Sterilization special problems

Processing in Hquid sterilants results in wet products which require highly specialized packaging. Therefore, Hquid sterilization should only be considered if the sterilized article is to be used almost immediately. Liquid sterilants or their residues can be harmful to living tissues. Therefore it is always necessary to rinse articles with sterile water or saline solution foUowing treatment. Whereas Hquid sterilization is an extremely useful method for articles that caimot withstand the conditions of steam sterilization, the problems associated with its use limit its appHcation. 

The rules of steam sterilization are well described [2.15], including some guide-lines for the validation of the sterilization process. The special problems with the steam sterilization of closing systems for vial stoppers has been discussed above. Similar problems... 

Brewer, J.H. Schmitt, R.F. Special Problems in the Sterility Testing of Disposable Medical Devices, Annual General Meeting of the Parenteral Drug Association, New York, November, 2, 1966. 

The essential method to obtain sterile air, whether packed-bed or cartridge filters are used, is to reduce the humidity of the air after compression so that the filter material always remains dry. The unsterilized compressed air must never reach 100% relative humidity. Larger plants install instrumentation with alarms set at about 85% relative humidity. Careful selection of the cartridge design or the design of packed-bed filters will result in units that can operate in excess of three years without replacement of filter media. If a fiber material is used in a packed-bed type filter, the finer the fiber diameter the shallower the bed depth needs to be for efficient filtration. Other filter media are less common and tend to have special problems and/or shorter life. The bed depth of filters is only 10 to 18 inches for fibers of less than 10 microns. These filters run clean for 2 weeks or longer before being resterilized. 

For sterile products, there should be no reduction in the degree of validation of sterilizing equipment required. Validation of aseptic processes presents special problems when the batch size is small, since the number of units filled may be not adequate for a validation exercise. Riling and sealing, which is often done by hand, can compromise the maintenance of sterility. Greater attention should therefore be given to environmental monitoring. 

The advent of parenteral nutrition has opened new avenues for therapy and prevention of malnutrition in these children. However, the technique of parenteral nutrition in burns poses several special problems. Because of the nature of the burned wound, sepsis is a particular hazard. Placement of the catheter is difficult especially when the burns involve the upper trunk and the arms. Whirlpool debridement may compromise sterility at the site of the catheter entrance. On the other hand, infusion of calories through peripheral veins limits the caloric concentration of the infusate and require large volume to meet nutritional needs. There is also an increased incidence of venous thrombosis whenever the dextrose concentration of the infusate exceeds 10%. Some of these complications can partially be prevented by simultaneous infusion of fat emulsion which in addition to their high caloric content also appear to protect peripheral veins from thrombosis. The reported experience with parenteral nutrition in burned children is limited and critical reviews are nonexistent. We have therefore presented the experience with parenteral nutrition of both the Cincinnati and Boston Units of the Shriners Burns Institute. 

This chapter has been devised to provide a broad survey of the state of the art of research and applications in the field of hydrogen cathodes. Analysis of problems was preferred to mere recipes of preparation and sterile quotations of experimental parameters. Although the main target has been to illustrate the special demands for application, the chapter provides in fact an interplay between theory and practice, emphasizing on one hand the importance of theory in guiding research and development, and on the other hand the irreplaceable role of the feedback from experiments to orient theory. 

Distillations of specially chemicals where contamination can be a problem. The betel) equipaient can be cleaned or sterilized between batch runs. 

Rubber closures for vials or other containers being filled aseptically on an industrial scale are nonporous but share some of the problems of porous loads. They are most frequently steam sterilized by passage through double-ended rotary washer autoclaves, which by agitation of the product ensure effective steam penetration to even the potentially occluded parts of the closures. Steam comes into direct contact with these bulk items they are not usually wrapped nor packed into hermetically sealed containers. Special precautions must be taken for unloading to avoid compromising their sterility. Static autoclaves may also be used for prew ashed versions of these types of components. They should then be loaded into the autoclave in shallow layers in perforated trays or boxes. 

Direct methods of measuring gas concentration include gas chromatography and infrared spectroscopy. Both methods are dependent upon small samples, and the problems of drawing these samples should not be underestimated. The location of multiple sample pons should be such that a representative sample of a hopefully homogeneous gas mixture is obtainable. With most sterilizers operating at positive pressures, it is not usually necessary to have any special means of withdrawing the gas, but it is essential to have sample lines heated and insulated to avoid condensation of gas and water between the sterilizer and the analytical instrument. 

These advantages are, however, often connected with some problems. For instance if growing cells are used, then increased cost for unfavourable product/volume/time efficiency may occur, control of an increased number of regulation parameters is required, operations should be under sterile conditions, and compliance with regulations for handling special biological systems (biohazards) has to be taken into account. 

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