CST Equipment Sterilization and Maintenance Review (16 Items): Cleaning, Steam Cycles and Indicators

Sixteen scored questions sit on only eight task lines, about two per line, so a typical line in this sub-area can be tested more than once. The public source for most of the rules is CDC's Guideline for Disinfection and Sterilization in Healthcare Facilities (2008), whose web pages carry dates from late 2023. NBSTSA's reference texts and AST's guidelines may go into more detail, and your facility follows manufacturer instructions; Passy doesn't reproduce AST's or AORN's guidelines.

The eight CST task lines behind 16 sterilization questions

NBSTSA's content outline lists these lines under Equipment Sterilization and Maintenance. In the order an instrument travels, they are:

1. Pre-clean instruments using enzymatic cleaner
2. Separate all instruments and put them in a basin with water
3. Take dirty instruments and equipment to Central Supply
4. Decontaminate and clean instruments and equipment
5. Inspect, test and assemble instruments and equipment
6. Interpret and understand chemical and biological indicators
7. Restock leftover supplies and instruments
8. Troubleshoot equipment malfunctions

The first three start in the OR at the end of a case, which is where a scrub's habits show up in questions. Lines 4 to 6 are central processing knowledge the exam still expects you to have.

At the point of use: keep soil from drying on CST instruments

CDC's sterilizing practices page and its cleaning page explain why the first lines matter:

• Cleaning comes first. Items must be cleaned with water and detergents or enzymatic cleaners before processing, because leftover organic and inorganic material acts as a barrier to the sterilant.
• Don't let blood dry. Surgical instruments should be presoaked or rinsed to prevent drying of blood and tissue. Dried or baked-on material makes cleaning harder and sterilization less effective or ineffective.
• Clean as soon as practical. CDC's recommendations say to clean devices as soon as practical after use, for example at the point of use.
• Open and take apart. Items with more than one removable part should be disassembled, and hinged instruments opened, so cleaning solutions and sterilant reach every surface.
• Enzymes aren't disinfectants. CDC says enzymatic cleaners don't disinfect, must be used at the dilution and contact time on the label, and must be rinsed off.

Sharps in a tray need care too. CDC says staff should not reach with gloved hands into trays or containers holding sharps and should use an engineering control such as forceps. OSHA's bloodborne pathogens standard says contaminated reusable sharps may not be stored or processed in a way that requires reaching by hand into their container.

Decontamination, cleaning and inspection in CST questions

• Manual cleaning relies on friction, such as brushing, and fluidics, fluid under pressure to flush channels a brush can't pass through.
• Mechanical cleaning includes ultrasonic cleaners, which remove soil by cavitation, and washer-disinfectors. In a washer, CDC says hinged instruments should be fully open, instruments shouldn't be stacked, and they should be disassembled as much as possible.
• Protective equipment. CDC says decontamination staff should wear household-cleaning-type rubber or plastic gloves, adding masks, eye protection and gowns when exposure to blood or contaminated fluids may occur, as in manual cleaning.
• Inspection. At a minimum, every instrument should be individually inspected and visibly clean. CDC's recommendations add: inspect for breaks in integrity, and repair or discard equipment that can't be properly cleaned and sterilized.

Questions in this group often hinge on order. If an option sterilizes something that hasn't been cleaned and inspected, it's wrong.

Steam sterilization numbers for the CST

CDC's steam sterilization page calls saturated steam under pressure the most widely used and most dependable method, and its recommendations make steam the preferred method for critical items that heat, steam, pressure or moisture won't damage. The figures most worth knowing:

Two more points from the same pages. A gravity sterilizer clears air by letting steam push it out through the drain, and CDC says steam penetration into porous items takes longer because air removal is incomplete; a prevacuum sterilizer pumps the air out first, giving nearly instantaneous penetration even into porous loads. And CDC says steam- or heat-sterilized items should be cooled before they are handled or used in the operative setting. For short daily recall of this subject area, full CST prep at launch includes 84 flashcards for Ancillary Duties.

Reading mechanical, chemical and biological indicators on the CST

"Interpret and understand chemical and biological indicators" is its own task line. CDC says to monitor sterilization with a combination of all three types:

The rules that turn into questions:

• If any indicator suggests a problem, don't use the item. CDC says not to use processed items if mechanical or chemical indicators, internal or external, suggest inadequate processing.
• A failed Bowie-Dick test takes the sterilizer out of use until it's inspected and passes.
• Spore tests run at least weekly, with daily testing helpful for sterilizers used several times a day.
• Every load with implants gets a biological indicator, and implants should be quarantined until the result is negative whenever possible.
• A single positive spore test in a steam sterilizer probably doesn't mean the sterilizer failed if mechanical and chemical indicators were fine. CDC says to repeat the test immediately and, if it stays positive, stop using the sterilizer until it is serviced.

Low-temperature sterilization in CST questions

CDC's recommendations reserve low-temperature methods, such as ethylene oxide (EtO) and hydrogen peroxide gas plasma, for critical items that are heat or moisture sensitive. Two details are classic test material:

• EtO items must be fully aerated before use. CDC's example is PVC tubing, which needs 12 hours at 50°C or 8 hours at 60°C.
• Packaging must suit the method. CDC lists foil, polyvinyl chloride and kitchen-type plastic wrap as unacceptable for EtO, and linens and paper as unacceptable for hydrogen peroxide gas plasma.

Wrapped packs, storage and event-related sterility

CDC's sterilizing practices page covers what happens after the cycle:

• Wet packs are contaminated. CDC says sterile items that become wet are considered contaminated, because moisture carries microorganisms from the air and surfaces. It names heavy metal mass in a set as a cause of wet packs.
• Event-related shelf life. Many hospitals treat a sterile item as sterile until an event contaminates it, such as a tear, wetness or a broken seal. CDC says the chance of contamination rises with handling.
• Check before you open. CDC's recommendations say to evaluate every package for loss of integrity, such as tears, wetness or punctures, and to repack and reprocess any compromised package. A dropped package must be inspected, and one heat-sealed in impervious plastic with the seal intact is considered not contaminated.
• Labels. Sterilized items carry a load number that identifies the sterilizer, the cycle or load, the date and, if used, an expiration date. With time-related storage, an expired pack is reprocessed.
• Storage. CDC describes sterile storage 8 to 10 inches from the floor, 5 inches from the ceiling (18 inches from a sprinkler head) and 2 inches from outside walls, never under sinks or anywhere supplies can get wet. Relative humidity in sterile storage should not exceed 70%.

"Check packages for sterile integrity and expiration indicators" also appears in Preoperative Preparation, so the same rules can cost points in two sub-areas. Ancillary Duties practice is planned with 146 CST questions at launch, covering this sub-area and Administrative and Personnel.

Immediate-use (flash) sterilization on the CST

CDC's flash sterilization page keeps the older term. The 2022 update of SHEA's surgical site infection prevention guidance, written with IDSA, APIC, the American Hospital Association and The Joint Commission, refers to "flash sterilization or immediate-use steam sterilization (IUSS)" and recommends minimizing IUSS. CDC's rules:

• When it's acceptable. For cleaned items that can't be packaged, sterilized and stored before use, or when there isn't time for the packaged method. CDC's recommendations give an inadvertently dropped instrument as an example of an item needed immediately.
• When it isn't. Not for convenience, not as an alternative to buying more instrument sets and not to save time.
• Implants. Not recommended because of the risk of serious infection. If it's unavoidable, records of the load, the patient and the biological indicator result are essential.
• Burns. CDC reports patient burns from hot flashed instruments and suggests air-cooling them or immersing them in a sterile liquid such as saline.

Two original CST-style questions on sterilization

Written by Passy for this guide. They are not NBSTSA items and don't come from any exam or practice test.

Question 1: a wet tray

After a steam cycle and cooling, the CST opens the outer wrap of a heavy orthopedic tray and finds moisture inside. What should happen?

• A. Treat the tray as contaminated and send it back for reprocessing
• B. Let the tray air-dry on the back table, then use it as usual
• C. Use the tray, because its internal chemical indicator changed color
• D. Blot the instruments dry with a sterile towel and pass them up

Keyed answer: A. CDC says sterile items that become wet are considered contaminated and that a compromised package is repacked and reprocessed before use. B and D try to fix contamination by drying. C is wrong because a chemical indicator shows exposure to the process, not sterility, and wetness makes the tray contaminated regardless.

Question 2: the end of the case

At the end of a case, which action by the CST best fits CDC's guidance for instruments going to decontamination?

• A. Keep them moist and send them for cleaning as soon as possible
• B. Let them dry on the back table so they are lighter to carry
• C. Close and lock the ring-handled instruments to protect the tips
• D. Leave them in the room until the last case of the day has ended

Keyed answer: A. CDC says instruments should be presoaked or rinsed to prevent drying of blood and tissue and cleaned as soon as practical after use. B lets soil dry, C keeps hinged surfaces closed when CDC says to open them, and D delays cleaning.

Your next step for CST sterilization questions

Draw the path an instrument takes from the back table to the sterile storage shelf, and write the task line and one CDC rule at each step. Then test yourself with the five mixed questions in the CST practice test guide, which include a Bowie-Dick item, and see where this sub-area sits among the eight in the CST content outline guide. When full prep launches, planned explanations for each CST answer cite the sterilization rules behind it.