Cell apheresis, in general, is a widely accepted, safe, and effective procedure used to collect a large volume of one or more components from the blood. The leukapheresis procedure is a short term process that lasts between 80-150 minutes from a non-mobilized donor (a donor in a physically stable position) and is very safe when performed in specialized facilities.
Leukapheresis can be performed in a continuous, intermittent, or discontinuous manner, though most procedures use continuous flow devices due to faster procedure times and decreased extracorporeal volumes of whole blood. Continuous flow technology, in a closed-loop system, has one arm with whole blood drawn out of the body while the other arm has RBCs, platelets, and plasma returned to the body all while the apheresis machine continuously collects WBCs.
Frank Strobl’s overview of therapeutic apheresis outlines the major steps of the leukapheresis procedure. Below are some of the major bullet points from this resource combined with PPA Research Group’s IRB and approved protocol for leukapheresis.
- All apheresis services should adhere to regulations outlined in the AABB Standards for Blood Banks and Transfusion Services and the Code of Federal Regulations. Centers may also refer to the FDA and the American Society for Apheresis for further reference and guidelines.
- All personnel, including medical technologists, nurses, medical assistants, and physicians, attending to the leukapheresis procedure should be thoroughly trained and adhere to these regulations.
- The leukapheresis machine (see LEUKAPHERESIS MACHINE for more information) should be turned on and have all components intact according to the device’s manufacturer instructions. Each facility should have these instructions readily available in their SOP (Standard Operating Procedure).
- The components include but are not limited to specific disposable materials such as sterile plastic collection chambers, needles, cannulas, tubing, and bags. Along with these disposable materials, each machine should have ample anticoagulant, such as sodium citrate, for use in centrifugation. Each machine is equipped with a centrifugation instrument which allows for either intermittent flow centrifugation (IFC) or continuous flow centrifugation (CFC).
- In IFC, the leukapheresis process is performed in cycles: withdrawal of whole blood, separation of desired leukocytes, and reinfusion of remaining components with the advantage of having one venipuncture for the procedure. This process, however, involves a greater volume of extracorporeal blood and takes longer than CFC.
- In CFC, the leukapheresis process is performed in a closed-loop system with continuous flow for withdrawal, separation, and reinfusion with the disadvantage of having two venipuncture sites and the advantage of a shorter donation period. For the purpose of this guidebook, the rest of the outlined procedure will detail the CFC technique.
- Before the venipunctures are made, the collection tubing circuitry must be primed with replacement fluid to maintain intravascular fluid volume and pressure. Most leukapheresis machines will use normal saline and/or albumin depending on the protocol. Although normal LEUKAPHERESIS GUIDE 10 saline historically has been easily accessible and relatively inexpensive, a diluted saline solution with 5% albumin is highly desirable in this procedure to help maintain oncotic pressure.
- Once a donor has been evaluated for eligibility for leukapheresis, which includes an apheresis evaluation of the donor’s medical history, physical examination, review of medications, allergies, and laboratory data, and obtained informed consent, he or she will sit comfortably in the donor chair with easy access to the leukapheresis machine. It is important to note that donors are encouraged to drink plenty of fluids and wear loose-fitting clothes to ensure comfort and stamina for the procedure.
- After proper sterilization of the skin, each arm receives a venipuncture for vascular access through peripheral veins such as the antecubital vein, which can be obtained by a 16-gauge (or larger) needle.
- If peripheral access is not accessible, a central catheter can be placed in the subclavian, femoral, or internal jugular vein. Certain catheter technologies have the potential to allow for higher flow rates from a larger lumen and rigid-wall construction, but are mainly seen in a hospital-based, therapeutic leukapheresis setting.
- Once all components are in place, venous flow is set in motion and WBC volume begins to collect through centrifugation, or separation. Once an appropriate amount of whole blood is collected in the bowl or belt chamber of the centrifugation instrument with an anticoagulant, the material is spun at high speeds, 900-1300 rpm, to allow centripetal forces to separate the desired components. Once separated, the WBCs are passed on to a sterilized chamber for collection while the anticoagulated RBCs and plasma are returned to the donor through the second venipuncture site. Collection rates differ for each machine. COBE Spectra has a variable inflow rate of 10-150 mL/min while other machines start off with a general rate of 3-8 mL/min.
- Since blood clots very quickly once outside the body, certain anticoagulants such as sodium citrate and sodium heparin are used to keep the extracorporeal blood from clotting for a smooth return back to the donor. Sodium citrate works by blocking calcium-dependent clotting factors on the cellular level while sodium heparin works similarly to block other important clotting factors from binding to hemoglobin. It is important to note that with sodium citrate as an anticoagulant, hypocalcemia, a condition where the body has too little calcium, may be a potential adverse event due to the reduction of the circulating ionized calcium concentration. Although sodium citrate improves the return of RBCs and plasma to the donor, supplemental calcium may be given during the procedure by IV or oral administration to reduce the risk of hypocalcemia.
- Once the desired volume is collected, the leukapheresis procedure may be discontinued. Most leukapheresis machine have automatic stops once this volume is reached. Exact volume to be obtained is based on exchanges to prevent metabolic homeostatic complications and reach the goal of the procedure (i.e. WBC harvest for research, peripheral leukocyte depletion to a total WBC count below 100,000 μL, etc). A one blood volume exchange can remove 63% of of the desired component while a two blood volume exchange can remove 87% of the desired component. A starting point of two blood volumes (about 10 L of whole blood) for adult donors, of average weight and who tolerate the procedure well, is recommended.
- On average, 600 mL of WBCs are collected during a single leukapheresis procedure, which reduces the donor’s peripheral WBC count by 15-20%. Depending on the goal of the LEUKAPHERESIS GUIDE 11 treatment (therapeutic or donation for research), leukapheresis treatments can be repeated. In a series of studies from 6 medical centers in Taiwan totaling 22 patients, physicians found that 55% of patients needed one treatment, 27% needed two treatments, and 18% needed three treatments to reduce WBC to a goal of under 100,000 μL, a benchmark for hyperleukocytosis and, in some cases, leukostasis.
- Post procedure, donors may feel weak from the WBC depletion, although this was wear off once the body naturally replenishes itself to a desirable homeostatic state and WBC count. Donors are encouraged to have an approved friend or family member present for transportation to and from the facility.
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