The Cost of Dried-On Soil
Every reprocessing failure has a starting point, and in many cases, it is the moment soil is allowed to dry. By the time a tray reaches the decontamination sink, the condition it arrives in has already decided how much time, effort, and risk the department is about to absorb. When blood, tissue, and other organic material harden on an instrument, the cost does not disappear. It moves downstream and lands squarely on sterile processing.
Point-of-use treatment is the first cleaning step in the reprocessing cycle, and it is also the most cost-effective place to prevent problems. ANSI/AAMI ST79 is direct about why it matters: blood, bodily fluids, and saline are corrosive, and if left to dry, they can be difficult to remove and can prevent sterilization.1 That single line captures a cost most departments pay every day without naming it. It is worth breaking that cost into its four parts:
The cost is measured in soak time
Dried soil does not clean at the same speed as fresh soil. It has to be softened before it can be removed, which means the clock starts at the sink. ST79 calls for instruments to be pre-soaked as soon as possible after point-of-use cleaning with a product intended to loosen soil, because pre-soaking moistens and loosens the soil, making the cleaning step more effective and efficient.2 The reverse is also true. When soil arrives already hardened, the pre-soak is no longer a head start. It is remediation.
The problem grows with enzymatic chemistries. AORN notes that when organic material has dried, an enzymatic cleaner cannot act on it directly. The dried material has to be re-hydrated before the enzymes can work.3 A step meant to speed cleaning becomes a waiting period instead. Multiply that delay across a shift, and a preventable condition quietly consumes capacity the department cannot spare.
The cost is measured in difficulty
Softening dried soil is one problem. Removing it is another. ST91 states plainly that when allowed to dry, soils become more difficult to remove, and that failure to promptly initiate cleaning can increase the difficulty of cleaning and decrease the effectiveness of disinfection and sterilization.4 The difficulty is not only added effort; it is a direct threat to the outcome the department works to guarantee.
Dried soil is also where biofilm begins. Once bacteria adhere and build their protective matrix, ordinary cleaning no longer reaches them. ST79 describes biofilm as tightly adhered material that cannot be removed easily, and warns that once it forms, direct friction or oxidizing chemicals are needed to remove it.5 This is not a distant risk. AORN reports that biofilm can begin to form within minutes after a procedure is completed.3 The window to prevent it closes at the point of use, not at the sink.
Independent laboratory work supports the point. An FDA study evaluating cleaning methods against organisms known to adhere to surfaces found that allowing bioburden to dry made cleaning very difficult, and concluded that microorganisms, protein, and cells should not be
allowed to dry on a device before cleaning.6 The consequences are not theoretical either: AORN documents a reported outbreak in which pre-cleaning of a flexible endoscope was delayed for 24 hours, allowing organic material to dry on the device, with organisms later transmitted to multiple patients.3
The cost is measured in double work
When soil is not removed on the first attempt, someone repeats the attempt. Encrusted material forces the more aggressive cleaning that ST79 specifically flags as a source of instrument damage, pointing to the vigorous cleaning processes needed to remove encrusted material.7 Trays that fail inspection are re-cleaned. Devices that cannot be verified as clean are returned, reprocessed again, or pulled from service. Every one of those loops is work the department already did once.
There is a longer bill as well. The same corrosive fluids that resist removal also pit and degrade instruments when left to dry.1 ST79 frames point-of-use soil removal as a way to minimize corrosion risk and damage, and notes that prompt handling might extend the life of the instrument.7 Dried soil, then, is not only a today problem. It shortens the service life of the inventory a department depends on, turning a skipped two-minute step into replacement cost down the line.
The cost is measured in trust
Here is the part that sets dried soil apart from most reprocessing challenges: the department that pays for it is usually not the one that caused it. Point-of-use treatment happens where the procedure happens. ST91 defines it as the activities the user performs immediately after patient use, including pre-cleaning to prevent biofilm formation and drying of soil.8 When that step is rushed or skipped in the procedure room, sterile processing inherits a harder job through no fault of its own.
That imbalance is where accountability frays. ST79 asks sterile processing and clinical personnel to collaborate so that instruments are kept as free of gross soil as possible during the procedure.9 ST91 builds the handshake into the workflow, requiring hand-off communication that documents when point-of-use treatment was completed.10 These are not bureaucratic details. They are the mechanism by which two departments hold a shared standard, and they only work when both sides treat point-of-use care as a real responsibility rather than an optional courtesy.
The encouraging part is that this cost is the most preventable one on the list. A moistened towel, a quick flush, a pre-treatment product applied before the cart leaves the room: the interventions are small, and the standards describe them plainly. Cart rating and quality-assurance feedback give the department an honest way to show the operating room what arrives and what it costs, turning a source of friction into a conversation grounded in evidence rather than blame.
The least expensive place to solve it
Dried-on soil looks like a small thing in the moment. It is a smear left to harden, a flush not performed, a cart moved a little too quickly. But the cost is real, and it is paid in soak time, in cleaning difficulty, in duplicated work, and in the trust between the two teams responsible for patient safety. The least expensive place to solve any of it is the same place it starts: the point of use.
Works Cited
1. Association for the Advancement of Medical Instrumentation. ANSI/AAMI ST79:2017, Comprehensive Guide to Steam Sterilization and Sterility Assurance in Health Care Facilities. Section 6.3.1, Handling of instruments during surgical procedure.
2. ANSI/AAMI ST79:2017. Section 7.5.1, Presoaking.
3. Association of periOperative Registered Nurses. Guideline for Processing Flexible Endoscopes. In Guidelines for Perioperative Practice. Section 3, Point-of-Use Treatment. Available at aornguidelines.org.
4. Association for the Advancement of Medical Instrumentation. ANSI/AAMI ST91:2021, Flexible and Semi-Rigid Endoscope Processing in Health Care Facilities. Section 7.1, Cleaning.
5. ANSI/AAMI ST79:2017. Section 6.3.1, Note on biofilm.
6. Merritt K, Hitchins VM, Brown SA. Safety and cleaning of medical materials and devices. J Biomed Mater Res. 2000;53(2):131-136. PubMed 10713558.
7. ANSI/AAMI ST79:2017. Section 6.3.2, Removal of gross soil.
8. ANSI/AAMI ST91:2021. Terms and definitions, point of use treatment.
9. ANSI/AAMI ST79:2017. Section 7.4.1, General considerations for all devices and utensils.
10. ANSI/AAMI ST91:2021. Section 7.2, Point of use treatment (hand-off communication).