Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using fluent heat transfer medium other than air
Reexamination Certificate
2002-04-15
2004-11-16
Jastrzab, Krisanne (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using fluent heat transfer medium other than air
C210S143000, C422S001000, C422S041000, C422S307000, C422S308000
Reexamination Certificate
active
06818179
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method and apparatus for producing a sterile medical solution. More specifically, the present invention relates to a method and apparatus for producing a sterile medical solution comprising a heat sensitive component, such as glucose.
BACKGROUND OF THE INVENTION
Medical solutions intended for mammals, specifically for use in humans, are required to be sterile before being infused or applied to the mammal.
One available method for sterilizing a solution is to heat the solution to a sterilizing temperature and to hold the solution at the sterilizing temperature during a sterilizing time period. To obtain a sterile medical solution intended for infusion, the solution is normally heated in an autoclave to 121° C. for 20 minutes to thereby produce said sterile medical solution. After the sterilizing time has elapsed, the solution should be cooled to a physiologically acceptable temperature before infusion.
Known methods and apparatus for sterilizing a solution are disclosed, for example, in British Patent Applications Nos. 1,450,030; 1,504,334; and 2,034,584, and in U.S. Pat. No. 5,603,894. These prior art publications describe the preparation of a medical solution starting from tap water and producing pure water by means of a reverse osmosis device, mixing a concentrate with the pure water to produce a non-sterile medical solution, passing the non-sterile medical solution through an on-line autoclave and delivering the sterile medical solution to a recipient, such as a storage bag or a patient.
In the prior art, the complete medical solution is first prepared in a non-sterile condition and then passes through an autoclave. If the medical solution comprises heat sensitive components, these must not be exposed to too high a temperature. Normally, the temperature is increased up to the sterilizing temperature and the medical solution is maintained at the sterilizing temperature for a sterilizing time period. If the temperature is 121° C., which is normal in an autoclave, the sterilizing time is 20 minutes to obtain a sterilizing dose, F
0
, of 20 minutes, as discussed below. Since the sterilizing effect is approximately exponential, an increase of the temperature by 10° C. means a lowering of the sterilizing time by ten times. If a sterilizing temperature of 131° C. is used, the sterilizing time should be 2 minutes, and if a sterilizing temperature of 141° C. is used, the sterilizing time should be 12 seconds, in order to obtain a sterilizing effect, F
0
, of 20 minutes.
If the medical solution comprises a heat sensitive component, like glucose, that component will deteriorate during the heat treatment. An example of a medical solution containing a heat sensitive component is a dialysis fluid for peritoneal dialysis (PD). The decomposition or heat deterioration starts at a much lower temperature than the sterilizing temperature and is also present at room temperature. In order to safeguard the heat sensitive material, very short heating and cooling periods are desired so that the time/temperature profile becomes more or less rectangular. This is of greater importance if high sterilizing temperatures and short sterilization times are used.
It is known to produce sterile medical solutions by including the medical solution in a bag and placing the bag inclusive of the medical solution, in an autoclave for heating and sterilization.
A variant of this method is described in international Application No. WO 93/09820, in which the medical solution is divided into two portions, one comprising glucose at high concentration and the other comprising the rest of the solution. The double bag is heat sterilized in an autoclave. Shortly before use, the contents of the two chambers are mixed to produce the sterile medical solution. In this way, the heat sensitive component, glucose, can be autoclaved under more appropriate conditions, such as at a low pH of approximately 3.2, and at a high concentration of approximately 50%, i.e. 500 grams of glucose per liter of glucose solution.
A variant of the same methods is described in International Application No. WO 97/05852 disclosing a three-chamber-bag, in which two of the chambers comprise glucose solution and the third chamber comprises the rest of the solution. The glucose chambers may also include ionic components, such as calcium, magnesium and sodium.
A further variant is described in International Application No. WO 99/27885.
In the aforementioned concepts, the glucose portion is sterilized separately from the remaining portion of the solution. However, in order to fully sterilise the large compartment, the small glucose compartment may be over sterilized, resulting in deterioration of the heat sensitive component. A remedy for that problem is described in Swedish patent application No. 9803627-0, filed at the Swedish Patent Office on Oct. 23, 1998.
The problem of deterioration of a substance during autoclaving is also recognised in other fields of use, such as the production of sterile milk products. In order to obtain rapid heating and cooling of the product, it is not sufficient to use heat transfer by means of a heat transferring surface, like a heat exchanger. Instead, the product is mixed with steam at a predetermined temperature and pressure to condense the steam in the milk product. The milk product is sterilized by retention in a holding zone for a certain time period and at a temperature of from about 120 to 150° C., and is then transferred to a flash cooling step, in which water is evaporated in an evaporation chamber to rapidly cool the product. Such a process is described in, for example, International Application No. WO 98/07328.
DISCLOSURE OF INVENTION
One object of the present invention is to provide a method and apparatus for producing a sterile medical solution having a gentle treatment of the heat sensitive component.
Another object of the present invention is to provide a method and apparatus in which inexpensive heaters and heat exchangers can be used.
A third object of the present invention is to provide a method and apparatus for sterilizing a medical solution in which the time/temperature profile for heating the heat sensitive component is essentially rectangular.
SUMMARY OF THE INVENTION
In accordance with the present invention, these and other objects have now been realized by the invention of a method for sterilizing a heat sensitive fluid comprising providing a first heat sensitive fluid component, providing a second fluid component, heating the second fluid component to a first temperature, the first temperature being greater than a predetermined sterilizing temperature, mixing the first heat sensitive fluid component with the heated second fluid component, whereby the first heat sensitive fluid component is heated and the heated second fluid component is cooled, and a mixed fluid is provided at a second temperature, the second temperature being at least the predetermined sterilizing temperature, and maintaining the mixed fluid at the second temperature for a predetermined sterilizing period, whereby a predetermined sterilizing dose is obtained for delivery to a recipient. Preferably, the method includes controlling the heating of the second fluid component to the first temperature to ensure that the mixed fluid reaches the second temperature.
In accordance with one embodiment of the method of the present invention, the method includes cooling the mixed fluid.
In accordance with another embodiment of the method of the present invention, the first heat sensitive fluid component comprises glucose or a glucose polymer.
In accordance with another embodiment of the method of the present invention, the second fluid component comprises water. Preferably, the second fluid component includes electrolytes, such as sodium chloride, calcium chloride, magnesium chloride, potassium chloride, sodium bicarbonate, or sodium lactate.
In accordance with another embodiment of the method of the present invention, the method includes preheating the first heat sensitive fluid component.
Dunkley Michael John
Edgson Raymond Anthony
Hammond Richard J.
Wilkinson Eric
Gambro Lundia AB
Jastrzab Krisanne
Lerner David Littenberg Krumholz & Mentlik LLP
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