Provision of nutritional support to those experiencing complications following bariatric surgery

This review details the practicalities of providing nutrition support to obese patients who experience complications following bariatric surgery and highlights some of the nutritional challenges encountered by this group of patients. Bariatric surgery to treat morbid obesity has significantly increased internationally over the past decade with hospital admissions rising annually. The gastric bypass is currently the most commonly performed procedure. The complication rate can be up to 16%, with a considerable proportion having nutritional implications. The treatment can involve avoidance of oral diet and nutrition support, i.e. enteral or parenteral nutrition. Opposition to nutrition support can be encountered. It is useful to clarify the aims of nutrition support, these being: the avoidance of overfeeding and its consequences, preservation of lean body mass and promotion of healing. Evidence suggests that hypoenergic nutrition is not harmful and may actually be beneficial. There is a lack of consensus regarding the optimum method to predict the nutritional requirements in the obese acutely unwell patient. The literature suggests that the predicted equations are fairly accurate compared to measured energy expenditure in free living obese patients before and after bariatric surgery. However, these findings cannot be directly applied to those obese patients experiencing complications of bariatric surgery, who will be acutely unwell exhibiting inflammatory response. It is therefore necessary to refer to the literature on energy expenditure in hospitalized obese patients, to help guide practice. More research examining the energy and protein requirements of obese patients needing nutrition support following bariatric surgery is urgently required.

Morbid obesity and nutrition support: is bigger different?

Morbid obesity (body mass index >40 kg/m2 or >35 kg/m2 in the presence of an severe-obesity-related comorbid disease) is increasing in frequency in the United States and worldwide. This population has a variety of medical and surgical disorders that result in hospitalizations. It is not unexpected to encounter these patients on the nutrition support service. The obesity comorbid diseases that may increase complications related to nutrition support are present in greater frequency and severity in the morbidly obese population than in the nonobese population. To reduce these potential complications, strategies of hypocaloric nutrition have been advocated for obese patients, and this study focuses specifically on the morbidly obese subset.

Can measured resting energy expenditure be estimated by formulae in daily clinical nutrition practice?

PURPOSE OF REVIEW

To recognize the fundamental factors that alter energy expenditure on a daily basis and the impact they have on the measurement of caloric consumption by the human body, through respiratory indirect calorimetry, and thus to try to determine which predictive equation best correlates with total energy expenditure generated from energy measurements.

RECENT FINDINGS

The most important compartment of the body, for its metabolic activity and influence upon resting metabolic rate, is fat-free mass. Other variables affecting energy expenditure are sex, weight, height, age, body surface area, fat mass and ethnicity. Metabolic and activity factors such as the thermic effect of nutrients, facultative thermogenesis, anabolism/growth and physical activity, also contribute, comprising total daily energy expenditure. Following the pioneering work of Harris and Benedict for the estimation of energy expenditure, several authors turned their experimental interest to this area, and various recent predictive formulae were derived. These are useful and easy to apply in daily clinical nutrition practice. However, because of the cited variables upon energy expenditure, the final daily caloric estimates show inherent errors ranging from -23.5 to +22.5% upon measured caloric expenditure. These are particularly remarkable in critically ill patients who are exposed to medical and surgical interventions.

SUMMARY

One has to be careful in choosing, understanding and clinically applying the results from predictive equations, bearing in mind that the original population from which the equation was derived does not always correspond to that currently being evaluated.

Caloric requirements in patients with necrotizing fasciitis

Patients with necrotizing fasciitis (NF) and other soft tissue infections are often treated in burn centers due to the extent of wound care and surgical intervention needed. Sepsis and surgery increase metabolic needs and may limit oral intake and necessitate enteral (TEN) or parenteral (TPN) nutrition. We reviewed the records of patients admitted with necrotizing fasciitis or surgical soft tissue infections from January 1993 to June 1998 who had indirect calorimetry (IC) measurements performed. Records were also reviewed for surgical/medical management and nutritional intervention. Twenty-six patients were admitted with 17 of these having IC measurements (133 total IC measurements). The IC group had more surgeries (mean 4.9 versus 2.7) and 82% required mechanical ventilation (mean 17.9 days). Energy expenditure showed a moderate but significant increase in energy needs (mean 23.8 kcal/kg/day, 124% BEE) with large variations (10.7-42.4 kcal/kg/day, 60%-199% BEE) in individual energy requirements. Caloric intake averaged 73% of needs based on IC (range 53%-104%). Nearly all patients (94%) required TEN (82%) and/or TPN (41%) nutrition for a mean of 24 days (range 1-68 days). NF presents a broad range of metabolic and surgical needs. Our data indicates patients with NF have increased energy requirements and suggests provision of calories at 124% basal or 25 kcal/kg actual wt/d; but due to the large individual variation, routine assessment using IC is recommended. Clinicians need to recognize the likely need for nutritional support and possibly lengthy clinical course for these patients.

Hypocaloric feeding of obese patients in the intensive care unit

PURPOSE OF REVIEW

Given the increased awareness of the detrimental complications of overfeeding, particularly hyperglycemia, the safety and efficacy of specialized nutritional support for the critically ill obese patient is of major concern. The intent of this review is to provide the scientific foundation, supporting and conflicting literature, for the implementation of hypocaloric, high-protein specialized nutritional support for acutely ill, hospitalized patients with obesity.

RECENT FINDINGS

Similar anabolic equivalencies can be achieved with hypocaloric, high-protein nutritional support compared with a more traditional higher calorie, lower protein regimen. The provision of additional calories worsens hyperglycemia, results in a further accumulation of fat mass, and increases the potential for overfeeding without significant net protein anabolism gain.

SUMMARY

The current literature indicates that hypocaloric, high-protein enteral or parenteral nutrition is promising as the standard of practice for the metabolic support of the critically ill obese patient. The achievement of net protein anabolism and the avoidance of overfeeding complications are the primary goals, with fat weight loss a welcome secondary benefit.

Enteral nutrition and enteral tube feeding. Review of the evidence

Improvements in delivery systems for enteral feeding, in formulas, and in the understanding of complications have made the technology for enteral feeding easy to apply. Adequate nutrients can be delivered, and individual tolerance for feeding is acceptable. The remaining question is when to apply the technology. Formula selection should be as simple as possible. Aspiration and other early complications are a serious risk and are not diminished by route of feeding. Long-term enteral feeding is associated with a high complication rate, with high mortality, and may not be effective.

Predictive versus measured energy expenditure using limits-of-agreement analysis in hospitalized, obese patients

BACKGROUND

Accuracy of predictive formulae is crucial for therapeutic planning because indirect calorimetry measurement is not always possible or cost effective. Energy requirements are more difficult to predict in the acutely ill obese patient compared with lean patients because of an increased resting energy expenditure per lean body mass and a variable stress response to illness.

METHODS

A retrospective review of 726 patients identified 57 patients (32 spontaneous breathing, S; 25 ventilator dependent, V) with body mass indexes of 30-50 kg/m2. Limits-of-agreement analysis determined bias (the mean difference between measured and predicted values) and precision (the standard deviation of the bias) to evaluate the accuracy of predictive formulae compared with measured resting energy expenditure (MREE) by a Deltatrac Metabolic Monitor. Predictive accuracy was determined within+/-10% MREE. The predictive formulae examined were: variations of the Harris-Benedict equations using ideal, adjusted weights of 25% and 50% and actual weights with stress factors ranging from 1.0 to 1.5; the Ireton-Jones equation for obesity; the Ireton-Jones equations for hospitalized patients (S and V); and the ratio of 21 kcalories per kilogram actual weight.

RESULTS

The mean MREE was 21 kcal/kg actual weight. The adjusted Harris-Benedict average weight equation was optimal for predicting MREE for the combined S and V sets (bias = 182+/-123; 67%+/-10% MREE), as well as the S subset (bias = 159+/-112; 69%+/-10% MREE).

CONCLUSIONS

The Harris-Benedict equations using the average of actual and ideal weight and a stress factor of 1.3 most accurately predicted MREE in acutely ill, obese patients with BMIs of 30-50 kg/m2. Predictive formulae were least accurate for obese, ventilator-dependent patients.

The role of nutrition in prevention and healing of pressure ulcers

Among the many risk factors for pressure ulcers, malnutrition is potentially reversible. This article examines the relationship of malnutrition to the prevention and healing of pressure ulcers. Evidence for nutrition in preventing and healing pressure ulcers is presented. Specific nutrients, including some amino acids, vitamins, and minerals, have been evaluated for their effects on wound healing.