Page 179 - Assurance of Sterility for Sensitive Combination Products and Materials

Preventing health care associated infections 161

Hydrogen peroxide There are two types of hydrogen peroxide (H 2 O 2 )
sterilization available to HCFs. Vapor-phase H 2 O 2 has a rapid cycle time
with low temperature. The by-products of the sterilization process are safe
and do not require special emission controls or abatement. There is good
material compatibility for most medical devices. Some materials like nylon
will become brittle and cellulosic materials will absorb the H 2 O 2 making
validation challenging. A typical vapor-phase H 2 O 2 sterilization takes be-
tween 55 and 75 min for most medical devices. Penetration of vapor-phase
H 2 O 2 is not as good as EO, which means that there are some design features
such as long narrow lumens that are more challenging to sterilize with this
process.
H 2 O 2 gas plasma is generated in an enclosed chamber under deep vac-
uum using radio frequency or microwave energy to excite the gas mol-
ecules and produce charged ions. Many of these charged ions are free
radicals which interact with essential cell components and disrupt cellular
metabolism. The gas plasma cannot penetrate long and narrow lumens and
cellulosic materials will absorb the H 2 O 2 causing the sterilization process
to fail.
Hydrogen peroxide/ozone Hydrogen peroxide/ozone sterilization
combines a cycle composed of hydrogen peroxide exposure phase followed
with an ozone exposure phase. Ozone can kill both airborne and water-
borne microorganisms. It is a powerful oxidant that destroys microorgan-
isms. The highly unstable ozone gas reverts to oxygen and water at the
end of the sterilization cycle. There are no toxic by-products to this steril-
ization method. The process operates at 30–35 °C making it usable for all
heat-sensitive medical devices. This process is compatible with a wide range
of materials. The hydrogen peroxide/ozone sterilizer can be used for many
flexible endoscopes. The manufacturer’s information should be checked for
any restrictions on lumen size. Ozone sterilization should not be used for
products containing the following materials: natural rubber, latex, textile
fabrics, copper, brass, bronze, zinc, and nickel.

Peracetic acid Peracetic acid is a liquid chemical sterilant that is a bio-
cidal oxidizer that maintains its efficacy even in the presence of organic soil.
The process can be used for high-level disinfection or immediate use ster-
ilization; there is no method for maintaining sterility after the sterilization
process is complete. Peracetic acid is used for immediate use sterilization
of endoscopes in surgery and for high-level disinfection of gastrointestinal
endoscopes.