The erythrocyte (RBC) count, a component of the CBC, is the determination of the number of RBCs per cubic millimeter. In international units, this is expressed as the number of RBCs per liter of blood. The test is less significant by itself than it is in computing Hgb, Hct, and RBC indices.

Many factors influence the level of circulating erythrocytes. Decreased numbers are seen in disorders involving impaired erythropoiesis excessive blood cell destruction (e.g., hemolytic anemia), and blood loss, and in chronic inflammatory diseases. A relative decrease also may be seen in situations with increased body fluid in the presence of a normal number of RBCs (e.g., pregnancy). Increases in the RBC count are most commonly seen in polycythemia vera, chronic pulmonary disease with hypoxia and secondary polycythemia, and dehydration with hemoconcentration. Excessive exercise, anxiety, and pain also produce higher RBC counts. Many drugs can cause a decrease in circulating RBCs (see Table 1-5), whereas a few drugs, such as methyldopa and gentamicin, can cause an increase.²³

• Excessive exercise, anxiety, pain, and dehydration may lead to false elevations.
• Hemodilution in the presence of a normal number of RBCs may lead to false decreases (e.g., excessive administration of intravenous fluids, normal pregnancy).
• Many drugs may cause a decrease in circulating RBCs (see Table 1-5).
• Drugs such as methyldopa and gentamicin may cause an elevated RBC count.

• Routine screening as part of a CBC
• Suspected hematologic disorder involving RBC destruction (e.g., hemolytic anemia)
• Monitoring effects of acute or chronic blood loss
• Monitoring response to drug therapy that may alter the RBC count (see Table 1-5)
• Monitoring clients with disorders associated with elevated RBC counts (e.g., polycythemia vera, chronic obstructive pulmonary disease)
• Monitoring clients with disorders associated with decreased RBC counts (e.g., malabsorption syndromes, malnutrition, liver disease, renal disease, hypothyroidism, adrenal dysfunction, bone marrow failure)

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).

A venipuncture is performed and the sample collected in a lavender-topped tube. A capillary sample may be obtained in infants and children as well as in adults for whom venipuncture may not be feasible.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample (see Appendix I).

• Anemia: Note and report signs and symptoms of anemia associated with decreased counts in combination with Hgb and Hct decreases. Prepare to administer ordered oral or parenteral iron preparation or a transfusion of whole blood or packed RBCs. Prepare for phlebotomy if levels are increased in polycythemia vera or secondary polycythemia.