# US 2014/0190886 A1 · Recirculating dialysate fluid circuit for blood measurement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0190886 A1 - Document ID: US20140190886A1 - Status: Published application - Kind: A1 - Application number: 13/836,538 - Filed: 2013-03-15 - Published: 2014-07-10 - Earliest claimed: 2013-01-09 - Assignees: Medtronic, Inc. - Inventors: Bryant J. Pudil; Thomas E. Meyer; David B. Lura; Martin T. Gerber - Web page: https://patentgrep.com/patent/US20140190886A1 ## CPC - A61M 1/1696: {with dialysate regeneration} - A61M 1/14: Dialysis systems; Artificial kidneys; Blood oxygenators (semi-permeable membranes characterised by the material, manufacturing processes therefor B01D71/00){; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis} - A61M 1/1605: {Physical characteristics of the dialysate fluid} - A61M 1/1609: {after use, i.e. downstream of dialyser} - A61M 1/1613: {Profiling or modelling of patient or predicted treatment evolution or outcome} - A61M 1/1619: {Sampled collection of used dialysate, i.e. obviating the need for recovery of whole dialysate quantity for post-dialysis analysis} - A61M 1/165: {with a dialyser bypass on the dialysis fluid line} - A61M 1/1694: {with recirculating dialysing liquid} - A61M 1/28: Peritoneal dialysis {; Other peritoneal treatment, e.g. oxygenation} - A61M 1/3406: {Physical characteristics of the filtrate, e.g. urea} - A61M 1/3472: {with treatment of the filtrate} - A61M 1/3486: {Biological, chemical treatment, e.g. chemical precipitation; treatment by absorbents} - B01D 15/08: Selective adsorption, e.g. chromatography - B01D 15/362: {Cation-exchange} - A61M 2202/0498: Urea - A61M 2205/05: combined with other kinds of therapy - A61M 2205/15: Detection of leaks - A61M 2205/3317: Electromagnetic, inductive or dielectric measuring means - A61M 2205/3324: PH measuring means - A61M 2205/3334: Measuring or controlling the flow rate - A61M: DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY (introducing media into or onto the bodies of animals A61D7/00; means for inserting tampons A61F13/26; devices for administering food or medicines orally A61J; containers for collecting, storing or administering blood or medical fluids A61J1/05); DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY (surgery A61B; chemical aspects of surgical articles A61L); DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR {(Electrotherapy, e.g. producing anaesthesia by the use of alternating or intermittent currents A61N1/36021)} - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) ## Abstract A blood based solute monitoring system for measuring at least one blood solute species that has a first recirculation flow path in fluid communication with a dialyzer. The first recirculation flow path is configured to allow a fluid to recirculate through a dialyzer such that the concentration of at least one solute species in the fluid becomes equilibrated to the solute species concentration of the blood in a blood compartment of the dialyzer. The blood solute monitoring system has at least one sensor to measure a fluid characteristic. ## Claims ### Claim 1 A blood based solute monitoring system for measuring at least one blood solute species, comprising: a first recirculation flow path in fluid communication with a dialyzer wherein the first recirculation flow path is configured to allow a fluid to recirculate through the dialyzer such that the concentration of at least one solute species in the fluid becomes equilibrated to the solute species concentration of the blood in a blood compartment of the dialyzer; and at least one sensor to measure a fluid characteristic of the fluid. ### Claim 2 (depends on 1) The blood based solute monitoring system of claim 1, further comprising a second flow path that passes the fluid through said dialyzer wherein the at least one solute species in the fluid does not become equilibrated with the solute species in the blood in the blood compartment of the dialyzer. ### Claim 3 (depends on 2) The blood based solute monitoring system of claim 2, with the proviso that the at least one solute species in the fluid in the second flow path is not equilibrated with the solute species in the blood in the blood compartment of the dialyzer. ### Claim 4 (depends on 2) The blood based solute monitoring system of claim 2, wherein the second flow path is a sorbent regenerated dialysate flow path. ### Claim 5 (depends on 2) The blood based solute monitoring system of claim 2, wherein the second flow path is a controlled compliant flow path. ### Claim 6 (depends on 1) The blood based solute monitoring system of claim 1, wherein the first recirculation flow path has a small volume and a control valve for selectively metering fluid in and out of the first recirculation flow path. ### Claim 7 (depends on 1) The blood based solute monitoring system of claim 1, wherein the system selectively meters fluid into and out of the first recirculation flow path using any one of a control pump, a water pump, an acid concentrate pump, a replacement fluid pump, and combinations thereof. ### Claim 8 (depends on 1) The blood based solute monitoring system of claim 1, wherein the system is capable of moving fluid bi-directionally in the first recirculation flow path. ### Claim 9 (depends on 6) The blood based solute monitoring system of claim 6, wherein the first recirculation flow path is in fluid communication with a REDY system. ### Claim 10 (depends on 1) The blood based solute monitoring system of claim 1, wherein dialysate is recirculated through the sorbent cartridge and not the dialyzer to create a baseline concentration. and directed through the dialyzer and a solute concentration profile is measured and used to determine the solute clearance through the dialyzer ### Claim 11 (depends on 1) The blood based solute monitoring system of claim 1, wherein the equilibration takes less than any one of 10 minutes, 7 minutes, 5 minutes, 3 minutes, 2 minutes, and 1 minute. ### Claim 12 (depends on 1) The blood based solute monitoring system of claim 1, further comprising a control mechanism to decrease equilibration time by increasing dialysate and/or blood flow during fluid flow through the first recirculation flow path. ### Claim 13 (depends on 1) The blood based solute monitoring system of claim 1, further comprising a control mechanism to decrease equilibration time by continuing to perform ultrafiltration during fluid flow through the first recirculation flow path with or without increased rate of fluid flows. ### Claim 14 (depends on 1) The blood based solute monitoring system of claim 1, wherein the first recirculation flow path has a void volume of components and conduits of less than a volume from the group consisting of 1.0 L, 0.5 L, 0.4 L, 0.3 L, 0.2 L, and 0.1 L. ### Claim 15 (depends on 1, 2) The blood based solute monitoring system of claim 1 or 2, further comprising a valve, wherein operation of the valve determines whether the fluid flows through the first recirculation flow path or the second flow path. ### Claim 16 (depends on 1) The blood based solute monitoring system of claim 1, further comprising a pump, wherein operation of the pump causes the fluid to flow through the first recirculation flow path. ### Claim 17 (depends on 1) The blood based solute monitoring system of claim 1, wherein the sensor is an ion selective sensor. ### Claim 18 (depends on 1) The blood based solute monitoring system of claim 1, further comprising at least two sensors to measure the fluid characteristic. ### Claim 19 (depends on 18) The blood based solute monitoring system of claim 18, wherein the at least two sensors include a conductivity sensor. ### Claim 20 (depends on 18) The blood based solute monitoring system of claim 18, wherein the at least two sensors include any one of a potassium sensor, a bicarbonate sensor, and an ammonia sensor. ### Claim 21 (depends on 19) The blood based solute monitoring system of claim 19 wherein the conductivity sensor is used to determine when equilibration with the blood has been achieved. ### Claim 22 (depends on 19) The blood based solute monitoring system of claim 19 wherein the conductivity sensor is used as a measure of the sodium concentration of the blood. ### Claim 23 (depends on 22) The blood based solute monitoring system of claim 22, wherein the sodium concentration is measured at the start of a therapy session to determine a pre-dialysis blood sodium concentration of a subject and is used to profile the dialysate sodium concentration during the therapy session. ### Claim 24 (depends on 1, 18) The blood based solute monitoring system of claim 1 or 18, wherein the at least one sensor is a pH sensor. ### Claim 25 (depends on 1) The blood based solute monitoring system of claim 1, wherein the blood solute monitoring system is in fluid communication with a controlled compliant flow path. ### Claim 26 (depends on 1) The blood based solute monitoring system of claim 1, further comprising a sorbent regeneration system for regenerating a dialysate and returning the dialysate to the dialyzer. ### Claim 27 (depends on 26) The blood based solute monitoring system of claim 26, wherein the fluid flowing in the first recirculation flow path through the dialyzer does not pass through one or more material layers of the sorbent regeneration system. ### Claim 28 (depends on 27) The blood based solute monitoring system of claim 27, wherein at least one said material layer comprises one or more selected from a urease-containing material, alumina, zirconium phosphate, zirconium oxide, a divalent cation exchanger, activated carbon, and mixtures thereof. ### Claim 29 (depends on 27) The blood based solute monitoring system of claim 27, wherein at least one material layer containing urease is present in the first recirculation flow path. ### Claim 30 (depends on 26) The blood based solute monitoring system of claim 26, wherein the dialysate flowing in the first recirculation flow path contacts material layers within the sorbent regeneration system in a defined sequence. ### Claim 31 (depends on 26) The blood based solute monitoring system of claim 26, further comprising an electrolyte bolus injector. ### Claim 32 (depends on 31) The blood based solute monitoring system of claim 31, wherein the electrolyte bolus injector is located in the first recirculation flow path at a position downstream from a dialysate outlet of the dialyzer and upstream of the sorbent regeneration system, and the monitoring system monitors fluid at one or more positions in the first recirculation flow path selected from the group consisting of: a first position downstream from the dialyzer outlet and downstream from the electrolyte bolus injector where the fluid has not contacted any material layer of the sorbent regeneration system; a second position where the fluid has contacted a urease-containing material layer; a third position where the fluid has contacted a material layer other than the urease-containing material layer; and a fourth position in fluid communication with dialysate eluted from an outlet of the dialyzer and positioned upstream from the electrolyte bolus injector. ### Claim 33 (depends on 32) The blood based solute monitoring system of claim 32, wherein the fluid at the second position has only contacted the urease-containing material layer. ### Claim 34 (depends on 32) The blood based solute monitoring system of claim 32, wherein the blood solute monitoring system further measures the conductivity of the fluid at one or more positions within the controlled compliant flow path. ### Claim 35 (depends on 32) The blood based solute monitoring system of claim 32, further comprising at least one sensor to measure the conductivity of the fluid at one or more positions within the sorbent regeneration system. ### Claim 36 (depends on 1) The blood based solute based monitoring system of claim 1, further comprising one or more selected from the group consisting of: an acid feed supplied to the controlled compliant flow path; a bicarbonate feed; and a water feed. ### Claim 37 (depends on 1) The blood based solute monitoring system of claim 1 for measuring the conductivity of a dialysate, further comprising: a sorbent regeneration system having a plurality of material layers within the sorbent regeneration system, wherein the dialysate exiting a dialyzer is conveyed through the sorbent regeneration system. ### Claim 38 (depends on 37) The blood based solute monitoring system of claim 37, further comprising a controlled compliant flow path circulating the dialysate between the dialyzer and the sorbent regeneration system. ### Claim 39 (depends on 1) The blood based solute based monitoring system of claim 1 that forms part of a hemodialysis or hemodiafiltration system. ### Claim 40 A method for measuring the solute concentration of at least one blood solute species during a fluid therapy, comprising the steps of: switching fluid flow from a first flow path to a dialyzer recirculation flow path; equilibrating a dialysate with a blood side of a dialyzer; and measuring the solute concentration in the dialysate that has been equilibrated with the blood side of the dialyzer. ### Claim 41 (depends on 40) The method of claim 40, further comprising the step of switching flow from the dialyzer recirculation flow path to the first flow path for continuing with the fluid therapy. ### Claim 42 A method for measuring BUN via the use of fluid therapy device including a sorbent regeneration system and a dialyzer, comprising the steps of: switching fluid flow in the fluid therapy device from a first flow path to a sorbent bypass fluid path; recirculating a dialysate through the dialyzer; and equilibrating the dialysate with blood in the blood side of the dialyzer. ### Claim 43 (depends on 42) The method of claim 42, further comprising: switching the fluid flow from the sorbent bypass fluid path to a non-bypass path; and measuring an ammonium ion concentration of the equilibrated dialysate after contacting urease in the sorbent regenerating system. ### Claim 44 (depends on 43) The method of claim 43, further comprising the step of continuing with dialysis. ### Claim 45 A method for measuring the solute concentration of at least one blood solute species, comprising the steps of: switching fluid flow in a fluid therapy device having a sorbent regeneration system and a dialyzer from a first flow path to a sorbent bypass fluid path; recirculating a dialysate through the dialyzer; and equilibrating the dialysate with blood in the blood side of the dialyzer; and measuring the conductivity of the equilibrated dialysate before the dialysate has contacted a predetermined layer or sequence of layers to provide a first conductivity value; and switching the fluid flow from the sorbent bypass fluid path to cause the equilibrated dialysate to contact a predetermined material layer or sequence of material layers in the sorbent system; and measuring the conductivity of the equilibrated dialysate after it has contacted the predetermined material layer or sequence of material layers to provide a second conductivity value. ### Claim 46 (depends on 45) The method of claim 45, further comprising the step of determining a solute concentration according to a predetermined relationship between conductivity and solute concentration. ### Claim 47 (depends on 46) The method of claim 46, wherein the solute concentration is based at least in part upon a difference of the second conductivity value and the first conductivity value. ### Claim 48 (depends on 46) The method of claim 46, further comprising the step of continuing with dialysis. ### Claim 49 (depends on 45) The method of claim 45, wherein the contacted material contains urease, the blood solute concentration measured is BUN and the sensed fluid characteristic is the conductivity of the fluid. ### Claim 50 (depends on 45) The method of claim 45, further comprising: measuring the conductivity of a second non-equilibrated dialysate before contacting a urease containing material to provide a third conductivity value; measuring the conductivity of the second non-equilibrated dialysate after contacting a urease containing material to provide a fourth value; and determining the effective urea clearance of the dialyzer from the first, second, third and fourth conductivity values. ### Claim 51 (depends on 50) The method of claim 50, wherein one or more determinations of the effective clearance of a dialyzer is used to monitor the performance of a therapy session. ### Claim 52 A method to measure BUN (blood urea nitrogen), comprising: measuring a first conductivity value of a dialysate flowing from an outlet of a dialyzer not having contacted a urease containing material layer of a sorbent regeneration system; measuring a second conductivity value of the dialysate flowing from the outlet of the dialyzer after the fluid has contacted the urease containing material layer of the sorbent regeneration system; intermittently providing an electrolyte bolus or diluent to a dialysate flow path and measuring a bolus conductivity of the dialysate passing to the dialyzer to provide a third conductivity value; measuring a bolus conductivity of the dialysate passing from the dialyzer to provide a fourth conductivity value; and determining the effective clearance of the dialyzer from the third and fourth conductivity values. ### Claim 53 (depends on 52) The method of claim 52, further comprising: determining the BUN from the effective clearance of the dialyzer from the first and second conductivity values. ### Claim 54 (depends on 53) The method of claim 53, further comprising: determining the blood concentration of a solute from the said effective clearance of the dialyzer from said first and second equilibrated conductivity values. ### Claim 55 (depends on 52) The method of claim 52, further comprising the step of determining a urea content of the dialysate flowing from the dialyzer based at least in part on the difference in conductivity between the first and second conductivity values. ### Claim 56 (depends on 52) The method of claim 52, wherein the dialysate contacts a plurality of materials of the sorbent regeneration system in a sequential order. ### Claim 57 (depends on 52) The method of claim 52, wherein the sorbent regeneration system includes one or more sorbent cartridges which in turn include an ion exchange resin selective for calcium ions and magnesium ions and releasing hydrogen ions in exchange. ### Claim 58 (depends on 52) The method of claim 52, further comprising: determining a third conductivity value of the equilibrated dialysate that has contacted an additional material layer other than the material layer(s) contacted by the fluid of the first or second conductivity value; and determining the blood solute concentration of at least a second blood solute from either the second and third conductivity values or the first and third conductivity values. ### Claim 59 (depends on 40, 42, 45, 52) A method of claims 40, 42, 45 and 52 for calculating one of the selected measures BUN (blood urea nitrogen), URR (urea reduction ratio), Kt/V, eKt/V (equilibrated Kt/V), and PCR (protein catabolic rate), wherein k stands for dialyzer clearance rate, t stands for dialysis time, and V stands for volume of distribution of urea. ### Claim 60 (depends on 40, 42, 45, 52) A method of claims 40, 42, 45 and 52 determining the level or concentration of a solute selected from the group of K, Mg, Ca, pH, bicarbonate, and glucose. ### Claim 61 (depends on 59) The method of claim 59, wherein URR is determined by calculating a first BUN prior to dialysis and a second BUN post dialysis. ### Claim 62 (depends on 59) The method of claim 59, wherein Kt/V, eKt/V and PCR are each determined based on a difference between the first and second conductivity values.