María D. Ballesteros-PomarMD, PhDEndocrinology and Nutrition Department, Clinical Nutri-tion Unit.

Complejo Asistencial Universitario de León Altos de Nava s/n 24008 León, Spain.

Correspondence:mdballesteros@telefonica.net

Conflicts of interest: None

Scientific Communication

Wound risk and prevention in obesity: The role of nutrition

adrid · Spain

EWMA n GNEAUPP 2014

Submitted to the EWMA Journal, based on a pres-entation given at The European Society for Clinical Nutrition and Metabolism (ESPEN) Guest Session: Obesity and wound management: The role of nutrition at the EWMA - GNEAUPP 2014, Madrid

INTRODUCTIONObesity is a worldwide problem, not only because of its serious medical comorbidities but also due to its increasing prevalence. It has recently been estimated that the prevalence of obesity has nearly doubled since 1980; 35% and 11% of adults older than 20 years of age are now overweight or obese, respectively, and 65% of the world’s population live in nations in which people who are overweight or obese are more likely to die than people who are underweight1. Therefore, a growing number of obese people will need medical assistance. The purpose of this short review is to address the nutri-tional aspects of wound risk and prevention in obese people.

WOUND RISK FACTORS IN OBESE PEOPLEObese people often have several wound risk factors, as shown in Table 1. Some of these may be preventable, but others are not. In addition, obesity may impair the body’s normal reaction to the effects of gravity. Pressure causes the brain to order a positional change to relieve ischemia, but positional changes may be challenging for obese people and their caregivers, leading to increased susceptibility to pressure sores2.

SKIN DISORDERS IN OBESE PEOPLEObesity and associated comorbidities increase the likelihood of impaired skin integrity and slow-to-heal wounds. Therefore, obese people are at risk of developing pressure ulcers, perigenital irritant dermatitis due to urinary and/or fecal incontinence, benign (e.g., candidal intertrigo, erythrasma) or more serious (e.g., cellulitis, necrotizing fasciitis) skin infections, venous ulcers, diabetic foot ulcerations, and surgical site infections3.

Obese people face numerous challenges in maintaining their skin integ-rity4 due to many pathogenic factors5, as shown in Figure 1. Obese people are at risk of delayed wound healing due to reduced oxygen and nutrient perfusion as a result of cardiovascular changes. Furthermore, adipose tissue has a relatively reduced blood supply, leading to inadequate oxygenation. Hypoventilation is also common in obese individuals, which reduces tissue oxygenation4.

Furthermore, moisture and microorganism collection in the skin folds of obese individuals can also increase the risk of infection and decrease skin integrity. Immobility, friction, and shear due to substantial weight stress the skin’s barrier function. Nutritional aspects also have a central role in the pathogenesis of skin disorders in obese people. In particular, obese people

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may be malnourished despite their physical appearance. This issue will be addressed in the present overview, as malnutrition can lead to inadequate protein, vitamins, and nutrients that are essential to wound repair4.

THE ROLE OF VASCULARITY AS A WOUND RISK FACTOR IN OBESE PEOPLESome recent reviews and studies have addressed the role of vascularity as a wound risk factor in obese people5-7. An inherent decreased vascularity of adipose tissue has been described in obese people, and increased adiposity induces a signalling cascade that positively feeds back to impair angiogenesis and cause chronic low-grade inflammation.

In addition, increased expression of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), an intracellular gluco-corticoid-amplifying enzyme, has been observed in obese people. As glucocorticoids suppress angiogenesis, the el-evated level of 11βHSD1 serves to amplify the inhibi-tory effects of glucocorticoids. As adipose tissue becomes hypoxic from impaired angiogenesis, hypoxia-inducible factor 1 alpha (HIF1β) levels increase and initiate local inflammation and fibrosis, which further impair the ang-iogenic process and wound healing. Other microvascular abnormalities linked to obesity include reduced nitrogen oxide availability, which impairs microvascular rarefaction, and prolonged elevation of free fatty acids in the blood due to increased fat mass, which impairs capillary recruitment5.

In surgical wounds, the increased tension on wound edges that frequently occurs in obese people contributes

to wound dehiscence8. Wound tension increases tissue pressure, reducing microperfusion and the availability of oxygen to the wound. The increase in pressure ulcers or pressure-related injuries in obese individuals is also influ-enced by hypovascularity, as poor perfusion makes tissue more susceptible to this type of injury. Venous insuffi-ciency is another vascular factor associated with the devel-opment of chronic wounds and delayed wound healing5.

OTHER PATHOGENIC MECHANISMS OF WOUND RISK IN OBESE PEOPLE Beyond impaired angiogenesis and vascularity, chronic low-grade inflammation associated with obesity is another important pathogenic mechanism of skin disorders and impaired wound healing. Obesity-related microangiopa-thy and alterations in immune mediators may lengthen the inflammatory stage of wound healing and leave obese individuals more susceptible to infections.

Oxidative stress has also been linked to obesity, es-pecially abdominal obesity, through a deficiency in adi-ponectin, an adipocytokine that protects against oxidative stress and inflammation. Low adiponectin levels impair wound healing via two mechanisms: impaired angiogenesis and impaired keratinocyte proliferation and migration, which is a critical process in the re-epithelialisation phase of wound healing4,5. Another aspect of wound healing that is potentially affected by a hypoxic environment in obes-ity is the capability of fibroblasts to synthesise collagen5.

TABLE 1. WOUND RISK FACTORS IN OBESE PEOPLE.

• Advanced age

• Cognitive impairment/altered sensory perception

• Hypoxia, infection/sepsis

• Intensive care unit experience, especially vent-dependency

• Hyperglycemia/diabetes

• Inadequate perfusion/oxygenation/ circulation

• Reduced mobility and difficult positional changes

• Multiple trauma/burns

• Pre-operative illnesses/co-morbidities (e.g., cardiovascular disease)

• Some disease states that cause hyper- metabolism and increase nutritional risk

Figure 1. Pathogenic mechanisms of wound risk in obese people (adapted from Pierpoint et al.5).

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DIABETES AND WOUND HEALING IN OBESE PEOPLEObesity is often associated with metabolic complications, with diabetes being one of the most relevant complications that also has an important role in wound risk and impaired healing. Poor blood glucose control impairs wound healing and increases risk of infection, and the metabolic stress caused by the wound further increases blood glucose.

In diabetic patients, foot ulcers and pressure-related chronic non-healing wounds are always accompanied by hypoxia9, resulting from insufficient perfusion and an-giogenesis8. Hypoxia may further increase the early in-flammatory response, which prolongs injury by increas-ing levels of oxygen radicals. Hyperglycemia also increases the production of oxygen radicals, thereby contributing to oxidative stress. The formation of advanced glycation end products under hyperglycemic conditions is associated with impaired wound healing. High levels of metallopro-teases found in diabetic foot ulcers and chronic wounds are also associated with tissue destruction and inhibit normal repair processes. Diabetic patients exhibit dysregulated cellular functions leading to inadequate bacterial clearance and delayed or impaired repair, such as defects in T-cell immunity, leukocyte chemotaxis, phagocytosis, bacteri-cidal capacity, and dysfunctional fibroblasts and epidermal cells10. Diabetic neuropathy also contributes to impaired wound healing. Figure 2 shows factors that contribute to impaired healing in individuals with diabetes.

Scientific Communication

Figure 2. Potential effects of diabetes on wound healing. MMPs, matrix met-alloproteases; ROS, reactive oxygen species; AGEs, advanced glycation end products (adapted from Guo et al.8.

MALNUTRITION AND WOUND HEALINGAs previously mentioned, obesity does not necessarily im-ply a good nutritional status. Obese people are sometimes malnourished because of bad nutritional habits or fad di-ets, but malnutrition is difficult to detect. This paradoxical malnutrition results from a calorie-dense diet that is high in carbohydrates and fats and low in vitamins and miner-als5. Many micronutrient and macronutrient deficiencies have been described in obese people11. Among 232 obese individuals studied by Ernst et al12. before bariatric sur-gery, 12.5% were deficient for albumin, 8.0% for phos-phate, 4.7% for magnesium, 6.9% for ferritin, 6.9% for hemoglobin, 24.6% for zinc, 3.4% for folate, 18.1% for vitamin B12, 32.6% for selenium, 5.6% for vitamin B3, 2.2% for vitamin B6, 2.2% for vitamin E, and 25.4% for 25-OH vitamin D. Albumin deficiency and anemia were positively correlated with body mass index (BMI), and 48.7% of the obese people included in the study showed at least one nutritional deficiency. As proper wound healing requires adequate levels of vitamins and minerals5, obese people may be at risk of impaired wound repair.

Therefore, obese people may have depleted lean body mass and protein stores while maintaining high levels of adipose mass and may be deficient in many vitamins and minerals needed for healing. Furthermore, detecting mal-nutrition is not easy in these individuals, as many nutrition screening tools rely on BMI or percentage weight loss, making it difficult to assess malnutrition.

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PREVENTION OF WOUNDS IN OBESE PEOPLESome preventative measures might decrease the risk of skin breakdown and maximise wound healing in obese peo-ple13. It is very important to maintain skin integrity using cleansers, lotions, moisture barrier ointments, and sealants. Also, patient independence and mobility should be pro-moted through the use of supplies, equipment, adaptive devices, and rooms designed for obese patients. Special attention should be paid to tube site care, positioning, and stabilisation. Leg elevation and external compression to encourage fluid recirculation is also important to avoid pressure sores. Furthermore, an adequate staff-to-patient ratio significantly helps to prevent sores13.

ROLE OF NUTRITION IN PREVENTING PRESSURE SORESEvidence-based guidelines on pressure ulcer prevention and treatment that have been developed by the European Pressure Ulcer Advisory Panel (EPUAP)14 and the Ameri-can National Pressure Ulcer Advisory Panel (NPUAP)15 specifically address the role of nutrition in preventing pres-sure sores. First, general recommendations are made for the screening and assessment of nutritional status of every individual at risk for pressure ulcers, as the early identi-fication and management of undernutrition can prevent pressure ulcer development. The guidelines suggest using any valid, reliable, and practical tool for nutritional screen-ing that is quick and easy to use and acceptable to both the individual and health care worker as well as having a nutritional screening policy in place in all health care settings. The Braden Risk Assessment Scale for predicting pressure ulcer risk includes a nutrition subscale that can be used in the nutrition screening and assessment process16. The problem for obese people is that any tool based on

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Pierpont YN, Dinh TP, Salas RE, Johnson EL, Wright TG, Robson MC, Payne WG. Obesity and surgical wound healing: a current review. ISRN Obes. 2014 Feb 20;2014:638936.

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body weight may underestimate malnutrition, and there is currently no screening tool validated for obese individuals.

Second, the guidelines propose providing nutritional support to each individual with nutritional and pressure ulcer risks by performing nutritional assessment, estimat-ing nutritional requirements, comparing nutrient intake with estimated requirements, providing appropriate nutri-tion intervention based on an appropriate feeding route, and monitoring and evaluating nutritional outcome. In-dividuals with nutritional and pressure ulcer risks should receive at least 30-35 kcal per kg body weight per day, with 1.25-1.5 g/kg/day protein and 1 ml/kcal/day fluid intake. Obese individuals should not be underfed when at wound risk. When estimating their energy needs, the use of adjusted body weight or specific formulae should be considered. In obese people, beware of calories, but maintain or increase protein supply.

Third, a specific recommendation is to offer high-protein mixed oral nutritional supplements and/or tube feeding in addition to the usual diet to individuals with nutritional and pressure ulcer risks. This recommendation is based on a systematic review and meta-analysis showing a 25% reduction in pressure ulcer development in at-risk patients with high-protein oral nutritional supplements (250-500 kcal/day) compared to routine care17. Obese people should not be excluded from this recommendation when they are either malnourished or at high nutritional risk. A decision tree on nutrition in pressure ulcers pre-vention and treatment has been published by EPUAP14.In conclusion, obesity itself should be recognised as a rel-evant risk factor for wounds, even more so if complicated by diabetes or cardiovascular disease. Also, as obese people may be malnourished, nutritional assessment and manage-ment, as in any other at-risk patient, is vital for wound prevention.

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