Immediate Use Steam Sterilization: When Flash Is Justified

Is flash sterilization still allowed? It is the question every new theatre manager asks, and the honest answer is: the word is gone, the practice is not, and the rules around it are much tighter than they were twenty years ago.

“Flash” described an abbreviated steam cycle run in a small sterilizer next to the operating room, often unwrapped, often to cover a shortfall in instrument inventory. Sterile processing bodies dropped the term deliberately. Today the practice is called immediate use steam sterilization (IUSS), and the new name says what it is for: an item that is sterilized and then carried straight to the sterile field for use in the case in progress, not stored and not used later.

This article explains when IUSS is defensible, what cycle and container requirements apply, why implants are a special case, and how a department can cut its IUSS rate by fixing the instrument supply problems that cause it.

From “Flash” to IUSS: What Changed and Why

In the 1990s and early 2000s, flash sterilization was a routine workaround. A surgeon dropped a Debakey forceps, a set arrived short of a needle holder, or a tray turned over too fast between cases, and the item went through a three-minute gravity cycle and back onto the table still hot and wet.

Several problems built up around that habit:

• Items were sterilized without the full cleaning and inspection that a CSSD performs, so bioburden carried over into the cycle.
• Abbreviated cycles were used on items whose manufacturers had never validated them for that cycle.
• Wet, hot items were carried unprotected through corridors.
• Records rarely linked a flashed item to the patient it was used on.

In 2011 a group of professional organisations, including AAMI, AORN, APIC and IAHCSM, issued a joint statement that replaced “flash” with “immediate use” and made one principle explicit: sterilizing an item for immediate use must follow the same cleaning, decontamination and cycle validation steps as terminal sterilization. AAMI ST79, the main US steam sterilization standard, now reflects that position. Hospital accreditors, including the Joint Commission in the US, inspect against it.

The important shift is this. IUSS is not a short cut cycle. Cycle parameters for an IUSS load must be the validated parameters for that item and that configuration, taken from the device’s reprocessing instructions and the sterilizer manufacturer. A department that still uses a single “3 minutes at 132 °C” setting for everything is out of line with current guidance.

When IUSS Is Justified

Guidance from AAMI and AORN agrees that immediate-use cycles should be kept to a minimum and used only when no other option exists. In practice that means a small set of situations:

• A dropped or contaminated instrument with no sterile replacement available in time for the case in progress.
• An unplanned need during surgery, for example an additional instrument the procedure turned out to require.
• A single-instrument, single-patient emergency where the alternative is delaying or abandoning surgery.

Just as important is what does not justify it:

• Not having enough sets to cover the day’s list.
• Saving time on turnover between cases.
• Avoiding the cost of buying duplicate instruments.
• Reprocessing loaner sets that arrived too late for normal processing.

Every one of those is an inventory or scheduling problem. IUSS used to cover them is a sign that the department is under-equipped. Auditors read high IUSS rates exactly that way.

Cycle Types and Parameters

Most theatre sterilizers offer three cycle families that can be used for immediate use: gravity displacement, dynamic air removal (prevacuum), and proprietary “express” cycles. Each removes air from the chamber differently, and air removal is what decides whether steam reaches every surface.

Older textbooks list exposure times such as 3 minutes for non-porous items in a gravity cycle at 132–135 °C, 10 minutes for porous or mixed loads, and 4 minutes in a prevacuum cycle. Treat these as history, not as a setting. The correct exposure time is the one stated in the instrument’s instructions for use (the ISO 17664 reprocessing information) for the cycle and container you are actually using. Where the instrument maker gives no IUSS parameters, the item should not go through an immediate-use cycle.

Every immediate-use cycle has the same three phases: conditioning (air removal and heat-up), exposure at temperature, and exhaust. What most IUSS cycles leave out is a meaningful drying phase. Items come out hot and often wet, which is one reason they cannot be stored.

Containers and Transport to the Sterile Field

The weak point of IUSS has always been the walk from sterilizer to table. An unwrapped tray carried through a corridor is exposed to air and handling, and a wet item contaminates easily.

Current practice is to use rigid sterilization containers that are specifically designed and validated for immediate use, so the item travels closed and is opened at the sterile field by the scrub team. Not every rigid container qualifies. Containers designed for terminal sterilization and storage are validated for different cycles, and their filters and valves may not perform in a short exposure cycle. Check the container manufacturer’s documented IUSS cycles before use. Our comparison of instrument drums and sterilization containers explains how the different systems handle air removal and drying.

The sterilizer should be located close to the point of use, ideally in the theatre suite’s sub-sterile room, so the transfer distance is short and controlled. Staff should wear heat-resistant gloves and transfer the container directly, without setting it down on unclean surfaces.

Implants: Why the Bar Is Higher

Implantable devices such as bone screws, plates and nails should not go through immediate use steam sterilization, except in a documented emergency where no alternative exists. The reasoning is simple. An implant stays in the patient. If a sterilization failure occurs, the consequence is a deep infection around hardware, often requiring removal and revision.

For implant loads in general, guidance calls for a biological indicator together with a Type 5 chemical integrating indicator in a process challenge device, and quarantining the implant until the biological indicator result is available. In an emergency where an implant must be used before that result is known, the release must be documented as an exception, with the reason, the person authorising release, and the patient record linked to that load so it can be traced if the indicator later reads positive.

The real fix for implant IUSS is planning. Implant and instrument sets for orthopaedic cases, including loaner sets brought in by suppliers, should arrive in time for full processing. Our guide to the total knee replacement instrument set shows how much hardware a single arthroplasty tray carries, and why late arrival puts pressure on the sterilizer.

Cleaning Comes First, Every Time

An immediate-use cycle can only sterilize what it can reach. Blood, tissue and bone dust shield microorganisms from steam. That is why the joint 2011 statement insists that items for IUSS receive the same cleaning as items for terminal processing:

1. Point-of-use removal of gross soil, and keeping the item moist so soil does not dry on.
2. Manual or mechanical cleaning with a suitable detergent, including brushing of box joints, serrations and any lumens.
3. Rinsing, preferably with treated water, so detergent and mineral residue are not baked onto the steel.
4. Inspection for remaining soil, cracks and function, especially at hinges.
5. Opening of all ratchets and hinged instruments so steam reaches the joint surfaces.

Cleaning in a scrub sink in the theatre corridor, with whatever brush is to hand, does not meet this standard. If the sub-sterile room has no proper cleaning area, the item belongs in the CSSD. The steps are covered in detail in our CSSD workflow guide and in the enzymatic cleaning guide.

Monitoring and Documentation

An IUSS load is monitored the same way as any other steam load, and the record has to tie it to the patient. A defensible log entry contains:

Physical monitoring (time, temperature, pressure) is checked on the cycle record before the item is released. Chemical indicators go inside each container. Biological indicator testing follows the department’s routine schedule and, for implants, every load. Read more about the indicator classes in our guide to chemical and biological indicators.

How Europe and the UK Approach It

Terminology differs outside the US, but the principle is similar. UK guidance for decontamination in acute care (HTM 01-01) expects surgical instruments to be reprocessed in a controlled sterile services environment and does not support routine reprocessing of instruments in theatres. Small benchtop steam sterilizers are covered by EN 13060, which defines Type B, N and S cycles. A Type N cycle is designed only for solid, unwrapped items, the same limitation as an old gravity flash cycle. Large sterilizers in CSSDs fall under EN 285.

In practice, many European hospitals have removed theatre-side sterilizers altogether. Emergency replacement items come from the CSSD, which keeps backup instruments in single-item sterile packs. That is the model most departments trying to reduce their IUSS rate end up moving toward.

Reducing IUSS: An Inventory Problem in Disguise

When a department reviews its immediate-use log, the same causes tend to come up again and again: one set in high demand, a particular instrument that is often dropped, loaner trays arriving late, and back-to-back cases using the same tray. Each has a supply-side fix.

• Single-wrapped backups for high-drop instruments. Keep peel-pouched spares of the instruments that appear most often in the IUSS log: needle holders, Adson forceps, Kocher clamps, suction tubes. They are cheap compared with the risk.
• Add a set, not a cycle. If one tray is reprocessed between cases every day, buy a duplicate. The cost of a second general or orthopaedic set is usually recovered within months in reduced reprocessing pressure and cancelled cases.
• Loaner deadlines. Contract for loaner sets to arrive at least 24–48 hours before the case, with documentation and IFUs, so they can be processed normally.
• Track the rate. Report IUSS cycles per 100 procedures monthly, by specialty. A rising rate is an early warning of an instrument shortfall.

This is where manufacturer pricing matters. Many hospitals carry too few sets because imported instruments from premium brands make duplicates hard to justify. Sourcing OR-grade instruments direct from an ISO 13485 manufacturer can make full set redundancy affordable, which is the cleanest way to bring immediate-use cycles down. Our article on hospital instrument inventory management sets out how to calculate how many sets a list actually needs, and you can review our quality system on the certifications page.

A Practical IUSS Policy Checklist

1. Define the permitted reasons for immediate use in writing, and exclude inventory shortfalls.
2. Allow only items whose instructions for use give validated immediate-use parameters.
3. Prohibit implants except in documented emergencies with an exception record.
4. Require full cleaning and inspection before every cycle, in an appropriate area.
5. Use only containers validated for the specific IUSS cycle.
6. Place a chemical indicator in every container and verify the cycle record before release.
7. Log every load against the patient, with the reason, and review the log monthly.
8. Run daily air-removal tests on prevacuum sterilizers used for immediate use.
9. Train and competency-assess all staff who operate the sterilizer.

Handled this way, immediate use steam sterilization stays what it should be: a rare, controlled backstop for genuine surprises, not a substitute for having enough instruments.