Different Methods of Surgical Instrument Sterilization

How surgical instrument Sterlized :

All instruments and other equipment used to perform surgery must be sterilized prior to use.Instruments, with or without an instrument tray, may be packed inside a folded cloth or paper wrap and sealed with autoclave tape for steam sterilization. A sterilization indicator is placed inside the pack. Instruments may be packed in a self sealing envelope with one side made of clear plastic. Referred to as peel packs, these may be used for steam or gas sterilization. The sterilization indicator is part of the package.

     Methods of Sterilization:  

• Steam Sterilization  (Autoclave) :

Steam or autoclave sterilization is the most common method of instrument sterilization. Instruments are placed in a pack and exposed to steam under pressure. A sterilization indicator such as autoclave tape or other indicator strip is used to clearly identify instruments that have been sterilized.Never lock an instrument during autoclaving. It will not be sterile as steam cannot reach the metal to metal surfaces. The

instrument will develop cracks in hinge areas because of heat expansion during the autoclave cycle.Do not over load the autoclave chamber as pockets may form that do not permit steam penetration. Place towel on bottom of pan to absorb excess moisture during autoclaving. This will reduce the chances of getting wet packs. Make sure the towels used in sterilization of instruments have no detergent residue and are neutral  if

immersed in water. This can be a real problem as laundries frequently use inexpensive but high detergents and do not properly rinse out or neutralize those detergents in the final wash/rinse cycle.

• Ethylene Oxide:

Ethylene oxide gas may be used to sterilize items that may not be exposed to high temperature and or steam. Ethylene oxide is highly toxic. Items sterilized with ethylene oxide must be aerated before use to allow the toxic gas to dissipate. A sterilization indicator  is used to clearly identify instruments that have been sterilized. Most peel packs have a built in indicator for both steam and gas sterilization. The two most important ethylene oxide sterilization methods are:

1.   The gas chamber method 

2.   The micro-dose method. 

 EtO has traditionally been delivered by flooding a large chamber with a combination of EtO and other gases used as dilutants (usually CFCs or carbon dioxide). This method has drawbacks inherent to the use of large amounts of sterilant being released into a large space, including air contamination produced by CFCs and/or large amounts of EtO residuals, flammability and storage issues calling for special handling and storage, operator exposure risk and training costs.

• Dry Heat Sterilization:

Dry heat can be used to sterilize items, but as the heat takes much longer to be transferred to the organism, both the time and the temperature must usually be increased, unless forced ventilation of the hot air is used. The standard setting for a hot air oven is at least two hours at 160 °C (320 °F). A rapid method heats air to 190 °C (374 °F) for 6 minutes for unwrapped objects and 12 minutes for wrapped objects.Dry heat has the advantage that it can be used on powders and other heat-stable items that are adversely affected by steam (for instance, it does not cause rusting of steel objects)..

• Boiling  Sterilization: 

Boiling in water for fifteen minutes will kill most vegetative bacteria and inactivate viruses, Boiling does kill most vegetative microbes and viruses, it is useful for reducing viable levels if no better method is available. Boiling is a simple process, and is an option available to most people, requiring only water, enough heat, and a container that can with stand the heat; however, boiling can be hazardous and cumbersome.

• Chemical sterilization:

Chemicals are also used for sterilization. Although heating provides the most reliable way to rid objects of all transmissible agents, it is not always appropriate, because it will damage heat-sensitive materials such as biological materials, fiber optics, electronics, and many plastics. Low temperature gas sterilizers function by exposing the articles to be sterilized to high concentrations of very reactive gases (alkylating agents such as ethylene oxide, and oxidizing agents such as hydrogen peroxide and ozone). Liquid sterilants and high disinfectants typically include oxidizing agents such as hydrogen peroxide and peracetic acid and aldehydes such as glutaraldehyde and more recently o-phthalaldehyde. While the use of gas and liquid chemical sterilants/high level disinfectants avoids the problem of heat damage, users must ensure that article to be sterilized is chemically compatible with the sterilant being used. In addition, the use of chemical sterilants poses new challenges for work place safety. The chemicals used as sterilants are designed to destroy a wide range of pathogens and typically the same properties that make them good sterilants makes them harmful to humans.