Читать книгу Transfusion Medicine - Jeffrey McCullough - Страница 188

The plasma collection and fractionation industry in the United States developed during the 1960s using manual plastic bag methods for plasma collection by plasmapheresis. Today, virtually all source plasma collected in the United States for fractionation into derivatives (see Chapters 2 and 5) is obtained by semiautomated instrument plasmapheresis. It has been estimated [126] that about 28 million liters of plasma are fractionated annually in the world (see Chapter 2). Most plasma used as fresh frozen plasma (FFP) is obtained from whole blood, but the increasing flexibility of some apheresis instruments makes it possible to obtain plasma for FFP as a by‐product of platelet or red cell apheresis. There are no data on the number of plasma products produced in this manner. Apheresis plasma contains greater activities of factor V, factor VIII, factor IX, and factor XI, prothrombin fragments 1 and 2, and platelet factor IV compared with recovered plasma (see Chapter 4 and Burnouf [126] and Runkel et al. [127]). Thus, apheresis appears to produce plasma with a higher quality, although the clinical significance of this is not established.

Source plasma is the starting material for the further manufacture of some diagnostics and plasma “derivatives.” Derivatives are described in more detail in Chapter 2, and the selection and medical evaluation of plasma donors are described in Chapter 4. Plasmapheresis was done using sets of multiple plastic bags and involved separation of the blood from the donor such that there was a chance for return of red cells to the incorrect donor. Source plasma is now collected by semiautomated instruments that require less operator involvement, while producing larger amounts of plasma at a reasonable cost. Usually one venipuncture is used, and the system can be set up in about 5 minutes. This includes loading the disposable plastic set into the instrument, connecting the anticoagulant and solution bags, recording appropriate data, and placing the collection bags. The venipuncture area is prepared as for whole blood collection (see Chapter 4), and the venipuncture is done using the needle integral with the disposable plastic set used for the procedure. The operator then activates the instrument, and blood flow is initiated by the pumps in the instrument. Anticoagulant is metered into the blood flowing into the instrument in the proper ratio, and the centrifuge bowl is filled until the optical sensor detects the red cell interface and stops the inflow of blood. During this filling phase of the cycle, the plasma has been diverted into the collection bag. After the plasma–cell interface has reached the detector, the blood flow is reversed and the red cells are pumped from the bowl back to the donor. The cycle is then repeated until the desired amount of plasma is obtained. Usually about 500 mL of plasma can be obtained in about 30 minutes [128]. These instruments might be used to produce FFP but are not used extensively to produce source plasma.

The Fresenius Kabi Autopheresis C (Auto‐C) and Aurora plasmapheresis instruments operate on a different principle from the Haemonetics devices. The Autopheresis C combines filtration and centrifugation to separate blood in a smaller chamber (and possibly more efficiently). The instrument setup and donor preparation are the same as described for the Haemonetics systems and for whole blood collection. In these systems, blood is withdrawn from the donor into a closed, disposable plastic set with a total extracorporeal volume of about 165 mL. Blood separation occurs in a small, 7‐mL (Auto C or Aurora) or 15‐mL (Aurora Xi) cylinder that is part of the system. A magnet causes rotation of the cylinder inside a larger compartment. The cylinder is composed of a membrane, and as the cylinder rotates, plasma moves peripherally through the membrane, thus providing the filtration part of the separation system. The system does not operate in a continuous‐flow manner; blood is returned intermittently to the donor through the single venipuncture and the process is repeated. The Auto‐C system collects about 500 mL of plasma in about 30 minutes [129, 130]. The Aurora Xi is slightly more efficient; however, both systems are used extensively for the production of source plasma for further manufacture of plasma derivatives.