Surgery – Blood drawn and replaced or treated and returned to body – Constituent removed from blood and remainder returned to body
Reexamination Certificate
1999-09-09
2004-06-01
Sykes, Angela D. (Department: 3762)
Surgery
Blood drawn and replaced or treated and returned to body
Constituent removed from blood and remainder returned to body
C604S004010, C604S005010, C210S085000, C210S195100
Reexamination Certificate
active
06743192
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apheresis machine and a method for producing blood products using the same. More specifically, the present invention relates to customizing a collection process of whole blood during a cycle for improving cycle efficiency in an apheresis machine and production efficiency of blood products, and for lowering the level of contamination by white blood cells.
Apheresis is a procedure in which whole blood is separated into its various blood components, i.e., a higher density component such as red blood cells, at least one intermediate density component such as platelets and white blood cells, including lymphocytes and granulocytes, and a lower density component such as plasma, for collecting a desired blood component or components. Various methods are available for conducting apheresis, among which an intermittent blood flow method, according to which whole blood is intermittently processed with the use of centrifugation, is prevailing.
Among various blood component products obtainable through apheresis, the demand for concentrated platelet products is rapidly growing. This is particularly because, with the improvement in cancer therapy, there is a need to administrate more and more platelets to patients with lowered hemopoietic function. Platelets are fragments of a large cell located in the marrow called a megakaryocyte and primarily contribute to hemostasis by performing aggregation function, although they also have a role in tissue healing. Normal platelet counts are 150,000-400,000/mm
3
in the adult. Platelet counts under 20,000/mm
3
can cause various troubles such as spontaneous bleeding.
Platelets have a short half-life of 4-6 days and the number of donors is limited. Therefore, in producing concentrated platelet products, it is important to harvest platelets from the whole blood supplied by a donor at a maximum yield and in a required amount. Further, it is known that the contamination of concentrated platelet product by white blood cells can lead to serious medial complications, such as GVH reactions and, therefore, it is also very important to keep the level of contamination by white blood cells as low as possible, while efficiently collecting platelets. To this end, various excellent techniques have been developed. For example, according to the so-called “surge” technology developed by the assignee of the present application, after whole blood is collected and concentrically separated within a centrifuge into higher density, intermediate density and lower density components (so-called “draw” step) and plasma is harvested, the plasma is supplied through the centrifuge at a surge flow rate, that is, a flow rate that increases with time. By performing the surge, platelets can be preferentially displaced from the intermediate density components, which exist as a buffy coat mainly comprising a mixture of platelets and white blood cells, and concentrated platelet products can thereby be produced at an increased yield. Further, in Japanese Patent No. 2,776,988 (PCT/US94/01107) also owned by the assignee of the present application, a success in the improvement of separation between platelets and white blood cells was achieved by recirculating plasma at a constant rate through the centrifuge for a short period of time (so-called “dwell” step) so as to arrange platelets and white blood cells, which have close specific gravities, before displacing platelets from the centrifuge using the surge technology. In the common intermittent blood flow method, after harvesting a desired component or components, the residual blood components mostly comprising red blood cells are returned to the donor (so-called “return” step).
Usually, about 500 ml of whole blood is processed during one cycle which comprises the above-mentioned successive steps. This amount is based on 15% or less of the total amount of blood in humans and, if more than this amount is taken out of the body at once, the donor may suffer from blood pressure lowering or dizziness. This also means that there is a limit in the amount of a concentrated platelet product that can be harvested from one cycle and, in normal apheresis, a cycle which may require about 15 minutes is successively conducted for three to five times. The number of cycles is determined based on information previously obtained on the donor and his or her whole blood, for example, the donor's sex, height and weight, the number of cells in the whole blood, hematocrit value and the like. Typically, the amount of a concentrated platelet product that can be harvested per cycle is determined based on this information, and the number of cycles is selected so as to satisfy a target number of platelets.
As is well-known, concentrated platelet products are administered or traded on the basis of the number of platelets contained therein, i.e., number of units. For example, according to the Pharmaceutical Affairs Law in Japan, the presence of 1×10
11
platelets in a bag is prescribed as 5 units, and the products are used in a discrete number of units, 5, 10, 15 or 20. Accordingly, for example, 11 units and 14 units are both regarded as only 10 units. However, in actual apheresis, an attempt to produce a 10-unit concentrated platelet product does not always result in the desired product. Specifically, assume, for example, that it has been determined from previously obtained information that a 4-unit concentrated platelet product may be produced from one cycle. In this case, while 2.5 cycles should be sufficient for producing a 10-unit concentrated platelet product, it is actually necessary to perform 3 cycles because number of cycles must be an integer, resulting in 12 units of platelets contained in a bag. This presents a problem in terms of efficient production of concentrated platelet products. Further, even if 3.5 units is to be produced from one cycle, in which case 3 cycles theoretically result in 10.5 units, i.e., a 10-unit concentrated platelet product, the operator tends to select 4 cycles for the sake of certainty because the number of actually harvestable platelets may vary. This causes a problem that the number of platelets actually present in a bag tends to exceed the number of units indicated on the bag. In such a case, excessive platelets are collected from a donor, and the time needed to collect blood becomes unduly long. This also presents a problem in securing the safety of a donor. It is to solve these problems that the present invention is directed.
SUMMARY OF THE INVENTION
In accordance with the present invention, the volume of whole blood to be processed in a centrifuge during a “draw” step is variably controlled in response to at least one characteristic associated with the whole blood collected or to be collected from a donor. Specifically, in accordance with the present invention, a process volume of whole blood is increased or decreased so as to be customized with respect to each individual apheresis, so that the volume of an intermediate density blood component to be actuary harvested, in particular the number of platelets, becomes substantially equal to a desired number of units. The characteristics of whole blood are typically the number of platelets and hematocrit value, but the total amount of whole blood, which can be calculated based on the sex, height, weight and the like of a donor, as well as other characteristics, can also be considered. In addition, in case the separation of a desired number of white blood cells should be sought, the present invention is equally applicable.
In a draw step, using a first pump such as a peristaltic pump, whole blood is collected into a centrifuge from a donor directly, or after once pooled in a container such as a bag. The centrifuge may, for example, be a standard Latham bowl as described in US Pat. No. 3,145,713 (the contents of which is hereby incorporated by reference), has an inlet port and an outlet port and separates the collected whole blood into each component. In a draw step, it has been conventional to recirculate separ
Kawamura Masahiro
Sakota Koichiro
Deak Leslie
Sykes Angela D.
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