Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 173

Leukapheresis from an unstimulated donor produced only a marginally adequate dose of granulocytes for therapeutic benefit and never gained widespread use. The resulting blood component is a suspension of granulocytes in plasma prepared by cytapheresis. Early on, patients with chronic myelogenous leukemia (CML) were used as granulocyte donors. However, there were the obvious problems of the use of abnormal or malignant cells, as well as the limited number of patients with CML available to donate. The two additional strategies used to increase the granulocyte yield are the addition of the blood sedimentation agent hydroxyethyl starch (HES) to improve granulocyte separation within the centrifuge and the treatment of donors with corticosteroids, and more recently with G‐CSF, to increase the level of circulating granulocytes.

Leukapheresis procedures in general are usually more complex and lengthier than plateletpheresis. The leukapheresis procedure takes 2–3 hours, compared with about 1 1/2 hours for plateletpheresis, to improve the granulocyte yield. Usually 6,500–8,000 mL of the donor’s blood is processed through the instrument, with removal of about 50% of the granulocytes, resulting in a granulocyte concentrate with a volume of about 200 mL. Because granulocytes do not completely separate from the red cells, granulocyte concentrates usually contain a substantial number of red cells (hematocrit 10% or about 20 mL of red cells); therefore, red cell crossmatching is necessary.

A granulocyte concentrate must contain at least 1 × 10¹⁰ granulocytes in at least 75% of the units tested [47]. Neither the American Association of Blood Banks (AABB) Standards nor US Food and Drug Administration regulations specify the number of units that must be tested for quality‐control purposes, but because only a few granulocyte concentrates are prepared by most blood banks, it is customary to test all concentrates.