Leukocytapheresis is a technique used to treat acute leukemia. NB: there is a contraindication to treating patients with APL (AML FAB M3) because of the risk of DIC. You should be able to check this with a blood smear. Pheresis (also referred to as apheresis) can be used for a huge number of conditions, which are outlined in exhaustive detail here.
How does it work? The concept is similar to dialysis or ECMO, except in pheresis, the plasma is siphoned off (and replacement fluid is given) and RBCs are returned to the body. There shouldn’t be any major fluid shifts like in dialysis.
Do you need a special catheter for pheresis? Ideally, pheresis is done through a peripheral IV because a lot of times these patients are thrombocytopenic, and you don’t want to delay pheresis for line placement or risk additional bleeding. However, there is such a thing as a pheresis catheter, which is a large-bore tunneled central line. Pheresis lines should be placed when multiple rounds of pheresis are expected, but to give emergent pheresis, anything from a peripheral IV to a regular central line is okay.
How much can someone improve with pheresis? Lots! Pheresis can be done when the WBC is 50-100K, but is only absolutely indicated when WBC >300K, as patients are at risk of leukostasis (if they don’t already have it). According to this review, the WBC can be expected to drop by 10-70% with the first session alone. However, it’s a game of diminishing returns. The WBC is most viscous and concentrated at the first session, so as sessions go on and the WBC improves, pheresis will become less and less effective.