Advanced Instrument Processing Solutions

First, I recommend you review our blog answers under the “hard water category.” That being said, it has been my experience that most institutions use tap water in their washer-disinfector, all the way up to the final thermal rinse. If the facility has the ability, they will use either de-ionized or reverse osmosis water in this final thermal rinse. Depending on where you live and the time of year, your tap water can contain a lot of dissolved minerals which can end up depositing on your instruments and in your machine’s wash chamber, eventually damaging both. An acid rinse will neutralize these minerals and keep them from forming deposits.

Now, there are certain instruments that cannot be exposed to an acid rinse (such as plated copper instruments); however, these instruments would not fare well in an alkaline wash either. Always check the manufacturer’s recommendations and instructions for cleaning.

The majority of the instruments you run through your washer are surgical grade stainless steel. These instruments have a layer of passivation that helps protect them from corrosive substances. This layer is not added to them, like a layer of electro-plating. Instead, passivation is formed by dipping the instruments in an acid bath which removes the Nickel and Iron from the top part of the instrument surface. The metal that remains is Chromium, which reacts with the acid to form Chromium Oxide–the passivation layer. This layer is very tough and protects the instrument from corrosion, but this layer is also very thin and can be easily damaged. Once this layer is damaged, corrosive substances can make their way to the steel below. It is, however, possible to reinforce this layer of passivation, and one of the means is to expose these instruments to an acid rinse in the wash cycle.

So to answer your question, the acid rinse will not harm your surgical instruments. In fact, it will strengthen and keep them free from corrosive deposits at the same time. Furthermore, the acid rinse will also keep your washer disinfector chamber free of deposit formations.

I truly understand the constraints of working in an ambulatory surgery center (ASC) and know you are trying to do the best thing by keeping the instruments moist to facilitate their cleaning the next day; however, I would recommend not leaving the instruments immersed in liquid all night. Instead, you should pretreat them with an enzyme gel/foam, or at least rinse them in sterile water, and then place the instruments in a plastic bag until the next morning.

Soaking instruments overnight, or for prolonged periods of time, encourages the formation of biofilm. These colonies of microbes adhere to surfaces by producing sticky, slimy protective films (polysaccharides). Not only does this layer make it difficult to remove these colonies, but it also protects the bacteria within it from the effects of disinfectants. Needless to say, enzymatic detergents have little or no effect on them. As these bacteria communities grow, they become more difficult to remove and more resistant to disinfectants (and even sterilization). It can take as little as 30 seconds for these microbes to attach to an instrument surface, and a little as a few hours for a mass of biofilm to mature.

Although tap water is chlorinated to reduce the replication of bacteria , biofilms are often found attached to the pipes of water delivery systems, and they are the source of these microbes in drinking water. Incidentally, DI and RO systems are even more prone to biofilms because the chlorination is removed from this water.

In my opinion, the best water to use in your final Thermal rinse would be De-Ionized (DI) or Reverse Osmosis (RO) water (I would actually have to say that these two treated waters are best for your whole wash cycle and not just the thermal rinse). DI and RO waters are both lacking in charged inorganic particles; this inorganic material is the main cause of deposits on your instruments. Deposits of calcium, magnesium, chlorides, etc. from tap water not only harm your instruments, but will also end up on the chamber walls, rotary spray arms and heating elements of your washer-disinfector, hampering its performance. Using water that is free of these inorganics, especially in the final thermal rinse, will help prevent these deposits from forming.

If tap water is the main source of water in the rest of the wash cycle, deposits can be alleviated by adding an acid rinse to a rinse cycle just before the final thermal rinse. deconex 25 Organacid™, a low dosing, phosphate and surfactant free, organic acid rinse additive, is a perfect choice for this. Originally formulated as a neutralizing rinse for use after an alkaline wash cycle, deconex 25 Organacid™ used in the rinse cycle will safely keep inorganics from depositing on your surgical instrumentation and washer-disinfector. Used regularly, it will also reduce and eliminate the need to “de-scale” your washer-disinfector.

Hard water deposits are very bad for both your instruments and your washer disinfector machine (WD).

The deposits on instruments make them more susceptible to corrosion (especially fretting corrosion in the box-lock), damaging the instruments and providing “hiding spaces” for organic soil and micro-organisms. Deposits in your WD eventually impede the machine’s performance by blocking water flow in the washer arms.

Softening your water only exchanges the calcium in your water for sodium. Although this will lessen deposits on your instruments, I recommend that your resources are better spent in getting a water deionization (DI) system.

DI water is void of both positive and negative ions (although it will still contain uncharged matter). This lack of charged matter makes the water hypotonic (water is a universal solvent and being stripped of its charged materials, it becomes aggressive), making it a better cleaning agent. In fact, you would need less detergent in your WD if you used DI water.

Water deionization is more expensive than water softening. Due to this fact (and the general lack of understanding of water and cleaning chemistries), many institutions with DI (or reverse osmosis water–which is even purer) only use DI water in their final thermal rinse cycle. This is to eliminate hard water deposits from the rest of the tap water cleaning process.

I would also suggest if you have a cleaning cycle that employs the use of tap water in all cycles up to the final thermal rinse, you should incorporate an acid rinse in the initial rinse cycle. This will help eliminate any inorganic deposits that may form on your instruments prior to the rinse cycle.

25 ORGANACID™ is just such an acid rinse. A very low dose in your initial post wash rinse will not only neutralize water hardness and prevent it from depositing on your instruments and WD chamber, but will also help remove existing deposits.