downward displacement and the prevacuum,
Downward Displacement Autoclave.In the
downward (gravity) displacement autoclave, air in the
chamber is forced downward from the top of the
chamber. The temperature in the sterilizer gradually
increases as the steam heats the chamber and its
contents. The actual timing does not begin until the
temperature is above 245EF (118EC).
Prevacuum, High-temperature Autoclave.
The prevacuum, high-temperature autoclave is the
most modern and economical to operate and requires
the least time to sterilize a single load. By use of a
vacuum pump, air is extracted from the chamber
before admitting steam.
This prevacuum process
permits instant steam penetration to all articles and
through all cotton or linen dry goods. The sterilization
time is reduced to 4 minutes. The temperature of the
chamber is rapidly raised and held at 274EF (134EC).
The cycle is timed automatically.
Sterilizing Times.If the temperature is
increased, the sterilization time may be decreased. The
following are some practical sterilization time periods.
3 minutes at 270EF (132EC)
8 minutes at 257EF (125EC)
18 minutes at 245EF (118EC)
All operating rooms are equipped with high-speed
Wrapped, covered, opened
instruments placed in perforated trays are flash
sterilized for 3 minutes at 270 E F (132 E C).
Sterilization timing begins when the above
temperature is reached, not before.
Dry-Heat Sterilization.The use of dry heat as a
sterilizing agent has limitations. It should be restricted
to items that are unsuitable for exposure to moist heat.
High temperatures and extended time periods are
required when using dry heat. In most instances, this
method often proves impractical. The temperature
must be 320EF (160EC), and the time period must be at
least 2 hours.
CHEMICAL STERILIZATION.Only one
liquid chemical, if properly used, is capable of
rendering an item sterile.
That chemical is
glutaraldehyde. The item to be sterilized must be
totally submerged in the glutaraldehyde solution for 10
hours. Before immersion, the item must be thoroughly
cleansed and rinsed with sterile water or sterile normal
It should be noted that this chemical is
extremely caustic to skin, mucous membranes, and
The most effective method of gas chemical
sterilization presently available is the use of ethylene
oxide (ETO) gas. ETO gas sterilization should be
used only for material and supplies that will not
withstand sterilization by steam under pressure. Never
gas-sterilize any item that can be steam-sterilized. The
concentration of the gas and the temperature and
humidity inside the sterilizer are vital factors that
affect the gas-sterilization process.
ETO gas-sterilization periods range from 3 to 7
hours. All items gas-sterilized must be allowed an
aeration (airing out) period. During this period, the
ETO gas is expelled from the surface of the item. It is
not practical here to present all exposure times, gas
concentrations, and aeration times for various items to
be gas-sterilized. When using an ETO gas-sterilizer,
you must be extremely cautious and follow the
manufacturers instructions carefully.
Preparation of Supplies for Autoclaving
Comply with the following guidelines in preparing
supplies that are to be autoclaved.
Inspect all articles to be sterilized, making sure
they are clean, in good condition, and in working
Wrap instruments and materials in double
muslin wrappers or two layers of disposable
When muslin wrappers are routinely used,
launder them after each use, and carefully
inspect them for holes and tears before use.
When articles are placed in glass or metal
containers for autoclaving, place the lid of the
container so the steam will penetrate the entire
inside of the container.
Arrange the contents of a linen pack in such a
way that the articles on top are used first.
Label every item that is packaged for
sterilization to specify the contents and
Do not place surgical knife blades or suture
materials inside linen packs or on instrument
trays before sterilization.