Physician Assistant Exam Review

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S2 E074 Red Blood Cells

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Red Blood Cells

Priming Questions

  • What are the four polypeptide chains that make up hemoglobin?
  • Define polycythemia
  • What does MCV stand for and what does it mean?
  • Define hemolysis.

Red Blood Cells Simplified

  • The specific shape of a RBC gives it an increased surface area for better gas exchange and flexibility for fitting into tiny places.
  • The main job of the RBC is to carry oxygen to the cells of the body and CO2 out from the cells to the lungs.
  • Hemoglobin is the protein structure within the RBC that has an affinity for Oxygen.
  • Hemoglobin is made up of four heme iron complexes and four polypeptide chains two alpha and two beta chains.

There are two basic problems red blood cells can have

  • Polycythemia – To many red blood cells
  • Anemia – There are not enough functioning red blood cells
  • Due to lack of production or destruction/loss of RBCs
  • Due to production of poorly or non functioning RBCs

Clinical Presentation

  • Patients with red blood cell disorders typically do not exhibit any symptoms, and when they do they are vague and overlapping.

For example:

  • Headaches
  • Fatigue
  • Exertional dyspnea
  • Dizziness
  • Tachycardia
  • Blurred vision

Physical exam may show

  • Pallor of the nail beds
  • Pallor of conjunctiva
  • Pallor of the palmar creases

Vocabulary

  • Reticulocytes – Immature red blood cells
  • Mean corpuscular volume (MCV) – Volume of an average red blood cell in the sample
  • Microcytosis – MCV< 80 (small cells)
  • Microcytosis – MCV>100 (big cells)
  • Hypochromic – RBCs a more pale than usual (decreased color)
  • Hemolysis – Destruction of RBCs

Important Labs

  • CBC
  • Hemoglobin (Hgb) – Measures the amount of hemoglobin in the blood
  • Male 13.5 – 17.5 g/dL
  • Female 12.0 – 15.5 g/dL
  • Hematocrit (Hct) – The volume percentage of red blood cells in blood
  • Male 41-51%
  • Female 36-44%
  • Reticulocyte count
  • Mean corpuscular volume (MCV)
  • Peripheral blood smear will give you cell morphology (shape)

Polycythemia

  • Elevated hematocrit or hemoglobin

Causes

  • Myeloproliferative syndrome
  • Chronic low oxygen
  • Malignancy
  • Over transfusion

Clinical Presentation

  • Most likely asymptomatic
  • Weakness
  • Headaches
  • Lightheadedness
  • blurred vision
  • Pruritus
  • GI bleeding

Labs & Studies

  • Hct > 55% (normal is 36-50%)

Treatment

  • Phlebotomy
  • Hydroxyurea – this is a myelosuppressive medication

Study tip

  • Use multiple passes to judge depth

Priming Questions

  • What are the four polypeptide chains that make up hemoglobin? 2 alpha and 2 beta polypeptide chains
  • Define polycythemia – too many RBCs
  • What does MCV stand for and what does it mean? Mean corpuscular volume (MCV) – Volume of an average red blood cell in the sample
  • Define hemolysis. Destruction of RBCs