Hospital sterilizer

Hospital sterilizer loads vary in composition, thus the challenge presented to the test organism can vary considerably, depending on the type and contents of packages in which they are placed. The benefits of a standardized test-pack constmction and test protocol are obvious, and such recommendation is made by AAMI for steam and ethylene oxide sterilizers (11). More recentiy in European (CEN) and International (ISO) standards, biological indicators are considered as additional information supplemental to the measurement of physical parameters. Indeed, for sterilization using moist heat (steam), the biological indicator information is not considered to be relevant. 

It is necessary to determine the bioburden and make cycle verification studies when ethylene oxide sterilization is used, as it is for other sterilization methods. The manufacturer of hospital sterilization equipment provides cycle recommendations based on the expected bioburden and the consideration of an appropriate safety factor. In ethylene oxide sterilization, it is necessary to determine if residues of the stefilant are absorbed by the sterilized article, and to examine the possible formation of other potentially toxic materials as a result of reaction with ethylene oxide. 

Provisions must be made for allowing residues of the stefilant absorbed by the product to dissipate by using aeration cabinets that have forced-air circulation at elevated temperatures. The amount of remaining absorbed stefilant should be determined before releasing the sterilized articles. If, as in the case of hospital sterilization, such studies are not feasible, the recommendations of the manufacturers of the articles sterilized or of the aeration equipment should be obtained. The permissible residue concentrations are 10—250 ppm, depending on the type of article and on its intended use. 

General recommendations for instmmentation include monitoring gas concentration, temperature, time, and the moisture content of the chamber. Hospital sterilizers are not usually equipped with instmmentation providing direct display of gas concentration and moisture content. These rely instead on a specific sequence of steps performed automatically and the recording of pressure which when 100% ethylene oxide is used is a perfect measure for the concentration of this gas. 

Preparation of ethylene glycol for antifreeze and synthetic textile fibers (60%), hospital sterilant (15%), surfactants (10%), other chemicals (10%). 

Steam for sterilization can either be generated within the sterilizer, as with portable bench or instrument and utensil sterilizers, in which case it is constantly in contact with water and is known as wef steam, or can be supplied underpressure (350-400kPa) from a separate boiler as dry saturated steam with no entrained water droplets. The killing potential of wef steam is the same as that of dry saturated steam at the same temperature, but it is more likely to soak a porous load creating physical difficulties for further steam penetration. Thus, major industrial and hospital sterilizers are usually supplied with dry saturated steam and attention is paid to the removal of entrained water droplets within the supply line to prevent introduction of a water fog into the sterilizer. 

The U.S. market in hospital sterilizing equipment is ca 70 x 10 . Manufacturers of various types of equipment are given in Table 1. 

The critical parameters of ethylene oxide sterilization are temperature, time, gas concentration, and relative humidity. The critical role of humidity has been demonstrated by a number of studies (11,18,19). Temperature, time, and gas concentration requirements are dependent not only on the bioburden, but also on the type of hardware and gas mixture used. If cycle development is not possible, as in the case of hospital sterilization the manufacturer s recommendations should be followed. 

Hospital sterilization is more limited in the availabiHty of sterilization methods and of packaging materials. Microbial invasion can occur particulady when articles are wrapped in traditional fabrics such as muslin (140-thread-count cotton). The expected shelf life of hospital-wrapped and sterilized articles is considered to be ca 21—30 days when a double-wrapping technique is used. Double-wrapping requires two successive wraps, each having a layer or layers of an approved packaging material. 

This is certainly the most widely used and most versatile moist-heat sterilization method. Accordingly, it is widely used not only for sterilization of pharmaceutical products but also for laboratory and hospital sterilization and for the treatment of medical devices. Nonetheless, it has significant limitations, especially in pharmaceutical use, which are described later. The sterilizing medium is obviously pure pressurized saturated steam. The word saturated means that the steam is in thermodynamic equilibrium with its liquid form (water) at the temperature being considered. 

Of 16 hospital sterilization operators who had been exposed to ethylene oxide and underwent medical and ocular examinations, 14 had lens opacities and 12 had abnormal contrast vision (an abnormality that is nonspecific to cataracts but which often supports the diagnosis) (16). 

Estrin WJ, Bowler RM, Lash A, Becker CE. Neurotoxicological evaluation of hospital sterilizer workers exposed to ethylene oxide. J Toxicol Chn Toxicol 1990 28(l) l-20. 

Sobaszek A, Hache JC, Frimat P, Akakpo V, Victoire G, Furon D. Working conditions and health effects of ethylene oxide exposure at hospital sterilization sites. J Occup Environ Med 1999 41(6) 492-9. 

Chemical industry Fur fumigants Hospital sterilant Industrial sterilant Lubricants ... 

Estrin WJ, Cavalieri SA, Wald P, et al Evidence of neurologic dysfunction related to long-term ethylene oxide exposure. Arch Neurol 44 1283-1286, 1987 Estrin WJ, Bowler RM, Lash A, et al Neurotoxicological evaluation of hospital sterilizer workers exposed to ethylene oxide. Clin Toxicol 28 1-20,1990 Fukushima T, Abe K, Nakagawa A, et al Chronic ethylene oxide poisoning in a factory manufacturing medical appliances. Journal of Social and Occupational Medicine 36 118-123,1986... 

Hospital sterilizer work Ethylene oxide, glutaraldehyde... 

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