Nutritional Support and the Surgical Patient
Nutritional Support and the Surgical Patient
Purpose: Data on the impact of nutritional support (NS) on outcomes in surgical patients are reviewed.
Summary: While most patients will progress to oral nutrition after surgery and require little or no intervention, major surgery or postoperative complications can delay the prescription of an oral diet. In such patients, nutritional requirements are often increased to support wound healing and hypermetabolism associated with surgical recovery. Without adequate nutrition, muscle wasting, immune dysfunction, and declining visceral protein status are observed. While it would seem intuitive that early nutritional intervention is warranted for most patients, the literature to date suggests that early parenteral nutrition (PN) does not improve clinical outcomes. An exception may be for severely malnourished patients if NS is provided for at least seven days preoperatively. Such patients should be identified early through nutritional assessment. Early enteral nutrition (EN) may potentially improve patient outcomes compared with PN, but there are insufficient data to confirm this. High-dose parenteral glutamine may reduce infectious complications and the length of hospitalization for surgical patients, but a significant reduction in mortality has not been observed. Early EN with immune-enhancing formulas appears promising for general surgery patients. However, their use in the critically ill surgical patient is not unanimously supported, and some studies suggest potential harm.
Conclusion: Surprisingly little evidence is available to support a significant impact of early NS on postoperative clinical outcomes.
Patients undergoing surgery face many metabolic and physiological challenges that may compromise nutritional status. Postoperative nausea, vomiting, pain, and anorexia may tax those undergoing even minor surgeries, whereas catabolism, infection, and wound healing may be additional hurdles for patients after major operations. These issues are of far greater concern for patients entering the operating room with nutritional deficits. Patients with preoperative undernutrition have a significantly higher risk of postoperative complications and death than those well nourished prior to surgery. Poor nutritional status can compromise the function of many organ systems, including the heart, lungs, kidneys, and gastrointestinal (GI) tract. Immune function and muscle strength are also impaired, leaving these patients more vulnerable to infectious complications and the need for postsurgical reintubation. Wound healing is delayed, as is progress in patient mobility, thus prolonging the patient's surgical recovery. All these factors may contribute to a longer hospital stay, higher readmission rates, and markedly increased health care costs. As described by Meguid and Laviano, every surgeon intuitively knows that operating on a malnourished patient can become a rueful and costly experience.
Even well-nourished patients can experience adverse outcomes if postoperative nutrition is significantly delayed. The lack of nutrition for 10-14 days, especially during periods of increased metabolic demand with postoperative recovery, can result in higher complication and mortality rates than in those receiving nutritional support (NS). Consistent with this, guidelines provided by the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) recommend that NS be initiated for patients unable to take adequate oral nutrition for 7-14 days. Other medical organizations have made similar recommendations.
Considering the complications associated with perioperative malnutrition, it may seem surprising that NS does not always improve clinical outcomes. The inherent risks associated with artificial NS may outweigh the benefits in certain patient populations. Therefore, it is important to (1) identify early which patients maybenefit from parenteral nutrition (PN) or enteral nutrition (EN) intervention, (2) provide the optimal combination of nutrients, and (3) closely monitor patient progress throughout the course of therapy. This process supports the optimal use of resources and, more important, can reduce risks of adverse clinical outcomes.
The purpose of this review is to summarize the available data regarding
Controversies regarding micronutrient requirements or specialty products for specific organ dysfunction are not included in this review.
A computerized search was performed using the MEDLINE and International Pharmaceutical Abstracts databases. Search terms included combinations of the following: "surg-," "parenteral nutrition," "enteral nutrition," "nutrition support," "calories," "hypocaloric," "protein," "nitrogen," "immunonutrition," "glutamine," "arginine," "omega-3 fatty acids," "fish oils," "nucleotides," and "immune." Reference lists of pertinent articles and personal files were also searched. When available, meta-analyses were chosen over randomized controlled trials (RCTs) and prospective RCTs over retrospective studies to summarize available data. Risk ratios (RRs) and confidence intervals (CIs) are reported whenever found in relevant articles. Because surgical intervention can result in critical illness, meta-analyses and trials combining data on surgical and critically ill patients are included with subgroup analyses defining differences in outcomes between these groups.
Abstract
Purpose: Data on the impact of nutritional support (NS) on outcomes in surgical patients are reviewed.
Summary: While most patients will progress to oral nutrition after surgery and require little or no intervention, major surgery or postoperative complications can delay the prescription of an oral diet. In such patients, nutritional requirements are often increased to support wound healing and hypermetabolism associated with surgical recovery. Without adequate nutrition, muscle wasting, immune dysfunction, and declining visceral protein status are observed. While it would seem intuitive that early nutritional intervention is warranted for most patients, the literature to date suggests that early parenteral nutrition (PN) does not improve clinical outcomes. An exception may be for severely malnourished patients if NS is provided for at least seven days preoperatively. Such patients should be identified early through nutritional assessment. Early enteral nutrition (EN) may potentially improve patient outcomes compared with PN, but there are insufficient data to confirm this. High-dose parenteral glutamine may reduce infectious complications and the length of hospitalization for surgical patients, but a significant reduction in mortality has not been observed. Early EN with immune-enhancing formulas appears promising for general surgery patients. However, their use in the critically ill surgical patient is not unanimously supported, and some studies suggest potential harm.
Conclusion: Surprisingly little evidence is available to support a significant impact of early NS on postoperative clinical outcomes.
Introduction
Patients undergoing surgery face many metabolic and physiological challenges that may compromise nutritional status. Postoperative nausea, vomiting, pain, and anorexia may tax those undergoing even minor surgeries, whereas catabolism, infection, and wound healing may be additional hurdles for patients after major operations. These issues are of far greater concern for patients entering the operating room with nutritional deficits. Patients with preoperative undernutrition have a significantly higher risk of postoperative complications and death than those well nourished prior to surgery. Poor nutritional status can compromise the function of many organ systems, including the heart, lungs, kidneys, and gastrointestinal (GI) tract. Immune function and muscle strength are also impaired, leaving these patients more vulnerable to infectious complications and the need for postsurgical reintubation. Wound healing is delayed, as is progress in patient mobility, thus prolonging the patient's surgical recovery. All these factors may contribute to a longer hospital stay, higher readmission rates, and markedly increased health care costs. As described by Meguid and Laviano, every surgeon intuitively knows that operating on a malnourished patient can become a rueful and costly experience.
Even well-nourished patients can experience adverse outcomes if postoperative nutrition is significantly delayed. The lack of nutrition for 10-14 days, especially during periods of increased metabolic demand with postoperative recovery, can result in higher complication and mortality rates than in those receiving nutritional support (NS). Consistent with this, guidelines provided by the American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.) recommend that NS be initiated for patients unable to take adequate oral nutrition for 7-14 days. Other medical organizations have made similar recommendations.
Considering the complications associated with perioperative malnutrition, it may seem surprising that NS does not always improve clinical outcomes. The inherent risks associated with artificial NS may outweigh the benefits in certain patient populations. Therefore, it is important to (1) identify early which patients maybenefit from parenteral nutrition (PN) or enteral nutrition (EN) intervention, (2) provide the optimal combination of nutrients, and (3) closely monitor patient progress throughout the course of therapy. This process supports the optimal use of resources and, more important, can reduce risks of adverse clinical outcomes.
The purpose of this review is to summarize the available data regarding
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Controversies regarding micronutrient requirements or specialty products for specific organ dysfunction are not included in this review.
A computerized search was performed using the MEDLINE and International Pharmaceutical Abstracts databases. Search terms included combinations of the following: "surg-," "parenteral nutrition," "enteral nutrition," "nutrition support," "calories," "hypocaloric," "protein," "nitrogen," "immunonutrition," "glutamine," "arginine," "omega-3 fatty acids," "fish oils," "nucleotides," and "immune." Reference lists of pertinent articles and personal files were also searched. When available, meta-analyses were chosen over randomized controlled trials (RCTs) and prospective RCTs over retrospective studies to summarize available data. Risk ratios (RRs) and confidence intervals (CIs) are reported whenever found in relevant articles. Because surgical intervention can result in critical illness, meta-analyses and trials combining data on surgical and critically ill patients are included with subgroup analyses defining differences in outcomes between these groups.
