STERILIZATION IN THE HOSPITAL

STERILIZATION IN THE HOSPITAL

Steam/Autoclaving

  • It involves exposure of microorganisms to saturated steam under pressure in an autoclave achieves their destruction by the irreversible denaturation of enzymes and structural proteins
  • The temperature at which denaturation occurs varies inversely with the amount of water present. Sterilization in saturated steam thus requires precise control of time, temperature and pressure
  • As displacement of the air by steam is unlikely to be readily achieved, the air should be evacuated from the autoclave before admission of steam. This method should be used whenever possible for aqueous preparations and for surgical dressings and medical devices
  • The recommendations for sterilization in an autoclave are 15 minutes at 121 – 124 degree celcius (200 kPa). The temperature should be used to control and monitor the process; the pressure is mainly used to obtain the required steam temperature

Dry Heat

  • Dry heat can be used to sterilize items, but as the heat takes much longer to the transferred to the organism, both the time and the temperature must usually be increased, unless forced ventilation of the hot air is used
  • The standard setting for a hot air oven is at least two hours at 160 degree celcius (320 degree F). A rapid method heats air to 190 degree celcius (374 degree F) for 6 minutes for unwrapped objects and 12 minutes for wrapped objects
  • Dry heat has the advantage that it can be used on powders and other heat-stable items that are adversely affected by steam (for instance, it does not cause rusting of steel objects)

Chemical (Ethylene Oxide/Other Chemicals)

  • The active agent of the gas sterilization process can be ethylene oxide or another highly volatile substance
  • The highly flammable and potentially explosive nature of such agents is a disadvantage unless they are mixed with suitable inert gases to reduce their highly toxic properties and the possibility of toxic residues remaining in treated materials
  • The whole process is difficult to control and should only be considered if no other sterilization procedure can be used. It must only be carried out under the supervision of highly skilled staff
  • The sterilizing efficiency of ethylene oxide depends on the concentration of the gas, the humidity, the time of exposure, the temperature and the nature of the load
  • After sterilization, time should be allowed for the elimination of residual sterilizing agents and other volatile residues, which should be confirmed by specific tests

Radiation

Sterilization of certain active ingredients, drug products, and medical devices in their final container or package may be achieved by exposure to ionizing radiation in the form of gamma radiation from a suitable radioisotopic source such as cobalt 60 or of electrons energized by a suitable electron accelerator. Laws and regulations for protection against radiation must be respected

Gamma radiation and electron beams are used to effect ionization of the molecules in organisms. Mutations are thus formed in the DNA and these reactions after replication

  • These processes are very dangerous and only well-trained and experienced staff should decide upon the desirability of their use and should ensure monitoring of the processes. Specially designed and purpose-built installations and equipment must be used
  • It is usual to select an absorbed radiation level of 25 kGy (2.5 Mrad), although other levels may be employed provided that they have been validated

Plasma Sterilization

  • Plasma is basically ionized gas. When applied by an electric field, it gets ionized into electrons and ions
  • These free radicals and ions interact with living organisms and destroys them
  • Most of the research in plasma sterilization pertains to volume experiments. The process involves UV irradiation, photo-desorption and chemical etching
  • The spores are basically made up of simple atoms like C, O, N, H and the like. The radicals react with these atoms to form simple compounds like CO2, which can subsequently be flushed out. When the organism loses such atoms that are intrinsic to its survival, it dies

Phases of Plasma Sterilization

  • Vacuum: medical instruments are placed in the sterilization chamber (4 cubic feet in capacity). The chamber is sealed and air is pumped out to create a strong vacuum
  • Injection: a solution of 59% hydrogen peroxide and water (from a cassette inserted by the operator at the beginning of every 10 cycles) is automatically injected into the sterilization chamber
  • Diffusion: the solution vaporizes and diffuses throughout the chamber, surrounding the items to be sterilized. Hydrogen peroxide exhibits antimicrobial activity and is capable of inactivating microorganism that it encounters in the sterilization chamber
  • Plasma: radio frequency (RF) energy is applied to create an electrical field, which in turn initiates the generation of the low-temperature plasma, i.e. a cloud of reactive and unstable species. These unstable particles collide with one another to produce a variety of new species, including free radicals that, like the hydrogen peroxide vapor, are capable of inactivating any microorganism, viruses, or spores that may be encountered within the sterilization chamber. In the plasma phase, the activated components ultimately lose their high energy and recombine to form primarily oxygen and water vapor. The combination of the diffusion pretreatment and plasma phases acts to sterilize while eliminating harmful residuals
  • Vent: the RF energy is turned off, the vacuum is released, and the chamber is filled with filtered air, returning it to normal temperature atmospheric pressure. After 10 sterilization cycles, the cassette self-ejects into an internal receptacle for future disposal

SUMMARY

Sterilization is necessary for the complete destruction or removal of all microorganisms (including spore-forming and non-spore forming bacteria, viruses, fungi and protozoa) that could contaminate pharmaceuticals or other materials and thereby constitute a health hazard. Since the achievement of the absolute state of sterility cannot be demonstrated, the sterility of a pharmaceutical preparation can be defined only in terms of probability. The efficacy of any sterilization process will depend on the nature of the product, the extent and type of any contamination, and the conditions under which the final product has been prepared

STERILIZATION IN THE HOSPITAL - steam or autoclaving, dry heat, chemicals, radiation, plasma sterilization
STERILIZATION IN THE HOSPITAL – steam or autoclaving, dry heat, chemicals, radiation, plasma sterilization

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