☻Aseptic technique

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ASEPTIC TECHNIQUE GUIDE

Terminology

Sepsis: - 

Presence of living pathogenic microorganism within the tissue

Sterile: -

Complete absence microorganisms

Sanitize: -

Reduction of the number of microorganisms to a safe level

Antiseptics: -

They are drugs, substances, or chemicals that applied topically to the living tissue to kill microorganisms

Disinfectants: -

They are drugs, substances, or chemicals that applied to inanimate objects or non-living surfaces to kill microorganisms

Characters of Ideal Antiseptic or Disinfectant

1-Safe, not absorbed by the skin of the animal, and neither harmful to living tissue nor corrosive for non-living surfaces

2-Highly effective against all microorganism at low concentration

3-Effective in presence of organic matter                                

4-Soluble in water, stable, penetrate tissue surface                  

5-Incompatible with other drugs

6-Fast acting with long duration

7-Non staining and odorless

Mechanism of Action of Antiseptics and Disinfectants

1-Coagulation of bacterial cell protein

2-Alteration of cell wall permeability leading to loss of essential substances or entry of unneeded substances

3-Interference with enzymatic system 

METHODS OF STERILIZATION

I-PHYSICAL STERILIZATION

Physical sterilization by dry or moist heat is the most commonly used method of sterilization

1-Dry heat (baking or flaming)

A-Direct flaming: -

Advantages: -

Simple, easy, and cheap method

Disadvantages: -

Dullness of sharp instruments

B-Hot air Oven: -

It is an effective method of sterilizing metal instruments and glassware (1-2 hours at a temperature over 200°C)

Advantages: -

Excellent method of sterilization

Disadvantages: -

1-High cost        

2-Unsuitable for sterilization of plastic or rubbery materials

2-Moist heat

It is a method commonly used for sterilizing instruments, clothes, suture materials, and any other utensils

A-Boiling: -

Boiling can be performed by using distilled water (to which sodium carbonate 2 % can be added) at 100°C for at least 20 minutes. It can be used for sterilization of suture materials (silk), syringes and needles

Advantages: -

Simple, easy, and cheap method

Disadvantages: -

It is not recommended for aseptic surgery since;

1-It is not effective in killing bacterial spores

2-It tends to dull sharp instruments

B-Steam under pressure sterilization (autoclaving): -

An autoclave is a self-locking machine that sterilizes with steam under pressure. Sterilization is achieved by the high temperature of steam under pressure. The high pressure also ensures saturation of wrapped surgical packs.

All instruments must be double wrapped in linen or special paper or placed in a special metal box equipped with a filter before sterilization. 'Flashing' is when an instrument is autoclaved unwrapped for a shorter period of time. Flashing is often used when a critical instrument is dropped

Autoclave Settings

Temperature

Pressure (PSI)

Time (min)

General Wrapped Items

120°C (250°F)

20

30

Bottled Solutions

120°C (250°F)

20

30

Flashing

131°C (270°F)

30

4-7

Advantages: -

It is a good penetrating, bactericidal and economical method

Disadvantages: -

1-It dulls sharp instruments                                     

2-It scorches fabrics

3-It may leave packs wet                                        

4-It will not sterilize grease or oil materials

II-COLD (CHEMICAL) STERILIZATION

Glutaraldehyde (Cidex) that is bactericidal, fungicidal, viricidal, and sporicidal and it is the most common disinfectant, usually 3 hours exposure time is needed to destroy spores. Instruments must be dry before immersion.

1-Oxidizing agents

These substances liberate nascent oxygen and so it is affected by the presence of organic matters

A-Halogens (Chlorine): -

B-Peroxides (H2O2): -

C-Potassium permanganate: -

2-Reducing agents

An example of reducing agent is formalin, which is formaldehyde 40% in water. It is not affected by organic matter and has the ability to form toxoid with bacterial toxins. It can be used as urinary antiseptic in acidic urine, as it is released from hexamine. It can be used in the form of gas when mixed with Potassium permanganates.

3-Heavy metal

A-Mercury salts: -

i-Mercuric chloride used as skin antiseptic

ii-Mercuric nitrate and oxide used as eye ointment

iii-Bin iodide of mercury % in lanoline used as blister or counter irritant

iv-Organic mercury compounds act as disinfectants by liberating mercury ions as thiomersolates for wounds, skin, and instruments

B-Silver salts: -

Silver nitrate is an astringent that can be used for corneal ulcers

C-Copper salts: -

Copper sulfate % can be used as astringent fungicidal and germicidal

D-Zinc salts: -

Like zinc sulfate, zinc oxide, and zinc chloride

E-Arsenical salts: -

Arsanilic acid can be used orally as intestinal antiseptic

4-Acid and alkalis

Caustic soda and quick lime can be used for disinfection of buildings but they are corrosive

5-Alcohols

Ethyl alcohol 70% can be used for skin disinfection

6-Phenol and its derivatives

A-Phenol: -

It can be used as 2% solution for disinfection, or it can be used as it is for corneal ulcers

B-Crysol: -

Used as 0.5.  % as intestinal antiseptic

C-Lysol: -

It can be used for disinfection of non-living objects

D-Chloroxylenol (Dittol®): -

It is none irritant antiseptic for intact skin in concentration of 2%

E-Picric acid: -

It is used as antiseptic for burns

7-Alcohol-formalin mixture (equal volumes) or organic dyes (acriflavin)

They are used for sterilization of optical instruments and catheters

III-GAS STERILIZATION (ETHYLENE OXIDE GAS, EO)

It is a colorless gas, very toxic and flammable with odor similar to ether and its use requires special equipment. It is used for heat sensitive instruments like plastics, suture material, lenses and finely sharpened instruments

Advantages: -

1-It is both bactericidal and sporicidal

2-Their penetration and effectiveness at relatively low temperatures make them useful for sterilizing surgical supplies made of leather, wool, paper, plastics and other materials that would be damaged by the heat

3-It sterilizes electrical and optical equipment effectively and do not dull instruments

Disadvantages: -

Materials that have been sterilized with Ethylene Oxide must be aerated for 1 to 7 days, depending on the material, otherwise residual gas may diffuse from it and irritates living tissues.

In order to perform aseptic surgery technique, strict measures should be performed to prevent contamination of the surgical wound, and in order to achieve this, the operating room, the surgery packs, the patient, and the surgeon must follow rigid routine procedures to insure such aseptic surgery technique.

IV-RADIATION STERILIZATION

High energy ionizing radiation destroys microorganisms and is used to sterilize pre-packed surgical equipment. It is used for instruments that can't be sterilized by heat or chemicals. Radiation sterilization is being promoted as an alternative to ETO sterilization. Care needs to be taken because not all materials can be irradiated successfully. Currently it is used by manufacturers, but not used in veterinary hospitals. Common sources of radiation include electron beam and Cobalt-60

PREOPERATIVE PREPARATION

I-OPERATING or SURGERY ROOM

Control of contamination starts with construction of the surgery room to limit or to prevent contamination as much as possible

1-Construction of operating room

It is preferred to be isolated. It must be subjected to rigid policies. It should be constructed with one exit (one door) in order to restrict unnecessary movement of personnel as well as to minimize the opening and closing of doors during surgery. The operating room should be in direct connection with the surgery preparation room and the surgical scrub area (used for preparation of surgical patients and used as post-surgical recovery room).

The operating room should be supplied with good lighting facilities, casting beds, operating tables, instrument carts, and trolleys. Permanently installed hydraulic operating table is likely to be used in large animal surgery room. When circumstances entail that surgery must be carried out in an open yard, the clinician must select the site most suitable for the procedure. If a minor surgical procedure is to be carried out on the standing position and measures should be taken, to secure the animal either in stanchion or in a box stall. When recumbency is mandatory, consideration must be given to the area or location in which the surgery will be performed preferably in a grass field or paddock in which a casting bed is required. The major drawbacks to this are the saturation of air with dust as well as the insect problems.

2-Surgery room cleanliness

Cleaning of the surgery room should be done by well-trained housekeeping personnel. Daily cleaning consists of damp dusting of all flat surfaces, lights, and furniture approximately one hour before surgery. Weekly cleansing routines must be established and it consists of whipping down of walls and ceilings with a germicidal cleaning solution. Cabinets and other operating room equipment should be cleansed. Operating tables should be cleansed after each operation with germicidal solution. Buckets should be carefully cleansed and disinfected. After surgery, areas contaminated by organic debris like blood and other body fluids should be cleaned with detergent and disinfectant

II-SURGERY PACKS

All materials and equipment used in a surgical procedure or entering the operative field must be sterilized. Instruments and materials must be clean prior to sterilization. Post-operative cleaning to remove blood can be facilitated by soaking all materials and instruments in cold water and detergent. Gowns, drapes and other fabrics must be laundered. After drying the equipment and supplies they are arranged for pack preparation. The instruments and materials included in a pack vary with the surgical procedure or with the surgeon preference. All materials are packed either in sterilizing drums or wrapped with clean towel and double thick paper without contamination. Autoclaving is the most widely used method of surgical pack sterilization. Properly wrapped sterilized packs will remain sterile for up to 6 months if properly stored. Packs stored in sealed plastic bags remain sterile for up to one year.

The Instruments:

Instrument trays are presented, with the assistant carefully removing the paper wrap or cover and then the surgeon places the instruments on the sterile wrapped instrument stand. Instruments should preferably be sterilized by one of the first two methods listed below:

1-Autoclaving by steam, 750 mm/Hg at 120°C for 30 minutes or at 131°C for three minutes for non-packed instruments, or for a shorter time in higher vacuum or higher pressure autoclaves

2-Gas sterilization by ethylene oxide followed by air drying for several days to avoid diffusion of residual gases from the materials into animal tissues – some acrylic plastic materials, polystyrene and certain lensed instruments may be damaged during this process. Note that ethylene oxide is cancerigenic.

3-Cold (chemical) sterilization in commercially available solutions, however prolonged immersion is necessary. Health and safety problems exist with products such as glutaraldehyde (Rapidex® Arnolds Vet).

4-Simple boiling of instruments is a poor, slow and tiresome means of sterilization particularly liable to cause damage. The minimal period of boiling is 30 minutes, longer at altitudes over 300 minutes. Addition of alkali to the sterilizer increases bactericidal efficiency and boiling time may be safely reduced to 15 minutes. Corrosion is avoided by the addition of 0.5–1% washing soda (Na2CO3), while accumulation of lime in serrations or joints is removed by leaving instruments in 5% acetic acid overnight, then brushing off

III-PREPARATION OF THE PATIENT

1-Preparation of the operative site

Bovine surgery involving regions where adequate skin preparation is feasible (i.e. with avoidable microbial contamination of tissues or sterile materials) should be performed under aseptic conditions. Instruments and cloths should be sterile. Preparation of operative field (e.g. flank) includes;

1-Close clip wide area, minimum 60 cm cranial-caudal and 90 cm vertically (Preferable to shaving)

2-Alternatively shave operative field after application of disinfectant, soap and water (Schick model razor is suitable)

3-Wash area with soap and water twice, then scrub it with povidone iodine solution (e.g. Betadine®), dry it off, and finally wash with 70% alcohol and rescrub

4-Repeat this procedure three times before re-spraying with diluted povidone iodine solution

5-Place sterile towel on suitable flat surface for instruments, use sterilized gauze swabs, instruments and suture materials, and sterile gloves

2-Draping the patient

Large impervious sterile towels or disposable drapes (rubber or plastic) are useful for placing on the site. The basic set of drapes pack consists of 4 pieces, each approximately 120x90 cm, and one main drape 200x250 cm with a rectangular window. The caudal drape is applied first, leaving a double thickness adjacent to the prepared area then the cranial drape is applied in a similar manner

The side drapes are then placed, leaving a suitable area exposed for the incision and the drapes are held in position with towel forceps. The patient and the entire operating table are then covered with the main drape that has a window that should enclose the area of the incision. The head of the patient is left uncovered for purposes of observation during surgery

IV-PREPARATION OF THE SURGEON AND ASSISTANTS

Members of the surgical team and operating room personnel should be appropriately clothed. Observation gowns and disposable shoe covers can be worn over the usual clothes of operating room personnel and others entering the operating room. Caps and masks are also necessary. Cloth flaps, masks and gowns must be laundered after each use

Preparation of the hands or hand disinfection (scrubbing up): -

The cap and mask should be worn before scrubbing commences. Before preparation of the hands for sterile surgery, the fingernails are cut short Hands are kept in contact with the disinfectant for at least five minutes. Effective hand sterilization procedures include;

1-Chlorhexidine scrub

2-Chlorhexidine 0.5% concentrate in 90% ethyl alcohol with 1% glycerine as emollient (cheapest), in which 10 ml is first applied to clean dry hands and permitted to dry, before further application and five minutes scrub-up commercially available povidone-iodine soap

3-Hexachlorophane suspension applied first dry then wet, but after scrub up (5 minutes) must be fully rinsed off (pHisoHex®, Zalpon)

Gowning and Gloving: -

The sterile gown and towel wrap or drums are opened by an assistant. The gown is lifted from the sterile wrap and held away from the table. The surgeon unfolds the gown by placing his hands in the appropriate armholes. The arms are pushed in the sleeves to the cuff. An assistant closes the neck and ties the inside waist tie. The gloves are worn and folded over the cuffs of the sleeves. Some operations need rigid aseptic precautions so that two pairs of gloves should be worn.