Apheresis Mathematics

As an apheresis nurse, it is important to not only pay attention to your donor/patient connected to the apheresis equipment, but also to the product you are collecting. Optimizing the procedure is crucial. There are many calculations related to apheresis medicine, and when you feel comfortable to apply these calculations in your practice, it will give additional value to your work and its logistics. You must obtain an optimal collection product or result without any risk for your donor or patient. Many specific blood values and physical characteristics influence the apheresis procedure. Think, for instance, of the total blood volume (TBV). The TBV varies from person to person. Also, the total plasma volume (TPV) is not the same for everyone as it depends on the TBV and the hematocrit. To work in a safe way, the extracorporeal volume (ECV) and the extracorporeal red cell volume (ECRV) are important parameters to be considered during apheresis procedures. An important quality parameter for your collection center is the collection efficiency (CE). By calculating the CE, you can not only compare the various devices in your center, but also the different nurses and operators. Based on the mean CE in your center, you can calculate the total of blood volumes of a donor to process to obtain a particular result, or you can make an estimation of the product yield when processing a specific amount of TBVs. Furthermore, you can use formulas to calculate the volume of red blood cells (RBC) to remove in case of RBC reductions, and if you only have the result of the hemoglobin (Hb) level, you can calculate the hematocrit (Hct) out of this Hb level.