Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 172

Chronic shortages of certain types of red cells stimulated interest in the use of apheresis to collect the equivalent of two units of red cells from some donors, especially group O. Several instruments are now available for red cell apheresis [30, 31, 36, 38, 39, 55–60] (Table 6.1). After removing RBCs, saline may be infused to the donor to maintain blood volume. The RBCs can be stored in an additive solution for the usual 42 days [30, 36, 39, 59]. The red cell products obtained by apheresis are much more standardized than red cells prepared from whole blood, but otherwise red cells obtained by apheresis have the same characteristics as those produced from whole blood (Table 6.2). The advantages provided by red cell apheresis are to obtain two units of red cells from one donation to allow for fewer donor visits, possible increases in red cell availability, and potentially fewer donor exposures if both units of red cells from one donor are transfused to one patient.

Donors for two‐unit red cell apheresis must meet weight and hemoglobin standards specified for each instrument. Because two units of red cells are removed, they may donate only every 4 months. This is adequate for red cell recovery but may not allow complete regeneration of iron stores [61]. Apheresis for two‐unit red cell collection is taking its place in the mixture of blood component production activities (Table 6.2). Although reactions following RBC collection by apheresis are more common than whole blood donation, almost all reactions were minor and for donors younger than 20 years, reactions are equally common after two RBC collections or a whole blood collection. Thus, two RBC collections are as safe as a whole blood collection [62].

Table 6.2 Comparison of red cell units prepared from whole blood with red cell units prepared by double‐unit red cell apheresis.

	Whole blood	Alyxa	Trima	MCSb
Product volume (mL)	310	301	347	312
RBC volume (mL)	190	177	NA	182
Total hemoglobin (g)	55	57.8	60.7	—
Hematocrit (%)	60	58	55	58
Collection time (min)	8	28	NA	50

NA, not available; RBC, red blood cell.

^a Source: Louie J, Greco BJ, Martinez S. Quality and characteristics of red cells collected on a new automated portable component collection system. Transfusion 2003; 43(Suppl):135A (abstract).

^b Source: Smith JW, Gilcher RO. Red blood cells, plasma, and other new apheresis‐derived blood products: improving product quality and donor utilization. Transfus Med Rev 1999; 13:118–123.