation
What are the laboratory features of pernicious anemia?
Pancytopenia with increased molecular corpuscular volume (MCV); megaloblastic dysplasia
Macrocytic and hypersegmented neutrophils
What is the etiology of anemia due to renal failure?
Primarily from failure of the renal endocrine function, with causes impaired erythropoietin (EPO) production
Secondarily from failure of renal excretory function
Anemia due to renal failure 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, hematocrit, and hemoglobin
Some grossly deformed RBC
General signs and symptoms of anemia usually manifest when hematocrit decreases to <20%
Iron deficiency anemia is the most common form of anemia and results in the unavailability of iron for hemoglobin synthesis
What are the laboratory features of iron deficiency anemia?
Smaller and paler RBCs
Low RBC indices: MCV, MCH, MCHC
Decreased serum ferritin
Thalassemia is an inherited blood disorder caused by increased RBC destruction (hemolysis), resulting in decreased RBC survival rates
Thalassemia is associated with mutant genes that suppress the rate of globin chain synthesis
Thalassemia is classified by the polypeptide chains with deficient synthesis
Thalassemia major is the most clinically severe and homozygous
Thalassemia minor is less severe and heterozygous
What are the laboratory features of thalassemia?
Hypochromic, microcytic RBCs
MCV, MCH, and MCHC are low
Erythroblastic hyperplasia (bone marrow)
Sickle cell anemia is characterized by a genetically determined defect of hemoglobin synthesis, resulting in hemoglobin instability and insolubility
Sickle cell anemia is found in hemoglobin S, in which a single amino acid substitution causes the structural abnormality
Sickled cells cause vascular occlusion
What are the laboratory features of sickle cell anemia?
Sickled RBCs present in blood smear
Polycythemia is characterized by excess RBCs, which results in increased blood viscosity, leading to clinical symptoms, such as hypertension
Primary polycythemia is characterized by
An absolute increase in RBC mass, leukocytosis, and thrombocytosis
Increased uric acid because of excess proliferation
Oxygen saturation is normal
The signs and symptoms of increased viscosity of blood are:
Hypertension
Thrombosis
Congested spleen and liver
Secondary polycythemia is characterized by increased RBC production WITHOUT an increase in WBCs or platelets
What are the functions of RBCs?
Transport oxygen to tissues
Remove carbon dioxide from the tissues
Buffer blood pH since they contain carbonic anhydrase
How are RBCs produced?
Through hematopoiesis: a 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% of RBCs are destructed inside blood vessels
What is the mechanism for RBC destruction?
As RBCs age, enzyme activities decrease and amount of membrane lipids decrease
The cell loses its 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 urine
What is the product of RBC destruction?
Bilirubin
What are the basic etiologic classifications for anemia?
Under production of RBC
Overproduction 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 immunological injury to the bone marrow stem cells
What is pancytopenia?
Low RBC, WBC, and platelets
What are the laboratory features of aplastic anemia?
Pancytopenia
Low WBC is important for prognosis (low leukocytes = susceptibility
Folate deficiencies are associated with neural tube defects
Pernicious anemia is characterized by the lack of intrinsic factor, resulting in the inability to absorb vitamin B12, which plays a role in RBC formation
What are the laboratory features of pernicious anemia?
Pancytopenia with increased molecular corpuscular volume (MCV); megaloblastic dysplasia
Macrocytic and hypersegmented neutrophils
What is the etiology of anemia due to renal failure?
Primarily from failure of the renal endocrine function, with causes impaired erythropoietin (EPO) production
Secondarily from failure of renal excretory function
Anemia due to renal failure 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, hematocrit, and hemoglobin
Some grossly deformed RBC
General signs and symptoms of anemia usually manifest when hematocrit decreases to <20%
Iron deficiency anemia is the most common form of anemia and results in the unavailability of iron for hemoglobin synthesis
What are the laboratory features of iron deficiency anemia?
Smaller and paler RBCs
Low RBC indices: MCV, MCH, MCHC
Decreased serum ferritin
Thalassemia is an inherited blood disorder caused by increased RBC destruction (hemolysis), resulting in decreased RBC survival rates
Thalassemia is associated with mutant genes that suppress the rate of globin chain synthesis
Thalassemia is classified by the polypeptide chains with deficient synthesis
Thalassemia major is the most clinically severe and homozygous
Thalassemia minor is less severe and heterozygous
What are the laboratory features of thalassemia?
Hypochromic, microcytic RBCs
MCV, MCH, and MCHC are low
Erythroblastic hyperplasia (bone marrow)
Sickle cell anemia is characterized by a genetically determined defect of hemoglobin synthesis, resulting in hemoglobin instability and insolubility
Sickle cell anemia is found in hemoglobin S, in which a single amino acid substitution causes the structural abnormality
Sickled cells cause vascular occlusion
What are the laboratory features of sickle cell anemia?
Sickled RBCs present in blood smear
Polycythemia is characterized by excess RBCs, which results in increased blood viscosity, leading to clinical symptoms, such as hypertension
Primary polycythemia is characterized by
An absolute increase in RBC mass, leukocytosis, and thrombocytosis
Increased uric acid because of excess proliferation
Oxygen saturation is normal
The signs and symptoms of increased viscosity of blood are:
Hypertension
Thrombosis
Congested spleen and liver
Secondary polycythemia is characterized by increased RBC production WITHOUT an increase in WBCs or platelets