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An evidence-based approach to venous leg ulceration

New evidence in wound care is constantly emerging. Una Adderley offers a brief overview of current clinical practice recommendations and the current related evidence base in venous leg ulceration

Una Adderley
DN RGN MSc BSc BA
Community Tissue Viability Prescribing Nurse
North Yorkshire and York PCT

Nurses have a professional responsibility to make clinical decisions that are based on good quality research evidence, wherever and whenever possible.(1) There are many areas of care where high-quality research evidence does not yet exist, but the area of leg ulceration has received a considerable amount of research attention.
Venous leg ulceration has been defined as "an open sore in the skin of the lower leg due to high pressure of the blood in the leg veins".(2) It occurs when the venous circulation is compromised by failures within the deep, superficial or perforator vein systems that enable venous return from the feet and legs. These systems contain valves that allow blood to flow up toward the heart and prevent backflow down the leg. Blood flows towards the heart in response to increased pressure from the pumping of the heart combined with the calf and foot pump mechanisms, which function during walking and when the ankle is flexed. When the valves are faulty they allow the backward flow of blood down the leg, which leads to increased pressure within the veins. This damages tiny blood vessels in the skin, which becomes vulnerable and may eventually break down spontaneously or fail to heal following an injury. The resulting open lesion is known as a venous leg ulcer. Some people are born with poor valves while some acquire valve damage following venous thrombosis (a blood clot that forms within a vein, read more about venous thrombosis on page 36) or as a result of reduced mobility or aging.
The evidence base for venous leg ulceration has benefited from clinicians and researchers who have driven forward the possibility of evidence-based care by developing research-based guidelines and position papers around venous leg ulceration, such as the RCN's clinical guidelines regarding the management of patients with venous leg ulcers.(3) For questions of clinical effectiveness, such as "What treatment heals leg ulcers?", randomised controlled trials deliver more reliable information than clinical observational studies such as case studies. However, evidence from metaanalyses of randomised controlled trials, such as those found in the Cochrane Library, is even more reliable.4 When no robust evidence exists, recommendations are made based on a consensus of expert opinion.

Diagnosis
The RCN clinical practice guidelines recommend that diagnosis of venous ulceration is based on the cliniciantaking a full history and carrying out a physical examination.(3) Recommended routine clinical investigations should include measurement of blood pressure (to monitor cardiovascular disease), weight (to monitor for obesity and subsequent weight loss) and urinalysis (to monitor for undiagnosed diabetes mellitus), but there is currently no robust research evidence to support these recommendations.(3)
Bacterial colonisation of leg ulcers is common, but the impact of such colonisation on healing is uncertain.(5-7) Bacterial swabbing is not recommended unless there are signs of chronic wound infection.(3,8)

Doppler measurement
Arterial supply was traditionally assessed through the palpation of foot pulses with absent or very weak pulses seen as indicating inadequate arterial supply. However, research has found poor agreement between manual palpation and ankle/brachial pressure index (ABPI). Consequently, Doppler measurement of ABPI to screen for arterial disease is recommended since compression applied to arterially compromised legs could lead to ischaemia and pressure damage.(3)

Compression therapy
With regard to treatment, there is robust research evidence in favour of graduated multilayer high compression systems for healing venous leg ulcers that are not complicated by arterial insufficiency (with an ABPI greater than 0.8). Graduated multilayer high compression systems include systems such as high elastomeric systems (such as four-layer bandaging), low elastomeric systems, nonelastomeric systems, short-stretch bandaging, Unna's boot and compression hosiery. There is reliable evidence that better healing  rates are associated with high compression systems compared with low compression systems, but there is no reliable evidence that any particular high compression system is better than another.(3) There is also no reliable evidence to support the use of intermittent pneumatic compression to promote healing.(3)

Dressings
Besides compression therapy, other types of clinical interventions such as dressings, topical and oral medication, devices and surgical interventions are used with the aim of promoting healing, but the evidence for such interventions is less robust. A Cochrane systematic review found insufficient evidence to promote the use of any particular dressing for promoting healing.(9) Therefore it is recommended that dressings should be simple, low-adherent, low cost and acceptable to the patient.(3) Under compression bandaging, a simple knitted viscose (eg, Paratex, N-A dressing, Profore WCL) usually meets these requirements.
Another Cochrane review found no evidence to support the routine use of systemic antibiotics to promote healing, but did find some evidence to support the use of topical cadexomer iodine.(10) No robust evidence could be found to support the use of other types of topical agent.(3)

Oral pentoxifylline
Oral pentoxifylline is an effective adjunct to compression therapy for promoting healing. There is also evidence to suggest that it may promote healing even in the absence of compression.(11) However, there is no reliable evidence to support the use of oral zinc or aspirin for promoting healing.(3)

Other treatments
Ultrasound may promote healing of venous leg ulcers, but this conclusion must be treated with caution since it was based on the results of only eight small trials of generally poor quality.(12) There is currently no robust evidence to suggest that low-level laser therapy or electromagnetic therapy is effective for healing.(3) Skin grafts or skin replacements have also been proposed as an intervention for promoting healing. Bilayer artificial skin, used in conjunction with compression bandaging, appears to increase the chance of healing, but there is insufficient evidence that any other form of skin graft or replacement is effective.(13)
 
Pain relief
Although healing is the most common primary outcome in research into interventions for venous leg ulceration, other outcomes, such as comfort and symptom control, are important to patients. There is some evidence that compression therapy may relieve pain and that EMLA cream is effective in reducing pain during debridement.(3) However, at present, no robust evidence exists to guide practice with regard to interventions for relieving persistent leg ulcer pain.

Ulcer recurrence
Venous leg ulceration is a long-term chronic condition and 59-67% of patients will experience recurrence following healing.(14) There is evidence to suggest that wearing UK class 3 compression hosiery reduces ulcer recurrence.(4)

Implementation
Implementing such an evidence base into practice is rarely straightforward. Despite the existence of a reasonable evidence base to inform venous leg ulceration care, many clinical questions exist for which there is still no robust research to guide practice. It should be noted that lack of evidence regarding an intervention is not the same as evidence that an intervention is not effective. In the absence of evidence, clinicians have little choice but to use knowledge gained from poorer-quality studies or from their own experience. Even when high-quality research is available, each patient is unique and therefore research results cannot be applied to the individual patient with complete reliability.(15)
Several other factors also require consideration during the clinical decision-making process.(16) Clinically effective interventions may not be cost-effective and healthcare providers may have to make difficult decisionsas to how health funding is spent. For example, there is emerging evidence to support the use of bilayer artificial skin grafts to promote healing, but this procedure is costly and therefore may not be readily available.
Human factors also play a fundamental role in evidence-based decision-making. Clinical expertise may lead a clinician to conclude that although there is evidence to support the use of oral pentoxifylline for promoting healing, the risks for a patient with insufficient renal function outweigh the potential benefits.
A patient's own personal preferences may mean that they are not willing to accept compression bandaging, despite robust evidence of its effectiveness. The clinician needs to consider the relevance of the available research evidence to each patient's individual clinical issue along with the patient's preferences, the available resources and their own clinical expertise.(17)

Conclusion
Not all clinical decisions can be based on good-qualityresearch evidence. However, clinicians have a duty to be aware of the evidence base around a clinical issue and to use this as a starting point from which to begin to consider questions of resources (whether a treatment should be funded), clinical expertise (whether the treatment is suitable for that particular patient) and patient preferences (whether the treatment is acceptable to the patient). Therefore although research evidence alone is an insufficient basis for clinical decision-making, research evidence offers the best foundation for it.

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References

  1. Nursing and Midwifery Council. Research and audit. Available from: http://www.nmc-uk.org
  2. British Association of Dematologists. What is a venous leg ulcer? Available from: http://www.bad.org.uk/public/leaflets/venous.asp
  3. Royal College of Nursing. The management of patients with venous leg ulcers. London: RCN; 2006.
  4. Haynes RB. Of studies, syntheses, synopses, and systems: the "4S" evolution of services for finding current best evidence. ACP J Club 2001;134:A11-A13.
  5. Eriksson E, Eklund AE, Kallings LO. The clinical significance of bacterial growth in venous leg ulcers. Scand J Infect Dis 1984;16:175-80.
  6. Skene AI, Smith JM, Dore CJ, et al. Venous leg ulcers: a prognostic index to predict time to healing. BMJ 1992;305:1119-21.
  7. Trengrove NJ, Stacey MC, McGechie DF. Qualitative bacteriology and leg ulcer healing. J Wound Care 1996;5:59-63.
  8. Gardner SE, Frantz RA, Doebbeling BN. The validity of the clinical signs and symptoms used to identify localized chronic wound infection. Wound Repair Regen 2001;9:178-86.
  9. Palfreyman SJ, Nelson EA, Lochiel R, et al. Dressings for healing venous leg ulcers. Cochrane Database Syst Rev 2006;3:CD001103.
  10. O'Meara S, Al-Kurdi D, Ovington LG. Antibiotics and antiseptics for venous leg ulcers. Cochrane Database Syst Rev 2008;1:CD003557.
  11. Jull A, Arroll B, Parag V, Waters J. Pentoxifylline for treating venous leg ulcers. Cochrane Database Syst Rev 2007;3:CD001733.
  12. Al-Kurdi D, Bell-Syer SEM, Flemming K. Therapeutic ultrasound for venous leg ulcers. Cochrane Database Syst Rev 2008;1:CD001180.
  13. Jones JE, Nelson EA. Skin grafting for venous leg ulcers. Cochrane Database Syst Rev 2007;2:CD001737.
  14. Briggs M, Closs J. The prevalence of leg ulceration: a review of the literature. EWMA J 2003;3(2):14-20.
  15. Straus S, McAlister F, Cook D, Greenhalgh T, Guyatt G. Expanded philosophy of evidence-based medicine. JAMA 2001;211-22.
  16. Guyatt G, Haynes B, Jaeschke R G, et al. Introduction: the philosophy of evidence-based medicine. In: Guyatt G, Rennie D, editors. Users' guides to the medical literature: a manual for evidence-based clinical practice. Chicago: American Medical Association; 2002.
  17. DiCenso A, Cullum N, Ciliska D. Implementing evidence based nursing: some misconceptions. Evid Based Nurs 1998;1:38-40.

Resources
RCN Clinical Guidelines
W: www.rcn.org.uk/development/practice/clinicalguidelines/venous_leg_ulcers
EWMA Position Papers
W: www.ewma.org/english/PositionPapers_en.htm
Cochrane Library
W: www.cochrane.org