sterilization in medicine

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STERILIZATION in medicine (Latin sterilis — sterile) — liberation of any substance or a subject from microorganisms by impact on them physical or volumetric factors.

Processing by various means of materials and products began to be applied to their S. already since the beginning of opening in the field of microbiology. J. Lister for the first time stated the requirement: «Nothing shall concern a wound, without being obesplozhenny». Methods, means and the modes of sterilization in the USSR are standardized.

The page is applied in medicine, microbiology, a gnotobiologiya, the food industry and other industries of the national economy (e.g., S. of space automatic devices etc.). Products of repeated use will be sterilized in the institutions using them, products of single use — at the industrial enterprises.

In medicine will sterilize all products (devices, devices, tools, materials, etc.) adjoining to a surface of a wound, blood for transfusion or drugs for hypodermic, intramuscular and intravenous administration and also for peroral introduction to children of early age, etc. S. is a basis asepsises (see).

Methods and S.'s means shall provide death of all, including high-steady microorganisms, both pathogenic, and nonpathogenic. Disputes of microorganisms are steadiest against the prevailing majority of means of S. Therefore the possibility of use for S. of certain means is estimated by existence at them the sporotsidny activity shown in acceptable time limits. The methods used in practice and S.'s means shall be effective, safe and not spoil the sterilized objects.

There are physical and chemical methods of sterilization. Carry to physical methods: steam, goryachevozdushny (air method), sterilization by infrared radiation, filtering, radiation. Carry to chemical methods gas and S. solutions of chemical drugs. The choice of this or that method for S. of specific products is defined by feature of a method — its advantages, shortcomings and properties of the sterilized product.

Implementation in practice of health care and other industries of a large number of products from thermolabile materials led to development of the cold methods C. which are carried out at a temperature not over 100 °. The methods of filtering mentioned above, radiation, gas and use of solutions of the chemical sterilizing drugs concern to them.

Except listed, continue to apply a traditional method of boiling, to-ry, however, as showed numerous researches, does not provide full S.: nek-ry sporous forms of microorganisms, viruses and vegetative forms of separate cocci at the same time do not perish. Therefore the value of this method C. shall be recognized as limited; it cannot be regarded as perspective and its use to lay down. institutions shall stop in process of providing them with the new sterilizing equipment. Boiling keeps the value for disinfection (see).

During the use of steam, goryachevozdushny, radiation and gas methods of a product will sterilize in packaging.

At a steam method the sterilizing agent is a water saturated steam with an excessive pressure and rather low temperature — 110 — 132 ° on exposure (time of sterilizing endurance) of 60±20 min. This influence at the high reliability caused by the mechanism of effect of steam on a microbic cell, its active penetration between the sterilized objects and in capillary porous materials is quite sparing for the processed materials. The lack of a steam method is that, being condensed, steam humidifies the sterilized products, can cause corrosion of products from metals, unstable to it, worsens storage conditions and increases danger of secondary planting by microbic flora of the sterilized products.

The Goryachevozdushny method C. is carried out by a dry hot air. At the same time the sterilized objects are not humidified and therefore the shortcomings noted above are excluded. However the dry air heated insufficiently dries up a microbic cell and does it steadier against influence of heat. Therefore at goryache-vozd an ear method the sterilizing temperature makes 160 — 200 °, and exposure — 60±10 min. Need of use of high temperature and long exposure limit the range of products and packing materials, to-rye it is possible to sterilize by such method.

The page is reached by infrared radiation due to thermal influence (temperature to 300 °) within 30 min.

For S. by method of filtering of thermolabile liquids, such as medicinal substances, biol. drugs (blood plasma, serums, vaccines, anatoxins), use bacterial filters (see) various design — the membrane and deep, detaining microorganisms of 0,3 microns in size and more. Membrane filters have a time of the identical size and microorganisms on a surface like a sieve detain. Deep filters are characterized by the difficult mechanism of detention (the adsorptive, inertial, etc.); diameter of their time is heterogeneous; microorganisms keep both on the surface of the filter, and in its internal structure (matrix). Deep filters can be ceramic (Shamberlan's candles, Berkefelda), porcelain, glass, asbestos; membrane filters — disk and cartridge, are manufactured they of the mixed esters of cellulose, polyamide, polyvinylchloride, etc. Filtering is carried out both under vacuum, and under pressure.

The highly effective and reliable radiation method allows to carry out S. in packaging and even in a transport container. Serve as the sterilizing agents gamma radiation (sources 60 Co and 137 Cs) and the accelerated electrons. Antimicrobic action of both agents their penetration is identical, significantly various that affects technology of process and the nomenclature of the sterilized products, to-rye shall be selected according to the radiation used for S. In the USSR and in the majority of the countries of the world as the sterilizing dose are recognized 2,5 Mrad (25 kgr). However according to the international recommendations existing in the USSR specification of the sterilizing dose for the certain product made at the specific enterprise depending on an obsemenennost (initial contamination) by its microorganisms, radioimmunity of kontaminat is required.

At a gas method C. as sterilizing gases use ethylene oxide and formaldehyde; ethylene oxide in mix with air in concentration from 3 to 80% is explosive therefore it is applied in mix with phlegmtizators. The composition of these mixes and content of ethylene oxide in them are various: e.g., ethylene oxide (10 — 15%) with dv uokiyeyu carbon; ethylene oxide (10 — 12%) from hladona; ethylene oxide (28,5 — 40%) with methyl bromide (mix ABOUT). Also mix of ethylene oxide (50%) is used with sweep l formiate, but this mix is explosive. Optimal conditions of S. during the use of pure ethylene oxide and in its mix with carbon dioxide and hladona is the dose of ethylene oxide of 750 — 1000 mg on 1 dm3 of the sterilizing camera, temperature 55 — 60 °, relative humidity of 80 — 100%, exposure 4 — 6 hour. S.'s carrying out by pure ethylene oxide and mix ABOUT at t ° 18 — 23 ° demands increase in exposure up to the 16th hour. The products sterilized using the specified compoundings need to be decontaminated, napr, airing in rooms with good ventilation within several days.

Formaldehyde (see. Ant aldehyde ) for S. it can be used at generation of its vapors mixed with water vapor in special sterilizers, in to-rykh for increase in efficiency preliminary vacuum is created. The page is carried out by evaporation of 1,2 ml of 16% of water solution of formaldehyde for 1 dm 3 the sterilizing camera at t ° 70 ° and exposures not less 5th hour. Upon termination of exposure and removal of formaldehyde neutralization of its residual number of 25% by solution of ammonia (0,9 ml/dm3) within 1 hour is carried out.

For chemical S. use hydrogen peroxide, connections on the basis of hydrogen peroxide and aldehydes. Solutions of hydrogen peroxide are recommended for use in 6% of concentration at t ° 18 — 20 both 50 ° and exposures 6 and 3 hours respectively. Derivatives of hydrogen peroxide — peracid-peracid (peroxyacetic and peroxyformic) in concentration of 1,0% are recommended for sterilization of products from thermolabile materials. The most active aldehyde is glutaric dialdehyde; it can be used for S. in concentration of 2,5% on exposure the 5th hour.

For operating control of parameters C. (temperature, pressure, amount of gas in the sterilizing camera, etc.) use physical and chemical means. So, temperature is registered by means of the maximum thermometers, thermocouples, etc., pressure — manometers, analytically define amount of actively active ingredient in solution; temperature, a dose of gas, etc. are controlled by chemical tests — the substances changing the color or physical condition at certain values of the specified parameters. The majority of the known chemical tests C. induce only one parameter — temperature or a dose of sterilizing gas.

Assessment of efficiency of process is carried out the most specific and the general for all ways C. — bacterial. by method. As the test use an object from the material similar sterilized, inseminated by a test microorganism, i.e. a microbe with certain parameters of resistance to the specific sterilizing agent. Density of planting of a test object shall be created taking into account a usual obsemenennost by microbes of the sterilized product.

Sterilization in surgery — destruction of microbes on the objects touching a wound — is a basis of an asepsis. It is carried out by various methods, according to a variety of the sterilized objects and materials. Microorganisms can get to a wound from air, at contact with hands of the surgeon, surgical instruments, a dressing material, operational linen, etc. or to be implanted into tissues of the patient with a suture material, prostheses, devices, etc. From air the microbes which are on motes in drops of saliva, a bronchial secret, etc., the weighed in air operational and dressing pokhmeshcheniye get to a wound.

Disinfecting of air of rooms is performed by filtering, with the help a cut dust and the drops of liquid weighed in air, and UV rays are late. Filters install on the ways of air flow (in conditioners, stitched ventilating channels). The best effect of S. of air is reached at so-called laminar type of ventilation of operating rooms when the air flow, having passed the bacterial filter, moves with rather high speed (see. Surgery block ). Disinfecting of air UV rays in operating rooms and dressing rooms is carried out bactericidal lamps (see).

A dressing material, linen, gloves (see. Gloves medical ) will sterilize in autoclave (see). Devices, S. in to-rykh it is carried out by fluid steam (without pressure), in a crust, time are not applied as well as flaming (burning). The last is used only at S. of an inner surface of the big Tazy intended for washing of hands of the surgeon before operation, setting fire to the alcohol poured in them 96%.

The page can be made a saturated steam under pressure in the autoclave. In such a way will sterilize all-metal endoprostheses, syringes, and also the tools contaminated by spore-forming activators mephitic gangrene (see).

Any way C. can not give effect if on the surface of the tool the insignificant remains of the dried-up blood, pus remained at least. Therefore upon termination of operation it is necessary to clear the used tools immediately and carefully (to separate parts of difficult tools), to wash up running water, to wipe, process mix of hydrogen peroxide with detergents (see) to wash out and drain again.

Cutting instruments under the influence of a boiling water and couple are exposed to microcorrosion and are quickly rebated, in this regard will sterilize them, calcinating in a drying and sterilizing case (see. Knives surgical ). Dry hot air will often sterilize both other metal and glass tools.

If necessary cutting instruments can be sterilized in the chemical way — immersion in alcohol not less than for 2 hours. On condition of their careful prerefining chemical S. can provide sterility of these tools. Not cutting instruments, and also syringes and needles to them can be sterilized a dry hot air in drying and sterilizing cases.

Metal tools, glassware and rubbers if necessary can be sterilized boiling in 2% water solution of hydrosodium carbonate; however vegetative forms of nek-ry microbes, viruses and disputes do not perish in a boiling water, in this regard fractional sterilization is applied.

At use of chemical substances for aseptic preparation of hands of participants of operation and skin of the patient only relative and not resistant sterility therefore to these objects the term «sterilization» is usually not applied is reached, and speak about processing of hands (see), processing of a surgery field (see. Surgery field).

For prevention of implantation of microbes in fabric of an operational wound will sterilize a suture material, drainages and irrigators of cavities and wounds, prostheses, transplants and other objects, napr, artificial pacemakers of heart and their electrodes.

Drainages, tampons, rubber graduates and irrigators will sterilize in the autoclave. The suture material is processed by specially developed methods (see. Suture material) or subject beam S. industrially. Metal prostheses will sterilize in sterilizers a pressured steam. Biol. prostheses (bones, valves of heart, joints, vessels) take from donors in aseptic conditions and will sterilize in the solutions most often prepared on the basis of formalin. So, skin and bone transplants process in formalinoglitserinovy mix (concerning 1:1) during the 2nd hour. Artificial pacemakers of heart are made tight, and their outer surface will be sterilized by any antiseptic agent. Usually it is made industrially, and the sterile device arrives for implantation in sterile film packaging.

In surgical establishment bacterial is systematically carried out. control of sterility of air, tools, hands of the surgeon, surgery field and materials.

Sterilization of pharmaceuticals. Pages are exposed the pharmaceuticals used parenterally, eye dosage forms, and also pharmaceuticals for washing of cavities, processing and treatment of burns and wounds. Water and water solutions of medicinal substances, mineral and vegetable oils, oil solutions, fats, lanolin, vaseline, powders, tablets, etc. can be objects C.

For S. of pharmaceuticals use hl. obr. thermal methods — steam and goryachevozdushny.

The most widespread method is S. saturated water vapor under pressure at t 120 ° in steam sterilizers — autoclaves. Exposure depends on physical. - chemical properties of drug, volume of liquid, and also from design features of the used equipment. Water solutions of medicinal substances in the glass hermetically corked bottles or ampoules will be sterilized no more than 30 min. Fats and oils at this temperature maintain during 2 hours

S.'s Goryachevozdushnuyu of wasps ushchestvlyat a dry hot air in drying and sterilizing cases at t ° 180 — 200 °. By this method will sterilize hl. obr. heat-resistant powders, fats, mineral and vegetable oils. This way it is impossible to sterilize water solutions for injections since at high temperature medicinal substances decay and ampoules are broken off, and at lower air temperatures the sterilizing effect is not provided.

For solutions of medicinal substances, and also the vaccinal and serumal drugs sensitive to thermal influence, use a method of the sterilizing filtering via microporous filters. The increasing application for S. of liquid pharmaceuticals is found by membrane microfilters with a constant pore size, size to-rykh does not exceed 0,3 microns. During the use of filters from glass or asbestos fibers for sterilization of the solutions entered parenterally at the exit of a filtrate the membrane sterilizing filter shall be installed. All technological operations at the sterilizing filtering shall be performed in strictly aseptic conditions in boxing or with use of specially equipped table, with a laminar flow of pure sterile air.

Bibliography: Belovo O. I., etc. Manufacturing techniques of sterile solutions in the conditions of drugstores, M., 1982; Vashkov V. I. The means and methods of sterilization applied in medicine, M., 1973; To and in m and G. Ya. N, With N e and p e in and N. S. and Yavorskaya E. S. Sterilization of drugs by means of filters, Chemical - pharm. zhurn., t. 13, jVe I, page 91, 1979, bibliogr.; Loshonts of. Intrahospital infections, the lane with Wenger., M., 1978; Methods, means and modes of sterilization and disinfection of products of medical prescription, Terms and definitions, GOST 25375-82, M., 1982; V. I Pods. General surgery, M., 1983; Tumanyan M. A. and Kaushansky D. A. Radiation sterilization, M., 1974, bibliogr.; X about r t and G. P. Modern technology of creation of superpure rooms, Chemical - pharm. zhurn., t. 13, No. 2, page 89, 1979; Beit-rage zur Sterilisation und Aseptik, hrsg. y. R. Machmerth u. A. Giinther, S. 28, Lpz., 1976; Handbuch der Desinfektion und Sterilisation, hrsg. v. H. Horn, Bd 2, B., 1973.

C. A. Rusanov, V. A. Sakharov (sterilization in surgery), A. I. Tentsova, V. V. Karchevskaya (sterilization of pharmaceuticals).