Metabolism of intravenous fat emulsion in the surgical newborn

Metabolism and energy prescription in critically III children

Optimal nutrition therapy can positively influence clinical outcomes in critically ill children. Accurate assessment of nutritional status, metabolic state, macronutrient requirements and substrate utilization allows accurate prescription of nutrition in this population. In response to stress and injury, the body undergoes adaptive physiologic changes leading to dysregulation of the inflammatory response and hyperactivation of the inflammatory cascade. This results in a global catabolic state with modification in oxygen consumption and macronutrient metabolism. A comprehensive understanding of the metabolic response is essential when prescribing nutritional interventions aimed to offset the burden of this adaptive stress response in the critically ill. In this narrative review we aim to provide a comprehensive review of the physiologic basis, recent literature and some emerging concepts related to energy expenditure and the practical aspects of energy delivery in the critically ill child. Based on the unique metabolic characteristics of the critically ill child, we aim to provide a pragmatic approach to providing nutrition therapy.

Understanding triglyceride levels related to intravenous fat administration

Lipid is an essential macronutrient in parenteral nutrition (PN) support. intravenous (IV) lipid provides essential fatty acids and a concentrated calorie source. Preterm infants are at risk for essential fatty deficiency early in life. Lipid administration is associated with some risks, and there are guidelines for administration to minimize complications. Lipid emulsions in the United States are derived from soybean oil. Outside of the United States, lipid emulsions made from fish oil or combinations of fish, soybean, olive, and medium-chain triglycerides (MCTs) are under investigation for improved tolerance, lower plasma lipid levels, and improved fatty acid profiles, all of which are considered beneficial. Triglyceride levels are an important measurement to assess patient tolerance.

Manganese in human parenteral nutrition: considerations for toxicity and biomonitoring

The iatrogenic risks associated with excessive Mn administration in parenteral nutrition (PN) patients are well documented. Hypermanganesemia and neurotoxicity are associated with the duration of Mn supplementation, Mn dosage, as well as pathological conditions, such as anemia or cholestasis. Recent PN guidelines recommend the biomonitoring of patients if they receive Mn in their PN longer than 30 days. The data in the literature are conflicting about the method for assessing Mn stores in humans as a definitive biomarker of Mn exposure or induced-neurotoxicity has yet to be identified. The biomonitoring of Mn relies on the analysis of whole blood Mn (WB Mn) levels, which are highly variable among human population and are not strictly correlated with Mn-induced neurotoxicity. Alterations in dopaminergic (DAergic) and catecholaminergic metabolism have been studied as predictive biomarkers of Mn-induced neurotoxicity. Given these limitations, this review addresses various approaches for biomonitoring Mn exposure and neurotoxic risk.

Neonatology/Paediatrics - Guidelines on Parenteral Nutrition, Chapter 13

There are special challenges in implementing parenteral nutrition (PN) in paediatric patients, which arises from the wide range of patients, ranging from extremely premature infants up to teenagers weighing up to and over 100 kg, and their varying substrate requirements. Age and maturity-related changes of the metabolism and fluid and nutrient requirements must be taken into consideration along with the clinical situation during which PN is applied. The indication, the procedure as well as the intake of fluid and substrates are very different to that known in PN-practice in adult patients, e.g. the fluid, nutrient and energy needs of premature infants and newborns per kg body weight are markedly higher than of older paediatric and adult patients. Premature infants <35 weeks of pregnancy and most sick term infants usually require full or partial PN. In neonates the actual amount of PN administered must be calculated (not estimated). Enteral nutrition should be gradually introduced and should replace PN as quickly as possible in order to minimise any side-effects from exposure to PN. Inadequate substrate intake in early infancy can cause long-term detrimental effects in terms of metabolic programming of the risk of illness in later life. If energy and nutrient demands in children and adolescents cannot be met through enteral nutrition, partial or total PN should be considered within 7 days or less depending on the nutritional state and clinical conditions.

Initial nutritional management of the preterm infant

Postnatal nutrition has a large impact on long-term outcome of preterm infants. Evidence is accumulating showing even a relationship between nutrient supply in the first week of life and later cognitive development in extremely low birth weight infants. Since enteral nutrition is often not tolerated following birth, parenteral nutrition is necessary. Yet, optimal parenteral intakes of both energy and amino acids are not well established. Subsequently, many preterm infants fail to grow well, with long-term consequences. Early and high dose amino acid administration has been shown to be effective and safe in very low birth weight infants, but the effect of additional lipid administration needs to be defined.

Metabolism and nutrition in the surgical neonate

Considerable improvements have been achieved in pediatric surgery during the last two decades: the mortality rate of neonates undergoing major operations has declined to less than 10%, and the morbidity of major operations has become negligible. This considerable improvement can be partly ascribed to a better understanding of the physiological changes that occur after an operation and to more appropriate management and nutrition of the critically ill and "stressed" neonates and children. The metabolic response to an operation is different in neonates from adults: there is a small increase in oxygen consumption and resting energy expenditure immediately after surgery with return to normal by 12-24 hours. The increase in resting energy expenditure is significantly greater in infants having a major operation than in those having a minor procedure. The limited increase in energy expenditure may be due to diversion of energy from growth to tissue repair. During parenteral nutrition, it is not advisable to administer more than 18 g/kg/day of carbohydrate because this intake will be associated with lipogenesis, increased CO(2) production, and increased free radical-mediated lipid peroxide formation. Glutamine intake is potentially beneficial during total parenteral nutrition, although a large, randomized, controlled trial in surgical neonates requiring parenteral nutrition is needed to provide evidence for its benefit.

Effects of low fat and babassu fat diets on nutritional status in obstructive cholestasis in young rats

PURPOSE: To test the effects of a low fat diet compared with a babassu fat diet on nutritional status in obstructive cholestasis in young rats. METHODS: We submitted 40 rats in 4 groups of 10 animals each from P21 (21st postnatal day) to P49 to two of the following treatments: bile duct ligation or sham operation and low fat diet (corn oil supplying 4.5% of the total amount of energy) or babassu fat diet (this fat supplying 32.7% and corn oil supplying 1.7% of the total amount of energy). Weight gain from P25 to P49 every 4 days was measured. The Verhulst's growth function was fitted to these values of weight gain. Growth velocity and acceleration at each moment were estimated using the same equation. Total food and energy intake from P21 to P49, energy utilization rate (EUR) from P25 to P49 and fat absorption rate (FAR) and nitrogen balance (NB) from P42 to P49 were measured. Two Way ANOVA and the S.N.K. test for multiple paired comparisons were employed to study the effects of cholestasis and those of the diets and their interaction (p<0.05) on those variables. RESULTS: In cholestatic animals, a higher growth velocity at P45, a higher growth acceleration at P41 and P45, a greater EUR, a greater FAR and a greater NB, were found with the low fat diet as compared with the babassu fat diet. CONCLUSION: A low fat diet lessens the growth restriction brought about by cholestasis and allows for an improved dietary energy utilization and a better protein balance than the babassu fat diet.

Impaired energy metabolism during neonatal sepsis: the effects of glutamine

Neonatal sepsis is an important cause of morbidity and mortality as a result of multiple organ system failure, particularly in neonates requiring total parenteral nutrition. Suitable therapies and support are needed both to prevent sepsis and to prevent multiple organ failure. After bacterial infection, pro-inflammatory cytokines trigger the antimicrobial activity of macrophages and neutrophils, resulting in production of reactive species such as H2O2, NO, superoxide and peroxynitrite. However, excess production can lead to host tissue damage. Incubation of either hepatocytes or heart mitochondria from neonatal rats with these reactive species, or with cytokines, leads to impairment of mitochondrial oxidative function, and in an animal model of neonatal sepsis similar results to thein vitrofindings have been demonstrated. Recentin vivostudies, using indirect calorimetry of suckling rat pups, show that during endotoxaemia there is a profound hypometabolism, associated with hypothermia. Having determined that cellular oxidative function may be impaired during sepsis, it is of great importance to try to identify therapeutic measures. Much interest has been shown in glutamine, which may become essential during sepsis. It has been shown that hepatic glutamine is rapidly depleted during endotoxaemia. When hepatocytes from endotoxaemic rats were incubated with glutamine, there was a restoration of mitochondrial structure and metabolism.In vivo, intraperitoneal injection of glutamine into endotoxic suckling rats partially reversed hypometabolism, markedly reduced the incidence of hypothermia and improved clinical status. These results suggest that glutamine has a beneficial effect during sepsis in neonates.

Oxidation of intravenous lipid in infants and children with systemic inflammatory response syndrome and sepsis

During sepsis in adults, fat becomes a preferred fuel; however, oxidation may be impaired relative to the circulating fatty acid levels. Little is known about the ability of infants and children to oxidize lipids during systemic inflammation (SIRS) and sepsis. The aim of this study was to examine the oxidation of exogenous lipid in these patients. Sixteen patients with SIRS/sepsis and eight controls with no evidence of sepsis were studied by indirect calorimetry during an i.v. lipid utilization test (1 h of 0.3 g/kg/h glucose followed by 3 h of 0.1 g/kg/h glucose plus 0.15 g/kg/h lipid). The respiratory quotient (RQ) (1.0 for carbohydrate utilization and 0.7 for fat utilization) was measured. Results were compared by repeated-measures analysis of variance (ANOVA), paired or unpaired t tests. There was no difference in baseline RQ between controls and patients with SIRS/sepsis (mean +/- SD; 0.82 +/- 0.08 versus 0.82 +/- 0.04). The RQ of controls dropped significantly to 0.78 +/- 0.08 at 240 min (p < 0.001). The RQ of patients with SIRS/sepsis also fell to 0.78 +/- 0.06 (p < 0.01). Infants and children with SIRS/sepsis are able to oxidize i.v. lipid.

The metabolic response to intravenous medium-chain triglycerides in infants after surgery

OBJECTIVE

The aim of this study was to determine if administration of mixed medium-chain triglycerides (MCT)/long chain triglycerides (LCT) fat emulsion would increase net fat oxidation and if carbohydrate intake would influence net fat oxidation.

STUDY DESIGN

Stable infants receiving total parenteral nutrition were studied after surgery. Respiratory gas exchange was measured by indirect calorimetry and urinary nitrogen excretion by the micro-Kjeldahl method. Intravenous fat (4 g/kg/day) was given as either pure LCT fat emulsion or 50/50 MCT/LCT fat emulsion. Carbohydrate intake was either "high" (15 g/kg/day) or "low" (10 g/kg/day). Four groups of patients were studied: group 1 = LCT and high-carbohydrate; group 2 = LCT and low-carbohydrate; group 3 = MCT/LCT and high-carbohydrate; group 4 = MCT/LCT and low-carbohydrate.

RESULTS

At a carbohydrate intake of 15 g/kg/day, the calories available from glucose exceeded the measured resting energy expenditure (REE), and no differences were seen in either energy expenditure or net fat oxidation between patients receiving LCT and MCT/LCT fat emulsions. However, at a carbohydrate intake of 10 g/kg/day, when glucose calories were less than REE, net fat oxidation was significantly higher in patients receiving MCT/LCT (median, 1.94; range, 1.05-2.24 g/kg/day) compared with patients receiving LCT (median, 0.60; range, -0.09 to 1.35; P =.03).

CONCLUSION

Providing that carbohydrate calories do not exceed REE, partial replacement of LCT by MCT in intravenous fat emulsions can increase net fat oxidation in infants after surgery.

Metabolism and nutritional support in the surgical neonate

Various factors can influence the metabolism of surgical neonates. These include prematurity, operative stress, critical illness, and sepsis. The nutritional management of surgical infants with congenital or acquired intestinal abnormalities has improved after the introduction of parenteral nutrition. This article is focused on the energy and protein metabolism of surgical neonates with particular reference to the metabolic response to operative trauma and sepsis. The metabolic utilization of intravenous nutrients also is discussed. The metabolic response to operative trauma is different between neonates and adults. Infants have high rates of protein turnover and are avid retainers of nitrogen. Energy expenditure increases only transiently (4 to 6 hours) after major surgery in neonates. Protein turnover and catabolism seems not to be affected by major operative procedures in neonates. In neonates on parenteral nutrition, carbohydrate and fat have an equivalent effect on protein metabolism. The main determinants of fat utilization are carbohydrate intake and resting energy expenditure. Parenteral nutrition in surgical neonates is associated with increased production of oxygen-free radicals. This seems to be related to intravenous fat administration. Promoting fat utilization by reducing the carbohydrate to fat ratio in the intravenous diet reduces free radical activity to a similar extent as fat exclusion. Glutamine appears to be safe for use in neonates and infants and is "conditionally essential" in very-low birth weight infants and in septic neonates. Enteral glutamine supplementation in very-low birth weight infants reduces the risk of sepsis. The metabolism of surgical neonates is affected by operative trauma, critical illness, and sepsis. Nutritional support in surgical neonates has a profound impact on outcome. Exogenous glutamine can modulate immune, metabolic, and inflammatory responses. Further investigations are needed to clarify the clinical benefit of parenteral or enteral glutamine administration in surgical neonates.

Energy metabolism, nitrogen balance, and substrate utilization in critically ill children

BACKGROUND

Critically ill patients are characterized by a hypermetabolic state, a catabolic response, higher nutritional needs, and a decreased capacity for utilization of parenteral substrate.

OBJECTIVE

We sought to analyze the relation between a patient's metabolic state and their nutritional intake, substrate utilization, and nitrogen balance (NB) in mechanically ventilated, critically ill children receiving parenteral nutrition.

DESIGN

This was a cross-sectional study in which resting energy expenditure (REE) and NB were measured and substrate utilization and the metabolic index (MI) ratio (REE/expected energy requirements) were calculated.

RESULTS

Thirty-three children (mean age: 5 y) participated. Their average REE was 0.23 +/- 0.10 MJ x kg(-1) x d(-1) and their average MI was 1.2 +/- 0.5. Mean energy intake, protein intake, and NB were 0.25 +/- 0.14 MJ x kg(-1) x d(-1), 2.1 +/- 1 g x kg(-1) x d(-1), and -89 +/- 166 mg x kg(-1) x d(-1), respectively. Patients with an MI >1.1 (n = 19) had a higher fat oxidation than did patients with an MI <1.1 (n = 14; P < 0.05). Patients with lipogenesis (n = 13) had a higher carbohydrate intake than did patients without lipogenesis (n = 20; P < 0.05). Patients with a positive NB (n = 12) had a higher protein intake than did patients with a negative NB (n = 21; P < 0.001) and lower protein oxidation (P < 0.01).

CONCLUSIONS

Critically ill children are hypermetabolic and in negative NB. In this population, fat is used preferentially for oxidation and carbohydrate is utilized poorly. A high carbohydrate intake was associated with lipogenesis and less fat oxidation, a negative NB was associated with high oxidation rates for protein, and a high protein intake was associated with a positive NB.

Early feeding strategies in preterm and critically ill neonates

This two-part article presents feeding strategies for the NICU population over the first several weeks of life. It focuses primarily on the theory and approach to feeding extremely low birth weight (ELBW) infants, but also addresses some issues pertinent to larger, ill infants. The premise for these recommendations is that avoiding early malnutrition in ELBW and ill infants has both short- and long-term benefits. Many practitioners may consider our approach to be somewhat aggressive. In this strategy, total parenteral nutrition (TPN) is initiated in the first hours after birth and is given together with initially small, and then increasing, enteral feedings beginning on the first or second day of life. The role of the TPN is to provide rapid, maximal nutrition and that of the early enteral feedings is to "prime" the gut and stimulate normal gastrointestinal tract activity.

Energy metabolism of infants and children with systemic inflammatory response syndrome and sepsis

OBJECTIVE

To evaluate whether critically ill children with systemic inflammatory response syndrome (SIRS) or sepsis have altered resting energy expenditure (REE) and substrate utilization.

SUMMARY BACKGROUND DATA

Studies in adults with sepsis have shown increased energy expenditure and mobilization of endogenous fat. In infants and children, energy metabolism and substrate utilization during sepsis have not been characterized.

METHODS

Metabolic studies were performed in 21 critically ill children with SIRS or sepsis. Twenty-one stable control children, matched for weight, were also studied. Seven patients required inotropic support and 17 received mechanical ventilation. Fifteen patients with SIRS had evidence of bacterial, fungal, or viral infection and were considered septic. Respiratory gas exchange was measured by computerized indirect calorimetry for 1 to 2 hours continuously.

RESULTS

The REE of patients with SIRS or sepsis was not different from that of controls. Similarly, there were no differences in carbon dioxide production and oxygen consumption. Resting energy metabolism was not different between patients with SIRS and patients with sepsis. In addition, the presence of low platelet count or inotropic support did not affect resting energy metabolism. The median respiratory quotient of patients with SIRS or sepsis was 0.88 (range 0.75-1.12), indicating mixed utilization of fat and carbohydrate; this was not significantly different from that of controls. The Pediatric Risk of Mortality Score was not significantly correlated with REE or respiratory quotient.

CONCLUSIONS

The energy requirements of children with SIRS or sepsis are not increased. Their resting metabolism is based on both carbohydrate and fat utilization. The authors speculate that these children divert the energy for growth into recovery processes.

Intravenous nutrition and postnatal growth of the micropremie

There is a growing body of evidence that early nutritional practices may affect short-term growth and developmental outcome. In addition, they may play a role in determining adult health and disease. There is much that needs to be learned about safe and efficacious nutrient administration in the ELBW population; about techniques to assess the effect of different nutritional strategies; and about the long-term effects of these regimen or development outcome, growth, and disease.

Lipid peroxidation can be reduced in infants on total parenteral nutrition by promoting fat utilisation

BACKGROUND/PURPOSE

Increased oxygen-derived free radical activity has been reported during total parenteral nutrition (TPN) in infants and has been specifically linked to the fat infusion. The aim of this study was to test the hypothesis that during TPN, oxygen-derived free radical production can be reduced by increasing the utilisation of fat.

METHODS

In experiment A (17 patients) the fat infusion was kept constant (3 g/kg/d) and the carbohydrate infusion was changed from 18 g/kg/d on day 1 to 10 g/kg/d on day 2. In experiment B (six patients) the carbohydrate infusion remained constant and the fat infusion was changed from 3 g/kg/d on day 1 to 0 g/kg/d on day 2. Fat utilisation was measured by indirect calorimetry. Plasma malondialdehyde, an index of lipid peroxidation resulting from increased oxygen-derived free radical activity, was measured by a colorimetric assay.

RESULTS

In both experiments there was no significant change between the two study phases in oxygen consumption, carbon dioxide production, and resting energy expenditure demonstrating that the patients were metabolically stable. In experiment A there was a significant (P = .0005) increase in fat utilisation and a significant (P = .009) decrease in malondialdehyde (MDA) concentration between the two phases. In experiment B there was also a significant (P = .007) decrease in MDA concentration. The decrease in MDA concentration was similar between the two experiments.

CONCLUSIONS

It is not necessary to stop the infusion of fat to reduce free radical production. Promoting fat utilisation by reducing the carbohydrate-fat ratio of the TPN reduces free radical activity to a similar extent as fat exclusion. These findings have important implications for the composition of TPN.

Nutritional support in malnourished paediatric patients

An imbalance between a person's energy requirements and his or her dietary protein and caloric supply is the source of protein energy malnutrition (PEM), which compounds the problems of any underlying disease. Malnutrition may occur quite rapidly in critically ill patients, particularly those suffering from sepsis, setting up a vicious cycle with worsening of the PEM. This chapter examines the main consequences of PEM, the means whereby appropriate nutrition may be provided, and risks for severely malnourished paediatric patients in hospital. If the gastrointestinal tract can be used for refeeding, it should be used. When the gastrointestinal tract is unable to meet the protein and energy requirements, parenteral nutrition (PN) is required. PN is efficient but carries a high risk of metabolic complications known as the refeeding syndrome and directly related to the homeostatic changes secondary to severe PEM. Catch-up growth may be achieved by using appropriate nutritional support. Changes in body composition have to be assessed during the course of renutrition.

Energy requirements of surgical newborn infants receiving parenteral nutrition

The energy requirement for mature newborn infants receiving total parenteral nutrition is approximately 100 kcal.kg-1.d-1. There is no necessity to increase the caloric intake after an uncomplicated operation. Energy requirements are affected by the maturity of the infant, the degree of operative stress, opioid medication, and the presence or absence of sepsis. In general, glucose intake should not exceed the resting energy expenditure. Glucose administration exceeding 18 g.kg-1.d-1 is associated with lipogenesis and reduced oxygenation of exogenous lipid. Resting energy expenditure varies widely between infants, and energy intake, based on clinical and biochemical monitoring, should be adjusted for individual patients.

Nutritional considerations and management of the child with liver disease

Nutritional management of the infant and child with liver disease is highly dependent upon the type of liver disease. Acute liver disease, such as that secondary to viral hepatitis, requires no specific nutritional therapy with the exception that branched-chain amino acid supplements may be indicated in the management of hepatic encephalopathy. Nutritional management of the child with chronic liver disease depends upon whether or not cholestasis is present, since in that condition, large amounts of fat-soluble vitamin supplements and medium-chain triglycerides are usually required for optimum growth. However, anicteric cirrhotic liver disease also presents nutritional challenges because of hypermetabolism, enteropathy, and increased protein oxidation. Certain inborn errors of metabolism that result in liver disease (including galactosemia, hepatorenal tyrosinemia, hereditary fructose intolerance, and Wilson's disease) have specific nutritional requirements. And, finally, the advent of pediatric liver transplantation has placed new emphasis on the importance of optimum nutritional management of the child with chronic liver disease, since improvement of nutritional status in the pretransplant period maximizes success of the transplant. This review will focus on the pathogenesis of malnutrition in childhood liver disease and will provide recommendations for nutritional assessment and monitoring as well as nutritional management of cholestatic liver disease, anicteric cirrhotic liver disease, and the inborn errors of metabolism enumerated above. Specific recommendations for nutritional management of the child awaiting liver transplantation will be provided.

Low birthweight infants and total parenteral nutrition immediately after birth. II. Randomised study of biochemical tolerance of intravenous glucose, amino acids, and lipid

This randomised study aimed to compare the biochemical tolerance of three parenteral regimens administered during the first 48 hours of life. Twenty nine infants were randomised to either: (a) glucose 10%; (b) glucose 10%/amino acids; (c) glucose 10%/amino acids/lipid. Blood samples for plasma amino acid profiles, cholesterol, and triglyceride concentrations were taken on arrival in the neonatal unit and again between 36 and 48 hours of life. Arterial or capillary blood gas analysis and blood glucose estimates were performed routinely during the first 48 hours of life. There was a sharp decline in plasma amino acid concentrations in the group following (a) compared with the two groups following (b) and (c) regimens. In all groups plasma triglyceride and cholesterol were not significantly different before and after 48 hours of lipid infusion. Peak mean (SE) bilirubin concentrations (203 (12) v 181 (19) v 220 (20) mumol/l) and the need for phototherapy (nine v eight v five infants) were similar for each of the groups. Hypoglycaemia occurred most frequently during the (b) regimen and least commonly in the (c) group. There are potential health gains from giving parenteral nutrition to low birthweight infants immediately after birth, and this study indicates that restriction of nutritional intake immediately after birth in preterm infants may cause significant metabolic disturbance. This can be prevented by starting a regimen of intravenous amino acids and lipid immediately after birth.

Protein metabolism kinetics in neonates: effect of intravenous carbohydrate and fat

The aim of this study was to determine the effect of different glucose/fat ratios on protein metabolism kinetics in newborn infants receiving total parenteral nutrition (TPN). Eighteen studies were done on 14 infants receiving TPN (weight 3.15 +/- 0.22 kg [mean +/- SEM]; gestational age 37.8 +/- 0.9 weeks; postnatal age 14.0 +/- 3.7 days). There were two study groups. Group A infants (n = 9) received 10.0 g/kg/d of dextrose and 4.0 g/kg/d of fat; group B infants (n = 9) received 19.0 g/kg/d of dextrose and 0.5 g/kg/d of fat. Caloric intake (86 kcal/kg/d) and amino-acid intake (2.5 g/kg/d) were the same in the two groups. There was no difference between the groups with regard to weight, gestational age, and postnatal age. Intravenous diet was constant during the 3-day study period. Timed urinary nitrogen excretion was determined. On day 3 of the study, each infant received a priming dose of 15 mumol/kg of [13C]leucine followed by a 6-hour infusion at 6 mumol/kg/h. Plasma and breath samples were taken at hourly intervals, and CO2 production was measured by indirect calorimetry. Plateau levels of plasma [13C]-alpha Ketoisocaproic acid (KIC) enrichment and expired 13CO2 enrichment were determined by gas chromatograph mass spectrometry. Protein metabolism kinetics were calculated. Results were: nitrogen balance 0.27 +/- 0.01 g/kg/d, total protein flux 10.38 +/- 0.34 g/kg/d, total protein synthesis 9.64 +/- 0.31 g/kg/d, total protein breakdown 7.86 +/- 0.38 g/kg/d, and total protein oxidation/excretion 0.92 +/- 0.04 g/kg/d.(ABSTRACT TRUNCATED AT 250 WORDS)

A new equation to predict the resting energy expenditure of surgical infants

It is essential that adequate calories are provided to newborns to cover their energy expenditure. This is difficult to measure and varies significantly between individuals. The aim of this study was to develop an equation to predict the basal energy requirements of stable surgical infants, using easily measurable parameters. Resting energy expenditure (REE) was measured using computerized open-circuit indirect calorimetry. One hundred twenty-two measurements were made on different days in 46 stable nonventilated infants. The measured REE was 34.41 +/- 0.46 cal/kg/min; (mean +/- SEM). Three body-size measurements correlated significantly with REE (cal/min): weight in kilograms (r = .87; P < .00001), body surface area in square meters (r = .86; P < .00001), and lean body mass in kilograms (r = .81; P < .00001). Five other independent variables correlated significantly with REE (cal/kg/min): heart rate in beats per minute (r = .60; P < .00001), postnatal age in days (r = .49; P < .00001) caloric intake in cal/kg/min (r = .44; P < .00001), gestational age in weeks (r = .43; P < .00001), and rectal temperature in degrees Celsius (r = .19; P = .04). Weight, heart rate, age, gestational age, and temperature were regarded as independent predictor variables of REE for the multiple stepwise regression analysis. Three variables entered this highly significant equation: REE (cal/min) = -74.436 + (34.661 x weight in kg) + (0.496 x heart rate in beats/min) + (0.178 x age in days) (r = .92; F = 230.07; significance, F < .00001).(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative changes in resting energy expenditure and interleukin 6 level in infants

The relationship was determined between resting energy expenditure (REE) and interleukin (IL)6 level following surgery in infants. Sixteen infants of mean(s.e.m.) weight 3.2(0.2) kg undergoing uncomplicated surgery were studied. The operative stress score was recorded and plasma IL-6 levels were measured before and 4, 8, 12 and 24 h after surgery. Respiratory gas exchange was measured by indirect calorimetry before and at 2, 4, 6, 8, 10, 12, 24 and 48 h. Urinary nitrogen excretion was measured and calculated. IL-6 levels increased significantly after surgery (P = 0.006) and were maximal at 12 h. There was a linear correlation between the increase in IL-6 level and operative severity score (r = 0.61, P = 0.012). REE increased significantly after operation (P < 0.001), peaking at 2-4 h, and returned to baseline levels by 12 h. The changes in REE preceded those in IL-6. IL-6 is a marker of the stress response in infants and may play a role in the subsequent modulation of this response.

The metabolic response to operative stress in infants

The aim of this study was to characterize energy metabolism and substrate utilization in infants following an operation. Nineteen infants (weight 3.2 +/- 0.2 kg) who had an operation were studied. Anesthesia was standardized and operative stress score (OSS) was recorded. Five infants had a minor operation (OSS < 7), and 14 infants had a major operation (OSS > or = 7). Energy and nitrogen intake were constant during the 48-hour study period. Respiratory gas exchange was measured by indirect calorimetry preoperatively, and postoperatively for the first 12 hours continuously and at 24 hours, 48 hours, and 5 days. Urinary nitrogen excretion rate was measured for the first 48 hours following the operation. Physical activity was scored. Resting energy expenditure (REE) and nonprotein respiratory quotient (NPRQ) were calculated. REE increased postoperatively, peaking at 2 to 4 hours, and returned to baseline levels by 12 to 24 hours. Peak REE was significantly higher than baseline REE (P < .001). Substrate utilization was not altered by operation. The increase in REE was significantly greater in infants having a major operation than in infants having a minor operation (P < .05). Among infants having a major operation, the increase in REE was significantly greater in those infants more than 48 hours old, than in those infants less than 48 hours old (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose utilization in the surgical newborn infant receiving total parenteral nutrition

Glucose is the main source of nonprotein calories in total parenteral nutrition (TPN). However, its use has been associated with various nutritional, metabolic, and respiratory complications. The aim of this study was to determine, in the stable surgical newborn infant, the characteristics of carbohydrate metabolism, in particular the maximum oxidative threshold for intravenous glucose and the thermogenic effect of glucose. Twenty-one studies were done on 11 infants (weight 2.82 +/- 0.19 kg) receiving TPN containing constant amounts of amino acids (2.5 g/kg/d) and fat (3.0 g/kg/d), and different amounts of glucose (range, 10 to 25 g/kg/d). Oxygen consumption (VO2), carbon-dioxide production (VCO2), and resting energy expenditure (REE) were measured by indirect calorimetry. Urinary nitrogen excretion rate was measured and substrate utilization calculated from the nonprotein respiratory quotient (NPRQ). There was a positive correlation between the predictor variable glucose intake and the dependent variables VO2 (r = .55; P < .05), VCO2 (r = .83; P < .0001), REE (r = .65; P < .005), NPRQ (r = .94; P < .0001), respiratory rate (r = .46; P = .06), and plasma triglycerides level (r = .67; P < .01). When glucose intake exceeded 18 g/kg/d the NPRQ was greater than 1.0, indicating glucose conversion to fat. Above this level of intake, the gradient of the correlation between the predictor variable glucose intake and the dependent variables VCO2 and REE increased. From this study we conclude that: (1) Glucose intake is the principal determinant of glucose utilization and exerts an influence on the metabolism of exogenous fat.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory gas exchange in response to fat-free parenteral nutrition: a comparison after thoracic or abdominal surgery in newborn infants

Thoracic surgery is known to cause a postoperative respiratory failure because of the mechanical problems following chest wall disruption and/or diaphragmatic dysfunction. This study was to verify whether the fat-free intravenous nutritional support of neonates who underwent thoracic surgery could lead to a CO2 production exceeding the patients' respiratory reserves. Respiratory gas exchange and alveolar ventilation were obtained by indirect calorimetry and continuous recordings of transcutaneous PO2 and PCO2. These noninvasive measurements were compared at the same age of 7 +/- 1 days between a group of 7 newborn infants (mean +/- SEM: 3.09 +/- 0.14 kg, 39 +/- 1 weeks) after thoracic surgery versus a group of 8 newborn infants (2.88 +/- 0.17 kg, 37 +/- 1 weeks) after abdominal surgery. The intravenous macronutrient support was the same between both groups: 14 g/kg/d of glucose, 2 g/kg/d of amino acids, 250 kJ/kg/d of energy. One week after surgery, the global metabolic rate (195 kJ/kg/d) was not increased, and comparable between both groups. We documented that early after thoracic surgery, the ventilatory compensation required to handle the CO2 production (6.7 +/- 0.2 mL/kg/min) associated with a positive energy balance (45 +/- 8 kJ/kg/d) was effective.

Glucose versus glucose-fat mixture in the course of total parenteral nutrition: effects on substrate utilisation and energy metabolism in malnourished children

Energy substrate utilisation was evaluated over 21 days in two groups of malnourished children on total parenteral nutrition (TPN). Non-protein energy was infused as glucose (Group A; n = 7) or as a glucose/fat (1:1 v/v) mixture (Group B; n = 10). Results indicated that: 1) net glucose oxidation was related to glucose intake; 2) glucose storage was elevated in group A; 3) net fat synthesis occurred earlier in group B together with constant net fat oxidation which was inversely related to glucose intake (r = -0.89, p < 0.001); 4) lipogenesis from glucose occurred only when glucose intake exceeded 19.3g/kg/d; 5) energy expenditure increased by 36% (group A) and 18% (group B) during renutrition; 6) 73% and 82% of the energy administered in excess of energy required was stored in group A and B respectively. Hence, glucose/fat infusion appears to be more energy-efficient than glucose-alone in TPN of malnourished children.

Energy expenditure and substrate utilization in the course of renutrition of malnourished children

Energy expenditure (EE) and substrate utilization in the course of renutrition of malnourished children is not well understood in children receiving total parenteral nutrition (TPN). The aim of this study was to evaluate, during protein-glucose renutrition, EE and substrate utilization and the relationship between EE and growth and/or protein metabolism. Seven malnourished children were studied during the first 3 weeks of TPN. Weight-for-height = 81.4 +/- 8.0%, with an initial weight of 4.5 +/- 3.3 kg. Caloric support was progressively increased according to a preestablished protocol. Every 7 days the following were determined: (1) EE at 3 different 3-hour intervals per day using an open circuit indirect calorimetric system, (2) anthropometrically defined fat free mass (FFM), and (3) 24-hour urinary 3-methylhistidine (3-M-His) and protein balance. Compared to initial values, EE increased 13% at day 7 and 36% at day 14. A negative relationship was found between the amount of perfused glucose and lipid utilization (r = -0.82; p less than 0.0001). EE per kilogram of total body FFM changes during renutrition were more than EE changes per kilogram of total body weight. There was a relationship between EE and weight gain (r = 0.62; p less than 0.005) and a positive relationship between EE and protein gain (r = 0.48; p = 0.012) and 3-M-His excretion (r = 0.51; p less than 0.026).(ABSTRACT TRUNCATED AT 250 WORDS)

Partition of energy metabolism in the surgical newborn

Variations in energy expenditure (EE) and substrate utilization were investigated in 12 surgical neonates (body weight, 2.81 +/- 0.15 kg) receiving total parenteral nutrition (TPN) at an energy intake of 66.34 +/- 2.16 kcal/kg/d in a thermoneutral environment of 32 degrees C to 34 degrees C. Respiratory gas exchange was continuously recorded for 12 hours by a computerized, open-circuit indirect calorimeter. Physical activity was monitored on a modified Freymond scale. Urine was collected over 3 days, including the time of the calorimetry study to determine the urinary nitrogen excretion rate. Oxygen consumption, carbon dioxide production, nonprotein respiratory quotient, and EE were calculated according to the principles of indirect calorimetry for each 30-minute period and for the entire 12 hours. During the indirect calorimetry study the patients were receiving a fat-free TPN mixture consisting of 10% glucose and 2% amino acids (GL/AA) for 8 hours. The fat-free TPN was interrupted by an isocaloric and isovolemic infusion of intralipid 10% (IL) for 4 hours. The effect of physical activity on EE was evaluated separately according to the macronutrient intake (GL/AA for 8 hours v IL for 4 hours) and then combined throughout the 12 hours of intravenous alimentation. The neonates were resting during 80% of the 12-hour study time (range, 38% to 90%). The partition of EE expressed as mean +/- SEM in kcal/kg/d was: total EE 48.5 +/- 2.1; resting EE 43.9 +/- 1.6; energy cost of activity 4.6 +/- 1.3.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic and clinical consequences of changing from high-glucose to high-fat regimens in parenterally fed newborn infants

To evaluate the metabolic and clinical consequences of changing from high-glucose to high-fat regimens during initiation of parenteral nutrition, we performed 22 studies in 11 newborn infants (birth weight (mean +/- SD) 2.54 +/- 0.54 kg, gestational age 37 +/- 3 weeks, postnatal age 8 +/- 3 days) maintained in a constant thermal environment. In a paired design, two isoproteinic (2.4 +/- 0.2 gm/kg/day) and isocaloric (64 +/- 6 kcal/kg/day) regimens differing by source of energy (high glucose vs high lipid) were infused on consecutive days. Environmental and body temperatures were recorded during a 4-hour period, and 24-hour urinary excretions of catecholamines, nitrogen, and C peptide were measured. Despite constant incubator and average skin temperatures, the rectal and interscapular temperatures rose significantly when the high-glucose regimen was changed to a high-lipid regimen. The specific locations of these changes in body temperature suggested brown fat activation. A significant drop in nitrogen retention (63 +/- 9% vs 56 +/- 10%) during the lipid infusion could be further evidence of a metabolic adaptation to the rapid change in energy substrates.

Resting energy expenditure is increased in infants and children with extrahepatic biliary atresia

To determine if liver dysfunction in children affects energy and macronutrient homeostasis, we performed 13 metabolic studies in 11 patients (age, 17.8 +/- 5.9 months [mean +/- SEM]) with extrahepatic biliary atresia (EHBA). Nutritional balance, indirect calorimetry, anthropometry, and biochemical liver function tests were utilised. Sixty-four percent of the energy losses were in the form of stool fat. Energy expenditure (68 kcal/kg/d) was 29% higher than normal (P less than 0.0025). Only one third of the metabolisable energy intake (37 kcal/kg/d) was stored in the body for new tissue synthesis. In spite of the bountiful protein intake for age, the increased protein oxidation (2g/kg/d) resulted in a virtually zero mean nitrogen balance. In addition, four patients oxidised endogenous protein as well. The respiratory quotient was 0.96, and did not change significantly between pre- and post-meal measurements, suggesting a predominant utilisation of carbohydrate for energy metabolism. Net lipid oxidation was severely diminished. We found that the higher the serum aspartate aminotransferase level (previously named SGOT), the lower the net fat oxidation, and the higher the conversion of glucose to fat. These data suggest that markedly increased energy expenditure contributes to the malnutrition of patients with EHBA. We characterised for the first time how severe liver disease in infants and children affects carbohydrate, fat, and protein metabolism, thus inducing protein-energy malnutrition.