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Mixed aetiology leg ulcers

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It is estimated that leg ulcers affect 0.1-0.3% of the population (Nelzen et al, 1996; Callam et al, 1985). This creates a huge resource burden on the health services and, furthermore, has a significant impact on the lives of those who are affected (Rich and McLachlan, 2003).

The care of those with venous leg ulcers has improved considerably over recent decades, but there are new challenges today, as people are now living longer and are more likely to have co-morbidities that affect wound healing.

The aetiology of leg ulcers is thought to fall into the following categories:

- Venous 75%;

- Arterial 20%;

- Other 5%.

Of those with venous aetiology, 10-15% have a significant level of arterial impairment (Callam et al, 1985). However this is an estimate, and the number of people with mixed aetiology ulcers will probably increase as the population ages. Currently, national guidelines (Clinical Resource Efficiency Support Team, 1998; RCN, 1998; Scottish Intercollegiate Guidelines Network, 1998) do not deal specifically with mixed aetiology ulcers, although new RCN guidelines are to be published soon.

Types of leg ulceration

Leg ulceration is not a diagnosis; it is the underlying aetiology that defines the ulcer and the management decisions (Young, 1994). It is crucial that a patient is assessed before treatment decisions are made, and that ongoing assessment takes place, as disease processes such as arterial insufficiency can be progressive (Vowden and Vowden, 1996).

Venous ulcers - These develop owing to chronic venous hypertension, which arises as a result of ineffective venous return from the lower legs. This increases the pressure in the superficial venous system, which affects the exchange of nutrients in the capillary bed. Fluid is not then reabsorbed effectively into the venous system from the interstitial spaces, resulting in oedema. This means that the tissues are undernourished, and waste metabolites such as haemosiderin, fibrin and other products collect in the interstitial spaces. Staining of the skin results, together with varicose eczema and risks to skin integrity from infections such as cellulitis, and ultimately ulceration may occur (Fig 1) (Morison and Moffatt, 2004).

The aim of treatment is to reduce backflow, venous hypertension and oedema. In some circumstances, surgical intervention is an option.

Arterial ulcers - These occur when the normal flow of blood through the arteries is impaired, usually from atherosclerotic plaque lining the arterial wall. This reduces the lumen of the vessel and subsequently affects the supply of oxygen and nutrients to the lower leg. As a result of this, the tissues are poorly perfused and are at risk of sudden and dramatic ulceration following injury.

The lack of an adequate oxygen supply means that the wound can be very slow to heal, or may not heal at all (Herbert, 1997). Additional risks include thrombus formation on areas of atheroma, which can occlude the vessel completely.

Surgical intervention, such as angioplasty or a bypass may help restore circulation. However, the problem may be too extensive or the patient may not be fit.

If surgery is not an option, the management of people with arterial leg ulcers centres on symptom management, particularly their pain, which is a significant issue in arterial disease (Herbert, 1997). Box 1 lists the risk factors for arterial disease.

Mixed aetiology ulcers - People with these ulcers have venous disease and a significant level of arterial disease, but their arterial blood supply is not yet poor enough to cause critical ischaemia.

 

 

The key clinical factor in mixed aetiology ulceration is that, without intervention, arterial disease is progressive and that, eventually, the arterial problem will take precedence over the venous problem in treatment decisions.

Assessment

Patients must have a full assessment in order to determine the aetiology of their ulcer and to identify any other disease processes and risk factors for ulceration and delayed wound healing (Morison and Moffatt, 2004). In addition, it is important to identify any risk factors associated with arterial disease.

Assessment includes the following:

- History-taking, including medical history and lifestyle;

- Clinical examination of the limb to identify whether or not it is oedematous;

- Observation of the general condition of the skin;

- Blood tests to screen for conditions such as anaemia and diabetes.

The arterial blood supply to the lower limb should be measured using a hand-held Doppler, which will record the ankle brachial pressure index (ABPI). This is only a single component of the assessment: the ABPI must never be considered in isolation from the rest of it.

It is important to be aware of conditions that may give an erroneously elevated ABPI reading, such as when the atherosclerotic plaque in the artery is calcified and incompressible. This sometimes occurs in patients with diabetes. There are other vascular assessment tests available; for an overview of these see legulcerforum.org and link to ‘Professional Leaflets’).

Management

Compression therapy - The management of venous ulcers aims to reduce venous hypertension and the pressure at capillary level in order to restore normal capillary dynamics. This is usually achieved by a combination of leg elevation, exercise and the application of external compression therapy to the limb (Dealey, 2005). It has been identified that high levels of compression are more effective in achieving this than lower levels of compression, but that this should be used only in the absence of significant arterial disease (Fletcher et al, 1997).

When an ulcer has mixed venous and arterial aetiology the aim is to treat both diseases effectively. But to balance safety and effectiveness there has to be a compromise, so reduced compression can be used. The aim is to reduce the oedema and venous pressure by using external compression but at a level that does not significantly squeeze the arteries and compromise arterial blood flow, which may cause serious problems (Ghauri et al, 1998). Applying full compression to a limb with an ulcer with mixed aetiology may be catastrophic (Ghauri et al, 1998). This fact emphasises the importance of assessing patients thoroughly before clinical decisions are made about treatment.

In the absence of empirical evidence to support the level of compression that would be desirable in mixed ulcer disease, different trusts have adopted their own criteria. These are generally based on the ABPI measurement which, although it has been accepted as an effective way of measuring arterial blood flow, is not without error in technique or interpretation. It is important, therefore, to consider other factors, such as co-morbidities, pain, limb shape and circumference when deciding on treatment options for patients.

According to Arthur and Lewis (2000), all patient-related factors need to be taken into account. However, any decision taken to apply reduced compression to an ulcer of mixed aetiology must be undertaken only by a specialist practitioner.

Reduced compression is commonly used when a patient’s ABPI is between 0.8 and 0.5. When an ABPI is below 0.5, critical ischaemia is indicated, in which case no compression should be applied (Caruana et al, 2005; Marston and Vowden, 2003). Patients need to be monitored regularly for increased levels of pain, or a reduction in ABPI. If the patient’s pain increases, the ulcer fails to respond or deteriorates, or the ABPI reduces, further investigations should be considered.

Practical application of reduced compression - There is general consensus that pressures around 40mmHg at the ankle are sufficient to reverse venous hypertension. However, this depends on the characteristics of the bandage and the circumference of the limb. Laplace’s Law is used to explain this (Clark, 2003). The law says that pressure will depend on the following:

- The number of layers of bandage applied;

- The extent to which the bandage is stretched;

- The circumference of the ankle and leg (the larger the circumference, the lower the pressure).

The above criteria thus mean that reduced compression can be achieved by:

- Reducing the number of layers of a single bandage (applying them in a spiral instead of as a figure of eight);

- Reducing the number of layers in a multilayer system;

- Reducing the stretch of the bandage (25% extension rather than 50%).

There is little research to suggest the optimum level of reduced pressure and the best way to achieve reduction. Stacey et al (2002) define reduced compression therapy as 15-25mmHg at the ankle, but this could increase to 30mmHg. Ghauri et al (1998) define it as 30mmHg and Arthur and Lewis (2000) as 14-17mmHg.

Class 1 and 2 compression hosiery can be useful, as can short-stretch bandages, because there is relatively low pressure on the limb when the person is at rest but higher pressure is exerted on movement (Stacey et al, 2002).

It is important to remember that people with any degree of arterial disease are particularly at risk of compression-related trauma. Therefore, an experienced leg ulcer practitioner must always be involved in any decisions that are made about reduced compression.

Symptom management

Pain - Pain is a significant factor in arterial disease and is the single most important symptom; indeed it may be pain that prompts a patient to seek medical advice. The pain is usually related to exercise, and results from an abnormal accumulation of metabolic products in the muscle (Herbert, 1997). Trauma or infection may also increase metabolic products.

Severe arterial disease affecting the lower extremities can compromise capillary perfusion when the patient is resting, particularly when the legs are elevated, which results in ischaemic or nocturnal rest pain. Pain experienced by people with arterial and venous leg ulcers is frequently underestimated, and inadequately treated (Ebbeskog and Ekman, 2001).

Oedema - Oedema occurs with venous hypertension as a result of abnormal capillary dynamics, but gravitational oedema also occurs with arterial disease when the limb is dependent and inactive.

Patients with pain from arterial disease may have a disrupted sleep pattern from sitting for long periods with their legs in a dependent position in an attempt to obtain pain relief. This has a significant impact on the development of oedema (Herbert, 1997).

Skin care - Skin problems can occur with both venous and arterial disease and meticulous care is essential to prevent further tissue breakdown. The skin needs to be protected as much as possible from the effects of trauma. Patients with venous hypertension tend to develop hyperkeratosis (a build up of dry skin that can feel very itchy). There is also a risk of stasis eczema owing to the collection of waste products trapped in the interstitial spaces, and this will contribute to the irritation.

An emollient should be used for patients with skin problems, but those containing sensitisers, such as perfumes, or preservatives such as parabens, should be avoided (Cameron and Newton, 2004). Patients should be encouraged to report any problems with itching and irritation.

Other diseases

Mixed aetiology ulcers are very complex and can change their character very rapidly as, for instance, with progressive arterial disease. It is important that other co-morbidities are recognised, as these may add to the complexity of the condition. These may include conditions that give rise to the risk of vasculitis, such as rheumatoid arthritis and other connective tissue/inflammatory disorders.

Vasculitis results from an abnormal activity of the white blood cells in the arterial micro-circulation, and leads to adhesion of these cells to the intima (lining of the vessel), causing occlusion. The high pressures exerted by bandaging may lead to further damage to these fragile vessels, with subsequent skin damage, necrosis of tissue and considerable pain.

People with rheumatoid arthritis are especially vulnerable to leg ulceration because of their reduced joint function and mobility. In addition, long-term steroid therapy will cause thinning of the skin, making it more vulnerable to trauma (Morison and Moffatt, 2004). For these reasons, compression therapy has to be used with caution so as to reduce the risk of causing pain and damage to the limb (Dealey, 2005).

People with diabetes may also have venous disease. They are also at risk of infection and of developing atherosclerosis, and may have poor blood flow through their micro-circulation as a result of increased hypercoaguability (an increased tendency for blood to clot) (Herbert, 1997).

It is important that any co-existing disease is identified in a patient who presents with a leg ulcer so that the correct underlying aetiology for the ulcer is established and to ensure that treatment does not cause further problems.

Involving the patient

Patients have no control over their age or their genetic profile (Vowden and Vowden, 1996), but they do have control over factors such as smoking, obesity and exercise. They need to be encouraged and supported to adopt a healthier lifestyle, which must also include taking care of their skin, and prevention of tissue damage. In addition, it is important that they are aware of the channels of communication to healthcare professionals so that they can report promptly any changes in pain, sensation and colour in their legs.

Conclusion

Patients presenting with an ulcer where mixed disease is present pose a challenge to the practitioners involved in their care. Balancing the management of venous hypertension with treatment for arterial disease requires a sound knowledge of the underlying disease processes. Furthermore, access to available evidence to support the treatment decisions is important.

Unfortunately, empirical evidence may be lacking and treatments may therefore be based on local expert consensus. It is important that practitioners involved in the care of such patients are aware of their own limitations and that they involve the multidisciplinary team as appropriate.

This article has been double-blind peer-reviewed.

For related articles on this subject and links to relevant websites see www.nursingtimes.net

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