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Nutrition 411: Nutrition Implications for Postsurgical Wound Healing
An abundance of research supports nutrition guidelines for treating pressure ulcers, but published guidelines on medical nutrition therapy for postsurgical wounds do not exist. Surgical wounds are distinctly different from chronic types of wounds; key factors in nonhealing surgical wounds are ischemia and bacterial colonization, which stall healing in the inflammatory stage.1 Primary wound healing typically begins within hours of closing a surgical incision.2 Nevertheless, the principle goals of wound healing are to eliminate factors that may complicate or delay wound healing, and then optimize the wound healing environment3,4 (see Table 1). Some factors that may complicate or delay wound healing can be addressed (at least partially) through nutrition. 
Malnutrition puts stress on the immune system and is a risk factor for poor wound healing and other postoperative morbidities and mortality5 (see Table 2 and Table 3). Postoperative malnutrition is associated with higher complication rates.6 Deficiencies in a variety of nutrients can impair wound healing; severe protein deprivation is associated with an increased rate of wound infection. Superficial surgical site infection (SSI) is one of the most frequent hospital-acquired infections on surgical floors.7 One study found that the best predictor of SSI was the preoperative serum albumin level.8 Addressing malnutrition preoperatively may promote faster wound healing after surgery.5
Fast-Track Protocols
According to the European Society for Clinical Nutrition and Metabolism (ESPEN),9 the main goals of perioperative nutrition support are to minimize negative protein balance in order to maintain muscle, immunity, and cognition and promote postoperative recovery. Guidelines from ESPEN on parenteral nutrition (PN) following surgery indicate that only a small number of patients should benefit from this type of therapy due to the introduction of modern surgical practices that use “enhanced recovery after surgery (ERAS) protocols” that lead to most patients eating regular food within 1 to 3 days. ERAS, also known as “fast-track” protocols, are multidisciplinary perioperative pathways designed to speed surgical recovery. Thus, patients identified preoperatively as severely malnourished who cannot obtain sufficient calories orally or enterally may benefit from 7 to 10 days of PN, but oral and enteral routes of nutrition should be given preference in postoperative patients.9
Melnyk10 notes that adoption of ERAS protocols has been slow despite the strong evidence in their favor. Traditional feeding practices of surgical patients frequently contribute to malnutrition; such practices include nil per os (NPO) status preoperatively, delayed feeding while awaiting signs of the return of bowel function, and a slow advancement of the diet from clear liquids. American Society for Parenteral and Enteral Nutrition (ASPEN) recommendations indicate that enteral nutrition (EN) can be safely administered in the intensive care unit despite mild to moderate ileus, and that evidence of bowel motility is not required.11 In addition, perioperative NPO status may propagate ileus and should be minimized. Other fast-track protocols include the use of pre/probiotics, oral carbohydrate loading, limiting fasting to 3 hours, immediate initiation of a regular diet post surgery, and the use of chewing gum.10,12
Open Heart Surgery
SSI is a significant cause of morbidity and mortality following coronary-artery bypass grafting (CABG).13 Diabetes is associated with post-CABG infection; thus, perioperative glycemic control is of great importance for optimizing wound healing. Deep sternal wound infection occurs in 1% to 2% of patients who undergo median sternotomy following CABG.14 Up to 25% of adults undergoing cardiac surgery are malnourished, and this may directly hinder myocardial metabolism.15 Preoperative unintentional weight loss 10% within 6 months and body mass index (BMI) £21 are independently associated with post-CABG complications, including infection, and may be good screening indicators.16
A high incidence of metabolic syndrome can be expected in patients undergoing cardiac surgeries. Metabolic syndrome — ie, the presence of a cluster of risk factors that include abdominal obesity and elevated blood sugar, blood pressure, and triglyceride levels — significantly increases risk for diabetes, heart attack, and stroke. This syndrome has been associated with an increased risk of post-CABG wound infection but not mortality; this may be due to a heightened systemic inflammatory response directly related to the pro-inflammatory state associated with the syndrome.17 Some studies have found that a high BMI (>30–40), which is a risk factor for metabolic syndrome, may be associated with complications that include SSIs, especially in the chest and lower limbs. As such, it has been suggested that a diagnosis of metabolic syndrome may be used to predict postoperative complications, including infections and poor wound healing.
Obese Adults
An ASPEN consensus recommendation provides guidance on nutrition therapy for critically ill adults.11 Noting the lack of literature available to guide nutrition therapies for this population, these consensus recommendations include some guidelines related to wound healing. Specifically, if BMI >30, EN should aim for 60% to 70% of calorie needs (11–14 kcal/kg actual body weight [BW] or 22–25 kcal/kg ideal BW). Protein is noted to be of the utmost importance to promote wound healing in critically ill patients. Surgical wounds may lose protein through exudate. Protein should provide 2.0 g/kg ideal BW when BMI = 30–40, and 2.5 g/kg ideal BW when BMI >40, an amount sufficient to meet protein requirements and maintain a neutral protein balance while allowing for wound healing. Glucose (205–275 g/day) should be provided to promote wound healing in this population, and arginine is proposed at a dose of 12.5–25 g/day per 1,000 kcal of formula, especially for surgical patients.18
A similar consensus report18 points to the fact that obesity can affect patient outcomes, including increasing the incidence of comorbidities and decreasing tolerance to prescribed nutrition regimens, and that immune-modulating formulas or supplements may be beneficial. However, the report cautions that more research is needed. The authors propose the following agents for consideration when designing an enteral formula: magnesium, L-arginine, zinc, leucine, fish oil, whey, betaine, S-adenosylmethionine, L-carnitine, and a –lipoic acid. The authors also recommend providing a high-protein, hypocaloric diet to preserve muscle, reduce fat mass, and improve insulin sensitivity.
Immune-modulating Nutrients
Early postoperative EN with an immune-enhancing formula is supported by research.1 A 2010 meta-analysis showed enteral formulas that include arginine and fish oil can reduce wound complications and acquired infections in malnourished or otherwise high-risk patients undergoing elective surgeries, including cardiac surgery.19 The authors indicate that perioperative and postoperative feeding with this type of immune-modulating diet can be beneficial. They further conclude that because postoperative feeding often is delayed, administering this type of diet preoperatively may be helpful and ideally should be started 5 to 7 days before surgery. They also report that the benefits of this type of dietary treatment may not be observed for 3 to 7 days.
Most of the studies in this and other research on the effects of immunonutrition have used the enteral product Impact® (Nestle HealthCare Nutrition, Florham Park, NJ).20 This product also contains antioxidants and nucleotides; therefore, the results seen in these studies cannot be attributed to any single added nutrient, nor can a synergistic effect be ruled out. Additional research in this area is needed.
Omega-3 fatty acids. Omega-3 fatty acids in fish oil are incorporated into cell membranes and help reduce tissue inflammation and the general inflammatory response with subsequent immunosuppression that normally occurs after surgery.19 Although omega-3 fats can provide the body with energy and help intestinal absorption of fat-soluble vitamins, they are unique in their ability to modulate the immune response. The byproducts of omega-3 metabolism result in the production of prostaglandins and leukotrienes, which are significantly less inflammatory than the byproducts of omega-6 metabolism and seem to promote wound healing. Omega-6 fatty acids previously have been shown to promote inflammation in critically ill patients.21
Menhaden oil is the most concentrated source of the most effective two omega-3 fats, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). DHA/EPA may be administered enterally or parenterally, although IV solutions of these lipids are not readily available in the US.22 It should be noted that although canola and flaxseed oil provide omega-3 fatty acids, these particular fats have not been shown to be effective in modulating immunity.
A rule of thumb is that omega-3 fats must be administered enterally for at least 3 to 5 days before a clinical benefit can be seen. Some evidence suggests that hospital length-of-stay may be decreased by giving DHA/EPA before surgery. A typical dose is 1.5–3 g/day, but research to identify an optimal dose for clinical settings is ongoing. Some international guidelines suggest 0.1–0.6 g/kg/day DHA/EPA as a general requirement.
Amino acids. Arginine is a substrate for protein synthesis, collagen deposition, and cell growth.1 Arginine supplementation increases nitric oxide production, enhances immune function, and increases tensile strength in acute wounds. Arginine is thought to promote wound healing by restoring depressed humoral and cell-mediated immunity, including boosting macrophage function and lymphocytic response and regulating cell proliferation.19 Both oral and enteral formulas containing arginine have helped improve wound healing.1 However, surgical patients with sepsis, as well as otherwise critically ill patients, appear to metabolize arginine differently than persons without these problems, and it is questionable whether arginine administration may actually be harmful in persons with sepsis.1,5 Optimal dosing for arginine has yet to be determined.
Glutamine functions as an energy source for cell proliferation within wounds.23 It also aids in stimulating the inflammatory response during wound healing.1 Glutamine supplementation may improve nitrogen balance and strengthen immunity following surgery.1 Given parenterally to patients undergoing elective surgeries, glutamine appears to reduce postoperative infections.5 Research on glutamine’s effects on wound healing or optimal dosing is limited.1 A supplemental dose of 0.57 g/kg/day has been suggested.
Conclusion
Practice implications for dietetic practitioners from the Academy of Nutrition and Dietetics24 stipulate that the lack of available evidence related to nutrition for wounds other than pressure ulcers require that dietitians use their best judgment and available resources when making decisions related to nutrition and wound care. Clinicians can take their cues from this and recognize that in some areas we need to rely on clinical judgment. Collaboration with other multidisciplinary team members also is recommended.
ERAS protocols include this type of multidisciplinary effort. As with any patient deemed high risk, it is important for a registered dietitian to promptly perform a thorough nutrition assessment and tailor an individualized plan of care, preferably before the surgical procedure, so perioperative nutrition can be maximized. Ideally, early nutrition intervention can prevent or minimize many of the complications, including delayed would healing or infection, that might otherwise occur in surgical patients. A number of individual nutrients may support improved wound healing and immune modulation. Although many of these nutrition therapies are insufficiently supported by available research for specific guidelines to have been published, it is hoped that future research will clarify many questions that remain regarding the use of specific nutrients to modulate the immune system.
Nancy Kondracki is an independent contractor in Greensboro, NC. She teaches weight loss classes to state employees, writes a monthly health and safety e-newsletter, and appears frequently in local television interviews. Nancy works in the Greensboro community to improve access to healthy food and opportunities for physical activity. This article was not subject to the Ostomy Wound Management peer-review process.
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