The effect of amino acids,carbohydrate and fat emulsion on the metabolism in gastrectomized patients

Nitrogen balance and other metabolic activity can be maintained by adequate calorie and protein supply during immediate post-gastrectomy period. Despite high intake of protein, great loss of nitrogen seems to occur in urine during infusion with polyalcohol sugars as compared with natural sugars, e.g., glucose, fructose and maltose. The best utilization of amino acids resulting in positive nitrogen balance and energy utilization were shown to be achieved by combined use of Intralipid, glucose, maltose and essential as well as non-essential amino acids in the clinical and laboratory studies.     

Substrate Interaction in Intravenous Feeding. Comparative Effects of Carbohydrate and Fat on Amino Acid Utilization in Fasting Man

Data are presented on the metabolic and endocrine effects of intravenous infusions in normal fasting man observed under highly controlled conditions over a period of six to eight days duration. There are comparative data on a variety of intravenous feeding programs. The data on total starvation are based on studies from the literature, some of which were carried out in this laboratory. The data on low dose glucose, high dose glucose, glycerol, fat emulsion, and amino acids, each given separately, demonstrate changes seen with simple infusion of a single substrate in fasting. These data are now compared with the utilization of amino acid infusions when accompanied by low dose glucose, high dose glucose, glycerol, and fat emulsion. In all, nine experimental intravenous feeding programs are presented, based on data from 35 subjects observed over a total of 370 subject-days. The findings show a strong interaction between glucose or lipid and protein metabolism. In fasting, glucose had protein sparing effect, most evident when given at high dose. Glycerol, in an amount equal to that contained in 2000 ml of ten per cent fat emulsion, had a mild protein sparing effect. Fat emulsion was no more effective. When amino acids were given alone, normal fasting human subjects were always in negative nitrogen balance with the daily nitrogen loss half that seen in starvation alone. Although amino acids given alone have a protein sparing effect, this is accomplished only at the expense of a high nitrogen excretion including an amount equivalent to the entire infusion plus an additional loss from the body's native proteins.The provision of energy yielding non-protein substrates with the amino acids markedly improved nitrogen economy in the following order: glycerol, low dose glucose, fat emulsion and high dose glucose. When caloric provision with glucose approached the isocaloric level for normal diet, the utilization of amino acids was maximized. When given with amino acids, fat emulsion was more effective than the available glycerol alone.THE ACCOMPANYING ENDOCRINE AND BIOCHEMICAL CHANGES SUGGEST THAT THE MILIEU FOR IDEAL UTILIZATION OF INFUSED AMINO ACIDS IS VARIABLE: ketones at low range (carbohydrate) or moderately elevated (fat emulsion); insulin elevated (carbohydrate) or unchanged (fat emulsion). The utilization of the infused amino acids was markedly improved in both endocrine settings, suggesting that it is the provision of energy as substrate as well as the endocrine setting that determines amino acid utilization. There were other changes in plasma intermediates, particularly fatty acids, glucose and urea, all consistent with the concept that when amino acids are given without other substrates, the amino acids must be maximally utilized for gluconeogenesis. When other substrates are provided (particularly glucose at high dose) then this mandate no longer exists and protein synthesis from the amino acids is favored.Several of the plasma amino acid concentrations responded to glucose when added to amino acid infusion. Amino acids alone produced increases in concentration of all the amino acids found in the infusion with the exception of alanine, arginine, and threonine. Many of these increases were abated by the addition of glucose to the amino acid infusion, suggesting an increased utilization rate. Glycerol and fat emulsion, while modulating increases in the plasma amino acid concentration, did so to a lesser extent than did glucose. This lowering of amino acid concentration was unaccompanied by an increase in urinary excretion. The assumption is therefore made that the provision of the added glucose favors the incorporation of amino acid into protein. There is no evidence from these data to suggest that a rising concentration of ketones in the blood favors amino acid utilization or protein synthesis.     

Adaptation to low-protein diets in renal failure: leucine turnover and nitrogen balance

In normal subjects, short to intermediate responses to dietary protein restriction include decreased amino acid oxidation and protein degradation plus increased utilization of amino acids for protein synthesis; these responses are activated to improve amino acid utilization and nitrogen balance. To assess whether chronic renal failure (CRF) impairs the adaptive responses to a low-protein diet, we measured nitrogen balance and the kinetics of infused L-(15N,1-13C)leucine during fasting and feeding. In six adult CRF and four control (C) subjects, 0.6 (LP) and 1.0 (HP) g protein kg-1 day-1 diets were compared. LP reduced feeding stimulated oxidation of leucine by 26% in CRF and 33% in C (P = NS). During fasting, oxidation was unaffected by diet or CRF. For both groups, feeding suppressed protein degradation to the same extent; leucine incorporation into protein did not change. Nitrogen balance during the two diets was the same with C and CRF, as was protein balance estimated from results of measured leucine kinetics. Thus, patients with CRF can activate appropriate adaptive responses to LP inasmuch as reduced amino acid oxidation occurring with feeding and estimates of protein balance did not differ from control.     

Intravenous Amino Acids as the Sole Nutritional Substrate: Utilization and Metabolism in Fasting Normal Human Subjects

The fasting normal human volunteer subject provides an ideal experimental setting for the initial investigation of foodstuffs whose use is proposed for the acutely ill surgical patient. In the normal human subject many variables can be controlled; the achievement of an ideal body fuel economy is quite simple; if a favorable utilization of injected foodstuffs cannot be achieved in this setting, it is unlikely, and remains to be proven, that utilization will be satisfactory under the challenges of acute surgical trauma. In this experimental model, employing four normal human volunteer subjects, nutrition has been provided by the intravenous infusion of isotonic amino acids (FreAmine(R) II) at a 3.4% concentration. No other source of calories or nutrients was provided. In this setting, utilization was very poor; the subjects were in negative nitrogen balance throughout. The nitrogen excretion was significantly greater than the total of infused nitrogen. The changes in protein, fat and carbohydrate intermediates, as well as the alteration in hormone concentrations, suggest the following endocrine governance of fuel economy in this setting: a sharp rise in glucagon with maintenance of insulin concentration; rapid gluconeogenesis at the expense of both injected and endogenous amino acids; a progressive ketosis without any associated improvement in protein economy; fat oxidation to meet caloric need. The changes in plasma amino acid concentrations are of outstanding interest. They demonstrate changes appropriate to the infusion gradient with the exception of three amino acids whose concentrations did not respond to high infusate levels (serine, lysine, and alanine); likewise, by the fact that methionine rose remarkably though present in only low concentrations in the infusion. These data, taken with other information reported in the literature, as well as continuing studies in these laboratories, strongly suggest that the utilization of infused amino acids for protein synthesis is favored by the provision of an additional caloric source such as glucose.     

Energy intake can determine albumin synthesis in man after surgery

Albumin synthesis rate, nitrogen balance, plasma hormone levels, and selected substrates were measured after operation in 12 patients who underwent colonic operations who were randomized to receive an intravenous fluid regimen that contained either 3.5% amino acids with 20% fat and 2.5% glucose or 3.5% amino acids with 20% fat alone. The albumin synthesis rate was higher in patients who received the first of these intravenous mixtures (357 +/- 34 mg/kg/day versus 216 +/- 22 mg/kg/day; p less than 0.01), but they also had a significantly higher intake of calories (10.2 +/- 1.1 calorie/kg/day versus 6.4 +/- 0.6 calorie/kg/day; p = 0.01). The mean albumin synthesis rate in the group who received amino acids with glucose and fat is the highest we have measured in our series of studies. Although a previous trial in a similar group of patients suggested that glucose acts on albumin synthesis by diverting uptake of amino acids into skeletal muscle, it is possible that the impressive increase in the albumin synthesis rate in patients of the present series who received supplementary glucose is related to the extra energy infused. In contrast, nitrogen balance was similar in both groups, and thus was not predictive of protein synthesis. In addition, myofibrillar protein degradation appears to be equivalent in the two groups, as indicated by 3-methylhistidine output. Plasma albumin synthesis thus may be sensitive, especially to energy intake.     

A controlled study of protein-sparing therapy after excision of the rectum: effects of intravenous amino acids and hyperalimentation on body composition and plasma amino acids.

This study considers the effects of glucose, during amino acid infusion, on protein-sparing and amino acid utilization after proctocolectomy or abdominoperineal resection of the rectum. Body composition and plasma amino acids were compared in each of three groups of patients before and 15 days after surgery who were receiving, in addition to restricted oral diets: 1) no hyperalimentation 2) parenteral amino acids or 3) hypertonic glucose plus amino acids. Parenteral solutions were given by central venous catheter. Infusion of amino acids alone spared body protein but branch chain amino acids (i.e. valine, isoleucine and leucine) and also phenylalanine, methionine and proline were increased well above the normal values. There were no increases in liver proteins other than for the "acute phase" type. In contrast, full hyperalimentation spared more body protein and fat, restored plasma amino acids to normal while plasma cortisol and acute pohase proteins were lower. Plasma transferrin, prealbumin and retinol binding protein were increased, as previously shown, while clinical outcome was more favorable. It is concluded that glucose is essential to ensure optimum utilization of amino acids for both muscle and liver protein synthesis and, therefore, intravenous hyperalimentation is preferable to amino acids alone after major colorectal surgery.     

Relative value of glucose and amino acids in preserving exercise capacity in the postoperative period

The value of crystalline amino acids compared with glucose in maintaining functional muscle mass (maximum exercise capacity) in the perioperative period was studied. Twelve surgical patients received 100 g of glucose (Group 1) for 7 to 10 days perioperatively, and 12 (Group 2) received 90 g of crystalline amino acids for a similar period. Maximum exercise capacity, nitrogen balance, and serum albumin were studied. The use of amino acids instead of glucose spared nitrogen. Net nitrogen loss was 64.7 +/- 6.7 g in Group 1 compared with 34.7 +/- 4 g in Group 2 (p less than or equal to 0.001). Exercise capacity decreased 13.8 +/- 4.5 percent in Group 1 and 13.3 +/- 2.9 percent in group 2. The serum albumin level decreased by 0.30 +/- 0.2 g/100 ml in Group 1 compared with 0.34 +/- 0.15 g/100 ml in Group 2. These differences were not significant. Changes in serum albumin were correlated with changes in exercise capacity (r = 0.7, p less than or equal to 0.002), but neither was significantly correlated with nitrogen loss. We concluded that the use of amino acids instead of glucose during moderate periods of semi-starvation associated with moderate trauma will not influence loss of exercise capacity significantly, although some nitrogen will be spared; patients undergoing moderately severe surgical procedures accompanied by moderate periods of semistarvation will lose approximately 14 percent of their exercise capacity; and loss of exercise capacity is not correlated with loss of nitrogen under these conditions but is loosely correlated with changes in serum albumin levels.     

Growth hormone stimulates protein synthesis during hypocaloric parenteral nutrition. Role of hormonal-substrate environment.

The influence of growth hormone (GH) on protein metabolism and fuel utilization was investigated in eight paired studies of normal volunteers. GH (10 mg) was given daily during one period, and saline was injected during control studies. For 6 days, subjects received parenteral nutrition that provided adequate dietary nitrogen, vitamin, and minerals, but energy intake varied to provide 30-100% of requirements. On Day 7, the feedings were discontinued and an oral glucose load (100 g) was administered. The level of energy intake did not markedly influence the actions of GH. During nutrient infusions, GH caused positive nitrogen balance (1.0 +/- 0.3 g/m2/day vs. -1.2 +/- 0.3 in controls, p less than 0.001) and increased protein synthesis (16.8 +/- 0.7 g N/m2/day vs. 13.9 +/- 0.8, p less than 0.01). No change in the rate of protein breakdown or excretion of 3-methylhistidine occurred. GH was associated with an increase in insulin and insulin-like growth factor-I concentrations (IGF-I, 9.1 +/- 0.6 IU/ml vs. 3.3 +/- 0.5, p less than 0.001). After discontinuation of the parenteral nutrition and administration of the oral glucose load, glucose concentrations tended to be higher after GH; however, despite a two- to threefold increase in insulin response, muscle glucose uptake was attenuated (1.10 +/- 0.19 g/kg forearm vs. 1.64 +/- 0.30 in controls, p less than 0.05). Compared with control conditions, GH appeared to attenuate the increase in amino acid nitrogen efflux from muscle after the administration of oral glucose. These data demonstrate that the protein anabolic effect of GH, which occurs even during hypocaloric feedings, is related to multiple mechanisms that favor protein synthesis. These include the increase in plasma concentrations of GH, insulin IGF-I and fat utilization. GH administration results in a hormonal-substrate environment that favors nitrogen retention and protein synthesis. GH may be beneficial in promoting protein synthesis in surgical patients, particularly in association with hypocaloric glucose infusions that allow utilization of body fat as an energy source.     

Total parenteral nutrition with F080 in cirrhotics with subclinical encephalopathy.

It has been proposed that hepatic encephalopathy and malnutrition in cirrhosis can be reversed by infusion of a protein formula (F080) enriched with branched-chain amino acids (valine, leucine, isoleucine) and containing decreased amounts of aromatic amino acids (phenylalanine, tyrosine, tryptophan). This hypothesis was tested by measuring changes in encephalopathy status, plasma ammonia, amino acid profile, and liver function during seven metabolic balance studies in three patients with cirrhosis and subclinical encephalopathy given increasing amounts (20-100 g/d) of F080. The results showed the following: 1) positive nitrogen balance was achieved only with 80 and 100 g F080/day; 2) plasma ammonia fell during negative, but increased during positive nitrogen balance; 3) plasma tyrosine and cystine fell significantly (p less than 0.05) with all intakes of F080; 4) the abnormal branched-chain to aromatic amino acid ratio was reversed; 5) extracellular volume was expanded in all patients; 6) albumin, bilirubin, prothrombin time became abnormal; and 7) encephalopathy did not significantly change from baseline. It is concluded that, in this population, F080 is an inadequate nutritional formula when given as the sole protein source because it produces hypotyrosinemia and hypocystinemia. The marked changes in the ratio of branched-chain to aromatic amino acids are not accompanied by improvement in encephalopathy.     

Peripheral intravenous feeding with isotonic amino acid solutions

Nitrogen balance was studied in ten patients receiving peripheral solutions of the following: (1) 5 per cent dextrose and water; (2) dextrose and 3 per cent amino acids; (3) amino acids alone. Significant improvement in nitrogen balance was observed when amino acids were administered without glucose. This was associated with lower insulin and glucose levels and with elevated levels of free fatty acids and ketones. A new concept on which to base parenteral protein-sparing therapy is presented.     

Basic metabolism: protein

Proteins serve a wide variety of functions. They are made by the sequential incorporation of amino acids in an order that is determined by genes and which in turn determine the final structure and thus the function of the protein. Proteins are constantly being synthesized and broken down at rates which exceed the amount of protein consumed in the diet and the equivalent amount of nitrogen that is excreted as urea in the urine. Some amino acids can be synthesized in the body (non-essential amino acids) but others (essential amino acids) must be supplied from dietary proteins in amounts that match the amounts that are oxidized. Hence the criterion of adequacy of a diet with respect to protein is its ability to maintain nitrogen balance in an adult and its ability to support normal growth in a child. During some critical illnesses there appears to be a constraint on the rate at which some non-essential amino acids can be synthesized, so that clinical benefits have been seen from supplementing the diet with these ‘conditionally-essential’ amino acids. Moreover, following surgery or during severe illness there is an increase in amino acid oxidation that can lead to muscle wasting. It is important to minimize the loss of lean tissue, but it may not be possible to prevent it completely by dietary means.     

The absence of protein--sparing effects utilizing crystalline amino acids in stressed patients.

The protein-sparing effects of the peripheral infusion of crystalline amino acids (PAA) was studied metabolically in selected surgical patients subjected to various degrees of stress. Twenty-one patients (sixteen cancer patients receiving chemotherapy and/or radiotherapy, three with major abdominal traumatic injuries and four with paralytic ileus) were infused with 2 1/24 hours of a solution of 4.2% Travasol amino acids with only 5% glucose as a source of nonprotein calories. One-half of the cancer patients were also allowed ad libitum oral intake of a regular hospital diet or Vivonex-HN. The nutritional status was evaluated by measuring changes in body weight, serum albumin levels and nitrogen balance. Body weight decreased in only the trauma patients. When these solutions were the sole source of nutrients all patients were in negative nitrogen balance and had significant decreases in their serum albumin levels. Serum albumin levels were preserved only when extra sources of calories were provided. The infusion of the crystalline amino acids without adequate levels of nonprotein energy did not conserve protein in these stressed patients.     

Impaired utilization of exogenous amino acids after surgery for subarachnoid haemorrhage

Summary We studied the metabolic response to acute aneurysm surgery and its modification by parenteral nutrition. Forty-eight patients receiving perioperative corticosteroid treatment were randomly assigned to receive glucose alone (7.2 kcal/day, D5W+C), glucose and a conventional amino acid solution (7.2 kcal/day and 0.15gN/ day, CAA+C) or glucose and branched chain amino acid enriched solution (7.2 kcal/day and 0.14 gN/day, BCAA+C). Twenty patients without corticosteroid treatment received either glucose alone (7.2 kcal/day, D5W) or glucose and a conventional amino acid solution (7.2 kcal/day and 0.14gN/day, CAA). Poor nitrogen utilization was indicated by strongly negative nitrogen balance in all groups and a failure of the infused amino acids to improve nitrogen balance. (Day0; D5W+C: –9.3±3.6g/day and CAA+C: – 8.2±9.7g/ day vs CAA: –2.6±4.9g/day, p<0.05,Day 1; D5W+C: –14.9 ±9g/day vs CAA:–7.7±6.5g/day, p<0.05, MANOVA). We conclude that subarachnoid haemorrhage and its surgical treatment induce a catabolic response and impaired utilization of exogenous nitrogen, further amplified by perioperative corticosteroids, which is in sharp contrast to the response to surgery not involving the central nervous system.     

Studies on the absorption of carbohydrate and nitrogen sources in elemental diets

To elucidate more efficient carbohydrate and nitrogen sources in elemental diets (ED), we constructed practical elemental diets in which glucose, maltose, or dextrin were used as carbohydrate sources, and crystalline amino acids (AA), small peptides (SP) or large peptides (LP) were used as nitrogen sources. We studied the absorption of carbohydrate, nitrogen and water in these elemental diets. Dogs were used as two experimental models. The Thirty-Vella loop was used as one model (a 40cm intestinal loop separated from the upper portion of the jejunum) so that the effect of digestive juice could be avoided. In the other model (jejunum fistula) two plastic tubes were indwelled in the upper portion of the jejunum, with the oral one being used for infusion of the ED and the other anal one being indwelled 40cm distal to the oral one and used for sampling of intestinal contents. In both loop models, glucose and maltose were absorbed more rapidly than dextrin. Water and nitrogen were absorbed more rapidly in the maltose-ED than glucose-ED. In another series of the studies where nitrogen sources were compared, SP was most rapidly absorbed in the AA-ED, SP-ED and LP-ED. The water absorption rate of the SP-ED was more than that of the AA-ED. These results suggest that maltose is most suitable for use as a carbohydrate source, and small peptides are most suited as a nitrogen source of the materials examined in the present study.     

Branched chain amino acid uptake and muscle free amino acid concentrations predict postoperative muscle nitrogen balance.

Amino acid solutions rich in branched chain amino acids (BCAA) are commonly utilized both clinically and in experimental protocols in an attempt to reduce skeletal muscle and whole body protein catabolism. To investigate the effectiveness of BCAA infusion, amino acid formulas containing varying concentrations of BCAA were given during operation in this study to three groups of dogs undergoing a standard laparotomy and retroperitoneal dissection. A fourth group was given saline alone. With the use of previously described hindquarter flux techniques, individual and total amino acid nitrogen exchange rates were measured and utilized in estimating skeletal muscle protein catabolism. Intracellular free amino acid concentrations were measured in percutaneous muscle biopsy samples. Although there was no relationship with the rate of BCAA infusion, there was a significant correlation between the rate of BCAA uptake by muscle and diminished total nitrogen release from hindquarter skeletal muscle after operation. There was also a significant relationship between muscle nitrogen balance and the postoperative change in the muscle concentration of either total amino acids or the single amino acid glutamine. When combined in a single equation, BCAA uptake and the change in muscle free amino acid concentration predict skeletal muscle nitrogen release with an r = 0.86. Thus, the rate of BCAA uptake and the free glutamine or total amino acid concentration in muscle appear to be independent predictors of muscle nitrogen balance. The nitrogen-sparing effect of BCAA in skeletal muscle is unrelated to infusion concentration or rate of infusion.     

Intraperitoneal nutrition

Provision of nutrients through the peritoneum is as old as peritoneal dialysis (PD) itself. Studies with a shelf-stable amino acid-based dialysis solution have shown that the amino acids absorbed during one exchange quantitatively exceed the daily losses of proteins and amino acids. The supplementary amino acids are well tolerated and can induce protein anabolism in many malnourished PD patients, as is evident from increased nitrogen balance, insulin-like growth factor-1, and increased concentrations of serum proteins. Such solutions offer a convenient means of providing nutritional supplementation to address the major nutritional needs of PD patients.     

Postoperative infusion of amino acids induces a positive protein balance independently of the type of analgesia used

BACKGROUND: Net loss of body protein is a prominent feature of the catabolic response to surgical tissue trauma. Epidural analgesia with hypocaloric dextrose has been demonstrated to attenuate leucine oxidation but was unable to make protein balance positive. The current study was set to determine whether an infusion of amino acids on the second day after colon surgery would revert the catabolic state and promote protein synthesis while maintaining glucose homeostasis in patients receiving epidural analgesia as compared with patient-controlled analgesia with morphine (PCA). METHODS: Sixteen patients undergoing colorectal surgery were randomly assigned to receive epidural blockade or PCA as analgesic techniques and underwent a 6-h stable isotope infusion study (3 h fasted, 3 h fed) on the second postoperative day. Whole body glucose kinetics and protein turnover were measured using [6,6-2H2]glucose and l-[1-13C]leucine as tracer. RESULTS: The infusion of amino acids caused a decrease in endogenous glucose rate of appearance in both groups (P < 0.05), with greater changes in the PCA group (P < 0.05). Administration of amino acids suppressed the appearance of leucine from protein breakdown in both groups (P < 0.05), although the decrease was greater in the PCA group (P < 0.05). Leucine oxidation increased in both groups (P < 0.05), with greater change in the epidural group (P < 0.05). Protein synthesis increased to the same extent in both groups (P < 0.05). Protein balance became positive after the infusion of amino acids, and the effect was greater in the PCA group (P < 0.05). CONCLUSIONS: Infusion of amino acids decreased the endogenous glucose production and induced a positive protein balance independent of the type of anesthesia provided, although such effects were greater in the PCA group.     

A prospective randomized study of the optimal source of nonprotein calories in total parenteral nutrition

We previously showed that providing 30% of nonprotein calories as lipid eliminated glucose intolerance and ameliorated the other troublesome metabolic complications of total parenteral nutrition (TPN): hepatic abnormalities and hypertriglyceridemia. Whether such a mixed-fuel system is as effective as a hypertonic glucose-only TPN fuel system in achieving an anabolic state was tested in 88 consenting patients randomized to either conventional TPN (25% dextrose and 4.25% amino acids) or modified TPN (15% dextrose, fat, and 5% amino acids). Treatment groups were: group A, no surgery, TPN only; group B, postoperative TPN starting 48 hours after surgery; and group C, preoperative TPN, surgery on day 7 and with continued postoperative TPN. In all groups TPN was given for 14 days while patients were given nothing by mouth. Changes in the indexes of body protein metabolism, reflected by nitrogen balance, serum albumin, blood urea nitrogen, and weight, were measured on days 1 and 14. Nitrogen balance improved in patients randomized to either regimen, but there was no significant difference in the degree of improvement. Albumin levels were maintained, and differences between initial and final values were not significant. Blood urea nitrogen increased in all groups (p less than 0.05); however there was no significant difference between regimens. Patients maintained their weight, and fluid balance data indicated no water retention. Observed weight changes were not statistically significant. In each treatment group an anabolic state occurred and gains in measured protein indexes were similar. Isocaloric replacement of 30% of TPN glucose calories with fat was as effective as glucose-only TPN in achieving an anabolic state without the metabolic complications associated with glucose-only TPN.     

Whole-body nitrogen and tyrosine metabolism in surgical patients receiving branched-chain amino acid solutions

Fifteen patients undergoing gastric bypass surgery for morbid obesity received preoperatively a standard crystalline amino acid solution containing 15.6% branched-chain amino acids. During the first five postoperative days, the patients were randomized to receive one of three amino acid solutions (9.0 to 10.3 g of nitrogen per day) of different branched-chain amino acid content. The branched-chain amino acid concentrations of the mixtures were 15.6%, 50%, and 100% by weight with five patients in each group. Whole-body amino acid appearance and oxidation were estimated using a continuous intravenous infusion of L-(U-14C)-tyrosine preoperatively and on the third postoperative day. Daily postoperative nitrogen balance, fractional albumin renewal rate, and whole-body tyrosine appearance, oxidation, and incorporation into protein were not significantly different among the three groups. This study suggests that an adequate nitrogen intake of a balanced amino acid mixture, as well as a solution enriched with branched-chain amino acids, maintains protein homeostasis and supports protein synthesis similarly in well-nourished patients following major abdominal surgery. A diet containing only branched-chain amino acids in isomolar ratios was as effective at maintaining protein retention and whole-body protein synthesis and albumin renewal postoperatively when compared with a standard amino acid formula.     

Postoperative total parenteral nutrition in patients with liver disorders

Sixty-one patients with liver disorders receiving total parenteral nutrition (TPN) for about 14 postoperative days were divided into three groups based on the parenteral nutritional regimen. The influence of these TPN solutions on the liver function tests and the nutritional assessments, and the availability of the specially formulated amino acid solution were studied. Glucose alone as energy source was infused in Group Ia. The mixture of glucose and fructose was infused in Group Ib. In these patients (Group I), a commercially available amino acid solution was administered simultaneously. A specially formulated amino acid, rich in branched-chain amino acids but poor in aromatic amino acids was infused with the mixture of glucose and fructose in Group II. There was no remarkable elevation of blood glucose and lactate levels in all patients. Blood glucose levels in Group Ib were maintained lower than that in Group Ia. Except for serum alkaline phosphatase, no remarkable abnormality was observed in liver function tests. Body weight changes were less than 5% in each group. Average nitrogen balances were -44.5 mg/kg/day in Group Ia, -5.5 mg/kg/day in Group Ib, -51.5 mg/kg/day in Group II. While the abnormalities in serum amino acid pattern and molar ratio of leucine, isoleucine, and valine to phenylalanine and tyrosine tend to be more enhanced in Group I, these abnormalities returned to near normal in Group II during TPN. By multiple linear regression analyses, 45 kcal/kg/day of energy intake would be required to maintain nitrogen equilibrium and zero body weight change. And when nitrogen intakes were 159 mg/kg/day in Group Ia, 114 mg/kg/day in Group Ib, and 189 mg/kg/day in Group II at 45 kcal/kg/day in energy intake, nitrogen balances were expected to be equivalent. These results suggest that postoperative TPN is good for nutritional support in patients with liver disorders. And also, the combination of glucose and fructose has better effect on nitrogen balance. The postoperative TPN with a specially formulated amino acid solution may be a valuable way of maintaining the nutritional status as well as normal serum amino acid pattern in patients with liver disorders.