Method and system for colloid exchange therapy Number:7,520,992 from the United States Patent and Trademark Office (PTO) owispatent The present invention relates to a method and system for using a hemofilter to treat IMRD, hepatic failure, exogenous intoxication and other conditions associated with toxins in a patient's blood. One treatment includes the use of a very large pore hemofilter to remove target complex molecules and/or target molecules from a patient's blood and to infuse a replacement fluid into the patient's blood to maintain a prescribed albumin concentration in the patient's blood.<H exchange, therapy, Method, and, syst, 7520992.html, Patent, pto, 7520992

Title: Method and system for colloid exchange therapy

Abstract: The present invention relates to a method and system for using a hemofilter to treat IMRD, hepatic failure, exogenous intoxication and other conditions associated with toxins in a patient's blood. One treatment includes the use of a very large pore hemofilter to remove target complex molecules and/or target molecules from a patient's blood and to infuse a replacement fluid into the patient's blood to maintain a prescribed albumin concentration in the patient's blood.

Patent Number: 7,520,992 Issued on 04/21/2009 to Radunsky, et al.

Inventors: Radunsky; David (Dallas, TX), Matson; James R. (Dallas, TX), Lee; Patrice A. (Erie, CO)
Assignee: Imunocept, L.L.C. (Plano, TX)

Appl. No.: 11/387,556

Filed: March 23, 2006

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10796882	Mar., 2004
09858210	May., 2001	6787040
60204398	May., 2000
60230106	Sep., 2000

Current U.S. Class: 210/645 ; 210/195.2; 210/321.6; 210/651; 210/805; 604/19; 604/5.01; 604/5.04; 604/6.09

Current International Class: B01D 61/00 (20060101)

Field of Search: 210/321.6,645,650,651,195.2,805 604/4.01,5.01,5.02,5.04,6.09,19,6.08 514/21,23,832 424/140.1,192.1,529-531 530/300,350,362-364,369,380-382

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Primary Examiner: Drodge; Joseph W
Attorney, Agent or Firm: Bromberg & Sunstein LLP

Parent Case Text

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 10/796,882 filed Mar. 8, 2004 entitled METHOD AND SYSTEM FOR COLLOID EXCHANGE THERAPY, which is a divisional of U.S. patent application Ser. No. 09/858,210 filed on May 15, 2001, and entitled METHOD AND SYSTEM FOR COLLOID EXCHANGE THERAPY, now U.S. Pat. No. 6,787,040 which claims the benefit of provisional application Ser. No. 60/204,398, filed on May 16, 2000 and provisional patent application Ser. No. 60/230,106, filed on Sep. 5, 2000, both provisional applications having the title of METHOD AND SYSTEM FOR COLLOID EXCHANGE THERAPY.

Claims

What is claimed is:

1. A very large pore hemofiltration system for removing target molecules and target complex molecules from a patient's blood, comprising: a blood flow circuit operable to remove a portion of the patient's blood to a very large pore hemofilter and return an unsieved portion of the patient's blood; the very large pore hemofilter operably coupled with the blood flow circuit to allow the portion of the patient's blood to flow therethrough; the very large pore hemofilter having a molecular weight cutoff of between about 150,000 Daltons and about 1,000,000 Daltons and selected to avoid removal of significant amounts of immunoglobins and operable to form the unsieved filtered bloodstream portion and an ultrafiltrate stream containing the target molecules and the target complex molecules removed from the portion of the patient's blood flowing through the very large pore hemofilter; a fluid source operable to supply a plasma colloid replacement fluid to the patient's blood; the plasma colloid replacement fluid comprising clean target receptor molecules, clean carrier molecules and/or clean receptor molecules to adequately replenish ongoing losses in the form of target complex molecules removed from the portion of the patient's blood flowing through the very large pore hemofilter; the clean target receptor molecules, clean carrier molecules and/or clean receptor molecules operable to combine with additional inflammatory mediators and toxins from tissue spaces and tissue binding sites in the patient when the filtered bloodstream is transferred to the patient; whereby the clean target receptor molecules, clean carrier molecules and/or clean receptor molecules combine with the additional inflammatory mediators and toxins to form target complex molecules which may be removed by the very large pore hemofilter from the portion of the patient's blood flowing therethrough; and the replacement fluid operable to provide sufficient clean albumin to maintain adequate plasma oncotic pressure at ultrafiltration rates between approximately one liter per hour and twenty liters per hour.

2. The system of claim 1 wherein the plasma colloid replacement fluid comprises a pharmaceutical grade balanced salt solution with a concentration of albumin greater than approximately 0.5 grams per one hundred milliliters.

3. The system of claim 1 wherein the plasma colloid replacement fluid comprises a pharmaceutical grade balanced salt solution with a concentration of albumin less than approximately twenty grams per one hundred milliliters.

4. The system of claim 1 wherein the plasma colloid replacement fluid comprises a pharmaceutical grade balanced salt solution with a plurality of clean target receptor molecules corresponding with a plurality of target receptor molecules contaminated with more than one toxin removed from the patient's blood by the very large pore hemofilter.

5. The system of claim 1 wherein the very large pore hemofilter further comprises a nominal molecular weight cutoff sufficiently large to sieve more than a nominal amount of target complex molecules during hemofiltration and the nominal molecular weight cutoff less than approximately 500,000 Daltons.

6. A very large pore hemofiltration system for removing target molecules and target complex molecules from a patient's blood, comprising: an extracorporeal blood circuit operable to remove portion of the patient's blood to a very large pore hemofilter and return an unsieved portion of the patient's blood; the very large pore hemofilter operably coupled with the blood circuit to allow the portion of the patient's blood to flow therethrough without being sieved and having a molecular weight cutoff of between 150,000 Daltons and 1,000,000 Daltons; the very large pore hemofilter operable to form a filtered bloodstream comprising an unsieved portion and an ultrafiltrate stream; the ultrafiltrate stream containing the target molecules and the target complex molecules removed from the portion of the patient's blood flowing through the very large pore hemofilter and the ultrafiltrate stream not containing significant amounts of immunoglobulins; the extracorporeal blood circuit operable to remove an initially high volume ultrafiltrate stream of at least approximately two liters per hour; a replacement fluid kit attached to the extracorporeal blood circuit during hemofiltration of the portion of the patient's blood; the replacement fluid kit having a reservoir source operable to supply plasma colloid replacement fluid to the patient's blood circulatory system; the reservoir having at least one port operable to communicate the replacement fluid from the reservoir source; a coupling operable to allow flow of the replacement fluid from the port to the extracorporeal blood circuit; the replacement fluid including a pharmaceutical grade balanced salt solution and clean target receptor molecules suitable for infusion into the patient's blood circulatory system; the clean target receptor molecules selected to replace the target molecules and target complex molecules disposed in the ultrafiltrate stream; and the replacement fluid having a concentration of albumin at least sufficient to maintain a prescribed albumin concentration in the patient's blood circulatory system.

7. An extracorporeal blood circuit for the filtration of a patient's blood, the circuit comprising: the blood circuit operable to remove a portion of the patient's blood to a blood filter and to return a an unsieved portion of the patient's blood from a blood source; the blood filter operably coupled with the blood circuit to allow the portion of the patient's blood to flow therethrough without being sieved; the blood filter having an effective molecular weight cutoff of between 150,000 Daltons and 1,000,000 Daltons and sufficiently large to sieve an ultrafiltrate stream having more than a nominal amount of target complex molecules from the portion of the patient's blood and adapted to avoid removal of significant amounts of immunoglobulins as part of the ultrafiltrate stream; an ultrafiltrate line operable to allow the ultrafiltrate stream to flow from the blood filter through the ultrafiltrate line at a rate between at least two liters per hour and five liters per hour; a waste reservoir in fluid communication with the ultrafiltrate line so as to receive at least a portion of the ultrafiltrate stream and to hold the ultrafiltrate separate from the blood source; and an albumin source operable to infuse albumin and optionally other clean target receptor molecules into a filtered bloodstream exiting from the blood filter to maintain a serum albumin sufficient to preserve adequate plasma oncofic pressure for the patient and to replenish ongoing losses from the patient's blood.

8. An extracorporeal blood circuit for filtration of a patient's blood to remove target molecules and target complex molecules, the circuit comprising: the circuit operable to remove a portion of the patient's blood to a very large pore hemofilter and to return an unsieved portion of the patient's blood from a blood source; the very large pore hemofilter operably coupled with the circuit to allow the portion of the patient's blood to flow therethrough without being sieved; the very large pore hemofilter having a molecular weight cutoff greater than 150,000 Daltons to sieve more than a nominal amount of the target complex molecules from the portion of the patient's blood; the molecular weight cutoff less than approximately 500,000 Daltons to avoid removal of undesired amounts of immunoglobulins to prevent increasing the risk of opportunistic infection; a fluid source having a fluid reservoir containing a replacement fluid with clean target receptor molecules selected to replace target receptor molecules contaminated with at least one inflammatory mediator removed from the portion of the patient's blood during the very large pore hemofiltration; and the circuit operable to remove an ultrafiltrate stream of at least one liter per hour from the very large pore hemofilter and to isolate at least a portion of the ultrafiltrate stream from the blood source for disposal.

9. The circuit of claim 8 wherein the replacement fluid further comprises a concentration of albumin greater than approximately 0.5 grams per one hundred milliliters.

10. An extracorporeal blood circuit operable to remove target molecules and target complex molecules from a portion of a patient's blood flowing through the blood circuit to a very large pore hemofilter and return an unsieved portion of the filtered blood to the patient comprising: the very large pore hemofilter operably coupled with the blood circuit to allow the unsieved portion of the patient's blood to flow therethrough; the very large pore hemofilter having a molecular weight cutoff of between about 150,000 Daltons and about 1,000,000 Daltons and operable to sieve the target molecules and target complex molecules from the bloodstream and the molecular weight cutoff operable to avoid removal of significant amounts of immunoglobulin to prevent increasing the risk of opportunistic infection; the circuit containing a valve for controlling discard of an ultrafiltrate stream between at least two liters per hour and twenty liters per hour; the ultrafiltrate stream containing target molecules and target complex molecules removed from the bloodstream using the very large pore hemofilter; an ultrafiltrate tubing operable to flow the ultrafiltrate from the very large pore hemofilter to the valve; a return tubing operable to return the unsieved portion of the patient's blood to the patient; a source of replacement fluid having clean target receptor molecules operable to replenish ongoing losses from the portion of the patient's blood flowing through the very large pore hemofilter including sufficient clean albumin to maintain adequate plasma oncotic pressure; and the clean target receptor molecules operable to attract additional inflammatory mediators and toxins from tissue spaces and tissue binding sites in the patient.

Description

TECHNICAL FIELD

The present invention relates generally to systems, methods, and devices used for hemofiltration. More specifically, the present invention relates to very large pore hemofiltration ("VLPH") for treating liver failure, for treating exogenous toxin exposures, and for treating inflammatory mediator-related diseases ("IMRD") including sepsis and septic shock, which include systemic inflammatory response syndrome ("SIRS"), multiorgan system dysfunction syndrome ("MODS"), multiorgan system failure ("MOSF"),and compensatory anti-inflammatory response syndrome ("CARS"), and for treating other conditions associated with toxin circulating in a patient's blood.

BACKGROUND OF THE INVENTION

Discussed herein are three subjects. First, devices and procedures for the therapeutic manipulation of target receptor molecules, target complex molecules, and target molecules in immune mediator related disease, and hepatic failure, and exogenous intoxication. Second, selected physiologic roles of albumin in health, immune mediator related disease, hepatic failure and exogenous intoxication, in particular effects of oncotic pressure and binding of physiologic or pathologic molecules. Third, the physiologic roles of soluble receptor and carrier molecules with respect to pro- and anti-inflammatory mediators ("IM") in particular and toxins in general.

Medical Blood Filtration: Treatment of certain diseases by filtration of blood is well established medical practice. Dialysis, using dialysis filters, which remove molecules with molecular weights up to 5,000 to 10,000 Dalton, is used to treat chronic and some acute renal failure. Conventional hemofiltration, discussed below, is used to treat acute renal failure, and in some cases, chronic renal failure. Plasmapheresis, using plasma filters or centrifuge techniques which remove molecules with molecular weights of 1,000,000 to 5,000,000 Dalton or more, is used to treat diseases associated with high molecular weight pathologic immunoglobulins or immune complexes, (e.g., multiple myeloma, lupus vasculitis, etc.).

Conventional hemofilters are well known medical devices commonly used to filter the blood of a patient with acute renal failure, and in some cases, chronic renal failure. The hemofilter may be used either for convective or dialytic depuration of blood. Many hemofilters are on the market with various characteristics. However, conventionally they all share one major characteristic, which is a nominal or effective molecular weight cutoff of less than 69,000 Dalton--the molecular weight of albumin. Conventional hemofilters are generally designed to minimize or avoid sieving of albumin. The reason is that the removal of albumin in the application of renal failure treatment is of no benefit, and would be a deleterious side effect, because the oncotic pressure of plasma would be reduced and edema promoted. Albumin could be replaced, but would add cost and risk with no therapeutic benefit. Therefore, conventional hemofilters are designed to avoid sieving of albumin.

Plasmapheresis has the objective of sieving all plasma proteins, especially all classes of immunoglobulins and immune complexes. This requires a molecular weight cutoff of from 1 million to 5 million Dalton, or more. Plasmapheresis membranes are designed to reject only cellular elements of blood, and are the most extreme of the blood filtration techniques designed to produce an acellular filtrate.

Physiology of Albumin and Soluble Receptor and Carrier Molecules:

Serum albumin serves a number of vital functions, two of these are its oncotic function and its chemical binding and transport of both physiologic and pathologic molecules. Albumin provides 80% of the oncotic pressure of plasma. This oncotic pressure keeps plasma water within the blood-vascular space, preserving the plasma water component of the blood volume, and preventing tissue edema by drawing tissue fluid back into the plasma from tissue. Albumin normally is present in human plasma at a concentration of about 3.5 to 5.0 gm/100 ml. If albumin concentration declines, typically to a concentration of <2.5 gm/100 ml, then oncotic pressure drops below its critical level, and edema fluid accumulates in tissues, body cavities (e.g., ascites, pleural effusion), and in air spaces in the lung (e.g., pulmonary edema). This accumulation of edema fluid may result in vital organ dysfunction, increased susceptibility to infection, and hyper-coagulable states. Thus, depletion of albumin molecules to the extent that oncotic pressure is excessively reduced is to be avoided.

The chemical binding and transport functions of albumin are numerous. In most cases, potentially biologically active molecules in the blood circulation only have their biologic effects when they are free in suspension or solution in the plasma water. In this free state, the molecule is able to interact with its receptor(s) to bring about biologic effects. Such biologic actions may be agonistic or antagonistic. Binding of a potentially biologically active molecule to albumin or other carrier or soluble receptor molecule usually inactivates the molecule by preventing combination with its tissue receptor. In some instances, the binding functions are part of normal physiologic process. For example when albumin binds calcium or magnesium ions, it is a dynamic process that helps to preserve the proper concentration of ionized calcium in the plasma water. If ionized calcium drops, calcium is released from albumin to restore normal plasma water ionized calcium. In other instances, the binding function of albumin and other receptor molecules protects against disease causing molecules by participating in their inactivation and detoxification.

Another major function of albumin is its role in detoxification, in which it binds endogenous or exogenous toxins. In this role, albumin acts both to detoxify the toxin by binding and therefore inactivating it, and also as a carrier molecule, transporting the toxic molecule to the liver for chemical transformation (detoxification) and excretion, or to the kidney for excretion. Endogenous toxins arise from a great many pathologic bodily processes. During sepsis and septic shock, inflammatory mediators ("IM") are produced in excess. At the site of local tissue injury or infection, IM serve the vital immune functions of removal and healing of injured or dead tissue, or resisting or destroying infecting organisms. When IM become excessive and spill over into the general circulation, they may become toxic to the body causing the systemic inflammatory response syndrome, with complicating multiorgan dysfunction syndrome and multiorgan system failure. These IM are carried in the plasma bound to albumin, bound to other receptor molecules, or free in plasma water. Binding by albumin and other receptor molecules moderates and ablates the effects of circulating IM. When the binding capacity is exceeded, the circulating IM become much more toxic and the moderating effects of albumin-carrier molecule binding are exceeded.

Other diseases, such as rheumatoid arthritis, pemphigoid vulgaris, multiple sclerosis, lupus, graft versus host disease and similar conditions, are similarly caused by excess circulating IM. These conditions generally result from an autoimmune process in which IM, either physiologic or pathologic, are dysfunctionally produced and are therefore toxic in any amount, or produced in dysfunctionally large and toxic quantities. Sepsis-septic shock and the autoimmune diseases, each resulting from dysfunctional and/or dysfunctionally abundant IM, may be referred to in aggregate as Inflammatory Mediator Related Disease ("IMRD").

Liver failure is a complex disorder with an intricate pathophysiology and diverse effects on many vital organs. It is characterized by the accumulation in the body of many toxins that arise from body metabolic processes, which, under normal conditions, are quickly detoxified and eliminated by the liver, but which, in liver failure, accumulate in the body. The pathologic effects of liver failure are varied and include bleeding (failure of liver to produce clotting factors), infection (failure of liver to remove organisms translocated from the gut into the portal circulation), and the accumulation, as noted above, of various liver failure toxic substances which have been only partially characterized. The lethal effect of these liver failure toxic substances is hepatic coma with progressive cerebral edema and eventual brain stem herniation and death. Liver failure toxic substances are extensively bound by albumin. While several supportive therapies are in use to reduce these toxic substances and ameliorate the effects of hepatic failure, none have shown a clear or consistent benefit.

Exogenous toxin exposures such as suicide attempts, accidental toxin ingestions and environmental (industrial, agricultural, etc.) toxin exposures are of great diversity. The majority of these exogenous toxins are bound to albumin and other tissues, thus excretion by natural means (kidney elimination) or artificial means (dialysis) is severely limited. Therapy for nearly all these intoxications is supportive only. In most intoxications, which are mild or moderate, simple supportive care and allowing the body's own detoxification mechanisms time to work, is satisfactory. However, in severe intoxications, particularly with more dangerous chemicals (e.g., tricyclic antidepressants, aspirin, etc) removal by some extracorporeal means would be desirable. However, current methods are not adequate to overcome binding of exogenous toxins to albumin or tissue and remove them from the body.

Not all carrier molecules inhibit the function of the bound molecule; in some cases, biologic activity of the bound molecule is enhanced by binding to a carrier molecule. For example, lipopolysaccharide (endotoxin) stimulation of cyotkine production is enhanced by low levels of lipopolysaccharide binding protein (LBP). LBP is an acute phase carrier protein made by the liver.

SUMMARY OF THE INVENTION

In accordance with teachings of the present invention, a method and system for a new type of hemofiltration referred to as very large pore hemofiltration ("VLPH") is provided. Very large pore hemofiltration includes sustained removal of albumin and similar large receptor molecules and carrier molecules for the purpose of removing both bound and unbound pathologic molecules or toxins. U.S. Pat. No. 5,571,418 teaches the use of a hemofilter with a nominal molecular weight cutoff of 100 to 150 kiloDalton (1,000 Daltons=1 kiloDalton) for the treatment of sepsis, septic shock, and other conditions. The purpose of the filter in the '418 patent is to remove circulating IM. A 100-kiloDalton hemofilter may initially sieve small amounts of albumin, but even if it does, albumin sieving quickly becomes negligible due to membrane polarization soon after the procedure begins.

Membrane polarization is well recognized in filtration process of blood and consists of the accumulation of a protein layer or "cake" on the membrane surface which characteristically reduces its sieving capacity (e.g., effective molecular weight cutoff) by 30 to 50%. The application of the 100 kD filter accepts the possibility of minor albumin sieving as a side effect of its therapeutic application. Therefore, a very large pore hemofiltration membrane suitable for the therapy of the present invention often requires a nominal molecular weight cutoff of >100 kD. Hemofilters with a nominal molecular weight cutoff <100 kiloDalton are generally not capable of sustained effective removal of albumin, and large receptor and carrier molecules, especially when target molecules are bound to them.

VLPH is distinct from plasmapheresis in the following critical ways. First, VLPH seeks sieving of proteins such as albumin, soluble tumor necrosis factor receptor 75 (molecular weight=75,000 Dalton), and similar soluble receptor and carrier molecules for the reasons stated above. VLPH specifically avoids removal of significant amounts of immunoglobulins and similar large molecules because removal of these molecules is associated with a marked increase in the risk of opportunistic infection.

Inflammatory mediator related disease ("IMRD"), liver failure, exogenous intoxication, and other conditions associated with toxins circulating in the blood are similar in that each is a severe pathologic process, often acutely life threatening, and in need of urgent or emergent therapy. Therefore, VLPH should generally be most effective when initial high volumes of ultrafiltrate are removed (exchanged for replacement fluid) for limited periods of time. Thus, the present invention will often be most effective at initial adult patient ultrafiltration rates of from 2-5 liters/hour, or even up to 15 to 20 liters/hour or more, and for initial treatment times ranging from about 4-10 hours, but generally not more than 24 hours at a time. Conventional hemofiltration produces ultrafiltration rates of about 1-2 liters/hour and is used on a continuous basis over a few to several days.

Devices and procedures, incorporating teachings of the present invention, fulfill longstanding needs for an effective therapy to treat IMRD, liver failure, exogenous toxin exposure and other conditions associated with toxins in the blood by removing target molecules and target complex molecules from a patient's blood. Such devices and procedures may be generally described as plasma colloid exchange therapy (PCET).

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete and thorough understanding of the present invention and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:

FIG. 1 is a schematic diagram showing one example of a very large pore hemofiltration system incorporating teachings of the present invention; and

FIG. 2 is a block diagram showing one example of a method for treating a wide variety of conditions associated with inflammatory mediators and bound or unbound toxins in a patient's blood in accordance with teachings of the present invention using a hemofiltration system, replacement fluid for ultrafiltrate discarded from the hemofiltration system and an optional ultrafiltrate recycling device.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the invention and its advantages are best understood by reference to FIGS. 1 and 2.

For purposes of this patent application, albumin, receptor molecules, and carrier molecules will be referred to collectively as "target receptor molecules". A wide variety of naturally occurring receptor molecules and carrier molecules may be satisfactorily used with this invention. Also, receptor molecules and carrier molecules may be designed and artificially created to bind with specific target molecules or general classes of target molecules. The term "clean target receptor molecule" refers to a receptor molecule or a carrier molecule which is not contaminated with or bound with a target molecule. The term "clean albumin" refers to albumin which is not contaminated with or bound with a target molecule.

For purposes of this patent application, albumin with bound IM and/or toxins, receptor molecules with bound IM and/or toxin, and carrier molecules with bound IM and/or toxin, will be referred to collectively as "target complex molecules". For purposes of this patent application, unbound IM, and unbound toxin (whether endogenous or exogenous) will be referred to collectively as "target molecules." Endogenous toxins include but are not limited to IM, liver failure related toxins, and metabolites of certain exogenous toxins. Exogenous toxins include chemicals such as medicine taken in excess, industrial and/or agricultural chemical exposures, and the like.

Various embodiments of the present invention include a process, method, and system to treat IMRD, to treat hepatic failure and coma, to treat exogenous intoxication, and/or to treat other conditions associated with bound and unbound toxins in a patient's blood including target molecules and target complex molecules.

One example of a very large pore hemofiltration (VLPH) system incorporating teachings of the present invention is shown in FIG. 1. System 90 may be used to treat mammals such as patient 100. System 90 may include a very large pore hemofilter 102, blood lines 101, 103, 105, 107 and ultrafiltrate lines 112, 127 and 121, source 150 of replacement fluid and optional ultrafiltrate recycling device 170. System 90 represents only one example of an extracorporeal blood circuit which may be used to treat patients in accordance with teachings of the present invention. For example, ultrafiltrate recycling device 170 may not be included in some systems used to treat a patient using hemofilter 102. For other systems, ultrafiltrate may flow directly from hemofilter 102 to waste reservoir 119.

Very large pore hemofilter 102 receives a stream of blood from patient or mammal 100 and removes ultrafiltrate from the stream of blood and thereby creates a stream of filtered blood and a stream of ultrafiltrate flowing through tubing 112. The filtered blood is preferably returned to patient 100. All or portions of the ultrafiltrate may be discarded to waste reservoir 119. Alternatively, all or portions of the ultrafiltrate may be cleaned and returned to patient 100.

Very large pore hemofilter 102 preferably sieves the ultrafiltrate from the blood stream. The ultrafiltrate will typically include a fraction of plasma water, electrolytes, peptides, proteins, target receptor molecules, target complex molecules, and target molecules. The sieved target molecules, target receptor molecules, and target complex molecules generally have a molecular size smaller than the nominal or effective pore size of the VLPH membrane (not expressly shown).

Very large pore hemofilter 102 is preferably formed from one or more biocompatible materials. In particular, very large pore hemofilter 102 may include a membrane disposed within case 102a. The membrane may be formed from the group of biocompatible materials (e.g., polysulfone, polyacrylonitrile, polymethylmethacrylate, polyvinyl-alcohol, polyamide, polycarbonate, etc.) and biocompatible cellulose derivatives. The case may be formed from polycarbonate or some other suitable biocompatible material. The VLPH membrane will generally remove albumin from the patient's blood. Depletion of albumin below acceptable levels will occur unless plasma colloid replacement fluid (described below) is provided in accordance with teachings of the present invention.

Various types of membranes may be used. Examples of such membranes include either a parallel plate or hollow fiber format. The membrane material may be any biocompatible material, typically polysulfone, polyacrylonitrile, polymethylmethacrylate, polyvinylalcohol, polyamide, polycarbonate, cellulose derivatives, and the like. The effective molecular weight cutoff will allow for effective sieving of target receptor molecules, target complex molecules, and target molecules, even after the membrane has undergone membrane polarization. The purpose of the membrane is to efficiently remove target receptor molecules, target complex molecules, and target molecules, as well as associated plasma water and associated solutes. The size and other sieving characteristics of albumin or other target receptor molecules may change when bound with various target molecules.

For the embodiment represented by system 90, first tubing 101 interfaces with patient 100 and blood pump 104. Blood pump 104 controls the flow of blood from patient 100. Blood exits from blood pump 104 through second tubing 103 and flows to hemofilter 102. Hemofilter 102 further interfaces with third tubing 105 and ultrafiltrate tubing 112. Filtered blood exiting hemofilter 102 through third tubing 105 flows to three-way joint 125 and fourth tubing 107 where it returns to patient 100.

Ultrafiltrate removed from the blood stream supplied by blood pump 104 to hemofilter 102 may flow through ultrafiltrate tubing 112 to three-way joint or three way valve 110 where the ultrafiltrate stream is discarded. Ultrafiltrate entering three-way joint 110 may be discarded through ultrafiltrate tubing 127, ultrafiltrate pump 106b, and discard ultrafiltrate tubing 121 to waste reservoir 119.

For some applications, ultrafiltrate recycling device 170 may be coupled with ultrafiltrate tubing 112 by tubing 172 and tubing 174. Ultrafiltrate recycling device 170 may include an adsorptive filter or other device operable to form clean ultrafiltrate by removing target molecules and target complex molecules from the ultrafiltrate. Control valve 176 may be disposed in ultrafiltrate tubing 112 between the respective junctions with tubing 172 and tubing 174. One or more control valves 178 and 180 may also be disposed in tubings 172 and 174 between ultrafiltrate recycling device 170 and ultrafiltrate tubing 112. For some treatment therapies, control valve 176 may be opened and control valves 178 and/or 180 closed so that all of the ultrafiltrate stream will flow from hemofilter 102 through tubing 112 to three-way joint 110 to waste reservoir 119. For other treatment therapies, control valve 176 may be closed and control valves 178 and 180 opened to direct the ultrafiltrate stream from hemofilter 102 through ultrafiltrate recycling device 170.

All or a selected portion of clean ultrafiltrate from ultrafiltrate recycling device 170 entering three-way joint 110 may be directed to ultrafiltrate return pump 106a and return ultrafiltrate tubing 129. The clean ultrafiltrate may flow through three-way joint 125 and tubing 107 to patient 100 along with the filtered blood stream. All or selected portions of clean ultrafiltrate may be directed from three-way joint 110 to waste reservoir 119.

The rate of blood flowing through blood pump 104 and the total amount of blood circulated through hemofilter 102 will depend on the condition of patient 100, the molecular weight cutoff of the associated hemofilter membrane, the body size of patient 100, and other requirements for effective treatment of the patient. The amount of blood, the blood flow rate and the duration of treatment are preferably determined on a case by case basis after factoring the weight, the age and the nature and severity of illness of patient 100. Often, blood flow rates may range from one hundred to two hundred milliliters/minute. Typically, total ultrafiltrate flow rate may range between one to nine liters per hour of which from zero to nine liters per hour may be discarded. The discard rate will be determined by the fluid balance requirements of patient 100 and the need for fluid removal. All clean ultrafiltrate not discarded may be returned to patient 100. The use of replacement fluid will be discussed later in more detail.

The composition of the material making up the blood pump, ultrafiltrate pumps, replacement fluid reservoir, tubing, ultrafiltrate tubing and ultrafiltrate recycling device is preferably a biocompatible material, such as polyvinylchloride, but not limited to this material. The tubing may be flexible and have dimensions complementary with associated hemofilter connections, ultrafiltrate recycling device connections, replacement fluid reservoir connection, joints, stop cocks, or pump heads.

Ultrafiltrate waste pump 106b may be used to pump a portion or all of the ultrafiltrate to waste reservoir 119. Ultrafiltrate return pump 106a may be used to pump a portion or all of the recycled or clean ultrafiltrate back to patient 100. Ultrafiltrate return pump 106a may also be used to infuse replacement fluid into patient 100. Tubing 107 transfers filtered blood along with replacement fluid and/or recycled ultrafiltrate or clean ultrafiltrate (if recycling is being done) to patient 100. Tubing 129 transfers recycled or clean ultrafiltrate and replacement fluid from the ultrafiltrate return pump 106a. The various pumps are all optional so long as sufficient blood circuit pres