Editing Apheresis (section)

== Method ==

Depending on the substance that is being removed, different processes are employed in apheresis. If separation by [[density]] is required, [[centrifugation]] is the most common method. Other methods involve absorption onto beads coated with an absorbent material<ref>{{Cite journal |last1=Fuchs |first1=Kornelius |last2=Rummler |first2=Silke |last3=Ries |first3=Wolfgang |last4=Helmschrott |first4=Matthias |last5=Selbach |first5=Jochen |last6=Ernst |first6=Friedlinde |last7=Morath |first7=Christian |last8=Gauly |first8=Adelheid |last9=Atiye |first9=Saynab |last10=Stauss-Grabo |first10=Manuela |last11=Giefer |first11=Mareike |date=2022 |title=Performance, clinical effectiveness, and safety of immunoadsorption in a wide range of indications |journal=Therapeutic Apheresis and Dialysis |volume=26 |issue=1 |pages=229–241 |doi=10.1111/1744-9987.13663 |pmc=9291474 |pmid=33914397}}</ref> and filtration.<ref>{{cite journal |vauthors=Hirano R, Namazuda K, Hirata N |title=Double filtration plasmapheresis: Review of current clinical applications |journal=Ther Apher Dial |volume=25 |issue=2 |pages=145–151 |date=April 2021 |pmid=32558286 |doi=10.1111/1744-9987.13548 }}</ref>

The centrifugation method can be divided into two basic categories:<ref>{{cite journal |vauthors=Lambert C, Gericke M, Smith R, Hermans C |title=Plasma extraction rate and collection efficiency during therapeutic plasma exchange with Spectra Optia in comparison with Haemonetics MCS+ |journal=J Clin Apher |volume=26 |issue=1 |pages=17–22 |date=2011 |pmid=21312255 |doi=10.1002/jca.20271 }}</ref>

=== Continuous flow centrifugation ===

Continuous flow centrifugation (CFC) historically required two [[venipunctures]] as "continuous" means the blood is collected, spun, and returned simultaneously. Newer systems can use a single venipuncture by pooling blood in a vessel and cycling through drawing and returning blood though the needle while the centrifuge continuously processes blood remaining in the vessel.<ref>{{cite patent |country=US | number=7108672| status=patent| title=Extracorporeal blood processing methods and apparatus }}</ref> The main advantage of this system is the low extracorporeal volume (calculated by volume of the apheresis chamber, the donor's [[hematocrit]], and total blood volume of the donor) used in the procedure, which may be advantageous in the elderly and for children.{{citation needed|date=November 2021}}

=== Intermittent flow centrifugation ===

Intermittent flow centrifugation (IFC) works in cycles, taking blood, spinning/processing it and then giving back the unused parts to the donor in a [[Bolus (medicine)|bolus]]. The main advantage is a single venipuncture site. It does require a larger extracorporeal volume, and takes significantly longer to perform the procedure via IFC. As such, it is less likely to be used for therapeutic reasons, and is often seen in Donation Center settings.<ref>{{Cite web |title=Apheresis |url=https://www.transfusions.org/p/apheresis.html |access-date=2022-10-24 |language=en}}</ref> To stop the blood from [[Coagulation|coagulating]], [[anticoagulant]] is automatically mixed with the blood as it is pumped from the body into the apheresis machine.<ref>{{cite journal |vauthors=Vurro F, Merolle L, Marraccini C, Parisi M, Canovi L, Erta B, Santachiara A, Bonvicini L, Giorgi Rossi P, Baricchi R, Pertinhez TA |title=Quantitative assessment of the anticoagulant in plasma units collected by plasmapheresis |journal=Transfusion |volume=59 |issue=6 |pages=2113–20 |date=June 2019 |pmid=30875439 |doi=10.1111/trf.15244 }}</ref>

=== Centrifugation variables ===

The centrifugation process itself has four variables that can be controlled to selectively remove desired components. The first is spin speed and bowl diameter, the second is "sit time" in centrifuge, the third is solutes added, and the fourth is not as easily controllable: plasma volume and cellular content of the donor. The result in most cases is the classic sedimented blood sample with the [[Red blood cells|RBCs]] at the bottom, the [[buffy coat]] of platelets and [[White blood cells|WBCs]] ([[lymphocytes]], [[granulocytes]], [[monocytes]]) in the middle and the plasma on top.<ref name=Vrielink23>{{cite journal |vauthors=Vrielink H, Neyrinck MM |title=Basics of apheresis and equipment |journal=Transfus Apher Sci |volume=62 |issue=2 |pages=103671 |date=April 2023 |pmid=36870905 |doi=10.1016/j.transci.2023.103671 }}</ref>