OR Manager November/December 2021 - 25

Sterilization & infection prevention
Cart Washers
Cart washers were originally designed
to clean transport carts. They function
in a manner similar to washer disinfectors
but on a larger scale. Spray arms
deliver high-temperature water and detergent,
and successive steps provide
rinse water and hot air drying cycles.
Cart washer equipment can also be
designed to process rigid sterilization
containers and instruments. If a cart
washer is designed and used to clean
sterilization containers and instruments,
the same cleaning verification used for
instruments applies to cart washers.
Ultrasonic Washers
Ultrasonic cleaners may also be referred
to as " sonic cleaners. " The term
" ultrasonic " is an appropriate name for
this type of mechanical cleaner. " Ultra "
means beyond, and " sonic " means
sound; they are used for fine cleaning-to
remove soil from joints, crevices,
lumens, and other areas that are
difficult to clean by other methods. The
cleaning action of ultrasonic cleaners
is performed by the use of cavitation.
Cavitation is the process in which lowpressure
bubbles in a cleaning solution
burst inward and dislodge soil from
instruments. To produce cavitation, an
ultrasonic wave passes through a liquid,
which makes the liquid vibrate.
A hospital sonic cleaner can produce
from 20,000 to 38,000 vibrations per
second. The vibrations are transmitted
through the detergent bath and create
cavitation. With this process, ultrasonic
waves pass through a cleaning solution,
the molecules of the solution are
set in very rapid motion, and small gas
bubbles develop. As the bubbles grow
larger, they become unstable until they
implode inwards (not explode). Creating
a vacuum in the solution draws minute
bits of foreign material (including
microorganisms) from cracks and crevices
such as hinges and serrations on
instruments. This vacuum action results
in the cleaning of hard-to-reach areas.
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For this process to work effectively, the
water must be degassed each time it is
changed in the sonic cleaner. Excess
bubbles in the water are formed during
filling, and these gas bubbles reduce
the energy released during implosion.
The de-gas process involves filling the
sonic cleaner, closing the lid, and running
it for 5 to 10 minutes. Degassing
should only be done after the tank is
filled (not while it is being filled) to avoid
damaging the equipment. Some ultrasonic
cleaners will automatically de-gas
the solution when the chamber is filled.
As a safety precaution, the lid of the
sonic cleaner should be closed at all
times when the unit is operating to prevent
aerosols from being dispersed.
An ultrasonic unit may have one,
two, or three chambers. The first chamber
is for the detergent bath, the second
is for rinsing, and the third is for
drying. Some single-chamber ultrasonic
cleaners may only provide a cleaning
process, whereas other single-chamber
units perform both cleaning and rinsing
functions. There are different types
available, each with specific features
intended for a specific purpose.
Basic ultrasonic washers. This is
the simplest design, consisting of one
or more chambers. Some models have
automated processes consisting of several
phases: filling with water, adding a
cleaning agent, degassing, rinsing, and
draining. Simpler models are completely
manual, with the user performing all the
functions of filling, rinsing, and draining.
Ultrasonic irrigators. This type is
designed to clean minimally invasive
surgical devices with lumens (flushing
the inside of instruments as well as exterior
surfaces). The cavitation process
is used, with the addition of flushing
and irrigation to remove the bioburden
from lumens, channels, box locks, and
other crevices. These types of ultrasonic
cleaners contain water ports with
hoses and special adapters to connect
to various devices such as laparoscopic
and robotic instruments.
Ultrasonic irrigator washers. These
ultrasonically clean external surfaces
and interior lumen channels using rapidflow,
high-pressure irrigation. This equipment
provides programmable wash
cycles.
Ultrasonic irrigator washer disinfectors.
This equipment has programmable,
automated ultrasonic cleaning
processes. It cleans internal lumens
and channels through high-pressure
irrigation, detergent solution washing,
optional lubrication, and thermal disinfection.
The
solution temperatures for cleaning
instruments should be between
80°F and 109°F (27°C and 43°C),
unless otherwise specified by the equipment
or detergent manufacturer. Temperatures
above 140°F (60°C) will coagulate
protein, making it more difficult to
remove. Water should be changed when
it is visually soiled-or at regular intervals-to
prevent soiled particles from
redepositing on instruments. The unit's
tank should be cleaned, and the drain
should be checked for debris at each
water change. The ultrasonic cleaning
process lifts proteins, starches, and
lipids from instruments; therefore, it is
important to routinely clean the tank
according to the manufacturer's instructions.
An ATP test can used to measure
the tank's cleaning effectiveness.
There are different types of sonic
cleaners, and each function requires
verification testing. A cavitation test is
commercially available to test the cavitation
energy, and soil removal verification
tests are also available. For ultrasonic
washers with irrigation capabilities, verification
tests that test for channel irrigation
should be used. If using multiple
channel irrigation ports, each should be
tested to ensure adequate flow.
Cleaning equipment is an essential
step in the processing of medical devices.
For that reason, this equipment
should undergo cleaning verification to
ensure it is functioning appropriately. ✥
Continued on page 31
OR Manager | Nov/Dec 2021
25
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OR Manager November/December 2021

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