AAMI ST108: Ensuring Safe Reprocessing through Water Quality

The Association for the Advancement of Medical Instrumentation (AAMI) has established a new standard, ANSI/AAMI ST108:2023, critical for sterile processing departments (SPDs). Replacing the previous AAMI TIR34 guidelines, ST108 emphasizes a stringent approach to water treatment, application, and monitoring for safe and effective reprocessing of medical devices.

Water’s Role in Sterile Processing

Water plays a vital role throughout the medical device reprocessing cycle. It’s used for:

  • Flushing: Removing gross soil and debris from instruments.
  • Washing: Deep cleaning devices using detergents and enzymatic solutions.
  • Rinsing: Removing cleaning chemicals and ensuring a final, contaminant-free surface.

However, unlike tap water, sterile processing demands high-purity water to guarantee device safety. Contaminated water can harbor microorganisms and endotoxins (toxins from gram-negative bacteria) that compromise sterility and potentially cause patient infections.

AAMI ST108: Three Water Categories

ST108 defines three water categories with specific quality requirements:

Utility Water: This is the starting point, typically tap water. Depending on the facility’s source, it may require further treatment to meet the standards for the next two categories.

Critical Water: This highly treated water is used for the final rinse cycle of reprocessed devices or for steam generation in sterilizers. ST108 outlines specific parameters for critical water, including:

    • Low conductivity: Measures the presence of dissolved salts and minerals.
    • Low total organic carbon (TOC): Represents organic contaminants.
    • Low endotoxin levels: Minimizes the risk of bacterial toxins.
    • Microbiological control: Ensures the absence of bacteria.

Several treatment methods can achieve critical water quality, including:

  • Deionization (DI): Removes charged ions like salts.
  • Reverse Osmosis (RO): Removes dissolved salts and organic molecules using a semi-permeable membrane.
  • Ultrafiltration (UF): Removes bacteria and other large molecules.
  • Distillation: Produces the purest form of water by boiling and condensing vapor.
  • Facilities can choose a single method or a combination to achieve the desired critical water quality.

Steam: ST108 also addresses the quality of steam used for sterilization. While generated from critical water, the standard outlines monitoring procedures to ensure it remains free of contaminants.

Water Treatment, Distribution & Storage

ST108 places significant emphasis on the entire water management system within the SPD. Key aspects include:

  • Water Treatment Equipment: The standard requires proper validation and maintenance of all treatment equipment to ensure consistent water quality.
  • Water Distribution & Storage: ST108 outlines guidelines for the distribution piping and storage tanks to minimize contamination risks. Regular inspections and cleaning are crucial.
  • Quality Control Procedures: The standard mandates a comprehensive water quality monitoring program. This includes routine testing for conductivity, TOC, endotoxin levels, and microbiological activity.

AAMI ST108 elevates the importance of water quality in sterile processing. By implementing a robust water treatment system, adhering to distribution and storage protocols, and maintaining a rigorous monitoring program, healthcare facilities can ensure the safety and efficacy of reprocessed medical devices, ultimately protecting patient health.