2014 12-22 - sterilization methods - regulation (aa)

Sterilization methods: regulation

Arti Ahluwalia

Open Source for Biomedical Engineering - OS4BME

Sterilization

Sterilization means the use of a physical or chemical procedure to destroy all microbial life including resistant bacterial endospores.

It causes denaturation of proteins, nucleic acids and components of cellular membrane.

Sterilization

The importance of sterilization :

- reduction of number of deaths- improvement of surgical techniques- reduction of epidemic diseases- improvement of health conditions

Sterilization

Sterility assurance level (SAL) is the probability of a single unit being non-sterile after it has been subjected to sterilization:- 10-6 for tools operating on internal tissue (surgical tools, implantable devices);- 10-3 for tools operating on external tissue.

N = number of microorganismsN0 = initial number of microorganismsT = timeD = decay constant

Sterilization

Sterilization methods

Physical methods:● dry heat● steam sterilization● gamma ray● UV rays● filtration

Chemical methods:● ethylene oxyde (EtO)● glutaraldehyde and formaldehyde● hydrogen peroxide● paracetic acid

Sterilization: physical methods

Dry heat: can be done by baking and flaming.Mainly used for metals and ceramics; practical and cheap, but takes a long time.


Steam sterilization: in AutoclaveUsed for heat-stable materials(generally not plastics).


Gamma Radiation (usually Cobalt-60 or caesium-137)Commonly used in biomedical device sterilization, it does not produce radioactivity on the objects.Very efficient butexpensive method.


UV sterilization (wl = 230-280 nm, typically 254 nm)Mainly used to sterilize water, air fluxes and surfaces.

Cheap and fast system, but no penetrating power and not usable with plastics.


Filtration for liquid not tolerant to heat, rays, chemical agents.

Membrane filters present pores with diameters of μm or nm to effectively remove microorganisms.

Sterilization: chemical methods

Ethylene Oxyde (EtO): highlypenetrating and efficient.

Generally used to sterilize PVC, rubbers and devices such as endoscopes.

Formaldehyde is used to preserve anatomic specimens and to prepare viral vaccines.


Glutaraldehyde and Formaldehyde: separately and in solution. Method expensive and of low durability and taking long time (>20h).

Glutaraldehyde is used for medical devices such as endoscopes; objects sterilized by it can not be packed.


Hydrogen Peroxide is a strong oxidant.It is used for heatsensitive articles,disinfecting soft contactlenses and endoscopes.

Peracetic acid shows a rapid action against all microorganisms (t < 30min). It is used for surgical and dental instruments.

Sterilization: regulations & standards

Differences between standards and regulations


It is not easy to understand which are the rules to respect in designing and creating sterilization devices.


National regulation agencies

International regulation agencies for regulatory harmonization in a specific area

International regulation agencies for global harmonization

WHO, Harmonization Task Force (GHTF) , International Medical Devices Regulatory Forum (IMDRF)


Goals: creating occasions to exchange information about regulatory on medicine and biomedical fields to reach a harmonization system.

In their sites there are sections with documentation available.

www.amrh.org & www.pahwp.org


Non-governmental membership organization

The world's largest developer of voluntary International Standards

Members from 165 countries and 3,368 technical bodies to take care of standard development


www.iso.org


ISO Members


About sterilization of health care products...

Over 60 ISO rules!!!


Typical ISO standard rule structure:

I. Definition of application field

II. Definition of technical terms used in the document

III. Regulatory references

IV. Technical regulations

V. Technical tables and appendixes


Choosing is fundamental- to save time in consulting- ISO rules are not free...


There is still a long way to go...


References

1. Guideline for Disinfection and Sterilization in Healthcare Facilities – CDC2. www.who.int3. www.iso.org4. Ultraviolet Germicidal Irradiation Handbook – W. Kowalski5. Final Report: Effectiveness of UV Irradiation for Pathogen Inactivation in Surface Waters – EPA (USA)


Thank you for your a t tent ion!