Sterilisation of dressing materials, operating sheets and suturing materials

Stage 1 - presterilisation. Dressing materials include gauze balls, towels, pack, and swabs. They are used during operation and dressing mainly for keeping the wound dry, stopping bleeding, for drainage or for packing the wound. Dressing material is prepared from gauze and cotton wool and rarely from viscose and linen. They have to have the following characteristics:

1) they should be biologically and chemically inert and void of any negative effects on wound healing;

2) they should have good hygroscopic, or water absorbing, properties;

3) they should have a few free threads from outside; this will prevent pieces of thread from falling into the wound as these can act as foreign bodies in the wound;

4) they should be soft, elastic and not traumatise the wound;

5) they should be easy to sterilise without loosing its qualities;

6) they should be cheap, considering its wide use. Annually, 200 metres of gauze and 225 pieces of bandage are normally spent per a surgical bed. Appendectomy alone, for example, requires about 7 metres of gauze.

Dressing materials are prepared from gauze that has been cut into smaller sizes. They are folded in a way that the cut edges are folded inside so that the threads do not hung freely outside. Enough material is always prepared so that there is always some reserved. To facilitate easy counting during operation they are arranged in a particular order before sterilisation: 50-100 cotton wool balls in one gauze wrapper. Ten swabs tied in one pack. Operation clothes include the following: surgical gowns, towels, sheets, napkins, masks, caps, and boot-covers, which are normally made of cotton. Operation materials that are used several times (non-disposable) have to be marked and given to the laundry separately from those that are in the special bag. The gowns should not have pockets or belts. Gowns, bed sheets, napkins, towels for sterilisation are folded in rolls to make them easy to spread when using.

Stage 2 - package and preparation of materials for sterilisation. Dressing materials and operation sheets are packed in special containers (dressing boxes) (fig. 4). For the lack of such boxes they can be sterilised in thick cloth-bag.

In a universal package, the dressing box contains a set of materials for a typical minor operation (e.g. appendectomy, herniorrhaphy, phlebectomy).

In specific packages, the dressing box contains the set of materials for a specific operation (e.g. pneumonectomy, stomach resection). In a typical pack the dressing boxes contain packs of the same material (e.g. box of gowns, box of napkins, box of swabs).

The dressing box is first inspected to make sure it is in good condition, and is then lined with a sheet whose ends hang outside. Further, the dressing materials are arranged in a vertical position in sectors of packets. The materials should not be arranged too close to each other to allow for circulation of the steam. An indicator of the sterilisation regime is placed inside (maximum thermometer, a melting material, or a test tube with test-microbes), the ends of the sheet are folded to cover, and the dressing box covered and locked with a padlock. A labelled plaster indicating the type of material is pasted on the box, and after sterilisation, the date and name of the one who did the sterilisation is added.

When the items for sterilisation are packed in a bag, they should not be arranged too tight, and the bag is tied with a special metallic tie. The bag is put into another bag and tied. When it is necessary to use the sterilised materials in the bag, it is placed on a table; the nurse assistant opens the first bag and pulls it down. The theatre nurse then opens the inner bag with sterile hands and removes the sterile items from it.

Stage 3 - sterilisation. It is noteworthy that an autoclave may be used only after it has been certified and the person in charge of the autoclave needs to be qualified appropriately. Using the steam-electric steriliser, one has to follow the exact instructions and safety measures.

• The equipment must be earthened.

• Faulty equipment should never be used.

• When in use, the equipment should be under control.

• Do not add water after the equipment has been switched on.

Fig. 4. Schimmelbusch's steriliser.

After sterilisation the apparatus should be switched off, and the ventilator closed not to let any more air into the sterilisation chamber.

The cover of the sterilisation chamber is opened only when the arrow of the manometer has reached the zero mark.

Sterilisation time is counted from the time when the manometer reaches the required pressure. Dressing materials and operation sheets are sterilised for 20 minutes at 2 atmospheres (temperature 132, 9 °C).

Stage 4 - keeping the sterilised materials. After sterilisation ends the sterilisation chamber is emptied, dressing boxes are removed, all openings are immediately closed and brought to a special table for sterile materials. Dressing boxes are kept locked in a special room. With an intact dressing box dressing materials and sheets can stay sterile for 48 hours after sterilisation has completed. Dressing materials and sheets sterilised in the bag can stay sterile for only 24 hours.

Control of sterility

The sterility of the items and the working regime of the steam steriliser can be controlled either by a direct or indirect method.

Direct methods

• Inoculation of medium with a swab of the dressing material.

To inoculate medium with a swab, open the dressing box in the operating theatre, using a sterile instrument. Soak a piece of sterile gauze in normal saline which is passed several times on the material to be tested, then drop the piece of gauze into a sterile test tube and send it to the microbiological laboratory

• Bacteriological tests.

A test tube that contains reference non-pathogenic cultured microorganisms known to die, if exposed to a certain temperature, is used. Place the test tube inside the dressing box and send it to the laboratory after sterilisation is over. Absence of bacterial growth implies that the items are sterile.

The swabs should be taken from once every 10 days.

Indirect methods

• Control of sterility of materials is done each time they have been sterilised. Compounds with known specific melting points are used for this purpose: benzoic acid (120 °C), resorcinol (119 °C), antipyrin (110 °C). These compounds are kept in ampoules. They can also be put into test tubes (0, 5 g each), and closed with gauze plug. One or two ampoules are placed in between the layers of materials to be sterilised. Melting of the powdered compound into a liquid mass implies that the temperature in the box was at least as high as the melting point of the compound. If sterilisation is performed at 2 atmospheres (temperature 132, 9 °C), compounds with higher melting points are used: ascorbic acid (187-192 °C), succinic acid (180-184 °C), pilocarpine hydrochloride (200 °C), thiourea (180 °C).

Thermometry is known to be the most objective indirect methods of sterility control. In each dressing box 1 or 2 thermometers are placed in between the layers of materials to be sterilised. The readings will indicate the maximum temperatures but not the exposition time, i.e. for how long such a temperature was maintained in the chamber. Hence this method does not preclude the use of direct methods like the bacteriological test.

Suturing material

Materials from different sources (e.g. metallic brace, clips and wires) are used in sewing tissues together during operations. There are more than forty types of suturing materials: widely used are those made of silk, nylon, catgut, vicryl, metallic braces.

Both resolvable and non-resolvable threads may be used. Natural resolvable threads are made of catgut. To lengthen the resolution time of catgut, metallic compounds are impregnated into them (chromic and silver catguts). The examples of synthetic resolvablesutures are dexon, vicryl and oxylon.

Non-resolvable natural sutures include sutures made of natural silk, cotton, yarn; their synthetic equivalents are dacron, nylon, ftolon, silk, kapron, etc.

Suturing material should meet the main requirements as follows:

• have smooth level surface without causing additional damage to the tissues;

• have good manipulating qualities - slip easily through tissues;

• be elastic (sufficient elasticity prevents tissues from being pressed on and necrotized when they subsequently become oedematous);

• be firm at the knots;

• be non-hygroscopic and not swell up;

• be biologically compatible with bodily tissues and not be allergic to the body.

Breakdown of the suture and healing the wound should be simultaneous.

Wound infection rarely occurs when suturing material with antimicrobial activity is used, this is achieved by incorporating into the sutures the antibacterial compounds (e.g. letinal-silk, ftorlonov, acetate and other sutures, containing nitrofuran, antibiotics). Synthetic sutures that contain antiseptics both possess all the qualities of clean materials and cause antibacterial effect.

Sutures can be sterilised with gamma rays by manufacturers. Silk or catgut sutures in ampoules can be kept at room temperature. Metallic suturing materials (wires, clips, braces) are sterilised in the autoclave or can be boiled while cotton sutures, lavsan, kapron may be sterilised in an autoclave. Silk, kapron, lavsan, linen, cotton are sterilised by Kocher's method. Catgut is treated with iodine steam (Sitkov's method), in alcohol solution of Lugole (Gubarev's method) or in water solution of Lugole (Heinac-Claudius method). When catgut is sterilised by the Gubarev's method, it is kept in alcohol solution of Lugole. When Heinac-Claudius method is used, they are kept in 96% ethyl alcohol. Lugole's solution or alcohol should be changed each ten days; bacteriological control each time is obligatory. Silk is kept in 96% ethyl alcohol with a label showing the suture number, dates of preparation and of bacteriological testing. The alcohol should be changed every ten days and bacteriological test done simultaneously.

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