IL47945A - Method and apparatus for the separation of cryprecipitate separation of cryoprecipitate from blood plasma - Google Patents

Description

47945/2 at fioo ea m*np-_?pwa m-ten jpnni n»*w Method and apparatus for the separation cryoprecipitate from blood plasrna BAXTER TRAVEUOIi LABORATORIES, INC.

C¾- 45657 BACKGROUND OF THE INVENTION This application relates to an improved blood collection apparatus and method in which the separation of Factor VIII rich cryoprecipitate from the remainder of the blood plasma is facilitated in an improved manner and in which the yield of Factor VIII rich cryoprecipitate is improved.

Many thousands of units of blood are collected each year in multiple bag blood collection systems comprising several blood compatible, sealed bags connected together with blood compatible tubing.

In a typical operation, a donor needle is inserted into the vein of a patient. This needle is connected by suitable tubing, such as vinyl tubing, to a first blood bag containing a small amount of conventional blood cell preservative, such as ACD or CPD. The blood is allowed to fill the first blood bag of the system, the donor needle is withdrawn from the patient, and the tubing connecting the needle to the bag is sealed. Following this, the blood collection system is cen-trifuged to cause the blood cells to settle and separate from the plasma. The plasma is then expressed through another tubing into a second blood bag, while the cells remain in the first blood bag.

Optionally, platelets may be harvested at this stage by a second centrifugation.

The plasma in the second blood bag is then frozen, either by refrigeration or by immersion in a mixture of dry ice and ethanol or a similar solvent.

After this, the frozen plasma is conventionally allowed to thaw slowly and then is centrifuged once again to settle solid material in the cold, thawed plasma. This solid material is known as Factor VIII rich cryoprecipitate.

After the conventional centrifuging, the plasma, which is now cryoprecipitate-poor, is expressed through tubing into a third blood bag for use, leaving behind the Factor VIII rich cryoprecipitate. This Factor VIII rich cryoprecipitate is the source of an important therapeutic agent for arresting the symptoms of a common type of hemophilia.

In accordance with this invention, an apparatus and a method of using the same is provided which permits the collection of increased yields of Factor VIII rich cryoprecipitate without the use of a second centrifuging step and which provides substantial savings in time and effort when compared with the present technique for obtaining Factor VIII rich cryoprecipitate.

DESCRIPTION OF THE INVENTION This improved blood collection system incorporates a plurality of blood compatible, sealed bags connected together with blood compatible conduit means. Blood collection means, such as a phlebotomy needle connected to vinyl plastic tubing, communicates with the interior of the first of the bags. Accordingly, the blood is collected into the first bag and centrifuged to remove blood cells. The plasma is then expressed through the appropriate connecting conduit from the first bag to the second bag. Optionally, platelets may be harvested by another centrifugation in which the platelets remain in the second bag and the plasma is passed on to an additional bag. The bag containing the plasma is sealed, typically by heat sealing or clamping of the conduit, and frozen to form the Factor VIII rich cryoprecipitate.

For the final separation step, it is preferred to allow the frozen plasma to thaw slowly, permitting the thawed plasma to pass through the filtering means and out of the bag into another storage container as it melts. The thawing process typically can be performed between 2° and 20°C. (preferably between 2-5°C, ) for maximum yield of cryoprecipitate. The frozen bag is hung up and allowed to slowly melt and drain through the filtering means and bag outlet into another container. The thawing and draining process takes approximately 18 to 24 hours at 5°C. in a Fenwal blood bag containing one unit of blood plasma.

After the drainage is completed, the bag containing the Factor VIII rich cryoprecipitate can be sealed and separated from any remaining attached bags. One unit of cryoprecipitate is obtained (often with an increased yield of Factor VIII). Likewise, one unit of cryoprecipitate-poor plasma passes into the storage receptacle, which is usually the third or fourth bag of the system.

The filtering means used in the separation of the cryoprecipitate from the plasma must exhibit certain characteristics. It must pass the cryoprecipitate-poor plasma while retaining the Factor VIII rich cryoprecipitate. Cryoprecipitate-poor plasma can pass through a conventional screen type or membrane filter with a 2 micron pore. However, the cryoprecipitate clogs present-day screen or membrane filters. Therefore, part of the multiple blood bag system must account for and solve the clogging problem. Accordingly, "filtering means" as used herein means a filter which can pass the cryoprecipitate-poor plasma while retaining the Factor VIII rich cryoprecipitate and which solves the clogging problem.

Presently, the filtering means most effective in exhibiting - n cons s s o rous, granu ar or s n ere ma er a s, presse , wound, fired, or otherwise bonded into a tortuous maze of flow channels. " (Millipore's High Volume Pharmaceutical and Biological Filtration, (1972) page 2. ) Because a depth filter is a three-dimensional irregular maze of material, it has a large internal surface area on which cryoprecipitate can be caught. Therefore, it will not readily become clogged as plasma is being passed through the filter.

Because a depth filter is a three dimensional maze of material, its filtering capacity cannot be described in terms of the size of the particles it will pass. Rather, a depth filter' s filtering capacity is defined experimentally in terms of the percentage of particles of a certain size which will pass through it. It follows that outside factors will affect the filtering rate of depth filters. Flow rate, pressure, and particle adhesiveness are three such factors.

The presently preferred filtering means used in the improved blood collection system of this invention is a polyurethane open cell foam depth filter.

The specific embodiment described below illustrates one exemplary means for embodying the invention of this application. A "triple" bag system is shown bearing some similarity to the currently available Fenwal triple bags, but other structures such as single, double, and quadruple bag systems may be used if desired, modiFied in accordance with this invention.

In the drawings: Figure 1 is a plan view of a triple bag blood collection system, utilizing the invention of this application, with a portion broken away for showing construction detail.

Figure 2 is a sectional view taken along line 2 -2 of Figure 1.

Referring to the drawings, a blood collection system is shown comprising blood compatible, sealed blood bags 10, 12, 14, connected together with blood compatible conduit means 16, 18, which are shown to be vinyl plastic tubes. As stated above, any of the overall specific details of design of bags 10, 12, 14, and their respective conduits 16, 18, are well known, and similar bags made of vinyl plastic are commercially available at the present time.

A blood collection needle 20, conventionally sheathed with a needle protection cover 22, is shown to be connected in conventional manner by vinyl plastic tubing 24 to the interior of the first bag 10.

Vinyl plastic tubing 16 and flexible connector tube 17 provide communication between first bag 10 and second bag 12, while vinyl plastic tubing 18 and similar connector tube 19 provide connection between second bag 12 and third bag 14. Each of the three bags carries a pair of outlet ports 26 which are surrounded with conventional rup-turable sheaths 28, specifically shown to be the design presently utilized in the Fenwal blood bags.

In accordance with this invention, filtering means is located in the interior of second bag 12, being positioned to cover outlet port tube 32 of bag 12. Outlet port tube 32, which is generally made of plastic, in turn communicates through tube 18 with the interior of bag 14.

Filtering means 30 may be polyurethane open cell foam depth filter sold under the brand name Scott Felt by the Scott Paper This material is a thick, sheet-like material, the grade specifically used herein being approximately 3/ 8 inch thick. The material, as originally made, has approximately 100 pores per inch, but then is compressed to l/8th of its thickness, and heat set so that the material does not re-expand significantly after release from the compression.

Referring also to Figure 2, a slit 34 is shown to be cut longitudinally in filtering means 30. Port tube 32 is positioned within the slit. Port tube 32 and filtering means 30 are positioned as shown in Figure 1 between the pair of plastic sheets 35, 37 that makes up blood bag 12, and the periphery 36 of sheets 35, 37 is heat sealed together, with the bottom 38 of filtering means 30 between them, so that periphery 36, bottom 38 of filtering means 30, and outlet port tube 32 all are sealed together into a unitary, sealed mass. Both ends of outlet port tube 32 protrude from opposite sides of the heat sealed periphery 36, for fluid communication therethrough.

Tube 19 is connected to port tube 32 by means of sleeve 40, which may be made of plastic or the like. Sleeve 40 defines a diaphragm 42 which blocks fluid flow out of bag 12 through port tube 32 until the diaphragm is ruptured by pointed tubular cannula 44, which is constructed in a manner similar to the diaphragm rupturing system of U. S. Patent No. 3, 110, 308, and is retained in a bore of connector tube 19, since the bore of tube 18 is preferably too smal l to receive the cannula. Alternatively, tlie system for ruptu ring diaphragm 42 can bo similar to I' . S. Patent No. 3, 685, 795, or any other conventional diaphragm ruptui-ing system may be used.

A similar sleeve 40, having diaphragm 42, communicates with the interior of first blood bag 10, being retained with the corresponding heat sealed periphery 36 of bag 10 for leak free communication with the interior of the bag. Another hollow cannula 44, retained in connector tube 17, is present for the same function of opening diaphragm 42.

Sealed tubes 46 on bags 12 and 14 are ports used in the sterilization of the bags, to provide venting of the bags during and after the sterilization process. Thereafter the tubes are sealed as shown.

Identical serial numbers may be placed on vinyl tubing 16, 18 and 24 in the manner of Bellamy U. S. Patent No. 2, 896, 619 for identification of the respective bags after they have been separated from each other, and for analysis of small samples of the contents of the bags.

Hangers 48 at the bottom of bags 10 and 14 permit inversion of the bags on an I. V. pole for conventional administration of the respective bag contents to a patient.

Accordingly, the triple bag blood collection system of Figure 1 can be utilized by first obtaining a unit of fresh blood by conventional venipuncture with needle 20, and collection of a unit of blood into bag 10. Following such collection, donor tube 24 may be sealed by clamping, or by heat sealing in a HEMATRON heat sealing device, sold by the Fenwal division of Travenol Laboratories, Inc. Bag 10 contains a small amount of conventional blood cell preservative such as ACD or CPD preservative solution.

Following the blood collection, and sealing of tube 24, the blood bag system is centrifuged, to cause the blood cells in the accomplished, cannula 44 of bag 10 is moved forwardly to rupture diaphragm 42 by manual manipulation of flexible connector tube 17 to push cannula 44 through the diaphragm. The plasma can then be carefully expressed through tube 16 into the second bag 12, leaving the packed cells behind in bag 10.

Tube 16 is then usually severed after clamping or heat sealing, and bag 10 may be removed from the system, with its packed cells being preserved and stored in a conventional manner until needed for use.

The remaining bags of the system are then placed in a freezing environment, for example an ethanol-dry ice bath or mechanical refrigeration, to freeze the plasma in bag 12 to the solid state. After the plasma has solidly frozen, the cannula 44 associated with bag 12, and an appropriate portion of flexible connector tube 19, are warmed with the fingers or the like to permit the cannula to be advanced to rupture its associated membrane 42. This opens communication between bag 1 and tube 18. Bag 12 is then hung (if desired by means of holes 54) in a refrigerator at a temperature above the plasma freezing point. The preferred temperature is approximately 5°C. Bag 14 is placed at a position vertically below bag 10 to receive cryoprecipitate-poor plasma, as the plasma melts, on a drop by drop basis. The melting plasma in bag 12 passes through filtering means 30 and outlet port tube 32, and accordingly through tubes 18 and 19 into bag 14.

After the plasma has thawed completely and has been filtered into bag 14, tube 18 may be sealed in a manner previously described, and severed to permit bag 14 and the cryoprecipitate-poor plasma to be removed for storage until needed for administra An abundant yield of Factor VIII rich cryoprecipitate remains captured on the filtering means 30 within bag 12. This material may be frozen for storage if desired.

When the cryoprecipitate is needed for use, it may be dissolved by adding about 10 cc. of sterile physiological saline solution, generally at room temperature, to the interior of bag 12. This may be done by opening one of the rupturable sheet closures 28 of bag 12 and inserting into the exposed outlet port 26 a medication injection site of the type currently sold by the Fenwal Division of Travenol Laboratories, Inc. The saline solution is then added through the medication injection site into the bag with a syringe and injection needle. The filtering means 30 is then manipulated and washed with the solution in the bag until all of the cryoprecipitate is dissolved in the solution. Thereafter, the bag is inverted so that the outlet ports 26 point downwardly, and the saline solution, with the dissolved cryoprecipitate, is withdrawn from the bag by means of the syringe needle.

Filtering means 30 is advantageously placed on the side of the bag opposite from the outlet port 26 used in this operation, since the bag may then be inverted with the outlet port pointed downwardly with the filtering means 30 out of contact with and above the liquid. The filtering means may then be manually squeezed to remove essentially all of the cryoprecipitate solution from it.

Claims (1)

1. THAT WHICH IS CLAIMED IS: Claim 1. In a blood collection system which comprises blood compatible container means, including a blood compatible, sealed container for receiving blood plasma, the improvement comprising a filtering means within said plasma -receiving container, said filtering means being positioned to cover an outlet from said plasma-receiving container, whereby blood plasma in said plasma-receiving container may be frozen, and then thawed to form Factor VIII rich cryoprecipitate in said plasma-receiving container, and cryopre cipitate -poor plasma may be transferred from said container through said filtering means and outlet, while said cryoprecipitate is held in said second container by said filtering means. Claim 2. The blood collection system of Claim 1 in which said filtering means is a depth filter. Claim 3. The blood collection system of Claim 2 in which said depth filter is an open cell foam filter. Claim 4. The blood collection system of Claim 3 in which said open cell foam filter is made of polyurethane. Claim 5. In a multiple bag blood collection system which comprises a plurality of blood- compatible, sealed bags connected together with blood compatible conduit means, and blood collection means communicating with the interior of a first of said bags, the improvement comprising: Filtering means positioned within a second of said bags to cover an outlet from said second bag, whereby blood plasma, expressed from said first bag into said second bag, may be frozen from said second bag through said filtering means and outlet, while said cryoprecipitate is retained in said second bag by said filtering means. Claim 6. The blood collection system of Claim 5 in which said filtering means is a depth filter. Claim 7. The blood collection system of Claim 6 in which said depth filter is an open cell foam filter. Claim 8. The blood collection system of Claim 7 in which said open cell foam filter is made of polyurethane. Claim 9. The blood collection system of Claim 5 in which said outlet of the second bag is in fluid communication with a third bag, for receiving cryoprecipitate-poor plasma in aseptic manner. Claim 10. In the method of blood collection which comprises passing blood plasma containing Factor VIII into a blood compatible sealed container; freezing said blood plasma within said sealed container to cause the precipitation of Factor VIII rich cryoprecipitate; and thawing said blood plasma, the improvement comprising passing the thawed blood plasma, under conditions to prevent the substantial redissolving of said cryoprecipitate, through filtering means, said filtering means being positioned within said container to obstruct an outlet therefrom, whereby cryoprecipitate-poor plasma is transferred from said container, and said cryoprecipitate is retained on the filtering means within said container. Claim 11. The method of Claim 10 in which said filtering means is a depth filter. Claim 12. The method of Claim 11 in which said depth filter is an open cell foam filter. Claim 14. The method of Claim 10 in which said frozen blood plasma is allowed to slowly thaw at a temperature below 20°C, while the plasma is allowed to pass through said filtering means promptly as it melts and out of said bag outlet. Claim 15. The method of Claim 14 in which said filtering means is a depth filter. Claim 16. The method of Claim 15 in which said depth filter is an open cell foam filter. Claim 17. The method of Claim 16 in which said open cell foam filter is made of polyurethane. Claim 18. The method of Claim 10 in which said frozen blood plasma is allowed to thaw at 2 - 5°C. Claim 19. The method of Claim 18 in which said filtering means is a depth filter. Claim 20. The method of Claim 19 in which said depth filter is an open cell foam filter. Claim 21. The method of Claim 20 in which said open cell foam filter is made of polyurethane. Claim 22. The method of Claim 10 in which said cryoprecipitate -poor plasma is transferred to another blood- compatible sealed bag through a blood compatible conduit. Claim 23. The method of Claim 22 in which physiological saline solution is thereafter added to said second bag, to redissolve the cryoprecipitate, and said cryoprecipitate containing solution is thereafte r- removed from said second bag. Claim 24. The method of Claim 23 in which, after the cryoprecipitate is redissolved, any cryoprecipitate caught in the Claim 25. The method of Claim 2k in which the removal of cryoprecipitate from the filter is accomplished by washing the filter with a saline solution. Claim 26. The method of Claim 2k in which the removal of cryoprecipitate from the filter is accomplished by squeezing the filter. Claim 27. Blood plasma to Factor VII I rich cryoprecipitate and cryoprecipitate-poor plasma converting apparatus comprising: a plasma freezing sealed container having means for allowing blood plasma to be charged therein; a cryoprecipitate-poor plasma receiving sealed container; means defining a flow path between said containers; and filter means operably coupled thereto so as to filter plasma transferred through said flow path between said pair of containers, whereby blood plasma may be charged into and frozen in said plasma-freezing container and then thawed so form Factor V! ll rich cryoprecipitate and cryoprecipitate-poor plasma may be transferred to said cryopreci itate-poor plasma receiving container through said filter means. Claim 28. A method of processing blood plasma containing Factor VIII into Factor VI M rich cryoprecipitate and cryoprecipitate-poor plasma using a filter comprising the steps of (a) freezing the blood plasma containing Factor VIM ; (b) thawing the frozen blood plasma in such a manner so as to substantially prevent cryoprecipitate from returning into solution; (c) filtering in the filter and separating a substantial portion of the thawed plasma obtained in step (b) to obtain separated volumes of cryoprecipitate-poor plasma and Factor VI II rich plasma. Claim 29. The method of claim 28 wherein after a substantial separation has occurred a small quantity of separated cryoprecipitate-poor plasma is re-introduced into the separated Factor VII I rich cryoprecipitate to form an easily handled and storable Factor VII I rich Claim 30. The method of Claim 28 wherein after substantial separation has occurred a small quantity of saline solution is introduced into the separated Factor VIM rich cryoprecipitate to form an easily handled and storable Factor VI II rich cryoprecipitate solution