Medical devices steam sterilisation

The principle of steam sterilisation for medical devices, pharmaceutical products and utensils is based on heat transfer by hot condensing steam under pressure. The steam condenses in the autoclave to pure water, releasing at that moment its heat content. This is a very effective means of heat transfer. Furthermore, the mechanism of inactivation by saturated steam (denaturation of proteins) is also very effective. Therefore, steam sterilisatirai in an autoclave is the preferred method for medical devices, utensils and some pharmaceutical products. It is of critical importance that the steam in a steam autoclave is completely saturated and not superheated, because only then the sterilisation is effective. For the details of steam sterilisation reference is made to other textbooks and guidance, such as [4,5]. The pressure of saturated steam at different temperatures is shown in Table 30.2. 

It is important that either the steam can penetrate into the object to be sterilised (medical devices or utensils in dedicated steam sterilisation packaging), or that the object in a closed container contains water (content of an ampoule, bottle, vial or plastic bag with aqueous solution). 

Process Description of Steam Sterilisation for Medical Devices... 

The packaging of medical devices after cleaning and before sterilisation should protect the content (against contamination) as well as (during sterilisation) allow for removal of air and penetration of steam. The classical and most often used packaging material is sterlisation paper. Instrumentation kits are wrapped in sheets of sterilisation paper or non-woven materials that are subsequently sealed with sterilisation tape, which usually has a sterilisation indicator. 

Because of the fundamental difference between sterilisation of finished medicinal products and medical devices (temperature-controlled hot water process vs. -pressure-controlled steam process), both processes have their own validation directive. Most countries have then-own National legislation and standards on sterilisation and validation. International ISO standards are always useful or are implemented and commented in the own country for steam sterilisation see [6]. 

Gas sterilisation is performed with ethylene oxide or hydrogen peroxide gas. Sometimes peracetic acid is used, but this method is too specialised to mention here in detail. In the past (fi-om 1940) formaldehyde was used as well, but this method is rarely used anymore. Gas sterilisation is used for sterilisation of medical devices and of surfaces of pharmaceutical containers where the contents are too sensitive to the high temperature of steam sterilisation and/or cannot withstand radiation sterilisation. 

Cyanoacrylates are quite widely used for the bonding of medical devices (especially small component parts, see Figure 9.5) as these adhesives show excellent adhesion to many of the plastics used in this industry. In this industry component parts are sterilised and, whilst cyanoacrylates will withstand gamma sterilisation and ethylene oxide (EtO) sterilisation processes, they would not generally be recommended for applications where the component assembly will be steam autoclaved. 

PES is undergoing extensive trials for use in medical equipment where its ability to withstand repeated steam or dry heat sterilisation or chemical sterilisation is important The use of PES for parts of respirators, anaesthetic equipment, and flow control devices are all being actively developed ... 

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