Immediate Use Steam Sterilization, or IUSS, is an accelerated method of steam sterilizing surgical instruments when they are needed right away and cannot go through the standard, longer sterilization cycle. It was previously called “flash sterilization,” a term still widely recognized in healthcare settings. The key distinction is that instruments processed through IUSS are not stored or saved for later. They go straight from the sterilizer to the sterile field during an ongoing surgical procedure.
How IUSS Differs From Standard Sterilization
In a typical hospital sterile processing department, instruments are cleaned, inspected, wrapped or placed in containers, and run through a full steam sterilization cycle. A gravity-displacement sterilizer, for example, requires 15 minutes of exposure at 270°F (132°C) for wrapped instruments, followed by 15 to 30 minutes of drying time. A prevacuum sterilizer can cut the exposure down to about 4 minutes at the same temperature, but still needs 20 to 30 minutes for drying. After all that, the wrapped instruments can be stored until they’re needed.
IUSS shortens this timeline considerably. Because the instruments aren’t wrapped in the traditional sense and are used immediately after the cycle finishes, there is no extended drying phase. The tradeoff is that the instrument has no protective packaging and must be transported directly to the patient in an aseptic manner, with zero delay. It cannot sit on a shelf, be held between cases, or be set aside for a future procedure.
When IUSS Is Considered Appropriate
Both the Joint Commission and the Centers for Medicare and Medicaid Services are clear: IUSS is not meant for routine use. It exists for genuinely urgent situations. The Joint Commission identifies three common scenarios where it may be appropriate:
- Emergency procedures requiring a specific instrument that isn’t available through standard processing
- Contaminated instruments that are irreplaceable and must be returned to the sterile field immediately, such as when a critical tool is the only one available
- Dropped instruments needed to continue a surgery already in progress
Using IUSS simply because a facility doesn’t own enough instruments to cover its surgical schedule, or because it’s faster and more convenient, is considered a deficient practice. CMS requires that any facility found using IUSS routinely be cited as a violation of federal infection control regulations.
What Cannot Be Processed Through IUSS
Certain items are explicitly off-limits for IUSS. Implantable devices, such as joint replacements or plates and screws used in orthopedic surgery, must not be processed this way. The risk of a failed sterilization cycle with a device that will remain permanently inside a patient’s body is too high. Single-use devices sold as sterile are also excluded, as are any instruments that haven’t been validated for the specific IUSS cycle being used. Additionally, instruments used on patients suspected of having Creutzfeldt-Jakob disease or similar prion disorders require specialized decontamination that IUSS cannot provide.
Loaner trays, the instrument sets that vendors ship to hospitals for specific surgeries, present their own challenge. The Joint Commission expects facilities to have agreements with vendors requiring that these trays arrive far enough in advance to go through full reprocessing rather than being rushed through IUSS at the last minute.
The Infection Risk
A study published in Antimicrobial Stewardship & Healthcare Epidemiology analyzed nearly 24,000 surgical procedures and found that IUSS was associated with a 1.52 times higher risk of surgical site infection compared to standard reprocessing. Among procedures where instruments went through IUSS, 2.6% resulted in surgical site infections, compared to 1.7% for standard processing. That difference may sound small in percentage terms, but across thousands of surgeries it translates to a meaningful number of preventable infections.
The risk wasn’t uniform across all specialties. Transplant surgery saw a 2.47 times higher infection risk after IUSS, and plastic surgery procedures showed a 3.64 times higher risk. These findings reinforce why regulatory bodies treat routine IUSS use as a serious compliance issue rather than a minor shortcut.
Steps Required Before and During IUSS
IUSS is not simply a faster version of throwing instruments into a sterilizer. Every step of standard reprocessing still applies before the cycle begins. The instrument must be thoroughly cleaned and decontaminated at the point of use, inspected for visible soil or damage, and placed into a container or tray validated for IUSS. Skipping the cleaning step and relying on steam alone to handle organic material like blood or tissue is a recipe for sterilization failure, because debris can shield microorganisms from the steam.
Once cleaned, the instrument goes into the sterilizer using cycle settings that match the manufacturer’s instructions for the device, the container, and the sterilizer itself. When the cycle finishes, the item must be transferred immediately and aseptically to the sterile field. “Immediately” means the shortest possible time between the sterilizer door opening and the instrument reaching the surgical team. There is no acceptable window to set it down, carry it through a hallway, or hold it for another case.
Monitoring and Quality Control
Standard biological indicators designed for full sterilization cycles don’t reliably monitor IUSS cycles. Facilities must use biological indicators specifically validated for IUSS. According to the ANSI/AAMI ST79 standard, these biological indicators should be run at least weekly, though daily use whenever the sterilizer operates is preferred. Each IUSS cycle should also include a Type 5 or Type 6 chemical indicator strip placed inside a containment device, run in an otherwise empty chamber.
Mechanical monitors built into the sterilizer, such as temperature and pressure gauges, provide a first layer of verification. But no single monitoring method is sufficient on its own. The combination of mechanical readouts, chemical indicators, and biological indicators creates a system of checks that can catch failures a single method might miss.
Documentation Requirements
Every IUSS cycle must be logged with enough detail to trace the instrument back to the patient. A typical IUSS log includes the date and time, the sterilizer number, what instrument was processed, the reason IUSS was used instead of standard reprocessing, patient identification, the signature of the person who verified the cycle, and an attestation from the operating surgeon for emergent procedures. These records are maintained for seven years, giving infection control teams the ability to investigate any complications that surface long after the surgery.
This documentation serves a dual purpose. It creates accountability for each individual cycle, and it allows facility leadership and surveyors to track whether IUSS is being used at appropriate frequencies or creeping toward routine reliance.
Why Facilities Are Pushed to Minimize IUSS
The push to reduce IUSS use comes down to a combination of infection risk, regulatory pressure, and the reality that most IUSS situations are preventable with better planning. Having adequate instrument inventory, scheduling sufficient turnover time between cases, and ensuring loaner trays arrive early enough for full processing all reduce the need for IUSS. The AAMI standard governing steam sterilization, ST79, is currently undergoing a revision process that aims to harmonize with newer standards and reflect changes in technology and best practices since its last update.
For surgical patients, the practical takeaway is straightforward: instruments used during your procedure should ideally go through a full sterilization cycle with proper wrapping, drying, and storage. IUSS exists as a safety valve for genuine emergencies, not as a workaround for scheduling pressure or insufficient equipment.