Philippa J. Cunliffe, BSc (Hons), RN.
Staff Nurse, The Royal Infirmary of Edinburgh, Edinburgh
For many centuries wounds have been cleansed, using a variety of methods and solutions, to promote healing (Flanagan, 1997).
Since their discovery by Lister in the 19th century, antiseptics have been popular wound-cleansing agents (Lawrence, 1997). However, in recent years their use has been questioned and normal saline (0.9% sodium chloride) has become the favoured alternative.
The techniques used to cleanse wounds have also changed over time. For many years, swabbing the wound was the most common method but was abandoned after research suggested that swabbing could cause damage to healthy granulating and epithelialising tissue. Although wound cleansing has come a long way in recent years and continues to develop further (Trevelyan, 1996), wound care is an area of nursing renowned for ritualistic rather than evidence-based practice (Fletcher, 1997; Blunt, 2001). This may be due to insufficient research in this field, or because findings of research have not been implemented in practice (Rodgers, 2000). Within the context of hospital care, current practice in wound cleansing would seem to favour low-pressure irrigation with normal saline (Dealey, 1999). This paper focuses on the ward setting and aims to examine the extent to which this practice is based on evidence of its effectiveness.
The importance of evidence-based practice
Nursing is, in many ways, a discipline based on tradition and it may be a challenge to change practice to that which is based on evidence.
It is first important to define what is meant by ‘evidence-based practice’ and to identify the role evidence-based practice plays within nursing.
Various definitions of evidence-based practice exist; for example French (1999) suggests that it is: ‘The systematic interconnecting of scientifically generated evidence with the tacit knowledge of the expert practitioner to achieve a change in a particular practice for the benefit of a well-defined client/patient group’ (French, 1999).
The concept of evidence-based practice has become central to the NHS, where cost-effectiveness, value for money and quality assurance are at a premium (Upton, 1999). It is also unacceptable for health care not to be based on sound evidence and on evidence of effectiveness (McKenna et al, 1999). Yet, there continue to be nursing interventions undertaken which are based only on tradition. As Hunt (1997) and, more recently, McCaughan (2002) have observed, many nurses fail to use research to guide their decision making, thereby continuing to support practices for which there may be no sound evidence base.
It is acknowledged that not all research findings are published. Easterbrook et al (1991) suggest that this may be because of ‘publication bias’, the selective publication of positive results. Alternatively, research may be published in particular highly rated, peer-reviewed, international journals and may not reach as wide an audience of practitioners as it should (Towler, 2001). Towler (2001) identifies this as a particular problem in wound care because of the large population of individuals involved in its delivery and the small number of peer-reviewed journals dedicated to wounds and tissue viability.
The gap between theory and practice within nursing is well documented and it is argued that the systematic process of evidence-based practice may assist in reducing this gap (Upton, 1999). However, the existence of evidence to inform practice is only the first step towards evidence-based practice. One of the greatest hurdles, it would seem, is getting nurses to use the research. Many nurses still see research and its utilisation as something too difficult or irrelevant and find researchers’ work too remote from practice (Hunt, 1997; McCaughan, 2002).
Box 1 demonstrates the different forms of acceptable evidence on which practice should be based. Not all nursing interventions easily lend themselves to evaluation through research, and it is a wrong to assume that evidence for practice comes only in the form of randomised controlled trials (RCTs). It has always been recognised that clinical experience is an important, even critical, source of knowledge and a component of clinical decision making (White, 1997).
The practice of wound cleansing
There are three parts to successful wound cleansing: the technique, the choice of equipment and the cleansing agent (Trevelyan, 1996). Low-pressure irrigation, often with a syringe, and using normal saline, is the currently favoured method of cleansing and it is the evidence to support this practice that must be evaluated.
Not all wounds require cleansing; the belief that they do is one of the greatest myths and areas of ritualistic practice within wound care. Miller and Dyson (1996) state that there is no point in cleansing a wound that is healing by secondary intention to remove or reduce bacteria. Such wounds should be cleansed only to remove superficial slough, excess exudate, visible debris or any matter from previous dressings.
Flanagan (1997) suggested that the reasons for wound cleansing were to:
- Rehydrate a wound in order to provide a moist environment
- Facilitate wound assessment
- Minimise trauma when removing adherent dressing materials
- Promote patient comfort.
However, with the development of new dressings, rehydration can now be achieved by the use of modern moisture-retaining and interactive dressings (Ballard and Baxter, 2000). Interactive agents aim to alter the wound bed in order to promote a suitable environment for cell migration and growth (Ballard and Baxter, 2000).
Flanagan (1997) also suggests wound cleansing is appropriate to keep the skin surrounding the wound clean and free from excessive moisture. Thus the surrounding area, rather than the wound, is cleansed (Flanagan, 1997). The surrounding skin may require cleansing to prevent maceration and damage and perhaps to remove dressing adhesive. The management of potential maceration from excessive exudate is achieved through the selection, based on sound evidence, of an appropriate dressing with fluid-handling properties (Cutting, 2002).
Although his sample size was small, Davies (1999) found that 27% of the 25 respondents would clean a wound if it was contaminated by bacteria and 14% would clean a wound if it were moist or exuding. Normal wound healing depends upon the bactericides and nutrients present in wound exudate (Oliver, 1997) and it is therefore important that exudate is not removed and that wounds are not dried. Bacterial colonisation does not appear to impede wound healing but in fact stimulates the inflammatory response, resulting in an improved blood supply to the wound and the arrival of neutrophils and macrophages at the wound bed (Davies, 1999). Removal of bacteria therefore is not a reason for wound cleansing unless the wound is clinically infected.
Conversely, only 36% of respondents stated that they would clean a wound to remove excessive debris, which can become a focus for infection and a barrier to the migration of epithelial cells and therefore disrupt optimum healing (Davies, 1999). It is clear that the nurse respondents in Davies’s study were not equipped with the appropriate levels of evidence to inform their decision making (Box 1). It should also be noted that only 10% had attended a wound-care update or study session in the past two years and 68% of the respondents had never attended one at all.
The evidence for irrigation
Towler (2001) states that the evidence in wound care is often based on respected expert opinion (level 5) rather than scientific evidence (level 1 or 2). Quality randomised controlled trials evaluating wound-care interventions are scarce and much of the information generated from research is often flawed (Towler, 2001). As a result, other sources of evidence such as case studies, expert opinion, and other types of trial evaluation or review may need to be considered when deciding on the clinical management of wounds (Towler, 2001). In a search of Medline and Cinahl no level 1 experimental evidence relating to wound irrigation could be found, although its use, without evidence identified at any level, is often mentioned in journal articles.
Most of the literature agrees that, in order to minimise trauma and optimise the healing of wounds, irrigation is the preferred method of wound cleansing. However, variations exist in the suggested pressures and exact technique to be employed. ‘To irrigate’ means ‘to flush with fluid’ (Anderson et al, 1994).
It is important to bear in mind the purpose of irrigating a wound when choosing the best technique to use and whether the desired effect is likely to be achieved. Morison (1992) and Bale (2000) state that the purpose of wound irrigation is to gently remove loose debris and excess wound secretions from the wound surface in order to help create optimum healing conditions.
Pressure and volume - There are two aspects to irrigation: the pressure of the fluid and the volume required. Irrigation may be gentle or vigorous, dependent upon the desired outcome (Fletcher, 1997) and the severity, presence of debris and stage of healing of the wound. Optimal irrigation force needs to be achieved while minimising tissue trauma (Williams, 1999).
Many authors (Fletcher, 1997; Oliver, 1997; Davies, 1999) cite clinical guidelines by Bergstrom et al (1994), which suggest that pressures of between 4 and 15 pounds per square inch (psi) can be used safely and that a pressure of 8psi appears to be effective in cleansing wound debris. A pressure higher than 15psi (Krasner (1992) argues even 11psi), can damage the wound and drive bacteria into the tissues; a pressure below 4psi is ineffective - serving only to moisten the wound and the surrounding area (Oliver, 1997).
As syringes and needles are always available in the ward these are the most commonly used irrigation equipment. However, the pressure achieved is difficult to judge using these. Krasner (1992) recommends the use of an 18-19 gauge needle and a 30-35 ml syringe to produce an optimal pressure of between 8 and 11psi. Stevenson et al (1976) also produced these recommendations and also recommended that, to achieve this psi, the syringe must be pushed at full pressure. The use of needles also adds the risk of needle-stick injury.
Wound irrigation can also be achieved by a variety of equipment including spray canisters, semi-rigid ampoules or a showerhead (Flanagan, 1997).
The use of sterile saline in pressurised canisters and semi-rigid ampoules allows for wound irrigation without the risk of needlestick injury (Flanagan, 1997). Chisholm et al (1992) found that irrigation with a canister of saline took half the time needed to irrigate a wound using a syringe. The canister also had the advantage of a controllable nozzle to allow a choice of low- or high-pressure irrigation (Williams, 1996). However, to maintain optimum wound healing it is necessary to warm the saline to body temperature. This requires the canister to be held under running warm water. Even when achieving the ideal of 37°C, the maximum impact pressure using a canister is only 6.88psi (Fletcher, 1997). This is not as high as the recommended pressure of 8psi and therefore may not successfully irrigate the wound. Similarly, ampoules of saline may not produce a pressure in excess of 4psi and therefore may also be ineffective (Oliver, 1997).
Effective irrigation is likely to require copious amounts of fluid (Oliver, 1997), Miller and Gilchrist (1996) suggesting a volume between 250ml and 500ml, an amount that must be accommodated within the wound-dressing environment.
Use of high pressure - Miller and Gilchrist (1997) advocate high-pressure irrigation to remove bacteria from a wound. However, as previously discussed, there is no need to remove bacteria from wounds to aid healing. Also high-pressure irrigation may cause damage to delicate granulation and epithelialising tissue (Flanagan, 1997; Williams, 1999) and discomfort to the patient. Wheeler et al (1976) provided evidence that high-pressure irrigation can actually increase infection rates due to damage to the tissues.
Williams (1999) stated that high-pressure jet irrigation may be necessary to debride a wound or to remove excessive bacterial contamination. High-pressure jet irrigation will not be suitable if the aim is to simply remove loose debris and other surface contamination. Lawrence (1997) sees jet irrigation as essentially a debriding technique, not a method of routine cleansing, and as such should be carried out only under operating theatre conditions.
Infection risks: splash-back and aerosols
Pressure irrigation is likely to result in ‘splash-back’ from the wound. Nurses must be aware of this risk and should take suitable precautions to protect themselves from infection and avoid contamination, especially of the mucous membranes (Oliver, 1997). In some instances, for example, where irrigation is to be vigorous and splash-back expected, protective glasses may be recommended (Fletcher, 1997). An aerosol may also be produced, which may not only be a potential source of infection to the practitioner performing the procedure but could also potentially result in further environmental contamination (Lawrence, 1997). Lawrence (1997) recommended that, unless suitable facilities are available, wound irrigation should be restricted to simple washing in a gentle stream of saline solution. Suitable facilities would be a separate location from the ward or a protective ‘capsule’ over the wound through which the irrigation syringe is inserted, and the wearing of protective clothing and glasses. However, no indication is given of the irrigation pressure and therefore the effectiveness of ‘simple washing in a gentle stream of saline’ is open to question.
In summary, the difficulty is in balancing the pressure required to remove loose debris, other surface contamination and excess wound secretions against the negative effects of damage to delicate wound tissue and compromising infection control.
Choice of cleansing solution
A range of cleansing agents is available, including normal saline and tap water. Certain antiseptic agents may be used with caution but agents that are toxic to wound tissue or deemed carcinogenic should be avoided (Mallet and Dougherty, 2000).
Flanagan (1997) lists the characteristics of a wound-cleansing solution as one that:
- Is non-toxic to human tissues
- Remains effective in the presence of organic material
- Is able to reduce the number of micro-organisms
- Does not cause sensitivity reactions
- Is widely available
- Is cost-effective
- Is stable; with a long shelf life.
However, Lawrence (1997) argues that any anti-microbial effects of irrigation are likely to be due to the physical action of the fluid rather than any antimicrobial effects of the solution. Indeed, most antiseptics require to be in contact with the bacteria within the wound for longer than is allowed for during irrigation (Lawrence, 1997).
The evidence for using normal saline
Normal saline fulfils all the remaining criteria given above. Indeed, Dealey (1999) identifies normal saline as the only completely safe cleansing agent and the treatment of choice for use on most wounds. Saline is an isotonic solution and so does not donate or draw fluid from the wound (Davies, 1999). Lawrence (1997) has suggested, however, that a more complex isotonic solution may provide a further improvement, especially one buffered to pH7.4.
There is now increasing recognition of the safe use of tap water for wound irrigation, especially in chronic wounds (Davies, 1999) and it is worth considering as an acceptable alternative. Indeed, Flanagan (1997) argues that water has been used for centuries to treat wounds without any reported detrimental effects.
The two most commonly cited concerns regarding tap water are a possible infection risk and the fact that it is not an isotonic solution. However, Griffiths et al (2001) and also Angeras et al (1992) found that there was no significant difference between the infection and healing rates in wounds irrigated with normal saline or tap water. Indeed, Angeras et al (1992) found a higher rate of infection in those wounds irrigated with saline.
Unfortunately, the trial carried out by Angeras et al (1992) was flawed in that it did not provide a fair comparison of the two solutions: the water was at body temperature, while the saline was at room temperature. This, the authors submit, could have caused local vasoconstriction and therefore impaired wound healing. Angeras et al (1992) also suggested the possibility that those irrigating may have been aware of which solution they were using and were perhaps more generous in their use of water for irrigation. If this is the case, it may be that it was the larger volumes of irrigation fluid which reduced the rate of infection - because more water was used, contaminants would be more effectively flushed out. The study by Griffiths et al (2001) is likely to be more reliable as it was a double-blind randomised controlled trial. It did, however, also have a relatively small sample size.
Flanagan (1997) concludes that as long as the water to be used comes from a properly treated supply and the tap water is run for a few minutes before use, any fears concerning bacterial contamination appear to be unfounded.
Another concern mentioned less frequently in the literature is the effect of the water on human tissue. Water, in contact with breached tissue, can cause pain which Clide (1992) suggests is the result of tissue damage. Because water is hypotonic it will, under the influence of osmotic pressure, cause cells within the tissues to swell and rupture (Flanagan, 1997).
Lawrence (1997) therefore suggests that, because of the potential problems water can cause in wounds it should be used only occasionally. He goes on to argue that, despite the evidence appearing to support the use of normal saline, wound irrigation fluids have received little attention in scientific study (Lawrence, 1997) and therefore the evidence to support the selection of cleansing solutions is still inconclusive (Griffiths et al, 2001).
It is clear that ongoing research is required in the area of wound cleansing, both with respect to the optimum pressure at which to irrigate wounds and the solution to employ.
Much of the evidence on wound cleansing appears to be based on expert opinion rather than scientific study. As part of accountable professional behaviour, nursing practice must be evidence based and, therefore, in the area of wound care, nurses must base their method of wound cleansing on the evidence drawn from research-based literature. The suggestion is that evidence is limited and arbitrary, while such evidence as does exist does not appear to be easily accessible to the practising nurse. Both these concerns must be addressed.
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