IS YOUR WATER WORKING
FOR YOU???
WHY IS WATER SO IMPORTANT IN A MEDICAL
DEVICE REPROCESSING DEPARTMENT?
• Used for pre-cleaning instruments at POU
• Used in manual cleaning, rinsing
• Used in ultrasonics, pasteurmatics, washer
disinfectors
• Converted to steam for sterilizers
IMPORTANCE TO INSTRUMENTS
• An instrument inventory is a significant
expense to any facility & not easily replaced
• Metal instruments are made of a high grade of
stainless steel but can be damaged during
reprocessing not only by improper handling,
but also by poor water quality
• Instruments need to be properly reprocessed in
order to maintain functionality, sharpness,
etc...
IMPORTANCE TO INSTRUMENTS
• Corrosion of instruments can cause instruments to
break (stress cracks), scissors to become dull, loss
of integrity of instrument surface (holes, rust)
• Cracks or corrosion spots can harbour microorganisms, debris and therefore interfere with the
effectiveness of sterilization
• Stains, water spots, mottled finishes cause end
user to believe the instrument is not clean and
therefore ‘suspect’ the sterility of the instrument
bundle (instruments look dirty)
WHY DO STAINLESS STEEL INSTRUMENTS
CORRODE?????
• Surgical instruments have a ‘passive’ layer of
chromium and iron oxide
• This ‘passive’ layer is what protects the
instrument from corrosion
• The more chromium in the ‘passive’ layer, the
more resistant the instrument is to corrosion
• ‘Passive’ layer can be damaged by: handling,
acidic/alkaline detergents, dried soil/blood,
saline, chlorine, hard water deposits, etc.... ¹
POSSIBLE WATER –BASED CAUSES
• Rust and pitting – usually caused by chlorides in water,
rust in pipes to washer/sterilizer, boiler carry-over
• Rainbow colours on instruments – possible cause is
excessive silicates in water (by-product of sand) or
dissimilar metals in contact during reprocessing
• Spotting (light/dark)– minerals in water; seen when
instruments dry and water evaporates leaving water
spots
• Black/brown – low pH, exposure to chlorine
• Black – possible exposure to ammonia
• Powdery residue on aluminum – low pH water (acidic)
• Etched aluminum – high pH solution (alkaline)
Silicate staining
Pitting due to chlorides
Rust or stain?
Improperly cleaned; pitted; rust
Low pH or Ammonia
Rust caused by saline
BUT WE USE GREAT CITY WATER!
“Water that is safe to drink may not be acceptable for reprocessing or for
sterilizing surgical devices....”²
“Most public water systems include additives such as chlorine, dissolved salts and
sometimes significant naturally occurring mineral content, and even organic
contaminants, bacteria and endotoxins.”²
“Tap water is contaminated with toxic heavy metals, synthetic organic chemicals,
chlorine, biological parasites and thousands of other harmful contaminants.
According to a research group, ‘EPA reports show that U.S. water supplies
contain over 2300 cancer causing chemicals’. In addition, all the chemicals we
use will ultimately show up in our tap water. There is no new water; our planet
keeps recycling the same water. Furthermore, water treatment facilities are not
designed to remove organic chemicals and toxic heavy metals, like lead.”²
“Stainless instruments are susceptible to pitting when there is an increase in
chloride content in the water, when there is an increase in temperature, with
decreasing pH values, increased exposure times, insufficient drying and
concentration of chloride from dry residues to instrument surfaces after
evaporation.”²
PRINCIPLES OF WATER USE
• Water, by itself, does not clean instruments
• Water, with enzymatics and detergents clean
instruments (explain how water works)
• Water compatible substances can be fairly
easily dissolved by water, but other substances
cannot; these ‘other’ substances include fats,
oils and proteins – which we find every day on
surgical instruments in the form of blood, fat,
body fluids, tissue, etc...
•
.
The first washer phase is done with warm (not
hot) tap water and injections of enzymatic, so
blood and proteins are not ‘set’, but rather the
break down begins.
• The wash phase with tap water and detergent,
causes the debris to be loosened and dispersed
into the water. The water volume and presence of
detergent holds the debris in ‘suspension’, so it
does not re-settle on instrument surfaces.
• The rinse phase is done with hot water. The rinse
water should be purified water so all debris,
chemicals, minerals, etc rinse away cleanly from
instrument surfaces. SO, WHY NOT TAP
WATER???
THIS IS WHERE IT GETS A BIT (MORE)
TECHNICAL!!!
• Reverse osmosis (RO) water, de-ionized (DI)
water or distilled water all remove the
impurities that would normally cause damage
to and deposits on instruments
• Generally is used only for the rinse cycle due
to system capacities, necessity and cost
• Each has their own advantages and
disadvantages, but all hold a distinct advantage
over tap water for ‘final rinse’ water
DISTILLED WATER
• Is the least likely method to produce pure
water for an MDRD
• Water is boiled in a distiller. The impurities
are ‘heavy’ and stay in the boiling water while
the lighter steam rises and is drawn off. The
steam is then allowed to condense back into a
nearly pure water form for use.
• Is not practical when large volumes are needed
as it requires a large amount of energy to
produce, therefore significantly increased costs
and considerable infrastructure
R.O. WATER
• Water is passes through pre-filters, then is
forced through pores of a semi-permeable
membrane into a collection tank
• Pore size is approx. 0.0005 micron (bacteria
are generally 0.2-1 micron & viruses 0.02-0.4
micron)
• Very effective in removing most minerals,
metals, micro-organisms
• Membranes vary in quality, pore size; are
sensitive to damage by chlorine, metal ions
• Membranes can be self-cleaning to a degree
R.O. WATER ISSUES
• Membranes become plugged or contaminated,
requiring changing; pre-filters require changing
• Water temperature and pressure need to be
maintained according to manufacturer’s specs to
maintain system efficiency
• Water used to wash across the face of the
membrane for cleaning, is wasted – flows down
the drain
• Water purity begins to decline almost
immediately due to buildup of contamination on
membrane - needs to be monitored for regular
maintenance of filters, membrane changes
D.I. WATER – a little chemistry first
• “When diluted in water, minerals usually are
split up ions, which are charged particles. The
split up results in positively charged ions: the
cations... mainly hydrogen and metal ions (K,
Na, Ca, Fe,etc) and negatively charged ions,
the anions. Anions are usually left overs of
acids and salts.”³
The above statement is the principle that DI
water is founded upon.
D.I. Water
• Water is passed through carbon filters, reverse
osmosis, then through 2 resin tanks. The first
tank contains cation resin which removes the
positive ions and replaces them with hydrogen
ions, while the second tank contains anion resin
which removes the negative ions and replaces
them with hydroxyls. When the hydrogen and
hydroxyl ions combine, they form pure water. 3,4
• Water purity is measured by the ‘resistance value’
in Meg-Ohm cm (won’t conduct electricity)
D.I. WATER ISSUES
• A meter is attached to the DI system for daily/weekly
readings, as the water quality can change quickly once
the resin tanks become depleted.
• The drop in resistivity from a starting point of 17-18
Meg Ohms does not occur gradually, but rather
exponentially. Once the resistivity drops below a
certain point, the tanks are no longer replacing the
removed ions, so the water becomes ‘hungry’ and
attracts ions from other sources (ie: the piping, the
washers, the washer racks, instruments, containers, etc)
• DI systems do not remove organic contaminants or
micro-organisms because these do not have a positive
or negative ion charge
D.I. WATER
• Our experience:
>We noticed the instruments appeared dull (we had our
chemistries checked by vendor)
>We noticed dark staining in jaws and box locks, then
over entire surfaces (we had chemistries checked again
by vendor, and had maintenance do water quality tests)
>Aluminum trays began to dry with a fine powder on
them (we had maintenance check DI water system and
biomed check RO water system)
>Metal pitting started on older instruments and copious
amount of powder on aluminum trays started (brought
water for independent water analysis) and discovered
what the issue was and how to fix
REFERENCES
1
2
3
4
- Spotting, Staining, and Corrosion of Surgical Instruments; H.J. Kaiser PhD/ P.
Schwab MBA/ J.F. Tirey MA; Copyright 2012 Virgo Publishing; Posted in Infection
Control Today 10/01/2000
- Water Filter Comparisons. Ralph Nadar Research Group; Copyright 2012 Virgo
Publishing; Posted on Infection Control Today 04/29/2009
- DI Water; DI Water Specifications. TM Associates. Santa Clara CA.
- DI (Deionized) Water – Part 1: System Overview. Digital Matrix. Copyright 2012.