What is ANSI/AAMI ST108

Sterile processing, also known as Central Sterile Services or Central Supply, is the department responsible for cleaning, sterilizing, assembling, and packaging medical instruments. This cycle of steps involved in the sterilization of medical instruments, also known as the sterile processing loop, is critical to ensuring surgical instruments, endoscopes, orthopedic tools, suction tubing and cannulas, and similar devices that come in contact with patients are free from harmful microorganisms, thus preventing the risk of infection in patients. 

This crucial process is integral to patient safety, making strict adherence to established standards and guidelines essential within the sterile processing industry. The Association for the Advancement of Medical Instrumentation (AAMI) and the American National Standards Institute (ANSI) collaborated on developing two key standards. AAMI TIR34, a technical information report released in 2014, offers guidelines and best practices for water quality in medical device reprocessing but does not carry legal enforceability. In contrast, ANSI/AAMI ST108: Water for the Processing of Medical Devices, released in 2023, is an enforceable standard that expands upon the guidance of TIR34 to offer a comprehensive approach to water quality in the entire processing cycle of reusable medical devices. 

Why Water Matters in Sterile Processing

Water is the foundation of sterile processing. As the water progresses through the various stages of the sterile processing loop, it is split into three categories.  ANSI/AAMI ST108 lists these categories as – Utility Water, Critical Water, and Steam. The medical device and the disinfection or sterilization process determine each water category’s use. For example, “the processing of stainless-steel surgical instruments that are steam sterilizable has different water quality requirements than the processing of flexible endoscope, which require high-level disinfection or low-temperature sterilization.” To learn more about the specifics of each water category, reference page 17, section 6 – Categories of water quality for medical device processing.  

Facility managers should carefully plan which type of water will be used in their sterile processing loop and when it will be used. An important thing to note is the water quality parameters, which can be found on page 18, table 2 of the standard, are critical to ensuring compliance and maximizing patient safety. This table goes into depth regarding the acceptable level of contaminants allowed in each water category, such as bacteria, endotoxin, chloride, etc.  

Inadequate water quality can lead to adverse effects and leave patients at serious risk for compliance violations. ANSI/AAMI ST108 lists the repercussions of poor water quality as follows:

• Device malfunction during a patient procedure
• Toxic effects and tissue irritation results from residuals on a device or implant that was processed using water of inappropriate quality
• Risk of patient infection resulting from the use of contaminated devices (e.g, surgical site infections)
• Pyrogenic reactions due to the presence of endotoxin; and
• Ineffective cleaning/disinfection due to water contaminants interfering with device processing chemicals

Sterile Processing Loop Water Purification Equipment

To maximize patient safety, sterility of medical devices, and containment of contaminant levels, sterile processing departments implement various types of water purification equipment to achieve compliance. 

Reverse Osmosis

Reverse osmosis (RO) is a water purification process that removes contaminants from water using a semi-permeable membrane. The process involves applying pressure to water, forcing it through the membrane, which only allows water molecules to pass while blocking larger molecules and contaminants.

De-Ionization

Deionization is a chemical process that removes ions, or electrically charged particles, from water to produce pure water. It’s also known as demineralization. De-ionization is a cost-effective water purification method that can be used independently or in combination with other methods. 

Storage Tanks

Storage tanks ensure a continuous, reliable water supply, crucial for cleaning and sterilizing medical devices. They provide a buffer against water supply interruptions and support consistent water temperature and quality, which is essential for effective sterilization. 

Ultraviolet (UV) Disinfection

Ultraviolet disinfection is a non-chemical method to control microbial contamination in water systems. UV light inactivates microorganisms by damaging their DNA, making it an effective tool for achieving the microbial limits specified by ANSI/AAMI ST108.

Endotoxin and Bacteria Ultrafiltration

Endotoxin and bacteria ultrafiltration is a key technique to remove harmful microorganisms and endotoxins. Ideal for multiple applications across the sterile loop, supplementing your process with sub-micron filtration is key to reducing microbial contamination. 

In-Line Infection Control Filtration for Endotoxin Protection

Sterilization alone does not eliminate endotoxins and may, in some cases, increase their presence, especially during the critical water phase of the sterile processing loop. Dedicated endotoxin filtration is highly recommended to address these gaps in traditional water purification processes. 

Nephros in-line infection control filters provide a reliable barrier against bacteria, viruses, and endotoxins for up to 90-days (3 months) or 180 days (6 months). Featuring hollow-fiber technology with a 0.005 pore size – the smallest on the market, our solutions are 510(k)-cleared as Class II filters to aid in infection control and backed by strict testing standards and performance accountability.

Point-of-Use Infection Control Filtration for Rinse Sinks

For immediate bacterial protection at sterile processing rinsing sinks utilizing critical water, Nephros point-of-use infection control filters provide an effective barrier for bacteria for up to 90 days (3 months) and quick and easy installation. Featuring hollow-fiber technology with a 0.1-micron pore size, our solutions are 510k-cleared as Class II filters and offer medical-grade filtration backed by rigorous performance, compliance, and accountability standards.