STERILIZATION
Introduction
It is the process of killing all microorganisms
(bacteria, viruses, and fungai) with the use of either physical or chemical
agents. A disinfectant is a chemical substance that kills microorganisms on non
living surfaces, such as sample disks
and surgical instruments. An antiseptic is a chemical that is applied to
a living surfaces to inhibit the growth of microorganisms. Iodoform or pyodine
are antiseptics. Asepsis is the absence of dangerous microbs in living tissue.
Skin can never be completely sterile. The inside
of the body contains
no bacteria and is referred
to as aseptic and class A area in industries are antiseptic areas.
Contamination may be define as when there
is a break in sterility or asepsis. Contamination allows microbs to
enter a surgical place.
Sterilization of items used to perform
surgery in an environment maintaining asepsis during surgery.
Brief History of Sterilization
In the late 1860s, Louis Pasteur, a French
chemist, proved that bacteria were a cause of disease in hu- mans and animals.
He also developed the process of pasteurization which uses heat to kill microorganisms
in milk. His theories led Joseph Lister, an English
surgeon, to develop “antiseptic technique” for per- forming surgery. Aseptic
veterinary surgery began to be practiced in the 1940s. The use of surgical
gowns, caps, masks, and gloves became routine in the 1960s.
Microorganisms and Infection
Wound infection is a common post-operative compli- cation and
dependent on numerous factors. Maintain- ing a sterile operating field is the
factor the veterinar- ian and veterinary staff has the most control over. A surgical patient will never
be completely sterile.
There will always be bacteria present. However, a critical number of
bacteria are required to cause an infection. This number is 105 microorganisms per gram (100,000
organisms/g) of tissue or milliliter of fluid. As long as bacterial numbers do not exceed this number, the nor- mal immune defenses of the body can
prevent infec- tion. The goal of asepsis is to prevent the addition of bacteria
to the surgical site.
Methods of Sterilization
Exposure to harmful
microorganisms can be prevented
by utilizing the correct sterilization methods. Though they are invisible to
the naked eye, organisms capable of causing
infection are everywhere. Sterile bandages,
instruments, and equipment are necessary for prevent-
ing infection in animals receiving veterinary
care.
Steam
The use of steam under pressure is most
commonly used by veterinary hospitals to sterilize items. The three factors
that dictate the success of steam steriliza- tion are temperature, pressure
and exposure time. In- creasing pressure of steam in a closed
container causes the
temperature of the steam to rise. When microbes are exposed to the correct
temperature and pressure for the right amount of time, they are destroyed and
the items they were on become sterile. The device used for steam sterilization is called an autoclave. The minimum time, temperature, and
pressure required to sterilize items is 10 minutes at 275 ºF or 15 minutes at
250 ºF and 15 pounds per square inch of pressure.
The use of surgical gowns, caps, masks,
and gloves inhibits the spread of harmful bacteria.
Heat
sterilizer.
Chemical (Gas)
Some items will be destroyed
when exposed to the temperatures and pressures required for steam sterilization.
These items include plastics, power cables and endoscopes. Ethylene oxide is a
gas that can be used to sterilize these types of items. Exposure to the gas at
under appropriate conditions results in sterility. Ethylene oxide is flammable,
carcinogenic, can cause numerous health problems and is environmentally
harmful. Use of it is strictly regulated.
Plasma
A
safer method of sterilizing heat-sensitive items is plasma sterilization. This
method uses reactive ions, electrons and neutrons to sterilize items in about
45 minutes at temperatures as low as 122 ºF.
Ionizing Radiation
Most
prepackaged sterile items like surgical gloves and suture packets have been
sterilized with ionizing radiation. Exposure of these items to a radioactive
source, such as cobalt 60, destroys microorganisms. This process is expensive
and limited to commercial use.
Cold Chemical
Cold
chemical sterilization is a common and inexpensive method of sterilizing items
that cannot be exposed to steam sterilization. The most common chemical used is
glutaraldehyde. A 2 % glutaraldehyde solution is noncorrosive to metal and
delicate equipment like endoscopes. Immersion times in the solution vary
depending on the item. Items should be thoroughly rinsed with sterile water
prior to being used on a patient.
Storage of
Sterile Equipment
It
is important to store sterilized instruments and supplies in a manner that
maintains their aseptic condition. Keep them in a dust-free, clean environment
until use.
Antiseptics
Ideal antiseptics used in patient treatment prevent the growth of
microorganisms, without necessarily destroying them, and do not harm the
patient.
Characteristics of an ideal antiseptic include:
• Active against pathogens
• Non-irritating
• Cleansing
• Cost effective
• Long shelf life
• Safe for patient and handler
• Stable in the presence of organic matter
