CA1176573A - Method and apparatus for on-line filtration removal of macromolecules from a physiological fluid - Google Patents

Abstract

METHOD AND APPARATUS FOR ON-LINE FILTRATION REMOVAL
OF MACROMOLECULES FROM A PHYSIOLOGICAL FLUID
ABSTRACT OF THE INVENTION
An on-line filtration system for the removal of macromolecules greater than 70,000 mol. wt. from a physio-logical solution, such as blood, in the therapeutic treat-ment of various disease states. For blood, the plasma (which contains the macromolecules) is separated continu-ously from the blood using a first membrane filter with a membrane porosity of nominally 0.2 to 1.0 micron. The separated plasma is then continuously filtered in a physi-ological temperature state or a cooled state through a second membrane filter with a membrane porosity of nomi-nally 0.01 to 0.2 micron, which retains the macromolecules.
In the cooled state, separation of the macromolecules is effected more efficiently than could be done in the non-cooled state. The treated plasma (macromolecules removed) is then reunited with the blood flow coming from the first plasma filter and returned to the patient. The blood flow and filtration processes are generally continuous. Suit-able agent(s) may be added to the separated plasma to promote formation of macromolecules.

Description

This is a divisional a~plication of copending application serial no. 377,362, filed May 12, 1981.

METHOD AND APPARATUS FOR ON LINE FILTRATION REMOVAL
OF MACROMOLECULES FROM A PHYSIOLOGICAL FLUID
This invention relates to pla3mapheresis and more particularly to the removal of undesirable solutes from plasma ~n a plasmapheresis process.
BACKGROUND OF T~E INVENTION
. . _ Pla~mapheresis (the removal of blood, separa-tion of the plasma and the reinfusion of the blood c~
with or without the replacement of the patient'~ plasma by donor plasma, a plasma ~raction, or other physiologi-cal solution, is becomi~g more u~eful in the clinical treatment o~ various disease states. Such disease ~tates have in common the presence of undesirable ele~ated levels of plasma solutes. Such solutes (due to their increased size) cannot be effectively removed by techniques such as dialyses and hemofiltration. Therefore plasma rémoval with the infus:ion of physiological solutions is effective in depleting their concentration. Various disease 8tat~3 reated by plasmapheresis are as follow~.
Myasthenia gravis Glomeruloneph~itis Goodpasture's syndrome Skin diseases pemphigus herpes gestationis Severe asthma Immune complex diseases crescentic ~phritis "` ~ lL76~73

-2-systemic lupu5 erythemato~us Wegner'~/polyarteritis subacute ba~terial endocarditis ' cryoglobulinemia cutaneous vasculiti~
Diabetic hypertriglyceridemia Hypercholesterolemia Macroglobulinemia - Waldenstrom's syndrome hypervisco~ity syndromes paraproteinie~ia~, myeloma Hematological di~ea3es hemolytic anemia red cell agglutinins auto-antibody lymphocytes thrombotic thromcocytopenia purpura immune ~hrombocytopenia factor VIII inhibitor or antibodies Raynaud' 8 disease and phenomenon Renal transplantation Rhe~us incompatibility Hepatic colna Hypertension ~otor neurone disease amyotrophic lateral sclerosis auto polyneuropathy Refsum'~ disea3e Guillain-Barre syndrome Arthritis Removal of protein bound toxins poisons - methyl parathion, poisonous mushrooms, paraquat hormones - thyroid protein bound aluminum - dialysis dementia Cancer Insulin resistant diabetes While this list is not exhaustive, it exempli-fies the wide range of diseases a4sociated with biochemi-cal abnormalities; such biochemical agents being of high molecular weight.

` `` ~17~573 At present the number of cases of plasma ex-change are small and in n~lny instances without controls.
The SUCC~S8 in some case~ i8 quite impressive-The treatments presently being carried out by5 pla.~mapheresis may be generally grouped into two types:
(1) removal of an abnormal metabolite(s) or toxin(s) and (2) treatment of a disorder of the immune ~y~tem. Exam-ples of the fir~t type include hepatic support, hyper-triglyceridemia, hypercholesterolemia, and the removal of protein or lipid bound toxins. Examples of the ~econd type include myasthenia gravi~ glomerulonephritis, macro-globulinemia~, arthritis, and systemic lupu~ erythema-to~is.
While in some of ~he diseases there i8 little known concerning the correlation of the disease with ~he increa~ed plasma factor~, for other disea~es the factor( 8 ) is known or correlation between the increased factor and the disease state can be shown as outlined in Table 1 and Table 2 as follow~.

1 ~76~'~3 TABT ~ 1 IMMUNOLOGICAL DISOR~ERS TREATED BY PI~SMAPHERESIS
Disease Increased Factor(~) or Abnormality __ Myasthenia gravis Antibody ~pecific for acetyl-S choline receptor Renal transplant rejection (Antibody to glomerular ba~e-(ment membrane Goodpasture'~ syndrome ~Antibody to basement membrane (of lung 10 Rhesus incompatibility Anti-D-antibody Systemic lupus erythema- DN~ antibodies and immun~
tosua complexes of DNA
Glomerulonep~ritis Immune complexe~ or auto-antibodie~
15 Macroglobulinemia IgM and hyperviscosity (Waldenstrom's syndrome) Pemphigu~ vulgaris IgG anti~odies Asthma bronchitis IgE
Myeloma Myeloma globulin ~o Raynaud's disease and Macroglobulin, i~creased vis-pnenomena c08ity ~hrombocytopenic purpura Immunocomplex ~ancer ~ 2 globulines, f?_globulins, ~ -l-antitryp-sin, ceruloplasmin, orosomu-coid, haptoglobin, IgA
Breast cancer Circulating immune complex Polyneuropathy Antibodies to myelin Rheumatoid arthritis "Serum factor"
30 Diabetes Autoantibodies to insulin receptor Autoimmune hemolytic Antibody to R~C
- . anemia METABOLXC DISORDERS TREATED BY PLASMAPHERESIS
Disease Increa3ed Factor(Q) or AbnormalitY
5 Hepatic coma Metabolic factors (bilirubin) Refsum's disease Phytanic acid (bound to lipo-proteins) PoisOnings Protein bound drug Dialysis dementia Protein bound aluminum 10 Hypertriglyceridemia Triglycerideq and hypervis-cosity Hypercholesterolemia Choles~erol Amyt~ophic lateral Cytotoxic factors, immune 15 ~clerosis complexes suspected Listed are various diseases for which increased levels of antibodies or macrom~lecules exist and for which plasmapheresis has been useful by its reduction of these substances. For example, in myasthenia gravis, antibodies specific for the acetycholine receptors are elevated. ~emoval of these antibodies by pla~mapheresi6 shows improvement in the patients. ~n macroglobulinemia, there is an increased level of gamma globulin. Reducing this level by plasmaphçre3i~ is clinically effective.
The conventional method of plasmapheresi~
employs a cell centri~uge involving bulky and expensive equipment which is not portable and is very co~tly, and carries with it potential hazards. Namely, essential plasma products are lost that are not being replenished in the substitution fluids and the potential exists for acquiring hepatitis. In addition, the effectiveness of the procedure is limited due to the limited removal that can be accomplished in discarding a limited volume.
If conventional plasmapheresis were to be accepted for the treatment of many of these diseases there would be created a greater need for plasma products than could be met nationally. Obviously, to take advantage of pla~mz-pheresis in treating these diseases, new techniques mu~t be developed for removal of the plasma "toxins".
A ma~or improvement would be to develop "on-line" removal systems to remove the "toxin" in question and to return the treated plasma back to the patient. The advantage~ are quite obvious. The recent development o~
membrane systems for the on-line removal of plasma from whole blood has added impetus to the development work.
Extracorporeal treatment of plasma generated by either membrane plasma separators or centrifuges has been carried out by either specific or non-specific sorbents such a activated charcoal, nonionic or ionic resins and immobil-ized proteins, cells or tissue.
In many of the disease states multiple biochemi-cal abnormalities exist, and due to the nature of the abnormal substances involved, multiple sorbent sy~tems may be required. Such developments will take ~any year~.
Therefore due ~o the nature of the substances (larger 25 molecular weights of generally over 100,000 daltons) or the nature of the disease state, where the specific macro-molecule that is causative for the symptoms of the disease is not defined, the more general approach of removing all molec~les ovex a specific molecular weight can be chosen.
Mem~ran~s having a molecular cutoff of about 100;000 dal-tons are chosen as they can pass albumin thereby negat-ing the need to infuse this plasma product as is done by the conventional plasmapheresis process.

1 :L76~73 Therefore it is an object of the invention to provide a plasmapheresis method and apparatus for removing macromolecules of predetermined size from a plasma solution.
In a process aspect of the invention there is provided a method of removing macromolecules from a stream of physiological solution including: forming from the stream of a physiological solution a separated stream containing macromolecules, then using a membrane filter having a porosity to remove macromolècules of predetermined size out of the separated stream, to produce the filtered separated stream substantially free of macromolecules of the predetermined size, and further including the step of adding a complexing agent to the separated stream before it is filtered by the membrane filter, the method being continuous.

mgJ~ - 7 -In an apparatus aspect of the invention there is provided an apparatus for removing macromolecules from a patient's physiological solution comprising; plasma separation means for dividing a physiological solution containing macromolecules into a concentrated cellular element stream and a plasma stream, filter means in fluid flow communication with the plasma separation means for receiving the plasma stream therefrom and filtering such plasma stream to remove macromolecules of a predetermined size therefrom, fluid flow communication means for receiving the filtered plasma stream from the filter means and for receiving the concentrated cellular element stream and combining the two last-named streams to form a processed stream substantially free of macromolecules of the predetermined size for return to the patient, a complexing agent being added to the plasma stream before it is filtered by the filter means to promote macromolecules formation.

mg~ 8 -Other objects and advantages of the invention will be apparent from the following description taken in conjunctio~ with the drawings whereino BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a schematic flow diagram illustrat-ing the method and apparatus of the invention;
FIGURE 2 is a schematic flcw diagram similar to FIGURE 1, but showing a modification thereof: -. FIGURE 3 is a chart showing albumin retention in a plasma solution filtered by the method and apparatus shown in FIGURE l; and FIGURE 4 i~ a chart showing the cryo-protein ~removal in the same plas~a solution used in the FlGUR~ 3 chart and employing the method and apparatu~ show~ in FIGURE 1.
In the drawings, like numhers and letters are used to identify like and similar parts throughout the several views.
DE~INITIONS:
Crvoprecipitates: Ser~m globulins that precipitate or gel on cooling at low tem-peratures (4-35C) and redissolve on warming ,.~.

`: I ;176573 CrYoqlobulins: Homogenous proteins that have become physically altered (myeloma, mixture~
of immunoglobulins (as IgG and (IgM, sr Lmmune complexes (as antigen and antibody), possible with complement (as in SLE) Mol. Wt. 100,000 -1,800,000 Macromolecules: Molecules of 100,000 daltons molecular weight or higher The use of the artificial Xidney, blood oxy-genators, and artificial joints is well recognized today.
However, for a variety o~ disease states, application of the techniques of extracorporeal circulation and mechani-cal or mass transfer support are becoming more recognized.
Significant advances have been made in the axeas o~ cardiac, pancreatic and liver support in recent years. Within the past decade, with the availability of the continuous ~low blood cell centrifuges, many different disease states, mostly of an Lmmunological nature, have been investigated in response to plasma exchange.
For many of the diseases, the nonspecific removal of plasma factoxs has correlated with improvements in the disease state. Problems with this conventional methodolo-gy in chronic applications are the limited removal re-lated to the volume o exchange and dilution by the required inusion solution, the requirement for plasma products and the potential hazards of such infusions, and the need 'for bulky and expensive capital equipment. The removal of the specific plasma factors as antibodies, immune complexes, and immunoglobulins by specific agents as sorbents may be desirable; however, in most disease states the etiology is not known.
In most immunologically related disease states the presence and abnormal concentration of plasma factors : I ~.76573 greater than t~e molecular weight of albumin, suggests the application of membrane filtration. In practic~, plasma is separated on-llne from whole blood in an extra-corporeal circuit. The plasma which contains the molecules S of interst i~ then filtered through a membrane filter which reject~ those macromolecules greater than albumin and allows albumin and the smaller size plasma solute3 to pas~ and be returned to the patient. The return of the albumin o~viates the requirement for infusion of large volumes o~ donor plasma. Such techniques are presently being applied clinically in the treatment of rheumatoid arthritis and certain other disease states.
Plasma exchange has been shown to be effective in the treatment of various diseases, including the immu-nologically based disease states. This technique, however,has severe limitations in chronic applications, such as limited removal related to the volume of exchange and dilu-ti~n by the infusion solution and the requirement for plas-ma products. Removal of the macromolecules as immune complexes by specific sorbents in most cases re~uire~ ex-tensive development work. The nonspecific removal of macromolecules by membrane filtration makes the treatment simpler and more universal in application.
In practice, plasma i8 separated on-line fro~
whole blood. The plasma which contain~ the macromolecules is then filtered through a membrane filter which rejects the macromolecules and passes the albumin and smaller size plasma solutes which are reinfùsed into the patient.
With rheumatoid arthritis plasma and membranes of nominal pore size of 0.1 microns, over 9P~ passage of albumin was achieved with greater than 25~ rejection in a single pass of rheumatoid factor and Clq binding immune complexes.
In certain immunologically related disease states, the 1 ~76573 increased levels of cryoprecipitates containing antigen and or antibody in the form of immune complexes with or without complement sugge~ts that their removal could be therapeutic. Modification of the on-line pla~ma ~iltra-S tion circuit i5 made to include a heat exchanger to coolthe plasma to below 10C before filtr~tion. Using rheuma-toid arthritis plasma with cryoprecipitate concentrations of greater than 5 tLme~ normal, reductions to concentra-tions below normal values were achieved in single pa~
with over 90~ passage of albumin.
The technique~ of on-line plasma filtration th~ough select membranes and t~e cooling of placma to promote qel formation of abnormal plasma proteins to maxi-miz~ their removal are simple and easy to apply. They do not requLre the infusion of expensive plasma products.
~ Referring to the drawings, FIGURE 1 illu~trates the method and apparatu~ of the invention as applied to the filtration of biood, although it wil~ be understood that any other type of physiological fluid such as, for example, lymph, a~citic ~luid, etc., may be treated.
In FIGURE 1, blood is drawn from a patient into line 10 and fed into a pump 12 from which it is pumped into a line 14 and then into membrane filter 1.
In place of membrane filter 1, a centrifuge may be em-ployed as the function at this point is to separate th~blood into a plasma solution stream (fed into line 18) and a concentrated cellular element stream (which is fed into line 19).
From the membrane filter 1, the plasma solution is led down a line 18 to a cooling unit 20 where the plasma solution is cooled to a temperature of between just above the freezing point of the plasma solution and about 35 centigrade to cause the macromolecules to gel or 1 17~573 precipitate. Next, the cooled plasma solution is led down the line 22 to membrane filter 2, where the macro-molecules are xetained (and the albumin and lowex molec-ular weight components pass through).
From filter 2, the filtered plasma ~plasma) minus larger molecular weight solute) is led through the line 24 to the juncture 26, where the filtered plasma stream and the concentrated cellular element stream are joined or united ~to form a processed stream) and then fed into line 28 and thence into the heater unit 30.
The heater unit 30 heats the processed stream to body temperature. The heated processed stream is then fed into the line 32 and returned to the patient in a con-tinuous process.
In the FIGURE 2 modification, the cooling unit 20a i8 shown encasing the filter 2 (and a portion of the - ' incoming line 22) such filter 2 being enclosed in a layer of,in~ulation 34. This structure assures proper (cooled) temperature maintenance within filter 2 during the fil-20 te~ing process~ -It is to be understood that, if required, it woul~ be in order to inject into line 22 (before cooling) a complexing agent for effecting gelling or precipitation or macromolecule formation. A complexing agent i~ an agent which will allow single or multiple plasma factors co form a complex of higher molecular weight. Such agent could be a sorbing agent or ion exchange material such as, for example, heparin which forms complexes with cholesterol and lipid containing components.
~0 Thus, FIGURES 1 and 2 outline filtration for the separation of plasma from whole blood. A cell centri-fuge could also be used in place of membrane filter 1 for the generation of the plasma flow stream. The plasma, 1 ~76573 which contains the factors of interest, is directed to a membrane filter 2 designed to filter out the macro-molecule(s) of interest, but pass those plasma ~olutes of smaller size. The plasma is then reunited with the blood flow (concentrated cellular element stream) from filter 1 (or in the case of a centrifuge the blood flow from the centrifuge) before being returned to the patient.
For filter 1, a membrane with a normal poro~ity of 0.2-1 micron would be required to generate the plasma.
Past investigatiOnQ with membranes in the lower range porosity have indicated ~hat sieving coef~icients of certain plasma macromolecules in the normal and the diseas~
states are low (less than 0.8). In addition, operational conditions of filter 1, including blood and plasma flow , and ~elocities and transmembra~e pressures may ~eriou~ly affect the sieving pr0perties of the macromolecule~ o~
interest. The filtration of blood i~ filter 1 is cro~s flow. Filter 2, which employs a mem~rane with a porosity of nominally 0.01 to 0.2 microns, would be required to remove macromolecules of 100,000 daltons molecular weight or greater. For this porosity, essential substances as albumin and l~wer molecular weight solutes will pass through the membrane filter 2 and be returned to the patient. The filtration of the plasma in this filter may be cross flow or conventional (flow directly into filtration media~. In cross flow, a recirculation circuit and an additional pump are required. Ir this recirculation circuit a vari-able resistor ~as a screw clamp) may be placed to regulate the rate of filtration.
Serum glo~ulins that precipitate or gel on cool-ing at low temperatures (nominally 35- 4C and generally 25-4C) and redissolve on warming may occur in a variety of disorders such as myeloma, kala-azar, macroglobinemia, - - u ~ 176573 mali~nant lymphoma, collagen diseases as lupus, glomeru-lonephritis, infectious mononucleosis, syphilis, cytome-galovirus disease, rheumatoid arthritis, and other auto-immune diseases. The globulins may represent homogeneous proteins that have become physically altered (myeloma), mixtures of immunoglobulins (as IgG and IgM~, or immune complexes (such as antigen and antibody), possibly with complement (as in systemic lupus erythematosus). The term cryoglobulins refers to those abnormal globulin~.
The molecular weight of cryoglobulins vary from 100,000 to 1,800,000 daltons molecular weight. By taking advan-tage of the precipitation or gelling effect of cryoglobu-lins their removal can be effected~ As the plasma i3 separated from blood it is cooled. While in some clinical situations only a small temperature change ~xom phy~iologi-cal temperature of 37C is needed to start gelling or precipitation, in the clinical situation~ temperatures as low as near freezing for extended times are necessary to cause precipitation in collected serum.
Occasionally ~ryoglobulins will precipitate out at room temperature, but as a rule, sera have to be cool~d to 10C or lower, before precipitation occurs.
With the cryoglobulins cooled to a level to cause precipi-tation or gelling the filtration of these substances from the plasma is greatly facilitatedO ~he advantage of ~his scheme over the direct filtration scheme without excessive cooling is that the membrane porosity or pore size may be increased allowing for higher sieving of the normal proteins in the plasma and therefore more efficient re-turn to the patient. While cooling of the plasma wouldnormally take place in the circuit the temperature decrease may not always be uniform or low enough therefore a heat exchange system woule be most desirable to cool the plasma.

: ~76573 ~ 16-To avoid chills to the patient or precipitation or gel-ling of the cryoglobulins i~ the blood circuit returning to the patient, the blood should be rewarmed by heater 30 to physiological temperature on its return to the patient~
5 EXPERIME~rAL STUDIES
Ex~eriment #l Asahi (Asahi Medical Co., Tokyo, Japan) S-type filter containing cellulose acetate hollow fiber membranes with a nominal pore size of 0.2 microns with 84% porosity was evaluated for sieving properties of Clq binding L~mUne complexes that are present in rheumatoid arthritis. Plas-ma obtained by centrifugation from patient ~Lo who had high values of Cl~ binding immune complexes was perfused through the S-type filter. Sieving coefficients (concen-tration of filtrate divided by the concentration in thefluid flow stream to the filter) for the Clq binding im-mune complexes averaged 0.49 over a two-hour perfusion period. This study demonstrated that, these complexe~
can be filtered from plasma but that i~s efficiency is lo~, allowing only about 50~ of the complexes to be re-moved. This would necessitate long~r treatment time.
Experiment #2 Due to the relatively low e~ficiency of the Asahi*S-type filter various available membrane~ of nomi-nal pore size of 0.2 to 0.1 micron were selected for~tudy. The membranes were Tuffryn ~T-100 (polysulfon~) with pore size of 0.1 micron from Gelman Sciences ~Ann Arbor~ Michigan), X~300 (acrylic copolymer)5~pproximate-ly ~.02 micron pore size) from Amicon (Lexington, Massa-chusetts), (VMWP-approximately 0.05 mi~ron pore size) MF
(mi~ed cellulose acetate and nitrate) from Millipore Corp. (Bedford, Massachusetts).
Plasma from a patient suffering from rheumatoid * trade mark 1 ~6573 arthritis was procured by centrifugation. Such plasma contained elevated levels of rheumatoid factox and Clq binding immune complexes. The membranes were assembled into small test cells gi~ing a total surface area of 56 S cm2. The plasma was recirculated through the test cells at ambient temperature. For testing the XM-300 membrane the plasma was filtered first through an Asahi ~ilter.
This filtration process reduces the concentration o~
macromolecules in the plasma. For one of the ~T-100 membrane, in addition to first filtering the plasma through an Asahi filter, the plasma was used after decan-tation following refrigeration. This procedure re~ult~
in the removal of a significant amount of cryoglobulins from the plasma. For the other HT-100 membrane tested and the MX 0.05 membrane tested the cryoprecipitate~
were resuspended in the plasma for the study. It is noted that for all membranes, complete ~ieving ~no rejec-tion) of small molecule weight solutes is achieved. Par-ticularly noteworthy is the sieving of albumin. In the initial stages of the filtration studies (less ~han 30 minutes) nearly complete rejection (low sieving coefficient) was seen for the X~-300 membranes. There was about 2~
rejection of Cl~ binding immune complexes and 32~ re jec-tion of rheumatoid factor for the HT-100 membrane at 10 minutes.
Experiment #3 A 54-year old white female was selected with extremely aggressive seropositive rheumatoid arthritis who failed all accepted modes of therapy and in addition failed cytotoxic drugs including Methotrexate and Cytoxan.
The only therapeutic modality to which she has transiently responded has been plasmapheresis. The subject's blood was treated by the method and apparatus of FIGURE 1, such ~ ~76~73 treatment reducing her immune complex Clq Binding ( ~74 u/ml.) from 2256 units down to 688 units with a resultant improvement in symptomatology.
Experiment #4 S Reerence is now made to FIGURES 3 and 4. In this experiment, a patient's plasma was treated by the method and apparatus of FIGURE 1. It will be noted in -FIGURE 3 that the albumin loss was only about 20%, while as shown in F~GURE 5, the cryo-protein reduction was about 95%.
Both charts ~FIGURES 3 and-4) are from the same single experiment, which was done under a cooled state.
Such experiment shows that the albumin substantially re-mains in solution (which i~ hig~ly desirable) and the cryo-protein (which represents the macromolecules) are almo~t all removed from the plasma solution.
In the method and apparatus of FIGURE 1, treat-ment time is normally about two to four hours, with roughly 1.7 to 3.0 liters of plasma being treated.
Controlled recirculation of the treated plasma rrom line 24 over to line 18 could be effected if desired.
Thus, the invention provides a method of remov-ing macromolecules from a plasma solutîon including pro-viding a plasma solution containing macromolecules includ-ing a minimum size thereof, cooling the plasma solution to a temperature not lower than just above the fre~zing point of the plasma solution, and filtering the plasma solution with a membrane filter 2 having a porosity up to said minimum size to remove macromolecules of predeter-mined size from the plasma solution.
Also provided is a method of removing macro-molecules from a physiological solution such as blood including, securing a physiological solution from a 1 1~6573 patient, separating the physiological solution stream into a concen~rated cellular element stream and a plasma stream containing macromolecules therein by either a mem-brane filter or a centrifuge, filtering macromolecules of predetermined size out of the plasma stream to fonm a filtered plasma stream, combining the filtered plasma stream and the cellular element stream to form a processed stream, and returning the processed stream to the patient in a continuous process. The step of heating the processed stream to approximately body temperature before it is re-turned to the patient may also be included.
In such method the membrane filter for re~oving the macromolecules out of the separated stream has a por-osity of nominally 0.01 to 0.2 microns to pass macro-molecules of approximately ~0,000 molecular weight and be-low and reject or collect macromolecules of approximately 100,000 molecular weight and over.
The invention also contemplates an apparatus ~or removing macromolecules from a patient's physiological solution including, plasma separation means 1 for divid-ing a physiological solution such as blood containing macromolecules into a concentrated cellular element stream and a plasma stream, a cooler 20 in fluid flow communica-tion with the plasma separation means 1 for receiving the plasma stream therefrom and cooling such plasma stream to cause the macromolecules therein to gel or pre-cipitate, filter means 2 in fluid flow communication with the cooling unit 20 for receiving the cooled plasma stream therefrom and filtering such cooled plasma stream to re-move macromolecules of a predetermined size therefrom,fluid flow communication means 26 for receiving the filtered plasma macrosolute stream from the filter means and for receiving the concentrated cellular element stream ~ ~76573 and combining said two last-named streams to form a processed stream for return to the patient in a continuous pxocess.
Further included is a pump 12 in fluid flow communication with the plasma separation means 1 and with the patient to pump the physiological solution from the patient to the plasma separation means 1.
The cooling unit 20 cools the separated plasma stream to a temperature of between just above the freez-ing point of the separated plasma stream and approxLmately 35 centigrade, although it is to be understood that the cooler 20 may be eliminated in certain instances.
Also, the heater unit 30 is preferred, but may be eliminated if the temperature in the line 28 is near body temperature.
The terms and expressions which have been em-ployed are used as terms of description, and not of limi-tation, and there is no intention, in the use of such terms and expressions, of excluding any equivalent3 of the features shown and described or portions thereof, but it is recognized that various modifications are possi~le within the scope of the invention claimed.

Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of removing macromolecules from a stream of physiological solution including: forming from the stream of a physiological solution a separated stream containing macromolecules, then using a membrane filter having a porosity to remove macromolecules of predetermined size out of said separated stream, to produce the filtered separated stream substantially free of macromolecules of said predetermined size, and further including the step of adding a complexing agent to the separated stream before it is filtered by the membrane filter, said method being continuous.

2. An apparatus for removing macromolecules from a patient's physiological solution comprising; plasma separation means for dividing a physiological solution containing macromolecules into a concentrated cellular element stream and a plasma stream, filter means in fluid flow communication with said plasma separation means for receiving the plasma stream therefrom and filtering such plasma stream to remove macromolecules of a predetermined size therefrom, fluid flow communication means for receiving the filtered plasma stream from the filter means and for receiving the concentrated cellular element stream and combining said two last-named streams to form a processed stream substantially free of macromolecules of said predetermined size for return to the patient, a complexing agent being added to the plasma stream before it is filtered by the filter means to promote macromolecules formation.