“I recently attended a seminar where the speaker discussed cleaning solutions. They talked about “surface tension,” of cleaning solutions, and I had not heard of that term before. Can you explain why it is important?”A:
I need to start with a simple concept. No matter the type of cleaning solution you are using, cleaning takes a lot of energy. Cleaning requires both friction and fluid to get anything clean.
There are three different kinds of energy needed for cleaning:
- Chemical energy: provided by the cleaning solution.
- Mechanical energy: provided by a machine or by hand.
- Thermal energy: provided by heating water.
Surface tension falls under chemical energy because it is part of the cleaning solution. When I think of surface tension, I think of a drop of water (what I call “beads up”) on my kitchen counter. The drop will hold its shape and will not spread. As tension is reduced, the “bead” will spread out reaching more of the kitchen countertop surface.
Thus, when you clean, you want your cleaning solution’s surface tension reduced. In other words, less is more with surface tension. To do this, cleaning solutions’ companies use a group of chemicals called surface active agents or surfactants, which change how water behaves. When added, the surface tension is reduced, and water can spread out and wet the surface (like the kitchen countertop example) better than using just plain water.
This simple principle applies to cleaning anything; so, when cleaning your medical devices, you want a cleaning solution having surfactants that lower the surface tension.
It should be noted that some cleaning solutions are specifically formulated for use in an ultrasonic cleaner. Cleaning solutions that reduce surface tension within the bath/tank will increase cavitation intensity and enhance cleaning. Make sure you read the label to ensure it can be used in an ultrasonic.
We also understand that cleaning solutions are formulated with more than just surfactants. You also can have any combination of the following additives: a) builders, b) solvents, c) enzymes, d) preservatives, e) pH adjusters, f) fragrances, and g) dyes. These are just some of what can be added to cleaning solutions. Various combinations of these and other ingredients create all the unique cleaning solutions you can pick from to use in your department.
Comparing the many types of cleaning solutions that a medical device reprocessing department can use can be both difficult and confusing. As I pointed out in my insights article in HPN’s September 2021 publication, ASTM has published standards that I feel users should ask for when comparing or changing cleaning chemistries. It is objective testing methods that should help differentiate the various cleaning solution products.
As in the movie Indiana Jones and the Last Crusade (Spielberg, 1989), Indy needed to “… choose wisely,” the right chalice to obtain life, so you also need to “choose wisely” the cleaning solution to get those medical devices clean.
“I was informed we need to use a multi-enzyme cleaning solution with our washer because it is on contract. Is that true?”A:
As with any cleaning solution, you want to pick the right one for the task at hand. Although I cannot address the issue with your contract situation, my hope is that there was a committee made up of a variety of professionals who have a good understanding of cleaning solutions when they chose this multi-enzyme cleaning solution.
When it comes to enzymes, they are produced by living organisms; however, they are not living substances. Enzymes act as a catalyst to speed up chemical reactions. They are highly specialized proteins classified by the type of reaction they catalyze. Medical device reprocessing departments basically use these three types of enzymes (or any combination of them):
- Lipase - breaks down fats and greases.
- Protease - breaks down protein.
- Amylase - reaks down carbohydrates and starches.
Lastly, I think we all can agree that blood is probably the number one soil we try to clean off medical devices. Whatever solution you use, you want to make sure it is a proteolytic type of cleaning solution, which means it can break down protein by means of proteolysis. “Proteolysis is a hydrolysis reaction of peptide bonds in which proteins breakdown into smaller peptides and/or into individual amino acid residues. The proteolytic cleavage reactions are usually catalyzed by either chemicals or enzymes.” (Raju, 2019).
Cleaning solution companies have their own proprietary formulas, and some combine enzymes and some do not use any enzymes. Again, depending on your process, you need to “choose wisely,” which cleaning solution with/without enzymes works best in your department to make sure it gets your medical devices clean.