EFHSS Questions and Answers - Question Q00011

Good morning

I'm looking for information on sterilization method Kindly advise on Advantages and disadvantages of Ethylene Oxide, Formaldehyde and Peroxide.

Thank you very much
Olivier Peres

Good day,

One advantage of EtO is that it has a very high compatability with many materials.

Disadvantages of EtO include its toxicity: it is carcinogenic and mutogenic to mammals. EtO's toxicity mandates that very long aeration times must be adhered to, resulting in turnaround times from start of the cycle to the safe use point can exceed 16 hours. EtO is not detectable by the human nose at levels below about 600-700 ppm, but 50 ppm exposure has been linked to increased cancer levels in employees. This means that mechanical monitors must be used. EtO can burn flesh when residuals are left on items due to the item being not properly aerated.

Liquid EtO can cause frost bite on skin. Any water left on items sterilized can interact with the EtO forming Ethylene Glycol (Automobile Radiator Antifreeze) which is poisonous to mammals.

EtO is flammable and explosive. In the past this was addressed by mixing EtO and Freon, but the use of Freon has been banned due to its negative effects on the earths ozone layer. Electical devices must have their batterys removed prior to sterilization in 100% EtO to reduce the explosion dangers.

Hydrogen Peroxide such as used in the Sterrad system, is a very fast low temperature sterilization technique, and at my institution, the turnaround time for Sterrad sterilized items is shorter than steam sterilized items. H2O2 can irritate mucous membranes, so the permitted exposure limits are similar to the limits for EtO, but EtO's limits are based on its carcinogenicy and mutogenic properties rather than irritation. The Sterrad system requires no venting, no steam lines, etc. It is on wheels, and can be moved to any spot with an electrical outlet.

A disadvantage to the Sterrad system is its limited ability to penatrate long narrow lumens. This disadvantage is partly offset by the use of boosters that attach to the lumens. The Sterrad is not approved in the USA by the FDA for sterilizing long flexible endoscopes such as sigmoidoscopes for a few reasons (such as the requirement that it sterilize scopes that have not been cleaned and are full of fecal matter), but this lack of USA FDA approval does not effect European users.

Another disadvantage to the Sterrad system is that it cannot be used to sterilize organic materials such as cellulose (Cotton, paper, etc) and so cloth and wood fiber based wrappers cannot be used. Kimberly Clark makes several wrappers that are compatable with Sterrad, EtO, and steam techniques. As you might note, I am a fan of the Sterrad system, and I use 4 of these at my institution. I can reprocess an instrument set in 75 minutes using the Sterrad system, so the same instrument tray can be used for 4 or more surgical procedures in a day. This has allowed me to reduce the number of instrument sets I have on hand.

Formadehyde is a very old technology that is rarely used today. I recall reading (maybe 15 years ago) that it was not an effective sterilization technique and the author was recommending it only be used for furniture.

Hope this helps address your concerns,
Pete Bobb, Saudi Arabia

Bon Jour Olivier,

Mr. Bobb's admitted bias towards the Sterrad system, warts and all unfortunately is hardly an answer to your question. The obvious requirements for a good sterilant is it's compatibility with the materials to be processed and its ability to penetrate the types of items processed in order to ensure sterility, and as stated by Mr Bobb this is a major plus with EO. This may account for the fact that more than 50% of all single use medical devices manufactured are processed with EO. Obviously the need for aeration increases cycle time but as all gas systems require Biological indicator testing and product really should not be released until the result of the BI is availabe (48hrs in the case of peroxide).
EO is of course toxic, so is Hydrogen peroxide and so is Formaldehyde and perhaps the following might help in understanding the relationships:

I am particularly impressed with Mr. Bobb' s assertion that "STERRAD IS NOT APPROVED BY THE FDA FOR ......... BUT THIS LACK OF FDA APPROVAL DOES NOT EFFECT EUROPEAN USERS"!! Does this suggest that FDA consider that patients in the USA should be afforded more or different protection than their European counterparts? There is also reference to the use of booster systems with the Sterrad device (which I understand require a "gas tight fit"?) these too are, as far as I am aware, not permitted in the USA but are offered in Europe, same logic?

The bottom line is that a properly installed sterilizer, operated by trained and skilled technicians, in accordance with a suitable quality system, and subjected to preventative maintainence programmes offers nor risks to the operator, the patient or the envirnoment. In my opinion at least EO offers the most cost effective, versatile in terms of capacity, penetratrability, material compatibility and is a perfectly safe low temperature system where one is needed.

Regards
Pat Dillon
3M Sterility Assurance

Dear Olivier,

LTSF - Low Temperature Steam Formaldehyde sterilization uses low temperature steam (55 - 80 °C) and formaldehyde. It is suitable method for sterilization of all kind of thermo-sensitive instruments and applicable for sterilization of instruments, including long and narrow dead-end cavities. Formaldehyde is absorbed by medical materials and desorption sequences aimed for residue reduction in goods are included in the process. No airing of sterilized goods external from the sterilizer chamber is needed.Sterilizers are available that can be used for both low temperature formaldehyde sterilization and (as back up) for normal steam sterilization processes. This avoids the necessity of a dedicated low-temperature sterilizer There is a growing interest, because of new European standard EN 14180 published on July 2003 for formaldehyde sterilization.
European standards of formaldehyde sterilization regarding biological indicators, chemical indicators and packaging materials are available. Their ISO versions are under preparation. As you can understand from the above explanations it is not an old technique (15 years ago). There are several manufacturers in Europe like Getinge, Matachana, MMM, Cisa for formaldehyde sterilisers. You can find detailed information from their web pages.

Best Regards
Vecihe Ozek
Turkey

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