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7: Chemical Sterilization |
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By - Pauline W. Fallis,
Chemical sterilization includes both liquid and gas chemicals. Most
electrologists are familiar with liquid chemical sterilization, but there
are gas forms as well.
The most frequently used liquid sterilants used in office settings are 2%
alkaline glutaraldhyde, peroxyacetic acid, and sodium hypochlorite
(household bleach). All liquid sterilants are disinfectants that have the
capability of sterilizing when the exposure time is considerably
lengthened. As with any other form of sterilization, all items must be
clean before sterilizing. In order for sterilization to take place, each
item must be completely immersed in the sterilant solution, so that all
surfaces are in contact with the liquid for the specified time indicated by
the manufacturer. As only unwrapped instruments are sterilized in liquid
sterilants, they do not stay sterile, after they are removed from the
solution. The chances of contamination of sterile items is very high,
because there is nothing to protect them.
Alkaline glutaraldehyde 2% is the most common of the liquid sterilants
used today. For this solution to be effective the item must be completely
immersed in the liquid for about 10 hours. There are no monitoring devices
to ensure the effectiveness of the process. However, there are testing kits
available from the suppliers, to test the strength of the solution so that
it is within the parameters to be an effective sterilant. As long as the
results of the test show it has not been contaminated by organic material
(protein or blood) or diluted by too much rinse water, it may be used for
the shelf life of the chemical (14 to 30 days, depending on the
formulation).
Being a toxic substance, 2% alkaline glutaraldehyde is regulated by the
Occupational Safety and Health Administration (O.S.H.A.), in the U.S.A.,
and is included in the Workplace Hazardous Materials Information System
(W.H.M.I.S.) in Canada. Be careful when using this solution. Use it only in
well ventilated rooms, in covered containers (plastic) and when wearing
household rubber gloves. Immediately after removing articles from the
solution, make sure they are rinsed thoroughly with sterile distilled
water.
Peroxyacetic acid is a liquid sterilant that is only used safely within the
confines of a special sterilizer. It is used in a formulation of .2%, with
a buffer and anticorrosive dry powder added. The sterilizer automatically
controls and monitors the time, temperature and concentration of the
solution. The cycle is completed when the items are rinsed with sterile
distilled water. The cycle is usually 12 minutes exposure time, followed by
4 thorough rinses. When the cycle is completed the solution and rinse water
are discharged down the drain into the sanitary sewer system. Peroxyacetic
acid can not be reused. One thing about peroxyacetic acid is that the
process may be monitored by either bacillus subtilis or bacillus
stearothermophilus biological indicators.
Due to the ability of this process to be monitored and due to the short
length of the sterilizing cycle, this method of sterilization for
immersible but heat sensitive items is becoming more popular in hospitals.
But due to the high cost of the sterilizing device and the chemical, it is
not a viable alternative for electrologists.
Sodium hypochlorite, or household chlorine bleach, is the last liquid
chemical sterilant. This sterilant is not often used. Although it is
powerful, it is an unstable sterilant. As with all other methods of
sterilization, items must be cleaned before being sterilized in sodium
hypochlorite. The items must be completely immersed in the solution for at
least 20 minutes at 20 degrees C. or 68 degrees F., then rinsed thoroughly
with sterile distilled water. This process can not be monitored. Because
sodium hypochlorite gives off a strong odour which will irritate eyes and
skin, it should only be used in a well ventilated room.
Chemical vapour, is another chemical sterilizer. Chemical vapour
sterilization is used for items made from metals like carbon steel that
will corrode in the presence of steam or moisture. The sterilizer uses a
combination of 1% formaldehyde and alcohol in a gaseous form as the
sterilant. It sterilizes at 132 degrees C. or 270 degrees F., and therefore
is not suitable for the sterilization of items that are heat sensitive,
like plastic or rubber. As liquids absorb gas, they cannot be sterilized by
this method either. The sterilization cycle takes approximately 30 to 35
minutes. When the gas is exhausted from the chamber it is normally captured
by a chemical filter canister. When fabric items are sterilized, each load
must contain a biological indicator because the fabric tends to absorb the
gas, and thus it may not be as effective. The biological indicator of
choice is bacillus stearothermophilus. Of all the chemical sterilization
processes, the gas chemical vapour method of sterilization is the only one
that can be done for wrapped items, therefore sterility can be maintained.
The problem with this method of chemical sterilization, is that the
sterilizer is quite expensive.
These are the main liquid and gas chemicals used for sterilization in an
office setting. They are by no means the only ones sold, but they are the
only ones that have been thoroughly studied and are proven to be effective.
Sterile items must be carefully handled after they are removed from the
liquid sterilants, and must be used immediately. There is no method of
monitoring the effectiveness of 2% alkaline glutaraldhyde or sodium
hypochlorite. For the purpose of sterilizing instruments that must be used
sterile, liquid sterilants are not recommended for electrologists. Steam
under pressure is still the preferred method of sterilization, followed
closely by dry heat.
Remember, that the time that a sterilized item must be sterile, is at the
moment that it is used.
References -
AAMI - Chemical sterilants and Sterilization Methods: A guide to Selection
and Use.
AAMI Technical Information Report, The Association for the Advancement of
Medical Instrumentation, Arlington, Virginia, U.S.A., 1990.
Jdorette, W.H.L, ed. - The Central Service Technical Manual, International
Association of Hospital Central Standards Association, Chicago Illinois, U.
S. A., 1981.
Fallis, P. W. - Handbook of Infection Control in Office-Based Health Care
and Allied Services - Canadian Standards Association, Plus112, Toronto,
Ontario, Canada, 1994.
Rutala, W. A., The 1994, 1995 and 1996, APIC Guidelines Committee, APIC
Guideline for the Selection and Use of Disinfectants - American Journal of
Infection Control, August, 1996, Volume 24, Number 4, Page 333.
Whipple, L., Helgeson, J., Infection Control Practices and Sterilization
Standards, The Society of Clinical and Medical Electrologists Inc.,
Massachusetts, U. S. A., 1993.
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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