This article presents the position of Lawrence F Muscarella, PhD, on the use of “immediate-use steam sterilization” (IUSS), historically known as “flash sterilization,” to process surgical instruments in or near an operating room setting.

“Flash sterilization, “flashing,” or “immediate-use steam sterilization”

Also known as “flashing” or “flash sterilization,” immediate-use steam sterilization — or, IUSS — is a rapid, steam sterilization process historically intended exclusively for “emergency situations.”[1-11]

Re-sterilizing for immediate use a previously cleaned and sterilized instrument that inadvertently dropped on the operating room floor after being unwrapped and about to be introduced into the sterile field is an example of such an emergency situations.[1-4,10]

Flash sterilization’s definition

According to the Centers for Disease Control and Prevention (click here), flash sterilization is a modified conventional steam sterilization process (either gravity, pre-vacuum, or steam-flush pressure-pulse) that rapidly re-sterilizes a potentially contaminated item in an open tray or a specially designed, covered, rigid container.[10]

The manufacturer-based Association for the Advancement of Medical Instrumentation (AAMI) (click here) similarly describes flash sterilization as the exposure of unwrapped medical instruments to a quicker, abbreviated steam sterilization cycle for their immediate use, not for storage at a later time.[11]

Traditional terminal sterilization

IUSS is performed in or near an operating room, to reduce the potential for the instrument’s re-contamination during its transfer from the steam sterilizer (or, autoclave) to the sterile field.

IUSS may therefore be referred to as a “point-of-use” sterilization process.

In contrast, traditional “terminal sterilization” not only is a more thorough and controlled sterilization process that sterilizes cleaned and wrapped (or otherwise packaged) surgical instruments, but it also is performed in a sterile processing and distribution area, or a central supply department, by trained (and sometimes certified) reprocessing and sterilization personnel.

Packaged in a wrap or rigid sterilization container, these surgical instruments may then be stored “sterile” for later use (e.g., several days later).

Whereas IUSS is limited to pressurized steam, terminal sterilization of wrapped instruments is not, but may also be achieved using, for example, ethylene oxide (EtO) gas or hydrogen peroxide plasma.

A shifting paradigm due to latitude and convenience?

Arguably because of both its abbreviated cycle time and convenient point-of-use paradigm, IUSS has morphed from an infrequently utilized, exceptional practice into, at times and for some healthcare settings, an all-but-standard replacement for terminal sterilization.

In fact, today, IUSS may be routinely used (or, as some might argue, misused) to process many different types of surgical instruments, no longer necessarily being reserved only for emergency situations.(4,5,10,12)

Primarily because of financial considerations and convenience, not quality enhancements or controls, the popularity of immediate-use steam sterilization (IUSS) has grown in many medical fields, including orthopedic surgery and ophthalmology. — Lawrence F Muscarella, PhD

The time savings and convenience associated with flash sterilizing a potentially re-contaminated surgical instrument in the sub-sterile area or the operating room itself can be significant.

And, with shorter cycle times typically comes lower costs.

Whereas a traditional steam sterilization cycle may require as many as 30 minutes at 121 degrees C to process pre-washed, wrapped instruments followed by the time required for the instruments’ drying and cooling, IUSS may require as few as 3 minutes at 134 degrees C, with no drying time.

Quality and Safety Services for Hospitals, Manufacturers, Patients:  Click here to read about Dr. Muscarella’s quality and safety services committed to reducing the risk of healthcare-associated infections, including CRE outbreaks linked to contaminated endoscopes and other reusable medical equipment.

To flash or not to flash?

For better or worse, a healthcare facility’s decision whether to flash sterilize surgical instruments may be reduced to adoption of one of the following two policies:

  • the contraindication of its routine (but not emergency) use, with additional instruments sets being purchased to meet patient demand and accommodate the longer cycle times associated with traditional, terminal (steam) sterilization performed in a more remote central supply department; or
  • the more routine use of IUSS in or near the operating room to permit faster turn-around times for surgical instruments, to increase patient throughput, and to avoid the purchase of more surgical instrument sets, which can be expensive, increasing revenues while saving money.

What does the CDC say?

The Centers for Disease Control and Prevention (CDC) might sanction the latter policy, stating in its 2008 guideline on disinfection and sterilization (click here) that:[10]

  • “Correctly performed flash sterilization is an effective process for the sterilization of critical medical devices”; and
  • “Flash sterilization is considered acceptable for processing cleaned patient-care items that cannot be packaged, sterilized, and stored before use.”

Appearing possibly to convey a mixed signal, however, the CDC also states in this same guideline that (at least for “implantable” devices), flash sterilization is associated with “the potential for serious infections.”[11]

More specifically, the CDC writes that: “Because of the potential for serious infections, flash sterilization is not recommended for implantable devices (i.e., devices placed into a surgically or naturally formed cavity of the human body).”

AAMI’s stance

Whereas in the past flash sterilization was reserved exclusively for emergency situations encountered in an operating room setting, the Association for the Advancement of Medical Instrumentation (AAMI) would disagree, placing few restrictions today on the use of IUSS.[11]

AAMI’s position on IUSS can be read by clicking here.

And, AAMI is not alone. According to AAMI, its position has been adopted, too, by the Accreditation Association for Ambulatory Health Care, Association of Perioperative Registered Nurses (AORN), and the Association for Professionals in Infection Control and Epidemiology (APIC), among others.[11]

[Note: These organizations adopted the term immediate-use steam sterilization, not only because “flashing” may have become an antiquated term, but also, possibly, to assuage concerns that — right or wrong — “flashing” is an abbreviated cycle with inherent risks not associated with traditional terminal sterilization.]

Relegating traditional sterilization, not IUSS, more to the role of the exception for processing some types of instruments in some instances, only in certain circumstances does AAMI (and the organizations that endorse its position statement) contraindicate flashing.

For example, AAMI recommends IUSS not be used to process:[11]

  • implants (except in a documented emergency situation when no other option is available; the CDC agrees[10]);
  • surgical instruments that may have been used on patients known or suspected of being infected with Creutzfeldt–Jakob disease (CJD) or a similar brain disorder; and
  • surgical instruments sold as “sterile” and intended for single-use only.

AAMI also recommends that IUSS not be used to process surgical instruments (or loads) that have not been validated for this type of abbreviated cycle.[11] *

* Note: Refer to the instrument’s reprocessing instructions for specific warnings and contraindications regarding IUSS. As an example, one manufacturer’s reprocessing instructions — in this case, Intuitive Surgical’s “Cleaning, disinfection, and sterilization information for reusable instruments, accessories and endoscopes used with da Vinci, da Vinci S and da Vinci Si Systems” (click here) — writes:

“Warning: The use of ‘flash’ sterilization is not recommended.”

No organization recommends IUSS

IUSS’s increasing use raises a number of questions, if potential concerns:

— Is healthcare quality, if not patient safety, being compromised for the sake of convenience, ease, time and money?

— And, if as the CDC acknowledges the IUSS of implantable devices is associated with “the potential for serious infections,” might there not be concern, too, about the risk of infection associated with the flash sterilization of other types of critical instruments, not merely implants?[11]

As AAMI acknowledges, flash sterilized instruments are exposed to “air and other environmental contaminants” prior to their use, manifestly posing an increase risk of contamination of the instruments during their handling and prior to their use and, therefore, patient infection.

Whereas some organizations may no longer contraindicate IUSS’s routine use, none unconditionally recommends that it be used in lieu of or to replace traditional terminal sterilization, in part because the IUSS is a less controlled practice, is inherently prone to a narrower margin for error, and requires the unwrapped instrument’s “immediate use.”

Some more limitations of IUSS

In addition:

  • not only to the increased potential for the flashed instrument’s re-contamination with potentially pathogenic microorganisms during handling (remembering that, to permit IUSS’s more rapid cycle, flashed instruments are not covered with a protective wrapping to maintain their sterility prior to their clinical use),
  • but also to its contraindication of flashing for surgical implants,

the CDC acknowledges that IUSS has some other important limitations that could compromise healthcare quality, if not also patient safety.[11]

These additional shortcomings — which historically have provided a sound rationale for healthcare organizations to reserve its exclusive use for emergency situations — include IUSS’s lack of timely results yielded by biological indicators (BI).

BIs are used to monitor a steam sterilization process’s effectiveness and verify that the processed instruments were sterilized to within a defined sterility assurance level, or SAL (e.g., a SAL of 10^-6).[11,12]

No drying cycle

Further, although it exposes the instrument to wet steam under pressure, IUSS features no or minimal drying time following the sterilization cycle.

Therefore, unlike cleaned instruments processed by a traditional terminal sterilization process, flashed instruments, which are hot and unwrapped, not only have not been first washed or typically inspected, but also are typically wet (with steam condensate or water) when transported to the sterile field, posing an increased risk of re-contamination and healthcare-associated infection.(10)

As Dr. Muscarella advised in the journal Chest (click here), the clinical use of wet surgical instruments poses an increased risk of disease transmission.[13,14]

The use of wet surgical instruments are associated with an inherently increased risk of bacterial infections, with documented morbidity and mortality. Any sterilization process that increases this likelihood would be concerning. — Lawrence F Muscarella, PhD

Whether shifting the use of IUSS from a rare, reserved process to a more commonplace one has adversely affected quality and patient safety, however, remains possible and is supported by some data.(1-9)

The ‘abuse’ of intermediate-use steam sterilization (IUSS) (i.e., its use during ‘non-emergent’ circumstances) has the potential to increase risk for development of (surgical-site infections), increased health care costs, and even direct thermal injury to the patient. — Zuckerman et al. (2012) (See reference No. 15)

With shortcuts can come risks

Like with several other aspects of medicine, potential risks may accompany certain types of shortcuts and conveniences, and flash sterilization may be no exception — the CDC’s and AAMI’s respective stances vis-a-vis IUSS’s use notwithstanding.

Although it is certainly bactericidal, flash sterilization requires close monitoring and is associated with an inherently narrower margin of safety compared to traditional steam sterilization.

For some types of surgeries, positive predictors for the usage of IUSS include the day of the week (e.g., Monday), patient obesity, a high case (or surgical) volume, and the specific operating room in which the procedure was performed (operating room No. X), whereas negative predictors for IUSS’s usage include performing surgery in the morning.(15)

Although its methodology has some limitations, one study found a statistically significant higher incidence of healthcare-associated infection (HAI) associated with flash sterilization.(1)

Questioning flash sterilization’s quality

In addition to those noted by the CDC, above, IUSS is also associated with several additional potential shortcomings that may call into doubt the quality of care it provides.

These limitations include that:

  • wet, unwrapped flashed instruments may be used more frequently during one time of the day (e.g., morning) than dry, wrapped instruments processed by a traditional steam sterilizer, raising additional concerns about whether flashing introduces two different standards of patient care; and
  • the documentation* and records associated with flashed instruments—unlike instruments processed using traditional steam sterilization cycles—are often incomplete, preventing adequate tracking of flashed instruments. Flashing may also encourage the preoperative administration of prophylactic antibiotics.(1)

[* Note: Documentation — for example, the instrument’s or load’s identification, the patient’s name or comparable identifier, and both the biological and chemical indicator’s respective result — recording the use of flash sterilization, consistent with manufacturers’ instructions and the medical facility’s written policies and procedures (e.g., the flash sterilization of an implantable device), is essential for, among other reasons, quality and epidemiological tracking.[17]]

Whatever the healthcare facility’s usage of IUSS (e.g., often, rarely), quality standards require that it be documented and consistent with the facility’s written policies and procedures.

Namely, a healthcare facility’s policies and procedures indicating the rare use of IUSS contrasted with the results of an independent review, survey or audit confirming instead IUSS’s common use violates quality principles and could most certainly have adverse accreditation implications.

The Affordable Care Act

These limitations are particularly salient considering the growing national trend toward increased quality, the improvement of patient safety, the prevention of healthcare-associated infections (“HAIs”), and, to be sure, the emergence of “superbugs” and other antibiotic-resistant bacteria.

As part of the Affordable Care Act of 2010, Medicare payments to hospitals may be reduced if patient care is lacking. These reductions are intended to incentivize hospitals financially to improve quality — a clinical outcome that is measured, in part, by patient re-admissions for care within a month of their discharge.

Instrument damage

Moreover, some manufacturers of surgical instruments (and implants) contraindicate flash sterilization.(16)

Such factors as a physically small operating room and one in close proximity to the steam autoclave may increase IUSS’s usage.(12,15)

The rapid heating and cooling of its rapid, high-temperature cycle can cause chipping, flaking, and other types of damage to some types of surgical instruments.[17]

Such damage can result in costly repairs and an increased risk of bacterial transmissions.

Whether flash sterilization might be damaging ophthalmic instruments causing pieces of the instrument’s surface to be introduced into the eye during cataract surgery, increasing the risk for toxic anterior segment syndrome (TASS), is unclear.

Click here to read Dr. Muscarella’s article “Association of Toxic Anterior Segment Syndrome (TASS) with Ophthalmic Instrument Sterilization,” which discusses instrument reprocessing and flash sterilization as a risk factor for TASS.

Data from the ophthalmic and orthopedic surgical settings

In part due often to limited, lacking, or voluntary post-surgical surveillance validating the associated incidence of infection, data showing a lack of infection associated with a specific practice or procedure does not confirm or prove its safety.

Click here to read Dr. Muscarella’s article “Tap water used for irrigation during gastrointestinal endoscopy: A recommendation and assessment of the infection risk.

That said, some studies have suggested that IUSS does not necessarily pose an increased risk of infection following some types of surgical procedures, although the safety of IUSS depends on many factors, including the healthcare setting and the type of surgical instrument.[12,15]

Focusing on post-operative infections following ophthalmic surgery, Carpel et al. (2012) divided approximately 40,000 ophthalmic surgical patients into one of two groups (with approximately 19,000 patients in each group).[12]  This discussion is continued in Box A, below.

And, a report by Lopansri et al. (2010 —click here) concluded that flash sterilization was the cause of a protracted outbreak of post-arthroscopy surgical site infections, adding that:[18]

Flash sterilization is not an appropriate method for routine sterilization. — Bert Lopansri, MD

According to Lopansri et al. (2010), the rate of surgical site infections following arthroscopy returned to “baseline” once flash sterilization was discontinued and all arthroscopes were cleaned and sterilized in the hospital’s central processing department.[18]

Semantics: The definition of “immediate use”

In addition to a number of other questions, concerns, and confusion that arise with the IUSS of surgical instruments, there is IUSS’s requirement that, as its name indicates, the processed instrument be used “immediately.”

In the context of using IUSS, AAMI defines “immediate use” as “the shortest possible time” between the removal of the processed surgical instrument from the sterilizer and its (aseptic) transfer to the sterile field.[11]

While this definition is intended to require the instrument’s prompt transfer and clinical use on the order of a few seconds, it also permits some potentially problematic latitude, discretion, variability, and confusion.

First, “prompt” for one practitioner may be “delayed” for another.

All that AAMI’s definition seemingly prohibits is that the instrument be “stored” prior to its use. And what defines “storage” may, too, be subject to some discretion and interpretation.

In fact, AAMI’s aforementioned position statement defines “immediacy,” not according to a specific time frame (as would be expected), but rather as a term that is established “through the critical analysis and expert collaboration of the health care team” (click here).[11]

Second, it could be debated that failure to restrict the use of IUSS exclusively to emergency situations (as defined by the healthcare facility in its policies and procedures manual — Note: A list of such situations is provided in Table 2 of this article’s reference No. 15, below) can confuse the practitioner about the importance of quality, standardization, and aseptic technique.

And, third, the more routine use of IUSS (AAMI’s position and the stance of Carpel et al. [2012] — see: Box A — notwithstanding[11,12]) contradicts the cautious recommendations of others, including Zuckerman et al (2012), who recently wrote that:[15]

“Intra-operative contamination is the only acceptable reason” to employ the use of immediate-use steam sterilization.

Whether IUSS may be favored because the diagnosis and treatment of post-operative infections is often less expensive and saves money, compared to a medical facility purchasing additional expensive instrument sets to accommodate high case volumes as required of traditional terminal sterilization has been suggested.(14)

The Centers for Medicare & Medicaid Services (CMS)

No matter the CDC’s or AAMI’s respective stance,[10,11] this article by Dr. Muscarella endorses Zukerman et al.’s (2012) position[15], contraindicating the routine use of IUSS, thereby reserving the abbreviated process of flashing only for those circumstances that have been historically termed and remain “emergency situations” (see above).

The Centers for Medicare & Medicaid Services (CMS) would seemingly agree with this stance, stating with circumspection, in 2009 (click here), that as a condition for participation:[17]

“Sterilization of unwrapped/uncontained loads should not be routine practice in (ambulatory surgical centers) but should be used only for an urgent and unpredicted need for a specific device (e.g., when an instrument is dropped). Routine sterilization of unwrapped/uncontained loads continues to be inappropriate and should be cited as a violation of 42 CFR 416.51(a).”

(For hospitals, CMS applies 42 CFR 482.42(a) as a condition for participation or coverage, writing that: “The hospital must provide a sanitary environment to avoid sources and transmission of infections and communicable diseases. There must be an active program for the prevention, control, and investigation of infections and communicable diseases.”)

Update: In a memorandum, dated August 29, 2014, CMS writes that the term “flash” sterilization is “now considered outmoded,” replacing it, like other organizations, with the term immediate use steam sterilization.

In this same memorandum, which can be read by clicking here, CMS emphasizes not only that “practices associated with the outmoded term ‘flash’ sterilization have been implicated in surgical site infections and are considered to pose an increased risk of complications …,” but also that “IUSS also entails an increased risk of inadvertent contamination during transfer to the sterile field and damage to the instruments, as well as risks related to wet instruments and the potential for burns,” adding that:[19]

Therefore use of IUSS, even when all steps are performed properly, should be limited to situations in which there is an urgent need and insufficient time to process an instrument by using terminal sterilization.

Position statement

The position statements of the CDC, AAMI, Carpel al al. (2012) and others notwithstanding, Dr. Muscarella recommends, in agreement with the Zuckerman et al. (2012)[15], the CMS[17], and Lopansri et al. (2010), that the IUSS of patient-care items be reserved for emergency situations — not for the purpose of convenience, reducing the inventory of instruments required to meet patient demand, and/or to save money.

Indeed, compliance with this recommendation will likely require a healthcare facility to purchase additional instrument sets to ensure an adequate inventory of instruments, to accommodate the longer reprocessing times associated with traditional terminal steam sterilization processes.[18]

But, doing so will establish:

  • one safe standard of patient care;
  • enhance quality and safety;
  • minimize potential legal exposure in the event of a bacterial outbreak linked to surgical procedures; and
  • demonstrate that reducing costs to the potential detriment of patient safety is not prudent.


1. AORN. Toxic Anterior Segment Syndrome. Clinical Issues. AORN J 2006 Nov;84(5):841-4.

2. Leonard Y, Speroni K, Atherton, et al. Evaluating use of flash sterilization in the OR with regard to postoperative infections. AORN J 2006 Mar;83(3):672-80.

3. Provincial infectious diseases advisory committee (PIDAC). Best practices for cleaning, disinfection, and sterilization in all healthcare settings. April, 2006.

4. Alfa M. System 1 Steris Processing System: Liquid Chemical Sterilization Anthology. Marketing Brochure. March 4, 2004.

5. Hancock C. Sterilization in a flash. Not a quick fix, flash sterilization requires discipline to be effective. Infection Control Today May 2001.

6. Cause of eye disease never found at Montreal hospital. CBC News November 30, 2006.

7. Dalton M. Experts’ advice on preventing future TASS outbreaks. Eyeworld 2007;12(2):18.

8. Guttman C. Retrospective study links use of short-cycle sterilization to TASS. Ophthalmology Times Mar 15, 2006.

9. Schraag J. To Flash or Not to Flash? That’s the Question for Many Healthcare Workers. Infection Control Today.

10. Centers for Disease Control and Prevention (CDC). Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008. (Click here)

11. Association for the Advancement of Medical Instrumentation (AAMI). Position paper: Immediate-Use Steam Sterilization (click here).

12. Carpel EF, Mancera AD, Rowan LL. et al. Full-cycle steam sterilization in ophthalmic surgery: The effect of wrapping instruments. Am J Ophthalmol 2012 Mar;153(3):405-11.

13. Muscarella LF,. The importance of bronchoscope reprocessing guidelines: Raising the standard of care. Chest 2004 Sep;126(3):1001-2; author reply 1002-3.

14. Muscarella LF. Inconsistencies in endoscope-reprocessing and infection-control guidelines: the importance of endoscope drying. Am J Gastroenterol 2006 Sep;101(9):2147-54.

15. Zuckerman SL, Parikh R, Moore DC, et al. An evaluation of immediate-use steam sterilization practices in adult knee and hip arthroplasty procedures. Am J Infect Control 2012 Nov;40(9):866-71.

16. Plus Orthopedics. Important information on the handling and care of instruments from Plus Orthopedics AG. Brochure

17. Centers for Medicare & Medicaid Services (CMS). Flash sterilization Clarification – FY 2010 ambulatory surgical center (ASC) surveys.  Reference: S&C-09-55. September 4, 2009. (Revised October 9, 2009).

18. Lopansri B, et al. Protracted Outbreak of Postarthroscopy Infections Associated with Flash Sterilization of Instruments. in: Program and abstracts of the Fifth Decennial International Conference on Healthcare-Associated Infections. Atlanta: Society for Healthcare Epidemiology of America, 2010. Abstract 400.

19. Centers for Medicare & Medicaid Services (CMS). Memorandum. Reference: S&C: 14-44-hospital/CAH/ASC. August 29, 2014.

Box A. Data from the ophthalmic surgical setting.

In part due often to limited, lacking, or voluntary post-surgical infection surveillance, data showing a lack of infection associated with a specific practice does not confirm or prove its safety.

That said, some studies have suggested that IUSS does not necessarily pose an increased risk of infection following some types of surgical procedures, although the safety of IUSS depends on many factors, including the healthcare setting and the type of surgical instrument.[12]

Focusing on post-operative infections following ophthalmic surgery, Carpel et al. (2012) dividing approximately 40,000 ophthalmic surgical patients into one of two groups (with appropriately 19,000 patients in each group)[12]:

  • patients in the first group on whom were used unwrapped surgical instruments processed via IUSS (performed adjacent to the operating room); and
  • patients in the second group on whom were used wrapped surgical instruments processed in a central facility via “full-cycle steam sterilization.”

Carpel et al. (2012) report that the incidence of presumed post-operative infections (group 1; n=17) associated with unwrapped instruments processed via IUSS (performed adjacent to the operating room) was higher than, but not statistically different from, that (group 2; n=9 presumed infections) associated with wrapped instruments processed in a central facility via “full-cycle steam sterilization.”[12]

Carpel et al. (2012) add that if certain measures are taken, such as carefully cleaning ophthalmic surgical instruments prior to sterilization, terminal sterilization and IUSS can be used interchangeably.[12]

According to these authors, their findings corroborate the current position of The Joint Commission, and American Academy of Ophthalmology (AAO), and American Society of Cataract and Refractive Surgery (ASCRS).[12]

As acknowledged by Carpel et al. (2012), however, the extent to which topical, sub-conjunctival, or intra-cameral antibiotics were used during the treatment of these almost 40,000 patients and might have masked or “hidden” infections, causing the infection rate of either group, particularly the first group, to be under-calculated, was not evaluated and is a possibility.[12]

Article by: Lawrence F Muscarella, PhD, posted on 1/16/2013; updated 8/18/2014, Rev A.

Leave a Reply

Your email address will not be published. Required fields are marked *