NZ619246B2 - Blood treatment apparatus adapted to preserve parts thereof - Google Patents

Abstract

Disclose is a blood treatment apparatus adapted to preserve a blood treatment unit (20) between blood treatment sessions. The blood treatment apparatus is configured to i) perform a blood treatment session and thereby use the blood treatment unit (20), ii) fill the blood treatment unit (20) with a preservation fluid comprising at least one treatment fluid concentrate of a type that is used to prepare the treatment fluid and having a pH value less than 4.5, iii) maintain the preservation fluid in the blood treatment unit (20) until a next blood treatment session is prepared, iv) dispatch the preservation fluid from the blood treatment unit (20) in preparation of a next blood treatment session, and v) perform a next blood treatment session and thereby extend the use of the blood treatment unit (20). reservation fluid comprising at least one treatment fluid concentrate of a type that is used to prepare the treatment fluid and having a pH value less than 4.5, iii) maintain the preservation fluid in the blood treatment unit (20) until a next blood treatment session is prepared, iv) dispatch the preservation fluid from the blood treatment unit (20) in preparation of a next blood treatment session, and v) perform a next blood treatment session and thereby extend the use of the blood treatment unit (20).

Description

BLOOD lRfiAlMfiNl A? BARAlUS ADABl Ll. D lO BRfiS fiRVfi BARlS lH fiRfiOE Technical Field The t invention generally relates to a blood treatment apparatus and ds for preserving parts ll the blood treatment appara ZUS.

Background Today blood Lrea ,men u apparatuses are used for extracorporeal blood area oment which involves withdrawing blood from a patient, treating the blood and ret Jrning the treated blood to the patient. For this purpose an extracorporea' blood ‘low circuit (blood line) is used which is connected to a blood vessel access of the patient, typically via one or more access devices such as needles or ca:heters ed into a blood vessel of the patient. Depending on method of blood ent, the blood may be withdrawn from the patient, passed through a blood treatment unit (e.g. dialyzer) and ed to the patient via tqe same or another blood vessel access device. Simultaneously a ‘luid line withdraws a treatment ‘luid (i .e. ‘resh dia' ysis Sluid) ‘rom a fluid source, passes L 1e ,reatment lluid tqrough the blood treatment Jnit where the blood is treated, and disposes used/spent en jluid to a drain. Txtracorporeal blood ureaumen u includes hemodialysis, hemodia:filtration, qemofiltration etc.

During blood treatment it is important that a patie at is not exposed to harm‘ul micrOOrganisms. For this reason, new and e b:_ood treatment units and bloodlines are typically used :or each blood treatment VV()2012/163737 session. Non—disposable parts, such as the flaid line, are typically disinfected on a regular basis to prevent microbial growth therein. ?arts in contac, wi,h blood, such as the blood line and the blood treaomeq, unit, are usually replaced with new ones when a new pa,ien, shall be treated but in some cases, the blood treaomen, un it and the blood line may be reused for treatment ol the same patient at a later time.

Such X: nd d us r quir s cl aning and disin:fection 0: contacting parts between blood ent sessions. A number 0: techniques have been developed :OI this purpose, which typically include use 0: cleaning fluids, UV—radiation and/or heat fOr removing or kil ling any harm u' microorganism.

A well—known cleaning solution is Renalin®, which has been used for b' ood treatment unit reuse for decades.

It is however very harmful , and care mus, be ,aken that all Renalin® is rinsed out of the blood treatment unit before it may be used again.

One e 0: a cleaning technique is disclosed in US6146536 where a qemodialyzer apparatus comprises a reasable dialyzer nembrane as well as reusable blood flow path and dia'ysis flow path units. The apparatus automatically primes itsel " and makes dialysis solution from dry chemicals, concentrates, and fresh water wqich is provided to the apparat as. After use, the apparatus tically prepares a ng and rinsing solution for the cleaning and rinsing ol ,he dialyzer membrane as well as the dialyzate and blood flow path means. r example 0: cleaning technique is given by US6022512 disclosing a cleaning and disinfecting met qod for treating the es 0: hemodialysis equipment that are exposed to a ate or purified water. The method VV()2012/163737 compri s s th I] US 0 : l ctrolyzed hyperacidity water l Or cleaning and disin:fection.

Known techniques are general:_y e of cleaning a blood line or a fluid line 0“ a b'ood treatme at apparatus such that various components may be reused. However, it is bel ieved that present cleaning techniques may be improved in the sense that required hardware components and/or use 0: cleaning ions may be d, while still SB. feguarding a patien from harmfu 1 micrOOrganisms and toxic substances and allowing extended use 0; components .

Summary It is an object o: the invention to at least partly ne one or more limitations 0: the prior art. In partic alar, it is an object to provide a blood treatment appara ,us tha allows e 'icient extended use 0: One or more componen':s while still arding a patient from harmfu 1 micrOOrganisms.

Hence a blood treatment appara :us is provided which is adapted to preserve a blood trea ,ment uni between blood trea:ment sessions. The blood treatment apparatus ses the blood treatment unit, a blood line configured to pass blood through the blood treatment unit and deliver treated blood to a target vessel, and a f'uid line configured to pass treatment flaid through the blood treatment unit and deliver ased/spen, treatment fluid to a drain. The blood ,reaomen, apparatas is configured to: i) m a blood ,reaomen, session and thereby use the blood ,reatment unis, ii) fill the blood treatment unit with a preservation flaid comprising at least one treatmen, fluid concenorate of a type ,hat is used to pr par oh tr atm nt 'luid, iii) maintain the preservation fluid in the blood treatment unit until a next blood treatment session is prepared, iv) dispatch the preservation fluid rom ,he blood treatment unit in preparation 0: a next blood treatment session, and v) perform a next blood ,reaomen, session and thereby extend the use 0: the blood ,reaomen, unit.

The blood treatment apparatus is advantageous in that growth 0“ i micrOOrganisms e 'iciently may be prevented by tne maintaining o: the preservation fluid in the blood ,reaomen, uni ,, which allows extended use 0; the blood ,reaomen, uni o. Typically, the ining I] the preservaoion 'luid in the blood treatment unit is achieved by "i'iing the blood treatment uni, with the vation uid and keeping the preservaoion 'luid in the blood ent uni t until a next blood treatment session is prepared. An additional advantage lies in the possibility to use ,he treatment fluid concentrates already mounted on the blood ,reaoment apparaous for ,he preservation, which is cost e ecoive and keep labor hours down within busy dialysis s.

The blood treatment may further be configured to fill the blood line with the preservation fluid and maintain the preservati on fluid in the blood line until the next blood treatment session is ed. "n 95 preparation o she next blood treatment session the preservation flaid is t nen dispatched from the blood line. In some ments the blood treatment unit and the blood line are arra nged as a common, disposable unit.

The blood treatment apparatus may also be configured to fill the fluid line with the preservation fluid and maintain the preservati on fluid in the f'uid 'ine until the next blood treatment session is prepared. "n 2012/059520 preparation 0: the next blood treatment session the preservation fluid is dispatched from ,he 'luid 'ine.

The preservation uid may have a pH value less than 4.5, less than 4.0, less than 3.0 or less than 2.0.

The preservation uid may comprise an electrolyte solution or an electrolyte solution having a water activity 0: less than 0.97, less than 0.94, or less than 0.86.

The preservation fluid may comprise an acidic eleCtrolyte solution, an acidic electrolyte solution having a pH value less than 4.5, an acidic electrolyte solution having a water activity 0: less than 0.97 , an acidic electrolyte solution having a pH value less than 4.5 and having a water activity 0: less than 0.97, or an acidic electrolyte on having any combination 0; above given ranges for pH and water activity.

In some embodiments the vation fluid comprises at least one 0“ hloric acid, citric acid, acetic acid, ylcystein, ascorbic acid, d—ketoglutarate, gluconic acid, or combinations thereo;.

The preservation fluid may comprise an A—concentrate o: a type that is used to pr par th tr atm nt fluid.

Such an A—concentrate may comprise an acid and e'ectro'ytes usually used to prepare a treatment fluid, except for onate.

The acid may be at least one 0'_ hydrochloric acid, citric acid, acetic acid, N—acetylcystein, ascorbic acid, d—ketoglutarate, gluconic acid, or combinations thereo;.

The eleCtrolytes may among others include at least one 0: sodium ions, calcium ions, potassium ions, magnesium ions and chloride ions, or combinations thereo;.

VV()2012/163737 This A—concentrate may be d to some , depending on the original concentrations 0: the component in the A—concentrate.

The preservation fluid may comprise only electrolytes, e.g. in form 0“ sodium chloride. Such a preservation fluid may be provided from a two—part A— trate provided from two containers, where one ner contains sodium de and the other CODtainer contains acid and ally additional olytes. By using only the container comprising the sodium chloride, a preservation fluid having a water activity 0: less than 0.97 may be ed.

The blood treatment apparatus may be configured to maintain the preservation fluid in the blood ,reatmen, unit for at least 8 hours until the next blood treatment session is prepared.

The blood treatment apparatus may be configured to, prior filling the blood treatment unit with t me preservation _:-|u_id, flush a rinsing fluid through the blood treatment u qit.

The rinsing uid may comprise treatment fluid, purified water, aline solution, or combinations I] s thereo;.

In some embodiments the blood trea omens apparatus is CODfigured to, pr ior "'I ling the blood ,reaument uni, witq the preservation uid, fill the blood treatment unit with a prote in solvent, maintain t 1e protein solvent in the blood trea tment uni, for a predetermined period 0: time, and dispatch the pro :ein solvent from the blood treatment unit.

The blood treatment apparatus may be configured to, prior filling the blood ,reatment unit with t 1e preservation fluid and after the dispatching the protein solvent, flush a rinsing fluid h the blood treatment unit.

Again, the rinsing fluid may comprise ent fluid, purified water, saline solution, or combinations thereof.

The protein solvent may comprise a bicarbonate containing solution. In some embodiments the protein solvent comprises a bicarbonate containing dialysate concentrate of a type that is used to prepare the treatment fluid passed through the blood treatment unit during the blood treatment operation. Optionally the protein solvent consists of a bicarbonate containing ate concentrate of a type that is used to prepare the treatment fluid passed h the blood treatment unit during the blood treatment ion.

The blood treatment tus may further comprise a processing unit and processing instructions which when executed on the processing unit cause the blood treatment apparatus to fill the blood treatment unit with the preservation fluid and maintain the preservation fluid in the blood treatment unit until a next blood treatment According to r aspect of the present invention a method is provided for a blood treatment tus that is adapted to preserve a blood treatment unit between blood treatment sessions. The blood treatment apparatus comprises the blood treatment unit, a blood line configured to pass blood through the blood treatment unit and deliver treated blood to a target vessel, and a fluid line configured to pass treatment fluid through the blood treatment unit and deliver used/spent treatment fluid to a drain. The method comprises g the blood treatment unit with a vation fluid that comprises at least one treatment fluid concentrate of a type that is used to prepare the ent fluid, once the blood treatment session is completed, and maintaining the preservation fluid in the blood treatment unit until a next blood treatment session is prepared. In preparation of a next blood treatment session the preservation fluid is dispatched from the blood treatment unit.

The method may be configured to implement any features discussed in connection with the blood treatment apparatus, and shares the corresponding ages.

Still other features, aspects and advantages of the invention will become apparent from the following detailed description when taken in conjunction with the claims and gs.

Brief Description of the Drawings Embodiments of the invention will now be described, by way of example, with nce to the accompanying tic drawings, in which Fig. 1 illustrates a blood treatment apparatus arranged to perform a blood treatment session, Fig. 2 illustrates the blood treatment apparatus of Fig. 1 when it is arranged to preserve a blood treatment unit, Fig. 3 is a flow chart of a general method for preserving a blood treatment unit, as performed by the blood treatment apparatus of Fig. 2, Fig. 4 is a flow chart of a more detailed embodiment of the method of Fig. 3, VV()2012/163737 Fig. 5 is a flow chart of another embodiment of the method of Fig. 3 and 4, and Figs 6 1 — 9 illustrate results of tests per‘ormed "OT” evaluating preservation O“ a blood treatment unit.

Detailed description of the Invention Fig. l With reference to Fig. 1 an embodiment of a blood treatment tus 2 for extracorporea' blood treatment, such as dialysis, is rated. The bl_ood treatment apparatns 2 (dialysis machine) comprises a blood treatment unit 20 and a b'ood 'ine 40 with a blood pump 44 arranged to withdraw b' ood ‘rom a blood source 13, pass the blood through the blood treatment unit 20 (in which tne blood is treated) and d l iv r th tr at d blood to a target vessel 14.

Within the blood treatment unit 20, a semi—permeable membrane 27 is t and divides the blood treatment 2O unit 20 into a blood tment 26 with a blood inlet 21 and a blood outlet 22, and a treatment fluid compartment that has a f'uid inlet 23 and a fluid outlet 24. The membrane 27 allows the treatment fluid to interact with the blood in a manner known within the art.

Blood line The blood line 40 is divided into an blood withdrawa' 'ine 4’ and a blood return line 42. The blood withdrawa' 'ine 4’ has a first connector device 71 that is ted to a ‘irst b'ood access device 131 in form OI- e.g. a needle arrangement or a catheter device that is inserted into the blood source 13. Tne blood return line 42 has a second connector device 72 that is connec:ed to VV()2012/163737 a second blood access devi ce 141 in :orm 0' e.g. a needle arrangement or a catheter device that is inserted into the targ t v ss 1 11. Th blood awal line 41 thereby connects the blood soarce 13 to the blood inlet 21 o: the blood treatment unit 20, whi;e the blood return line 42 ts the blood ou,le, 22 of the blood treatment unit 20 with the target vessel 14.

Both the blood withdrawal line ml and the blood return line 42 has clamping means mll, 421 (automatically and/or manually operated) allowing the blood withdrawal line 41 and the blood return line 42 to be repeatedly opened and , such that blood or some other fluid may be d tively prevented to pass through the respective connector device 71, 72. The clamping means 411, 421 may be opened and closed by receiving control signa's trom a processor unit 60 o: the blood treatment apparatus 2, such that a :low through the blood line 40 and blood compartment 26 may be controlled. The clamping means 411, 421 may also be ated with respeCtive 2O conneCtor device 71, 72 such that a disconnect aCtion automatically closes the passage through respective conneCtor device 71, 72.

For reasons 0“ clari, y o presentation, signal paths between the processor unit 60 and the ents it controls have been omitted from the drawings.

The contiguration O“ the blood line 40 and the blood treatment unit 20 may inc;ude various other components and control units generally present in blood treatment apparathes. The blood source 13 and target vessel 14 may 3O be a patient that receives blood treatment, but nay also be bags 0“ b'ood that are handled by operators. Even though the blood source 13 and the target vessel 14 are shown as separate units, they may be one and the same unit. The blood treatment apparatus 2 may be made to operate so as to perform single—needle dialysis and/or double—needle dialysis, and may therefore include some additional components conventionally used for this purpose.

Fluid line The blood ent apparatus 2 has a fluid 'ine 30 arranged to pass treatment 'luid (fresh dialysis fluid) h tqe blood treatment unit 20 and deliver used/spent treatment fluid to a drain 12. The drain 12 may, for example, be a fluid sink, a sewer, a receptacle or any other component or rge that may receive pent ,reatment fluid. The fluid line 30 is divided into an upstream fluid line 31 that connects a source 0; purified water ll with the fluid inlet 23 O“ the blood treatment uni, 20, and a downstream f'uid line 32 that connects the fluid outlet 24 of the blood ent unit with the drain l2. 2O In the upstream fluid line 31 the treatment fluid is prepared from purified water ll, a so called A— concentraoe, which may be contained in a container 15A connecoed to ,he upstream fluid 'ine 3’, and a so called 3—concentrate, which may be contained in a container ‘6? connecoed to ,he upstream fluid 'ine 3‘. The A— concenorate may be divided into two separate concenorates, as shown in Fig. l, in container l5Al and l5A2, but may also constitute a single A—concentrate in one container 15A. The mixing 0: the purified water and concentrates may be done ing to conventional techniques and may include measuring conductivity of the partly prepared concentrates as well as of ,he ,reaomen, fluid, this may include sending conductivity measurement values to the processor unit 60 which in turn may control the mixing process such that a desired composition is obtained for the treatment "'uid.

As will be explained below, the A—concentrate(s) and entrate may be used for preparing the treatment fluid as well as for preserving the blood treatment unit The flow through the downstream fluid line 39 to the drain 12 may also be controlled by the processor unit 60.

The blood treatment unit 20 and the blood line 40 may be arranged as a common, disposable unit 50 in the form 0' a anitary device that may be disconnected from the blood ent apparatus 2 and discarded once a blood ,reaomen, session 0: a patient is completed. When a new pa,ien, shall undertake treatment by the blood ent apparatus 2, a new and similar common unit 50 is ted to the apparatus 2 and a treatment session may commence. For allowing the disposable unit 50 to be connected to the apparatus 2, a third connector device 73 2O is arranged in the upstream fluid line 3l and a fourth connector device 74 is arranged in the downstream fluid line 32.

The third and fourth connector devices 73, 74 are par, of the able unit 50 or the blood ent unit 20, and the third connector device 73 is conneCted to an upstream connector device 311. The fourth connector device 74 is connected to a downstream conneCtor device 391. Alternatively or additionally, each 0: tie third and fourth connector devices 73, 74 and the upstream and downstream connector devices 311, 321 may have clamping means (not shown) separated or integrated as disclosed above for the connector s 71, 72, which may, manually or automatically, be opened and closed. 2012/059520 Concentrates Typically, the A—concentrate in the container l5A or the containers l5Al and l5A2 may be a concentrate, or concentrates ning acid and eleCtrolytes usually used to prepare a ent fluid, except sodium bicarbonate. The acid may be at least one o: hydrochloric acid and organic acid, such as citric acid, acetic acid, N—acetylcystein, ascorbic acid, glutarate, gluconic acid, etc or combinations thereo:. The electrolytes may among Others include at least one 0: sodium ions, calcium ions, potassium ions, magnesium ions, de ions, or ations ;.

The A—concentrate may further contain glucose or glucose—like compounds.

During a treatment session, the A—concentrate(s) is (are) mixed with purified water and contributes to the acidic component ol ,he treatment Sluid that is passed through the treatment unit 20 during the treatment session. The A—conceqtrate is highly acidic and may have a pH valJe 0: about 2 in its concentrated form. When diluted to the concentration used in preparation 0: the treatment Sluid, the pH value may be less than 4.5. An example 0; commercially available entrate contained in a container is a product named Soft?acm, which is provided by Gambro.

As disclosed above, the A—concentrate may also be provided from two containers, where one container contains sodium chloride (container l5Al) and the other container contains acid and optionally additional electrolytes which includes at least one 0: calcium ions, potassium ions, magnesium ions, chloride ions, or combinations thereo: (container l5A2). Such a two—part A— VV()2012/163737 concentrate system is provided by Gambro under the name Select?ag® and SelectCart®. This allows for control I] 0" 0; the concentration 0: sodium chloride in the treatment uid independently from the acid and other al electrolytes.

The 3—concentrate in ner 163 may comprise sodium bicarbonate, either as a concentrated solution or as a powder which may be dissolved by puri:fied water on— line in the blood treat nent appara:us 2 during the ent session. The 3—coqcentra:e contributes to the basic and bu "er component on the ,reaoment jluid that is passed through the en, unit 20 daring the treatment session. fically, the 3—concentra:e may comprise, or may consist o: , a sodium bicarbonate containing dialysate 1 concentrate o._ a type that is used to prepare the ureaomeno jluid that is passed through the blood ,reaomen, unit 20 during a blood treatment session. One example 0: a commercially available 3—concentrate is the product named 3iCart®, which is provided by Gambro.

The fluid line 30 may implement known techniques and standards, and may thus include various ents and control units lly used in blood treatment apparatuses, such as ‘ilters, ‘low meters, pressure sensors, additional pumps, valves and clamps etc. ?reservation Fluid The preservation ‘luid is a S'uid intended to prevent growoh o: pote itially l microorganisms b tw n or acm no s ssions. It may be used in the blood treatmen, uni o 20 and/or in the blood line 40. The preserva,ion Sluid may also be used to prevent growth I] pOtentially harm''ul microorganisms in the fluid line 30 b tw n tr atm nt s ssions. 12/163737 The preservation ‘luid is prepared in the blood treatment tus 2 nsing available concentrates. Thus, the preservaoion fluid may comprise at least one ,reatmen, flnid concentrate ol a type that is used to pr par oh or atm nt "'uid.

The preservation f'uid may comprise an A— concentrate. As disclosed above in the section “Concentrates”, such an A—concentrate may comprise acid and electrolytes usually used to prepare a treatment fluid \ except for bicarbonate. Such an A—concentrate may be diluted by purified water within di "eren, ranges depending on the original concentrations of ,he components in the A—concentrate.

The preservation fluid may further comprise only electrolytes. Such a preservation fluid may be provided from a two—part A—concentrate as disclosed above under the seCtion “Concentrates". By using only the container sing sodium chloride, a vation ‘luid only comprising electrolytes may be provided. 3y diluting such a sodium chloride concentrate, di"erent degree 0: water activity, aw, may be provided in tte preservation fluid.

Also here, a dilution may be d, maintaining a relatively low water activi 3y, aw, below 0.97.

Further, having such a rt A—concentrate also a"ows for the possibility to provide a preservation uid by only using the par s ol the A—concentrate comprising acid and optional Other electrolytes but :Olf sodium de. A preservation fluid having an acidic pH, a pH value below 4.5, bus not arily having a water aCtivity less than 0.97 nay then be provided. Also here di "erent dilutions ol ,he A—concentrate may be prepared to provide the preservation fluid, which then is mainly acidic.

VV()2012/163737 Tests Tests have shown that a vation fluid based on a diluted A—concentrate e 'iciently may preserve a blood treatment unit, a blood line and/or a fluid line by ting growth 0" harmtul microorganisms.

MicrOOrganisms require certain basic nutrients such as water, a source 0: energy, nitrogen, vitamins, and minerals for growth and maintenance of meoabolic functions. The amount and type of nuorienos required range widely depending on the type 0" rganism. "n order to prevent growth 0: rganisms one may restrict one or l 0: the above mentioned requirements for growth. Moreover, temperature, pH and water activity will also a "ect growth and survival 0; the microorganisms.

Microorganisms need available water for growth. The amount 0: water needed for growth 0: microorganisms varies. Th wat r r quir m nt is expressed in terms 0; available water or water activity (aw). The aw 0" purified water is 1.00 . Low aW has traditionally been used to control microbial deterioration o ood. now water aCtivity will also prevent microbial growth within pharmaceutical drug products.

Water ty may be combined with other preservauion "actors, such as temperature, high and low pH etc. to es ,ablish conditions that inhibit microorganisms. Di "erent microbial inhibitory factors that might nOt prevent growth when considered singly prevent growtq when used together.

Water ty is defined as the ratio 0: water vapour pressure of ,he product of interest to the vapour pressure 0: pure water at the same temperature, aW =9/90 where ?=vapour pressure 0: the solution and ?o=vapOLr pressure 0: pure water. The aW may be manipulated ir products by a number 0; means, ing addition 0; solutes such as salt or sugar, physical removal 0: water by drying, or binding of water to various macromolecules.

An aw value stated ‘or a micrOOrganism is generally the minimum aw which supports growth. In table 1 water activities required to support the growtq o; representative microorganisms are presented. At aW values below the m for growth, the microorganisms do not necessarily die. The microorganisms may qowever remain dormant. The limiting value 0: water activity for the growth 0: any microorganism is about 0.6 (US?<;112>).

Table 1. Water Activities (aw), measured at 25°C, ed to t the growth 0: representative nicroorganisms (adapoed jrom US? <lllZ>) ia Water Molds and yeasts Water ac:ivity ac:ivity (am) (am) Pseudomonas 0.97 Saccharomyces 0.90 aeruginosa cerevisiae Clostridium 0.95 Aspergillus niger 0.77 botulinum Type A Escherichia coli 0.95 Zygosachharomyces 0.62 rouxii hilic yeast) Clostridium 0.95 perfringens Lactobacillus 0.95 viridescens Salmonella spp. 0.95 VV()2012/163737 Enterobacter 0.94 aerogenes Micrococcus 0.93 lysodekticus Staphylococcus 0.86 aureus Halobacterium 0.75 (halophilic bacterium) Sodium chloride The preserving e"”ect o: sodium chloride (NaCl) involves more than the dehydrating capacity. The minimum aw for the growth 0: various micrOOrganisms is higher when NaCl is used ed to other s such as glycerol (Taormina, 2010). ?lease se table 2 below :OI water activity in various WaCl solutions.

Table 2. Water Accivicy 0 Various NaCl Solutions (adapted from EDA %ad %ug %ook) ?ercent NaCl (w/v) olal Water Activity 0.9 0.15 0.995 1.7 0.30 0.99 3.5 0.61 0.98 7.0 .20 0.96 .0 .77 0.94 3.0 2.31 0.92 16.0 2.83 0.90 22.0 3.81 0.86 In general, most rganisms grow beSt in an environment with a pl rang b tw n 6 8, y aSts 4.5—6.0 and filamentous fungi 3.5—4.0. The ability of low pH to restrict microbial growth has been used since the earlieSt times in the preservation o" "oods with acetic and laCtic acids. The ty and stabi'ity of macromolecules such as enzymes are great'y a"”ected by the acidity or alkalinity of the environment.

The ability 0“ micrOOrganisms to grow or survive in acidic environments s on the prOton concentration which is determined by the pH, and on the type 0: acid.

It is well known that although addition 0: strong acids has a more profound e "ect on pH they are less inhibitory than several weak organic acids at the same pH. The inhibitory properties 0“ many o_ o he organic acids, acetic, benzoic, citric, lactic, proprionic, and sorbic acids make them widely used as vatives. Organic acids are more e ecoive as preservatives in the non— dissociated state. In the non—diss ociaoed soaoes weak acid molecules pass through the membraqe. Inside the cell the acid dissociates and hence lowers the pl of the cytoplasm. The cell will try to ma intain its internal pH by neutralizing or by active transport of o 1e prOtons out from the cell. In doing so the cel l waste energy from growth related functions which hinder the . "” the pH 0: the environment is su 'iciently low and the extracell Jlar concentration of the acid high tqe cell will eventually die.

Growth studies 0: the baCteri a Staphylococcus, Serratia, and us showed that they could nOt increase in acidic (pl 5.6 or lower) total parenteral ons without lipids whereas the yeast Candida VV()2012/163737 albicans grew at pH 5.5 (Kuwahara et al ° I 2010).

Moreover growth studies with the yeast C. albicans adding di” "erent weak acids to the medium resulting in pH in the range 2.3 to 3.6 (acetic acid pH 3.6; c itric acid pl 2 .4, succinic acid pH 2. 8, tartaric acid pH 2.3) showed ,ha, the C. albicans grew as well as the control with pH 5.5 in media (De Seta e : al., 2009). However adding fumaric and maleic acid res Jlting in pH 2.6 and 2.0, respectively, resul ted in inhibition 0“ growth.

Table 3. Approximate pH values per nitting growth (adapted from FDA, Food) Microorganism Minimum Optimum Maximum Bacillus cereus 2.9 6.0—7.0 .8 idium botulinum m.6 ichia coli —.4 .0—7.0 O idium perfringens 5.5—5.8 Salmonella spp. m.2 .0—7.5 Staphylococcus aureus m.0 C7\\1\]O\ .0—7.0 HKOOOKOOOOO References United States Fharmacopoeia (US?) chapter <lll2> Application or waoer activity determination to non— sterile pharmaceuti cal :s.

Food and Drug Administration (EDA) sad %ug %ook: Foodborne pathogeni c microorganisms and natural toxins handbook. Factor a "ecting the growth 0 : rganisms in foods.

Taormina 9.d. "mplications o: salt and sodium reduction on microbial food safety. Cri tical Reviews in food science and nutrition 50:209—227, 2010 Food and Drug Administration (FDA) Food chapter 3.

Factors that influence microbial growth. December 31, 2001.

Kuwahara T, Kaneda S, Shimono K, Inoue Y. Growth 0: microorganisms in total parenteral nutrition solutions without lipid. "nternational Journal 0“ medical Sciences 3—47, 2010 De Seta F, Schmidt M, Vu %, fissman M, Larsen 3.

Antifangal mechanisms supporting boric acid therapy ll Candida vaginitis. Journal of crobial Chemotherapy —336, 2009 Test 1 A test 1 A—concentrate was used comprising: 210,7 g sodium chloride; 5,22 g ium chloride; 7,12 g magnesium chloride; 9,01 g m chloride; 35g glucose; 6,75 g citric acid, and purified water to a final volume 0: 1 liter.

This test 1 A—concenoraoe was then diluted with purified water to obtain ,es, 1 diluted concentrates with the following tions (test 1 A—concentratezwater): lz‘; lz7; lz4; 1:8; l:l6; 1:35. pH and water activity was measured for each test 1 diluted concentrate, see table 4 below.

Table 4. pH ard water activity measurements of test 1 diluted concentrates.

Dilution pH Water activity 1 1.4 0.86 2 2.0 0.94 4 2.3 0.97 8 2.6 0.98 The water activity was measured in the di "erent dilutions with AQUA Lab 4TEV instrument from Decagon Devices at 25°C according to the instruCtions from the manufacturer.

The test 1 diluted concentrat s w r th n t st d on yeast organism Candida albicans ATCC (American Type Culture Collection) 1023’ and on the organism ?seudomonas aeruginosa ATCC 15442. The tests were performed by covering the respec :ive organism with the di' "erent Lest 1 diluted concentrates, and the concentration of the sms (Colony Forming Units (CFU) per ml) were measured over time. As may be seen from Fig. 6, the di"erent test 1 diluted concenorates e"iciently prevented growoh of or killed (the 1:1 and 1:2 concenorates) ,he organism Candida albicans.

As may be seen from Fig. 7, the di"erent test 1 d concentrat s w r abl to ”'iciently kill the organism monas aeruginosa.

Test 2 A test 2 A—concentrate was used comprising: 210,7 g sodium chloride; 5,22 g potassium chloride; 7,12 g magnesium chloride; 9,01 g calcium de; 6,31 g acetic acid; and purified water to final volume ll a 0; 1 liter.

The test 2 entrate was then diluted with ed water to obtain test 2 diluted concentrates with the following proportions (test 2 A—concentrate:eri:ied water): 1:1; 1:2; 1:4; 1:8; 1 :16; ’:35.

VV()2012/163737 pH and water activity was measured for each test 2 diluted concentrate, see table 5 below.

Table 5. pH ar d water activity measurements of test 2 diluted concentra tes.

Dilution pH Water activity :1 .84 :2 .93 :4 .97 :8 .98 :16 .99 :35 WWWNNN prHQGH 000000 .99 The test 2 diluted concentrat s w r Lh n a S a d on the same organisms as the test 1 diluted concen ,raoes above, by using the sar1e method.

As may be seen from Fig. 8, the di' "erent test 2 diluted concentrate S e 'iciently prevented grow oh 0: or killed (the 1:1, 1: 2, :4, 1:8 second type diluted concentrates) the organism Candida albicans.

As may be seen from Fig. 9, the test 2 diluted concentrat s w r abl Lo 'iciently kill the organism ?seudomonas aeruginosa. ?reservation The blood Lrea omen a apparatus 2 is configured to 2O preserve the blood ,rea ,meno unit 20 betwee 1 blood treatment sessions such Lhao i a may be used an ed number 0: times. This vation may also e the blood line 40 such that the disposable unit 50 may be ved. In addition to preserving the blood treatment VV()2012/163737 unit 20 and optionall y also the blood line 40, the fluid line 30 may also be ved.

For implementing the preservation the blood treatment apparatus 2 has a fluid branch line 39 that is conn ct d b tw n th upstream f'uid line 31 and a first preservation connector 391. The first preservation connector 391 may b op n d r sp ctiv ly closed, either manually or by receiv ing control s from the processor unit 60, and is connectable to ,he first connector device 71 o f the blood withdrawal 1ine 41 (Or alternatively to the second connector device 72 o: the b'ood return line 49) The exemplified b'ood treatment apparatus 2 may also have a discharge line 122 that is arranged in between the drain 12 and a second preservation connector 121. The second preservation connector 121 may also be opened tively closed, either manually or automatically, e.g. by receiving control signals from ,he processor unit 60, and is connectabl e to the second connector device 72 2O o: the blood return 'ine 42 (or alternatively to the first connector device 71 of the blood withdrawal line 41).

Fig. 2 With reference : 0 Fig. 2 the blood ent apparatus 2 is illus,ra,ed when it is arranged to preserve the blood treatment unit 20, the blood line 40 and/or the fluid 'ine 30. As may be seen, the blood access devices ’3‘, 1 41 are now disconnected from the 3O blood line 40. Instead, the first connector device 71 is connected to ,he firs L preservation connector 391 and the second :or devi ce 72 is ted to the second preservation connector 121. The upstream fluid line 31 12/163737 may then direct a flow 0" preservation f1uid into the blood line 40.

When the change from the blood access devices 131, 141 to the preservation connectors 391, 121 is performed, the blood withdrawa; line 41 and the blood return 'ine 42 may be clamped by ng means 411, 421.

When the blood ent apparatus 2 is arranged to preserve the f1u id 'ine 30, the upstream f1uid 1ine 31 may then direct a ow 0t preservation f1uid through the f1uid 'ine 30 in the same route as the ,reatment fluid norma1'y flows during a treatment session.

When bo,h the fluid line 30 and the blood treatment unit 20 and the blood line 40 is to be preserved, the am f1uid 1 ine 31 may direct a flow 0" preservation fluid through both the fluid line 30 and the blood line 40, or on b for th och r.

Fig. 3 With further reference to Fig. 3, when the blood 2O treatment apparatus 2 is arranged as in Fig. 2 it may preserve the blood treatment unit 20 by performing a number 0: steps.

The preservation presumes that a first soep 301 o: the method includes preparation (priming) of ,he blood ,reatmen, apparatus 2 and the following blood treatment session for a patient, which may be med according to known techniq Jes and which results in that the blood treatment unit 2 0 is used.

During the blood treatment session no fluid may 3O enter or exi, the fluid branch line 39, and A— concentrate(s) and 3—concentrate are continuously used for preparing ,he ,reatment flJid that is passed through the blood treaomen, unit 20.

W0 2012/163B7 The first and second connector devices 71, 72 are sealed, as disclosed above, at the end of the first step 301 such that 10 uid may ”low 'rom or to the blood source 1 3 and the targ t v ss 1 11, r sp ctiv 1y. The first and second blood access devices 131 and ‘4‘ are then dis connected from the blood line 40 and the first and second connector devices 71, 72 are connected to the preservation connectors 391, 121.

In a 39X: step 308 the blood treatment unit 20 is filled w it 1 preservation fluid. "n this step the processor anit 6O may control the dilution and mixing such tha t the concentration 0: the A—concentrate in the treatmen t fluid is increased in comparison with the concentrate level that is used for tqe ent fluid, while there is no supply of the 3—coqcentrate into the upstream fluid line 31. The vation ”laid is fed to the blood treatment unit 20 via the fljid branch line 39 into the connector devices 71, 72 and the preservation connectors 391, 121. The processor unit 60 may be 2O sible for controlling the conneCtor s 71, 72, the preservation connectors 391 121 , SJCh that the preservation fluid may be ”ed 'rom the upstream fluid line 31, through t 1e fluid branch line 39 to the blood withdrawal line 41.

The -i'ling 0" the blood treatment unit 20 may be stopped wqen the blood line 40 and the blood compartment 40 is filled with preservation fluid. The filling ion is completed by closing the connector devices 7;, 72 and/or the preservation connectors 391, 121. The 3O e "ect o Pil— f the ing is that both the blood treatment unit 20 and the b:_ood line 40 are filled with the preserva tion uid. When preservation fluid is fed into the blood line 40 any fluid y present in the blood line 40 is rinsed out and is ed the drai ‘2. O'I] to n course, it is possible to use a separate drain 0 r Fluid that is rinsed out, whicq may be desirable when the rinsed out fluid comprises blood or blood residues.

In a next step 309 the preservation fluid is ined in the blood treatment unit 20 until a next blood ,reatmen o session is prepared. This means that the conneCtor devices 71, 72 and/or the preservation conneCtors 391, 191 remain closed until the preparations for the next blood treatment SGSSiOU commence. Typically, when treating an average paoien o the preserva,ion fluid is maintained in the blood area ,ment unit 20 for 8 hours or longer, such as 16 — 22 flours or even up to 70 hours or more. The resul, ol this step is that harmful microorganism growth in the blood treatment unit 20 or in the blood line 40 is prevented.

In a next Step 3lO the preservation fluid is dispatched from ,he blood treatment unit 20 and the blood line 40. This is done as part 0: preparing the bl ood 2O ent apparatus 2 for a nex : blood treatment session and may be accomplished by opening the connector devices 71, 72 and the vation connectors 39‘, 191. ?urified water is ,hen "ed 'rom she source of purified water ll, in,o the fluid branch line 39, into the blood witqdrawal line 41, into the blood treatment unit 20, out of the blood return 'ine 42, through the rge line 122, and to the drain l2. The discharge line 122 may be in fluid communication with the downstream fluid line 32, but may also be ly connected to drain (nOt shown). When the preservation f'uid is dispatched a new treatment operation may start, i.e. t me method may be re—iterated by returning ,0 the first s ,ep 301.

VV()2012/163737 Fig. 4 The method described in connection with Fig. 3 is a general description 0: how the blood ent apparatus 2 may preserve the blood treatment unit 20. A number 0; additional steps for preservation may be performed, as rated with re:ference to th mor d tai:_ d m thod of Fig. 4. "n a first step 301 o: the detailed method, a blood treatment session is performed fOr a patient as described in connection with Fig. 3. As mentioned, this results in that the blood treatment unit 20 is used and in that both A—concentrate and 3—concentrate are continuously used :OI ing she ,rea ,ment fluid that is passed through the blood treatmen a unit 20.

In a next step 303 the blood treatment unit 20 is rinsed or f'ushed. This may be accomplished by conveying a rinsing -='ui'd from the am fluid line, into the fluid branch line 39, into the blood awal line 41, through the blood treatment unit 20, ouu of the blood 2O return line 49, through the discharge line 122, and to the drain l2. By virtue of the blood lines' connection to the blood treatment unit 20, the blood line 40 is also rinsed wqen the blood treatrient unit 20 is rinsed. The rinsing typically removes b:_ood residues from the blood ,reatmen, unit 20 and the b:_ood line 40. The rinsing fluid may be puri.fied water, but may also coriprise ,reatmen, fluid or a physiological saline solution.

In three next steps 308, 309, 310 the blood ,reatmen, uni, 20 and blood line 40 are filled with the 3O preserva,ion fluid, the preservation fluid is maintained therein and is therea:fter dispatched, just as described in connection with steps 308, 309, 310 of Fig. 3.

VV()2012/163737 In a next step 31‘ rinsing O“ the blood ent unit 20 and the blood line 40 is per:formed again, which may be done in a manner corresponding to step 303. The step 311 of rinsing typically removes any residues 0; preservation fluid, and may be an integral part of the step 310 of dispatching of the preservation fluid. The rinsing f'uid may initially be puri:fied water, but may at the end of the rinsing operation comprise ,reatment fluid or at leaSt a physiological saline solution.

When the preservation fluid is rinsed out a new treatment operation may Start, i.e. the method may be re— iterated by returning to ,he first s ,ep 301.

However, before returning to step 301 a step 0; checking the blood trea ,ment unit 20 for its capability to treat blood may be per:formed. This may be done by ming a led conductivi:y measurement where a conductivity pulse is d at ,he fluid inlet 93 O“ the blood treatment unit 20 and a step response is measured by means 0: e.g. a conduc civify cell (not shown) ed downstream the blood trea omen, unit 20. A80 called clearance, i.e. indication 0“ tqe current performance 0: the blood trea ,ment uni, 20, may thereafter be calculated by t 1e processor unit 60 based on the Step response. ,he clearance is insu 'icient a next step 313 o: ing the blood treatmen, Jniu 20 with a new similar one is performed, and thereafter ,he first step 301 o: ming a blood treatment session may be reentered. On the other hand, il ,he clearance is su 'icien,, step 301 is reentered but wi:hout replacing the blood ,reaoment unit 20.

It is possible to per.form the s ,ep 312 o: checking the capability 0: the blood treatmen: unit 20 during the blood treatment session, i.e. steps 301 and 312 may be performed in parallel instead 0: sequentially.

Alternatively, the step 312 o: checking the blood ent unit 20 for ios capabilioy for trea,ing the blood may be done direcoly afoer soep 301, before step 303 where the blood treatment unit 20 is rinsed. In either case, i: the lioy ol the blood treatment unit is insu 'icient then step 3’3 0" replacing the blood treatment unit 20 may be entered directly after step 301 is complete.

During the step 301 o per'orming the blood treatment session, or during any other subsequent step, an integrity test may be done for ensuring that the membrane 27 in the blood treatment unit 20 does not leak. l5 ,he integrity test should show that the ne 27 leaks, then the step 3’3 of replacing the blood treatment unit 20 should be entered. The ity test may be embodied as an integra' part 0 ,he step 312 o: checking the capabilioy ol ,he blood treaoment uni, 20.

To verify thao the blood line 40 is filled with a proper composition 0" preservation fluid or prOtein solvent, or that the blood line 40 is su 'iciently rinsed during the steps 0: rinsing, the apparatus 2 may comprise conductivity meter (not shown) that is arranged in the discharge line 122. The conductivity meter may measure a composition 0" a 'luid in the rge line 122 and send a corresponding signal to the processor unit 60. The sor unit 60 may also or alternatively control the composition ol the fluid that is fed into the fluid branch line 39, such that a proper fluid composition is fed into the blood line 40.

Fig. 5 The method bed in tion with Fig. 3 and 4 may comprise a number 0: additional steps for preservation, as illustrated with reference to the more detailed method 0: Fig. 5. "n a first step 301 o: the detailed method, a blood treatment session is performed for a patient as bed in connection with Fig. 3. As ned, this results in that the blood treatment unit 20 is used and in that both A—concentrate and 3—concentrate are continuously used for preparing ,he ,reaoment fluid that is passed through the blood treatment unit 20.

In a next step 303 the blood treatment unit 20 is rinsed or flushed as described in connection with Fig.4.

In a next step 304 the blood treatment unit 20 and the blood line 40 are filled with a protein solvent like the 3—concentrate described above. This step may be performed in a manner similar with step 308 0: Fig. 3, with the di"erence that the processor unit 60 controls the on and mixing such that the tration 0; the 3—concentrate in the protein solvent is increased in comparison with the concentrate level that is used for the treatment fluid, while there is no supply 0: the A— concentrate iflfiO the upstream fluid 'ine 31.

In a next step 305 the protein solvent is maintained in the blood ,reatment unit 20 for a predetermined period ol ,ime, tAB, such as 10—15 minLtes. The result 0: this step is that blood prOteins remaining in the blood treatment unit 20 and the blood line 40 are solved, which is accomplished by the protein solving characteristics I] the 3—concentrate (bicarbonate).

VV()2012/163737 In a next step 306 the protein solvent is dispatched or flushed out from the blood treatment unit 20. ching tqe n solvent may be done in a manner corresponding to the dispatching o: the preservation fluid in step 310 0: Fig. 3.

In a next step 307 rinsing o: the blood treatment unit 20 and the blood line 40 is per:forned again, which may be done in a manner corresponding to step 303. In this t, dispat ching a fluid (in ,qe form blood or any other so'ution) from the blood treatment unit 20 and the blood line 40 may in some ments result in rinsing or ushing. "n a corresponding manner rinsing or flushing may result in dispatching a fluid in the blood ,reatment uni, 20 and blood line 40. Thus, steps 306 and 307 may be inuegraued into one step. The rinsing typically removes the protein solvent together with any therein solved prOte ins.

In three next steps 308, 309, 310 the blood treatmen, uni, 20 and blood line 40 are filled with the 9O preservauion 'luid, the preservation fluid is maintained therein and is thereafter dispatched, just as described in connection with steps 308, 309, 310 of Fig. 3.

In two next steps 311 and 312 the blood treatment uni t 20 and blood line 40 are rinsed again, and check 0; performance is done, just as described in connection with step 311 and step 312 o: Fig. 4.

Freserve fluid line In addition to as an alternative to preserving the blood ent unit 20 and optionally the blood line 40, the uid line 30 may be preserved in a similar manner.

This may e "'I ling the fluid 'i ne 30 with a preservation fluid 'ike the one used for the blood 12/163737 2012/059520 treatment unit 20, and maintaining the preservauion fluid in ,ne fluid line 30 for e.g. the same period 0: time as maintaining the preservation fluid in the blood treatment unit 20.

Typically, the :— uid line 30 is then filled with preservation fluid be':OYe, after or simultaneously to the blood treatment unit 90 is filled with preservation S'uid. The preservation fluid may be discarded from the f'uid line 30 before a next treatment operation by rinsing it with new ,reatmen, fluid. ving the fluid line 30 may be done independently o f the preserving o: the blood treatment unit 20, i.e. the blood treatment apparatus 2 may be configured to: i) perform a blood treatment session and thereby use the fluid line 30, ii) fill the fluid line 30 with a preservation flnid comprising a leaSt one treatmen, fluid concenurate of a type ,hat is used to pr par uh tr atm n, fluid, iii) maintain tne preservauion 'luid in ,he fluid line 30 until a next 2O blood treatment session is prepared, iv) dispatch the preservauion fluid F YOT‘l ,he fluid line 30 in preparation Off a neXt blood treatment SGS sion, and v) perform a next blood treatment session and y use the f'uid i ine 30 again.

Steps of ,he vation method may be per:formed by the processor anit 6O that controls various parts of the blood treatment appara:us 2. For this purpose the processor unit 60 typically includes one or more processing devices such that a cen :ral processing unit 61 which may execute software instruc :ions, i.e. computer program code that carry out releva nt steps and ions bed above . For this purpose the blood treatment apparatus 2 may include a computer—readable memory 62 VV()2012/163737 that stores the so:ftware instructions. These may :OI development convenience be written in a high—level programming language such as Java, C, and/or C++ but also in other programming languages, such as, but not limited to, interpreted languages.

The steps 0: rinsing 303, 307, 311, filling 304, 308 and dispatching 306, 3 l0 may be initiated by commands implemented by one or riore software instructions stored OD the computer—readab:_e memory 62. Also, relevant contro' 'ed means fOr performing the method are typically ' 'ed by the processor unit 60. From this _:O' lows, ,ha, the blood treatment unit is speci:fically configured to perform the described operations.

From a hardware perspective it may be said that the blood treatment unit comprises e.g. a pump capable o; filling the blood treatment unit with the preservation uid, and e devices, for example in form 0' clamps, connector devices or valves, that maintain the vation fluid in the blood treatmen 0 unit until a next blood treatment session is prepared. The pump may then dispa':ch the preservation fluid from the blood ,reatment Jniu in preparation 0“ a next blood treatment session, and the apparatus may therea oer perform a next blood e it session and thereby re Jse the blood ent anit.

Of coarse, the principles described herein tor preserving a blood treatment unit may be employed in conneCtion with other tuses as well, for example by tuses to which a blood treatment uni: may be connecued, 'iiled with " _ uid and subsequen:ly emptied 'rom 'luid. Moreover, i”: the connector s 71—74 are closed after ,he blood treatment unit 90 is filled with preserva,ion fluid, then the disposable unit 50 may be VV()2012/163737 removed jrom ,he apparatus 2 and stored at some other suitab; e location until it shall be reused. In the meantime, the apparatus 2 may be used by another patient.

A; so, other techniques 0 1" "I ling the blood ent unit and maintaining a uid therein may be used, and some method steps described herein may be performed in a di "eren, order than the rated one or may be combined, sucq as a ching step and its “Ol'owi ng rinsing step. Thus, althoagh various lO embodiments o: the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subj ct matt r d fin d in the following claims.

Claims (13)

What we claim is:

1. A blood treatment tus adapted to preserve a blood ent unit between blood treatment sessions, the blood treatment apparatus comprising the blood treatment unit, a blood line configured to pass blood through the blood treatment unit and deliver treated blood to a target vessel, and a fluid line configured to pass ent fluid through the blood treatment unit and deliver used/spent treatment fluid to a drain, wherein that the blood treatment apparatus is configured to: perform a blood treatment session and thereby use the blood treatment unit, fill the blood treatment unit with a preservation fluid comprising at least one treatment fluid concentrate of a type that is used to prepare the treatment fluid, and having a pH value less than 4.5, maintain the preservation fluid in the blood treatment unit until a next blood treatment session is prepared, dispatch the preservation fluid from the blood treatment unit in preparation of a next blood treatment session, and perform a next blood ent session and y extend the use of the blood treatment unit.

2. A blood ent apparatus according to claim 1, configured to fill the blood line with the preservation fluid, maintain the vation fluid in the blood line until the next blood treatment session is prepared, and dispatch the preservation fluid from the blood line in preparation of the next blood treatment session.

3. A blood treatment apparatus according to claim 1 or 2, configured to fill the fluid line with the preservation fluid, maintain the preservation fluid in the fluid line until the next blood ent n is prepared, and dispatch the preservation fluid from the fluid line in preparation of the next blood ent session.

4. A blood ent apparatus according to any one of claims 1 - 3, wherein the preservation fluid comprises an electrolyte solution.

5. A blood treatment apparatus according to claim 4, wherein the preservation fluid comprises an electrolyte solution having a water activity of less than 0.97.

6. A blood treatment apparatus according to any one of claims 1 - 5, wherein the preservation fluid comprises at least one of hydrochloric acid, citric acid, acetic acid, N-acetylcystein, ascorbic acid, α-ketoglutarate, gluconic acid, or combinations f.

7. A blood treatment apparatus according to any one of claims 1 - 6, ured to maintain the preservation fluid in the blood ent unit for at least 8 hours until the next blood treatment session is prepared.

8. A blood treatment apparatus according to any one of claims 1 - 7, wherein the blood treatment unit and the blood line are arranged as a common, disposable unit.

9. A blood treatment apparatus according to any one of claims 1 - 8, configured to, prior filling the blood treatment unit with the preservation fluid, flush a rinsing fluid through the blood treatment unit.

10. A blood ent apparatus according to any one of claims 1 - 9, comprising a processing unit and processing instructions which when executed on the processing unit cause the blood treatment apparatus to fill the blood treatment unit with the preservation fluid and maintain the preservation fluid in the blood treatment unit until a next blood treatment session.

11. A method for a blood treatment apparatus adapted to ve a blood treatment unit between blood treatment sessions, the blood treatment apparatus comprising the blood treatment unit, a blood line ured to pass blood through the blood treatment unit and deliver treated blood to a target vessel, and a fluid line configured to pass treatment fluid through the blood treatment unit and deliver used/spent ent fluid to a drain, the method comprising: filling the blood treatment unit with a preservation fluid comprising at least one treatment fluid concentrate of a type that is used to prepare the treatment fluid, and having a pH value less than 4.5, once a blood treatment sessions is completed, maintaining the preservation fluid in the blood treatment unit until a next blood treatment n is prepared, and dispatching the preservation fluid from the blood treatment unit in ation of a next blood treatment session.

12. A blood treatment apparatus substantially as herein described or exemplified, with nce to the drawings.

13. A method according to claim 11, substantially as herein described or exemplified.