US 3654925 A
A blood-collecting tube of the evacuated type containing an anticoagulant receives through normal techniques whole blood to be tested. Thereafter, a cell-collecting tube is interconnected with the blood-collecting tube through the intermediary of a double-ended needle assembly including an external discoidal hub intermediate the ends thereof, such that the interior of both tubes communicate with one another. The tubes with the interconnecting needle assembly are then subjected to centrifugation with the cell-collecting tube being spaced radially outwardly relative to the blood-collecting tube and the axis of rotation. Upon generation of sufficient centrifugal forces, the plasma separates from the heavier constituents with the latter and particularly the blood cells being forced out into the cell-collecting tube and packed therein. The relative capacities of the tubes are such that in the blood-collecting tube only plasma will remain following completion of centrifugation. The needle assembly is then removed from the blood-collecting tube to effectively separate and remove plasma from the remaining constituents of the blood.
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Description (OCR text may contain errors)
United States Patent [151 3,654,925 51 Apr. 11,1972
Holderith  PLASMA SEPARATOR SYSTEM  Inventor: William J. Holderith, Wyckoff, NJ.
 Assignee: Becton, Dickinson and Company, East Rutherford, NJ.
 Filed: Sept. 23, 1969  Appl. No; 860,191
 US. Cl ..128/272, 128/318 M  Int. Cl. ..A61j 01/00  Field ofSearch ..l28/2,2l8 M,218D, 272
 References Cited UNITED STATES PATENTS 1,614,067 1/1927 Heublein ..128/272 1,928,998 10/1933 Kovacs ..128/272 2,342,214 2/1944 Perelson... ..128/272 UX 2,655,919 10/1953 Goodstein et a1. ..128/218 M 2,734,649 2/1956 Callahan et al. ....128/272 X 2,908,274 10/1959 Bujan ....128/272 3,200,813 8/1965 Christakis. ..128/2 3,221,741 12/1965 LeVeen ....128/272 3,490,437 l/1970 Bakondy et a1. ..128/272 X Primary Examiner-Joseph S. Reich Attorney-Kane, Dalsimer, Kane, Sullivan and Smith [5 7] ABSTRACT A blood-collecting tube of the evacuated type containing an anticoagulant receives through normal techniques whole blood to be tested. Thereafter, a cell-collecting tube is interconnected with the blood-collecting tube through the intermediary of a double-ended needle assembly including an external discoidal hub intermediate the ends thereof, such that the interior of both tubes communicate with one another. The tubes with the interconnecting needle assembly are then subjected to centrifugation with the cell-collecting tube being spaced radially outwardly relative to the blood-collecting tube and the axis of rotation. Upon generation of sufficient centrifugal forces, the plasma separates from the heavier constituents with the latter and particularly the blood cells being forced out into the cell-collecting tube and packed therein. The relative capacities of the tubes are such that in the bloodcollecting tube only plasma will remain following completion of centrifugation. The needle assembly is then removed from the blood-collecting tube to effectively separate and remove plasma from the remaining constituents of the blood.
1 Claims, 3 Drawing Figures PLASMA SEPARATOR SYSTEM BACKGROUND OF THE INVENTION In the testing of blood, it is often desired to obtain a sample of blood plasma, the clear, straw-colored liquid left when all formed elements in uncoagulated blood have been removed. To obtain plasma, it is common practice to draw blood into a tube containing an anticoagulant, centrifuge this sample, and remove the supernatant plasma either by decanting (pouring it off) or removing it with an aspirating device such as a pipette or syringe. These removal methods are not entirely satisfactory in that both require the tube to be opened and exposed to the air, thereby risking contamination. The decanting method also risks mixing of the formed elements with the plasma, rendering the plasma unusable. The transfer method is also unsatisfactory in that the sample may be contaminated by the transfer device, and the cost of the transfer device adds extra expense to the determination and analysis.
SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a more effective system and procedure for removing plasma from whole blood after the sample has been centrifuged.
Another object is to provide a device and system of this type which permits the removal of the plasma portion without disturbing the packed red cells thus allowing the use of pure plasma in many tests wherein the presence of formed elements might render the test invalid.
A further object is to provide a system of this type which is essentially closed" in that neither portion of the original sample is exposed to the atmosphere.
BRIEF DESCRIPTION OF THE DRAWING FIG. 3 is a similar longitudinal sectional view showing theblood-collecting tube associated with the cell-collecting tube through the intermediary of the double-ended needle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated blood plasma collecting system includes a blood-collecting tube such as is described in US. Pat. No. 2,460,641 titled Blood Collecting Apparatus, granted Feb. 21, 1949 a cell-collecting tube 12, and an intermediate needle assembly 14 which may be either affixed to the stopper of the cell-collecting tube 12 or be constructed as a separate unattached assembly. Referring initially to the tube 10, it will be noted that a tubular body 16 of essentially cylindrical configuration includes a closed end 18 and an open end 20. Sealing the open end 20 is a penetrable self-sealable stopper 22. In accordance with conventional practice, the stopper 22 cooperates in maintaining a vacuum within the tube 10 which also conveniently receives an anticoagulant for whole blood. The stopper 22 includes an interiorly disposed plug portion 24 and an exterior radially extending flange portion 26 disposed against the open end 20. An exterior conical recess 28 facilitates penetration of the stopper 22 by a pointed needle. The interior of the plug portion 24 includes an inner end 30 forming the base of a truncated conical recess, the conical walls of which serve a funneling function in facilitating the complete removal of the solid constituents of whole blood during centrifugation in a manner to be described in detail below.
The cell-collecting tube 12, on the other hand, includes a tubular body portion 32 having a closed end 34 and an open end 36 across which a stopper 38 extends in sealing relationship. In this connection, the capacity of tube 10 relative to tube 12 should be such that all of the heavier constituents of the separated blood are accommodated and only a minimum amount of plasma will be present. The stopper 38 includes the usual plug portion 40 and flange portion 42. This stopper is also adapted to be penetrated and self-scalable. For purposes of this invention, the tube 12 need not be evacuated and may possess essentially the same capacity as tube 10, but is preferably smaller in volume.
The needle assembly 14 is provided with a double-ended cannula 44 having bevel pointed ends 46 and 48. A hub 50 is affixed to a cannula 44 intermediate its ends. The needle assembly 14 may conveniently form a part of the tube 12 as shown in FIG. 2 or be an independent assembly but necessary component or part of the plasma-collecting system of this invention.
In use, the blood-collecting tube 10 is employed together with a double-ended hypodermic needle (not shown) to collect a sample of venous or arterial blood in a manner similar to that disclosed in US. Pat. No. 2,460,641. As soon as convenient thereafter, the cell-collecting tube 12 is attached to tube 10 by inserting the bevel end 46 of cannula 44 through stopper 22, such that the parts assume the position illustrated in FIG. 3. The assembly is then placed in a centrifuge (not shown) and held therein in such a manner that centrifugal forces will act along the common axis of the assembly from the blood-collecting tube 10 towards the cell-collecting tube 12. The centrifuge is run for a sufficient period of time to enable the generated centrifugal forces to force the liquid in the tube 10 to displace the air in tube 12 and eventually urge the solid constituents of the blood and particularly the cells thereof to be packed within the tubular body 32 of cell-collecting tube 12 as shown in FIG. 3. The plasma passes through the cannula 44 into the tube 10 with a minor portion of the plasma remaining in tube 12. When centrifugation is complete the assembly is removed and the tube 10 separated from the needle assembly l4, and consequently the tube 12. Remixing of plasma and the fomied elements or solid constituents of the blood is prevented by removal of the connecting cannula, while the assembly is held vertically and contamination is prevented by maintaining a closed system which can be made entirely sterile if desired.
As stated in the foregoing, the conical recess 30 of stopper 22 avoids entrapment of red cells or other solid constituents in the upper tube 10 during centrifugation. It is also preferred that the bevel end 46 of cannula 44 not protrude into the conical recess 30 for this same reason but be disposed in the cylindrical extension 32 of this recess. By the same token, the bevel end 48 of cannula 44 should be disposed within the tube 12 and related to its internal capacity such that this bevel end be disposed in the plasma portion and not protrude into the packed cell portion following centrifugation.
In an alternate embodiment of the plasma separator system, tubes 10 and 12 may be of substantially equal size and capacity. With this in mind both tubes may be utilized to collect blood. However, the needle assembly 14 does not form part of tube 12 and is a separate unit which is thereafter employed to join the tubes together. This assembly is then centrifuged and the blood separated. The plasma and cells are then isolated one from the other and collected for the intended purposes.
Thus, the aforenoted objects and advantages are most effectively obtained. Although several preferred embodiments of the invention have been disclosed and described in detail herein, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of his appended claims.
l. A plasma separating system comprising in combination a blood-collecting tube comprising a tubular body having a closed end and an open end fitted with a needle penetrable stopper; said stopper extending across and covering the open end thereof; said blood-collecting tube having whole blood disposed therein; a cell-collecting tube comprising a tubular body having a closed end and an open end fitted with a stopper; said stopper extending across and closing the open end thereof; said cell-collecting tube having a volume such that the cells obtained from separating whole blood disposed in the blood-collecting tube would fill a major portion of the cell-collecting tube; a double-ended needle assembly mounted on the blood-collecting and cell-collecting tubes; said doubleended needle assembly having cannula and a hub disposed between the ends thereof, each end of the cannula having a beveled pointed end so as to penetrate through the stopper of the blood-collecting tube and the stopper of the cell-collecting tube so that the interior of each of said tubes is in fluid communication with each other whereby the cells contained in the whole blood are adapted to be separated by external forces on said system and when separated will substantially till a major portion of the cell-collecting tube by passing through the cannula of the double needle assembly and, at the same time, the liquid plasma portion of the whole blood will fill at least a portion of the blood-collecting tube, and said hub being adapted to engage with an exterior surface of said stopper on said cellcollecting tube such that the pointed end of the needle associated with the cell-collecting tube is disposed interiorly thereof and short of the cells of the blood collected therein following said separation.