Ascorbic acid dynamics in the seriously ill and injured

BACKGROUND

In addition to the known beneficial effects of ascorbic acid on wound healing and the immune response, it is also a potent extracellular antioxidant. Recent work in septic rats suggests that high-dose ascorbic acid total parenteral nutrition (TPN) supplementation may protect cells from free radical injury and improve survival. In this study, we determined ascorbic acid levels in the immediate post-injury/illness period and evaluated the ability of early short-term high levels of ascorbic acid in TPN to normalize plasma levels.

MATERIALS AND METHODS

Ascorbic acid levels were determined in 12 critically injured patients and 2 patients with severe surgical infections. Each patient received TPN supplemented with increasing doses of ascorbic acid over a 6-day period. Therapeutic responses were determined by plasma and urine measurements using high-pressure liquid chromatography.

RESULTS

The initial mean +/- SEM baseline plasma ascorbic acid concentration was depressed (0.11 +/- 0.03 mg/dl) and unresponsive following 2 days on 300 mg/day supplementation (0.14 +/- 0.03; P = 1.0) and only approached low normal plasma levels following 2 days on 1000 mg/day (0.32 +/- 0.08; P = 0.36). A significant increase was noted following 2 days on 3000 mg/day (1.2 +/- 0.03; P = 0.005).

CONCLUSION

We confirmed extremely low plasma levels of ascorbic acid following trauma and infection. Maximal early repletion of this vitamin requires rapid pool filling early in the post-injury period using supraphysiologic doses for 3 or more days.

Gastric emptying in trauma patients

BACKGROUND/AIM

The aim of this study was to obtain quantitative data on gastric emptying following trauma.

METHODS

In order to assess gastric emptying for early enteral feeding, we evaluated the absorption of an amino acid, L-[1-(13)C]phenylalanine, within 24 h of admission and 7 days later in 14 trauma patients (injury severity score 36 +/- 2). Following nasogastric administration of 100 mg L-[1-(13)C]phenylalanine, the plasma L-[1-(13)C]phenylalanine enrichment at 30 and 60 min and the expired (13)CO(2) for 1 h in the breath were used to measure the degree of gastric emptying.

RESULTS

The plasma L-[1-(13)C]phenylalanine enrichment concentration at 30 min was 0.53 +/- 0.23 mmol/l during the first study and 2.46 +/- 0. 62 mmol/l during the second study (p = 0.006, a fivefold increase). The L-[1-(13)C]phenylalanine plasma level in historic controls was 4. 57 +/- 1.48 mmol/l. The percent of the dose oxidized and expired as (13)CO(2) in 1 h was 0.51 +/- 0.17 during the first 24-hour study compared to the second study of 3.37 +/- 0.68 (p = 0.0008) 7 days later (an over sixfold increase). The percent of the dose oxidized in 1 h in 37 normal historic controls was 7.08 +/- 0.33.

CONCLUSION

These data indicate delayed gastric emptying with limited recovery in 1 week. We conclude that gastric feeding should not be employed, and the route for early nutritional intervention should be transpyloric for the trauma patient.

Effect of amino acid infusion on glucose production in trauma patients

The relationship between precursor supply and hepatic glucose output (HGO) was examined in 8 control subjects and 12 trauma patients after a fasting period of approximately 60 hours. Glucose kinetics were measured with a primed-constant infusion of [U-14C]glucose and [6-3H]glucose. The basal rate of HGO was 5.45 +/- 0.22 micromol x kg-1 x min-1 in the controls and 13.16 +/- 0.76 micromol x kg-1 x min-1 following trauma (p < 0.001). Four hours after amino acid infusion of 1.3 g x kg-1 x 24 h-1, HGO in the controls was unchanged at 5.35 +/- 0.22 micromol x kg-1 x min-1 but it had decreased to 11.71 +/- 0.67 micromol x kg-1 after trauma (p < 0.001). We conclude that increasing the supply of gluconeogenic precursors does not stimulate HGO in normal subjects after fasting or after severe trauma and that factors other than to availability of amino acids are responsible for the enhanced rate of HGO in trauma patients.

Impact of enteral feeding of a glutamine-supplemented formula on the hypoaminoacidemic response in trauma patients

Plasma amino acid concentrations were measured during fasting and after 3 days of enteral feeding in 16 trauma patients on a glutamine-supplemented diet and 14 patients on an isonitrogenous control diet. During fasting, total amino acids, including glutamine, were depressed by 50% and this was attributed to a reduction in both essential and nonessential amino acids. The essential amino acid concentrations increased in both groups after feeding. The nonessential amino acid concentrations also increased in the control group but not in the glutamine group during feeding. Repletion of the glutamine extracellular pool was not evident after an average intake of 27.1 g per day of glutamine for 3 days. Nitrogen balance was similar for the two groups during feeding. We conclude that in this study, enteral glutamine did not increase the glutamine plasma concentration. In addition, both formulas improved the hypoaminoacidemia of essential amino acids but only the control diet improved the nonessential amino acids plasma concentration.

Glutamine supplementation of enteral nutrition: impact on whole body protein kinetics and glucose metabolism in critically ill patients

BACKGROUND

Glutamine-supplemented parenteral nutrition has been reported to attenuate the early postoperative reduction in intracellular glutamine and improve protein synthesis and nitrogen balance. We investigated the effect of an enteral formula or protein and glucose kinetics and nitrogen balance in trauma patients.

METHODS

The enteral formula (AlitraQ) provided a mean intake of 0.35 g of glutamine/kg body weight per day to 16 trauma patients and was compared with an isonitrogenous formula that provided a mean of 0.05 g of glutamine/kg body weight per day in 14 trauma patients. After 3 days of feeding, protein kinetics were measured using a 4-hour prime-continuous infusion of L-[1-13C]leucine. Glucose kinetics were measured during the same time interval using prime-continuous infusion of [U-14C]- and [6-3H]glucose.

RESULTS

Nitrogen balance was not significantly different in the two groups. There were no significant differences in protein turnover, synthesis, and breakdown between the two groups. There were no significant differences in glucose turnover, oxidation, recycling, and percent of VCO2 from glucose oxidation between the two groups.

CONCLUSIONS

Glutamine-enriched enteral formulas are well tolerated by the severely injured patient but provide no additional nutritional advantage compared with standard enteral formulas during the first 3 days of feeding immediately after trauma.

Protein and energy balance following femoral neck fracture in geriatric patients

To elucidate the effect of total peripheral parenteral nutrition (TPPN) on protein kinetics following injury, we compared the whole-body leucine kinetic response using a primed-constant infusion of L-[1-14C]leucine in 33 elderly patients (aged 82 +/- 1.0 years) following hip fracture and 33 healthy elderly control subjects (aged 75 +/- 0.7 years). Following a 36-hour fast, leucine release from protein breakdown was 1.2 +/- 0.10 mumol.kg-1.min-1 and leucine incorporation into protein was 0.94 +/- 0.095 mumol.kg-1.min-1 in control subjects, and in injured subjects leucine release from protein breakdown was 1.3 +/- 0.14 mumol.kg-1.min-1 and leucine incorporation into protein was 0.97 +/- 0.092 mumol.kg-1.min-1. Control and injured subjects were then administered TPPN (protein, 1.5 g amino acids.kg-1; carbohydrate, 10.0 kcal.kg-1; lipid, 15.0 kcal.kg-1) for 24 hours, and leucine kinetics were redetermined. Compared with protein kinetics in the fasting state, leucine release from protein decreased to 1.0 +/- 0.14 mumol.kg-1.min-1 and leucine incorporation into protein increased to 1.16 +/- 0.097 mumol.kg-1.min-1 in control subjects. Injured patients also responded to TPPN with a decrease in leucine release from protein breakdown (1.12 +/- 0.156 mumol.kg-1.min-1) and an increase in leucine incorporation into protein (1.29 +/- 0.164 mumol.kg-1.min-1). These results indicate that in a geriatric population, whole-body leucine kinetics following hip fracture and the anabolic response to TPPN are not significantly altered from those of uninjured subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose metabolism in advanced lung cancer patients

Although it is generally accepted that altered nutrient intake and metabolism are responsible for the progressive loss of body weight observed in most advanced cancer patients, there is still considerable controversy regarding the contributory role of changes in both resting energy expenditure (REE) and glucose metabolism. Several studies suggest increases in both REE and glucose appearance in advanced cancer patients compared with healthy control subjects, whereas others revealed no changes in either metabolic parameter. We measured REE with indirect calorimetry and glucose kinetics with a primed constant infusion of D-[U-14C]glucose and D-[6-3H]glucose over the last 4 h of a 24-h fast in 32 advanced lung cancer patients immediately after diagnosis and before any chemotherapy or radiotherapy and in 19 healthy volunteer subjects. REE for the lung cancer group was not significantly different from that in the control group (1535.8 +/- 78.0 vs. 1670.2 +/- 53.9 kcal/day, respectively, p = 0.151). When REE was expressed as a function of body weight, or lean body mass, no differences between the two groups were observed. The rate of glucose appearance was 9.88 +/- 0.36 mumol.kg-1.min-1 in the cancer patients and 10.15 +/- 0.53 mumol.kg-1.min-1 in control subjects (p = 0.667), of which 50.4 versus 58.2%, respectively, was oxidized. The amount of glucose recycled was 13.54 +/- 1.22% in cancer patients and 15.08 +/- 0.99% in control subjects (p = 0.394). The amount of VCO2 from direct oxidation of glucose was 23.39 +/- 0.74% in cancer patients and 27.45 +/- 1.36% in control subjects (p = 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma amino acid concentrations in geriatric control and hip-fracture patients

Changes in plasma amino acids, 24-h nitrogen balances, and resting metabolic expenditures (RMEs) were measured in 10 geriatric patients (aged 70-92 y) with hip fracture 1 d after surgical fixation during both a 24-h fasting state and while receiving total peripheral parenteral nutrition (TPPN) for 24 h at 1.5 g amino acids.kg-1.d-1 and 29-30 kcal.kg-1.d-1 and compared with 19 healthy volunteer subjects (aged 70-84 y). RME and 24-h urinary nitrogen losses were also elevated in the trauma patients during both fasting and TPPN. Positive nitrogen balances were evident in both groups during TPPN. Plasma total amino acid concentration was significantly lower in the trauma patients because of lower plasma concentrations of the nonessential amino acids. Phenylalanine and methionine concentrations were significantly higher and lysine lower in the trauma group. In addition, evaluation of the essential amino acid ratios after fasting and TPPN reveal that there are no limiting amino acids during TPPN.

Comparison of three methods for the estimation of total nitrogen losses in hospitalized patients

Since the measurement of total nitrogen output (TNO) is not routinely determined in the clinical setting, its level is frequently estimated using formulas based on the urinary urea nitrogen excretion (UUN). We measured TNO in 124 surgical patients over 990 days (TNO, 19.22 +/- 8.72 g N/day; total urinary nitrogen (TUN) 18.17 +/- 8.70 g N/day; UUN, 15.17 +/- 7.70 g N/day; mean gastrointestinal nitrogen (MGIN) 0.68 +/- 0.49 g N/day; integumental nitrogen (ITGN), 0.34 +/- 0.08 g N/day) and compared the results with the daily estimations using three different formulas: formula A, UUN + 4; formula B, UUN x 1.20 + 1.05, where 1.20 is the reciprocal of the mean ratio UUN/TUN and 1.05 the mean extraurinary nitrogen losses; and formula C, UUN x 1.0986 + 2.55, derived from the regression analysis of UUN vs TNO. TNO estimated by these formulas were 19.17 +/- 7.70, 19.26 +/- 9.24, and 19.22 +/- 8.70 g N/day, respectively. The regression analyses of the estimated TNO from the three formulas versus the measured TNO indicated that formulas A, B and C were equally accurate in estimating TNO over the entire range of UUN. However, when only values of UUN greater than or equal to 30 g N were considered, a modified formula A (UUN + 6) was the best predictor of TNO. Daily audits of the differences between the estimated and measured TNO showed comparable results for the three formulas. In 28.4 to 31.1% of the observed days the differences were higher than +/- 2 g N/day, an error which is not acceptable when estimating the protein requirements in many clinical conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

A physiologic basis for the provision of fuel mixtures in normal and stressed patients

It has been suggested that lipid is a preferred fuel in stressed patients. We evaluated glucose oxidation in 20 patients (sepsis, cancer of the colon, multiple trauma, controls) while they received TPN (5.65 mg glucose/kg/min). Respiratory quotient (RQ) was measured by indirect calorimetry and the percent VCO2 arising from the oxidation of glucose was measured using [U-14C] glucose. Since RQs were 1.0 or greater in all patients, the nonprotein energy utilized by them was calculated to be derived completely from glucose. However, the kinetic data showed that glucose contributed only 55-60% of the VCO2. Protein oxidation contributed less than 20% of the VCO2, as calculated from urinary nitrogen. The difference must have been derived from fatty acid oxidation. The glucose turnover that was not oxidized was presumed to be converted to lipid at an RQ of 8.6. The net oxygen consumption and carbon dioxide production from this overall distribution resulted in an RQ of about 1.0 with only 60% coming from glucose oxidation. Since all patients responded in the same manner, it appears that the proper ratio of glucose and lipid was dictated on a physiologic basis and not on the type of disease.

Catabolic effect of dexamethasone in patients with major head injuries

In the records of our extensive metabolic studies on trauma victims, we found 16 head injured patients who had no other major injuries. Among them, nine had been given dexamethasone for at least 6 days. The other seven had not received any corticosteroids. There was no significant difference in the Glasgow Coma Scales of the treated and untreated groups. Metabolic balance studies were carried out for at least 3 days, including the periods when the treated patients were receiving dexamethasone. Mean nitrogen balance was -0.296 +/- 0.03 g/kg/day for the treated group and -0.182 +/- 0.03 g/kg/day for the untreated group. This difference was significant (p = 0.02, t-test). Our metabolic data are also consistent with those of other published studies, which used other corticosteroids and somewhat different methodologies. Thus, it is clearly established that corticosteroids cause significant degrees of catabolism in head injured patients, beyond what would "normally" be expected in such patients if they did not receive these drugs.

Validity of 3-methylhistidine excretion as an indicator of skeletal muscle protein breakdown in humans

The urinary excretion of 3-methylhistidine (3MEH) in humans and animals has been used as a biologic marker for skeletal muscle protein breakdown. In rats, it has been recently suggested that there is a significant contribution of 3MEH in urine from the gastrointestinal tract due to the rapid turnover of protein in that tissue. To evaluate this point in humans, six patients with short bowel were evaluated. They were placed on three-day meat-free diets while 24-hour urine collections were obtained. The mean +/- SEM 3MEH in the short-bowel group was 3.27 +/- 0.34 mumol/kg/d and the mean +/- SEM molar ratio of 3MEH to creatinine was 0.0212 +/- 0.0012. These data were not significantly different from the control group at 95% confidence level. The results suggest that the contribution of the small intestine appears to be negligible, therefore urinary 3MEH should continue to be a valid index of skeletal muscle breakdown in man.

Urinary excretion of 3-methylhistidine: an assessment of muscle protein catabolism in adult normal subjects and during malnutrition, sepsis, and skeletal trauma

The urinary excretion of 3-methylhistidine (3 MEH) has been shown to be a reliable index of muscle protein breakdown. It is decreased in protein-calorie malnutrition and increased during the hypercatabolic phase of sepsis and thermal trauma. Losses of 3 MEH after moderate to severe skeletal trauma in man and animals are reported as increased or unchanged. To clarify this response, 24 male and 6 female skeletal trauma patients were evaluated for 24 hr urinary losses of 3 MEH, nitrogen and creatinine. Eight of the 24 males also received a catabolic steroid for treatment of a head injury. In addition, 3 male and 1 female septic patients were similarly evaluated. Controls consisted of 10 volunteers on a meat free diet for 4 days and of 8 volunteers who were given only intravenous 5% dextrose in water for 3 days. The 3 MEH excretion for all control males was 3.6 mumole/Kg/day and for females was 2.8 Skeletal trauma produced a 280% increase for the males and a 225% increase for the females. Trauma with steroids caused a 325% increase. Sepsis induced a 227% increase in 3 MEH losses for males and 292% for females during the febrile episode. Creatinine excretion also increased significantly in response to trauma and sepsis but the magnitude of the increase was less than for 3 MEH. This was reflected in the 3 MEH to creatinine molar ratio increase from 0.018 for controls to 0.030-0.040 in sepsis and trauma. Patients with extensive body weight loss showed decreases in 3 MEH and creatinine excretion and a molar ratio similar to controls. The calculated contribution of muscle protein to whole body protein breakdown in the trauma and septic groups showed a twofold increase compared to the control group. The data indicate that the increased muscle protein catabolic response following stress of skeletal trauma and sepsis provides an insight on the origin of the large urinary nitrogen losses following such insults.

A comparison of the effects of skeletal trauma and surgery on the ketosis of starvation in man

The increase of plasma ketone bodies (acetoacetic acid and beta-hydroxybutyric acid) is related to the efficient protein-sparing adaptation during a total fast by healthy man. This study investigated the response to a total fast during the postinjury state. Twenty patients with skeletal or soft-tissue trauma received 3 days of carbohydrate-free intake and then 3 more days of carbohydrate intake. Control subjects were ten postoperative patients and two healthy volunteers who received similar nutritional treatment. The trauma patients lost nearly 20 gm of nitrogen/day, which was twice control, and had a resting energy expenditure of 27.07 kcal/kg, 21.4% greater than controls. Trauma was found related to an elevation in plasma glucose and to inhibit the rise in plasma ketone bodies and free fatty acids. In contrast, indirect calorimetry showed that fat contributed 63% of the nonprotein energy on the third day of fasting and injury. These data indicate that fat is utilized by the trauma patient but that fatty metabolism is abnormal compared to starvation in healthy or mildly stressed patients.

Contribution of skeletal muscle protein in elevated rates of whole body protein catabolism in trauma patients

Whole body protein breakdown using 15N and skeletal muscle protein breakdown from urinary 3-methylhistidine were measured simultaneously in seven skeletal trauma and eight normal subjects on a standard hypocaloric, protein free diet. The trauma group had a 31% greater resting metabolic energy expenditure than controls. The control males lost 3.73 mumol/kg/day of 3-methylhistidine which suggested a protein breakdown rate of 0.89 g P/kg/day. The control females lost 2.46 mumol/kg/day of 3-methylhistidine or a breakdown rate of 0.58 g P/kg/day. These parameters were 187% greater for males and 163% greater for females in the trauma group. The measured whole body protein breakdown rates were 3.64 g P/kg/day for the control males and 2.69 for females. Skeletal trauma increased both by 73%. Skeletal trauma raised the muscle contribution to the whole body breakdown rate from 24.4 to 40.4% for men and from 21.6 to 33.0% for women. This disproportionate increase in muscle protein breakdown is consistent with muscle protein metabolism being most seriously affected by severe injury.

Effects of major skeletal trauma on whole body protein turnover in man measured by L-[1,14C]-leucine

Skeletal trauma induces excessive urinary nitrogen losses and is thought to stimulate the oxidation of the branched chain amino acids. This study was undertaken to quantitate whole body protein turnover rates and leucine metabolism during the peak nitrogen loss period following skeletal trauma. Quantitation was done in eight healthy and six trauma subjects, who received D5W as their only nutrition for 72 hours, using a 10-hour continuous infusion of L-[1,14C]-Leucine. The controls lost an average of 6 gm of nitrogen/day and the trauma patients 25 gm of nitrogen/day on the study day. Trauma was shown to elevate plasma leucine by 76%, increase the leucine flux through the free leucine pool by 86%, and accelerate leucine oxidation by 277% over the values for controls. Trauma also produced a 50% increase in whole body protein synthesis and a 79% increase in protein breakdown. The data clearly define significant increases in both the protein synthetic and catabolic rates in trauma with a greater increase occurring in catabolism. This is similar to findings for protein turnover in sepsis and burn injury, but is different from that found in elective surgery. A striking aspect of our data is the indication that women do not exhibit the same response to injury that men do. This suggestion, however, is based on a small sample.

Metabolic response to injury and illness: estimation of energy and protein needs from indirect calorimetry and nitrogen balance

The metabolic response to injury and illness as manifested by increases in energy expenditure and nitrogen losses makes it difficult for the clinician to evaluate calorie and protein needs. A method for determining daily calorie needs in hospitalized patients is presented. Average increases in resting metabolic expenditure for a group of patients following elective operation, skeletal trauma, skeletal trauma with head injury, blunt trauma, sepsis and burns were determined by indirect calorimetry and protein need by urinary nitrogen losses over extended time periods. Total daily calorie needs were then calculated, using the Harris-Benedict equation and adjusting this value upward using a previously measured activity and injury factor to arrive at the daily needs. Protein requirements may be determined on periodic 24 hour urine samples analyzed for the urinary urea nitrogen and adjusting this to a total nitrogen or protein equivalent. This approach to estimating the calorie nitrogen needs of the hospitalized patient under various degrees of stress more closely approximates the patient's variable needs at the height of the catabolic response and during convalescence.

Metabolic response to injury and illness: estimation of energy and protein needs from indirect calorimetry and nitrogen balance

The metabolic response to injury and illness as manifested by increases in energy expenditure and nitrogen losses makes it difficult for the clinician to evaluate calorie and protein needs. A method for determining daily calorie needs in hospitalized patients is presented. Average increases in resting metabolic expenditure for a group of patients following elective operation, skeletal trauma, skeletal trauma with head injury, blunt trauma, sepsis and burns were determined by indirect calorimetry and protein need by urinary nitrogen losses over extended time periods. Total daily calorie needs were then calculated, using the Harris-Benedict equation and adjusting this value upward using a previously measured activity and injury factor to arrive at the daily needs. Protein requirements may be determined on periodic 24 hour urine samples analyzed for the urinary urea nitrogen and adjusting this to a total nitrogen or protein equivalent. This approach to estimating the calorie nitrogen needs of the hospitalized patient under various degrees of stress more closely approximates the patient's variable needs at the height of the catabolic response and during convalescence.

Body composition changes in the critically ill patient: emphasis on water balance

The moisture contents of foods, fluids, and parenteral solutions taken in and of all samples excreted, the water of oxidation of fuel mixtures burned, and the evaporative water loss must be determined in order to obtain a quantitative picture of water balance. Because there is a tendency to retain water after trauma, surgery, or an acute illness, changes in the water compartment of the body may lead to changes in body weight that may be considered erroneously as changes in energy or protein stores. Measurement of water balance, in addition to calorie and nitrogen balance is one of the most accurate means of accounting for these changes in body composition. Fluid and electrolyte therapy and nutritional supplementation can be tailored to meet the patient's specific needs by utilizing this information. Application of these principles to the care of hospitalized patients outside of the research setting will be discussed.

Gluconeogenic response during glucose infusions in patients following skeletal trauma or during sepsis

In order to quantitate the effect of sepsis and skeletal trauma on gluconeogenesis, four septic and five skeletal trauma patients were evaluated for their ability to convert 14C-L-alanine to 14C-glucose while receiving 5% dextrose by peripheral vein. In the septic group, the mean glucose pool size increased by 35% and the glucose turnover rate increased by 85% over normal. The alanine conversion averaged 11.1% of the dose. The skeletal trauma group showed a glucose pool size increase of 61%, a 100% increase in glucose turnover rate and a 11.7% conversion of the alanine dose to glucose. The increased conversion of 14C-alanine to 14C-glucose in both sepsis and skeletal trauma in the face of an exogenous glucose infusion indicates an abnormal unsuppressible response. Each of the above parameters when compared to normal values was found to be significant at levels greater than 97.5%. The percentages of the dose expired as 14CO2 in three hours were not significantly different from the normals.

Muscle protein catabolism in the septic patient as measured by 3-methylhistidine excretion

Muscle protein catabolism has been evaluated using the excretion of urinary 3-methylhistidine (3-MEH) is six normal male and six normal female subjects and in four surgical patients, two of whom developed febrile episodes during the course of their study. In addition, their nutritional status was also evaluated using percentage body weight losses before hospital admittance, creatinine-height ratios, and, in two patients, serum alkaline ribonuclease levels. The results indicate that: 1) prolonged starvation may produced decreased 3-MEH excretion because of an adaptive diminution of muscle breakdown in sustained starvation, decreased 3-MEH excretion also may simply reflect diminished lean body mass, 3-MEH excretion may be increased above basal levels because of superimposed stresses such as fever, and the acute phases of starvation produce increased levels of 3-MEH excretion until adaptive mechanisms occur; 2) creatinine-height ratios are low in starvation, and increase not only with improved nutrition but in response to fever and stress of operation, even when these are superimposed on malnutrition; and 3) alkaline RNAase levels are elevated in malnutrition and decrease with improved nutrition but in response to fever and stress of operation, even when these are superimposed on malnutrition; and 3) alkaline RNAase levels are elevated in malnutrition and decrease with improved nutrition. The enzyme may also be elevated by the stress of operations.

Parenteral nutrition in the septic patient: nitrogen balance, limiting plasma amino acids, and calorie to nitrogen ratios

A series of eight septic patients was provided varying levels of beef fibrin protein hydrolysate by central vein in the presence of adequate calories for evaluation of nitrogen retention under septic conditions. The mean nitrogen intake to achieve nitrogen equilibrium was 240 mg/kg of body wt per day. This represents a 40% increase over that required to produce nitrogen equilibrium in normal adults. The mean caloric intake of these patients was 43.3 kcal/kg of body wt per day. The calorie to nitrogen ratio based on the above intake was calculated to be 180:1. In order to utilize effectively calorie to nitrogen ratios in the nutritional care of patients, it is suggested that ratios be standardized using daily total coloric expenditures. Correcting the mean measured resting calorie expenditures of these patients for minimal daily activity, a caloric to nitrogen ratio of 138:1 was obtained. The plasma amino acid ratios in these septic patients confirm the finding that valine and phenylalnine are limiting amino acids in a beef fibrin hydrolysate at infusion levels below 240 mg of N/kg of body wt per day. Analysis of the urinary excretion of total nitrogen, urea, and amino acids in two patients suggests that 30 to 50% of the infused peptides of a beef fibrin hydrolysate are lost in the urine in these septic patients.

Nonsuppressability of gluconeogenesis by glucose in septic patients

The contribution of alanine to the synthesis of glucose and the oxidation of alanine was evaluated in normal and septic patients using (14C)L-alanine. The data indicate that there is a twofold increase in the conversion of alanine into glucose in sepsis and, further, this increase was observed while the patients were receiving a constant glucose infusion (100 mg/min) prior to and during the single injection of (14C)L-alanine. Failure of glucose to decrease this gluconeogenic response in these septic patients clearly indicates that the controlling mechanism for glucose synthesis is modified following injury and undoubtedly plays a role in the abnormal carbohydrate metabolism observed in injury. The contribution of alanine carbon to oxidation was the same in the control and septic group as measured by the per cent of the (14C)L-alanine dose expired in 3 h. Since the control subjects received glucose continuously during the study with and without amino acids, it is clear that nutritional intake and injury has minimal effect on the oxidation of alanine. This suggests that transamination is not affected by sepsis nor is there an inhibition of pyruvate oxidation following sepsis.

Metabolism of 3-methylhistidine in man

The metabolism of L-3-methylhistidine was studied in man using intravenously administered ((14)C)3-methylhistidine. Analysis for expired (14)CO2 for periods up to 2 hr following a single intravenous injection revealed no radioactivity, indicating that this compound is not oxidized in man. Analysis of urine samples for total radioactivity showed that 75% of the administered dose was excreted in 24 hr and 95% in 48 hr. Ion-exchange chromatography of urine samples with monitoring of the column eluated by a flow liquid-scintillation technique showed the presence of only two radioactive peaks. The time taken to elute these peaks was compatible with the major excretory component (95.5%) being ((14)C)3-methylhistidine, accompanied by a small amount (4.5%) in the form of N-acetyl-((14)C)3-methylhistidine. The plasma disappearance curves of ((14)C)3-methylhistidine suggested a half-life of approximately 130 min. The inability ot oxidize 3-methylhistidine and its quantitative excretion as the original compound as well as its N-acetyl derivative is similar to its metabolic fate in the rat and therefore suggests that 3-methylhistidine excretion may provide a reliable measure of actin and myosin turnover in the whole animal or in human subjects.