Dressings

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Chapter: Pharmaceutical Microbiology : Sterile Pharmaceutical Products

Dressings and surgical materials are used widely in medicine, both as a means of protecting and providing comfort for wounds and for many associated activities such as cleaning and swabbing. They may or may not be used on areas of broken skin.


DRESSINGS

 

Dressings and surgical materials are used widely in medicine, both as a means of protecting and providing comfort for wounds and for many associated activities such as cleaning and swabbing. They may or may not be used on areas of broken skin. If there is a potential danger of infection arising from the use of a dressing then it must be sterile. For instance, sterile dressings must be used on all open wounds, both surgical and traumatic, on burns, and during and after catheterization at a site of injection. It is also important to appreciate that sterile dressings must be packaged in such a way that they can be applied to the wound aseptically.

 

Dressings are described in the British Pharmacopoeia (2010). Methods for their sterilization include autoclaving, dry heat, ethylene oxide and ionizing radiation. Any other effective method may be used. The choice is governed principally by the stability of the dressing constituents to the stress applied and the nature of their components. Most celluloses and synthetic fibres withstand autoclaving, but there are exceptions. For instance, boric acid tenderizes cellulose fibres during autoclaving, and dressings containing waxes cannot be sterilized by moist heat. Certain constituents are also adversely affected on exposure to large doses of gamma radiation. Examples of dressings that are required to be sterile are listed in Table 22.2, together with other dressings and materials that may be sterilized when required.

 


 

A very important aspect of the production of dressings is packaging. The packaging material must allow correct sterilization conditions (e.g. permeation of moisture or ethylene oxide), retain the dressing in a sterile condition and allow for its removal without contamination prior to use. All dressings intended for aseptic handling and application must be double wrapped. For steam sterilization they may be individually wrapped in fabric, paper or nylon and sterilized in metal drums, cardboard boxes or bleached Kraft paper. The choice of method also determines the design of the autoclave cycle. Providing that adequate steam penetration is assured, dressings may be sterilized in downward displacement autoclaves which rely on displacement of air by steam. However, high prevacuum autoclaves in which virtually all the air is removed before the admission of steam are much more commonly employed. This method ensures rapid heating up of dressings, reduces the time needed to achieve sterilization (e.g. 134 °C for 4 minutes) and shortens the overall sterilization cycle.

 

A recent development is the use of spray-on dressings. A convenient type is an acrylic polymer dissolved in ethyl acetate and packed as an aerosol. This should be self-sterilizing. The film after application is able to maintain the sterility of a clean wound for up to 2 weeks. However, they can only be used on clean, relatively dry wounds.


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