It is estimated that 110 000 new pressure ulcers develop each year (Department of Health and Social Care, 2018), costing the NHS between £1.4 and £2.1 billion annually (European Pressure Ulcer Advisory Panel (EPUAP) et al, (2019). The average length of a hospital stay for a patient with a pressure ulcer is around 25 days (NHS Improvement, 2018).
Pressure ulcers are caused by tissue damage when the blood supply to an area of skin is impaired because of significant pressure; they are often preventable (National Institute for Health and Care Excellence (NICE), 2014). Clinical interventions for pressure ulcer prevention include holistic assessment, risk assessments and preventive measures (Mitchell, 2018). Malnutrition is a common complication in wound healing and has been cited as a key factor in the development of pressure ulcers (NICE, 2014).
Pressure ulcers, as with all hard-to-heal wounds, require sufficient macronutrients and micronutrients, iron and fluid for optimal healing. Energy is required for increased cell activity and collagen synthesis. Protein—as amino acids, in particular arginine and glutamine—is vital for tissue repair, fibroblast proliferation, collagen synthesis, angiogenesis and immune function. Inadequate amino acids delay healing by keeping the wound in the inflammatory stage (Figure 1).
Fatty acids are essential for the synthesis of cell membranes, as an energy source, and are important for the development of inflammatory mediators. Iron is required for an adequate immune response, collagen synthesis and to transport oxygen to the wound, and certain micronutrients are particularly important for wound healing (Sherman and Barkley, 2011; Medlin, 2012; Saghaleini et al, 2018; Munoz et al, 2020; Tuz and Mitchell, 2021). These micronutrients include:
- Vitamin C: fundamental for collagen formation, proper immune response and monocyte migration in the inflammatory stage, and also helps with iron absorption
- Zinc and copper: needed for epithelialisation and granulation tissue formation, B and T lymphocyte and neutrophil proliferation and protein synthesis
- Vitamin E: essential for optimal immune function and assists with healthy tissue formation
- Vitamin A: increases the inflammatory response and helps with collagen formation
- Iron: required to assist with various molecular mechanisms in the skin. Iron deficiencies can affect cell proliferation and differentiation, protein synthesis and regulation of macrophage function during the inflammatory phase.
In addition, there are several factors relating to malnutrition that impact on wound healing. Pain from pressure damage can affect patient participation and appetite, which can further impede their nutritional intake. Nutrition can have a significant impact on the function of the central nervous system, which in turn can affect the patient's experience of pain and the gut health status can affect experience of nociceptive pain (Pribyl, 2018).
Age is also an important factor. Older patients often have multiple comorbidities, which can affect mobility, hand dexterity, ability to swallow, appetite and continence. All of these can have a significant effect on a patient's nutritional intake, but also their ability to socialise, which can contribute to loneliness and depression, and can further impede eating habits. The quality of a patient's diet can be linked to social support, isolation and participation in leisure activities (Bloom et al, 2017). People on a lower income have been found to have lower vitamin C levels (Bold, 2020). Up to 51% of patients with a pressure ulcer were found to have a nutritional deficiency (Guest et al, 2017). Only 30% of adults are getting the recommended five portions of fruit and vegetables a day (British Nutrition Foundation, 2019) and an association has been found between nutritional deficiency and the development of pressure ulcers (Brito et al, 2013).
The EPUAP et al (2019) guidelines recommend that a patient with a pressure ulcer requires 30-35 kcal of energy per 1 kg of body weight, in addition to 1.2–1.5 g of protein per 1 kg of body weight. A high-calorie diet and protein-fortified foods or oral supplements are recommended for all patients at risk of developing a pressure ulcer and who are at risk of malnutrition (EPUAP et al, 2019). These supplements must be prescribed on an individual basis following a full risk assessment. Additionally, high-calorie, high-protein, arginine, zinc and antioxidant oral nutritional supplements should be prescribed for patients with a category 2 or more pressure ulcer who are malnourished or at risk of malnutrition (EPUAP et al, 2019). Nutritional supplements are not required to treat patients with pressure ulcers if nutritional intake is adequate (NICE, 2014). However, it is often a health professional's subjective viewpoint as to what is considered ‘adequate intake’, and since a chronic inflamed wound causes a catabolic state (Munoz et al, 2020), it would follow that a person's nutritional intake should be higher when they have a pressure ulcer. EPUAP et al (2019) recommend increased protein intake in patients with a pressure ulcer: up to 2 g/kg for patients with a category 4 pressure ulcer. Adequate fluid intake for an individual with or at risk of a pressure injury should be provided (EPUAP et al, 2019; Posthauer et al, 2015); and 30–40 ml per kg of body weight in those with healing pressure ulcers (Saghaleini et al, 2018).
Intake of oral supplements has been found to improve patients' energy and protein requirements during wound healing significantly (Roberts et al, 2016). These interventions should be used in conjunction with other forms of nutritional assistance such as nutrition counselling and education, modifying food textures to increase food intake and offering assistance with eating and drinking (EPUAP et al, 2019). Oral supplements are more expensive and should be prescribed following a full clinical assessment. However, if appropriately prescribed, they can reduce dressing changes by improving wound healing and lowering overall wound-care costs (Elia et al, 2016).
In older adults, the risk of dehydration is high, typically in those who have decreased lean body mass and increased body fat, reducing the amount of water stored in the body. These factors, coupled with the likelihood of having multiple morbidities, can increase the risk of dehydration, which can delay wound healing. Wounds require a moist environment for the fluid to transport nutrients into the wound (Wounds UK, 2013). A reduced body mass also means that protein intake needs to be higher. However, older people have been shown to have reduced protein intake due to multiple morbidities and decreased mobility (Acton, 2013). If lean body mass is lower, the body must both rebuild that mass and heal the wound at the same time, thus wound healing is slowed (Munoz et al, 2020). Quain and Khardori (2015) found that, with a loss of 10% lean body mass, immunity was impaired; with 20% loss of lean body mass, decreased wound healing and thinning of the skin occurred; and 30% loss of lean body mass halted wound healing and led to an increased likelihood of new wounds forming. Protein needs are increased by 250% in all stages of wound healing (Molnar et al, 2014). Excessive exudate in all hard-to-heal wounds can also lead to protein deficiency (Wounds UK, 2013) and pressure ulcers and chronic inflammation can induce a catabolic metabolic state. Elevated cortisol levels from the adrenal cortex leads to a catabolic effect and loss of protein in addition to poor albumin synthesis from the inflammatory response, resulting in a protein deficiency for patients with chronic wounds (Moor, 2019; Cox and Rasmussen, 2014).
Despite the evidence supporting the importance of nutrition in healing pressure ulcers, when evaluating the effectiveness of supplementing with specific nutrients, results have been divided. Langer and Fink (2014) assessed 23 randomised controlled trials and found a significant improvement in pressure ulcer healing from arginine-enriched supplementation, but no significant healing rates from zinc supplementation. With fatty acid supplementation, omega 3 supplements have been found to reduce ulcer size and limit deterioration of the wound (Cox and Rasmussen, 2014; Soleimani et al, 2017). A high protein diet and oral supplements have been found to reduce the size of the wound but not the depth. Cawood et al (2012) found that high protein- and arginine-enriched nutritional supplements can improve pressure ulcer healing rates in patients (Theilla et al, 2012; Neyens et al, 2017; Cereda et al, 2017).
Obesity has been linked to impaired wound healing with an increased body fat linked to lower lean body mass and protein deficiency (Munoz et al, 2020). Obesity can also cause cell ischaemia from the excess subcutaneous tissue, this is due to poor circulation in adipose tissue, which results in reduced collagen synthesis and reduced ability to fight infection (Pierpont et al, 2014). Growth factors in fatty tissue can cause low-grade inflammation in the body, which will affect the body's immune response. Obese surgical patients can have a higher number of micro- and macro-nutritional deficiencies. Other factors that can cause pressure ulcers and a delay in wound healing in obese patients include limited mobility to reposition, skin folds which can trap moisture and increase the risk of pressure damage from shear and friction (Mitchell, 2018). Obesity is still not widely recognised as being a risk factor for malnutrition and the Malnutrition Universal Screening Tool (MUST) score does not score for obesity. Patients will score a zero, in the same category for normal-weight individuals (BAPEN, 2011).
Appropriate screening and assessments such as the MUST nutritional screening score, Waterlow and Braden risk assessment tools are essential to diagnose malnutrition in patients. However, these do not reduce the importance of clinical judgement and an individually tailored care plan. Risk assessments will not take into account certain elements, such as the presence of oedema or obesity. A holistic approach is necessary, involving risk-assessment tools, education and training for health professionals on the importance of patients' nutritional needs when managing pressure ulcers.
It is important for all health professionals to holistically risk assess patients who are at risk of developing pressure ulcers or who currently have a pressure ulcer. Prescription of nutritional supplements should be on an individual basis and supported with patient education, advice on how to fortify the patient's diet, intervention or assistance from the multidisciplinary team and regular review.
KEY POINTS
- Malnutrition is a key factor in the development of pressure ulcers
- Older people are more likely to develop pressure ulcers because of a lack of mobility, comorbidities and malnutrition
- Important nutrients for wound healing include macronutrients (particularly protein) and micronutrients (such as vitamin C, E and A, zinc and iron)
- Individual assessments of patients with pressure sores is vital so that malnutrition can be addressed and plans put in place for nutritional support, pressure relief and wound care
CPD reflective questions
- How often do you assess the nutritional status of patients with wounds?
- Is there any additional nutritional advice or support you could give patients with wounds?
- What would you change about your current practice in this area?