When doctors aspirate bone marrow from the cavities in bones, it is full of stem cells—cells from which all types of blood cells evolve. Stem cells can also be found in the circulating (also called peripheral) blood, although in much lower numbers.
In a peripheral blood stem cell transplant (PBSCT), the childs own blood stem cells are harvested in a procedure called apheresis or leukapheresis. The pheresis is performed as the child is recovering from an intensive course of chemotherapy. As the blood counts begin to improve, the number of stem cells in the blood increases. Most centers also treat the child with GCSF (granulocyte colony stimulating factor) and/or GMCSF (granulocyte-macrophage colony stimulating factor) after the chemotherapy to further increase the numbers of stem cells in the blood.
Six-year-old Ethan sailed through the stem cell harvest. He was on Neupogen (G-CSF), which is an injectable med that stimulates white cell release from the marrow. Neupogen has been a piece of cake for Ethan. Once he had enough of the stem cells in his bloodstream, he had a femoral PICC line placed, because they needed a larger catheter to do the harvest. The only down side was that he had to lie completely flat for about six hours, and collection took two days. Plan a lot of quiet activities! Videos, books on tape, handheld games, cards.
When the childs peripheral blood counts rise, blood is removed through a central venous catheter or a special temporary pheresis catheter and circulated through a machine that extracts the stem cells. The blood is then returned to the child. Each pheresis session lasts two to eight hours. The number of sessions required varies. Infants may need only one session, but children who have received extensive prior irradiation or chemotherapy may need six or eight sessions.
In rare cases, it is impossible to get enough stem cells from children who have recently undergone extensive chemotherapy and/or radiation. In these children, a bone marrow harvest may be able to collect an adequate number of stem cells.
Potential complications of peripheral blood stem cell apheresis include:
• Hypocalcemia (low calcium in the blood). Your child may experience muscle cramps, chills, tremors, tingling of the fingers and toes, dizziness, or occasional chest pain.
• Thrombocytopenia (low platelets). A reduction in platelets can occur if platelets stick to the tubes in of the apheresis machine. Your childs platelet count will be checked before and after the apheresis, and a platelet transfusion will be given if needed.
• Hypovolemia (low blood volume). A reduction in blood volume can occur at any time during the procedure and is more common in small children. Symptoms can include low blood pressure, rapid heart rate, lightheadedness, and sweating.
• Infection. In many cases, a new and larger central venous catheter is placed prior to the apheresis procedure to reduce the likelihood of infection. If your child develops fever, chills, or low blood pressure (symptoms of infection), then blood cultures will be obtained and IV antibiotics given.
Most apheresis procedures are performed safely on an outpatient basis or in a short-stay clinic or hospital unit. Some institutions, however, do require hospitalization throughout the procedure.
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