The importance of a source of sufficient protein in postoperative hypocaloric partial parenteral nutrition support

Efficacy of hypocaloric parenteral nutrition for surgical patients: a systematic review and meta-analysis

BACKGROUND AND AIMS

Hypocaloric parenteral nutrition is an underfeeding strategy that lowers energy intake to around 20 kcal/kg/d. It is believed to achieve benefits by modulating metabolic responses and alleviating hyperglycemia. This study aims to systematically review the clinical efficacy of hypocaloric parenteral nutrition on surgical patients.

METHODS

Medline, SCI, Embase, Cochrane Library, Chinese Biomedicine Database (CBM) and China Knowledge Resource Integrated Database (CNKI) were searched for studies published before July 1, 2010. Randomized control trials (RCTs) that compared hypocaloric PN with standard or higher energy PN in surgical patients were identified and included. Methodological quality assessment was based on Cochrane Reviewers' Handbook and modified Jadad's Score Scale. Statistical software RevMan 5.0 was used for meta-analysis.

RESULTS

Five trials met all inclusion criteria and were included in the final meta-analysis. There were significant reductions in infectious complications (RR, 0.60; 95%CI 0.39-0.91, P = 0.02; I(2) = 38%) and length of hospitalization (LOS) associated with receiving hypocaloric PN (MD-2.49 days, 95%CI -3.88 to -1.11, P = 0.0004; I² = 48%). Stratified analysis of the smaller trials (<60) and larger trials demonstrated that the heterogeneity between trials was mainly associated with sample size. When smaller trials were excluded, hypocaloric PN was associated with reduction in infectious complications (RR, 0.21, 95%CI 0.06-0.72, P = 0.01, I2 = 0%) and shortening of LOS (MD, -2.32 days, 95%CI -3.72 to -0.93, P = 0.001, I² = 0%).

CONCLUSION

Hypocaloric parenteral nutrition may reduce infectious complications and the length of hospitalization in post-operative patients. However, this conclusion is tentative due to patient type and sample size. Furthermore, in terms of hypocaloric PN, the actual energy amount still varies a great deal (from 15 kcal/kg/d to 20 kcal/kg/d). This suggests that further research, including larger randomized clinical trials is required.

Randomized Controlled Study of Glycerol Versus Dextrose in Postoperative Hypocaloric Peripheral Parenteral Nutrition

The aim of this study was to use glycerol and dextrose in hypocaloric peripheral parenteral nutrition (HPNN) and investigate their effects on postoperative metabolic and nutritional responses. Thirty patients who had undergone major gastrointestinal surgery were examined in a prospective randomized study. The study period extended from the day before operation to postoperative day 7. Fifteen patients (intervention group) received 1.2 g amino acids, 1.2 g glycerol, and 0.5 g fat emulsion/kg/day (approximately 15 kcal/kg/day). The other 15 patients (control group) received 1.2 g amino acids, 1.5 g dextrose, and 0.5 g fat emulsion/kg/day (approximately 15 kcal/kg/day). After 7 days of study, both groups were found to have a decrease in body weight, mid-arm circumference, triceps skin fold, serum albumin, and transferrin and prealbumin levels, but an increase in serum cholesterol and triglyceride levels. However, the differences between them were not significant. Improvements in nitrogen balance were observed in the intervention group (p = .035). These data suggest that advantages favoring the administration of glycerol instead of dextrose in hypocaloric parenteral nutrition could hardly be found in our investigation, except that better nitrogen equilibrium is maintained. Nonetheless, the peripheral intravenously administered ProcalAmine with fat emulsion has been well tolerated and safe for these patients, as well as more convenient for clinical use.

Nutrition Society Symposium on ‘End points in clinical nutrition trials’ Death, morbidity and economics are the only end points for trials

In order to determine whether surrogate markers predict clinical outcome, randomized controlled trials (RCT) of nutrition supportv. no nutrition support that have reported at least one clinical outcome (mortality, infections, total complications, or duration of hospitalization) and at least one nutritional outcome (energy or protein intake, weight gain, N balance, albumin, prealbumin, transferrin, three anthropometric measures, skin testing, lymphocyte count) were assessed for concordance. If changes in nutritional markers predict clinical outcome, changes in both outcomes should go in the same direction. Concordance is defined as both outcomes changing in the same direction or both outcomes showing no difference. Discordance is defined as one outcome changing and the other not (partial) or both outcomes changing in opposite directions (complete). Ninety-nine RCT were identified, of which most were underpowered to see statistically significant changes, especially in clinical outcomes. Thus, the results were analysed only in relation to the direction of the respective changes in outcomes. Forty-eight comparisons (4×12) were made. The rates of concordance were ≤50% in forty-one of forty-eight comparisons; the rate was never >75%. A complete discordance rate of ≥25% was present in forty-three (≥50% in thirteen) of the forty-eight comparisons. The discordance was usually a result of the nutritional outcome being better than the clinical outcome. Changes in nutritional markers do not predict clinical outcomes. Before adopting any surrogate marker as an end point for a clinical trial, it has to be known that improving it will result in patient benefit.

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 support after bone marrow transplantation: comparison of total and partial parenteral nutrition during the early posttransplantation period

OBJECTIVE

Bone marrow transplantation (BMT) usually is indicated if the patient's malignant disease involves the marrow or if hazard to the normal marrow is the limiting factor in the aggressive treatment of disease. The success of BMT depends on a complete team with all the resources needed to ensure optimal results. Aggressive nutrition support after BMT is very important. Adequate parenteral nutrition, total (TPN) or partial, followed by enteral nutrition according to the patient's gastrointestinal function is the important principle.

METHODS

Between 1996 and 2000, 60 patients, 46 male and 14 female, received BMT in Chang Gung Memorial Hospital. Their ages ranged from 6 to 54 y. Standard TPN was used in 40 patients after BMT, and partial parenteral nutrition was used in the remaining 20 patients. TPN was enriched with branched-chain amino acids (BCAA) when the patient's liver functions were impaired, and cyclic TPN was shifted when the patient's liver functions persistently deteriorated.

RESULTS

Most patients improved their nutrition status and increased their body weights, especially those receiving TPN. The patients receiving partial parenteral nutrition decreased their visceral proteins significantly during the course of parenteral nutrition. The BCAA-TPN can maintain a patient's visceral protein better than standard TPN. Only two patients expired because of graft rejection and sepsis; their body weights and nutrition status showed deterioration despite aggressive nutrition support.

CONCLUSIONS

We conclude that the nutrition support for patients with BMT is related to the success of marrow transplantation. Parenteral nutrition support, especially with TPN, is important because of frequent gastrointestinal dysfunction during the posttransplantational period, and it is better at maintaining the nutrition status and body weights of patients after BMT. An oral diet can be resumed after the patient's gastrointestinal function has improved and it can be tolerated.

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.

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.

Early curbing of protein hypercatabolism in postoperative patients by nutritional support with glucose plus amino acids, but not with glucose alone

This work attempts to determine if there are differences in protein metabolism in post-surgical patients who receive parenteral nutrition with amino acids plus glucose (G+AA) or conventional gluco-salinal solution (GS). Eighteen patients submitted to gastrointestinal surgery were randomized and double-blindly administered either G+AA (1 g AA/kg x d and 28 kJ/kg x d), or GS (28 kJ/kg x d). Protein metabolism was determined 12 h after surgery (day 0) and after 5 days of nutritional support. On day 0, protein breakdown was similarly elevated, with respect to reference values, in both groups (GS: 4.62 +/- 0.25; G+AA: 5.25 +/- 0.50 g prot/kg x d) as a result of surgical stress. These values increased significantly at day 5 (P < 0.03) with the administration of GS to 6.93 +/- 1.00 g prot/kg x d, while they decreased (P < 0.002, 3.30 +/- 0.42 g prot/kg x d) with G+AA. Protein synthesis was increased (5.69 +/- 0.86 g prot/kg x d) with GS (P < 0.02), and was decreased (2.79 +/- 0.44 g prot/kg x d) with G+AA (P < 0.0002). Both synthesis and breakdown were inside normal reference values after 5 days for group G+AA. In both groups, nitrogen balance did not change significantly at day 5 compared to day 0. G+AA is effective in curbing the hypermetabolism produced by postoperative stress, achieving normal protein metabolism in 5 days, while GS increases the protein breakdown and synthesis. Nitrogen balance does not detect these modifications of the protein metabolism. Undernutrition on prognosis is not yet fully recognized.