Improvement of nutritional measures during preoperative parenteral nutrition in patients selected by the prognostic nutritional index: a randomized controlled trial

Preoperative nutrition therapy in people undergoing gastrointestinal surgery

BACKGROUND

Poor preoperative nutritional status has been consistently linked to an increase in postoperative complications and worse surgical outcomes. We updated a review first published in 2012.

OBJECTIVES

To assess the effects of preoperative nutritional therapy compared to usual care in people undergoing gastrointestinal surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, Embase, three other databases and two trial registries on 28 March 2023. We searched reference lists of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of people undergoing gastrointestinal surgery and receiving preoperative nutritional therapy, including parenteral nutrition, enteral nutrition or oral nutrition supplements, compared to usual care. We only included nutritional therapy that contained macronutrients (protein, carbohydrate and fat) and micronutrients, and excluded studies that evaluated single nutrients. We included studies regardless of the nutritional status of participants, that is, well-nourished participants, participants at risk of malnutrition, or mixed populations. We excluded studies in people undergoing pancreatic and liver surgery. Our primary outcomes were non-infectious complications, infectious complications and length of hospital stay. Our secondary outcomes were nutritional aspects, quality of life, change in macronutrient intake, biochemical parameters, 30-day perioperative mortality and adverse effects.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodology. We assessed risk of bias using the RoB 1 tool and applied the GRADE criteria to assess the certainty of evidence.

MAIN RESULTS

We included 16 RCTs reporting 19 comparisons (2164 participants). Seven studies were new for this update. Participants' ages ranged from 21 to 79 years, and 62% were men. Three RCTs used parenteral nutrition, two used enteral nutrition, eight used immune-enhancing nutrition and six used standard oral nutrition supplements. All studies included mixed groups of well-nourished and malnourished participants; they used different methods to identify malnutrition and reported this in different ways. Not all the included studies were conducted within an Enhanced Recovery After Surgery (ERAS) programme, which is now current clinical practice in most hospitals undertaking GI surgery. We were concerned about risk of bias in all the studies and 14 studies were at high risk of bias due to lack of blinding. We are uncertain if parenteral nutrition has any effect on the number of participants who had a non-infectious complication (risk ratio (RR) 0.61, 95% confidence interval (CI) 0.36 to 1.02; 3 RCTs, 260 participants; very low-certainty evidence); infectious complication (RR 0.98, 95% CI 0.53 to 1.80; 3 RCTs, 260 participants; very low-certainty evidence) or length of hospital stay (mean difference (MD) 5.49 days, 95% CI 0.02 to 10.96; 2 RCTs, 135 participants; very low-certainty evidence). None of the enteral nutrition studies reported non-infectious complications as an outcome. The evidence is very uncertain about the effect of enteral nutrition on the number of participants with infectious complications after surgery (RR 0.90, 95% CI 0.59 to 1.38; 2 RCTs, 126 participants; very low-certainty evidence) or length of hospital stay (MD 5.10 days, 95% CI -1.03 to 11.23; 2 RCTs, 126 participants; very low-certainty evidence). Immune-enhancing nutrition compared to controls may result in little to no effect on the number of participants experiencing a non-infectious complication (RR 0.79, 95% CI 0.62 to 1.00; 8 RCTs, 1020 participants; low-certainty evidence), infectious complications (RR 0.74, 95% CI 0.53 to 1.04; 7 RCTs, 925 participants; low-certainty evidence) or length of hospital stay (MD -1.22 days, 95% CI -2.80 to 0.35; 6 RCTs, 688 participants; low-certainty evidence). Standard oral nutrition supplements may result in little to no effect on number of participants with a non-infectious complication (RR 0.90, 95% CI 0.67 to 1.20; 5 RCTs, 473 participants; low-certainty evidence) or the length of hospital stay (MD -0.65 days, 95% CI -2.33 to 1.03; 3 RCTs, 299 participants; low-certainty evidence). The evidence is very uncertain about the effect of oral nutrition supplements on the number of participants with an infectious complication (RR 0.88, 95% CI 0.60 to 1.27; 5 RCTs, 473 participants; very low-certainty evidence). Sensitivity analysis based on malnourished and weight-losing participants found oral nutrition supplements may result in a slight reduction in infections (RR 0.58, 95% CI 0.40 to 0.85; 2 RCTs, 184 participants). Studies reported some secondary outcomes, but not consistently. Complications associated with central venous catheters occurred in RCTs involving parenteral nutrition. Adverse events in the enteral nutrition, immune-enhancing nutrition and standard oral nutrition supplements RCTs included nausea, vomiting, diarrhoea and abdominal pain.

AUTHORS' CONCLUSIONS

We were unable to determine if parenteral nutrition, enteral nutrition, immune-enhancing nutrition or standard oral nutrition supplements have any effect on the clinical outcomes due to very low-certainty evidence. There is some evidence that standard oral nutrition supplements may have no effect on complications. Sensitivity analysis showed standard oral nutrition supplements probably reduced infections in weight-losing or malnourished participants. Further high-quality multicentre research considering the ERAS programme is required and further research in low- and middle-income countries is needed.

Assessing the nutritional status of hospitalized elderly

Purpose

The increasing number of elderly people worldwide throughout the years is concerning due to the health problems often faced by this population. This review aims to summarize the nutritional status among hospitalized elderly and the role of the nutritional assessment tools in this issue.

Methods

A literature search was performed on six databases using the terms “malnutrition”, “hospitalised elderly”, “nutritional assessment”, “Mini Nutritional Assessment (MNA)”, “Geriatric Nutrition Risk Index (GNRI)”, and “Subjective Global Assessment (SGA)”.

Results

According to the previous studies, the prevalence of malnutrition among hospitalized elderly shows an increasing trend not only locally but also across the world. Under-recognition of malnutrition causes the number of malnourished hospitalized elderly to remain high throughout the years. Thus, the development of nutritional screening and assessment tools has been widely studied, and these tools are readily available nowadays. SGA, MNA, and GNRI are the nutritional assessment tools developed specifically for the elderly and are well validated in most countries. However, to date, there is no single tool that can be considered as the universal gold standard for the diagnosis of nutritional status in hospitalized patients.

Conclusion

It is important to identify which nutritional assessment tool is suitable to be used in this group to ensure that a structured assessment and documentation of nutritional status can be established. An early and accurate identification of the appropriate treatment of malnutrition can be done as soon as possible, and thus, the malnutrition rate among this group can be minimized in the future.

Nutrition support in hospitalised adults at nutritional risk

BACKGROUND

The prevalence of disease-related malnutrition in Western European hospitals is estimated to be about 30%. There is no consensus whether poor nutritional status causes poorer clinical outcome or if it is merely associated with it. The intention with all forms of nutrition support is to increase uptake of essential nutrients and improve clinical outcome. Previous reviews have shown conflicting results with regard to the effects of nutrition support.

OBJECTIVES

To assess the benefits and harms of nutrition support versus no intervention, treatment as usual, or placebo in hospitalised adults at nutritional risk.

SEARCH METHODS

We searched Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, MEDLINE (Ovid SP), Embase (Ovid SP), LILACS (BIREME), and Science Citation Index Expanded (Web of Science). We also searched the World Health Organization International Clinical Trials Registry Platform (www.who.int/ictrp); ClinicalTrials.gov; Turning Research Into Practice (TRIP); Google Scholar; and BIOSIS, as well as relevant bibliographies of review articles and personal files. All searches are current to February 2016.

SELECTION CRITERIA

We include randomised clinical trials, irrespective of publication type, publication date, and language, comparing nutrition support versus control in hospitalised adults at nutritional risk. We exclude trials assessing non-standard nutrition support.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane and the Cochrane Hepato-Biliary Group. We used trial domains to assess the risks of systematic error (bias). We conducted Trial Sequential Analyses to control for the risks of random errors. We considered a P value of 0.025 or less as statistically significant. We used GRADE methodology. Our primary outcomes were all-cause mortality, serious adverse events, and health-related quality of life.

MAIN RESULTS

We included 244 randomised clinical trials with 28,619 participants that met our inclusion criteria. We considered all trials to be at high risk of bias. Two trials accounted for one-third of all included participants. The included participants were heterogenous with regard to disease (20 different medical specialties). The experimental interventions were parenteral nutrition (86 trials); enteral nutrition (tube-feeding) (80 trials); oral nutrition support (55 trials); mixed experimental intervention (12 trials); general nutrition support (9 trials); and fortified food (2 trials). The control interventions were treatment as usual (122 trials); no intervention (107 trials); and placebo (15 trials). In 204/244 trials, the intervention lasted three days or more.We found no evidence of a difference between nutrition support and control for short-term mortality (end of intervention). The absolute risk was 8.3% across the control groups compared with 7.8% (7.1% to 8.5%) in the intervention groups, based on the risk ratio (RR) of 0.94 (95% confidence interval (CI) 0.86 to 1.03, P = 0.16, 21,758 participants, 114 trials, low quality of evidence). We found no evidence of a difference between nutrition support and control for long-term mortality (maximum follow-up). The absolute risk was 13.2% in the control group compared with 12.2% (11.6% to 13%) following nutritional interventions based on a RR of 0.93 (95% CI 0.88 to 0.99, P = 0.03, 23,170 participants, 127 trials, low quality of evidence). Trial Sequential Analysis showed we only had enough information to assess a risk ratio reduction of approximately 10% or more. A risk ratio reduction of 10% or more could be rejected.We found no evidence of a difference between nutrition support and control for short-term serious adverse events. The absolute risk was 9.9% in the control groups versus 9.2% (8.5% to 10%), with nutrition based on the RR of 0.93 (95% CI 0.86 to 1.01, P = 0.07, 22,087 participants, 123 trials, low quality of evidence). At long-term follow-up, the reduction in the risk of serious adverse events was 1.5%, from 15.2% in control groups to 13.8% (12.9% to 14.7%) following nutritional support (RR 0.91, 95% CI 0.85 to 0.97, P = 0.004, 23,413 participants, 137 trials, low quality of evidence). However, the Trial Sequential Analysis showed we only had enough information to assess a risk ratio reduction of approximately 10% or more. A risk ratio reduction of 10% or more could be rejected.Trial Sequential Analysis of enteral nutrition alone showed that enteral nutrition might reduce serious adverse events at maximum follow-up in people with different diseases. We could find no beneficial effect of oral nutrition support or parenteral nutrition support on all-cause mortality and serious adverse events in any subgroup.Only 16 trials assessed health-related quality of life. We performed a meta-analysis of two trials reporting EuroQoL utility score at long-term follow-up and found very low quality of evidence for effects of nutritional support on quality of life (mean difference (MD) -0.01, 95% CI -0.03 to 0.01; 3961 participants, two trials). Trial Sequential Analyses showed that we did not have enough information to confirm or reject clinically relevant intervention effects on quality of life.Nutrition support may increase weight at short-term follow-up (MD 1.32 kg, 95% CI 0.65 to 2.00, 5445 participants, 68 trials, very low quality of evidence).

AUTHORS' CONCLUSIONS

There is low-quality evidence for the effects of nutrition support on mortality and serious adverse events. Based on the results of our review, it does not appear to lead to a risk ratio reduction of approximately 10% or more in either all-cause mortality or serious adverse events at short-term and long-term follow-up.There is very low-quality evidence for an increase in weight with nutrition support at the end of treatment in hospitalised adults determined to be at nutritional risk. The effects of nutrition support on all remaining outcomes are unclear.Despite the clinically heterogenous population and the high risk of bias of all included trials, our analyses showed limited signs of statistical heterogeneity. Further trials may be warranted, assessing enteral nutrition (tube-feeding) for different patient groups. Future trials ought to be conducted with low risks of systematic errors and low risks of random errors, and they also ought to assess health-related quality of life.

Percentage of Weight Loss as a Predictor of Surgical Risk: From the Time of Hiram Studley to Today

Hiram Studley's 1936 article of research was the first publication to present a connection between preoperative weight loss and adverse postoperative outcome. Almost 70 years later, weight loss remains one of the most prominently used tools to assess nutritional status and predict surgical risk. This paper provides an overview of surgical practices at the time of Dr Studley and demonstrates Studley's unique contributions to the field of nutrition support. The search for more accurate methods of preoperative nutrition assessment is traced to show how subsequent research continues to validate the use of weight loss in the assessment of surgical risk. New developments center on techniques of body composition assessment to quantify weight lost as functional weight and clarify the impact of malnutrition on operative outcome.

Pre-operative nutrition support in patients undergoing gastrointestinal surgery

BACKGROUND

Post-operative management in gastrointestinal (GI) surgery is becoming well established with 'Enhanced Recovery After Surgery' protocols starting 24 hours prior to surgery with carbohydrate loading and early oral or enteral feeding given to patients the first day following surgery. However, whether or not nutritional intervention should be initiated earlier in the preoperative period remains unclear. Poor pre-operative nutritional status has been linked consistently to an increase in post-operative complications and poorer surgical outcome.

OBJECTIVES

To review the literature on preoperative nutritional support in patients undergoing gastrointestinal surgery (GI).

SEARCH METHODS

The searches were initially run in March 2011 and subsequently updated in February 2012. Databases including all EBM Reviews (Cochrane DSR, ACP Journal Club, DARE, CCTR, CMR, HTA and NHSEED) MEDLINE, EMBASE, AMED, British Nursing Index Archive using OvidSP were included and a search was run on each database separately after which duplicates were excluded.

SELECTION CRITERIA

The inclusion criteria were randomised controlled trials that evaluated pre-operative nutritional support in GI surgical participants using a nutritional formula delivered by a parenteral, enteral or oral route. The primary outcomes included post-operative complications and length of hospital stay.

DATA COLLECTION AND ANALYSIS

Two observers screened the abstracts for inclusion in the review and performed data extraction. Bias was assessed for each of the included studies using the bias assessment tables in the Cochrane Software Review Manager (version 5.1, Cochrane Collaboration). The trials were analysed using risk ratios with Mantel-Haenszel in fixed effects methods displayed with heterogeneity. Meta-analyses were undertaken on trials evaluating immune enhancing (IE) nutrition, standard oral supplements, enteral and parenteral nutrition (PN) which were administered pre-operatively.Study characteristics were summarised in tables. Dichotomous and ratio data were entered into meta-analyses for the primary outcomes. These were then summarised in tables with assumed and corresponding risk with relative effect giving 95% confidence intervals.

MAIN RESULTS

The searches identified 9900 titles and, after excluding duplicates, 6433 titles were initially screened. After the initial title screen, 6266 were excluded. Abstracts were screened for 167 studies and 33 articles were identified as meeting the inclusion criteria, of which 13 were included in the review after an assessment of the complete manuscripts.Seven trials evaluating IE nutrition were included in the review, of which 6 were combined in a meta-analysis. These studies showed a low to moderate level of heterogeneity and significantly reduced total post-operative complications (risk ratio (RR) 0.67 CI 0.53 to 0.84). Three trials evaluating PN were included in a meta-analysis and a significant reduction in post-operative complications was demonstrated (RR 0.64 95% CI 0.46 to 0.87) with low heterogeneity, in predominantly malnourished participants. Two trials evaluating enteral nutrition (RR 0.79, 95% CI 0.56 to 1.10) and 3 trials evaluating standard oral supplements (RR 1.01 95% CI 0.56 to 1.10) were included, neither of which showed any difference in the primary outcomes.

AUTHORS' CONCLUSIONS

There have been significant benefits demonstrated with pre-operative administration of IE nutrition in some high quality trials. However, bias was identified which may limit the generalizability of these results to all GI surgical candidates and the data needs to be placed in context with other recent innovations in surgical management (eg-ERAS). Some unwanted effects have also been reported with components of IE nutrition in critical care patients and it is unknown whether there would be detrimental effects by administering IE nutrition to patients who could require critical care support after their surgery. The studies evaluating PN demonstrated that the provision of PN to predominantly malnourished surgical candidates reduced post-operative complications; however, these data may not be applicable to current clinical practice, not least because they have involved a high degree of 'hyperalimentation'. Trials evaluating enteral or oral nutrition were inconclusive and further studies are required to select GI surgical patients for these nutritional interventions.

Nutrition support in clinical practice: review of published data and recommendations for future research directions

In the last 30 years, marked advances in enteral feeding techniques, venous access, and enteral and parenteral nutrient formulations have made it possible to provide nutrition support to almost all patients. Despite the abundant medical literature and widespread use of nutritional therapy, many areas of nutrition support remain controversial. Therefore, the leadership at the National Institutes of Health, The American Society for Parenteral and Enteral Nutrition, and The American Society for Clinical Nutrition convened an advisory committee to perform a critical review of the current medical literature evaluating the clinical use of nutrition support; the goal was to assess our current body of knowledge and to identify the issues that deserve further investigation. The panel was divided into five groups to evaluate the following areas: nutrition assessment, nutrition support in patients with gastrointestinal diseases, nutrition support in wasting diseases, nutrition support in critically ill patients, and perioperative nutrition support. The findings from each group are summarized in this report. This document is not meant to establish practice guidelines for nutrition support. The use of nutritional therapy requires a careful integration of data from pertinent clinical trials, clinical expertise in the illness or injury being treated, clinical expertise in nutritional therapy, and input from the patient and his/her family.

Nutrition in the perioperative patient

The association of malnutrition with surgical morbidity and mortality is well recognized. The question of whether this relationship is causal or simply an association in sick patients has been hotly debated. The field of nutrition support has grown out of the belief that correcting malnutrition will modify associated risks for poor outcome. It has been easier to substantiate this belief in some clinical situations than in others. The evidence for nutrition support during the perioperative period is reviewed and recommendations are made about where nutrition support is most useful and where it may be counterproductive. Some of the important unanswered questions about perioperative nutrition support are raised.

AGA technical review on parenteral nutrition

This literature review and the recommendations therein were prepared for the American Gastroenterological Association Clinical Practice and Practice Economics Committee. The paper was approved by the Committee on September 13, 2001, and by the AGA Governing Board on May 18, 2001.

Parenteral nutrition in the critically-ill patient: more harm than good?

While many studies have reported that providing parenteral nutrition (PN) can change nutritional outcomes, there are limited data that demonstrate that PN influences clinically-important end points in critically-ill patients. The purpose of the present paper is to systematically review and critically appraise the literature to examine the relationship between PN and morbidity and mortality in the critically-ill patient. Studies comparing enteral nutrition (EN) with PN and studies comparing PN with no PN were reviewed. The results suggest that EN is associated with reduced infectious complications in some critically-ill subgroups. PN, on the other hand, is associated with increased morbidity and mortality in critically-ill patients. When nutritional support is indicated, EN should be used preferentially over PN. Further studies are needed to define the optimal timing and composition of PN in patients not tolerating sufficient EN. Strategies to optimize EN delivery and minimize PN utilization in critically-ill patients are indicated.

Nutritional support in the critically ill patients. A critical review of the evidence

Providing nutritional support has become a standard component of managing critically ill patients. While many studies have documented that providing nutritional support can change nutritional outcomes (e.g., amino acid profile, weight gain, nitrogen balance), data are lacking that demonstrate that nutrition actually influences clinically importance endpoints. This article systematically reviews and critically appraises the literature, examining the relationship between nutritional support and infectious morbidity and mortality in the critically ill patient. In addition, evidence-based recommendations are made.

Clinical efficacy of perioperative nutrition support

Despite a large number of published randomized prospective controlled clinical trials the indications for perioperative parenteral and enteral nutrition support remain controversial. This article reviews the reports of several recently published consensus conference reports and prospective randomized controlled trials evaluating nutritional therapy in surgical patients.

Nutrition support in clinical practice: review of published data and recommendations for future research directions. National Institutes of Health, American Society for Parenteral and Enteral Nutrition, and American Society for Clinical Nutrition

In the last 30 years, marked advances in enteral feeding techniques, venous access, and enteral and parenteral nutrient formulations have made it possible to provide nutrition support to almost all patients. Despite the abundant medical literature and widespread use of nutritional therapy, many areas of nutrition support remain controversial. Therefore, the leadership at the National Institutes of Health, The American Society for Parenteral and Enteral Nutrition, and The American Society for Clinical Nutrition convened an advisory committee to perform a critical review of the current medical literature evaluating the clinical use of nutrition support; the goal was to assess our current body of knowledge and to identify the issues that deserve further investigation. The panel was divided into five groups to evaluate the following areas: nutrition assessment, nutrition support in patients with gastrointestinal diseases, nutrition support in wasting diseases, nutrition support in critically ill patients, and perioperative nutrition support. The findings from each group are summarized in this report. This document is not meant to establish practice guidelines for nutrition support. The use of nutritional therapy requires a careful integration of data from pertinent clinical trials, clinical expertise in the illness or injury being treated, clinical expertise in nutritional therapy, and input from the patient and his/her family.

Nutrition assessment in the 1990s: where are we now?

This review addresses some of the challenges confronting the modern nutrition support clinician in developing protocols for nutrition assessment. While it is generally agreed upon that patients who are malnourished are at greater risk for development of complications during hospitalization, there is no consensus on the best method for assessment of nutritional status. Assessment parameters currently available include clinical, biochemical, anthropometric, and functional tests designed to evaluate nutrition status as well as estimate body composition. As some of these parameters are expensive or not practical for routine clinical use, they should be evaluated carefully when a nutrition assessment protocol is designed.

A prospective analysis of factors influencing outcome after fundoplication

Fundoplication remains a common operation in the brain-damaged pediatric patient, but recent reports suggest a poor outcome in these patients. The factors that might be associated with complications or recurrence after fundoplication have not been extensively examined. Fifty-six brain-damaged children, aged 6 months to 12 years, with documented gastroesophageal (GE) reflux underwent preoperative nutritional evaluations (percentage of ideal weight, albumin, nutrition risk index [NRI]) and documentation of medications (dexamethasone for bronchopulmonary dysplasia) before standard Nissen fundoplication. Hospital stay, intensive care unit (ICU) stay, and time on ventilator, as well as major postoperative complications (wound infection/dehiscence, pneumonia) were prospectively analyzed. Survival and recurrence rates 1 to 3 years postoperatively were also assessed. Eighty-two percent of patients were < 90% ideal weight, and 50% had NRI < 90 (normal = 100) and 29% had albumin < 3.5 g/dL. Albumin < 3.5 was significantly (P < .01) associated with prolonged hospitalization (26.8 + 2.2 versus 15.1 + 1.1 days) and ICU stay (13.8 + 1.0 versus 4.4 + .5 days) and time on ventilator (8.0 + 1.0 versus 1.8 + .4 days). NRI < 90 showed similar significant differences (P < .01). Ideal body weight < 90% was not significant. Major complications developed in 54% of patients; only two or more preoperative nutritional deficiencies, or a nutritional deficiency plus dexamethasone were significantly associated (P < .01). Recurrence occurred in 21% of patients and was significantly correlated with preoperative dexamethasone alone (P < .01), and especially when dexamethasone plus a nutritional deficit were present (low albumin, P < .001; low NRI, P < .005).(ABSTRACT TRUNCATED AT 250 WORDS)

[Respective indications of enteral or parenteral nutrition during pre- and post-operative periods]

Denutrition is often associated with poor postoperative outcome. However, a large body of evidence, from studies comparing perioperative parenteral (PN) or enteral (EN) nutrition to the absence of perioperative nutrition, suggests that perioperative nutritional support provides significant improvements in both nutritional status and postoperative clinical outcome in selected patients who are or will become malnourished. The aim of this study was to select and review all relevant articles comparing perioperative parenteral and enteral nutritional support, either in terms of clinical outcome, or risks and costs, or in pathophysiological terms. Twelve clinical reports were reviewed. All contained methodological flaws, mainly type II statistical error due to an insufficient number of patients, inaccurate primary diagnosis, absence of blinding, and lack of objective criteria of judgement. These concerns warrant caution in interpreting the results. Moderately strong (grade B) recommendations can only be drawn from these studies: PN (compared to early EN) is associated with a higher rate of sepsis in patients following abdominal trauma; EN is as efficient as PN in patients following surgery; EN is safe and cheaper than PN. PN formulae lack many important nutrients (glutamine, arginine, cysteine, peptides, fibers, n-3 polyunsaturated fatty acids, and nucleotides). Many experimental (animal) and some clinical (in non surgical patients) studies showed that PN (compared to EN) induces gut mucosal atrophy, liver dysfunction, gut bacterial translocation and immune dysfunction. The final aim of PN and EN would therefore strikingly differ. The qualitatively imperfect PN would only supply the fasting patient with quantitative amounts of calories and proteins. Due to initially limited digestive tolerance, EN provides less nutrition than PN does, but would finally lead to the same or even better outcome, due to its ability to counteract stress induced gut and immune dysfunction. Current evidence therefore suggests that early EN is superior to PN in trauma patients, and not different from but cheaper (and therefore more cost-effective) than PN in surgical patients. Further controlled, randomised, and blinded studies including sufficient sizes of groups are required, especially in the surgical setting, to address a large number of still unanswered questions.

[In which patients has the efficacy of preoperative artificial nutrition be proved?]

Today a consensus on the value of peroperative nutritional support is not existing, despite a recognized correlation between the stage of denutrition and the postoperative mortality and morbidity rates. This review of 11 prospective randomized studies, comparing undernourished patients with a major malignant or non-malignant surgical illness, according to the use or not of preoperative nutritional support, showed a wide discrepancy between the techniques of denutrition assessment, the underlying surgical disease, the tumor extension, the extend of surgery, the level and duration of nutritional support between the studies. However, among them, those without major bias show that a preoperative nutritional support of at least seven days, decreases significantly the rate of postoperative complications, especially the infection, in the most undernourished patients.

Nutrition support in patients with cancer: what do the data really show?

Although more than 70 prospective randomized controlled trials have evaluated the use of nutrition support in patients with cancer, the indications for nutrition therapy in this patient population remain controversial. We reviewed the published prospective randomized controlled trials that evaluated clinically important endpoints (morbidity, mortality, and duration of hospitalization). Many trials had serious shortcomings in study design that limit the ability to draw definitive conclusions from the data. In general, the data failed to demonstrate the clinical efficacy of providing nutrition support to most patients with cancer. Therefore, the indications for using nutrition therapy should be the same as those for patients with benign disease.

Strategies and needs for nutritional support in cancer surgery

Nutritional therapy in tumor patients undergoing surgery should be regarded as a supportive therapy. They render the operation tolerable or even feasible, and they have a positive effect on postoperative progress and wound healing. Malnourished patients definitely profit from nutritional therapy. However, the effectiveness of a nutritional regimen should not be overestimated: postoperative progress, wound healing, and complication rate depend not only on nutritional status but also on the nature of the operation, age, and preoperative treatment. As a rule, parenteral feeding is superior to enteral feeding directly after surgery. Enteral nutritive regimens are to be favored when long-term feeding is indicated: in this case the advantages of this type of feeding prevail.

What rate of infusion of intravenous nutrition solution is required to stimulate uptake of amino acids by peripheral tissues in depleted patients?

We examined the effect of varying the quantities (0, 0.1, 0.2, 0.3, and 0.4 gN.kg-1.[day]-1) of nitrogen input on N balance, 3-methylhistidine (3MH) excretion, plasma amino acid concentration and the net flux of amino acids across the leg in depleted patients requiring parenteral nutrition. The calorie-to-nitrogen ratio was 140 to 1 (kcal:1 gN) and consequently the patients received varying amounts of calories (8, 14, 28, 42, and 56 kcal.kg-1.[day]-10. There was negative nitrogen balance and net loss of amino acids from the limb during fasting. An infusion of 0.2 gN.kg-1.[day]-1 of IVN reversed the net catabolic process and resulted in equilibrium of peripheral total amino acid flux and of tyrosine flux without a decrease in 3MH excretion. Net uptake of total amino acids and tyrosine in peripheral tissues was achieved with 0.4 gN.kg-1.[day]-1 and 56 kcal.kg-1.[day]-1. This was associated with a fivefold increase in 3MH excretion (p less than 0.01), indicating that net anabolism occurred with increased protein turnover. Fifty per cent of the amino acids taken up by peripheral tissues during infusions of 0.4 gN.kg-1.[day]-1 was due to the uptake of glutamate (Glu) and 20% was due to the uptake of branched chain amino acids (BCAA). Plasma Glu concentration, [Glu], did not increase with increasing IVN infusion, but BCAA concentrations did. Although the mean plasma [Glu] did not change with IVN infusion, there was an independent effect of plasma [Glu] (p less than 0.0001) and of N input (p less than 0.0001) on Glu flux, indicating that even at high infusion rates the maximal capacity of peripheral tissues to take up Glu had not been reached.