Effects on the Hematologic System

The hematologic or hematopoietic system is responsible for producing new blood cells. The bone marrow contained in the long bones of the body contains stem cells, the precursors to the main blood components. Stem cells are able to reproduce and differentiate into red blood cells, white blood cells, and platelets, depending on the body’s need for replacement cells. Because the cells of the bone marrow are almost always in some phase of cell division and reproduce rapidly, most cytotoxic drugs damage bone marrow stem cells. The term "myelo" refers to the bone marrow. Bone marrow depression, also known as myelosuppresion, is one of the most common side effects of chemotherapy. The main effects of myelosuppression are anemia (less than normal number of red blood cells), leukopenia (less than normal number of white blood cells), and thrombocytopenia (less than normal number of platelets).

As blood cells normally wear out, they are constantly being replaced by the bone marrow. Following chemotherapy, as these cells wear out, they are not replaced as they would be normally, and the blood cell levels begin to drop. The decrease in blood cell counts does not occur immediately after chemotherapy because the drugs do not destroy the cells already circulating in the bloodstream. Instead, the drugs temporarily prevent formation of new blood cells by the bone marrow stem cells. Normally, white blood cells have an approximate 6-hour life span, platelets live for about 10 days, and red blood cells have a life span of 120 days.

The lowest count that blood cell levels fall to is called the nadir. The nadir for each blood cell type will occur at different times but usually WBC’s and platelets reach their nadir or lowest point within 7-14 days. It is at this point in time that patients are most susceptible to infection and bleeding. RBC’s live longer and will not reach a nadir for several weeks.

Bone marrow depression is caused by destruction of blood cells circulating in the bloodstream.


Red blood cells or erythrocytes carry oxygen from the lungs to the tissues and transport carbon dioxide back to the lungs. There are normally between 4 and 6 million red blood cells per milliliter of blood. The hematocrit is a measurement of the percentage of total blood volume occupied by red blood cells. A normal hematocrit ranges between 36-42%. Hemoglobin is the red pigment in RBC’s; it's function is to carry oxygen. An average hemoglobin is between 12 to 16 grams per deciliter. A lower than normal amount of red blood cells is referred to as anemia. Signs and symptoms of anemia include a fall in the red blood cell count, decreased hemoglobin and hematocrit levels, fatigue, hypotension, shortness of breath, tachypnea, tachycardia, headaches, dizziness, and irritability.

Anemia caused by chemotherapy is temporary. If the patient’s hematocrit and hemoglobin fall too low, transfusions of packed red blood cells may be needed until the bone marrow has recovered it’s normal ability to produce more blood cells. Because blood transfusions have some risks, this procedure is used only if there are serious anemia symptoms. A newer option for treating anemia caused by chemotherapy is giving erythropoietin, a naturally occurring growth factor that stimulates RBC production by bone marrow cells. Erythropoetin can relieve symptoms of anemia and reduce the need for blood transfusions.

Management strategies for anemia include:

a. Obtaining a baseline complete blood count and monitoring the number of red blood cells during and after chemotherapy.
b. Encouraging the patient to eat foods that are rich in iron, vitamins and minerals.
c. Teaching the patient to report signs and symptoms of anemia such as fatigue, dizziness, headaches, irritability, shortness of breath, an increase in heart rate or rate of breathing or both.
d. Encouraging the patient to modify and pace activities to get sufficient sleep and rest.
e. Giving transfusions of packed red blood cells or human erythropoetin as ordered.

Red blood cells reach their nadir several weeks after treatment with cytotoxic drugs.


White blood cells help the body resist infection. Bacteria can invade many areas of the body, including the skin, respiratory tract, oral cavity, sinuses, and perianal area. A normal white blood cell (WBC) count ranges between 4,000 and 10,000 per milliliter of blood. An overall decrease in the total white blood cell count is known as leukopenia. WBC’s are divided into 2 main categories: granulocytes, which contain granules in the cytoplasm of the cell, and agranulocytes, which have no cellular granules. Granulocytes include neutrophils, eosinophils, and basophils. Lymphocytes and monocytes are agranulocytes.

Granulocytes, especially neutrophils, provide an important defense against infections and are the most numerous type of WBC. The normal range of neutrophils is between 2,500 and 6,000 cells per milliliter. A lower than normal number of neutrophils is referred to as neutropenia. Neutropenia is the most common factor that puts people with cancer at risk of potentially life-threatening infection. A patient with an absolute neutrophil count of 1,000 or less is considered to be neutropenic. Patients with a neutrophil count of 500 or less are severely neutropenic and at high risk of infection.

The type, dose, schedule, and mode of administration of a drug help predict its myelosuppressive effects. Neutropenia is most severe with the use of cell cycle-specific drugs, particularly those that are active in the S and M phases. However, cell cycle nonspecific drugs can have a delayed and prolonged effect on the bone marrow. The use of high-dose or combination regimens can cause persistent nadirs because of intense damage to the stem cell population. If WBC counts are very low, the patient may be given antibiotics as a preventative measure. In the cancer patient with neutropenia, a fever is usually treated with broad-spectrum antibiotics and colony stimulating factors.

Neutropenia is the most common reason patients receiving cancer chemotherapy are at high risk of infection.

Several naturally occurring hematopoietic growth factors may stimulate the production of various types of blood cells. These growth factors are also called colony-stimulating factors. The 2 growth factors that stimulate production of WBC’s are granulocyte-macrophage colony stimulating factor and granulocyte colony stimulating factor. These drugs may be given the day after chemotherapy. In some situations, doctors may prescribe growth factors in order to prevent the WBC from falling too low, so that chemotherapy can be given on schedule.

Management strategies for leukopenia include:

a. Obtaining baseline data before chemotherapy begins, particularly the absolute neutrophil count.
b. Monitoring the neutrophil count during and after chemotherapy.
c. Assessing the patient for signs and symptoms of infection.
d. Teaching the patient about signs of infection such as fever, sore throat, new cough or shortness of breath, nasal congestion, burning during urination, shaking chills, redness, swelling, and warmth at the site of an injury.
e. Giving antibiotics or colony stimulating factors as ordered.
f. Instructing the patient to maintain a safe and clean environment to prevent infection.
g. Advising the patient to avoid people who have colds or any communicable diseases.
h. Advising the patient to avoid eating raw fruits and vegetables, handling fresh flowers or plants, or handling pet excrement due to the possibility of acquiring a fungal or bacterial infection.
i. Emphasizing the importance of meticulous personal hygiene. To avoid infection, the patient should be advised to bathe daily, perform oral care every 4 hours or more often, empty the bladder at least every 4 hours, and avoid using rectal suppositories or enemas. Female patients should be instructed to avoid douching or using tampons that can serve as reservoirs for infection.
j. Instructing the patient in good hand washing technique.
k. Encouraging the patient to maintain good nutrition by eating a high-protein, high-carbohydrate diet, and drinking at least 8 glasses of fluid daily.

Patients who are neutropenic should be encouraged to eat a diet of fresh fruits and vegetables.

The Oncology Nursing Society is an excellent resource for clinical practice matters for nurses.

For example, click here for information about management and prevention of neutropenia.

Look for the answer to this question

What are 2 drugs that are given to stimulate production of white blood cells?


Thrombocytes or platelets are critical for maintaining homeostasis, by being able to form blood clots when needed. The normal range for platelet counts is between 150,000 and 450,00 per milliliter of blood. The term for a low platelet count is thrombocytopenia. Symptoms of thrombocytopenia include easy bruising, bleeding longer than usual after minor cuts or scrapes, bleeding gums or nose bleeds, development of ecchymoses (large bruises) and petechiae (multiple small bruises). Sites of bleeding can include the skin, mucous membranes, gastrointestinal system, genitourinary system, respiratory system, and the brain. Chemotherapy can depress the platelet count and drugs containing acetylsalicylic acid (aspirin) or nonsteroidal anti-inflammatory agents (NSAIDS) can worsen the potential for thrombocytopenia.

Although low platelet counts resulting from chemotherapy are temporary, they can cause serious and potentially life-threatening blood loss from injury or bleeding that can damage internal organs. If platelet counts are very low (below 10,000), or if a person with moderately low counts has greater than normal bleeding, platelet transfusions may be given. Transfused platelets last only a few days, and some people who have received multiple platelet transfusions can develop an immune reaction that destroys donor platelets. A platelet growth factor may be given to people with severe thrombocytopenia to decrease the need for platelet transfusions.

Patients with a platelet count of 10,000 or below are at high risk of spontaneous bleeding.

Management strategies for thrombocytopenia include:

a. Monitoring the patient’s platelet count closely.
b. Assessing for superficial or internal signs of bleeding such as petechiae, epistaxis (nose bleeds), easy bruising, prolonged bleeding time, coffee ground emesis and hematuria.
c. Testing the stool and urine for blood.
d. Teaching the patient to maintain a safe environment to prevent falls or trauma.
e. Using stool softeners to avoid straining, which can cause rectal tearing and bleeding, and eating a high fiber diet and drinking plenty of fluids to avoid constipation.
f. Postponing, if possible, any invasive medical or surgical procedures, including dental extractions, multiple venipunctures, or injections.
g. Avoiding using sharp instruments such as razors or scissors for grooming.
h. Avoiding medications that may prolong or exacerbate bleeding, such as steroids or over-the-counter drugs containing aspirin.
i. Using a soft toothbrush and avoiding flossing.
j. Using a water-soluble lubricant for sexual activity.
k. Giving platelet transfusions as ordered.

Patients with low platelet counts should use drugs containing aspirin for pain relief.