Selecting a Detergent for Sterile Processing

You’ve all probably made a decision on a new detergent from time to time. The point of this article is to help you cover the key questions in making that decision. The point of this exercise is to see if there is a noticeable difference in performance or behavior from your current detergent. So, what are the key questions?

• Does it clean and does it make a noticeable difference in cleaning outcomes?
• Does it rinse off?
• Is it compatible with the items we normally clean?
• Is it compatible with our dosing system?
• Does the manufacturer provide the information needed to set the dose for the detergent?
• Is it available without supply chain issues?
• Does it save our facility money, or if it doesn’t, is it worth the extra cost?

If you use cleaning indicators, they should be spotless when taken out of the washer. The same should be the case when using the new detergent after its dosing is adjusted (see below). If you have the opportunity to test against a harder cleaning challenge, that challenge should be as clean or cleaner than it was using the old detergent.

This analysis should include testing for residual protein if there is protein in the indicator, since you can’t see many residual proteins that are in patient soil, although they may still be there. A number of manufacturers make protein detection tests, and these can be very useful in measuring the amount of protein remaining on the instrument. Adenosine triphosphate (ATP) is an alternative cleaning marker but it can degrade more easily than protein in the cleaning process and so give false negative results.

Protein will denature in the thermal disinfection phase of the washer/disinfector process. You should interrupt the cycle after the final rinse, before the thermal disinfection phase, to get the protein indicators out for testing to avoid false negatives. If you were running a real load, wear gloves since the instruments weren’t disinfected. After this, the instruments that were left in the washer should be run in a no-detergent, thermal disinfection cycle to disinfect.

For acceptance criteria, the FDA accepts 6.4 µg/cm² residual protein on an instrument. The UK’s Department of Health accepts 5 µg residual protein per side of an instrument, no matter how large the instrument is. That’s a big difference, but also shows how well processing can be done. Of course, you have to remember that enzymes are proteins, too, and they must be removed at the end of the phase in which they are used. If not, you may get false positive results for residual protein. It’s not just the detergent, it’s the cycle, too, that leads to good cleaning results. This was the point of my last article in this series.

One way to test for residual detergent is to look at the washer window to see how much detergent is in the final rinse before the cycle advances to the thermal disinfection phase. If it is soapy, the detergent hasn’t been removed by your washer’s cycle and will be baked on during the thermal disinfection phase. This leads to greying of the instruments over time, a cosmetic issue, but a down check in an accreditation audit nonetheless. This is a qualitative measure, and you should take pictures to compare the old and new detergent.

Another way to check for residual detergent is to interrupt the cycle after the final rinse and before the disinfection phase, or in an ultrasonic cleaner, after the rinse cycle. In the same way as protein testing was done, wearing gloves, remove instruments to be tested, preferably those with a lot of surface area. If you are sure that your critical water is really, really compliant with the requirements of AAMI ST108, immerse a portion of the test instrument in the smallest amount of critical water that will cover it and agitate. If any changes occur in the appearance of the water, i.e., a film on top, some suds, etc., the detergent didn’t rinse clean. This may point to the need for an additional post-cleaning rinse if the results are no different than the old detergent.

You can find examples of outrageously good cleaning results in the literature, but sometimes those are achieved by using high-alkaline detergents. These work brilliantly but may destroy items made of aluminum.

Other considerations are the point of use of the instruments on the patient. Some parts of the body are less able to tolerate the residual chemistry of detergents than others. The obvious example is the purported relationship between toxic anterior segment syndrome (TASS) and enzyme detergents. There may be others. Do not be afraid to ask your detergent provider for proof of the applicability of the detergent system to the loads you process, especially if there is some specialty focus in your processing.

If the detergent is ultraconcentrated, and your dosing system is designed for conventional concentrations of detergents, you will have to get a modification made to your dosing system, adding cost to the changeover and making going back more difficult. This is also true going in the other direction—if you are using an ultraconcentrated detergent and changing to a less concentrated one.

Typically, detergent doses should be set in accord with the quality of the water used in the cleaning process. One metric for this is conductivity/total dissolved solids (TDS). If the conductivity/TDS is low, you need less detergent to be dosed to give you adequate cleaning performance. If the conductivity/TDS is high, you need more. Some manufacturers can advise you on this. Some do not.

If you switch to a detergent and can’t get it when it is time to order more, where does that leave you? You need to be sure that you won’t get into that situation.

Total cost is more than the number of cycles run x cost per dose. It also should take into account the success of the processing, and conversely, the lack of rework needed.

Another measure of cost is the time it takes to run the cycle. If a new detergent is so efficacious or flexible in application that you can shorten your processing time, you gain a few minutes per cycle. This can be in a wash phase, in a temperature transition as the cycle proceeds (if you don’t need to use as high a temperature for second wash phase, you have saved time), or if it rinses better than the previous detergent, you can cut down the rinse times.

The decision to change detergents can result in improved processing and save time and rework. But it should not be a decision taken by the seat of the pants or based on a single parameter. You can and should prove that the new detergent provides better overall results and productivity using a scientific approach as laid out above. Your detergent vendor should be able to help you with some of these items, and they will if they want to earn your business!

This is a team effort between the manufacturer and the sterile processing department (SPD). If the new detergent does a better job cleaning, you can win on many fronts, and your patients will be more likely to have good outcomes from cleaner, residue-free instruments.

Author: Jonathan Wilder, PhD, Featured, Sterile Processing