Rinseback during red blood cell exchange with COBE Spectra does not affect fraction of cells remaining or post-exchange hematocrit

CaridianBCT currently does not recommend rinseback with its COBE Spectra cell separator during red blood cell (RBC) exchange procedure, as the machine's software does not take into account the "rinseback" when calculating the fraction of cells remaining (FCR, and therefore target hemoglobin S (HbS) value) and postexchange hematocrit (Hct). To our knowledge, no study has investigated the effect of rinseback on these laboratory values. Therefore, we performed pre- and postrinseback evaluations of FCR and Hct in 22 consecutive combined Isovolemic Hemodilution/Red blood cell (IHD-RBCx) exchange procedures in sickle cell anemia patients with stroke currently enrolled in our institution's chronic RBC exchange program. The pre- and-post rinseback values for HbS were 9.9 ± 4.66 and 10.7 ± 4.83 (P = 0.56) with corresponding FCRs of 22.6 ± 8.57 and 24.7 ± 8.75 (P = 0.44), and for Hct were 32.4 ± 2.93% and 32.2 ± 3.19% (P = 0.79), respectively. Since there was no significant difference in the "pre" and "post" values, we conclude that rinseback can be used during RBC exchange without any concern for significantly affecting Post Exchange HbS and Hct and possibly not waste 53 mL of precious red cell mass in the rinseback.