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In the past few years it has become apparent that the only acceptable
standard for the instruments that you use in your practice is sterile. Why
should you sterilize? Because you are using forceps and needles that enter
the skin. Anything that goes below the skin must be sterile. Even though
the heat used to remove hair is extremely hot, it does not heat long enough
to sterilize.
There are several acceptable methods of sterilization that can be used.
There is steam under pressure. There is dry heat. And there is chemical
sterilization, either liquid or gas. For the next several issues of this
news magazine, I will review the use of each of these methods of
sterilization. The first, "Steam Under Pressure", is reviewed below.
STEAM UNDER PRESSURE
(THE AUTOCLAVE)
Steam under pressure is the most effective and widely used form of heat
sterilization used today. It is both simple and inexpensive. The amount of
heat that the air can carry is directly related to the amount of moisture
present. The more moisture in the air, the more heat that can be carried.
Steam under pressure is an effective carrier of heat. For example, a
pressure cooker, cooks more quickly and effectively than an oven. There is
one disadvantage, it cannot be used to sterilize heat and moisture
sensitive items, powders or petroleum products. Steam kills microorganisms
by first softening their protective coat or layer, which then will allow
the heat to quickly coagulate the sensitive protein material inside.
Steam under pressure requires four conditions in order to be effective.
They are, contact, temperature, exposure time and moisture.
Any device being sterilized must be completely surrounded by steam. Steam
being surface sterilant, needs direct contact with the microorganisms in
order to be effective. To adequately sterilize, the temperature of the
steam inside the sterilization chamber, must be at least 121 degrees
Centigrade, or 250 degrees Fahrenheit throughout the entire exposure time.
Devices must be exposed to the required temperature for a minimum period of
time in order to kill microorganisms. The higher the temperature, the less
time it takes. For sterilization to take place, there must be adequate
moisture present in the sterilization chamber. The steam must be saturated,
or in other words, reach a relative humidity of 100%.
Sterilization failures do occur, usually because all of the above four
conditions have not been met. However, sterilization is also extremely
difficult to achieve if the items being sterilized are improperly prepared,
even when all of the conditions have been met. There are some frequent
causes of sterilization failure. Inadequate cleaning of items, causing
foreign matter to protect the microorganisms. Wrapping an item too tightly,
hindering air removal and steam penetration of packages - air and steam do
not mix; steam must replace the air in order for sterilization to take
place. Overloading an autoclave will prevent the steam from surrounding all
surfaces. Items may be positioned incorrectly so that the containers may
trap air or water, for instance, pans, bottles or other airtight containers
must have their tops removed and the containers placed on their sides.
In order to be assured that sterilization has taken place, the process must
be monitored routinely. They are monitored biologically, mechanically, and
chemically. The biological indicator for steam, is "Bacillus
Stear-othermophilus spores", which are non pathogenic, but whose resistance
and numbers are far greater than any microorganisms you would ever
encounter. They present a greater sterilization challenge then your
sterilizer would ever be faced with. Mechanical indicators include clocks,
thermometers, pressure gauges and sometimes, recording devices. As most
table top autoclave models do not have recording graphs or strips, it is
recommended that you record the temperature or pressure indicated on the
gauge yourself, at precise intervals during the sterilization cycle. If
there are recording graphs or strips, they must be examined to ensure that
the correct time, temperature and pressure has actually been reached during
the cycle. Chemical indicators include chemically impregnated tapes and
strips, or glass ampules containing indicator pellets. These can be most
useful for table top sterilizers that rarely have built in recording
devices. These indicators should be used for every sterilization load. A
multi parameter process chemical indicator is probably the best type for
these table top models. The indicators may be either internal or external.
Internal indicators demonstrate by colour change that the inside of the
package has been penetrated by steam. External indicators, like indicator
tape, or markings on packaging materials, show by colour change that the
item has been through a sterilization process, but not that it is actually
sterile. Your equipment, procedures and techniques, will determine which
chemical indicator will best suit your needs.
It doesn't matter what type of steam sterilizer you have. A traditional
table top model, a table top with a cassette as the chamber, or one with a
basket. The four conditions must be met for sterilization to take place,
and the process must be monitored to assure a sterile product.
REFERENCES -
Association for the Advancement of Medical Instrumentation - "Good Hospital
Practice: Steam Sterilization and Sterility Assurance" - 1988.
Canadian Standards Association - "Effective Sterilization in Hospitals by
the Steam Process" - CAN/CSA - Z314.3-91, Toronto, Ontario, 1991.
Dornette, W.H.L.ed, - "Central Service Technical Manual", International
Association of Hospital Central Service Management, 1981, Chicago,
Illinois, pages 50 to 67.
Fallis, P.W. - "Handbook on Infection Control in Office-Based Health Care
and Allied Services." - Canadian Standards Association, 1994, Toronto,
Ontario - pages 67 to 75.
INFECTION CONTROL ARTICLES
- PREPARING FOR THE PATIENT/CLIENT
Spring 2001, Volume 8, Number 1
- PREVENTING INFECTION FOR ELECTROLYSIS
Fall 2000, Volume 7, Number 2
- INFLUENZA
Spring 2000, Volume 7, Number 1
- MICROORGANISMS AND INFECTIOUS DISEASE
Summer 1999, Volume 6, Number 2
- BLOOD BORNE INFECTIOUS DISEASES AND PERSONAL PROTECTION
Spring 1999, Volume 6, Number 1
- MICROORGANISMS & INFECTION
Fall 1998, Volume 5, Number 2.
- BIOLOGICAL TESTING OF YOUR STERILIZATION PROCESS
Spring 1998, Volume 5, Number 1
- STEAM STERILIZATION
Fall 1997, Volume 4, Number 2
- CHEMICAL STERILIZATION
Spring 1997, Volume 4, Number1
- DRY HEAT STERILIZATION
Fall 1996, Volume 3, Number 2
- STERILIZATION
Spring 1996, Volume 3, Number 1
- IS YOUR USE OF NEEDLES SAFE IN YOUR PRACTICE?
Fall 1995, Volume 2, Number 2
- PREPARING INSTRUMENTS FOR STERILIZATION
Spring 1995, Volume 2, Number 1
- WHY ARE GLASS BEAD STERILIZERS NOT RECOMMENDED FOR USE IN ELECTROLOGY?
Fall 1994, Volume 1, Number 2
- STERILIZATION: HOW, WHEN, AND WHAT WITH
Spring 1994, Volume 1, Number1
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