Steam is the most preferred, least expensive and most reliable method of sterilizing your non-heat-sensitive instruments and equipment for surgery. Whether you're shopping for a portable tabletop model or a fixed room-size steam sterilizer, here are some factors to consider, purchasing insights and thumbnail sketches of eight autoclaves.

ABCs of steam sterilization
Moist heat in the form of saturated steam under pressure is the most dependable medium known for the destruction of all forms of microbial life. The microbe-destroying power is composed of two factors, both of which are essential: moisture and heat.

In the most basic terms, a steam sterilizer is a pressure-type vessel with a door or cover, valves to control the entry and exit of steam and air, and monitoring devices to let the operator observe (and record) conditions inside. It's designed to hold items and let steam under pressure contact all surfaces of the items being sterilized. The three most common types of steam sterilizers are

• Gravity displacement. Incoming steam displaces residual air through a port or drain in or near the bottom of the chamber.
• Pre-vacuum. These depend upon one or more pressure and vacuum excursions at the beginning of the cycle to remove the residual air. This method results in shorter cycle times for wrapped items because of the rapid removal of air from the chamber and the load by the vacuum system.
• Steam-flush pressure pulse. A repeated sequence of flushing the chamber with steam followed by pressure pulses removes air from the chamber and processed materials using steam at above atmospheric pressure (no vacuum required). This type of sterilizer is not susceptible to air leaks because air removal is achieved with the chamber pressure always above atmospheric pressure.

Note that the common thread of all three types of steam sterilizers is the removal of air from the chamber and its contents. The presence of air in and around the items being processed impedes the steam from contacting all surfaces.

Sterilizing with steam under pressure
When buying an autoclave, you have to think and plan from the outside-in. One of the most important issues is determining where your steam will be coming from. There are two common sources for steam used for sterile processing: steam boiler systems and self-contained packaged steam generators.

Regardless of which system you choose, you should design, monitor and maintain it to ensure that the quality, purity and quantity of the steam is appropriate for the sterilization system you're designing. Steam of poor quality can contribute to wet packs and suboptimal cycles that your monitoring system won't be able to identify. In addition, the hardness and pH of the water you use to generate the steam will affect steam purity. It's important to monitor boiler additives and feedwater conditioners to prevent carryover of excess chemicals.

Design your steam quantity to meet your peak demands. Undersized supply systems can lead to the malfunction and aborting of sterilization cycles, affect steam quality, and damage your boiler and distribution systems. If your sterilizer and your steam source are in different locations, you'll have to ensure that the steam can be piped in with sufficient pressure, especially if central processing is located upstairs from the source, says Susan Klacik, BS, CRCST, ACE, FCS, the corporate director of sterile processing for Forum Health in Youngstown, Ohio.

Your boiler plant may not actually be the best source due to the overall design of the system and the type (and method of use) of boiler feedwater treatment chemicals. If you don't have the in-house capability and expertise to produce, monitor and maintain the quality of the steam coming from the boiler, your best alternative may be to purchase a dedicated steam generator designed to work with the sterilizer you buy.

Like the availability of steam and other utilities, another key concern in purchasing a sterilizer is where you're going to house the equipment. The placement of the unit - and the resulting physical and functional layout of the processing area - is one reason why smaller surgery centers and office-based suites often prefer tabletop sterilizers.

"The production flow from dirty to clean is ever-important," says Diane Gantt, RN, FCSP, president-elect of the American Society for Healthcare Central Service Professionals. "But will your sterilizer fit in with the process?"

Consider the machine's footprint and the available floor space, says Ms. Gantt. Remember that you'll need a place to open the door, pull out the loading cart and let it cool where it won't obstruct staff traffic or be compromised by this traffic and other environmental conditions. How will it interface with the decontamination area on one side and the sterile storage and the OR on the other? This is where the option of a double-door sterilizer may prove valuable.

The right chamber
Once you've settled the external details, it's time to look inside the sterilizer. Two main factors should guide your choice of chamber: load size and processing volume.

What do you need in chamber capacity now, and projected into the next five years? What will be the smallest and largest loads anticipated? "Chamber size is important," says Ms. Klacik. "Some of the instrument trays are really long or wide, so measure your equipment and the sterilizers you're considering to make sure you can fit what you have."

Budget backwards, says Greg Stett, a clinical analyst for MD Buyline, a Dallas-based healthcare research consulting firm, "You have to totally assess what it is you intend to sterilize," he says. "Not only what you do today, but what you intend to do in the future. Then, by association, what types of instruments you'll be using. That would dictate what sort of sterilizing equipment you need to buy."

There's good reason to do the math. Load size affects processing volume, how often you can or have to run the machine. "It's not efficient to have a machine bigger than you need," say Ms. Gantt, "especially since sterilizers work best when they're full and worst when they're nearly empty. Are you expecting a rise in volume? Or do you have many sudden demands for processing?"

"If you could build your perfect sterilizing area," says Ms. Klacik, "you'd have a small sterilizer as well as a large sterilizer, which would actually improve productivity. You would have the flexibility to process a big load of instrument trays or linen packs, for example, and to do something in between if someone comes down and says, I need this right away."

Keeping time in mind
Whatever system you decide on, you'll want to keep in mind the time element. Ask yourself the following three questions:

• What will be the sterilizer's hours of operation?
• Will it only run a few days of the week, or will it run 24/7?
• How fast will your turnaround times need to be?

Mr. Stett advises backward planning on this question as well. Multiply the cycle time by how many cycles you'll run in an average day to make sure you don't run out of hours. "It's budgeting your time," he says. "You may find you'll have to increase your hours of operation or your staff, especially if you see an increased caseload. You don't want to be in the position where you can't meet the volume."

The chamber's dimensions are also a variable in processing time. While a sterilizer with a larger chamber may handle a larger quantity of instruments, its cycle may take longer to complete; just as a smaller sterilizer may work faster, but has limited capacity, says Mr. Stett.

Ms. Klacik suggests considering a sterilizer model with variable cycle times. "Something that you could extend to adjust time in accordance with a manufacturer's recommendations," she says, "which are the first thing we look at when new products come onto the marketplace."

Let's not forget about record-keeping. She also urges buyers to make sure the sterilizer can deliver complete, accurate documentation of its cycles and operation, perhaps even through bar coding and networking with your facility's computer system.

Use and repair
You can't overestimate the importance of a reliable autoclave. "When a sterilizer goes down, all your surgery comes to a halt," says Ms. Klacik.

Fortunately, says Mr. Stett, reliability isn't usually difficult to find. "Customers, especially customers of the major manufacturers, have told us that they're all very reliable, as far as hardware and engineering."

While a reliable service contract from the manufacturer or a third party is a necessity, "it goes without saying that ease of operation, ease of cleaning, and ease of taking care of things like checking the gasket and removing the strainer are important," says Ms. Klacik. Inquire about in-house maintenance. You'll appreciate the ability to do quick repairs and basic periodic checks. With your purchase, you should get a full in-service and training in preventive maintenance from the manufacturer.

"Get a lot of educational support from your manufacturer," says Ms. Klacik. "The company that I'm choosing has got to be able to provide instructions on the correct use and maintenance."

New or refurbished?
As with most medical equipment, there is a market for refurbished steam sterilizers, although if you choose this option you'll want to review your choices with an especially sharp eye.

There isn't much that goes wrong with steam sterilizers, provided its owners used good steam and stuck to a regular preventive maintenance schedule, but you should never purchase a used sterilizer directly from a former owner unless the machine has gone through a complete check-up by the original manufacturer. It may need complete refurbishing.

"Be aware that if you buy from a third-party refurbisher, you may not get the original equipment manufacturer's support," says Mr. Stett. "If that's the case, it's very important to get [the refurbisher] to give you a list of satisfied customers, so you can contact them for their opinions."

Who's in charge?
Last, but far from least, is the question of who will be in charge. In no uncertain terms, someone who has gone through a central sterile processing certification program should have a say on what steam sterilizer to buy, and have the last word on what can and cannot be done. This person should be responsible for hiring and training staff, setting employee qualifications, creating continuing education opportunities, and operating and maintaining the equipment.

Nothing will doom a sterilization process more than having it run by someone who isn't trained specifically in sterilization technology. Having the right (properly trained) person is the key to successfully buying, installing, operating and maintaining sterilization equipment.