Abstract:
The invention provides a syringe for preventing anemia resulting from withdrawal of blood from a patient for analysis, the syringe including a cylindrical tube having a nozzle at its lower end to which a needle is attachable; a piston disposed within the tube and apiston handle protruding from the upper end of hte tube; the syringe being further adapted to a be placed in a centrifuge for separating blood drawn from the patient into supernatant plasma component and a packed-cells component, and further comprising means for separating or removing at least a portion of teh plasma, thereby facilitating the injection of the packed-cells back into the patient The invention also provides a method for preventing anemia resulting from the withdrawal of blood from a patient for analysis.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a method for preventing anemia in patients, specifically, in premature infants, and to a syringe to be used in the method. More particularly, the invention concerns a combined syringe and blood sampling and centrifuge device and to a method for drawing blood from infants for analysis while preserving the erythrocytes. 
   BACKGROUND OF THE INVENTION 
   One of the main reasons for anemia in premature infants is blood withdrawal from them for diagnostic purposes. During their first days of life, infants weighing less than 1500 grams, whose blood volume is less than 120 ml, are often subjected to blood withdrawal, as a result of which they inevitably have to be transfused with packed-cells. Some infants receive the equivalent of a double- or triple-volume red cell exchange transfusion as a result of blood sampling for laboratory tests. The premature infants are exposed to all of the side effects of blood transfusions, including infections due to agents transmitted by blood (CMV, HIV, hepatitis), volume overload, mechanical erythrocyte injury, alloimmunization, and more. 
   DISCLOSURE OF THE INVENTION 
   It is therefore a broad object of the present, invention to overcome the above-mentioned problems and to provide a method for blood withdrawal from infants that will prevent anemia, and a combined syringe and blood sampling and centrifuge device for use in that method. 
   The principle behind the invention is to draw the blood through an arterial or venous line, to spin it as a bedside procedure, to remove the plasma for laboratory analysis and to administer the erythrocytes back to the patient through the same arterial or venous line. The procedure is carried out by the same syringe, without transferring the whole sample or its components (plasma and packed-cells) to any additional tube or syringe. 
   Thus, the invention provides a syringe for preventing anemia resulting from withdrawal of blood from a patient for analysis, the syringe comprising tube having a nozzle at its lower end to which a needle is attachable, a piston disposed within the tube and a piston handle protruding from the upper end of the tube; the syringe being further adapted to be placed in a centrifuge for separating blood drawn from the patient into a supernatant plasma component and a packed-cells component, and further comprising means for separating or removing at least a portion of the plasma, thereby facilitating the injection of the packed-cells back into the patient. 
   The invention also provides a syringe for preventing anemia resulting from withdrawal of blood from a patient for analysis, the syringe comprising a syringe body having, at its lower end, a nozzle to which means for connection to a patient&#39;s blood vessel are attachable; a hollow, cylindrical piston rod slidably disposed in the syringe body and carrying, at its lower end, a piston sealingly fitting the syringe body, the piston rod having a gripping disk at its upper end; a plasma vessel disposed within and slidingly fitting the hollow piston rod, the lower end of the vessel being closed and carrying a hollow needle through which a liquid can enter the vessel; wherein, by pulling up the piston rod, whole blood from the patient is drawn into the syringe body, the whole blood then being separated by centrifuging into a plasma component and a packed-cells component, and wherein, subsequently, by applying force to the upper, protruding end of the plasma vessel, the hollow needle is caused to perforate the piston, whereupon pushing down the piston rod causes the separated plasma component to be forced through the needle into the plasma vessel. 
   The invention further provides a method for preventing anemia resulting from the withdrawal of blood from a patient for analysis, the method comprising providing a syringe as described herein and affixing a needle to its nozzle; drawing blood from the patient; removing the needle or covering it and/or the nozzle with a valve; introducing the syringe into a centrifuge and centrifuging the blood sample, causing the blood to be divided into a supernatant plasma component and a packed-cells component; removing at least a portion of the supernatant plasma component from the syringe; removing the valve from the nozzle and needle; affixing a new needle to the syringe, and injecting at least a portion of said packed-cells component back into the patient. 
   The invention still further provides a method for preventing anemia resulting from the withdrawal of blood from a patient for analysis, the method comprising providing a syringe as described herein and affixing means for connection to a blood vessel of the patient; drawing blood from the patient; removing the means for connection to a blood vessel of the patient; closing the nozzle by means of the stopper; introducing the syringe into a centrifuge and centrifuging the blood sample, thus causing the blood to be divided into a supernatant plasma component and a packed-cells component; removing the syringe from the centrifuge and removing the lock means from the piston rod; removing the safety tab from the upper end portion of the plasma vessel and pushing down the vessel to perforate the piston; pushing the piston rod until the piston reaches the interface between the supernatant plasma component and the packed-cells component, and withdrawing the plasma vessel and performing analysis of the plasma. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood. 
     With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
     In the drawings: 
       FIGS. 1 and 2  are schematic, cross-sectional views of a first embodiment of a syringe according to the present invention, illustrating its two states of operation; 
       FIGS. 3 and 4  are schematic, cross-sectional views of further embodiments of a syringe according to the invention; 
       FIGS. 5A–5C  schematically illustrate an embodiment of a piston arrangement for the embodiment of  FIGS. 6A–6F ; 
       FIGS. 6A–6F  are schematic cross-sectional views of a syringe according to the invention, utilizing the piston arrangement of  FIGS. 5A–5C , showing different states of operation; 
       FIG. 7  is a semi-exploded perspective view of yet another embodiment of the syringe according to the present invention; 
       FIG. 8  is a cross-sectional view of the embodiment of  FIG. 1 ; 
       FIG. 9  is an enlarged view of detail A in  FIG. 8 ; 
       FIG. 10  is a perspective view of the plasma vessel and its attachments; 
       FIG. 11  represents the syringe prior to centrifuging and prior to the mounting of a safety lock, and 
       FIG. 12  is a cross-sectional view showing the syringe after centrifuging and perforation of the piston. 
   

   DETAILED DESCRIPTION 
     FIGS. 1 and 2  illustrate a first embodiment of a syringe  2  for preventing anemia due to frequent withdrawal of blood for analysis, especially in premature infants. The syringe  2  comprises a cylindrical tube  4  having a nozzle  6  at its lower end to which a needle  8  is attachable, a piston  10  to which is affixed an operating handle  12  protruding from the upper end of tube  4  through a cover  14 . Contrary to common syringes, syringe  2  is further provided with an aperture  16  in the upper wall portion of tube  4 , at a location below its upper edge, so that the thickness of piston  10  will not obstruct the aperture  16  when the piston is drawn to the upper end of the tube, as illustrated in  FIG. 2 . In order to assure that the piston will obstruct and close aperture  16  during the part of the procedure when same is required, there is advantageously provided a locking means  18 , such as a swiveling arm pivotably coupled to cover  14  at one end and having a pin engageable with a hole  20  in handle  12 , at its other end. 
   In accordance with the method of the invention, the syringe operates as follows: blood is drawn from the patient into syringe  2 . The piston  10  is then secured in a position so as to align the periphery of the piston with, and close, the aperture  16 , a valve  22  is fitted over the nozzle  6 , whether or not the needle  8  has first been removed, and the syringe containing the blood sample  24  is placed in a commonly used and available centrifuge (not shown). Centrifuging of the sample will cause it to divide into two components: a lower component, essentially constituting packed-cells  26 , above which the upper component, plasma  28 , accumulates. The means  18  are then moved to release handle  12 , which is then pulled above aperture  16 . The plasma  28 , or a portion thereof, is sucked out of syringe  2  through aperture  16  into another syringe or suction device  30 , for analysis ( FIG. 2 ). Valve  22  is then removed, syringe  4  is fitted with a fresh needle  8  and cells  26  are reintroduced into the patient&#39;s bloodstream, replenishing the cells and avoiding erythrocyte deficiency. 
   Modifications of the structure of the syringe  2  are illustrated in  FIGS. 3 and 4 . In  FIG. 3 , the syringe includes a piston  10  having an aperture  32  which is normally closed by any suitable removable plug, such as a screw  34  passing through the cover  14 . After centrifuging, the plug is removed and the plasma is withdrawn from the syringe  2  by means of a suction device penetrating through the piston aperture  32 , the screw  34  is replaced and the remaining plasma with cells can be injected back into the patient. 
     FIG. 4  illustrates a hollow handle  12 , through which an elongated screw  36  is attached to the piston  10 . After centrifuging, the screw  36  and possibly the entire handle  12  is removed, thus forming an aperture  38  in the piston. The plasma is removed through aperture  38  by means of a suction device having a needle, and similar to the embodiment of  FIG. 3 , the remaining plasma containing. cells is injected back into the patient. 
   A still further embodiment of the syringe according to the present invention is shown in  FIGS. 5A ,  5 B and  5 C. Piston  10  of the syringe consists of two disks  40 ,  42 , each made in the illustrated case with identically shaped triangular apertures  44 . Disk  40  is attached to an outer tubular handle  46 , while disk  42  is attached to a rod  48  concentrically disposed inside tubular handle  46 . Rod  48 , together with disk  42 , is rotatable with respect to handle  46  and disk  40 , thereby facilitating, in a first state, the alignment of apertures  44  in the two disks  40 ,  42 . In its second state, the alignment of the apertures is removed, so that the apertures in disk  40  are obscured by disk  42 , forming a contiguous, non-apertured piston surface. 
   The step-by-step method of operation of an embodiment of a syringe utilizing the piston of  FIGS. 5A–5C  is illustrated in  FIGS. 6A to 6F . 
     FIG. 6A  illustrates the syringe after blood is withdrawn from a patient. The withdrawal of the blood required the forming of a non-apertured piston surface, as explained above with respect to  FIGS. 5A–5C . Shown is, the blood, comprising intermixed blood cells and plasma. The nozzle  6  is then covered with a cap or valve  50  ( FIG. 6B ) and the entire syringe is placed in a centrifuge. Centrifuging causes a clear division between the blood cells  26  and plasma  28 . Disk  42  is then turned by means of rod  48 , so as to form an apertured piston. Piston  10  is pushed inside tube  4  to a position between the two blood components, namely, between cells  26  and plasma  28  ( FIG. 6C ). Rod  48  is then turned again so as to close apertures  44 , forming a single piston surface. The valve  50  is removed, a fresh, sterile needle  8  is fitted into nozzle  6 , and the cells  26  are reinjected into the patient ( FIG. 6D ). The piston is brought into its open state, enabling it to be pulled back through the plasma in the syringe ( FIG. 6E ). The piston is then brought into its closed state, thus enabling the plasma  28  in the syringe to be directly ejected into a test tube by means of the piston ( FIG. 6F ). 
     FIGS. 7–12  illustrate yet another embodiment of the syringe according to the invention. There is seen in  FIG. 7  a syringe body  52 , provided with a pair of trunnions  54  on which the syringe can be hung into the centrifuge. The lower end of syringe body  52  is in the form of a tapered nozzle or tip  56 , advantageously of the male luer-lock type with its internally threaded sleeve  58 , to which tip a hypodermic needle, a catheter with an integral female luer-lock terminal, and other accessories are connectable. 
   Inside syringe body  52  there is slidably disposed a hollow piston rod  60 , seen to better effect in  FIGS. 8 and 9 . Piston rod  60  has a gripping disk  62  at its upper end, and an undercut head  64  with a central bore  65  at its lower end. The inward-pointing rim  66  of a piston  68 , made of an elastomer, engages in the undercut. As seen in  FIG. 9 , the cross-section of piston  68  is greatly reduced in the central portion, with a hollow needle  70  poised above, but not touching, that weakened point. The purpose of this arrangement will be explained further below. 
   Inside hollow piston rod  60 , there is slidingly accommodated a vessel  72 , designed to accept the blood plasma after its separation, by centrifuging, from the erythrocytes. As can be seen in  FIG. 9 , the hollow needle  70  is fixedly attached to bottom  74  of vessel  72 . A helical compression spring  76  is interposed between bottom  74  of vessel  72  and head  64  of piston rod  60 . When in the position shown in  FIGS. 7 and 8 , the upper end of vessel  72  projects from gripping disk  62  and is seen to consist of three prongs  78  topped by pads  80 . Also seen is a safety tab  82 , designed to prevent needle  70  from inadvertently perforating piston  68 . When perforation is required, safety tab  82  is simply broken off. 
   Further shown in  FIGS. 7 and 8  is a stopper  84 , in the form of a female luer-lock connector having two wings  86  for handling. Stopper  84  is applied after the required quantity of whole blood has been drawn, prior to centrifuging of the sample. 
   The procedure for using the syringe according to the invention is as follows: 
   A hypodermic needle or a catheter is used to attach the syringe to one of the patient&#39;s blood vessels and the required quantity of whole blood is drawn. After that, the needle or catheter is detached from the syringe and stopper  84  is mounted on nozzle  56 . A lock  88  is clipped onto piston rod  60 , to prevent centrifugal force acting on the syringe from exerting pressure on the syringe. Then, the syringe, now with the greatly extended piston rod  60  in the position shown in  FIG. 11 , is introduced into the centrifuge. After centrifuging has been concluded and the whole-blood content of the syringe has been separated into the packed-cells component and the supernatant plasma component, the syringe is removed from the centrifuge, safety tab  82  is broken off, disk  62  is held between the index and middle fingers, and pressure is applied by the thumb on pads  80 , causing needle  70  to perforate piston  68  ( FIG. 12 ). The perforation establishes a pathway between syringe body  52 , now full with the separated, packed blood cells, and the supernatant plasma. 
   Now, piston rod  60  is pushed down. Since nozzle  56  is closed by stopper  84 , the descending piston  68  causes the plasma to pass through needle  70  into plasma vessel  72 . Piston  68  is pushed down until it reaches the interface between the plasma and the packed-cells. At that point, pressure on pads  80  is relaxed and spring  76  withdraws needle  70  from piston  68  by lifting vessel  72 , thereby hermetically closing off the packed cell component remaining in the syringe due to the resilient elastomer of piston  68 . 
   Plasma vessel  72  is now withdrawn from piston rod  62 , needle  70  is secured by means of a rubber plug  90 , the upper end of vessel  72  is closed with a plug  92 , and vessel  72 , along with its plasma contents, is transferred to the laboratory for analysis. 
   As a last step, stopper  84  is replaced by a hypodermic needle or a catheter, and the packed-cells component is returned to the patient&#39;s blood vessel. 
   Other types of pistons in which an aperture can controllably be formed are also envisioned. 
   It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.