Protein sparing therapy during periods of starvation with sepsis of trauma

An assessment of nutritional depletion following major colonic surgery

This study was undertaken to determine the changes in basic nutritional indices associated with major colonic surgery accompanied by periods of semi-starvation. Changes in weight, serum albumin, nitrogen balance, and maximum exercise capacity were studied. Weight loss was 5.5 +/- 1 per cent, serum albumin decreased 0.20 +/- 0.15 gm per cent. Nitrogen loss was 5.9 +/- 0.9 gm per day and maximum exercise capacity decreased by 13.5 +/- 1.8 per cent. Nitrogen balance improved when amino acids were substituted for glucose as the maintenance regimen, but no corresponding improvement in exercise performance could be demonstrated. It is concluded that major colonic surgery associated with moderate periods of semi-starvation is associated with an average nitrogen loss of 5.9 +/- 0.9 gm per day and a 13.5 +/- 1.8 per cent loss in maximum exercise capacity or effective muscle mass.

The effect of different carbohydrate intakes on body weight and nitrogen balance during nasogastric feeding after faciomaxillary surgery

In order to assess the effects on body composition of different carbohydrate intakes when nitrogen supply is constant and adequate (9 g/day), we gave either no carbohydrate, sufficient to avoid ketosis (100 g) or at least enough to satisfy energy needs (600 g) to a group of six patients after major faciomaxillary surgery. Each patient was given the different feeds for 3-day periods in a randomised, cross over design. 100 g carbohydrate was effective in avoiding negative nitrogen balance, but weight loss was only prevented when 600 g was used. Differences in water balance suggest that mobilisation and repletion of body glycogen (with associated water) probably account for most of these differences in body weight changes.

Free fatty acid mobilization and oxidation during total parenteral nutrition in trauma and infection

Free fatty acid (FFA) metabolism was studied in 18 traumatized and/or septic patients. Each patient was studied while receiving 5% dextrose (D5W) and after 4 to 7 days of total parenteral nutrition (TPN). Nonprotein energy during TPN was given either entirely as glucose (Glucose System) or as equal portions of intravenous fat and glucose (Lipid System). Plasma FFA concentrations were in the normal range on D5W and decreased markedly with TPN. FFA turnover was higher than normal on D5W and did not decrease significantly with TPN. The poor correlation between these two variables emphasizes the need to perform kinetic studies to characterize FFA metabolism in trauma and sepsis. Plasma FFA oxidation and net whole body fat oxidation measured by indirect calorimetry were in the normal range on D5W, 35 and 82%, respectively, of resting energy expenditure (REE). With a glucose intake averaging 108% of REE, plasma FFA oxidation and net fat oxidation decreased to 17 and 13%, respectively, of REE. Nonprotein RQ increased only to 0.94 despite administration of glucose in excess of REE, indicating an abnormal persistence of fat oxidation. During D5W administration, plasma FFA accounted for less than one half of total fat oxidation, indicating that unlabeled fat, such as tissue or plasma triglycerides not in rapid equilibrium with plasma FFA, accounted for the bulk of fat oxidation. Glucagon concentrations which were high on D5W did not decrease significantly with TPN. Insulin concentrations were normal on D5W and increased in response to TPN. The abnormal hormonal milieu may account for much of the abnormal fat metabolism. Administration of large amounts of glucose decreased FFA oxidation much more than FFA mobilization. Thus, the infused glucose acts to increase the rate of "futile cycling" of FFA in these acutely ill patients.

The human metabolic response to chronic ketosis without caloric restriction: physical and biochemical adaptation

To study the metabolic effects of ketosis without weight loss, nine lean men were fed a eucaloric balanced diet (EBD) for one week providing 35-50 kcal/kg/d, 1.75 g of protein per kilogram per day and the remaining kilocalories as two-thirds carbohydrate (CHO) and one-third fat. This was followed by four weeks of a eucaloric ketogenic diet (EKD)--isocaloric and isonitrogenous with the EBD but providing less than 20 g CHO daily. Both diets were appropriately supplemented with minerals and vitamins. Weight and whole-body potassium estimated by potassium-40 counting (40K) did not vary significantly during the five-week study. Nitrogen balance (N-Bal) was regained after one week of the EKD. The fasting blood glucose remained lower during the EKD than during the control diet (4.4 mmol/L at EBD, 4.1 mmol/L at EKD-4, P less than 0.01). The fasting whole-body glucose oxidation rate determined by a 13C-glucose primed constant infusion technique fell from 0.71 mg/kg/min during the control diet to 0.50 mg/kg/min (P less than 0.01) during the fourth week of the EKD. The mean serum cholesterol level rose (from 159 to 208 mg/dL) during the EKD, while triglycerides fell from 107 to 79 mg/dL. No disturbance of hepatic or renal function was noted at EKD-4. These findings indicate that the ketotic state induced by the EKD was well tolerated in lean subjects; nitrogen balance was regained after brief adaptation, serum lipids were not pathologically elevated, and blood glucose oxidation at rest was measurably reduced while the subjects remained euglycemic.

Effects of hypertonic glucose on the rates of plasma clearance and CO2 production of intravenously administered intralipid emulsion in dogs

Simultaneous infusion of glucose and Intralipid was carried out on dogs to evaluate the effect of glucose on utilization of the fat emulsion. For control experiments, normal saline was used in place of glucose. Results of these studies revealed that clearance of Intralipid and also of triglyceride and free fatty acid (FFA) from the plasma did not differ between the dogs receiving glucose and those receiving saline infusion. The rates of Intralipid clearance were 0.049 +/- 0.003 and 0.047 +/- 0.003 per minute (n = 16), respectively. Study with radioactive [14C]Intralipid also gave similar rates of 14C clearance from the plasma, 0.037 +/- 0.003 and 0.040 +/- 0.003 per minute (n = 4), respectively for the two groups. These suggested that clearance of Intralipid from the plasma was not affected by glucose. However, data on expired 14CO2 revealed that oxidation of the fat, which yielded CO2 as end product, was inhibited by glucose. The amount of 14CO2 expired in 2 hours was 10.4 +/- 1.4% for the saline group, which was significantly reduced to 3.0 +/- 0.4% (n = 4; p less than 0.01) for the glucose group. In each group, CO2 production was much delayed as compared to fat clearance from the plasma. Thus, the rate of clearance of Intralipid from plasma does not reflect the actual utilization of fat emulsion. In accordance with an experiment with insulin, it appears that suppression of CO2 production is directly related to plasma insulin levels.

Effects of carbohydrate-containing and carbohydrate-restricted hypocaloric and eucaloric diets on serum concentrations of retinol-binding protein, thyroxine-binding prealbumin and transferrin

The effects of diet on the serum concentrations of albumin, transferrin, thyroxine-binding prealbumin (TBPA) and retinol-binding protein (RBP) were studied in 3 groups of obese subjects (Groups I-III) and 1 group of normal weight subjects (Group IV). Group I subjects ate either a 830 kcal carbohydrate-containing diet (CCD) or carbohydrate-restricted diet (CRD), Group II and III subjects ate a hypocaloric CRD. Subjects in Group IV ate a eucaloric CRD. Serum albumin concentrations did not change in any of the 4 groups. Only the subjects in Group II had a statistically significant decrease in serum transferrin concentration 6 wk after starting the hypocaloric, CRD. Group I individuals eating the CRD and the subjects in Groups II, III and IV had significant decreases in the serum concentrations of TBPA and RBP after 1 wk which persisted without further change during the remaining 3-5 wk of the diets. Group I subjects eating the CCD had a significant decrease in TBPA concentration at 1 and 6 wk. The RBP serum concentration was significantly decreased after 1 wk on the diet, but was not significantly different from the control diet period at 6 wk. The magnitude of the decreases in serum concentrations of TBPA and RBP in the Group I subjects eating the CRD were significantly greater than in the Group I subjects eating the CCD. Thus, ingestion of a hypocaloric, CRD by obese individuals results in decreased serum concentrations of TBPA and RBP. Isocaloric substitution of carbohydrate for fat reduces this effect. Dietary carbohydrate apparently modulates the serum concentrations of TBPA and RBP, independently of caloric intake, since ingestion of a eucaloric CRD by normal weight individuals also decreased the serum concentration of the two visceral proteins.

The effects of nitrogen and energy intake on the metabolism of normal, depleted and injured man: Considerations for practical nutritional support

This article illustrates how the nutritional and metabolic effects of a range of protein and energy intakes depend on the clinical state of the patient and how these considerations may be used to provide guidelines for nutritional support. First, it is necessary to define states and mechanisms of malnutrition and then discuss the biochemical processes which underlie nutritional rehabilitation.

The metabolic effects of isotonic amino acid infusion in surgical sepsis

28 normally nourished adult male and female patients who had undergone major elective surgery were maintained on dextrose-free isotonic amino acid solutions as their sole nutritional support. In the 6 days after surgery, 15 patients had no septic complications, 9 developed superficial sepsis, and 4 developed a deep seated collection of pus or deep sepsis. Patients without infection developed and maintained a fasting metabolic fuel profile within the first 3 days and increasingly spared protein. Superficial sepsis caused a small depression in serum ketone body concentrations but did not otherwise alter the fasting profile. Moreover nitrogen balances and plasma albumin and transferrin concentrations were unaltered by superficial sepsis which is not the response usually recognised with infection. Metabolic adaptation to the fasting state was lost in patients with deep sepsis and nitrogen losses were increased with greater decreases in plasma albumin and transferrin.

Optimal dietary therapy for obese adolescents: comparison of protein plus glucose and protein plus fat

Nitrogen balance in six obese adolescent boys and three obese girls was studied during two nonconsecutive three-week dietary periods. Protein intake was based on an ideal body weight calculated from the measurement of total body water. The diets consisted of 1.5 gm meat protein/kg IBW/day plus 1.0 gm glucose/kg IBW/day, or an isonitrogenous diet made isocaloric with fat. Each dietary period was preceded by a controlled five-day diet designed to achieve weight maintenance. The first dietary period was followed by a one-month period of re-equilibration. The addition of carbohydrate to protein produced a significantly better cumulative nitrogen balance than P + F. Significant nitrogen losses persisted throughout the entire dietary period of P + F in three patients, but were observed in only one patient during P + G. Lymphopenia occurred in one subject on P + F but did not occur during P + G. Serum albumin concentrations were unchanged on both diets. Transferrin values decreased during P + F, but did not differ significantly from prediet levels during P + G. However, the observation of prolonged nitrogen losses in one subject on P + G and the limited experience with highly restrictive diets in obese adolescents emphasize that such diets must be used with caution and monitored carefully.

Morphological fatty changes and function of the liver, serum free fatty acids, and triglycerides during parenteral nutrition

Morphological fatty changes and function of the liver and serum free fatty acids and triglycerides were investigated in 37 catabolic patients (22 men, 15 women) given different parenteral nutrition regimens. In the glucose group energy was supplied as carbohydrate alone, in the lipid group as carbohydrates and fats, and in addition both groups received amino acids. In the amino acid group amino acids were given in excess and less energy was supplied as carbohydrates. Each patient served as his own control. During parenteral nutrition liver steatosis rose from 5% to 35% (p less than 0.001) in the glucose group and from 7% to 23% (p less than 0.01) in the amino acid group, but no increase occurred in the lipid group. Liver fat accumulation was associated with the rises in serum aminotransferase activities and with the lack of or a poor rise in serum prothrombin and proconvertin. The conjugation function of the liver was not disturbed. No cholestatis was found. During lipid infusion serum free fatty acids increased to 4.41 mmol/l (p less than 0.01) and serum triglycerides to 3.06 mmol/l (p less than 0.01), but they decreased to normal range 12 h after lipid infusion was stopped. In the glucose and amino acid groups serum free fatty acid levels fell, as expected, below the normal range. Serum triglycerides rose 1.4-fold (p less than 0.05) in the amino acid group. On the basis of liver tests and histological examination steatosis in the liver caused only a minor disturbance in hepatocellular integrity. The very high levels of serum free fatty acids and triglycerides during lipid infusion may be harmful in certain pathological states.

Effect of postoperative nutrition on muscle high energy phosphates

This study examines the effect of hypocaloric nutritional regimens on muscle high energy phosphates in normal subjects and patients following total hip replacement. Eighteen patients undergoing total hip replacement and 11 normal subjects on a four-day period of bedrest were studied. The patients were randomly assigned to receive either: (1) 90 gms/day glucose; (2) 70 gms/day amino acids; or (3) 90 gms/day glucose + 70 gms/day amino acids. A percutaneous muscle biopsy was performed before operation and on the morning of the fourth day after operation. Samples were analyzed for adenine triphosphate (ATP), adenine diphosphate (ADP), adenine monophosphate (AMP), phosphocreatine (PC), free creatine (CR), lactate, and pyruvate. Normal subjects were assigned to receive either: (1) 90 gms/day glucose; (2) 70 gms/day amino acids; or (3) no caloric intake. The patients receiving amino acid alone demonstrated a decrease in ATP, ADP, and PC, while AMP and free creatine rose. No significant changes were seen in patients who received 90 gms/day glucose either with, or without, amino acids. There were also no significant changes in any of the normal subjects. These results suggest that a series of metabolic changes occur in skeletal muscle following injury such that small amounts of glucose are important for maintenance of cellular energy levels.

Influence of abdominal surgical trauma and intra-operative infusion of glucose on splanchnic glucose metabolism in man

Abdominal surgery increases blood glucose concentration and peripheral release and splanchnic uptake of gluconeogenic substrates, including alanine. During trauma or sepsis, infusion of glucose fails to depress alanine conversion to glucose. The effect of intra-operative glucose infusion on splanchnic metabolism was examined in the present study. In eight patients undergoing elective cholecystectomy, splanchnic glucose metabolism was investigated before, during and immediately after surgery. Glucose was infused at a constant rate of 1 mmol/min. Splanchnic blood flow and arterio-hepatic venous differences of oxygen, glucose, lactate, glycerol, 3-hydroxybutyrate and alanine were measured. Eight other patients, who received saline instead of glucose, served as a control group. Infusion of glucose resulted in total inhibition of splanchnic glucose release before as well as during and immediately after surgery. This was observed, even before surgery, at an arterial glucose level which was lower than that in the control group at the end of and immediately after surgery, at which no decrease of the splanchnic glucose release was recorded. changes in neuronal and hormonal factors due to the surgical trauma are considered responsible for this difference in glucose homeostasis. Splanchnic alanine uptake increased during surgery in both groups, but tended to be somewhat lower in the glucose group. The arterial glycerol concentration and splanchnic uptake, as well as the arterial concentration and splanchnic release of 3-hydroxybutyrate, were reduced. It is concluded that an intravenous infusion of glucose at the rate of 1 mmol/min during abdominal surgery (a) increases the arterial blood glucose level and abolishes splanchnic glucose release, (b) reduces, but does not totally prevent the increase in splanchnic uptake of gluconeogenic substrates, and (c) diminishes lipolysis and the formation of 3-hydroxybutyrate.

[Protein-sparing effect of various types of peripheral parenteral nutrition]

A randomized clinical study was performed postoperatively in a total of 47 patients comparing three different concepts of peripheral parenteral nutrition. Substituting 1 g amino acids (AA)/kg b.w. daily, the amount of carbohydrates (CH) was changed solely: gr. II no carbohydrates (sole AA-substitution), gr. III 2 g CH/kg b.w. (hypocaloric nutrition) and gr. IV 5 g CH/kg b.w. (basic nutrition). The influence on protein metabolism was examined by cumulative N-balances, various plasma proteins viscerally synthesized and serum amino acids predominantly utilised in peripheral tissues. In comparison to a non-fed-control group (I), hypocaloric nutrition showed the qualitative most favourable protein-sparing effect. Besides, 87% of N-retention serum levels of plasma proteins and amino acids investigated could be normalized completely. Peripheral basic nutrition also had a 88% rate of N-retention, however, only peripherally utilised amino acids were influenced beneficially whereas the plasma proteins remained depleted. Sole AA-substitution neither affected amino acid levels nor plasma proteins, and the N-retention rate was significantly lowered (67%). Possibly this type of therapy increases protein turnover solely, while true protein-sparing took place only with additional CH supply. However, a positive effect on visceral protein synthesis was observed exclusively with hypocaloric nutrition.

Parenteral nutrition by peripheral vein

Peripheral parenteral nutrition can provide perioperative nutritional support to patients with inadequate oral intake in whom total parenteral nutrition with hypertonic dextrose administered by a central vein cannot be undertaken because of sepsis, subclavian vein thrombosis, or lack of expertise and familiarity. Peripheral parenteral nutrition may be indicated in patients with marginal nutritional status whose postoperative course and period of starvation are unpredictable and in patients being started on a total enteral nutrition regimen. In patients with increased requirements because of stress or malnutrition who need full nutritional support by a peripheral method, the lipid system is indicated. In certain instances, large enough volumes can be infused to provide sufficient calories and protein for nutritional repletion. Protein-sparing therapy is indicated for nutritional maintenance in patients who do not clearly require full support by total parenteral nutrition but who are taking insufficient calories and protein orally. Peripheral parenteral nutrition avoids the risks of subclavian vein catheterization but requires that adequate peripheral veins are available. The metabolic complications are minimal compared with those of total parenteral nutrition, and the nutritional management of the diabetic patient is greatly simplified. Several techniques of preserving peripheral veins and prolonging their use have been discussed.

Energy metabolism, substrate utilization, and nitrogen balance in parenterally fed postoperative neonates and infants. The effect of glucose, glucose + amino acids, lipid + amino acids infused in isocaloric amounts

In ten postoperative neonates and young infants the effect of three isocaloric, isovolemic intravenous nutritional regimens (glucose alone, amino acids + glucose, amino acids + lipid) on nitrogen balance, energy, and substrate metabolism were tested. Each regimen was given for 24 hours to each infant through three consecutive days, providing the same daily amino acid intake when the amino acid mixture was combined with glucose or lipid. Oxygen consumption and RQ were followed through three or four hours during each study period. The participation of three main nutrients in energy metabolism was calculated from the urinary N excretion and nonprotein RQ. Administration of glucose infusion alone was associated with a negative N balance. Addition of amino acids with glucose produced a marked N retention. This positive N balance remained unchanged when lipid was substituted for glucose as a nonprotein energy source. Alpha amino-nitrogen excretion and participation of protein catabolism in total energy metabolism were found to be identical during the three nutritional regimens, indicating that the amino acids together with glucose or lipid were either retained in nonprotein pools or were utilized for protein synthesis.

Capacity for moderate exercise in obese subjects after adaptation to a hypocaloric, ketogenic diet

To study the capacity for moderate endurance exercise and change in metabolic fuel utilization during adaptation to a ketogenic diet, six moderately obese, untrained subjects were fed a eucaloric, balanced diet (base line) for 2 wk, followed by 6 wk of a protein-supplemented fast (PSF), which provided 1.2 g of protein/kg ideal body wt, supplemented with minerals and vitamins. The mean weight loss was 10.6 kg. The duration of treadmill exercise to subjective exhaustion was 80% of base line after 1 wk of the PSF, but increased to 155% after 6 wk. Despite adjusting up to base line, with a backpack, the subjects' exercise weight after 6 wk of dieting, the final exercise test was performed at a mean of 60% of maximum aerobic capacity, whereas the base-line level was 76%. Resting vastus lateralis glycogen content fell to 57% of base line after 1 wk of the PSF, but rose to 69% after 6 wk, at which time no decrement in muscle glycogen was measured after >4 h of uphill walking. The respiratory quotient (RQ) during steady-state exercise was 0.76 during base line, and fell progressively to 0.66 after 6 wk of the PSF. Blood glucose was well maintained during exercise in ketosis. The sum of acetoacetate and beta hydroxybutyrate rose from 3.28 to 5.03 mM during exercise after 6 wk of the PSF, explaining in part the low exercise RQ. The low RQ and the fact that blood glucose and muscle glycogen were maintained during exhausting exercise after 6 wk of a PSF suggest that prolonged ketosis results in an adaptation, after which lipid becomes the major metabolic fuel, and net carbohydrate utilization is markedly reduced during moderate but ultimately exhausting exercise.

Factors influencing the composition of the weight lost by obese patients on a reducing diet

1. Weight loss, resting metabolic rate and nitrogen loss were measured in forty obese inpatients on reducing diets. 2. Five subjects ate 3.55 MJ/d for 6 weeks (Expt 1). Twenty-one subjects ate 4.2 MJ/d for the first week, 2.0 MJ/d for the second week and 4.2 MJ/d for the third week (Expt 2). Fourteen subjects ate 3.4 MJ/d for the first week and then 0.87 MJ protein or carbohydrate for the second or third weeks, using a cross-over design for alternate patients (Expt 3). 3. Patients in Expt 1 had highest weight loss and N loss in the first 2 weeks, but adapated to the energy restriction over the remaining weeks. On average subjects were in N balance at the end of the study. 4. In Expt 2 patients eating 2.0 MJ/d in week 2 showed increased weight loss compared with week 1. N loss was not raised but it failed to decrease as it had in Expt 1. Weight loss and N loss were reduced on return to 4.2 MJ/d for a third week. 5. In Expt 3 patients eating 0.87 MJ protein showed significantly more weight loss and less N loss than patients eating 0.87 MJ carbohydrate. 6. Resting metabolic rate decreased with time on the low-energy diet, but the manipulations of energy or protein content did not significantly affect the pattern of decrease. 7. Both weight loss and N loss were greater the lower the energy intake, and both decreased with time. Diets with a high protein:energy value give a favourable value for N:weight loss at each level of energy intake.

The effect of different calorific doses of carbohydrate on nitrogen excretion after surgery

The protein-sparing effect of different calorific regimens [0.025 MJ (6 kcal); 0.105 MJ (25 kcal); 0.167 MJ (40 kcal) per kg body weight per 24 h] of postoperatively infused glucose has been studied in 18 patients undergoing operations of intermediate severity. Carbohydrate infusion has a progressive nitrogen-sparing effect. However, the increased negative nitrogen balance associated with surgical stress could not be prevented completely.

In vivo demonstration of nitrogen-sparing mechanisms for glucose and amino acids in the injured rat

Changes in protein metabolism 8 hr after anesthesia and femur fracture were studied in healthy rats fasted or receiving either intravenous glucose or crystalline amino acids. Whole body rates of amino acid turnover (flux) and release from protein (breakdown) as well as fractional synthetic rates of mixed muscle, liver, and plasma protein were measured using the constant infusion of L-(I-14C)-leucine. Injury resulted in a 24% increase in the synthesis of liver (p less than 0.05) and plasma proteins (p less than 0.01), respectively. Amino acid infusions in the injured animals further increased the synthesis of liver protein (from 36.6% to 44.3%/day, p less than 0.05) and increased muscle protein synthesis (from 7.0% to 9.3%/day, p less than 0.05) without altering rates of protein breakdown. Glucose infusions, in contrast, reduced whole body protein breakdown 36% (p less than 0.05) when compared to fasting, and depleted the plasma essential amino acid pool (p less than 0.05). The usual increases in liver protein synthesis observed in fasted rats following injury were not seen when the animals were receiving intravenous glucose. The nitrogen-sparing mechanism of these two infusions are different. Protein-free glucose infusions impair the normal response to injury aimed at increasing visceral protein synthesis and maintaining plasma essential amino acid concentrations.

Consequences of modified fasting in obese pediatric and adolescent patients. I. Protein-sparing modified fast

Sixteen obese patients 9 to 16 years of age were treated with a protein-sparing modified fast for four weeks in a metabolic unit, using lean meat as the sole calorie-containing nutrient. Total weight loss was 7.11 +/- 0.33 kg (mean +/- SEM). One-half of the patients achieved positive daily nitrogen balance by the fourth week. Cumulative N balance was -28.8 +/- 10.0 gm. Serum albumin concentration remained normal. Hemoglobin and hematocrit values were stable, but decreases in total lymphocyte (P less than 0.005) and neutrophil counts (P less than 0.01) were noted. Cell-mediated immunity (four patients) remained normal. Protein synthetic and catabolic rates (two patients) revealed only minimal changes. Cumulative N balance correlated (P less than 0.01) with mean fasting serum insulin concentration, which was related (P less than 0.005) to body fat mass. The PSMF has therapeutic potential for achieving safe, rapid weight loss in severely obese older children and adolescents.

The nitrogen to creatinine ratio in untimed samples of urine as an index of protein catabolism after surgery

The loss of nitrogen after surgery is said to be related to body size as well as to the magnitude of the metabolic effects of surgery. Urine nitrogen should be 'corrected' for body size before it can be taken as a guide to the severity of surgery in the individual. Twenty-three patients were studied after elective abdominal surgery of moderate severity, when they were having only 3 litres of dextrose saline daily. The 24-hr urine nitrogen excretion (mean of days 3 and 4) was correlated with 3 indices of body size, body weight (r = 0.614), fat-free mass (r = 0.743) and 24-hr creatinine excretion (r = 0.780). Nitrogen excretion was corrected for body size by calculating the ratio of nitrogen to each index. For each index the s.d. of this corrected nitrogen excretion at the mean value of the index was less than the s.d. of the uncorrected data. The nitrogen : creatinine ratio in an untimed urine sample was closely related to the ration in the 24-hr urine (r = 0.914). These results demonstrate that nitrogen excretion after surgery is related to body size and can be corrected for body size by calculating the nitrogen : creatinine ratio in an untimed urine.

Intravenous protein-sparing therapy in patients with gastrointestinal disease

Two groups (each of 6 moderately ill, protein-depleted patients) were infused daily for 7 days. Mean 7 day nitrogen (N) balances with infusions of 0.83 and 1.83 g of a defined amino acid mixture (containing further nutrients but no other source of energy)/kg ideal body wt/day were -3.66 and +1.54 g/day, respectively (P less than 0.025) when adjusted for changes in body urea and estimated miscellaneous N losses. Concentrations of plasma free fatty acids, immunoreactive insulin and glucagon, and of blood glucose, pyruvate, lactate and glycerol were indistinguishable on corresponding treatment days in the 2 groups but blood ketone bodies were lower in the 1.83 g/kg group. Blood amino acid concentrations of alanine, valine, leucine, and isoleucine were similar, whereas those of phenylalanine, histidine, serine, and arginine were higher, and glutamine lower, in the 1.83 g/kg group. The data confirm that not only can body protein mass be maintained, but a net positive N retention achieved, in such patients, through provision of exogenous amino acids and concurrent mobilization of endogenous energy stores. Of note is that this fat mobilization can occur without plasma free fatty acids and/or significant blood ketone body elevations. An infusion of 2, rather than 1 g/kg/day seems suitable in the situation examined.

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.

Effect of inflammatory and noninflammatory stress on plasma ketone bodies and free fatty acids and on glucagon and insulin in peripheral and portal blood

Inflammatory stress as characterized by infection with Streptococcus pneumoniae, administration of endotoxin, or the induction of a turpentine abscess is characterized by the inhibition of the ketosis assoicated with fasting and a decline in the level of free fatty acids in the plasma. Moreover, rats subjectd to these inflammatory stresses demonstrate a significant rise in peripheral and portal insulin and glucagon. Rats subjected to noninflammatory stresses, screen-restraint, or noninvasive femoral fracture did not demonstrate the inhibition of ketosis but did show a decrease in plasma free fatty acids. The noninflammatroy stresses did not show an abnormal elevation of plasma or portal insulin or glucagon.

Nitrogen balance and electrolyte requirements in intralipid-based hyperalimentation

The present study was directed at determining whether or not a relatively low-calorie regimen in which 40 to 50% of the calories are provided as fat will produce positive nitrogen balance in most patients, and at establishing the electrolyte requirements for such a regimen. Clearly, the recommended regimen is successful in promoting nitrogen balance and provides adequate electrolytes. Further experience will be necessary to determine the place of intravenous fat emulsions in the clinical practice of total parenteral nutrition.

Energy metabolism in feasting and fasting

During feasting on a balanced carbohydrate, fat, and protein meal resting metabolic rate, body temperature and respiratory quotient all increase. The dietary components are utilized to replenish and augment glycogen and fat stores in the body. Excessive carbohydrate is also converted to lipid in the liver and stored along with the excessive lipids of dietary origin as triglycerides in adipose tissue, the major fuel storage depot. Amino acids in excess of those needed for protein synthesis are preferentially catabolized over glucose and fat for energy production. This occurs because there are no significant storage sites for amino acids or proteins, and the accumulation of nitrogenous compounds is ill tolerated. During fasting, adipose tissue, muscle, liver, and kidneys work in concert to supply, to convert, and to conserve fuels for the body. During the brief postabsorptive period, blood fuel homeostasis is maintained primarily by hepatic glycogenolysis and adipose tissue lipolysis. As fasting progresses, muscle proteolysis supplies glycogenic amino acids for heightened hepatic gluconeogenesis for a short period of time. After about three days of starvation, the metabolic profile is set to conserve protein and to supply greater quantities of alternate fuels. In particular, free fatty acids and ketone bodies are utilized to maintain energy needs. The ability of the kidney to conserve ketone bodies prevents the loss of large quantities of these valuable fuels in the urine. This delicate interplay among liver, muscle, kidney, and adipose tissue maintains blood fuel homeostasis and allows humans to survive caloric deprivation for extended periods.

Protein-sparing therapy during pneumococcal infection in rhesus monkeys

A model was developed in the rhesus monkey to determine if the marked wasting of body proteins associated with sepsis could be prevented by an intravenous supply of various nutritional substrates. All monkeys were given a basic infusion of 0.5 gm of amino acid nitrogen/kg body weight via an indwelling catheter in the jugular vein. Three groups were given diets with no added calories, 85 calories/kg from dextrose or 85 calories from lipid. In each group, six monkeys were inoculated with 3 x 10(8) Streptococcus pneumoniae and four with heatkilled organisms. In the monkeys infused with the amino acids alone, pneumococcal sepsis resulted in a fourfold increase in loss of body proteins compared with calorie-restricted controls. Addition of 85 calories/kg/day of either dextrose or lipid reduced body wasting associated with infectious disease. The calories from lipid were utilized bythe septic host as a source of energy, with a slightly reduced efficiency when compared with the isocaloric infusion of dextrose. The nitrogen sparing of the fat emulsion could not be accounted for by its glycerol content. Therefore, the septic monkey seemed to utilize fatty acids as an energy substrate. It appears that the carbohydrate calories tend to favor the synthesis of peripheral proteins (associated mainly with skeletal muscle), while lipid calories favor synthesis of visceral proteins such as plasma albumin and acute-phase proteins.

Protein-sparing in cystectomy patients

Forty-four patients undergoing radical cystectomy and urinary diversion for invasive bladder cancer were studied prospectively in order to evaluate the substitution of crystalline amino acids (A3W) for dextrose (D5W) in their postoperative fluid management. Nutritional assessment revealed 17 (39%) patients to be malnourished prior to operation; the postoperative complication rate in Group I (D5W) was 33% vs 17% in Group II (A3W). Nitrogen losses in both groups were low, secondary to the large amounts of albumin used postoperatively; however, more exogenous albumin was needed after operation to maintain serum albumin levels in Group I compared with Group II (77.5 +/- 3.1 gm vs 65 +/- 5.2gm). Cell-mediated immunity, determined by reactivity to a battery of recall antigens, revealed that 56% (5) of Group I patients were able to maintain their skin test reactivity throughout the postoperative course compared with 94% (17) in Group II. Four nutritionally depleted patients in Group I required conversion to a forced feeding regimen (IVH), while none of those in Group II required a change in nutritional regimen. Invasive bladder cancer represents a major injury, and preoperative x-ray therapy along with surgical extirpation is associated with considerable nutritional depletion. Early nutritional support in the management of these patients is mandatory, and where hypocaloric feeding regimens are appropriate, the use of A3W in place of D5W solutions would appear to be indicated.

The metabolic response to hypocaloric protein diets in obese man

Exogenous protein in the absence of other calories can cause protein-sparing, but the mechanisms involved are controversial. It has been postulated that low insulin and high fat-derived substrate levels are necessary and sufficient conditions for such protein-sparing. We therefore established such conditions with differing protocols of protein input to define the role of protein input in mediating the response. Three groups of obese, nondiabetic subjects received the following diets: (1) 82.5+/-1.0 g protein/day (400 cal/day) for 21 days, n = 7; (2) the same, but as a refeeding diet for 7 days after 21-28 days of total fasts, n = 7; and (3) commencing with the same input, but with daily stepwise decrements over 14 days to 19.4+/-2.2 g/day, then maintained an additional 7 days, n = 4. Diet 3 gave approximately the amount and pattern of protein lost during total fasting. The circulating hormone and substrate responses of diets 1 and 3 were comparable and resembled those of total fasts, in that plasma glucose and insulin fell and free fatty acids rose. Blood levels of alanine, pyruvate, and other glucogenic amino acids fell and blood levels of branched-chain amino acids rose transiently. Blood 3-hydroxybutyrate levels and urinary excretion were greater in diet 3 than diet 1, but less than in total fasting. Nitrogen balance in diet 1 was transiently negative, but in equilibrium from 12 to 21 days. In diet 3, it was constantly negative at -6 g/day, the values also observed at 21 days of fasting. Mean 3-methylhistidine excretion decreased by 170 mumol/day in diet 1 and 107 mumol/day in diet 3, reflecting decreased muscle protein catabolism. The refed, protein-depleted subjects, diet 2, showed an increase in plasma glucose without alteration in insulin levels. Free fatty acid and ketone body levels decreased to those of the steady state observed in diet 1. Glucogenic and branched-chain amino acids decreased transiently. Nitrogen balance became positive, and the low 3-methylhistidine excretion increased by 152 mumol/day. The differing responses of nitrogen balance could not be accounted for on the basis of levels of insulin or of fat-derived substrates. The primary determinants of the protein-sparing observed appeared to be the protein supply itself, and the magnitude of the decrease in endogenous protein catabolism. The positive balance on refeeding after prior depletion of protein stores was likely due to the exogenous supply, combined with decreased catabolism and considerably increased reutilization.

The influence of early post-operative intravenous nutrition upon recovery after total cystectomy

A retrospective review was made of the effect of early post-operative total parenteral nutrition on recovery from total cystectomy with formation of an ileal conduit. No difference in mortality or time spent in hospital after operation was noted between 2 groups receiving either total parenteral nutrition or isotonic dextrose-saline solutions.

Postoperative amino acid infusions: an appraisal

Amino acid infusions either as a 7 per cent solution or as an isotonic 3.5 per cent solution produce a nitrogen-sparing effect in the postoperative period. The nitrogen-sparing effect is independent of the concentration and rate of infusion of the amino acid solution; or of any changes in plasma substrate and hormone concentrations. These solutions have no advantage over conventional intravenous therapy with isotonic glucose and saline solutions and there is no indication for their routine use in the management of postoperative patients.

Protein and energy sparing of glucose added in hypocaloric amounts to peripheral infusions of amino acids

After abdominal surgery, patients were given peripheral infusions of amino acids alone for 4 days followed by amino acids plus glucose for 4 days, or the same solutions in the reverse order. Although there was a wide variation in the response of individual subjects, the typical effect of glucose under these conditions was to reduce both nitrogen excretion (average of 2.8 g N/day) and resting metabolic expenditure (average of 110 kcal/day).