Apheresis

Apheresis

Apheresis involves passing the blood of a donor or patient through a machine that separates one specific component and returns the rest to the body. This process, known as extracorporeal therapy, utilizes various methods depending on the substance being removed. Centrifugation is commonly used for density-based separation, while other techniques include absorption onto coated beads and filtration.

Continuous flow centrifugation (CFC) historically required two punctures for blood collection, processing, and return simultaneously. Modern systems can achieve this with a single puncture, reducing extracorporeal volume. Intermittent flow centrifugation works in cycles, processing blood and returning components in a single puncture, aided by automatic mixing with anticoagulant to prevent coagulation.

Centrifugation variables allow selective removal of components, including spin speed, bowl diameter, sit time, solutes added, and plasma volume. The end result typically separates red blood cells at the bottom, platelets and white blood cells in the middle, and plasma on top.

Apheresis encompasses various types, such as plasmapheresis for blood plasma, erythrocytapheresis for red blood cells, plateletpheresis for platelets, leukapheresis for white blood cells, and stem cell harvesting for bone marrow transplantation.

Safety measures include the use of single-use kits to prevent infection and monitoring immune system effects. Replacement fluid is crucial to maintain intravascular volume, with options including crystalloids, serum albumin, or blood products, each with associated risks such as citrate toxicity, ABO incompatibility, infection, and antigen reactions.