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Count the fields in this order. To count the cells in each field, start in the upper left small square and follow the pattern indicated by the arrow in field 1 of figure 7-16. Count all of the cells within each square, including cells touching the lines at the top and on the left. Do not count any cells that touch the lines on the right or at the bottom. 13. Total the number of cells counted in all five fields and multiply by 10,000 to arrive at the number of red cells per cubic millimeter of blood. NOTE: The number of cells counted in each field should not vary by more than 20. A g r e a t e r v a r i a t i o n m a y i n d i c a t e p o o r distribution of the cells in the fluid, resulting in an inaccurate count. If this happens, the test must be repeated. HEMOGLOBIN DETERMINATION A routine test performed on practically every patient is the hemoglobin determination. Hemoglobin determination, or hemoglobinometry, is the measurement of the concentration of hemoglobin in the blood. Hemoglobin’s main function in the body is to carry oxygen from the lungs to the tissues and to assist in transporting carbon dioxide from the tissues to the lungs. The formation of hemoglobin takes place in the developing red cells located in bone marrow. Hemoglobin values are affected by age, sex, pregnancy, disease, and altitude. During pregnancy, gains in body fluids cause the red cells to become less concentrated, causing the red cell count to fall. Since hemoglobin is contained in red cells, the hemoglobin concentration also falls. Disease may also affect the values of hemoglobin. For example, iron deficiency anemia may drop hemoglobin values from a normal value of 14 grams per 100 milliliters to 7 grams per 100 milliliters. Above-normal hemoglobin values may occur when dehydration develops. Changes in altitude affect the oxygen content of the air and, therefore, also affect hemoglobin values. At higher altitudes there is less oxygen in the air, resulting in an increase in red cell counts and hemoglobin values. At lower altitudes there is more oxygen, resulting in a decrease in red cell counts and hemoglobin values. 7-14 COVER GLASS COUNTING CHAMBERS PROPERLY LOADED A HM3f0714 FLOODED AIR BUBBLES UNDER- LOADED B Figure 7-14.—Loading hemacytometer: A. Hemacytometer properly loaded; B. Hemacytometer improperly loaded. Example: Total number of cells counted = 423. Multiply: 423 x 10,000 = 4,230,000 Total red cell count 4,2300,000 cells/mm3 HM3f0715 Figure 7-15—Loaded hemacytometer placed inside petri dish.


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