Sterilization And DisinfectionInSurgical Practice
During surgery, the body’s major defense against infection,the skin is broken and the inner surfaces of thebody are exposed to the environment. Every attemptmust therefore be made to prevent bacteria from enteringthe wound (asepsis) and to eliminate them if theyhave already entered (antisepsis).Asepsis Asepsis covers all those procedures designed to reduce the risk of bacterial (or other, e.g. fungal or viral) contamination, e.g. through the use of sterile instrumentsand the gloved “no touch” technique.
Asepsis can be ensured by-The use of sterile devices, materials and instrument.-Creating an environment that is poor in microbes.
AntisepsisAntisepsis relates to the removal of transient microorganisms from the skin and a reduction in the resident flora.Techniques may be applied to eliminatecontamination (bacterial, viral, fungal and others) by means of sterilization and disinfection
Sterility Sterility is a microbiologically germ-free state of materials and items. This means that they are free from allkinds of pathogenic and apathogenic microorganisms,including latent and resting forms, such as spores.
Sterilization Elimination and inactivation of pathogens this involves the removal of viable microorganisms (pathogenic and a pathogenic microorganisms, including latent and resting forms such as spores ) which can be achieved by different physical and chemical means….
Autoclaves Autoclaves are highly effective and inexpensive tools of sterilization. Their effectiveness is based on the fact that the temperature of steam under pressure exceeds 100 °C. At 108 kPa it is 121 °C (vacuum has to be created).When the pressure is 206 kPa, the temperature of steam is 134 °C.The time needed for sterilization at 121 °C is 20 min and at 134 °C is 10 min.
To be effective against viruses and spore forming bacteria the steam must be in direct contact withthe materials. The effectiveness can be checked via the color change of the indicator tape placed on the packing. Disadvantage : autoclaves are unsuitable for heat-sensitive objects.
Gas sterilization by ethylene oxide This agent is highly penetrative and active against bacteria,spores and viruses. It is suitable for heat-sensitiveitems.Disadvantages: it is flammable, toxic and expensive,and leaves toxic residues on sterilized items.
Sporicidal chemicals – cold sterilizationSporicidal chemicals are often used as disinfectants, butcan also sterilize instruments if utilized for a prolongedperiod.Advantages : Inexpensive and suitable for heat-sensitive items. Disadvantages They are toxic and irritants.The most widely used liquid sporicidal chemical is 2% glutaraldehyde (Cidex). It is able to kill most bacteria andviruses within 10 min (spores can survive for 3 h).
Irradiation Gamma rays and accelerated electrons are excellent for sterilization. They are mostly used for industrial purposes,e.g. the sterilization of disposable items (plasticsyringes and needles) and materials (bandages) ratherthan sterilization in hospitals.
Disinfection The reduction of the number of viable microorganisms by destroying or inactivating them on living or inanimate (nonliving) surfaces. It can be achieved with chemicals (disinfectants) such as glutaraldehyde, formaldehyde, quaternary detergents, etc. Some of these disinfectants are sporicidal, but theyshould generally not be used for sterilization becausemost items need a very long time (up to 10 h or more) ofsoaking in order to render them sterile.
Low-temperature steam Most bacteria and viruses are killed by exposure tomoist heat. This is usually achieved with dry saturatedsteam at 73 °C, applied for more than 10 min. This procedure is effective, reliable and suitable for instrumentswith a lumen. It is unsuitable for heat-sensitive items.
Chemical disinfectants These are suitable for heat-sensitive items, but are lesseffective than heat. The goal is to destroy microorganismsby chemical or physicochemical means. Differentorganisms vary in their sensitivity to them: Gram-positive bacteria are highly sensitive. Gram-negative bacteria are relatively resistant. Clostridial and Mycobacterial species are very resistant. Slow viruses are highly resistant. : The chemicals used includeclear soluble phenolics, hypochlorites and alcohols
Preparation of the skin before the operation The skin harbors resident flora (these bacteria cause no harm unless drawn into the body through a break in the skin, e.g. Staph. epidermidis) and transient flora(acquired from a contaminated source); the latter includesany type of bacterium that can live on the skin.
Bathing It is not unequivocal that bathing lowers the germ countof the skin, but as regards elective surgery preoperativeantiseptic showers/baths are essential. Special attention is paid to the operative site. This should be bathed with antiseptic soap (chlorhexidine or quaternol) the evening prior to the day of operation.
Shaving This makes the surgery, the suturing and the dressingremoval easier. It must be done immediately priorto the operation, with the least possible cuticular /dermal injury; in this case, the wound infection rate isonly 1%. The infection rate rises to > 5% if shaving isperformed more than 12 h prior to the surgery Clippers or depilatory creams reduce infectionrates to < 1%.
Preparation of the skinThis is performed immediately before the operation.Disinfectants are applied to the skin: 70% isopropanol (this acts by denaturing proteins; itis a bactericidal) short-acting; 0.5% chlorhexidine (a quaternary ammonium compound,which acts by disrupting the bacterial cellwall, it is bactericidal, but does not kill spore-formingorganisms; it is persistent, with a long durationof action (up to 6 h), and is more effective againstGram-positive organisms); 70% povidone–iodine (Betadine, which acts by oxidation/substitution of free iodine; it is bactericidaland active against spore-forming organisms;
Isolation of the operating area (draping) After the skin preparation, the disinfected operatingarea must be isolated from the nondisinfected skinsurfaces and body areas by the application of sterilelinen textile (muslin) or sterile water-proof paper(nonwoven) drapes and other sterile accessories/supplements.The isolation prevents contamination originatingfrom the patient’s skin. Draping is performedafter the surgeon has donned gown and gloves. The use of sterile self-attaching synthetic adhesives(affixed to the disinfected operating area) is questionable,because these can help residual bacteriacome to the surface, due to the increased perspirationduring the operation.
As the deeper layers of the disinfected skin alwayscontain residual bacteria, the skin can not betouched either by instruments or by hand. The isolation can be performed with disposable sterilesheets which are attached to each other wherethey cross by self-attaching surfaces. Nondisposable,permeable linen textiles are fixed with specialBackhaus towel clips; usually four Backhaus clipsfix the sheets. In the draping routine, four towels areplaced around the immediate surgical site.