Lecture 2- Hgb, hematocrit, and RBC indicies

hematopoiesis

production of RBCs

• increased under stress, illness, altitude, exercise, bleeding

erythropoiesis

hemoglobin structure

• 2 alpha and 2 beta chains

• each subunit has a heme and iron group that bind O2

RBC lifecyle

• 100-120 days

• olda damaged RBCs are removed from circulation and recycled

  • globin, heme, Fe

hematocrit

% of total sample composed of erythrocytes

mean corpuscular volume (MCV)

average volume/size of normal RBCs

• help classify type of anemia alongside RDW

adult critical values hematocrit

<21%; >65%

critical values hemoglobin

<7% ; >21%

causes of erythrocytosis (increased RBCs, hgb, hct)

• adrenal, brain, kidney, liver, cancer

• anabolic steroids

• congenital heart disease

• dehydration

• high altitude

• COPD/smoking

• medications- diuretics

• polycythemia

• sleep apnea

  • ex. prod more RBC sue to O2 deprivation

anemia

• decreased OXYGEN carrying capacity of the blood

• decrease in Hgb and/or Hct

• sign of underlying disease or deficiency, rather than specific diagnosis

  • anemia secondary to ____

pathophysiology of anemia

1) decreased production

• bone marrow damage (fibrosis, drugs)

• decreased marrow stimulation (renal disease- decreased EPO, inflammation)

• FE, folate, B12 deficiencies

2) destruction

• healthy bone marrow cant keep up with blood loss of hemolysis

elevated MCV- macrocytic

• >96

• EtOH use disorder - normal RDW

• folate deficiency - normal RDW

• HYPOthyroidism

• chronic liver disease (elevated RDW)

• medications: methotrexate, imuran, hydroxyurea - normal RDW

• multiple myeloma- elevated RDW

• myelodysplastic syndrome- elevated RDW

• pernicious anemia

• B12 def- elevated RDW
  
  

MCV- normocystic

• 80-90

• low RBC but normal size

• chronic disease - elevated RDW

• early B12 and iron def or mixed def - elevated RDW

• renal failure - elevated RDW

• sickle cell anemia - elevated RDW

low MCV- microcytic

• <80

• iron def anemia - elevated RDW

• toxins adn drugs - elevated RDW

• thalassemia - elevated RDW

• myelodysplastic syndrome - elevated RDW

mean corpuscular hemoglobin concentration (MCHC)

• concentration of Hbg in RBCs

• normal= normochromic

  • hemolytic anemia

• decreased= hypochromic

  • microcystic

  • iron def

  • thalassemia

red blood cell distribution width (RDW)

• indicates the variation in size or shape of RBCs

  • degree of ansiocytosis (RBCs of variable and abnormal size)

• increase:

  • iron def anemia

  • B12 or folate def anemia

  • hemoglobinpathies- sickle cell

  • hemolytic anemia

  • post- hemorrhagic anemia

degenerative forms of RBCs

• poikilocytosis: abnormal variation in shape

  • ex. sickle cell

• anisosytosis: abnormal variation in size

  • macro, megal

factors that interfere with the accuracy of hgb/hct values and RBCs indicies

• Hgb: slight diurnal variation, levels highest 8am, lowest 8pm

• heavy smokers (chronic inflammation)

• hemodilution (over hydration) affect Hgb/Hct

• pregnancy= hemodilution, levels decreased due to increase in volume

• high altitudes increase hgb/hct- physiologic response due to decreased O2 available

• abnormal RBC size

  • higher Hct with larger RBCs take up grater % of total blood volume, RBC size affects MCH and MCHC

• unreliable labs immediately after hemorrhage

  • % of total blood volume taken up by the RBC will not change until the blood volume id replaced with fluids

• exremely elevated WBC

  • decreases Hct and falsely indicates anemia→ increase MCV and MCH

• MEDICATIONS