Perioperative nutritional support: immunologic defects

Nutrition and Wound Healing

The relationship between nutrition and wound healing--after injury or surgical intervention--has been recognized for centuries. There is no doubt that adequate carbohydrate, fat, and protein intake is required for healing to take place, but research in the laboratory has suggested that other specific nutritional interventions can have significant beneficial effects on wound healing. Successful translation into the clinical arena, however, has been rare. A review of normal metabolism as it relates to wound healing in normoglycemic and diabetic individuals is presented. This is followed by an assessment of the current literature and the data that support and refute the use of specialized nutritional support in postoperative and wounded patients. The experimental evidence for the use of arginine, glutamine, vitamins, and micronutrient supplementation is described. Most of the experimental evidence in the field supporting the use of specialized nutritional support has not been borne out by clinical investigation. A summary of the clinical implications of the data is presented, with the acknowledgment that each patient's plan of care must be individualized to optimize the relationship between nutrition and wound healing.

Nutrition and wound healing

The relationship between host nutrition and wound healing has been the subject of study and experimentation for centuries. Despite the many years of study and a substantial knowledge base of the specific processes and factors involved, wound healing remains enigmatic. There is still much to learn about the wound-specific nutritional interventions that are available to improve wound healing. Nutrition profoundly influences the process of wound healing. Nutritional depletion exerts an inhibitory effect, and nutritional supplementation with such positive effectors as arginine can stimulate wound healing. Within this paradigm, the physician should be able to recognize patients who may be expected to have wound healing difficulties and offer early intervention to avoid wound failure.

Micronutrients in women's health and immune function

Lawrence J. Machlin's contributions to elucidating the roles of nutrients in optimizing human health included the support of research in the areas of women's health and immune function. Several essential nutrients have been shown to affect women's health throughout the different life stages. Symptoms of premenstrual syndrome affect the vast majority of menstruating women, and calcium supplementation significantly reduces physical and emotional symptoms. Premenstrual syndrome in fact might be a predictor of osteoporosis induced by low calcium intake. Periconceptional multivitamin supplementation has reduced the risk of serious birth defects, premature delivery, and low birth weight by 50% and improved maternal health during pregnancy. Micronutrients of particular importance for prevention of adverse pregnancy outcomes are folic acid, zinc, and iron. However, if the preterm delivery is caused by preeclampsia, then data suggest that calcium supplementation and high doses of vitamins C and E significantly reduce that risk. Well-controlled studies consistently have shown that calcium supplementation, with or without vitamin D, significantly reduces the risk of hip fracture. Antioxidants such as vitamins C and E have been shown to reduce the risk of fracture in women smokers. As in the rapidly growing embryo, the immune system includes rapidly multiplying cells whose functions are dramatically affected by an individual's micronutrient status. Multivitamins have been shown to enhance many aspects of immune response, and antioxidant micronutrients consistently have been found to enhance lymphocyte-proliferative responses and skin-test responses, especially in the elderly.

Protein-energy undernutrition in hospital in-patients

Impaired nutritional status has been frequently reported in surveys estimating its prevalence amongst patients in hospital. While there is no doubt that protein-energy undernutrition has serious implications for health, recovery from illness or surgery and hospital costs, lack of nationally or internationally accepted cut-off points and guidelines for most nutrition-related variables make nutritional assessment difficult and proper comparisons between studies impossible. In reviewing published work in which the prevalence of undernutrition has been assessed, it can be seen that each study defined undernutrition, or nutritional risk, using different methodology. This present review aims to highlight the problems which arise when deciphering these studies, and the resulting difficulty in determining the true prevalence of undernutrition and nutritional risk, amongst both general and specific groups of hospital in-patients. It is widely agreed that routine hospital practices can further adversely affect the nutritional status of sick patients in hospital. How this occurs, and the potential effects of impaired nutritional status on clinical outcome are examined. The methods currently available to assess nutritional status are evaluated in the knowledge that such assessments are difficult in clinical practice. The review concludes by proposing that if we want the medical and nursing professions to consider the nutritional status of hospital patients seriously, definitions of undernutrition and nutritional risk, and cut-off values for the nutritional variables measured must be agreed to allow evidence-based practice. Outcome measures which allow clear comparisons between groups and treatments must be used in studies assessing the effects of nutritional interventions.

Pre-operative nutritional assessment

Protein-energy undernutrition, or the possibility of its development, has been documented to occur frequently in surgical patients admitted to hospital. Nutritional status is known to deteriorate over the course of the hospital stay, with poor awareness by medical and nursing staff as to the deleterious effects of impaired nutritional status on clinical outcome and hospital costs. While there is no consensus on the best method for assessment of the nutritional status of surgical patients pre-operatively, there are a number of techniques available. These techniques can be divided into two types, those suitable for screening for nutrition risk on admission to hospital and those used to fully assess nutritional status. Both techniques have their limitations, but if used correctly, and their limitations recognized, should identify the appropriate degree of nutritional intervention for an individual patient in a timely and cost-effective manner. The techniques currently available for nutritional screening and nutritional assessment are reviewed, and their applicability to the Irish setting are discussed in the present paper.

Reversible impairment in monocyte major histocompatibility complex class II expression in malnourished surgical patients

BACKGROUND

Upregulation of major histocompatibility complex (MHC) class II antigen in response to the T-cell lymphokine interferon-gamma (IFN-gamma) is central to T cell-macrophage cooperation and immune homeostasis. We evaluated this property in malnourished surgical patients and assessed the impact of nutrition repletion with total parenteral nutrition (TPN).

METHODS

Sixty-two patients were studied: 37 malnourished and 25 controls. Whole blood was cultured with or without IFN-gamma (100 U mL-1), dual-labeled with anti-CD14 (monocyte) and anti-human leukocyte antigen-DR antibodies and analyzed by flow cytometry. Phagocytosis was measured by flow cytometry. In a second study, 10 severely malnourished patients received 5 days of TPN and MHC class II expression was measured at the end of this period.

RESULTS

The magnitude of the increase in monocyte MHC class II expression in response to IFN-gamma was significantly increased in the control group compared with the malnourished group (107% vs 53%; p < .05). This impairment directly correlated with severity of malnutrition, but did not correlate with age or disease type. The number of bacteria phagocytozed per cell was significantly decreased (p < .05) in the malnourished group. In study 2, there was a significant increase in MHC class II induction with IFN-gamma after short-term TPN (58% before vs 173% after, p < .001).

CONCLUSIONS

MHC class II induction in response to IFN-gamma is significantly impaired in malnourished patients, correlating with the severity of malnutrition. This defect is reversed by short-term TPN. These data identify the reversible loss of a key mechanism, fundamental to host defense, that may enhance the risk of infection in malnourished patients.

Nutrition and the immune system

Malnutrition frequently contributes to the immunocompromise seen in hospitalized patients. Nutritional support corrects malnutrition and can reverse the associated immunocompromise. Developing an understanding of nutritional needs and the role of nutrition in immune function is essential to prevention and treatment of nutrition-related immunocompromise. Current research is defining the role of specific nutrients in immune function. Recent evidence also suggests that the route (enteral versus parenteral) of providing nutritional support can affect immune competence. Intervention trials may show a role of key nutrients in not only maintaining normal immune competence, but also in modulating immunologic outcomes in critically ill patients.

Basic concepts of immunology and its application to clinical nutrition

In recent years, evidence has accumulated on the effects of nutrients on metabolic processes. The role of specific nutrients in modulating immune function has received much attention because of the significant role of the immune system in a variety of disease states. The immune system depends on the complex interactions of its various parts. In response to an "antigen" or foreign substance that penetrates the external protective barriers of the human body, nonspecific (phagocytes, complement) defense mechanisms and antigen-specific factors are activated. The antigen-specific immune system relies on both humoral (antibodies and B cells) and cellular (T cells and lymphokines) defenses. Malnutrition causes a decline in all aspects of host defense. Correction of malnutrition in hospitalized patients and restoration of immunocompetence has become a goal of nutrition support practitioners today. The application of current research findings to patient care requires a basic understanding of immunology.

Nutritional management of cats with infectious disease

The effect of malnutrition in patients with a variety of ailments is known to be deleterious to their overall quality of life, response and tolerance to therapy, and ultimate survival. These effects may be amplified in feline patients with infectious disease owing to the blunting of immunologic responsiveness that results from malnutrition. This vicious cycle of infection, ensuing malnutrition, and subsequent immunocompromise may not allow the patient to mount an attack on the invading pathogen adequately. The most logical means to reverse this cycle is to ensure an adequate nutritional state in the patient. Initial attempts at maintaining or increasing voluntary oral intake should be initiated in the short term. However, enteral or parenteral support should be instituted as quickly as possible if these should fail. Much is yet to be discerned about specific optimal supplementation techniques and dietary formulations for feline patients; however, the application of relatively simple and general principles of nutritional support offer our feline patients with infectious disease the best opportunity to overcome their disease.