Since many chemical agents are not capable of eliminating all varieties and kinds of microbial life, for example tubercle bacillus, bacterial spores and the filterable viruses, it is more nearly accurate to refer to the process as “chemical disinfection” rather than “chemical sterilization.”
Chemical disinfection is used only when it is not feasible to sterilize an article by heat. Chemical disinfectants tend to set or solidify “proteinaceous” material such as blood, and organisms contained within this protein precipitate. Accordingly, chemical disinfection should not be used for instruments contaminated with blood or tissue fluid.
Several factors are capable of influencing disinfectant actions. Here is the list:
The presence of blood, pus, oil or grease interferes with the action of all germicides. The effective use of soap and water for cleansing is a necessary preliminary step to ensure optimal effectiveness of a disinfectant.
This factor varies from seconds to hours, depending on the kind of disinfectant, the strength of the disinfecting agent, and the characteristics of the organisms to be eliminated. Vegetative organisms may be destroyed in 30 minutes by some of the chemical disinfectants, whereas no amount of time, hours, or days by the same agent would result in sporicidal action.
Usually a weak solution is not as effective as a strong solution of the same disinfectant. An exception is ethyl alcohol; 70% aqueous solution is more germicidal than absolute alcohol.
Usually, room temperature is used. However, most chemical agents are more effective if the temperature is raised.
5. Type of Organism
Some organisms are killed more readily than others. Examples of the resistant forms are the virus of serum hepatitis, tubercle bacillus and certain bacterial spores.
Now that you know the different factors that influence disinfectant action, it is also equally important that you understand the main uses of these disinfectants.
Instruments and Materials
Chemicals used to disinfect certain instruments and materials that cannot be sterilized by heat should use disinfectants instead. Examples of things that need to be chemically disinfected are bougies, cycstoscopes, and cataract knives. Items like these must be immersed in a germicide.
Most of the chemicals are used in the form of solutions, being dissolved in water or in alcohol. From time to time, new chemical compounds appear on the market and all of them have certain advantages and disadvantages. So be careful in choosing the right chemical disinfectant.
Disinfectants are used to remove as many resident and transient organisms of the skin as possible. In surgery, the preoperative preparation of the skin is necessary to prevent unnecessary contamination of the surgical wound. The hands and the arms of the surgical team likewise must be prepared by scrubbing and the application of appropriate disinfectants.
Application to Tissues
Antiseptics are applied to tissues that are or may be the seat of infection, in order to assist them in destroying germs and their products rapidly and completely. When used in this way, the ultimate antiseptic should bring about complete sterilization within its sphere of action without causing any damage to tissue cells. However, the disadvantage of most antiseptics is that in killing the bacteria, they tend to destroy the tissue cells as well.
For this reason, these chemical substances must be used in wounds in weak solutions and for only a short period of time. Many antiseptics have been suggested and used in tissues, and their very multiplicity would indicate that the ideal antiseptic has not been found yet.
It is being recognized to a greater extent that the body tissues have a natural resistance to infection, and that antiseptics are of value only occasionally in the treatment of certain specific types of infection, especially those on the surface of the body.