- 1 - Welcome to the sixth edition of the Dressings Times. In this issue we begin a series of articles on specific wound management topics written by individuals who are acknowl- edged experts in their particular field. The first of these has been produced by Dr Chris Lawrence, and deals with the management of burns. Future editions will deal with the treatment of cavity wounds and the importance of nutrition in wound healing. Also in this issue is a profile of Silas- tic foam, a versatile dressing which is used in the manage- ment of a variety of surgical and cavity wounds. Readers of the Times may be interested to know that this publication has now gained `international' status, with sub- scribers in America, Australia, Hong Kong and Saudi Arabia. In order to maintain this interest, we are very eager to re- ceive contributions on dressings related topics in the form of short articles, case histories or letters. Alternatively, if you have discovered a novel wound treatment or developed a new wound management technique, no matter how simple, that you think others may find useful, write and tell us and we will publish it in a future edition of the Times. DRESSINGS FOR BURNS Burns are probably the most extensive of all the types of skin wounds that are commonly encountered. For example, even large leg ulcers rarely exceed 1% of the total surface area of the body. (As a rough guide, 1% of the body surface is approximately equal to the palmar surface of the hand.) In a typical series of minor burns, treated on an outpatient basis at the Birmingham Accident Hospital, the mean percent- age area of the body surface involved was about 0.7%. In contrast, the mean area of the burns on 450 patients who were admitted into the hospital in a recent year was 14% of the total body surface. In England and Wales the annual number of burned persons seeking hospital attention is at least 130,000, about 12,000 of whom are detained in hospi- tal. Approximately 50% of the patients are children, many of whom are below school age, and about half the injuries are scalds which predominate in children. Although burns may be classified into a number of groups according to their depth or severity, for all practical purposes it is general- ly possible to divide them into two basic types. Partial thickness burns involve principally the outer layer of the skin. Such wounds should heal uneventfully within 21 days by the growth of epithelium from surviving foci provid- ed by the undamaged shafts of hair follicles and sweat ducts deep in the dermis of the burn (Fig.1). Full thickness burns contain no epithelial foci and can only heal from the wound margin (Fig.2). In man this process is very slow and leaves a fragile scar, hence it is usual to recommend closure of such wounds with skin grafts. It is important to remember that erythema does not represent burning, and although painful, this condition is sponta- neously reversible. The best treatment appears to be calamine lotion and reassurance. It is widely accepted that burns require dressings, and in the United Kingdom and other temperate climates, unless spe- cial facilities are available, the use of dressings in com- bination with suitable topical antibacterial agents is prob- ably desirable in the treatment of these wounds. By con- trast, in a warm, dry environment, such as that encountered in the Middle East, even very extensive burns can heal re- markably uneventfully in the absence of dressings. In 1830 the famous French surgeon Baron Dupuytren stated, `Burns are often subject to the most bizarre forms treat- ment'. Examination of current literature suggests that to some extent at least, this statement remains valid. As far as the use of dressings (either with or without antibacteri- al agents) is concerned, it wise to bear in mind their three main functions or aims which are, protection, prevention and improvement. Protection implies isolation from the environ- ment which includes mechanical contacts which may further traumatise the wound. Micro-organisms must be prevented from accessing the wound surface and wound exudates must not con- taminate the environment. Topical therapy should bring about an improvement in the wound compared with, for example, do- ing nothing, and an improvement in patient comfort must al- ways be considered desirable. All burns contain dead tissue which, bathed in nutrients at about 37C, forms an excellent bacterial culture medium. Consequently, although most burns are sterile at the time of injury, they readily acquire bacteria including pathogens. Wounds that become colonised in this way put the patient at risk from infection. The degree of risk depends on several factors, although the extent of burn is particularly impor- tant. In large burns, infection may not be obvious until the victim develops septicaemia. Thus, in many instances, there is a powerful arguement for not only isolating the wound from the environment but also for using topical antibacteri- al therapy. For burns that exceed 1-2% of the body surface, it may seem surprising that modern technology has not led, at least on a commercial basis, to the production of a more satisfactory material for this purpose than pads made from absorbent cotton and gauze. Such dressings were first de- vised by Dr Joseph Gamgee at the Queen's Hospital in Birm- ingham just over a century ago. In use they act as a micro- bial filter in much the same way as the cotton wool that is used to plug tubes of bacterial nutrient to maintain steril- ity. Gamgee tissue is compatible with many antibacterial agents, thus it is frequently used with these materials, se- cured in place with crepe or some other suitable bandage. Antibacterial agents suitable for use in burn management are somewhat limited. Silver suphadiazine is the most widely used, but sulfamylon is preferred by some authorities al- though the latter is painful and can cause metabolic acido- sis. A co-operative pharmacy department `on-site' can ex- tend this range by manufacturing creams containing silver nitrate plus chlorhexidine or phenoxetol plus chlorhexidine. A major disadvantage of absorbent wool dressings is that they lose their bacterial barrier properties in the presence of moisture. This occurs before visible `strike through' is apparent. It is therefore wise to change such dressings regularly, within four days at most. Leakage, slippage, strike through and unexplained pain, merit prompt dressing removal and wound inspection. Changing a burn dressing can often be an extremely painful proceedure for the patient who may require the use of potent analgesics or even anaesthesia in some instances. Grafted burns are often dressed in the same way as the ac- companying donor sites. Tulle gras, sometimes medicated, is frequently used for this purpose together with absorbent gauze secured by a crepe bandage or plaster of Paris. It is unwise to use tulles containing antibiotics because of a risk of the emergence of resistant bacterial strains. In practical terms this virtually limits the choice of medica- tion to a chlorhexidine tulle which is very effective against Gram positive bacteria but less effective against Gram negative organisms. Skin grafts are usually inspected four days post operative- ly, and although they should be completely healed by this time, they usually require a further dressing for a week or so, mainly to provide mechanical protection whilst the skin keratinises. It is usual to accord similar protection to donor sites and partial skin thickness burns which have re- cently re-epithelialised. Donor sites are commonly left for 10-14 days prior to dressing removal (unless some untoward event occurs) by which time they should be well healed un- less moderately thick skin has been excised. Some modern dressing materials have been successfully used to treat donor sites, these include vapour permeable plastic films such as Opsite, hydrocolloid materials such as Granu- flex or Granuflex-E and combinations of materials such as alginates covered with vapour permeable membranes. Success has been claimed with a wider variety of dressings than those quoted but in many instances these appear to offer no genuine advantages over other treatments, especially when factors such as cost and convenience of management are taken into consideration. Tulle gras is also a popular dressing for minor burns, but whether this needs to be medicated or not is debatable. Certainly a degree of prophylactic antibacterial activity can be demonstrated for the chlorhexidine medicated material and also for Inadine, a non-adherent dressings coated with polyethylene glycol containing povidone iodine, though this latter material is slightly less efficient. However, given prompt, adequate care using a strict aseptic management technique, the incidence of infection in such wounds is rel- atively low, (perhaps less than 1%) despite the presence of potentially pathogenic bacteria in well over 30% of these injuries. There is also a case for using medicated dress- ings in the management of burns on patients who delayed seeking attention beyond the day of injury since a large number of these wounds are found to be heavily colonised at the time they first present for treatment. The lifestyle of the patient is an additional factor that can influence whether medication may be appropriate. Various creams can also be used to treat burns, often in combination with traditional dressings. In mobile patients however these have the disadvantage that as they are excel- lent lubricants, satisfactory securement of the dressing may be difficult to achieve especially in young children. Creams are also expensive. There are several problems associated with the use of tradi- tional dressing materials, not least is the problem of adhe- sion at the time of dressing changes. With tulle gras the incidence of adhesion is about 20% (and this purports to be a non-adherent material), however, other materials such as surgical gauze are far worse. The problem can be minimised by avoiding the strict interpretation of the term `dressing change'. It makes little sense to vigorously rip off an ad- herent dressing since this may also remove much of the new epithelium. In addition, such a procedure may be very painful. There is also an attendant risk of leaving some of the dressings in situ. Occluded foreign bodies such as fi- bres or particles can lead to an inflammatory response and also exacerbate scarring. In practice therefore, it is wis- er not to remove an adherent wound contact layer since it is relatively unusual for a dressing to adhere to a suppurating wound simply replacing the outer absorbent material fre- quently suffices. If more medication is thought desirable then a further sheet of tulle can be laid over the original. By way of analogy few gardeners dig up seeds at regular in- tervals to see if they are germinating! Several of the newer dressings can be used as alternatives to conventional products, sometimes with advantage. Vapour permeable adhesive films may reduce the healing time of burns and donor sites as can hydrocolloid dressings, and both have the additional advantage of being waterproof. This feature is greatly appreciated by many patients as is the reduction in dressing bulk. Despite the range of such materials available, comparative trials are scant such that only Opsite and Granuflex appear to have had exhaustive ex- amination. Transparent films fail to adhere on about 20% of patients and there appears to be no way of predicting those individu- als on whom the dressings will not stick. Moreover, al- though their transparent nature affords the clinician the opportunity to inspect the wound, it also affords the pa- tient the same privilege. The latter is often much less en- thusiastic about viewing his wound and so a further dressing may be required by way of camouflage . There may well be other materials that could be used with advantage in the treatment of burns and there is consider- able scope for additional clinical studies in this area. Unfortunately, there are also a considerable number of new dressings that are used as a result of commercial pressure rather than proven merit. Some are very expensive and their use cannot be justified unless a proven positive advantage can be shown. J.C. Lawrence The Burns Research Group Birmingham Accident Hospital Bath Row Birmingham B15 1NA PRODUCT PROFILE: SILASTIC FOAM Silastic foam dressing consists of a resilient open cell foam which is formed in situ from two liquids which are mixed together and poured into the wound. As a result of the reaction which takes place, hydrogen gas in liberated and the mixture increases to approximately four times its original volume as a foam is produced which sets rapidly to form the dressing or `stent', a process which takes about three minutes. Although Silastic foam is very easy to use, it is important to follow the manufacturer's instructions carefully. In particular the base, which is presented in the form of a suspension, has a tendency to settle out on stor- age, and must be thoroughly mixed prior to the addition of the catalyst to ensure consistent results. Accurate measure- ment of the two components is also important. These should be used in the ratio of 10ml of base to 0.6 ml of catalyst and are best measured out using two appropriately sized sy- ringes. A silastic foam stent may be used for a number of days, of- ten up to a week or more, provided it is disinfected regu- larly by soaking in a suitable antiseptic for 10-15 minutes whilst the wound is cleansed or the patient takes a bath. After this time it should be rinsed carefully under running water, squeezed dry and replaced in the wound. Although aqueous chlorhexidine gluconate solution 0.5% is the anti- septic of choice, cetrimide 1% or chlorhexidine 0.5% in spirit can also be used provided that the dressing is rinsed thoroughly and no residues remain in the foam which may lead to the formation of sensitivity reactions.1 Initially the stent should be removed and cleansed twice a day, but as the wound begins to heal and exudate production diminishes, this may be reduced to once a day. Silastic foam is primarily indicated for the treatment of open granulating wounds, especially cavities, which may be formed following the surgical removal of large amounts of tissue. It was originally used in the treatment of pilonidal sinus wounds where it was found to reduce pain, enhance healing and decrease the time spent in hospital.3 Silastic foam has also been used to treat sacral pressure sores, per- ineal wounds and cases of abdominal wall breakdown. In all these applications, it was recorded that the use of the dressing increased patient comfort and led to a reduction in the time spent on nursing care. The major advantages claimed for the use of Silastic foam are its versatility, high degree of patient acceptability and ease and conve- nience of use.3 Although expensive on a unit cost basis, Silastic foam can be highly cost effective when used correctly4,5 as a single dressing can be used for a number of days, often managed entirely by the patient in his own home Silastic foam should not be introduced into sinuses or other narrow wounds which might contain constrictions, these could result in small pieces of foam becoming detached from the main body of the stent and causing problems later on. Following a report that a chemical entity related to the catalyst used in Silastic foam was found to be toxic to rats, the dressing was withdrawn from sale in some European countries. However after reviewing all the available evi- dence and toxicological data, Dow Corning, the manufacturers of the dressing and Wellcome, the distributor in the UK, are completely satisfied that the product is safe and free of any adverse effects and therefore this unique and highly useful material continues to remain available. References 1. Evans B.K. et al., The disinfection of silicone foam dressings, J. clin. Hosp. Pharm., 1985, 10, 289-295. 2. Wood R.A.B. and Hughes L.E., Silicone foam sponge for pilonidal sinus: a new technique for dressing open granulat- ing wounds, Br med J., 1975, 3, 131-133. 3. Wood R.A.B. et al., Foam elastomer dressing in the man- agement of open granulating wounds: experience with 250 pa- tients, Br. J. Surg., 1977, 64, 554-557. 4. Culyer A.J. et al., Cost effectiveness of foam elastomer and gauze dressings in the management of open perineal wounds, Soc. Sci. Med., 1983, 17, 1047-1053. 5. Young H.L. and Wheeler M.H., Report of a prospective trial of dextranomer beads (Debrisan) and silicone foam elastomer (Silastic) dressings in surgical wounds, Br. J. Surg.,1982, 69, 33-34. 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.