- 1 - Welcome to the fifth edition of the Dressings Times which concludes a two part series on the selection and use of dressings for the treatment of specific types of wounds. In part one, a simple classification system was described which divided wounds into four basic groups according to their ap- pearance as follows. o Black and necrotic - covered with a hard dry layer of dead skin, o Sloughy/necrotic - covered or filled with a soft yellow slough, o Clean and granulating with significant tissue loss, o Clean and low exudate (epithelialising). It was also suggested that this classification not only de- scribed four different types of wounds but also the various stages through which a single necrotic wound might pass as it heals. As the last issue of the Dressing Times identi- fied those products which could be used in the management of necrotic or sloughy wounds, this issue deals with dressings which may be applied to granulating and epithelialising wounds. Functions of a dressing Wounds which involve a degree of tissue loss and which are not closed surgically, are left to heal by secondary inten- tion. During this process, the wound cavity first becomes filled with granulation tissue which consists of a collagen network containing `ground substance', a complex mixture of proteins and polysaccharides. Once this new tissue reaches the level of the surrounding skin, epithelial cells around the margin of the wound begin to divide and gradually grow over the surface of the wound until it is completely cov- ered. If an open or granulating wound is to heal at the optimum rate, it is generally accepted that any dressing applied to it, should ensure that the area remains; o moist with exudate but not macerated, o free of clinical infection and slough, o free of toxic chemicals, particles and fibres, o at the optimum temperature for cell division to take place, o undisturbed by frequent or unnecessary dressing changes, o at an optimum pH value. In addition, the dressing should not adhere to the surface of the wound or be excessively expensive in normal use. As granulating wounds vary considerably in size, shape, and the amount of exudate that they produce, it follows that no one dressing will be suitable for use in all situations. For some wounds, a number of different products may be accept- able, with the final choice depending upon cost, availabili- ty, or the personal preferences of the user. For some other indications however, the choice of suitable products may be more restricted. Wounds with major tissue loss In the past, large open wounds such as those which are formed by the surgical removal of a pilonidal sinus, were traditionally packed with gauze soaked in hypochlorite, saline, proflavine or some other solution. This was a time consuming process that often caused much pain to the indi- vidual concerned. In 1975 however, a new treatment was reported[1] which involved the use of a silicone foam dress- ing - Silastic (Calmic). The dressing is formed in situ from two liquids which are carefully measured out in the correct proportions and mixed thoroughly before being intro- duced into the wound. The chemical reaction which takes place between the two components, results in the liberation of hydrogen gas. This causes the mixture to froth and in- crease to approximately four times its original volume be- fore it finally sets to form a soft, absorbent, open cell foam `stent' that takes up the shape of the wound and fills it completely. In use, the stent should be removed from the wound once or twice a day and washed out using a suitable antiseptic in accordance with the instructions provided by the manufacturer. Silastic foam should not be introduced into narrow sinuses or cavities which are partially con- stricted, as in these situations there is a real danger that a piece of foam will become detached and remain in the wound, leading to a foreign body reaction or the formation of an abscess. Silastic foam has been used in the treatment of many different types of wounds including decubitus ulcers and surgical wounds that have been sutured but which have subsequently broken down. At one time there was some uncer- tainty about the long term future of Silastic foam but it is now understood that this unique and valuable product will continue to be available for the foreseeable future. Recently, an alternative dressing for cavity wounds has been introduced. Intrasite Cavity Wound Dressing (Smith & Nephew), consists of small chips of hydrophilic polyurethane foam, totally enclosed within a thin, conformable plastic film pouch which is perforated to permit the uptake of wound exudate. The dressing, which is said to be highly absorbent, is produced in a range of shapes and sizes to fit different sized wounds. wounds - moderate to high exudate The products discussed above, are not generally suitable for the treatment of chronic wounds such as leg ulcers or super- ficial pressure sores that are not deep enough to be de- scribed as `cavities.' For wounds of this type, alternative materials are required and the final choice of product will be determined by a number of factors including the location and size of the wound and the amount of exudate produced. If the wound is relatively shallow but exuding heavily, an alginate sheet such as Sorbsan (Steriseal), Kaltostat (Brit- cair) or Tegagel (3M) may be of value. The dressing is sim- ply placed over the wound and covered with an absorbent pad. Alternatively, a new composite alginate dressing - Sorbsan Plus may be applied. This consists of a sheet of alginate fibres bonded to an absorbent viscose pad. Unlike the plain alginate products, Sorbsan Plus requires no secondary dress- ing. For deeper wounds and small cavities, alginate packing is available in the form of a rope or ribbon. Lightly exuding wounds of limited depth, can be dressed with a more occlu- sive type of alginate dressing such as Sorbsan SA or Kalto- clude. Sorbsan SA consists of a piece of alginate fleece bonded on to a thin sheet of polyurethane foam to form an island dressing, Kaltoclude is similar but has a polyurethane film backing. When applied to low exudate wounds, the backing layers of these dressings are said to conserve moisture and thus prevents the alginate gel formed at the wound surface from drying out. Alternatively, for light to moderately exuding wounds, the use of a hydrocolloid dressing may be preferred. A number of these are now available which differ in structure and composition. The majority consist of an adhesive mass ap- plied to a carrier or backing layer which is impermeable to water and micro-organisms, although most are permeable to moisture vapour when fully hydrated. They include Duoderm, previously known as Granuflex, (Convatec), Comfeel (Colo- plast), Intrasite (Smith & Nephew) and Tegasorb (3M Health Care). Biofilm (Clinimed), which is similar to Duoderm and Intra- site in terms of the composition of the adhesive mass, dif- fers from the other products in the structure of the backing material. Instead of a polyurethane film, the dressing is backed with a layer of a nonwoven polyester fabric. Although highly permeable to moisture vapour, this nonwoven layer is hydrophobic and resists the penetration of water or exudate under normal conditions of use. However as the dressing should not be immersed in water, it is not the product of choice for the treatment of pressure areas in incontinent patients or other individuals who require frequent bathing. Faecal matter or urine which may find its way into the back of the dressing will also be difficult to remove. In these situations, it may be preferable to use one of the film backed hydrocolloid dressings. Elsewhere, however, such as in the treatment of leg ulcers, for example, the highly per- meable nature of Biofilm may be an advantage, as a signifi- cant proportion of the fluid taken up by the hydrocolloid base will be lost as moisture vapour through the back of the dressing. If excessive fluid production becomes a problem with wounds dressed with hydrocolloid sheets, the absorbency of the dressing system may be enhanced by the use of addi- tional hydrocolloid base supplied in the form of granules or pastes. Other dressings which are used for the treatment of chronic exuding wounds include the foam products such as Lyofoam (Ultra) and Allevyn (Smith & Nephew). Lyofoam, consists of a sheet of hydrophobic polyurethane, one surface of which has been specially treated to collapse the cells of the foam and allow it to take up fluid by capillarity. The dressing is freely permeable to moisture vapour and gases but resists the penetration of liquids due to the hydrophobic nature of the unmodified back. When placed in contact with blood or exudate, the fluid is slowly drawn up into the wound contact layer and transferred laterally across the face of the dressing. The aqueous component then evaporates into the large cells at the back of the dressing from where it is lost to the environment as water vapour. As this process continues, the cells in the facing layer become filled with cellular debris and solid material and the dressing itself becomes progressively more occlusive. The moist environment which is formed under the foam facilitates autodebridement, and it is a feature of the dressing that moist wounds with sloughy areas, dressed with Lyofoam often contain signifi- cant amounts of semi-liquid slough when the dressing is re- moved. In contrast to the hydrophobic nature of Lyofoam, Allevyn is manufactured from a hydrophilic polyurethane foam, backed with a polyurethane film and faced with an apertured polyurethane net which is designed to act as a `non- adherent' layer. The dressing, which was originally sold for the treatment of burns, is able to absorb large volumes of fluid, some of which is lost by evaporation through the film on the back of the dressing. Some chronic wounds produce an unpleasant odour as a result of bacterial contamination. Medicated products (see below), used in conjunction with systemic antibiotic therapy, may be used to control the infection, and dressings containing ac- tivated charcoal can be applied to control the odour. [2] Examples of odour absorbing dressings include Actisorb Plus (Johnson and Johnson) and Lyofoam C (Ultra). Alternatively as described in part one, Scherisorb gel (Smith & Nephew), medicated with metronidazole 0.8% may be used to control in- fections caused by anaerobic organisms which are responsible for the odour that is produced in certain types of wounds. This treatment should only be carried out under medical su- pervision. One group of wounds that are often particularly difficult to heal are sinuses and other lesions which have a narrow open- ing leading to a flask shaped cavity under the skin. In these situations some form of packing is often inserted to ensure that the entrance does not close over before the main body of the wound is healed. Ribbon gauze packs are most commonly used, but a number of the new dressing materials can also be of value. If the wound is moist, it may be packed with alginate ribbon using a suitable probe, but care should be taken to ensure that it is not packed in too tightly. Hydrocolloid granules and pastes can be used for small cavity wounds which should then be covered with a sim- ple absorbent pad to allow adequate drainage. Alternative- ly, Scherisorb gel may be introduced into the cavity using a syringe and quill where necessary. (Scherisorb is particu- larly useful if a significant quantity of slough is present in the wound.) Ribbon gauze impregnated with Scherisorb gel may be used if physical packing of the wound is indicated. It is important to note that it would be unwise to introduce any of these gel forming materials into a sinus which may connect with a body cavity until the wound has been careful- ly probed or the depth determined by some other means. Epithelialising/superficial wounds With a few notable exceptions, epithelialising wounds tend not to produce large quantities of exudate. Where excessive fluid production is a problem, however, such as in the treatment of burns and donor sites, a dressing is required which can cope with large volumes of liquid without causing maceration of the surrounding skin. Traditionally, these wounds have been dressed with paraffin gauze covered with a layer of Gauze and Cotton Tissue (Gamgee) but some centres have reported that both alginates[3,4] and hydrocolloid dressings[5] appear to offer advantages over more conven- tional treatments. Omiderm - a highly permeable hydrophilic polyurethane film which may also be used for heavily exuding wounds, was reviewed in an earlier edition of the Dressing Times (Vol.2 No.1). Superficial wounds which produce relatively little exudate may be dressed either with the hydrocolloids or one of the semipermeable film dressings such as Opsite (Smith & Nephew), Bioclusive (Johnson & Johnson) or Tegaderm (3M). These materials are also used as catheter dressings and are even applied prophylactically to prevent or reduce friction damage to the skin of bedridden patients. Probably the major requirement of a dressing which is to be applied during the final stages of the healing process, is that it should not adhere to the surface of the wound. Per- forated plastic film products such as Melolin (Smith & Nephew) and Telfa (Kendall) are widely used for minor in- juries, and dressings coated with metallic aluminium which are claimed to be non-adherent are also available. A recent unpublished study (the subject of a personal communication) has shown that Lyofoam is a useful low adherent dressing for the management of superficial wounds, and the dressing has recently been included in the Drug Tariff for this purpose. Other dressings which are claimed to be of low adherence in- clude the knitted viscose products such as N-A Dressing (Johnson & Johnson) and Tricotex (Smith & Nephew) and the Paraffin Gauze Dressings of the BP. These are also available medicated with antibiotics and antimicrobial agents, and in- clude Sofra-Tulle (Roussel), containing framycetin, Fucidin- Intertulle (Leo), containing fucidin, Inadine (Johnson and Johnson) which contains povidone iodine and Bactigras (Smith and Nephew), Serotulle (Seton) and Clorhexitulle (Roussel ) all of which contain chlorhexidine acetate 0.5%. As it has long been accepted that the topical use of antibiotics should be discouraged because of the potential problems of skin sensitivity and the emergence of bacterial resistance,[6] medicated dressings used for the treatment of infected wounds should be limited to those materials which contain chlorhexidine and povidone iodine or other suitable antimicrobial agents. Dressing selector device A simple device which summarises the information and advice contained in the last two issues of The Dressing Times has been produced by the author and is available free of charge from Convatec from whom further details may be obtained. References 1. Wood R.A.B. and Hughes L.E., Silicone foam sponge for pi- lonidal sinus: a new technique for dressing open granulating wounds, Br. med. J., 1975, 3, 131-133. 2. Butcher G., et al., The treatment of malodorous wounds, Nurs. Mirror, 1976, April 15, 64. 3. Groves A.R. and Lawrence J.C., Alginate dressings as a donor site haemostat, Ann. R. Coll. Surg., 1986, 68, 27-28. 4. Attwood A.I., Calcium alginate dressing accelerates graft donor site healing, Paper presented to the Winter meeting of the British Association of of Plastic Sugeons, England, December 1986. 5. Doherty C. et al., Granuflex hydrocolloid as a donor site dressing, Care of the critically ill, 1986, 2, 193-194. 6. D'Arcy P.F., Drugs on the skin: a clinical and pharmaceu- tical problem, Pharm. J., 1972, 209, 491-492. Editor's note The advice expressed in this article is based upon the expe- riences of the author. However there will doubtless be oth- ers who hold different or contradictory views. Any corre- spondence on this or any other issue related to wound man- agement would be welcomed and reproduced in a subsequent edition of the `Dressings Times' Change of address The surgical dressings unit has recently moved from East Glamorgan Hospital to larger premises in Bridgend with the address shown below. This move which has taken a number of weeks to complete, was responsible for the delay in produc- ing this issue of the Dressing Times for which we apologise. Normal service will be resumed as soon as possible! The Dressings Times is produced by the Welsh Centre for the Quality Control of Surgical Dressings, Bridgend General Hos- pital, Quarella Road, Bridgend, Mid Glamorgan. Telephone No. (0656) 752820.