The Newest Alternatives to Steam

Infection Prevention

By: Michael Krivda

Published: 10/10/2007

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When steam's too harsh, and if you want to move away from ethylene oxide, gas plasma or ozone may be the answer.


Steam is still the gold standard when it comes to sterilization; it's quick, cheap and effective. Unfortunately, it can't be used on all your instruments because of the high temperatures - and resultant wear and tear - it subjects them to. While there are clear advantages to ethylene oxide (EtO) as the less-corrosive alternative, and it has been in use for more than 40 years, high operating costs, long cycle times, flammability and high toxicity have driven the development of alternatives. The two latest: hydrogen peroxide gas plasma sterilization (HPGPS), which is environmentally friendlier, faster, convenient and more cost-effective than EtO; and ozone which, while significantly slower than gas plasma, is considerably less expensive, and - in certain applications - may offer a better alternative.

Here's a look at how what we've learned from studies and a review of what you should consider when planning your sterilization strategy.

The gas plasma advantage
Gas plasma sterilizers introduce vaporized hydrogen peroxide to the chamber, allowing this oxidizing sterilzant to circulate. The sterilizer then produces a cloud of ions by passing electric or magnetic chargers through the hydrogen peroxide vapor, releasing free radicals that disrupt cell activities and killing the microbes it contacts. HPGPS offer dry, low-temperature sterilization in about one hour. Since the byproducts of plasma sterilization are primarily water and oxygen, there is no need for aeration or environmental hazard concerns. And they can usually be plugged into almost any outlet of sufficient amperage, with no need for other utilities such as water, making the devices easy to install and relocate. Studies have shown that gas plasma is easier to maintain than EtO1 and that it sterilizes most medical instruments and material without leaving toxic residues.2

In 1992, the Saint Barnabas Medical Center in Livingston, N.J., became a beta site for testing HPGPS as a possible replacement for its EtO sterilizers. Because of the success of the program, the medical center scrapped its EtO sterilizers in favor of the gas plasma sterilizers in 1997. According to Sharon Gilbert, RN, the director of central sterile processing at St. Barnabas, the decision to remove the EtO sterilizers was easy: "We initially looked at the hydrogen peroxide sterilizers for environmental reasons," she says. "We were all concerned about our staff's being exposed to the ethylene oxide. But the hydrogen peroxide sterilizers were so much faster than the older equipment (about 50 minutes versus more than 12 hours, including aeration) that there really was no question that we should be using them."

HPGPS has been shown effective in sterilizing equipment used in minimally invasive surgery,3 including those with long lumens,1 more cheaply than with EtO - and for a cost similar to that of steam if you take damage into account.4 St. Barnabas has had the same experience.

"We use those sterilizers for our OR cameras and scopes, things that cannot be sterilized in our steam units," says Ms. Gilbert. "Because the peroxide units can turn the equipment around in less than an hour, instead of the 18 hours the EtO sterilizers required, we saved hundreds of thousands of dollars because we were able to operate with far fewer sets of cameras and scopes."

Providing sterilization services for between 22 and 24 ORs, Ms. Gilbert estimates St. Barnabas would have needed to buy an equal number of scopes and cameras to ensure the equipment was available for each room each day. With the fast turnaround, the medical center is able to function with far fewer sets of cameras and scopes, at a substantial savings. "The technology on the optical equipment changes so rapidly that if we needed to maintain a larger inventory of that equipment, we would be spending a lot more money, both to buy the needed inventory and in ongoing upgrade costs."

Another aspect of the equipment that pleases Ms. Gilbert is its reliability both in terms of its ability to effectively sterilize load after load of equipment and its mechanical performance. "We have the same two sterilizers that we installed in 1992, and they have been operating trouble-free virtually around-the-clock since then," she says. "We do routine maintenance and have been able to avoid high-cost repairs."

Where HPGPS falls short
However, HPGPS is a relatively expensive process (compared to the cost of steam sterilization), and the plasma may not penetrate extremely long lumens (such as those of colonoscopes) and may corrode some materials. Porous materials such as paper, cellulose or linen cannot be sterilized using gas plasma technologies.

One study says the success of HPGPS depends mostly on educating staff to assure well-cleaned and dried devices, which will allow penetration of the gas plasma into the critical points of the instruments.5

A gas plasma sterilizer can sterilize stainless steel lumens that are 1mm or larger and no longer than 125mm, lumens that are 2mm or larger and no longer than 250mm, and lumens that are 3mm or larger and no longer than 400mm.

Though completely satisfied with the performance and cost savings of the hydrogen peroxide sterilizers, Ms. Gilbert says St. Barnabas does have some items that must be sterilized with EtO. "We follow the manufacturer's instructions, and if they say to sterilize using EtO, that is what we do," she explains. "We passed our EtO sterilizers on to another medical center in the area, and they sterilize those few items for us, which amounts to perhaps a dozen pieces a week." By comparison, the medical center is using the four hydrogen peroxide units to sterilize about 12,000 pieces a year.

Ins and outs of ozone
While the gas plasma sterilization technology has established a firm hold in the American market, ozone sterilization has yet to penetrate the United States in any significant way. This is evidenced by the lack of research on it, though one study calls it "highly effective and [providing] a reliable safety factor in treating contaminated surfaces."6

Popular in Canada because of its low cost per cycle, ozone technology has not attracted much interest here because of long cycle times. "In Canada, the ozone technology works financially because of the way their healthcare system is structured. Their budgets are fixed, so cycle costs are more important than cycle times," says Janet K. Schultz, RN, MSN, the president of consulting firm Jan Schultz & Associates, in Parker, Colo. "Unless the makers of the ozone technology can significantly reduce cycle times, they are going to have a very difficult time in the U.S. market."

Ozone sterilizers use oxygen, water and electricity to produce ozone. The non-toxic gas. is humidified to 70 or 90 percent and dispersed into a sterilization chamber. Ozone oxidizes and therefore kills the microbes it contacts. After the cycle, the ozone passes through a catalytic converter that changes it back to oxygen. The ozone sterilization process has some materials-compatiblity limitations, making it unsuitable for devices containing natural gum rubber products, some plastics and some metals (such as brass and copper), each of which will corrode or degrade over time, according to the manufacturer. Users should check with the manufacturer of specific devices to determine whether they are compatible with ozone.

According to the manufacturer labels, ozone can disinfect single stainless steel lumens with an inside diameter of 2mm and no longer than 250mm, lumens with an inside diameter of 3mm or larger and no longer than 470mm, and those with an inside diameter of 4mm and no longer than 600mm.

Ozone technology has been approved for use as a medical instrument sterilizer by the Food and Drug Agency (FDA). However, workers might need to wear respiratory protection when working around it,6 and the four-hour cycle time it currently imposes makes is somewhat unattractive. Manufactur-ers are working to improve cycle times and at some point, the cycle time may be quick enough that, when combined with its significantly lower per-cycle cost, may make the technology a more viable choice.

"In its current configuration, ozone technology does not meet the needs of the American market," says Ms. Schultz. "However, the only way currently to reduce the cycle time on gas plasma units is to increase the amount of sterilant used, which increases the already high per-cycle costs. So the ozone technology might have an advantage in the long run if the makers can reduce the cycle times without dramatically increasing the cost."

Considering all options
Gas plasma and ozone do not offer the breadth of application EtO provides, and initial expenditures to replace EtO sterilizers may run into the hundreds of thousands of dollars. But if you consider they have lower per-cycle costs and are safer and faster than EtO, the total cost of owning one of the alternatives better comes into focus. If you are building a facility, starting off with an EtO alternative might make sense.

"A total cost analysis that includes the value of time spent is essential whether replacing or augmenting a current system or installing a brand new service," says Nancy Chobin, RN, CSPDM, the corporate educator for St. Barnabas Healthcare System. "Many administrators make the mistake of only looking at a few major costs and ignoring such factors as the time spent, additional instruments needed and so on."

If you're considering replacing your EtO sterilizers, gas plasma technology may offer the best combination of cost, cycle times and safety for most applications but, says Ms. Chobin, you should also consider that "gas plasma devices may have reached their limit as far as reducing cycle times without significantly increasing costs."

Not gone entirely
EtO will almost certainly continue to be part of a surgical facility's overall sterilization approach, if only because manufactures may specifically call for it for their equipment. However, sterilizing a small number of instruments with EtO while selecting an alternative such as gas plasma to sterilize the majority of instruments appears to be the best approach in most cases. An option that you might want to consider is outsourcing your EtO sterilization, which may add to the total turnaround time, but would address the environmental and staff safety issues associated with the use of EtO.

"At the moment, it may be impossible to completely eliminate ethylene oxide from a sterilization strategy," says Ms. Schultz. "But, with the reduced costs and faster turnaround time that some newer technologies afford, not to mention the environmental advantages, it is crucial for healthcare facilities to begin moving in the direction of those technologies as quickly as possible."

Can You Safely Flash Sterilize Implantables? Yes, but only in emergencies

Bill Meltzer
Senior Associate Editor

For many years, facilities have had a simple policy regarding flash sterilizing implantable devices: It's never acceptable under any circumstances. The risk of infection is considered too high, and even facilities with flash sterilization policies excluded implantables.

Now, a handful of facilities, most notably Johns Hopkins University Hospital in Baltimore, has reconsidered. Here's a look inside the implantables policy Hopkins revised in November.

Never a recommended practice
"The most important point we emphasize is that flash sterilization of implantables is never a recommended practice," says Trish Perl, MD, of the university's school of infectious diseases. "It's strictly an emergency protocol."

The hospital requires vendors to make special items such as implantables available to the facility before the day of surgery. At the very least, the implants must be delivered with sufficient same-day lead-time to permit standard pre-packaged sterilization, obtaining a negative biological indicator test and releasing the device.

However, staff may flash sterilize the implantable device if circumstances arise where the device arrives with insufficient time for conventional sterilization before a case starts.

Emergency implantable flashing protocol
If the need arises for flashing an implantable, Hopkins staff must precisely comply with and document the following steps:

  • Before sterilization, staff must inspect implantables for defects, organic soil or debris, then clean the instruments according to manufacturer instructions, employing brushes for thorough cleaning of lumened and teethed devices. Staff must thoroughly wash even items without visible soil before sterilization.
  • Staff must arrange the implantable items in the sterilization pan to maximize the sterilization cycle's effectiveness, such as disassembling all parts. If the device must be transported to the OR through a semi-restricted hallway, staff should put the implant in a rigid covered flash sterilization container.
  • Next, staff must place a chemical integrator in each pan and sterilize the implantable using a gravity cycle for 10 minutes at 270'F, unless the manufacturer specifies differently. Staff must run the appropriate Rapid Readout biological indicator (BI) with each load. Although the implant is sterilized in 10 minutes, staff must also run a one-hour hour biological readout. The device may neither be placed in the sterile field nor implanted until the BI test comes back negative. Instead, it's delivered to the OR and placed on separate table.
  • At the conclusion of the sterilization cycle, staff must verify that sterilization time, pressure and temperature protocols have been met.
  • Before releasing the device, staff must document and initial the cycle graph/computer printout and indicate the room where they're delivering the implants. They must also document the BI cycle, including any follow-up tests.

Overcoming flash sterilization limitations
"I have strong feelings about ever using flash sterilization for implants. I don't understand the need to ever flash an implant," says Outpatient Surgery infection prevention columnist Dan Mayworm. "That said, I have no quibbles with the Hopkins policy," although he says that if the policy is rigidly followed, as it should be, it doesn't save much time over traditional wrapped, high-vacuum steam sterilization.

Specifically, Mr. Mayworm praises the Hopkins policy for addressing three major problems with flash sterilization: employing the method as a last resort; requiring strict compliance with rigid cleaning and sterilization requirements; and maximizing the potential of delivering a sterile device to the OR.

"It's one thing to attain a sterile product, quite another to deliver a sterile product to the OR," he says. The reason? As long as the sterilizer works properly and staff correctly follow cleaning protocols and sterilization directions, the item will be sterile when the cycle concludes. Once staff opens the sterilizer door, however, hot air rushes out and cold, non-filtered air (along with whatever particles the air carries) rushes in to cool the wet, hot unwrapped device. That's why Mr. Mayworm recommends wasting as little time as possible getting the flashed device from the reprocessing area to the OR. When possible, he recommends a single wrap cycle or the use of rigid containers that have been validated for use in the facility's flash sterilizers.

"Having the device sit around before OR delivery increases the chance of contamination," he says. "It makes no sense to hold the implant, waiting around for the BI results. The BI tells you you've run an acceptable cycle in the sterilizer, which is rather meaningless once you expose the flashed item. The key to a successful outcome is training doctors and staff to follow rigid, proven procedures that eliminate the need for ever having to flash implants."

References
1. Kyi MS, Holton J, Ridgway GL. "Assessment of the efficacy of a low temperature hydrogen peroxide gas plasma sterilization system." J Hosp Infect. 1995 Dec;31(4):275-84.
2. Spry, C. "Low-temperature hydrogen peroxide gas plasma-atomic age sterilization technology." Today's Surg Nurse. 1998 Jan-Feb;20(1):25-8.
3. Geiss HK. "New sterilization technologies-are they applicable for endoscopic surgical instruments?" Endosc Surg Allied Technol. 1994 Oct;2(5):276-8.
4. Adler S, Scherrer M, Daschner FD. "Costs of low-temperature plasma sterilization compared with other sterilization methods." J Hosp Infect. 1998 Oct;40(2)125-34.
5. Penna TC, Ferraz CA, Cassola MA. "The persterilization microbial load on used medical devices and the effectiveness of hydrogen peroxide gas plasma against Bacillus subtilis spores." Infect Control Hosp Epidemiol. 1999 Jul(20(7):465-72.
6. Li CS, Wang YC. "Surface germicidal effects of ozone for microorganisms." AIHA J (Fairfax, Va). 2003 Jul-Aug;64(4): 533-7.

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