- 1 - Welcome to the seventh edition of the Dressings Times in which we continue our series of articles on specific wound management topics written by individuals who are acknowl- edged experts in their field. In this issue, Sue Bale, a research nurse, deals with the treatment of cavity wounds and describes how the physical characteristics of such wounds, influence the choice of dressing. THE ASSESSMENT OF CAVITY WOUNDS Throughout the 1980s, a number of new wound management mate- rials have become available which are suitable for the treatment of cavity wounds. Although these dressings are very different in structure, their aim is essentially the same - to provide an environment in which healing can pro- ceed at the optimum rate. However good these new dressings may be, if they are to be used successfully, they must be applied to the right wound at the appropriate stage of the healing process. For cavity wounds, as with all other wound types, careful and thorough assessment is the basis of good wound management. It is also essential that the user be aware of what he, or she, requires from a dressing in order to ensure that each product is used cost effectively. Dur- ing the decision making process, the following factors should be taken into consideration. Wound Size In general, the larger the wound, the longer it will take to heal and therefore the size of the wound provides a useful indication of the probable healing time. The healing rates of some wound types, such as pilonidal sinus excisions and abdominal wall wounds have been carefully measured, and so it is often possible to predict with some accuracy exactly how long such cavities will remain open1. The size of the wound may also influence the choice of dressing. Whilst small cavities may be dressed with one of a number of prod- ucts, it may not be practical to use all of them on larger wounds where multiple pieces or packs would be required. In these situations, the choice of dressing may be limited to products which provide the required bulk with just one or two packs. Wound Measurement In order to assess the effectiveness of a particular treat- ment, it is necessary to monitor changes in the size of the wound. Surgically created cavities are usually of even con- tour and depth, the length and breadth of which can general- ly be determined fairly easily. Weekly measurement is suf- ficient and steady progress should be evident. Wound volume is more difficult to assess and does not really offer any advantage over the measurement of linear dimensions. Chron- ic wounds such as pressure sores are often more difficult to measure as the wound may extend under the skin edge. The simplest way of assessing the extent of these wounds is to insert a probe under the edge of the cavity and mark the boundary on the skin with an ink marker. Remeasurement may only be necessary every 2-3 weeks as healing is generally slower in these chronic wounds. Wound Shape When managing cavity wounds, it is necessary to recognise the importance of wound shape. Ideally, cavities created surgically should be boat or saucer shaped with evenly slop- ing sides. Where pockets, tracts or sinuses occur within a cavity, drainage of exudate may be inadequate. This in turn may greatly delay healing. Poor wound shape also restricts the range of materials that can be used. For example a long narrow cavity will require a dressing which is conformable enough to be inserted into the space available but which can be easily removed from the depth of the wound without leav- ing behind fibres and particles which could become a focus for infection. In wounds where the shape is so poor that progress towards healing is unacceptably slow, surgical re- vision may be required in order to create a wound with more regular contours. This is occasionally necessary when wounds, which have undergone primary closure, subsequently breakdown. Pressure sores are particularly prone to develop into poorly shaped wounds and as surgical revision is not always possible or advisable, careful choice of dressing ma- terials is essential. Exudate Production Cavities vary enormously in the amount of exudate that they produce. New surgical wounds can exude very heavily but some pressure sores may produce very little fluid. This variation will affect the choice of dressing. Some products are highly absorbent and able to deal with copious dis- charges whereas others have a very limited absorbent capaci- ty. The inappropriate use of a dressing can sometimes have serious consequences. If for example a product is chosen that is unable to cope with the exudate produced by a wound, the surrounding skin may become macerated but a very hy- drophilic product applied to a lightly exuding wound may cause excessive drying of the wound surface, delaying heal- ing and sometimes even causing pain. Presence of Slough or Necrotic Tissue When slough or necrotic material is present on the wound surface, healing will be delayed or in some cases prevented altogether. In the past a range of solutions and lotions including Eusol, and Aserbine have been used to remove such tissue, although these can also damage the surrounding skin and impair wound healing2. Fortunately, dressings such as hydrogels and hydrocolloids are now available which encour- age natural debridement without causing any unnecessary dam- age. When sloughy or necrotic tissue has become softened or loosened, it may be possible to remove it surgically without anaesthesia but the practitioner needs to be experienced in this field. Appearance of the Wound Bed In the pre-granulation stage, cavity wounds often appear red-raw and have a very uneven surface of adipose tissue. It is important to recognise that this is normal for this early stage of healing. Within 10-14 days however, the ap- pearance of the wound will change as granulation tissue is formed. A healthy wound should be pale pink in colour (sometimes covered with a pale yellow membrane), pain-free and not bleed easily if touched. If infection is present, the appearance of the wound will alter. The colour of the tissue may change from pale pink to deep red and the wound may show a tendency to bleed easily on light contact and be- come uncomfortable or painful. Superficial bridging may al- so occur. As the presence of infection can delay healing,3 prompt treatment is needed in these situations. For deep seated infections a wound swab followed by the appropriate course of antibiotics is generally indicated, but more su- perficial infections can sometimes be treated topically. Until the infection is cleared no dressing material will be effective. Excessive Granulations From time to time, re-epithelialisation fails to take place due to the presence of excessive granulation or `proud flesh'. The simplest treatment is application of 75% silver nitrate sticks which cauterizes the tissue but a less trau- matic method is the use of a cream containing a corticos- teroid, although this should only be applied under medical supervision. Conclusion The need for careful assessment is paramount in the success- ful treatment of cavity wounds. It is also necessary to consider precisely what is required of a dressing before se- lecting a product from the range of materials available. When planning a wound care program, consideration of the factors described above should provide the nurse or other practitioner with an accurate picture of the needs of each wound and also provide some assistance with the dressing se- lection process. References 1. Marks J. et al., Prediction of healing times as an aid to the management of open granulating wounds, World J. Surg., 1983, 7, 641-645. 2. Leaper D., Antiseptics and their effects on healing tis- sue, Nursing Times, May 28, 1986. 3. Marks K. et al Pilonidal sinus excision-healing by open granulation. Br. J. Surg., 1985, 72, 637-640. Sue Bale BA SRN NDN HV DipN EUSOL REVISITED The current debate on the use of hypochlorite solutions con- tinues to generate correspondence in the medical and nursing press. Two articles published recently, both question the relevance of the evidence cited by the anti-Eusol lobby and suggest hypochlorites do have an important role to play in cleaning necrotic wounds and combating or preventing infec- tion. In an interesting and balanced editorial1, it was suggested that although there were grounds for questioning the value of Eusol, these were based upon the results of laboratory studies using cell culture techniques or animal models which bore little relation to the clinical use of the products concerned as neither of these test systems contain the organic debris (proteinaceous components of serum, fib- rin and collagen) found in a dirty leg ulcer or pressure sore. It was also suggested that as hypochlorites have an excellent antimicrobial spectrum, they are of particular value in the treatment of dirty or infected wounds. The au- thor proposed that studies should be performed to examine the in vivo effects of antiseptics agents such as the hypochlorites but until such time that the results of this work become available - `medical and nursing staff should not be blinded by data derived from experiments which use models that bear no relationship to the clinical situation of a dirty ulcer'. The supposed advantages and lack of tox- icity of the hypochlorites were similarly referred to in a letter which criticised current attempts to ban the use of Eusol and similar solutions2. It was suggested that any ad- verse effects which these materials may produce should be `balanced by the benefits from destruction of bacteria and cleansing of necrotic material'. It was stated that this opinion was based upon the author's 30 years experience with the agents concerned, and he did not consider any research necessary. Many of the claims for the beneficial effects of the hypochlorites are based upon the work and observations of Dakin who used these materials with great effect to prevent sepsis and remove necrotic tissue during the first World War. He suggested that in the treatment of small lesions, 5-10 mL of solution should be introduced into the wound ev- ery two hours using a pipette or syringe but for larger, necrotic wounds, up to two litres could be applied by con- tinuous or frequent irrigation; such large volumes were rec- ommended because Dakin recognised that the solution was rapidly inactivated by the presence of pus and organic mat- ter. The frequent application of large volumes of hypochlo- rite solution by irrigation is in marked contrast to current nursing practice in which small volumes of solution are ap- plied in the form of packs or soaks. When used in this way, it is highly unlikely that sufficient available chlorine will be introduced into the wound either to exert an appre- ciable antibacterial effect or to dissolve slough or necrot- ic tissue. This may be illustrated by a simple calculation. A length of ribbon gauze 2.5 cm wide and a metre long can absorb approximately 5 mL of hypochlorite solution. If this is packed into a small cavity or sinus, assuming that none of the available chlorine will be lost by evaporation and all the hypochlorite absorbed by the gauze will come into contact with the necrotic material in the wound, (two very large assumptions!) then this volume of solution will be sufficient to solubilise a maximum of 0.05 grams of necrotic tissue for as reported previously3, it takes about 100 mL of Eusol to dissolve one gram of slough. On this basis, ap- proximately 100 dressing changes would be required to remove 5 g of slough from a small cavity! Clearly this does not accord with the observations and opinions of the authors re- ferred to previously who believe Eusol to be an effective wound cleansing agent. If wounds dressed with hypochlorites do become free of necrotic tissue faster than these figures would suggest, then some mechanism other than chemical degradation must be involved. This is almost certainly sim- ple rehydration followed by autolysis, a process which can also be brought about by the use of hydrocolloids, hydrogels or other substances which maintain the wound in a moist con- dition. Because hypochlorites are rapidly inactivated by debris in sloughy or necrotic wounds, the antibacterial activity of these solutions is also likely to be very limited. In one of the few published studies describing the clinical use of Eu- sol and liquid paraffin in the treatment of leg ulcers4, the number and variety of micro-organisms present in each wound were monitored over a six week period. No significant an- tibacterial effect was detected but the number of pathogenic organisms present actually increased in some of the wounds and Pseudomonas, Streptococcus and enterobacteria which were not present initially in some of the ulcers at the commence- ment of the study were isolated from them subsequently. Other ulcers which did contain these organisms initially, remained contaminated throughout the study and only a small number of wounds became free from contamination following treatment with Eusol. Further evidence of the poor antibac- terial properties of hypochlorite solutions in vivo was pub- lished recently following a study which compared the cyto- toxic and antibacterial properties of a number of agents used for the treatment of infected wounds5. Standard wounds in pigs were dressed with the materials in question which were replaced after 48 and 96 hours. It was found that only chlorhexidine solution 0.2% was able to eradicate all bacte- ria from the wounds to which it was applied. Interestingly, this solution was also found to have the most adverse ef- fects upon wound healing. It should be noted however that chlorhexidine gluconate is generally used at a concentration of 0.05% which has been shown in other studies to be free of cytotoxic effects. In contrast, half-strength Eusol showed little tendency to impair or delay healing but all wounds contained a heavy mixed growth of organisms including Staphylococcus epidermidis, Streptococcus faecalis, and Es- cherichia coli. Had the dressings been changed daily, or full strength Eusol used, the effect upon the number of or- ganisms present and the wound healing process may have been different. None of the evidence presented above is conclusive, and the Eusol debate will no doubt continue for some time to come. However it is probably reasonable to draw the following con- clusions; i. When applied to necrotic wounds in the form of packs or soaks which are changed on a daily basis, it is unlikely that the hypochlorite is present in sufficient concentration to exert any significant chemical debriding effect. ii. When used in this way, it is also unlikely that the so- lution will exert any significant anti-bacterial effect be- cause the hypochlorite will be rapidly inactivated by the necrotic material present. iii. When applied to wounds totally covered with slough or necrotic tissue, it is unlikely that the hypochlorite will have any marked effect upon the healing process because it will be rapidly inactivated as described above. It is possi- ble however, that the solution may exhibit some undesirable effect upon the surrounding skin. iv. In view of the results of animal and tissue culture studies which clearly indicate that even very dilute solu- tions of hypochlorites can have a dramatic effect upon the viability and function of the various cell types involved in the wound healing process, there can be little justification for the use of these materials in the management of wounds which are clean or free of slough. In these situations, the hypochlorite will not be readily inactivated and may be free to interact with otherwise healthy or viable tissue. Conclusion We would agree with the view expressed by Dr Cunliffe that further research is required and the opinion of Mr Langridge that the risk-benefits associated with the use of Eusol should be considered before rejecting the material complete- ly but in our opinion, the majority of the evidence pub- lished to date firmly supports the view of the anti-Eusol lobby and it is now the responsibility of those in favour of continuing to use hypochlorite solutions in routine wound management to support their claims for its efficacy with sound scientific research. References 1. Cunliffe W.J., Eusol-to use or not to use?, Derm. in Pract., 1990, 8, 5-7. 2. Langridge C.J,. Ban on hypochlorite solution is stupid, (letter), Hosp. Doc., June 28th 1990 3. The Dressing Times 1988, 1 No.3 4. Daltrey D.C. and Cunliffe W.J., A double-blind study of the effects of Benzoyl peroxide 20% and Eusol and liquid paraffin on the microbial flora of leg ulcers, Acta Derm. Venereol., 1981, 61, 575-7 5. Archer H.G. et al., A controlled model of moist wound healing:comparison between semi-permeable film, antiseptics and sugar paste, J.exp. Path., 1990, 71, 155-170. 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. (0656) 752820.