What supports nutritional support?

Parenteral Nutrition

Parenteral nutrition (PN) is a therapy to nourish patients who cannot tolerate feeding via the gut. Though a life-saving intervention, it does have risks associated. In this article, we aim to dispel myths associated with PN. Practitioners who manage critically ill patients or patients with intestinal failure should be equipped with evidence-based knowledge of PN including the indications, contraindications, feasibility, complications, and long-term management of PN.

Selected pharmacokinetic issues of the use of antiepileptic drugs and parenteral nutrition in critically ill patients

OBJECTIVES

To conduct a systematic review for the evidence supporting or disproving the reality of parenteral nutrition- antiepileptic drugs interaction, especially with respect to the plasma protein-binding of the drug.

METHODS

The articles related to the topic were identified through Medline and PubMed search (1968-Feburary 2010) for English language on the interaction between parenteral nutrition and antiepileptic drugs; the search terms used were anti-epileptic drugs, parenteral nutrition, and/or interaction, and/or in vitro. The search looked for prospective randomized and nonrandomized controlled studies; prospective nonrandomized uncontrolled studies; retrospective studies; case reports; and in vitro studies. Full text of the articles were then traced from the Universiti Sains Malaysia (USM) library subscribed databases, including Wiley-Blackwell Library, Cochrane Library, EBSCOHost, OVID, ScienceDirect, SAGE Premier, Scopus, SpringerLINK, and Wiley InterScience. The articles from journals not listed by USM library were traced through inter library loan.

RESULTS

There were interactions between parenteral nutrition and drugs, including antiepileptics. Several guidelines were designed for the management of illnesses such as traumatic brain injuries or cancer patients, involving the use of parenteral nutrition and antiepileptics. Moreover, many studies demonstrated the in vitro and in vivo parenteral nutrition -drugs interactions, especially with antiepileptics.

CONCLUSIONS

There was no evidence supporting the existence of parenteral nutrition-antiepileptic drugs interaction. The issue has not been studied in formal researches, but several case reports and anecdotes demonstrate this drug-nutrition interaction. However, alteration in the drug-free fraction result from parenteral nutrition-drug (i.e. antiepileptics) interactions may necessitate scrupulous reassessment of drug dosages in patients receiving these therapies. This reassessment may be particularly imperative in certain clinical situations characterized by hypoalbuminemia (e.g., burn patients).

Ageing and infection

An increased morbidity and mortality due to infectious disease has been noted in the ageing. Two alternative explanations may account for this. Changes in the immune system and inflammatory responses with age or an increase in age-related diseases may underlie the increased susceptibility. A review of studies of healthy older individuals demonstrates changes in the immune system with ageing but minimal change in the inflammatory response. Investigations of severe infection in older nursing-home patients requiring hospitalization indicate that infection as a cause of admission and death is significantly more common in individuals who are bedridden because of serious cardiovascular or neurological disease and require urinary catheterization. The evidence indicates that underlying disease, not the senescence of host resistance, leads to severe infection in the ageing.

Perioperative nutrition: parenteral versus enteral

Malnutrition has been shown to have an adverse effect on the clinical outcome of surgical patients. During the past 25 years, investigators have sought to determine whether clinical outcome can be improved by the administration of pre- or postoperative (perioperative) nutritional support. We conclude that the clinical outcome of severely malnourished surgical patients is improved by perioperative nutritional support and that this should be administered whenever possible via the enteral route. The clinical outcome of less severely malnourished surgical patients, including those who are normally nourished, can be improved by the administration of oral dietary supplements at a time in the postoperative period when patients are ingesting free fluids. Some of these patients may also benefit from early postoperative enteral tube feeding, but further work is required to determine the effects following different types of surgery before this is adopted for routine use. Parenteral nutrition is only indicated in the postoperative period when major complications occur in association with intestinal failure.

Clinical economics review: nutritional support

Nutritional support currently accounts for about 1% of the total health care costs in the USA. Interestingly, most of the prospective randomized controlled trials to date have not been able to demonstrate that this therapeutic intervention alters morbidity or mortality. In fact, parenteral nutritional support may predispose the recipients to developing systemic infections. There have been a few areas in which nutritional support may be of benefit. Enteral supplements given to underweight women who suffer hip fractures reduce the hospital stay and, presumably, overall cost. Preoperative parenteral nutritional support may produce a small absolute reduction in post-operative morbidity, but its cost becomes prohibitive. Preoperative enteral nutritional support, especially if carried out in the home, may be of benefit (using the most optimistic interpretation of a small number of trials); if so, it is an economically defensible intervention. Particular nutrients or diets may have specific effects on certain disease processes. Indirect comparisons have suggested that elemental diets can be used to treat flares of Crohn's disease (perhaps because putative food antigens are removed). However, corticosteroid therapy is more efficacious. Furthermore, it is less expensive to employ 6-mercaptopurine as the next modality in steroid failures. Branched-chain amino acid infusions may have some effect on hepatic encephalopathy, but again, lactulose is less expensive. Nutritional support is one area of medicine in which there has been far more enthusiasm than the data justify. Disease-associated malnutrition probably is a secondary phenomenon, not an important cause of morbidity. The widespread use of this modality cannot be justified in a cost-constrained health care system.

Nutritional support teams: a review of comparative trials

OBJECTIVE

To evaluate the literature describing the influence of nutritional support teams (NSTs) on the provision of nutritional therapy.

DATA SOURCES

A MEDLINE and International Pharmaceutical Abstracts search (key terms: nutritional support, nutritional support service/team, hyperalimentation service/team, metabolic support service/team, service/team) covering 1970-1993 were used to identify pertinent literature.

STUDY SELECTION

The results of comparative trials involving NSTs are presented.

DATA EXTRACTION

Data from comparative trials examining the influence of NSTs on the provision of enteral nutrition (EN) and total parenteral nutrition are discussed.

DATA SYNTHESIS

NSTs dramatically reduced the incidence of catheter-related complications, especially sepsis, by developing central venous catheter insertion and care guidelines. Early studies found that NSTs reduced the incidence of electrolyte and metabolic abnormalities by more stringent laboratory and clinical monitoring, but this was not found consistently in later studies. The ability of consultative NSTs to reduce the incidence of metabolic and electrolyte abnormalities is less clear. NSTs also were more likely to evaluate, document, and subsequently meet a patient's nutritional requirements. Studies examining the financial impact of NSTs frequently reported cost savings, but often failed to include personnel costs in their analysis. The provision of EN by an NST reduced the frequency of complications and increased the adequacy of nutritional supplementation.

CONCLUSIONS

Early nutritional support teams produced significant benefits largely through the development of protocols and standardization. Current NSTs should increase the dissemination of information supporting their continued benefits. To remain viable, NSTs need to expand their roles, document improved patient outcomes, and show cost-effectiveness.

Favorable response to parenteral nutrition and medical therapy in Crohn's colitis. A report of 38 patients comparing severe Crohn's and ulcerative colitis

The courses of 38 patients with severe, uncomplicated acute colitis (16 with Crohn's colitis and 22 with ulcerative colitis) were analyzed retrospectively. The patients were placed on total parenteral nutrition and treated concomitantly with corticosteroids, antibiotics (often metronidazole), sulfasalazine, and/or azathioprine. Fifteen of the 16 Crohn's colitis patients were initially managed without surgery. Four patients subsequently relapsed, two responded to reinstituted medical therapy, and two underwent colon resection 2 and 4 years later. Of 22 ulcerative colitis patients, 16 required surgery during the initial hospitalization, one patient subsequently had surgery, and one died after refusing surgery. Three of the other four continue in remission on medical therapy. Thus, there were significant differences in this series between the clinical courses of severe ulcerative colitis and severe Crohn's colitis. While most of the ulcerative colitis patients with severe disease underwent colectomy, most of the patients with severe but uncomplicated Crohn's colitis responded to aggressive medical therapy, of which total parenteral nutrition and perhaps bowel rest seemed to be an important part. Afterwards, the majority remained in remission on long-term medical therapy.

Contamination of parenteral nutrition solutions not a hazard with additions made at ward level

Pre-mixed amino acid and dextrose solutions used for parenteral nutrition had additions made to them at a ward level by medical officers. Samples of the solutions of the study group and a control group were taken at six hours and at the end of the infusion time and were analysed microbiologically for growth of microorganisms. No organism was isolated from either group. We conclude that making additions to pre-mixed amino acid/dextrose solutions at the ward level does not constitute a microbiological hazard for the patient.

The in vitro and in vivo effects of human growth hormone administration on tumor growth of rats bearing a transplantable rat pituitary tumor (7315b)

The direct effects of human GH and IGF-I on PRL secretion and cell proliferation were studied on PRL secreting rat pituitary tumor 7315b cells in vitro, as well as the effects in vivo of human GH administration on body weight, IGF-I levels and tumor size in rats bearing this transplantable tumor. In the in vitro studies IGF-I levels above 5 nM stimulated PRL release in a dose-dependent manner while GH, in concentrations of 0.23-45 nM, did not affect PRL release. Cell proliferation was stimulated by IGF-I in a dose-dependent manner from 0.5 nM onwards, while GH did not have an effect. The in vivo studies showed that 1 mg GH/rat/day prevented tumor-induced cachexia and normalized the suppressed IGF-I levels without stimulating tumor growth. It is concluded that tumor-induced cachexia can be prevented by exogenous GH administration without an increase in tumor mass, even if a tumor model is used whose cultured tumor cells respond to exposure to IGF-I with a mitotic response.

Parenteral nutrition with branched-chain amino acids in hepatic encephalopathy. A meta-analysis

Meta-analytic methods were applied to review clinical trials published in English that have assessed the efficacy of parenteral nutrition for cirrhotic patients with acute hepatic encephalopathy. Modified amino acid solutions containing increased amounts of branched-chain amino acids were used as part of the treatment regimen in all studies. Pooled analysis of five randomized controlled studies showed a highly significant improvement in mental recovery (p less than 0.001) from high-grade encephalopathy over follow-up times varying from 5 to 14 days. The significance level of the treatment effect did not change when the analysis was repeated using alternative methods of counting and attributing events in these trials. Sharp differences in direction of treatment effect precluded pooling case fatality data. Two studies reported an increased risk of death in the treatment group. Two others showed a clear benefit from administration of parenteral nutrition: the aggregate relative risk reduction was 0.59 (95% confidence interval: 0.23-0.80, p = 0.002). Addition of unpublished data from a third positive study increased the relative risk reduction to 0.82 (p less than 0.0001), and the most conservative interpretation of the published data still yielded a significant reduction in mortality (p = 0.023). However, given the uncertainty about effects on mortality and short follow-up times in all studies, a confirmatory randomized controlled trial with longer follow-up periods is warranted.

Postoperative complications in colorectal surgery in relation to preoperative clinical and nutritional state and postoperative nutritional treatment

The impact of the pre-operative nutritional and clinical state on post-operative morbidity and mortality is not fully known and the effect of total parenteral nutrition (TPN) on the postoperative complication rate has not been established. We have investigated the effects of postoperative TPN on the complication rate in 92 patients after major colorectal surgery for carcinoma of the large bowel or inflammatory bowel disease in a controlled, randomised study. The complication rate was analysed against seven commonly used nutritional (biochemical and anthropometric) variables and against the diagnosis, clinical inflammatory activity and presence of pre-operative septic complication. Patients were randomly allocated to postoperative TPN or conventional fluid and electrolyte support. The results show no correlation between the complication rate and the nutritional and clinical state of the patients as assessed pre-operatively. The complication rate was not significantly reduced by postoperative TPN. This study indicates that biochemical and anthropometric nutritional variables do not identify patients at risk to develop postoperative complications. The presence of pre-operative complications showed a marginal correlation with postoperative morbidity, in agreement with previous experience. The result of this study obviates the use of TPN in routine postoperative care.

Effect of peptide chain length on absorption of egg protein hydrolysates in the normal human jejunum

The influence of the peptide chain length of partial enzymic hydrolysates of protein on nitrogen and amino acid absorption was studied in 12 subjects using a jejunal perfusion technique. Three hydrolysates of egg white and an equivalent amino acid mixture were perfused at 30 mmol/L and 100 mmol/L in two separate experiments. Two hydrolysates (OH1 and OH2) contained mainly dipeptides and tripeptides, whereas the third (OH3) comprised tripeptide to pentapeptides as judged chromatographically. Nitrogen absorption was significantly slower from the higher chain length mixture, OH3, than from the short chain mixtures, OH1 and OH2, at both concentrations. Similarly, several amino acid residues were absorbed less well from OH3 than from OH1 and OH2. These data demonstrate that the chain length of heterogeneous mixtures of peptides affects absorption of nitrogen and individual amino acid residues, and suggest that brush border hydrolysis of tetrapeptides and pentapeptides limits absorption from enzymic hydrolysates of protein which simulate the composition of the postprandial luminal contents.

Does treatment with essential amino acids and hypertonic glucose improve survival in acute renal failure?: A meta-analysis

We performed a meta-analysis of four randomized trials (RCTs) and one concurrent control study which addressed the following question: Does treatment with amino acid solutions and hypertonic glucose improve survival of seriously ill patients with acute renal failure who are unable to take oral or enteral feedings? Three RCTs compared outcomes with essential amino acid solutions (EAA) and hypertonic glucose against hypertonic glucose alone, and their results were pooled. Use of EAA was associated with an absolute increase in initial survival of 0.24 as compared to glucose (confidence interval: +.015 to +.446). Without weighting the data to reflect the quality of the RCTs, this effect was significant (p = .017). Patients needing dialysis showed a significant treatment effect (p = .015), while those not requiring dialysis did not (p = .11). However, survival to hospital discharge was not significantly improved for the patient population as a whole (p = .10). Using a standardized quality assessment protocol, the four RCTs received scores ranging from .188 to .357 out of a possible 1.00. Any statistically significant treatment effects were abolished by factoring the quality scores of the studies into the data-pooling process. Sensitivity analysis was performed to determine the effect of including the nonrandomized study. Although it had more patients than the other studies combined, the nonrandomized study was of low quality (score: .032) and its inclusion did not change the outcome of data pooling once quality weighting was applied. We conclude that the efficacy of these parenteral nutritional regimens remains uncertain in this clinical setting.

Future of enteral nutrition

Although there has been agreement that enteral nutrition remains an excellent means of providing nutritional support to malnourished patients with normal or near normal gastrointestinal function, it is clear that areas of controversy do exist, and attention needs to be directed towards these in the future.

Improved protein kinetics and albumin synthesis by branched chain amino acid-enriched total parenteral nutrition in cancer cachexia. A prospective randomized crossover trial

A prospective randomized crossover trial was conducted to determine the effect of a branched chain amino acid (BCAA)-enriched solution on whole body leucine kinetics and fractional rates of albumin synthesis in patients with intra-abdominal metastatic adenocarcinoma. Ten malnourished cancer patients were provided isonitrogenous amounts of both a conventional total parenteral nutrition (TPN) formula containing 19% BCAA and a BCAA-enriched TPN formula containing 50% of the amino acids as BCAA in a random order. Whole body protein turnover was determined by a 10 hour continuous infusion of leucine 14C. Increased whole body leucine flux (68 +/- 5 mumols/kg BW/hr versus 145 +/- 11; mean +/- SEM; P less than 0.001) and oxidation (13 +/- 2 mumols/kg BW/hr to 46 +/- 5; P less than 0.001) were determined on the BCAA-enriched TPN. Increased whole body protein synthesis (2.2 +/- 0.2 g protein/kg BW/day versus 3.9 +/- 0.3; P less than 0.005) and leucine balance (2.5 +/- 0.4 g leucine/d versus 6.5 +/- 0.6; P less than 0.001) were also observed in patients receiving the BCAA-enriched TPN solution. Leucine release from protein breakdown was not statistically elevated (1.65 +/- 0.18 g protein/kg BW/d versus 2.48 +/- 0.40; P greater than 0.05) but, incorporation of leucine 14C into plasma albumin was significantly elevated (2.37 +/- 0.23 mumols/g/hr to 4.21 +/- 0.33; P less than 0.001) when the patients received BCAA-enriched TPN. Despite the better leucine balance, the improvement in the 24-hour urinary nitrogen balance was not statistically significant (6.6 +/- 3.9 g protein/d versus 11.4 +/- 2.9; control versus BCAA-enriched; P = 0.15). BCAA-enriched formulas improve whole body leucine kinetics, fractional rates of albumin synthesis, and leucine balance, and thus may favorably influence protein metabolism in cancer cachexia.