referring to fig1 it is seen that a patient 10 is shown therein in which the patient &# 39 ; s blood is pumped via tube 12 to an oxygenator 14 by means of roller pump 16 with some of the blood being pumped back to the patient , if desired , via line 18 and other of the blood being pumped via tube 20 to a hemoconcentrator 22 . the hemoconcentrator is a high ultrafiltration device containing a hollow fiber or plate sheet conduit as known in the art . hemoconcentrator 22 has a blood inlet 24 , a blood outlet 26 , and an ultrafiltration outlet 28 . ultrafiltration outlet 2b is coupled via line 30 to an ultrafiltration container 32 . blood outlet 26 is coupled via tube 34 to a two - way valve a . one outlet 36 of valve a is coupled via tube 42 to a platelet storage container 44 . the platelet storage container is connected via tube 46 to oxygenator 14 for returning the platelets to the patient when desired . a negative pressure may be applied to ultrafiltrate outlet 28 of hemoconcentrator 22 by means of a vacuum source coupled to line 50 through two - way valve b . one inlet 52 of valve b is connected to a vacuum source while the other inlet 54 of valve b is connected to a positive pressure source . upstream of blood inlet 24 there is a three - way valve c . valve c allows either blood flowing via tube 20 to be directed via tube 56 to blood inlet 24 or , alternatively , saline solution via tube 58 to be directed through valve c via tube 56 to blood inlet 24 . when the saline solution is directed to blood inlet 24 , the blood flowing via tube 20 will be directed via tube 60 to bypass the hemoconcentrator 22 and to flow directly to oxygenator 14 . valves a , b and c are interconnected and can be controlled to provide flow in various manners . for example , referring to fig2 it can be seen that valves a , b and c are rotated to positions whereby a vacuum is applied to the ultrafiltrate outlet 28 of hemoconcentrator 22 , the patient &# 39 ; s blood flows to the blood inlet 24 of the hemoconcentrator 22 , and the blood from the outlet 26 is directed toward oxygenator 14 . thus fig2 illustrates the valve positions during concentration of the platelets on the membrane walls . instead of applying a vacuum to ultrafiltrate outlet 28 , a positive pressure could be provided to the blood path . thus the significant step for obtaining concentration of the platelets on the membrane walls is the provision of a transmembrane pressure that is lower on the ultrafiltrate side . now referring to fig3 valve a has rotated so as to allow the blood flow from the hemoconcentrator to be directed to the platelet storage container 44 . valve b is rotated so that the application of the negative pressure is terminated and the patient &# 39 ; s blood , which flows through valve c , will be used to flush the platelets from the hemoconcentrator so that the platelets will be carried with the patient &# 39 ; s blood to the platelet storage container . referring to fig4 this process is similar to the process of fig3 but valve b has been rotated so as to connect the positive pressure source to the ultrafiltration outlet 28 of hemoconcentrator 22 . in this manner , during flushing the negative pressure source will aid in removing the platelets from the membrane walls . referring to fig5 in this embodiment instead of using blood as the flush , saline solution or another ionically balanced non - cellular solution is passed through the hemoconcentrator while the patient &# 39 ; s blood is diverted via tube 60 . fig6 is similar to fig5 but in fig6 a positive pressure is applied to ultrafiltrate outlet 28 instead of simply terminating the vacuum as in fig5 . it is preferred that the platelets be concentrated on the membrane walls with the vacuum being applied to ultrafiltrate outlet 28 for a period of about two minutes , and thereafter for a period of two minutes , and thereafter for a period of two minutes the platelets are flushed and diverted via tube 42 to platelet storage container 44 . thus there is platelet concentration on the membrane walls for about two minutes , flush for about two minutes , platelet concentration on the membrane walls for two minutes , flush for two minutes , etc ., with the system operating in such a cyclical manner for a given time period , or until sufficient platelets have been captured . the plasma water , i . e ., ultrafiltrate , is basically in ionic balance with the blood , so no damage due to ph , ionic , or osmotic effects are expected and the pore size of such blood conduit walls of the hemoconcentrator does not allow the passage of bacteria in order to maintain sterility . alternatively , the ultrafiltrate system may be separately maintained in a sterile state . the system of fig7 is used to obtain as few blood elements with the platelets as possible . to this end , the valve positions of fig2 are first utilized with the vacuum being applied to ultrafiltrate outlet 28 while the patient &# 39 ; s blood flows through the hemoconcentrator and to the oxygenator with platelets thus being concentrated on the membrane walls of the hemoconcentrator . valve c is then turned , as illustrated in fig7 with the patient &# 39 ; s blood being diverted around the hemoconcentrator and with saline solution or other ionically balanced non - cellular solution being directed to the blood inlet of the hemoconcentrator after the cessation of blood flow , but prior to reduction of the negative pressure . some of this saline solution thus passes through the blood conduit removing the bulk of the blood components and it is returned to the main blood pool . some of the saline solution is also ultrafiltrate across the walls of the blood conduit keeping the platelets in place near the conduit wall . after a sufficient rinse , the valve positions of fig6 are utilized to apply a positive pressure to ultrafiltrate outlet 28 and to divert the platelets and saline solution to the platelet storage container via tube 42 . this process is also cycled with an optimum period to allow maximum concentration in a minimum time . alternatively , a schedule may be utilized to use the ultrafiltrate as the rinsing solution , if desired . in this manner , some of the ultrafiltrate is moved to a pressure container during the flushing cycle and is used in place of the saline solution illustrated . thus the ultrafiltrate from ultrafiltration container 32 will become directed into tube 56 and blood inlet 24 of hemoconcentrator 22 so as to be used as the flush . if the total amount of solution in the platelet storage tank 44 is too much , it may be reduced by shutting off the inflow to the hemoconcentrator 22 , leaving the outflow via tube 34 connected via tube 42 to platelet storage container 44 and applying a vacuum to tube 50 . much of the solution will be ultrafiltered from the storage compartment retrograde to normal flow . the platelets captured as a consequence may then be removed by reversing the ultrafiltrate compartment pressure , i . e ., applying a positive pressure to ultrafiltrate inlet 28 , and then using a much smaller amount of ultrafiltrate than was removed . as another embodiment , a plurality of hemoconcentrators may be used in parallel and cycled back and forth . as a specific example , although no limitation is intended , hemoconcentrator 22 may utilize pan ( polyacrylonitrile ) and polysulfon fibers of approximately 200 microns in diameter . blood flows of 500 milliliters per minute , and water flux rates of 150 milliliters per minute may be utilized on one square meter of blood conduit wall . platelet concentration of over 50 percent in a 1 , 500 ml blood pool may be obtained in three minutes under these conditions in a single cycle . multiple cycles could quickly concentrate an entire patient &# 39 ; s blood volume . both acd and heparin may be used as anticoagulants . if only a few platelets need to be harvested for subsequent transfusion , such few platelets may be stored in the fibers themselves without utilizing cycling . in an illustrative embodiment , during the process a large amount of platelets are removed from the patient , perhaps 25 percent of his platelets . this prevents these platelets from being damaged during the operation . once the operation is complete , the platelets are introduced back to the patient by coupling the storage container outlet to the oxygenator . alternatively , the platelets may be added back to the patient in a direct intervenous route just prior to the patient going back to intensive care or during his stay in intensive care . as used herein in the specification and claims , the term &# 34 ; patient &# 34 ; also refers to a healthy donor . it can be seen that in one embodiment of the present invention , the platelets in the storage container are actually stored in the blood because it is the blood that removes the platelets from the walls of the hollow fibers . this is considered desirable in that the platelets that are stored in blood are considered to have a more natural environment . in another embodiment , very clean platelets may be obtained by utilizing saline solution or another ionically balanced solution . in accordance with this embodiment the saline solution is passed through the hemoconcentrator for a sufficient amount of time to remove any blood components , e . g . red blood cells , after the blood flow has been diverted . that is , first the blood is passed through the hemoconcentrator for a sufficient amount of time to perform the platelet collection . the blood flow is then terminated , and a saline or other ionically balanced solution is directed through the hemocentrator . the amount of time in which the saline solution is passed through the hemocentrator is minimized in order to prevent the removal of a significant portion of the collected platelets . preferably the saline is flushed through the hemoconcentrator for from about fifteen to ninety seconds , even more preferably forty - five seconds . during this step of flushing the blood components from the hemocentrator , it is necessary to maintain the negative pressure . the maintanence of the negative pressure , that is the maintanence of the greater pressure on the saline side of the membrane , is necessary to retain a significant portion of the collected platelets within the boundary layer . preferably this negative pressure is in the range of about - 200 millimeters mercury . after the lapse of the appropriate amount of time the negative pressure is removed . the collected platelets are then free to pass out of the hemocentrator with the saline solution . this solution of the saline and collected platelets is diverted into an appropriate collection container . in accordance with a still further embodiment of the invention , the blood plasma or saline being drawn through the membrane of the hemoconcentrator is stored . typically , the hemocentrator includes a casing about the ultrafilter membrane . the plasma or saline passing through the membrane collects in this casing . the stored plasma is forced back through the membrane of the hemoconcentrator , by the appropriate application of pressure during the procedure of flushing the platelets from the boundary layer . this reduces the need to adding saline or other suitable solution to the system during the collection process . this is particularly advantageous when the platelets are to be returned to the same patient . while the preferred embodiments have been described , various modifications and substitutions may be made thereto without departing from the scope of the invention . accordingly , it is to be understood that the invention has been described by way of illustration and not limitation .
the present invention concerns a novel process for collecting and storing platelets . the process enables the platelets to be removed from a patient prior to surgery , stored in a quiescent environment , and returned to the patient at the end of the surgery .