Instrument Processing Essentials: Key Steps for Sterilization and Storage

Instrument processing is critical to ensure sterility of instruments utilized on patients. There are four steps in processing instruments: cleaning, packaging, sterilization, and storage. This article will focus on the last two steps: sterilization and storage.  

Earle H. Spaulding. PhD, devised a rationale for disinfection and sterilization of instruments and items. He categorized instruments and items into three categories: critical, semi-critical and non-critical.

• Critical items enter normally sterile tissues, including the vascular system.
• Semi-critical are instruments or items that contact mucus membranes or non-intact skin.
• Non-critical items contact intact skin and not mucus membranes.

All instruments and items are cleaned first.

• Once a critical item is cleaned, it is packaged and heat sterilized.
• Semi-critical items are cleaned, and heat sterilized; if the item is not heat stable it can be high-level disinfected.
• Non-critical items are to be low-level disinfected.

Sterilization of instruments achieves destruction of all forms of microbial life either by physical or chemical methods. There are different ways available to sterilize critical and semi-critical instruments/items utilizing either high or low temperature methods. Most instruments are heat stable and therefore undergo steam sterilization. Other ways to sterilize are utilizing dry heat or chemical sterilant/disinfectants.  

Steam sterilization

Steam sterilization is most widely used and most dependable. Steam sterilization is moist heat in the form of saturated steam under pressure. There are several advantages of steam sterilization:

• it is non-toxic,
• the cycle is easy to monitor,
• it is inexpensive,
• rapidly microbicidal, and
• penetrates packaging.

There are also several disadvantages. These include:

• destroying heat or moisture sensitive instruments,
• dulling or rusting may occur, and
• the potential for burns of healthcare workers when removing the instruments from the sterilizer.  

Types of steam sterilization

There are two types of steam sterilization. The first method of steam sterilization is gravity displacement sterilizer. With this type of sterilizer, steam enters the chamber, and unsaturated air is forced out of the chamber through a vent in the chamber wall. Most common items sterilized are unwrapped instruments, glassware, and solid waste.  

The second method is a pre-vacuum sterilizer. These have a vacuum pump to create a vacuum in the chamber and ensure the air removal from the sterilizing chamber and load before the chamber is pressurized with steam. Wrapped items, surgical packs, and items with complex lumens are typically sterilized in a pre-vacuum sterilizer.  

Sterilizer use

As with any method of sterilization, always use FDA approved devices and closely follow manufacturer’s instructions for proper use. Follow these instructions for maintenance. Sterilizers will be cleaned weekly and monthly following the manufacturer’s recommendations. 

Loading instruments in the steam sterilizer should always be done in a manner to allow the steam to flow, should not be overloaded, instruments should be on the trays in a single layer, and not overlapping. Instruments packs can also be sterilized on their edge. Leave room between packs so the sterilizing agent can contact all sides of every pack. Follow the manufacturers’ instructions on loading the sterilizer. Once the sterilization cycle is complete, allow instruments packs to dry completely and cool before handling. Instrument packs that are handled when wet are not considered to be sterile and therefore should not be used on patients.  

Dry heat sterilizers

Dry heat sterilizers work by transferring heat energy from air inside the oven to the instruments. Simply put, it utilizes hot air to sterilize. Dry heat is good for items that are likely to dull or rust, powders, or ink that require sterilization. The packaging material must be able to withstand high heat. A disadvantage to dry heat is it is slow, and many instruments can’t withstand the high heat.  

Liquid chemical sterilant

Lastly, an alternative sterilization process for heat sensitive items is utilizing a liquid chemical sterilant cleared by the FDA. Liquid chemical sterilant is commonly referred to as cold sterile or a cold boat. The disadvantages to utilizing a chemical sterilant is exposure can be powerful and toxic and can be harmful to healthcare workers and patients if manufacturers’ instructions for use are not followed closely. Items in a chemical sterilant cannot be stored because they are not wrapped. For this reason, CDC encourages the use of heat tolerant and disposable items.  

Instrument storage

Now that we have cleaned, packaged and sterilized instruments, the last step is storage. Store instrument packs away from contaminants and leave instruments in packaging until ready to use. Removing instruments from the packs ahead of time is not recommended. Preferably, packs are stored in a closed drawer or cabinet; never under a sink where packs can become wet. Ensure the area used for storage will provide protection from moisture, dust, temperature, and humidity extremes. If a pack becomes compromised during storage, do not use the instruments for patient care. Instead, clean, repackage, and re-sterilize.  

Items are stored utilizing either event-related or time-related storage.

• Event-related storage means the items will remain sterile and can be used indefinitely unless the packaging becomes compromised.
• Time-related storage means items remain sterile for varying periods depending on the type of material used and manufacturer instructions on shelf life. If utilizing time related, the pack should be labeled with date of sterilization and expiration date.  

Following all the steps in instrument processing are equally important. All steps must be performed correctly every time to ensure that instruments are processed properly and in the safest way possible. Your patients will thank you!