The term ‘decubitus ulcer’ strictly speaking refers to ulcers occuring in prolonged recumbancy. The word derives from the Latin decumbere ‘to lie down’. The ulcer forms as a result of pressure hence is more commonly known as pressure sores, although other terms have been used including the old fashioned term ‘bed sores’. None of theterms are strictly accurate, pressure is not the only cause, nor is recumbancy the only vulnerable position. However, when referring to animals, the ulcers are almost always the result of recumbancy therefore decubitus ulcer is the term mostly used in this article Ulcers caused by other means for example from a cast or bandage will be refered to as pressure ulcers.
Campbell and Parish (2010) extensively reviewed previous research and literature and found four common denominators when defining a decubitus ulcer:
They describe that, in the simplest terms, the decubital ulcer is a breakdown of the skin usually over a bony prominence due to compromised blood flow caused by pressure (Campbell and Parish, 2010).
Surprisingly, the condition has only been recognized in its entirety since the 1950s when British nurse, Dorreen Norton, showed that decubitus ulcers could be prevented or treated by physically removing pressure on the skin by turning the patient every 2 hours. Prior to this discovery substances such as methylated spirits and soap were rubbed into the skin, possibly to toughen the skin (Elliot, 2009).
Since that time, much has been learned about the pathogenesis of decubitus ulcers most notably the association between direct pressure and tissue health (Salcido, 2007).
Causes of decubitus ulcers
Decubitus ulcers result from pressure on the skin where the bodyweight presses joints or prominent muscle masses against a surface, e.g. bedding or operating table. As a result, capillaries in the skin are compressed and unable to supply the cells with vital oxygen and nutrients and remove wastes, leading to ischaemic insult. Research using rats has illustrated that varying cycles of ischaemia and reperfusion cause skin injury, while ischaemia alone did not (Shayn et al, 2000). An ischaemia-reperfusion injury is defined as cellular injury caused by reperfusion of blood into previously ischaemic tissue and is considered to be a significant factor in the etiology of decubital ulcers (Shayn et al, 2000).
Prolonged pressure just above the ‘capillary filling’ pressure of 32 mmHg leads to reduced tissue perfusion (Kirman and Molnar, 2010). Constant external pressure for 2 hours or more produces irreversible changes in tissues in animal model studies.
Risk factors
In clinical practice, there are a number of common conditions that can predispose animals to decubitus ulcers (Table 1), but most have immobility in common.
| Sensory perception |
1. Completely limited |
2. Very limited |
3. Slightly limited |
4. No impairment |
| Moisture |
1. Constantly moist |
2. Very moist |
3. Occasionally moist |
4. Rarely moist |
| Activity |
1. No movement | 2 Slight movement |
3. Walks occasionally |
4. Walks frequently |
| Mobility |
1.Completely immobile. |
2. Very limited |
3. Slightly limited |
4. No Limitation |
| Nutrition |
1. Very poor |
2. Probably inadequate |
3. Adequate Eats over ½ most meals | 4. Excellent |
| Friction and shear | 1. Problem |
2. Potential problem |
3. No apparent problem |
The patient is assessed in six categories. Pressure sore risk increases as the score decreases. 15–16 = mild risk, 12–14 = moderate risk, <12= serious risk IV, intravenous
In human health care, decubital ulcer formation is commonly assessed using the Braden scale of risk factors (Braden and Bergstrom, 1989) or the Norton scale for predicting pressure sore risk (Royal Australian College General Practitioners, 2005). These scales have been modified for use with recumbant animals.
There are a number of specific conditions that can indicate that a patient may be more at risk of developing a decubitus ulcer. These include:
Large and giant breeds of dog are also at risk of naturally developing decubital ulcers becuse of their preference for sternal recumbency which puts pressure on their elbows. This can lead to the formation of hygromas (accumulation of fluid in a sac), which can become infected requiring surgical excision (Swaim et al, 1996).
Medium to large dogs lie in lateral recumbancy and change from side to side regularly. Small and medium dogs tend to sit (even paraplegic dogs) on their perianal regions which causes pressure on ischerial tuberosities, which can lead to decubitus ulcer formation.
Not all veterinary clinics are able to manage a paralyzed patient and the immobile animal may need to be transported to a veterinary hospital, which may take several hours. The veterinary nurse must make sure all bony prominences are well padded and that the animal has soft absorbant blankets to lie on to minimize pressure during the journey. Transporting the animal on a padded stretcher with straps to prevent rolling will reduce friction/shear injury.
Classification and pathogenesis
There are four stages in decubitus ulcer formation (Table 2).
| Stage I | Intact skin with non-blanchable redness of a localized areausually over a bony prominence. Darkly pigmented skin may not have visible blanching; its color may differ from the surrounding area (animal fur can be clipped if changes suspected) |
| Stage II | Partial thickness loss of dermis presenting as a shallow open ulcer with a red pink wound bed, without slough. May also present as an intact or open/ruptured serum-filled blister |
| Stage III | Full thickness tissue loss. Subcutaneous fat may be visible but bone, tendon or muscle are not exposed. Slough may be present but does not obscure the depth of tissue loss. May include undermining and tunnelling |
| Stage IV | Full thickness tissue loss with exposed bone, tendon or muscle. Slough or eschar may be present on some parts of the wound bed. Often include undermining and tunnelling |
| Unstageable | Full thickness tissue loss in which the base of the ulcer is covered by slough (yellow, tan, gray, green or brown)and/or eschar (tan, brown or black) in the wound bed |
As previously stated, any animal who is unable to move is at risk of developing decubitus ulcers. Animals are usually covered in fur and often have pigmented skin so it is not always possible to detect stage I ulcers as they involve no tissue loss, just redness (National Pressure Ulcer Advisory Pane,l 2007). If immobility for 2 or more hours (Bansal et al, 2005) is a potential problem the bony prominences should be padded to prevent a stage II ulcer developing (Figure 1).
If pressure is not removed from the animal's bony areas, then stage II damage will occur and this will increase the time for healing. Once ulcers reach stage III (Figure 2) or IV then surgical intervention to remove necrotic tissue is indicated. This will make the patient immobile, potentially creating additional problems.
Prevention
To avoid decubitus ulceration, a good assessment of the animal's abilities using the Braden scale for predicting ulcer risk is needed (Table 1), followed by the implementation of a good nursing care plan. This must include pressure area care, nutrition, skin care and be tailored to the individual animal's needs.
Prevention is key and implementing a thorough plan of nursing interventions can help avoid skin breakdown. Some interventions include:
Ulcer prevention aides
In addition to a good nursing care plan, veterinary nurses should take into account the other aides that are available. Orthopaedic foam can be made into a variety of shapes to suit every patient. As well as dry beds and sheepskins, some larger veterinary hospitals may have air cell mattresses, which can be pumped to different pressures, or foam mattresses with crenelations like egg boxes to relieve pressure on certain areas of the body. Memory foam mattresses mould to the patient's shape with no hard surface to cause pressure (Figure 3). Both gel filled and memory foam products provide a high density mattress. These provide greater durability and consistant support and more generalized distribution of the dog's weight on the bed.
Hoists and slings can be used to hold up an animal, either for exercise or for turning, but care must be taken with straps or belts which may cause friction rubs.Figures 4 and 5 show veterinary hoists produced in the USA. Figure 4 shows the hoist in Figure 5 transfering a large dog.
A foam square placed between the hocks will relieve pressure of bones rubbing together and sheepskin squares can also be used for the patient to lie on. Foam wedges can be used under various areas of the bedding to raise the patient, thereby relieving pressure from a small area.
Although the ‘donut’ style pressure reliever is not advocated in treating decubitus ulcers in people, they have been successfully used in dogs to keep pressure off decubitus ulcers and for decubitus ulcer repair sites on lower limbs (Swaim et al, 1996).
Treatment
Whether an animal develops the decubitus ulcer while in hospital care, or presents with one from home, treatment starts with assessment. A recumbant patient without a decubitus ulcer when admitted is assessed using the Braden scale (Table 1) and preventative measures already described are commenced.
If the patient already has a decubitus ulcer, as diagnosed by the veterinarian, the ulcer is assessed using the NPUAP scoring chart (Table 2). This will determine the type of treatment and expected length of healing time.
Photographs should be taken of the ulcer on admission or when first diagnosed followed by weekly updates to show progress. These should be attached to the patient file or downloaded into the clinical history to provide a comparison during future assessments.
The first step in addressing the wound is to relieve pressure on the area by ensuring frequent repositioning of the patient as well as sufficient physical support and protective padding. Each time the animal is repositioned, a thorough examination of skin must be made to check that the skin has normal temperature and colour indicating good circulation (cold limb temperature could indicate poor circulation to that area, heat could indicate inflammation). The skin around the wound should also be kept dry and the type of bedding (soft) used should minimize friction. Bedding must not be allowed to become creased under an animal as this will put extra pressure on vulnerable areas.
Prolonged recumbency can lead to chronic nonhealing wounds that require constant care and monitoring. Not only is this costly for the client, it can be debilitating and painful for the animal. At this stage, quality of life for the animal should be discussed by the veterinarian with the owner of the animal particularly if the overall prognosis is poor.
Current medical research supports the application of moist dressings (Campbell and Parish, 2010) for secondary healing wounds such as decubitus ulcers (Thomas, 2000). The review of pressure ulcer prevention and treatment by Thomas showed that occlusive dressings are far superior to dry gauze dressings or even saline dressings. It has been shown that the formation of granulation tissue without scarring (replacement tissue) can only take place in a moist wound environment (Svensjo et al, 2000). Topical opioid dressings were found to be most effective in patients with painful decubitus ulcers (Twillman et al, 1999).
Debridement (removal of necrotic tissue under anaesthesia) from a patient with an extensive or chronic wound may be necessary to allow the healing process to begin. Necrotic tissue delays healing by preventing reepithelialization (Campbell and Parish, 2010). This can consist of autolytic debridement using synthetic occlusive dressings, which digests dead tissue utilizing the body's own enzymes present in the wound fluids, maggots to ingest necrotic tissue, forceful irrigation or complete surgical removal of necrotic tissue.
For centuries, honey has been used to control wound infections and aid healing. Clinical trials have shown that pressure ulcers covered with honey-impregnated dressings healed four times faster that with other conventional wound dressings (Yapucu Günes, 2007). Honey dressings also reduced infection within 1 week of application (Efem, 1988).
If large ulcers are present, there may be a deficit in the muscle and exposure of musculoskeletal structure. This may require surgical intervention in the form of debridement and possibly the application of skin grafts to close the wound. Myocutaneous flaps are usually the surgical technique of choice because the flap has its own blood supply and breakdown of the wound due to poor tissue oxygenation is less likely (Minami et al, 1977).
The prognosis for the complete healing of decubitus ulcers is excellent if treated appropriately in the early stages, but according to NPUAP healing usually requires weeks mostly because the wounds are typically located in areas of the body where relief of pressure is difficult to achieve.
How well the ulcer is healing can be assessed using the PUSH tool (Pressure Ulcer Scale for Healing). This is a chart for recording the surface area of the ulcer, type of exudate and the type of wound tissue (National Pressure Ulcer Advisory Panel, 2008)
Conclusion
Decubitus ulcers are the result of a large number of factors related to recumbent and compromised patients. They can be quite debilitating and healing times are increased by a number of factors such as prolonged recumbency, diabetes and malnutrition. Treatment and recovery from decubitus ulcers can be fraught with complications so in most cases, prevention is far easier than the cure. Good nursing care is instrumental to effective treatment of decubitus ulcer wounds, but identification of patients that are at risk from decubitus ulcers can help prevent the problem before it occurs.