Sterilizing Medical Equipment

Medical professionals are legally obligated to provide patients with a standard of care. One of the key requirements for meeting this standard of care is the proper sterilization of medical equipment.

Healthcare organizations are audited by various groups; chief among them are The Joint Commission, DNV-GL and the Center for Medicare & Medicaid Services (CMS). Healthcare institutions are required to comply with policies outlined by their organizations and the standards to which they audit, as well as the recommended practices of the Association for the Advancement of Medical Instrumentation (AAMI), the Association of periOperative Registered Nurses (AORN) and the International Association of Health Central Service Materiel Management (IAHCSMM).

The Risks of Improper Sterilization of Medical Instruments

There are many risks associated with the improper sterilization of medical instruments; that said, the three most significant are as follows:

1. Using the incorrect sterilization process for a product or piece of equipment can damage that item. Certain sterilization techniques utilize temperatures that can melt some materials, such as plastics. This is unacceptable for any item, but for a major piece of equipment such as, say, the robotic arm for a da Vinci Surgical System, it presents a major problem, both for procedure readiness and for replacement cost. Another issue with choosing the incorrect sterilization process is that if a medical instrument is processed using a method that has not been validated for processing, that instrument might not come out sterile.Any medical facility found using the incorrect sterilization processes is subject to reimbursement penalties or other enforcement actions by CMS, or potential revocation of accreditation by the Joint Commission or other accrediting agencies. That’s why, when sterilizing any instrument, it’s important that you refer to Instructions for Use (IFU), which are the manufacturer’s guidelines for processing that instrument. If, for any reason, the IFU are unclear, it’s recommended that you contact the manufacturer directly for instruction or refer to the IFU for a similar piece of equipment.
2. Improper sterilization has the potential to spread disease or result in a Healthcare-associated Infection (HAI). Regardless whether you use steam sterilization or a low-temperature sterilization option, to ensure patient safety, it is essential to follow IFU, clean the device correctly, verify cleaning and to select the correct sterilization process. Anything less could jeopardize the health of your patients and put your medical facility at risk.
3. Some devices require longer exposures than others because of the way they’re built and, in some cases, because they were improperly validated. To that end, referring back to the IFU and creating common classes for instruments so that you can process more than one item at a time is critical. AAMI ST90 establishes a formal process for creating product families that can be sterilized under common conditions. Some conditions are more critical than others — for example, if you attempt to use a vacuum cycle to sterilize a device that is only supposed to be sterilized using a gravity cycle, that device might explode. Again, the importance of following IFU cannot be overstated.

How Do Hospitals Sterilize Surgical Tools?

Strange as it might sound, sterilizing surgical tools and other medical instruments isn’t as simple as just sterilizing them. Instead, it requires a three-step process ending with sterilization.

Know the Difference Between Point-of-Use Cleaning, Decontamination & Sterilization >>

The process is as follows:

1. The hospital will start the precleaning process at the point of use. Precleaning can take the form of irrigation with water (preferably distilled water) or spraying with a transport foam or gel (typically an enzymatic cleaner, which eats away at patient soil).
2. Once an item has been precleaned, it moves on to decontamination, which typically involves manually cleaning the instruments to remove gross soil. This is optimally followed by use of an ultrasonic cleaner to remove any residual patient soil if the instrument can tolerate sonication. Next, any eligible items would go through an automated washer disinfector. Items coming out of the automated washer disinfector are inspected by technicians to ensure that they are clean and functional and then packaged for sterilization.
3. Finally, the item undergoes sterilization, which we will describe in the next section.

As you can see, this is a very involved, labor-intensive process, one that requires a great deal of careful inspection; that said, technological advancements such as borescopes provide advanced assurance that the devices are clean.

Sterilization Techniques for Medical Devices

There are a few different techniques that medical professionals can use to sterilize instruments, devices and other equipment:

Autoclaving: Also known as steam sterilization. There are two different types of steam sterilization; each one is based on how air is pulled out of the autoclave chamber and how steam is vented in.

• Gravity displacement is the oldest and simplest form of steam sterilization. It admits steam in from the top of the autoclave chamber and pushes air out of the bottom. Gravity displacement is ill-suited for complex instruments, but it is ideal for simple devices or those that will be damaged by a vacuum. Gravity displacement takes longer than the alternatives and offers less throughput.
• Dynamic air removal refers to the process by which an autoclave alternates steam and vacuum pulses or steam pulses and venting to ambient pressure (known as steam flush pressure pulse, or SFPPs) in order to remove air from the chamber and instruments and allow steam to penetrate the load. Vacuum cycles are preferable for most applications because they can pull air out and ensure contact of the steam with the entire instrument in a sequence of three to four pulses. Vacuum cycles also actively remove air from instruments, making sterilization faster — there’s nothing between the steam and the instruments themselves.

Ethylene Oxide: Ethylene oxide is one of two sterilization options for items that cannot be processed using steam. Ethylene oxide used to be the dominant form of low temperature sterilization but is a slow process and has therefore been largely replaced by vapor hydrogen peroxide.

Vapor Hydrogen Peroxide: Vapor hydrogen peroxide is another form of low temperature sterilization. Though it initially presented market and material issues, many of these have been resolved, making it the dominant method for low temperature sterilization. There are a number of different vapor hydrogen peroxide sterilizer manufacturers and their processes, including those that use gas plasma or ozone as part of the sterilization cycle, are, as far as hospitals are concerned, essentially equivalent and aimed at low temperature sterilization. The reason for this that neither gas plasma nor ozone contribute to the sterilization of the products but instead are present to help destroy residual hydrogen peroxide.

The Benefits of Steam Sterilization

Steam sterilization is fast, robust, the least expensive option per instrument and is more generally applicable in hospitals and other medical facilities than other sterilization methods.

Steam Sterilization Process

All medical instrument sterilization processes share three common features: air removal, a steam injection and sterilization phase and steam removal and drying. The difference between gravity and vacuum steam sterilization cycles comes down to how air is removed from the load and how steam penetrates into the load.

Gravity Cycle

1. Once the sterilizer door has been closed and sealed and the cycle started, the chamber drain valve opens.
2. Steam is admitted into the sterilizer chamber, which pushes the air downward because hot steam is less dense than air. Gravity cycle gets its name from this downward air flow.
3. The steam pushes the air out of the load.
4. After a predetermined period of time, or when the chamber drain temperature reaches 100°C / 212°F, the drain valve closes, allowing the chamber to pressurize with steam.
5. When the chamber temperature reaches the programmed temperature, the steam valve cycles in order to maintain that temperature without overheating.
6. At the end of the cycle, the steam valve closes, and the drain valve opens. Normally, the steam either mixes with water or runs through a cooling heat exchanger on its way to the sanitary drain in order to cool it and avoid damaging the drain.
7. On some gravity steam sterilizers, a vacuum device — either a pump or ejector — turns on to help dry the load after the steam pressure has fallen to a temperature that the vacuum device can tolerate. Once the drying phase is complete, HEPA-filtered air enters the chamber to return it to atmospheric pressure. The cycle is now complete.

Vacuum Cycle

1. The door is closed and sealed, and the cycle starts.
2. The chamber drain valve opens.
3. Steam is admitted into the sterilizer chamber, which pushes the air downward.
4. The steam pushes the air out of the load and preheats it.
5. After a predetermined period of time, the steam valve closes.
6. A vacuum device turns on and removes air from the chamber and the load.
7. Once the sterilizer has reached the programmed vacuum level, the vacuum valve closes, and the vacuum device shuts off.
8. Steam enters the chamber in order reach the programmed pressure.
9. Once the chamber has reached the programmed pressure, the steam valve closes.
10. Steps five through seven are repeated twice or more, ending with an evacuation.
11. After the last evacuation, the drain valve closes, and steam enters the chamber to pressurize it.
12. Once the chamber reaches the programmed temperature, the steam valve cycles to maintain that temperature without overheating.
13. At the end of the cycle, the steam valve closes, and the drain valve opens. Normally, the steam either mixes with water or runs through a cooling heat exchanger on its way to the sanitary drain in order to cool it and avoid damaging the drain.
14. Once the steam pressure has fallen to a programmed level, the vacuum device turns on to help dry the load. Once the drying phase is complete, HEPA-filtered air enters the chamber to return it to atmospheric pressure. The cycle is complete.

Steam Sterilization Cycle Guide

The key difference between the two approaches listed below — gravity and dynamic air removal, or vacuum — is that with air being removed, there is no blockage of steam penetration into the load. For this reason, dynamic air removal cycle exposure times are much shorter than gravity cycle exposure times for the same temperature.

Where to Find Steam Sterilization Equipment

Hospitals and other facilities looking to acquire an autoclave for medical use are advised to contact Consolidated Sterilizer Systems. We offer medical series steam sterilizers designed to sterilize at temperatures between 250°F and 275°F, as well a stainless steel vessel construction in a variety of sizes and program control options.

To learn more about our medical series steam sterilizers or what Consolidated can do for you, contact us today.