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What's New in Low-temperature Sterilization
Find out how the new H202 vapor system stacks up against plasma, EtO and peracetic acid.
Nathan Hall
Publish Date: August 7, 2008   |  Tags:   Infection Prevention

If you're in the market for a low-temperature sterilizer, you'll need to brush up on the latest options. Gone are the days when the only choices for low-temperature sterilization were ethylene oxide or peracetic acid. In effect, those choices were an effective sterilization that took 16 hours and a considerably quicker, wet method where instruments weren't wrapped afterward.

Since then, hydrogen peroxide gas plasma sterilizers have set the standard at many facilities. The average cycle times for these systems range from 42 minutes to 70 minutes, and you can wrap instruments so they'll stay sterile for later procedures.

Now there's a new system on the market that uses vaporized hydrogen peroxide without converting it to plasma during the sterilization process. Its manufacturer claims it offers improvements over the older technologies, but are they enough to warrant choosing it over other options available to you?

No plasma necessary
The Amsco V-Pro 1 Low Temperature Sterilization System from Steris Corp. has been used for just over a month at Kadlec Medical Center in Richland, Wash., and sterile processing technician Christine DeLeon says it's working rather well.

"It's not as moisture-sensitive," says Ms. DeLeon. "If there was a drop of water on the instruments in our Sterrad machines, they would abort the cycle. That didn't happen to us often, because we're good at blow-drying our instruments, but once or twice a week we'd have a load abort due to moisture."

She says that, so far, the V-Pro has not had any aborted cycles. Steris says that the machine can handle wet and dry materials. Despite this difference, Ms. DeLeon says the V-Pro is quite similar to the Sterrad system. It is easy to load and operate and has a 55-minute cycle time, which is similar to plasma systems. But when dealing with sterility assurance, she says, it can take up to four days to get the readout from a biological indicator included in the sterilization cycle. Sterrad currently has a 48-hour BI readout.

The quicker biological readout time is one advantage Sterrad has over V-Pro, and it may become a greater difference. Sterrad's manufacturer, Advanced Sterilization Products, says it's planning to launch a new technology for indicators later this year that will make the information available 24 hours after the cycle is complete.

When it comes to comparing the actual process, Wally Puckett, PhD, vice president of science and technology for Steris Corp. in Mentor, Ohio, says the main point is that the V-Pro eliminates the need for a plasma generator. "From a practical point of view, users have to be careful when using a Sterrad system, because if any part of the load touches the coil, the cycle will abort," he says.

To clean the instruments, Dr. Puckett says, the V-Pro works by exposing the instruments through the elimination of air inside the chamber and letting a set amount of hydrogen peroxide stay inside the system as opposed to converting it to plasma through energy during the conditioning phases. "They claim that plasma helps to aerate the system by destroying the hydrogen peroxide," he says. "Frankly, plasma is clearly not required for sterilization in our estimations, and we've proved that to the FDA."

While the Sterrad systems come in a variety of sizes, with chambers ranging from 30- to 150-liter capacities, the V-Pro is only available with a 136-liter chamber. "That's the size of a small-to-medium steam sterilizer, so it's not a large unit, but it's enough to give a facility the productivity and throughput they need," says Dr. Puckett. "From a marketing point of view, we learned that the marketplace is more interested in a one-size-fits-all solution."

As for the price, Dr. Puckett says the V-Pro has an edge over Sterrad. According to Steris, the V-Pro has an initial capital cost of $100,000 and a per-cycle sterilant cost of $11.25. The company claims that both of these are less expensive than the costs for Sterrad systems. (Advanced Sterilization Products declined to verify Steris's approximations for Sterrad's list prices or cycle costs, nor did it provide its own figures, saying their costs vary by model, purchasing contract and the size of the cycle).

Both technologies also have similar limitations. The V-Pro may be more tolerant of moisture, but Dr. Puckett says the system's labeling makes it clear that the equipment has to be dried before being loaded, because moisture interferes with the vacuum process. "If it's a really wet load, the cycle will abort," he says. He also points out that "all hydrogen peroxide systems, regardless of whether they use liquids or gases, are incompatible with cellulose."

Long lumens remain a problem, as the V-Pro is only FDA-approved for lumen sizes >1mm x 125mm, >2mm x ?250mm and 3mm x ?400mm. For devices with longer lumens, Dr. Puckett says, a peracetic acid system is a perfect complement.

Some advantages of acid compared to EtO, he says, are its low cost ($17,000 list price for a System One from Steris, $7.50 per cycle) and that it has no limitations for lumen length, because it can be pumped through the channels to sterilize an instrument in 30 minutes. This is especially significant for an endoscopy suite. But since this is a wet system, he says, the instrument cannot be put in a pouch or wrapped, but rather must be used almost immediately for the procedure.

Ozone for Clean Instruments and Clean Air

The TSO3 125L Ozone Sterilizer uses oxygen in a natural process to manufacture its own sterilant, ozone, for pennies a day, says the company. Ozone is an effective microbicide, safe for users and patients, and poses no danger to the environment, according to the company. The sterilizer operates at low temperature and is designed for the rapid sterilization of instruments that are sensitive to heat and humidity.

"The machine is a good companion for our Sterrad machine," says Chrys Hatem, RN, CNOR, perioperative materials coordinator at the AnMed Health System in Anderson, S.C., which was a beta site for this technology four years ago and still has the machine today.

Even though the cycle time is about four-and-a-half hours and her facility had to purchase more instruments to compensate for this, Ms. Hatem says that is counterbalanced by the environmental benefit and savings from cycle costs. "The reduction in cycle costs is absolutely phenomenal. When we looked at the numbers, we saved about $28,000 on reprocessing a single item we studied."

The water, oxygen and electricity needed for an ozone cycle cost 85 cents at most, says Ann Hewitt, vice president for global sales at TSO3. Its list price is $165,000 for a full system. Ms. Hewitt adds that it has very broad lumen claims, as it can handle instruments with an inside diameter of 0.9mm and a length up to 485mm.

— Nathan Hall

All about the cycle time
Although she isn't familiar enough with the V-Pro system to do a full comparison between vapor and plasma sterilizers, Nancy Chobin, RN, AAS, ACSP, CSPDM, sterile processing educator for St. Barnabas Healthcare System in Livingston, N.J., says she's not ready to give up her Sterrad machines for something with a little more resistance to moisture. "I wouldn't go to that one system on that basis alone," she says. "As long as the employees follow the instructions with Sterrad, it works well. I've been working with that technology since 1991 and I've never had a problem with it."

Since Ms. Chobin's facility was one of the research sites for the Sterrad systems, she saw her staff climb a learning curve when it came to not putting cellulose-based materials such as towels into the sterilizer, but this has gotten considerably easier now that other suitable materials are on the market. "It really isn't an issue now that almost all facilities use non-cellulose-based sterilization wrap," she says. "And just about every company makes Tyvek pouches." Furthermore, there are now sterilization labels and other products specifically designed to be compatible with the Sterrad process, including foam tray liners.

Compared to the other technologies on the market, particularly EtO and ozone, Ms. Chobin says the short time for plasma sterilization gives it a significant advantage. "EtO is a wonderful sterilant and it's still in use, but pretty much everyone recognizes that these days we cannot tie up our instruments for hours and hours, because they're so sophisticated and expensive that we can't afford multiple sets of them," she says. "As for ozone, if I told my OR staff that we were going to take away the Sterrad systems for something that will take more than four hours per cycle, they would not tolerate this decision well. Sterrad set the bar for cycle times, and unless someone comes in with something quicker there's no reason to go to anything else."

Still a place for gas
The new systems may make much of their shorter processing times, but there are still sterilizers on the market that use EtO. The 16-hour cycle time remains a factor, yet Kathy Jorgensen, general manager and western states distributor at H.W. Andersen Products of California's Haw River, N.C., office, says EtO is comparable to plasma and vapor systems.

"When I meet people at conferences, I often ask them what they like about Sterrad systems other than the cycle time," says Ms. Jorgensen. "It's faster, there's no question about that, but if you take into account the special trays you need, the chamber sizes, what happens when the item is not compatible because it has anodized coatings on aluminum or is made from brass, or it contains certain foams or anything that is cellulosic, you have a problem that you will not have with EtO. You also can't use pressure-sensitive labels on the packs, or traditional packaging materials, or process long, narrow lumens."

In contrast, Ms. Jorgensen says, EtO sterilizers have an overall advantage in low temperature sterilization because they sterilize a wide range of items, from fiber optic scopes to compression sleeves, without fear of corrosion or other damage. "The fact that EtO has the best capability for penetrating narrow lumens is one of the reasons we think it's the best gas sterilant for medical use," she says.

EtO emissions can be addressed with an abator if local codes require it, says Ms. Jorgensen, and all of the systems use small unit doses that contain 10.5 grams to 17.5 grams of EtO per cycle. "The amount of EtO used is minimal because the gas diffusion process eliminates filling an entire chamber," she says. "If you used five cases of ampoules a year, you still wouldn't reach five pounds of EtO." However, she says, it is still important to check with local authorities for their codes and regulations.

As for her company's products, Ms. Jorgensen says the EtO-based Anprolene systems are very affordable for an office-based practice or clinic. An AN74i from Andersen, an EtO tabletop system, costs $4,465.60, while a slightly larger AN2000 costs $5,015.60. Both of these prices include a starter kit with enough supplies for 40 cycles, including sterility assurance indicators and a monitor kit. The average cycle cost comes to about $12.25, she says.