Abstract:
The invention concerns a hygienic agent for use in hemodialysis. This hygienic agent based on peracetic acid has an aqueous solution containing 6 to 8 weight % hydrogen peroxide, 0.1 to 1 weight % peracetic acid and 2 to 10 weight % acetic acid. Application to the disinfection, sterilization of dialysis generators, dialyzers, hemofilters and hemodialyzers and circuits of water treatment for hemodialysis.

Description:
This application is a continuation of parent application Ser. No. 08/111,966 filed Aug. 26, 1993, now abandoned, which is a continuation of Ser. No. 07/653,972 filed Feb. 11, 1991, now abandoned, which is a continuation of Ser. No. 07/438,293 filed Nov. 20, 1989, now abandoned. 
    
    
     BACKGROUND OF INVENTION 
     (1) Field of the Invention 
     The present invention concerns a hygienic agent for use in hemodialysis. 
     (2) Description of Prior Art 
     The principle of the extra corporeal dialysis is based on the contact of the blood to be purified with a dialysate through a semi-permeable membrane. In order to obtain efficient exchanges, the blood and dialysate must be permanently renewed, since the speed of diffusion, or of dialysis, depends on the difference of concentrations between the blood and the dialysate. This is obtained by creating an extra-corporeal circulation. 
     Any dialysis chain comprises a generator, a dialyzer, a dialysate and a water circuit. 
     The generators enable to obtain the dialysate, the circulation of the blood and of the dialysate, and the controls of the parameters of dialysis. 
     The artificial kidney or dialyzer permits the elimination of water and of the waste produced by the body by contacting the blood with a liquid which is the dialysate or a dialysis bath. The blood and the dialysate are separated from one and other only by means of a thin artificial organic membrane, of cellophane, cuprophane, polysulfone, polypropylene, polyamide, polyacetate, copolymer of acrylonitrile . . . This membrane can be prepared in the form of plates, as compartments which are piled over one and other, or in the form of coils, as a single compartment which is spirally wounded about an axis or finally as capillaries consisting of an assembly of very fine hollow fibres. 
     Thus, there are three types of dialysis which are often delivered sterile for single use. 
     In the coiled kidneys, of the type where two sheets of dialysing membrane are spirally wound in a parallel fashion about an axis, the blood circulates inside the envelope defined by the two sheets of the membrane and the dialysate on the outside. The coiled kidney is actually the less utilized. 
     The plate kidneys are all disposed according to the same diagram corresponding to an assembly of 15 to 20 sheets of membrane mounted as an arrangement of plates in a sandwich type fashion, so as to provide inserted blood compartments and dialysate compartments. The blood circulates from top to bottom between the sheets while the dialysate circulates in opposite direction. 
     The hollow fibre kidney contains very little blood; it offers a very weak resistance to the flow of blood. Instead of sheets of membrane in roller or plate arrangement, the dialysing surface is formed in the case of thousands of tiny hollow fibres. The blood passes from top to bottom and the dialysate passes around in the other direction. 
     The dialysate is a mixture of water and electrolytes, and the concentration of the electrolytes in the dialysate is provided so that the composition of the electrolytes in the blood is normal at the end of the operation. 
     For hemodialysis uses, water should be very pure and chains of hemodialysis are generally provided with a water treatment consisting of softeners, demineralizers, osmosers, filters and a container for storing water. After the container for storing water there is found a utilisation circuit which feeds the dialysis generators. 
     Since the appearance of the extra-corporeal blood purifying techniques, there were always problems associated with the disinfection and tartar removal from the material used. 
     The dialyzers are often materials considered to be for single use. However, certain establishments reuse them under the responsability of medical doctors. Now the chain of dialysis can very easily be contaminated and this is the reason why it must absolutely be disinfected on a regular basis. 
     Clinical reports indicate that important microbial proliferations in hemodialysis apparatuses can have serious effects on patients who are dialysed. More particularly, such phenomenons as bacteremia, hepatitis, fever, shivers, hypotension and shock have been observed. 
     Hot sterilization which would represent the ideal hygienic step is actually not feasible because of the numerous elements of the chain of dialysis which are unstable with respect to heat. 
     The addition of impervious filters placed immediately before the dialyzer is not completely satisfactory, since virus, mycoplasma and certain bacteria can pass through these filters. 
     In addition these physical methods of disinfection require a regular chemical disinfection of the other elements of the chain of dialysis. 
     In view of all the requirements that an appropriate disinfecting agent should meet, namely a large spectrum of activity for an active time which is as short as possible, cleaning and material preserving properties as well as a capacity to be easily rinsed under controlled conditions, only certain compounds can be considered. 
     The products used for disinfection are generally formaldehyde or sodium hypochlorite. 
     The water circuit can be regularly disinfected with formaldehyde or with sodium hypochlorite. 
     This operation is generally carried out once every six months since it is time consuming and requires that the operation of hemodialysis be stopped. 
     Sodium hypochlorite is used under more or less substantial dilutions depending on use, of the order of 50%, for the disinfection of generators. 
     Formaldehyde is also used under more or less substantial dilutions depending on the intended use. 
     These disinfecting products require multiple manipulations, such as preparations and dilutions . . . and involved risks. Thus, formaldehyde can produce an allergy which is well classified as a professional disease. Sodium hypochlorite brings in chlorine in a highly pure medium, which represents an inconvenience. 
     Independently in the disinfection, various acids are used to remove tartar, such as acetic, lactic, citric acids . . . 
     Peracetic acid, whose disinfecting properties are known, has been proposed at a concentration of a few percentages, from the order of 3.5-4%, for the disinfection of generators of dialysis. Under this concentration, this type of disinfecting agent has various disadvantages, including the fact of being a product which presents risks for the treating staff because of its irritating effect on skin and mucous membranes, as well as its corrosive activity on the dialysis material. 
     Therefore, a search has been made for a new concept of hygienic agent for use in hemodialysis which would meet the following conditions: nontoxicity and biocompatibility in trace amounts, combined disinfection and tartar removal, active time lower than 30 minutes, complete disinfecting effect, easily rinsable and detectable, biodegradable, stable and ready to be used. 
     SUMMARY OF INVENTION 
     A hygienic agent for use in hemodialysis fulfilling all the above conditions has been found. In addition, this new formulation based on peracetic acid increases the properties of one of its active principles. It consists of an aqueous solution containing 6 to 8 weight % hydrogen peroxide, 0.1 to to 1 weight % peracetic acid and 2 to 10 weight % acetic acid. 
     An aqueous solution containing 6 to 8% hydrogen peroxide, 0.3 to 0.4% peracetic acid and 3.5 to 4.5% acetic acid is very advantageous, and in particular an aqueous solution containing 7% hydrogen peroxide, 0.35% peracetic acid and 3.5 to 4% acetic acid. 
     These aqueous solutions constituting a hygienic agent for use in hemodialysis are in the form of colorless, non-inflammable liquid which can be mixed with water in all proportions, does not foam, can easily be rinsed, can be kept at room temperature in its original wrapping, and has excellent stability for at least one year. 
     This hygienic agent for use in hemodialysis constitutes a harmless product under normal conditions of use, while permitting the disinfection and tartar removal from the hemodialysis material in a single operation, under the best conditions of hygiene and safety for the staff and the patients, in which no irritations nor allergies have been observed. 
     With a complete spectrum disinfecting formula, the new hygienic agent for use in hemodialysis has been shown to be an efficient bactericidal, fungicidal, sporicidal and virucidal agent. Because it is oxidizing and acidic, the hygienic agent for use in hemodialysis frees a particularly active oxygen. It reacts with the proteins of the membrane of the microorganisms and penetrates inside cells to destroy them. Its acidic character provides tartar removal properties. 
     The bactericidal activity of the hygienic agent for use in hemodialysis has been tested on hemodialysis material sequentially contaminated with the following germs: Pseudomonas aerugionsa and Microbacterium smegmatis. Depending on the dilutions used for the apparatuses, which consist of 3 to 10% aqueous solution containing 7% H 2  O 2 , 0.35% peracetic acid and 3.5% acetic acid, 10 6  to 10 10  bacteries/ml could be destroyed in 10 to 30 minutes. 
     The hygienic agent for use in hemodialysis was also tested in vitro according to the requirements of the AFNOR norms, and it is important to note that the disinfecting properties were maintained in the presence of organic materials (dialysate, blood, etc . . . ). 
     The fungicidal activity of the hygienic agent has been confirmed in vitro against yeasts and molds. 
     The sporicidic activity was tested in vitro and also on hemodialysis material contaminated with spores of Bacillus cereus. Depending on the apparatuses used, 3 to 10% of a solution of a hygienic agent containing 0.35% peracetic acid destroy 10 4  to 10 6  spores of Bacillus cereus in a period of 10 to 30 minutes. 
     The virucidal activity has been confirmed, such as on the AIDS virus. A contact of 30 minutes with a solution containing 0.35% peracetic acid at a concentration of 1.5% is sufficient to inactivate the HIV (Human Immunodeficiency Virus). 
     The hygienic agent according to the invention is not toxic for patients and staff. On the contrary, it has been observed that allergic and anaphylactic shocks have disappeared as well as a decrease of pyrogenic reactions, often found during dialysis. 
     The lethal dose LD 50 on rat was 1.540 mg/kg for peracetic acid, which corresponds to about 440 g/kg of a solution of hygienic agent containing 0.35% peracetic acid. The toxicity by acute inhalation: LC 50 is about 150 g/m 3  of the solution, the sub-acute toxicity corresponds to 20 g/m 3  and the tolerable threshold for the nose and the eyes is 0.3 g/m 3 . The cutaneous toxicity, with respect to reversible lesions of the occular mucous membrane corresponds to the pure solution, the irritation threshold of the eye corresponds to a solution diluted one tenth. The irritating power on the skin is light with the pure solution and zero with a solution diluted to one tenth. 
     The hygienic agent for use in hemodialysis is biocompatible, and can be metabolized when present in traces. After 10,000 dialyses, no intolerance, irritation or allergy were observed among patients and treating staff. Tests made on blood of healthy donors have established that quantities lower than 0.2% solution of hygienic agent containing 0.35% peracetic acid are harmless and produce no modification of the erythrocytes (counts unchanged), hemoglobin, blood platelets, leukocytes and plasmic proteins. Thus, a concentration which is 150 times higher than the threshold of detection of the tests for rinsing control produced no ill effect on in vitro human blood. 
     The hygienic agent according to the invention finds applications in disinfection and tartar removal in all the stages of the cycle of dialysis. 
     It enables to disinfect and remove tartar from dialysis generators within less than one hour, including rinsing time. It can be used for a rapid disinfection between two dialysis treatments. Tartar removal from generators is realised simultaneously as their disinfection and there is no need to use another acid. Disinfection is carried out while the chemical disinfection cycle of the generators take place, and the periods of contact and rinsing are adjusted on the apparatuses, generally between 20 to 30 minutes of contact and 30 minutes of rinsing with osmotic water. For a normal chemical disinfection cycle it is recommended to use a dilution between 1/10th and 1/35th, preferably 1/30th. 
     The invention can also be used to make sure that generators awaiting utilisation in a dialysis cycle are kept sterile. 
     The hygienic agent according to the invention enables to disinfect water treatment circuits which are used for hemodialysis, in particular in the recirculation loop. This disinfecting agent can quite easily be used with short contact times, about 30 minutes, which enables to provide weekly or daily treatments according to needs. The agent can be used to disinfect channels, filters, and loops with a decrease of 10 6  to 10 7  germs/ml. Disinfection is followed by rinsing with osmotic water, during a short period of time of the order of 30 minutes to 2 hours depending on the circuits used. 
     The new peracetic acid-hydrogen peroxideacetic acid composition can be used as the single cleaning and disinfection agent in the sterilisation of dialyzers, hemofilters, hemodialyzers. The possibility of reusing dialyzers treated with such composition constitutes a simple method which is very efficient, and well accepted by the treating staff. The composition ensures an average number of 8 to 12 reutilisation times for each dialyzer, under high bacteriological security conditions, thus permitting to consider the possibility of significantly reducing the total cost of the therapeutic treatment while enabling to use &#34;highly permeable&#34; membranes (better quality but very expensive). 
     The germicidal action of the disinfection agent extends for at least 15 days thus permitting an easy preservation of the modules of dialysis from one treatment to the other. 
     Under conditions of automated reutilisation, the optimal dilution to strip the dialyzers as well as possible seem to be between 1/10th and 2/7th. In this case, the average reutilisation number is 8 to 9 with a single automated reconditionning of the modules of dialysis, with an apparatus for reutilisation ensuring a rinsing and cleaning of the high flow blood compartment in the direction of the fibres as well as by retrofiltration. The reutilisation of dialyzers with the recommended dilutions is never associated with a degradation of the filters or of the material to be reutilised. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a schematic illustration of a chain dialysis used for carrying disinfection according to the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Non-limiting examples of application of the hygienic agent according to the invention designated by Dialox® are given hereinafter. 
     EXAMPLE 1 
     Disinfection of generators of dialysis 
     The chain of dialysis in which the disinfection tests have been carried out, is represented in the annexed figure.. This chain comprises generator (1) in which the preparation of the dialysis bath is carried out, from the dialysate sampled in the reservoir (2) and fed toward the generator by means of the circuit (3). Water circulates in the circuit (4) until reaching the generator, and the dilution of the dialysis bath is carried out by means of the measuring pump (5). The dialysis bath leaves the generator via circuit (6) to be introduced in the dialyzer (7), after exchange with the blood of the sick person according to circuit (8a), (8b), and the dialysis bath is sent to a drainage via circuit (9). 
     For this series of tests the generator is placed in position of disinfection, and the tests were carried out with various strains of germs which were purposely introduced in the circuit (3). The generator takes sample on the circuit (3) and automatically dilutes the hygienic agent Dialox® by means of the measuring pump (5). 
     These tests were carried out in various types of generators with different dilutions of Dialox® corresponding to a solution containing 0.35% peracetic acid, 7% H 2  O 2  and 3.5% acetic acid and contact times between 10 to 30 minutes. 
     The samples were respectively taken at points (A) on the water circuit (4) before entering the generator, (B) on the circuit (6) of the dialysis bath before entering the dialyzer, (C) on the circuit of the dialysis bath (9) close to the outlet of the dialyzer, and at (D) before rejecting it to be drained. 
     The introduction of the germs is controlled, as well as the samples carried with a series of probes, at the osmotic water inlet (A), inlet of kidney (B), outlet of kidney (C) and drainage outlet (D). In each case, the initial and final count and the decrease of the number of germs are given. 
     EXAMPLE 1a 
     Generator of the type Frenesius®. 
     
                       TABLE Ia______________________________________Site of  Initial count/                 Final count/                           Decreasesampling ml           50 ml     log 10______________________________________Strain                Pseudomonas aeruginosaDilution              DIALOX ® 1/35thTime (T.) of contact  20 min. (mn)A        0            0          0.00B        8.00E + 08   0         10.60C        8.00E + 08   0         10.60D        8.00E + 08   0         10.60Strain                Spores of Bacillus cereusDilution              DIALOX ® 1/35thT. of contact         20 mnA        0            0         0.00B        3.00E + 06   0         8.18C        3.00E + 06   0         8.18D        6.00E + 06   0         8.48______________________________________ 
    
     EXAMPLE 1b 
     Generator of the type Monitral 
     
                       TABLE IB______________________________________Site of  Initial count/                 Final count/                           Decreasesampling ml           50 ml     log 10______________________________________Strain                Pseudomonas aeruginosaDilution              DIALOX`® 1/35thT. of contact         30 mnA        0            0         0.00B        1.00E + 06   0         7.70C        1.00E + 06   0         7.70D        1.00E + 07   0         8.70Strain                Mycobacterium smegmatisDilution              DIALOX ® 1/35thT. of contact         30 mnA        0            0         0.00B        1.00E + 06   0         7.70C        1.00E + 06   0         7.70D        1.00E + 06   0         8.70Strain                Spores of Bacillus cereusDilution              DIALOX ® 1/35thT. of contact         30 mnA        0            0         0.00B        4.00E + 06   0         8.30C        4.00E + 06   0         8.30D        7.00E + 06   0         8.54______________________________________ 
    
     EXAMPLE 1c 
     Generator of the type AK 10 
     
                       TABLE IC______________________________________Strain        Pseudomonas aeruginosaDilution      DIALOX ® 1/35thT. of contact 20 mnSite of   Initial count/                  Final count/                            Decreasesampling  ml           50 ml     log 10______________________________________A         0            0         0.00B         6.00E+08     0         10.48C         6.00E+08     0         10.48D         6.00E+08     0         10.48______________________________________Strain        Mycobacterium smegmatisDilution      DIALOX ® 1/35thT. of contact 10 mnSite of   Initial count/                  Final count/                            Decreasesampling  ml           50 ml     log 10______________________________________A         0            0         0.00B         1.00E+07     0         8.70C         1.00E+07     0         8.70D         9.00E+07     0         9.65______________________________________Strain        Spores of Bacillus cereusDilution      DIALOX ® 1/35thT. of contact 10 mnSite of   Initial count/                  Final count/                            Decreasesampling  ml           50 ml     log 10______________________________________A         0            0         0.00B         1.00E+06     900       4.74C         1.00E+06     700       4.85D         2.00E+06     1000      5.00______________________________________Strain        Spores of Bacillus cereusDilution      DIALOX ® 1/35thT. of contact 10 mnSite of   Initial count/                  Final count/                            Decreasesampling  ml           50 ml     log 10______________________________________A         0            0         0.00B         8.00E+06     5000      4.90C         8.00E+06     4000      5.00D         1.00E+07     3000      5.22______________________________________Strain        Spores of Bacillus cereusDilution      DIALOX ® 1/35thT. of contact 10 mnSite of   Initial count/                  Final count/                            Decreasesampling  ml           50 ml     log 10______________________________________A         0            0         0.00B         4.00E+06     0         8.30C         4.00E+06     0         8.30D         4.00E+06     0         8.30______________________________________ 
    
     EXAMPLE 1d 
     Comparative test for the disinfection of a generator of the type AK 10 (GAMBRO)® 
     
                       TABLE Id______________________________________Strain        Spores of Bacillus cereusDilution      4% formaldehydeT. of contact 12 hoursSite of   Initial count/                  Final count/                            Decreasesampling  ml           50 ml     log 10______________________________________A         0            0         0.00B         1.00E+06     300       5.22C         1.00E+06     500       5.00D         1.00E+06     150       5.52______________________________________ 
    
     EXAMPLE 2 
     Ex vivo study of the germicidal power of an aqueous solution containing 3.5% peracetic acid, 7% H 2  O 2  and 3.5% acetic acid (Dialox®). 
     The germicidal power of the Dialox® has been studied in vitro on used hemodiafilters (HF 80, polysulfone membrane, Fresenius®) which were sequentially contaminated by 3 types of germs (Pseudomonas aeruginosa, Mycobacterium smegmatis and Bacillus cereus in sporulated form). 
     For each type of germ 5 hemodiafilters were used: the first was used as indicator of contamination and the four others were used as indicator of the efficiency of the disinfecting product. These hemodiafilters were submitted to the normal procedure for reutilisation with disinfection by passing through Renatron®, which is an apparatus for reutilisation ensuring a highly efficient rinsing and cleaning of the blood compartment in the direction of the fibres as well as by retrofiltration. 
     These times of contact of the membranes with the disinfecting solution were respectively 5, 10, 20 and 30 minutes, and the count of the colonies of germs collected on the membranes were carried out at the 24th, 48th, 72nd and 96th hour of culture period. 
     The bactericidal power of Dialox® expressed as a logarithmic reduction of the number of germs by ml obtained for the three categories of germs tested as a function of time, is represented in the following table. 
     
                       TABLE II______________________________________                 CountTime    Count         after contact                           ReductionMinutes A T = 0       time      LOG 10______________________________________PSEUDOMONAS AEROGINOSA5       1.2 · 10.sup.7 g/ml                 0         7.0810      1.2 · 10.sup.7 g/ml                 0         7.0815      1.2 · 10.sup.7 g/ml                 0         7.0820      1.2 · 10.sup.7 g/ml                 0         7.08MYCOBACTERIUM SMEGMATIS5       5.1 · 10.sup.7 g/ml                 0         7.7110      5.1 · 10.sup.7 g/ml                 0         7.7115      5.1 · 10.sup.7 g/ml                 0         7.7120      5.1 · 10.sup.7 g/ml                 0         7.71BACILLUS CEREUS SPORULE5       4.0 · 10.sup.7 g/ml                 0         6.6010      4.0 · 10.sup.7 g/ml                 0         6.6015      4.0 · 10.sup.7 g/ml                 0         6.6020      4.0 · 10.sup.7 g/ml                 0         6.60______________________________________ 
    
     For a contaminating solution comprising 10 6  to 10 7  units forming colonies (U.F.C.)/ml, the reduction on the blood sector as well as on the dialysate sector is between 6 to 7 log after 5 minutes, of contact for a solution of Dialox® diluted 1/10th. The reduction is identical for germs which are sporulated or unsporulated. The bactericidal effect thus appears to be absolute for Dialox® diluted 1/10th after 5 minutes of contact. 
     EXAMPLE 3 
     In vivo study of the cleaning and disinfecting effect of Dialox® on the modules of dialysis. 
     This in vivo evaluation was carried out on ten patients in stable condition of chronic kidney insufficiency, for extra kidney assistance, by hemodialysis, hemofiltration or hemodiafiltration. 
     Three models of dialyzers were used: HF 80 (polysulfone membrane Fresenius®), Filtral 16 polyacrylonitrile AN69 HOSPAL®, FH 88 (polyamide membrane, GAMBRO®). 6 dialyzers have been used for each patient. 
     The reconditionning of the modules of dialysis was carried out automatically on a Renatron® as the treatment was terminated. 
     The cleaning agent was Dialox® at 0.35% peracetic acid. For cleaning filters, 2/7th, 1/7th, ,1/10th, 1/20th dilutions were used. The dilution used for maintaining the filters sterile from one treatment to the other was 1/10th. 
     Table II indicates the average number of reutilization of 60 modules with 10 patients (represented by their initials) under 2 dilutions of Dialox® at 0.35% peracetic acid, respectively 1/20th and 2/7th. 
     
                       TABLE III______________________________________Reaction of patient______________________________________Patient   BC        CJ     RY      FA   EKFilter    FH88      FH88   FH88    HF80 HF80______________________________________Dilutionof Dialox ®1/20th    7         8.2    5.3     4.3  9.52/7th     8.5       7.7    6.2     6.0  9.8X______________________________________Patient   EA        EF     TR      DV   FPFilter    FH80      HF80   HF80    F16  F16______________________________________Dilutionof Dialox ®1/20th    9.7       9.8    9.2     7.7  11.22/7th     10        10.2   9.8     7.8  10.3X______________________________________ X: number of reutilisation average/patient. 
    
     The average number of reutilisation was therefore of 8 (at most 4 to 11 times) with a good possibility of reproduction on the same patient whatever the dilution of Dialox® used. 
     In Table IV there is represented the average number of reutilisation of the modules of dialysis depending on their mode of utilisation in hemodialysis (HD), in hemofiltration (FH) or in hemodiafiltration (HDF) under 4 different dilutions of Dialox® at 0.35% peracetic acid, respectively 1/20th, 1/10th, 1/7th and 2/7th. 
     
                       TABLE IV______________________________________Influence of the method of dialysisDilutionof Dialox ®      HF           HDF    HD______________________________________1/20thX          6.2          9.5     9.4n          (18)         (30)   (12)1/10thX          7.5          9      10.5n           (3)          (5)   (2)1/7thX          7.1          10.0    9.1n          (18)         (30)   (12)2/7thX          7.3          9.2    10.0n           (3)          (5)   (2)______________________________________ n: total number of tests. X: average number of reutilisation/method. 
    
     The influence of the method of dialysis is clear when comparing the 2 most representative groups, namely those corresponding to 1/20th and 1/7th dilutions. These data establish that the modules used in hemofiltration have an average number of reutilisation significantly lower than those used in hemodialysis or in hemodiafiltration. 
     The influence of the type of dialyzer was studied for the dialysis modules FH 88, HF 80 and FILTRAL 16 at 4 different dilutions of Dialox® 0.35% peracetic acid, respectively 1/20th, 1/10th, 1/7th and 2/7th. 
     The average number of reutilisation (X) by dialyzer is given in table V. 
     
                       TABLE V______________________________________Influence of the type of dialyzerDilutionof Dialox ®      HF88         HF80   F16______________________________________1/20thX          5.2          7.1    6.3n          (30)         (50)   (20)1/10thX          5.3          7.6    7.1n           (3)          (5)    (2)1/7thX          5.7          7.7    6.2n           (30)        (50)    (20)2/7thX          5.3          7.8    7.0n          (3)           (5)   (2)______________________________________ n: total number of tests. X: average number of reutilization/dialyzer. 
    
     These data establish that there is a significant difference only between hemofilters FH88® and the group of hemodiafilters HF80® and FILTRAL 16®. 
     During this program of reutilisation of the module of dialysis no particular reaction was observed on the patients and the performances of the dialysis were not affected significantly by the reutilisation. 
     EXAMPLE 4 
     Disinfection of the water circuit. 
     In this type of disinfection, there was used a disinfecting agent containing 0.35% peracetic acid, Dialox®, at a dose of 5 liters for 100 liters of water injected in a buffer capacity. During disinfection, the circulation pumps of the circuit should operate to circulate the mixture of water and disinfecting agent. The circulation/disinfection time of contact is 30 minutes. Rinsing of the circuit is not carried out with osmotic water.