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Table Top Sterilizers - Processing Instruments - Protecting Patients - Ensuring Safety

Introduction

According to the Centers for Disease Control and Prevention (CDC) medical devices that have contact with sterile body tissues or fluids are considered critical items. Critical items must be properly sterilized in order to prevent microbial contamination, which can result in disease transmission. Steam sterilization, moist heat in the form of saturated steam under pressure is the most widely used and most dependable method of sterilization for critical items. Portable (table top) steam sterilizers used in outpatient, dental and rural clinics are designed to sterilize small instruments used in the practices, such as hypodermic syringes and needles, and surgical instruments.

Manufacturers' Operating Manual

Practices should obtain and reference the manufacturers' operating manual to ensure that staff are operating the sterilizers appropriately. Several older models feature a built-in metal instruction sheet (retractable) located beneath the compartment door. Contact the manufacturer to obtain an operating and maintenance manual if yours is not available. The internet is helpful in locating a manufacturer and/or a manual.

Policies and Procedures

Written procedures to guide staff members through the instrument processing cycle should include:

  • Operating instructions.
  • Cleaning instruments prior to sterilization.
  • Proper packaging of instruments.
  • Maintenance schedule.
  • Recordkeeping requirements.
  • Identification of occupational hazards.

Staff Training and Competency Assessments

A comprehensive staff competency program is necessary to ensure consistent sterilization practices. Staff members need to understand the "steam-under-pressure" principle to prepare and process items to ensure that sterility occurs. Staff competencies must be achieved and documented in preparing and packaging the instruments, loading the sterilizer, monitoring the sterilizing process, and documenting the features of each cycle.

Sterilizing Practices

Sterilizer Qualification Testing

In order to verify the sterilization process, table top sterilizers should be tested with a biological indicator process challenge device (BI PCD) when installed, relocated, redesigned, after a major repair and after a sterilization failure has occurred. The verification/qualification testing should be done with a fully loaded sterilizer using material representative of what will be regularly processed. Because there is no universally accepted standardized PCD for table top sterilizers, the BI PCD should represent the same type of package or tray that would be considered the most difficult to sterilize and which is typical of the items routinely processed. Table 1 lists the appropriate BI PCDs for sterilizer modes or cycles that contain instruments in peel pouches, unwrapped instruments and wrapped packs.

Table 1: BI PCD for Qualification and Routine Sterilizer Efficacy Testing of Table Top Sterilizers

Program/LoadTemperatureTime*BI PCD (Challenge or Test Pack)
Unwrapped instruments on a tray or glassware270° F - 274° F
(132° C - 135°C)
≥ 3 min.BI in unwrapped instrument tray or glassware
Wrapped trays of instruments, instruments in peel pouches270° F - 274° F
(132° C - 135° C)
≥ 5 minBI in a wrapped tray or peel pouch and include porous items if applicable
Packs, wrapped250° F
(121° C)
≥ 30 minBI in wrapped pack that is representative of the load, include porous items if applicable
Liquids250° F
(121° C)
≥ 15 minBI suspended above a test container of the liquid

*Check with the medical device or sterilizer manufacturer for correct time for the items being processed (Young).

A biological indicator which consists of geobacillus stearothermophilus spores should be placed in the BI PCD, in a place that is most challenging for the sterilizer to penetrate. The BI PCD should be placed in the sterilizer in an area the manufacturer has designated as the coldest area. Three consecutive full cycles, one after another, with the BI PCD, should be run according to the manufacturer's instructions. The chemical indicator (CI) should be removed and the results recorded after each cycle. The BI should be removed from the PCD and incubated according to the manufacturer's instructions. To verify this process you must have a control BI with the same lot number as the test BI. The control BI should show growth after proper incubation. The rest of the load should be quarantined until the BI results are known.

Sterilizers with a dynamic-air-removal feature require three Bowie-Dick test cycles run in an empty sterilizer to show acceptable air removal results. Results from each of the three test cycles must be documented.

Physical Facilities

The reprocessing area should have a workflow pattern such that devices clearly flow from high contamination areas to clean/sterile areas. There should be a clear separation between soiled and clean workspaces.

If it is not possible to physically separate the decontamination area from the clean work area, procedural barrier separations could be adequate (but not generally desirable). In these situations:

  • Staff should work to prevent splashing, production of aerosols and contamination of the clean items and work space

Ventilation and air-handling systems should move air from the clean side of room to the decontamination side.

Cleaning Medical Devices

Items must be cleaned using detergent or enzymatic cleaners and water prior to being processed. Cleaning reduces the amount of contaminates and removes foreign material that can interfere with the sterilization process.

Personnel should wear rubber or plastic gloves when handling or cleaning contaminated items. Personal protective equipment (PPE), such as face masks, eye protection, and gowns, should be worn when exposure to blood and other contaminates might occur.

Packaging Instruments

After items have been cleaned, dried and inspected they should be wrapped or placed in rigid containers and placed in the instrument trays or baskets according to guidelines provided by the Association for the Advancement of Medical Instrumentation (AAMI) and other professional associations. Hinged instruments should be opened; items with removable parts should be disassembled as appropriate; complex instruments should be prepared according to the manufacturer's instructions; devices with concave surfaces should be positioned to allow for water to drain; and heavy items should be positioned so they cannot damage delicate items. (CDC-Guideline for Disinfection and Sterilization in Healthcare Facilities)

Choices of material for packaging items include rigid containers, peel pouches, roll stock or reels, and sterilization wraps. The packaging material should permit air removal from the packaging, allow for free circulation with steam penetration, and protect contents from puncturing the packaging material. Wrap items in a manner that avoids tenting and gapping.

Select Correct Cycle Time and Drying Time

Review the medical device manufacturer (MDM) instructions for reprocessing instruments. If the MDM cycle time is longer than the cycle recommended by the sterilizer manufacturer, follow the MDM instructions.

Loading the Sterilizer

All items to be sterilized should be arranged to permit adequate air removal, to allow steam to circulate, and to penetrate each surface of an instrument. Avoid overloading the chamber because an air pocket may form that hinders steam penetration.

Consult with textile and metal/plastic container manufacturers and the sterilizer manufacturer for instructions on pack preparation and density parameters.

Listed below are basic principles for loading sterilizers:

  • Allow for proper sterilant circulation.
  • Perforated trays should be placed so the tray is parallel to the shelf.
  • Non-perforated containers should be placed on their edge (e.g., basins).
  • Small items should be loosely placed in wire baskets.
  • Peel pouches should be placed on edge in perforated or mesh bottom racks or baskets.

(CDC-Guideline for Disinfection and Sterilization in Healthcare Facilities)

Drying Feature

Relative humidity, packaging materials, and loading techniques may affect drying. Packages must be thoroughly cooled (eliminating all steam vapor and away from direct air currents) before being handled or removed from the chamber. The usual technique is to open the door about ½ inch and run the drying cycle if it is available, typically with the door open for a minimum of ten minutes. Not all table top sterilizers have drying cycles. In these cases, drying may be accomplished manually by following the manufacturer's instructions.

Storage and Sterility

Sterility of a package may be either time-related or event-related. Event-related shelf-life practice considers a package sterile until some event causes the item to become contaminated, such as a tear in the packaging, a seal broken, or the packaging becomes wet.

To prevent damage to the packaging and contamination of sterile items, use closed cabinets or drawers to protect seldom used items. Although open shelving may be used, ventilation considerations, traffic flow, and repetitive handling of items should be evaluated. The length of time an item is considered sterile depends on factors such as: the number of times an item is handled, the packaging material used, whether storage is on open shelves, cabinets, or drawers, and the method of sealing (tape, heat sealer, or self-sealing pouches). Items should be handled using aseptic techniques in order to prevent contamination.

Outside shipping containers and web-edged corrugated cardboard boxes should not be used in a sterile storage area. These boxes can collect dust, debris and insects during shipping.

Monitoring

After the device has successfully completed qualification testing it can be put into use and a schedule should be set up to routinely monitor the process using a combination of physical/mechanical, chemical and biological indicators. Table top sterilizers with a dynamic-air-removal feature should run a Bowie-Dick test pack each morning, to evaluate the efficacy of air removal and steam penetration before the sterilizer is used.

Physical/Mechanical Monitoring

Physical/mechanical monitors include the daily assessment of cycle time and temperature by examining the temperature record chart or computer printout and an assessment of pressure via the pressure gauge. These assessments must be checked at the beginning of each cycle. The operator should verify the information and mark the printout at the end of the cycle. The printout should be saved as part of the recordkeeping. Sterilizers that do not have recording devices should not be used. After each cycle, pressure readings, duration of achieved cycle temperature (beginning and ending time of a cycle), should be recorded in a log and initialed by the processor.

Chemical Indicators

Chemical indicators (CI) indicate if an item has been exposed to the sterilization process. Chemical indicators applied to the outside of a pack indicate that the pack has been processed through a sterilization cycle, but it does not prove that sterilization has been accomplished. Chemical indicators should also be placed inside of the package to verify sterilant penetration. Review medical device manufacturer instructions for information on where to place the CI in the package, tray or container, which is least accessible to steam penetration. (Young)

Internal Chemical Indicators (Pack Control)

Internal chemical indicators (CIs) are used to monitor the conditions inside individual packs to determine sterilant penetration to the medical device. The CI should be placed in each package, tray or rigid container to be sterilized. It should be placed in an area that is least accessible to steam penetration. Check with the manufacturer of the medical device to determine where to place the CI so that it is least accessible to steam penetration. There are several types of chemical indicators available; however, a Class 4 multi-variable indicator or a Class 5 integrating indicator should be used.

Staff should be trained to interpret the results of each internal chemical indicator. If the internal chemical indicator has not reached the appropriate end point, the package should not be used.

External Chemical Indicators (Exposure Control)

External chemical indicators are used to differentiate between processed and unprocessed items. They do not indicate whether or not sterilization has been achieved. External chemical indicators should be placed on the outside of a package unless the internal chemical indicator is visible; for example, with peel pouches or open trays. External chemical indicators would be Class 1 indicators.

Biological Indicators (Load Control)

Load control is the process of monitoring and releasing a load based on the results of the biological indicators (BIs) in a process challenge device (PCD), commonly referred to as a test pack. BIs are the only process indicators that directly measure the lethality of a given sterilization process. The BIs should be incubated according to the manufacturer's instructions. BIs should be used in PCDs at least weekly, but preferably every day the sterilizer is in use. Every load containing implants must be quarantined until the results of the BI testing are available. Choose an appropriate BI PCD for each type of sterilization process. Place the BI in the area of the PCD which will pose the greatest challenge to air removal and sterilant penetration. Incubate the BI test and control vials. Read and record the results. Release the load if the monitoring results are correct. If spores are not killed in routine spore tests, the sterilizer should immediately be checked for proper use and function and the spore test repeated. If spore tests remain positive, use of the sterilizer should be discontinued until it is serviced and the appropriate supervisor or infection control department should be notified immediately.

Recall

ANSI/AAMI ST79 states: “If it is determined that the sterilization failure was not the result of operator error, items processed in the sterilizer since the last negative BI results should be considered unsterile. They should be retrieved, if possible, and reprocessed. The sterilizer in question should be taken out of service.”

Recordkeeping

Recordkeeping will document which materials have been processed and will provide evidence of monitoring control for those items. If there is a sterilization failure, accurate records will enable each package to be traced through the monitoring controls to the sterilization event. If there is a sterilization failure, your records will enable you to trace each package through the monitoring controls to the sterilization event itself. A journal/log should record information on each cycle including:

  • Lot number.
  • Contents of load.
  • Exposure time and temperature if not on a recording chart.
  • Operator identification.
  • Date.
  • Results of the BI testing.
  • Results of Bowie-Dick testing, if applicable.
  • Results of the chemical indicator in the PCD (BI challenge test pack, BI challenge test tray, CI challenge test pack).
  • Any reports of inconclusive or nonresponsive CI in the load.

The practice should develop policies that outline how long the sterilizer records should be kept.

Quality Assurance/Quality Improvement

"Quality assurance testing of routinely processed items should be performed on an ongoing basis." (Young p. 95) Routinely processed items should be periodically tested. Testing should also occur when major changes have been made to packaging, wraps, or load configuration. See Table 2 for Periodic Product Quality Assurance Testing of Routinely Processed Items. (Young p. 96)

Table 2: Periodic Product Quality Assurance Testing of Routinely Processed Items

  1. Follow medical device manufacturer's instructions for processing the device.
  2. Place CIs and BIs in the areas of the product determined to be the least accessible to steam penetration.
  3. Label as test.
  4. Place in a standard load.
  5. Run the cycle.
  6. Retrieve CIs and BIs.
  7. Read and record the results of the CIs.
  8. Incubate the BI test and control vials. Read and record the results.
  9. Place the product into routine use if the monitoring results are correct, and there is no evidence of moisture.

Maintenance

Sterilizers can easily malfunction if not carefully maintained. The unit should be level. Follow the manufacturer's instructions for water purity requirements (distilled or demineralized water is usually recommended), filling and draining of the sterilizer, and general maintenance. Failure to use distilled water may damage the sterilizer, clog a valve with mineral deposits, and cause a dangerous situation. Routine cleaning of the chamber walls, door gasket, and draining of the line basket is necessary to ensure that mineral deposits or other obstructions do not interfere with proper functioning. Follow the sterilizer manufacturer's instructions for cleaning but generally, the following is recommended:

  • Wipe the chamber and the door with a damp cloth and mild soap. Drain the water from the reservoir on a weekly basis and refill.
  • Flush the system as per the manufacturer's recommendation with a sterilizer cleaner.
  • Remove the door gasket every three months. Wash with soap and water, inspect for cracks or cuts, and replace if needed. Run an empty load to ensure the sterilizer is operating properly.
  • Inspect ink cartridges and paper rolls of units equipped with readouts and graphs.

Several components of a sterilizer are subject to wear necessitating periodic inspections and maintenance of steam traps, filters, valves, and gaskets. Service providers are available to maintain table top sterilizers.

Safety

Hot pressurized steam that sterilizers generate makes them serious burn hazards. Sterilizer doors must be locked into place before operating a cycle. Many units have a safety mechanism that prevents the sterilizer from operating if the door isn't closed properly. Use caution if your model doesn't have this safety mechanism.

  • Do not operate in the presence of flammable material.
  • Allow sterilizer to cool for at least 10 minutes before unloading, performing maintenance or cleaning.
  • Wear protective gloves and apron when removing a processed load.

References:

Young, M. (2007). Quality control of table-top steam sterilizers. Managing Infection Control, 82-97.

Hubbard, C. (2010). QA for table-top steam sterilizers. Healthcare Purchasing News, 46-48.

Centers for Disease Control and Prevention. (2008). Guideline for Disinfection and Sterilization in Healthcare Facilities, W.A. Rutala, PhD., MPH; D.J. Weber, MD, MPH, and Healthcare Infection Control Practices Advisory Committee (HICPAC)

3M Medical Quality Control for Table-top Steam Sterilizers

Instrument Reprocessing: Best Practices in Sterilization and HLD, Rose Seavey, MBA, BS, RN, CNOR, CRCST, CSPDT: https://cdn.ymaws.com/www.osap.org/resource/resmgr/annual_conf_2017/Presentations_Saturday/SterilizationBestPractices.S.pdf

ANSI/AAMI: ST79:2017. Comprehensive Guide to Steam Sterilization and Sterility Assurance in Healthcare Facilities