Acknowledgment
We gratefully acknowledge Maureen E. Rombeau, MA, for editorial assistance.
Introduction
Surgeons are justifiably proud of their seminal contributions to nutritional care of the hospitalized patient. These contributions include quantifying the prevalence of malnutrition, confirming the association of malnutrition with adverse clinical outcomes, discovering parenteral nutrition (PN), and demonstrating, in selected groups of patients, that providing nutritional support (NS) may either prevent or correct malnutrition-associated morbidity. Despite the lack of confirmatory data in many surgical populations, surgeons must still decide when, what, and how to feed their patients while recognizing that the alternative is starvation.
In this chapter we review the assessment of nutritional status, indications for NS, dietary components and their delivery, and new directions in NS, with particular emphasis on colon and rectal surgery (CRS). For purposes of discussion, NS is defined arbitrarily as the provision of oral supplements, enteral feeding, or parenteral nutrients. Every attempt has been made to provide evidence-based recommendations. A complete discussion of this topic is beyond the scope of this short review. For more extensive information, the reader is referred to the Web site of the American Society for Parenteral and Enteral Nutrition (ASPEN) at http://www.nutritioncare.org/ .
Nutritional Assessment
The decision to provide NS is based, in part, on measurement of criteria predictive of a malnutrition-induced adverse outcome. It should be emphasized that these measures are not totally determined by the patient’s nutritional status; they are also influenced by the primary diagnosis, degree of metabolic stress, and presence of infection. Extensive information is available on nutritional assessment for perioperative NS, ranging from sophisticated multivariate indices (which are more feasible with dedicated teams performing these functions) to more readily performed clinical history and measurement of serum proteins. Important assessment criteria to initiate NS are shown in Box 83-1 .
Strong Indications
ONE of the following:
- •
Nonvolitional loss of ≥10% usual body weight within 2-3 mo prior to hospitalization
- •
Serum albumin <3.0 g/dL in euvolemic state
Moderate Indications
TWO of the following:
- •
Current oral intake meeting <50% of total energy needs
- •
Starvation >7 days
- •
Anticipation of nutritional support >7 days
- •
Serum prealbumin <150 mg/dL in euvolemic state
It should be noted that these criteria are guidelines and not absolute recommendations for NS. Clinical judgment remains the most important determinant in deciding when, what, and how to feed patients.
Indications for Nutritional Support
General Indications
General indications for perioperative NS for the patient undergoing CRS include severe malnutrition as determined clinically by weight loss and reduced serum proteins. Significant loss of body weight is perhaps the most important single indication for NS. Nonvolitional loss of more than 10% of usual weight within 3 months prior to surgery and/or a serum albumin level less than 3 g/dL in the euvolemic state are important criteria to initiate some type of perioperative NS ( Box 83-1 ).
Severe Malnutrition
The indications for NS, particularly for parenteral feeding, have become more limited during the past 40 years because of the lack of confirmatory data in the most common groups of minimally and moderately malnourished patients.
Severe malnutrition in perioperative patients is associated with adverse postoperative outcomes, including increased infection, poor wound healing, anastomotic breakdown, coagulopathy, and heart failure. Delaying an elective colorectal operation to improve the patient’s nutritional status may therefore be beneficial, but only if the patient is severely malnourished. The decision to use NS preoperatively must be made with an appreciation of the rising costs of health care, issues with third-party payor reimbursement, and administrative pressures to decrease hospital stay. In a recent Cochrane Review of preoperative nutrition in patients undergoing digestive tract surgery, it was concluded that immune-enhancing nutrition and PN had significant outcome benefits; however, trials evaluating standard enteral or oral supplemental nutrition were inconclusive.
One of the goals of preoperative nutrition in this patient population is to minimize loss of nitrogen from skeletal muscle by decreasing the duration of fasting and supporting muscle mass and immune function. Despite these metabolic goals, data only support aggressive NS for the most severely malnourished surgical patients because neither preoperative PN nor enteral nutrition (EN) provides a clear benefit in either the borderline or mildly malnourished patient. Moreover, multiple studies that failed to show a clear benefit, and that occasionally showed a detriment in these patients, led ASPEN to conclude that perioperative NS in patients with cancer should be limited to persons with severe malnutrition who are likely to be unable to eat for more than 7 to 10 days after surgery, as shown in Box 83-1 . PN should be given to patients who will not be able to meet their nutritional requirements by oral or enteral tube feeds within the same period.
Postoperative Nutrition
With the exception of the severely malnourished preoperative patient, most NS is provided postoperatively. The traditional postoperative management of keeping patients “nil by mouth” (NPO) until clinical signs of return of bowel function are present is no longer justified. To our knowledge, there is no significant outcome benefit with starting a clear liquid diet versus a regular or low-residue diet. However, initiating a regular diet offers numerous nutritional advantages, including increased caloric intake, decreased protein catabolism and weight loss, improved patient satisfaction, and decreased length of hospital stay. Moreover, level 1 evidence supports early postoperative feeding in patients undergoing elective colon and rectal surgery. Initiation of enteral feeds within 2 days of surgery shortens postoperative ileus and enhances return to oral intake. Thus, it behooves the colorectal surgeon to anticipate these issues and plan appropriately; for example, intraoperative placement of feeding tubes may be warranted to allow for early EN in the malnourished patient with colorectal cancer. PN should be reserved for patients who cannot meet their nutrient needs by 7 days after surgery. Fast-track or enhanced recovery programs begin oral intake within 24 hours of surgery (see the Early Postoperative Feeding: “Fast Track” section). Early administration of an oral diet diminishes the duration of a postoperative ileus, decreases postoperative complication rates, and lowers mortality. No significant increase in anastomotic leaks or dehiscence occurs, and early feeding results in a trend toward lower infection rates and decreased length of hospital stays. The major complication related to the early initiation of a diet is an increased risk of vomiting and bloating.
Specific CRS Indications
Inflammatory Bowel Disease
Almost all patients with Crohn disease and approximately one third of those with ulcerative colitis will require surgery. Some degree of malnutrition is common among most perioperative patients with inflammatory bowel disease (IBD) because of insufficient dietary intake, malabsorption, chronic inflammation, and adverse effects of medications. The extent of malnutrition depends on the chronicity of the disease, its severity, and the degree of involvement of the small intestine.
Preoperative malnutrition, as defined by unintended weight loss, or decreased serum proteins such as albumin and prealbumin, is associated with increased postoperative morbidity in persons with IBD. In fact, a preoperative serum albumin level less than 3.5 g/dL was associated with an increased risk of anastomotic leak after colon resection. Thus aggressive preoperative and postoperative NS has been recommended for selected surgical patients with IBD.
Insufficient data exist to support either a specific perioperative feeding regimen or generalized goals of nutritional care for patients with IBD.
Some patients with Crohn disease have undergone multiple resections of both the small and large intestine, leading to short bowel syndrome. Nutritional management of these patients is particularly challenging. This topic is described elsewhere in this book ( Chapter 72 ).
Colorectal Cancer
As in the cohort with IBD, preoperative malnutrition is present in some patients with colorectal cancer. Cancer stage, type, location and size, and prior neoadjuvant treatment with chemotherapy and/or radiation all contribute to decreased nutrient intake. In addition, the presence of a wasting syndrome, or cancer cachexia, may lead to severe malnutrition of the patient with colorectal cancer. Malnutrition and severe weight loss negatively affect surgical outcomes of patients with cancer. In this context, evidence suggests that early feeding after surgery is not only safe but is associated with decreased postoperative morbidity and mortality.
Confirmatory data are lacking to support the use of specific dietary formulas or the precise timing for initiating NS. In a study of 963 patients undergoing surgery for colorectal cancer, Gustaffsson and colleagues found that closer adherence to an enhanced recovery protocol resulted in fewer than 25% postoperative complications and a shorter length of hospital stay when compared with a nonprotocol group. Their protocol included a high-calorie liquid intake up to 2 hours before surgery (sometimes prohibited by anesthesiologists in the United States; see the New Directions section) and oral feeding as early as 4 hours after surgery.
Estimation of Nutrient Requirements
Perioperative nutrient needs have been measured in major clinical settings ranging from elective surgery to the severely stressed, critically ill patient. Knowledge of caloric and protein requirements is particularly relevant to the patient undergoing CRS. Consultation with a clinical dietician is frequently helpful to determine nutrient requirements, particularly in settings in which the surgeon is less experienced with these calculations.
Calories
Glucose is the preferred energy source, particularly for NS. When provided in sufficient amounts, glucose reduces protein breakdown and nitrogen losses by suppressing hepatic gluconeogenesis and limiting the need for amino acids to be oxidized for energy.
Lipid is another important exogenous source of energy. It also spares nitrogen and is often given as a supplement to PN-based carbohydrate in conditions of difficult regulation of serum glucose levels. With the recognition that nutrition is a requisite component of complete perioperative care, most patients initially should be prescribed 25 kcal/kg of actual body weight to be increased gradually to 30 to 35 kcal/kg if weight gain is desired.
Protein
Protein is a mandatory component of NS. It is composed of approximately one-sixth nitrogen. Grams of protein can be converted to grams of nitrogen by dividing by 6.25. This is often confusing to surgeons, inasmuch as protein loss is usually expressed as grams of nitrogen and protein intake is generally calculated as grams of protein per kilogram of body weight. Based on extensive metabolic studies in surgical patients, we prescribe approximately 1.5 g of protein/kg actual body weight/day. Nitrogen losses are monitored every few days through nitrogen balance by measuring 24-hour urinary urea nitrogen with an addition of 4 g as an estimate of fecal and integumentary losses. Positive nitrogen balance correlates with an anabolic state, whereas a negative balance suggests catabolism.
Estimates of total caloric and protein needs are also based, in part, on the patient’s body mass index (body weight kg/height cm), listed in Table 83-1 . The caloric ratio of protein:fat:glucose should approximate 20%:30%:50%. Lipids are delivered separately with PN and are limited to 20% to 30% of the nonprotein calories as a result of their tendency for oxidation and free radical formation.
| BMI <30 | BMI 30-40 | BMI >40 | |
|---|---|---|---|
| Calories | 25-30 kcal/kg ABW | 22-25 kcal/kg IBW | 22-25 kcal/kg IBW |
| Protein | 1.2-2.0 kg ABW | >2.0 g/kg IBW | >2.5 g/kg IBW |
Dietary Composition and Delivery
Options for feeding surgical patients include standard hospital-based oral diets, oral supplements, enteral liquid formula diets, and parenteral nutrition.
Hospital-Based Diets
The composition and array of hospital-based diets has changed little in the past 40 years. Diets relevant to patients undergoing colorectal surgery include clear liquid, regular, and low residue.
Clear Liquid Diet
Clear liquid diets contain water, broth, clear juices, Popsicles, and gelatin. They are relatively distasteful and provide minimal nutritional benefit. In some patients, these diets help stimulate swallowing in the early postoperative state. Similar to other types of oral intake, these diets should not be prescribed if the patient is abnormally distended because of the potentiation of gastric distension with swallowed air.
Regular Diet
Regular diets are used to provide nutrition for patients without special needs. They are well tolerated by most postoperative patients who have some return of appetite and the absence of contraindications to oral/enteral feeding ( Box 83-2 ). Patient preference for early initiation of standard diets, when compared with clear liquid diets, has been reported after elective colorectal surgery. As the result of the wide variety of food intolerances and preferences among patients of differing ethnic, religious, and socioeconomic groups, the ingestion of approximately one third of the standard hospital diet is generally sufficient for hospital discharge. Appetite and food intake usually increase significantly when the patient is discharged to his or her usual environment.
Severe abdominal distension, vomiting
Intolerance to enteral nutrition
High-output gastrointestinal fistula(s)
Hemodynamic instability/vasopressors
Intestinal ischemia
Severe sepsis
Low-Residue Diet
Low-residue diets are formulated similarly to a low-fiber diet but typically limit components that increase bowel activity, such as milk products. They contain less than 7 to 10 g of dietary fiber per day.
Oral Supplements
Oral supplements are similar in formulation to, although more palatable than, enteral tube feeds. Oral supplements provide a high caloric density of 1.0 to 2.0 kcal/mL. They are prescribed for patients with decreased intake of food. Prescription of oral supplements has improved quality of life, nutritional status, and intake and has decreased infection rates in postoperative patients.
Liquid Formula Diets
Liquid formula diets used for EN differ in osmolarity, caloric density, electrolytes, vitamins, and fiber contents. In general, formulas are categorized as standard, concentrated, predigested, and immune modulating ( Table 83-2 ). Standard formulas are relatively inexpensive and meet the basic nutritional needs of most postoperative CRS and critically ill patients. Concentrated EN formulations are hyperosmolar with high caloric densities and may be advantageous in patients who require volume restriction. Predigested formulas are valuable in certain malabsorptive situations such as short bowel syndrome and in patients with chyle leaks. Immune-modulating formulas are supplemented with arginine, glutamine, nucleic acid, omega-3 fatty acids, and antioxidants and are more costly than standard formulations. Some studies support use of immune-modulating formulas in surgical patients in the intensive care unit. Although no significant reduction in mortality occurs, decreased length of hospital stay and fewer infections occur in certain patient populations. Recent evidence supports increasing use of these diets (see the Immunonutrition section).
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