Effect of major abdominal operations on energy and protein metabolism in infants and children

[Prospective analysis of inflammatory markers and perioperative clinical data in children with craniosynostosis undergoing reconstructive surgery]

BACKGROUND

Craniosynostosis (CS) is a group of skull malformations manifested by congenital absence or premature closure of cranial sutures. Reconstructive surgery in the second half of life is traditional approach for CS. The issues of surgical stress response after reconstructive surgery for CS in children are still unclear.

OBJECTIVE

To evaluate clinical and laboratory parameters in children undergoing traumatic reconstructive surgery for CS.

MATERIAL AND METHODS

Inclusion criteria were CS, reconstructive surgery, age <24 months, no comorbidities and available laboratory diagnostic protocol including complete blood count, biochemical blood test with analysis of C-reactive protein, procalcitonin, ferritin and presepsin. The study included 32 patients (24 (75%) boys and 8 (25%) girls) aged 10.29±4.99 months after surgery between October 2021 and June 2022. Non-syndromic and syndromic forms of CS were observed in 25 (78.1%) and 7 (21.9%) cases, respectively.

RESULTS

There were no infectious complications. We analyzed postoperative clinical data, fever, clinical and biochemical markers of inflammation.

CONCLUSION

Early postoperative period after reconstructive surgery for CS in children is accompanied by significant increase of inflammatory markers (C-reactive protein, procalcitonin, ferritin). However, these findings do not indicate infectious complications. This is a manifestation of nonspecific systemic reaction. Severity of systemic inflammatory response syndrome with increase in acute phase proteins indicates highly traumatic reconstructive surgery for CS in children. Analysis of serum presepsin allows for differential diagnosis between infectious complication and uncomplicated course of early postoperative period.

Nutrition considerations in pediatric surgical patients

Children who require surgical interventions are subject to physiologic stress, necessitating a period of healing when nutrition needs may temporarily change. Providing appropriate nutrition to children before and after surgery is an important part of minimizing surgical morbidity. There is a clear link between poor nutrition and surgical outcomes, therefore providing good reason for ensuring an appropriate nutrition plan is in place for children requiring surgery. This review will address recent research investigating nutrition considerations for pediatric surgical patients with a focus on practical tools to guide decision making in the preoperative, intraoperative, and postoperative periods.

Providing the Best Parenteral Nutrition before and after Surgery for NEC: Macro and Micronutrients Intakes

Necrotizing enterocolitis (NEC) is the main gastrointestinal emergency of preterm infants for whom bowel rest and parenteral nutrition (PN) is essential. Despite the improvements in neonatal care, the incidence of NEC remains high (11% in preterm newborns with a birth weight <1500 g) and up to 20−50% of cases still require surgery. In this narrative review, we report how to optimize PN in severe NEC requiring surgery. PN should begin as soon as possible in the acute phase: close fluid monitoring is advocated to maintain volemia, however fluid overload and electrolytes abnormalities should be prevented. Macronutrients intake (protein, glucose, and lipids) should be adequately guaranteed and is essential in each phase of the disease. Composite lipid emulsion should be the first choice to reduce the risk of parenteral nutrition associated liver disease (PNALD). Vitamin and trace elements deficiency or overload are frequent in long-term PN, therefore careful monitoring should be planned starting from the recovery phase to adjust their parenteral intake. Neonatologists must be aware of the role of nutrition especially in patients requiring long-term PN to sustain growth, limiting possible adverse effects and long-term deficiencies.

Systematic review of factors associated with energy expenditure in the critically ill

BACKGROUND AND AIMS

Indirect calorimetry is the reference standard for energy expenditure measurement. Predictive formulae that replace it are inaccurate. Our aim was to review the patient and clinical factors associated with energy expenditure in critically ill patients.

METHODS

We conducted a systematic review of the literature. Eligible studies were those reporting an evaluation of factors and energy expenditure. Energy expenditure and factor associations with p-values were extracted from each study, and each factor was classified as either significantly, indeterminantly, or not associated with energy expenditure. Regression coefficients were summarized as measures of central tendency and spread. Metanalysis was performed on correlations.

RESULTS

The search strategy yielded 8521 unique articles, 307 underwent full text review, and 103 articles were included. Most studies were in adults. There were 95 factors with 352 evaluations. Minute volume, weight, age, % body surface area burn, sedation, post burn day, and caloric intake were significantly associated with energy expenditure. Heart rate, fraction of inspired oxygen, respiratory rate, respiratory disease diagnosis, positive end expiratory pressure, intensive care unit days, C- reactive protein, and size were not associated with energy expenditure. Multiple factors (n = 37) were identified with an unclear relationship with energy expenditure and require further evaluation.

CONCLUSIONS

An important interval step in the development of accurate formulae for energy expenditure estimation is a better understanding of relationships between patient and clinical factors and energy expenditure. The review highlights the limitations of currently available data, and identifies important factors that are not included in current prediction formulae of the critically ill.

Malnutrition increases the risk of 30-day complications after surgery in pediatric patients with Crohn disease

BACKGROUND

Pediatric patients with Crohn disease (CD) are frequently malnourished, yet how this affects surgical outcomes has not been evaluated. This study aims to determine the effects of malnourishment in children with CD on 30-day outcomes after surgery.

STUDY DESIGN

The ACS NSQIP-Pediatric database from 2012 to 2015 was used to select children aged 5-18 with CD who underwent bowel surgery. BMI-for-age Z-scores were calculated based on CDC growth charts and 2015 guidelines of pediatric malnutrition were applied to categorize severity of malnutrition into none, mild, moderate, or severe. Malnutrition's effects on 30-day complications. Propensity weighted multivariable regression was used to determine the effect of malnutrition on complications were evaluated.

RESULTS

516 patients were included: 349 (67.6%) without malnutrition, 97 (18.8%) with mild, 49 (9.5%) with moderate, and 21 (4.1%) with severe malnutrition. There were no differences in demographics, ASA class, or elective/urgent case type. Overall complication rate was 13.6% with malnutrition correlating to higher rates: none 9.7%, mild 18.6%, moderate 20.4%, and severe 28.6% (p < 0.01). In propensity-matched, multivariable analysis, malnutrition corresponded with increased odds of complications in mild and severely malnourished patients (mild OR = 2.1 [p = 0.04], severe OR 3.26 [p = 0.03]).

CONCLUSION

Worsening degrees of malnutrition directly correlate with increasing risk of 30-day complications in children with CD undergoing major bowel surgery. These findings support BMI for-age z scores as an important screening tool for preoperatively identifying pediatric CD patients at increased risk for postoperative complications. Moreover, these scores can guide nutritional optimization efforts prior to elective surgery.

LEVEL OF EVIDENCE

IV.

Nutrition: A Primary Therapy in Pediatric Acute Respiratory Distress Syndrome

Appropriate nutrition is an essential component of intensive care management of children with acute respiratory distress syndrome (ARDS) and is linked to patient outcomes. One out of every two children in the pediatric intensive care unit (PICU) will develop malnutrition or have worsening of baseline malnutrition and present with specific micronutrient deficiencies. Early and adequate enteral nutrition (EN) is associated with improved 60-day survival after pediatric critical illness, and, yet, despite early EN guidelines, critically ill children receive on average only 55% of goal calories by PICU day 10. Inadequate delivery of EN is due to perceived feeding intolerance, reluctance to enterally feed children with hemodynamic instability, and fluid restriction. Underlying each of these factors is large practice variation between providers and across institutions for initiation, advancement, and maintenance of EN. Strategies to improve early initiation and advancement and to maintain delivery of EN are needed to improve morbidity and mortality from pediatric ARDS. Both, over and underfeeding, prolong duration of mechanical ventilation in children and worsen other organ function such that precise calorie goals are needed. The gut is thought to act as a "motor" of organ dysfunction, and emerging data regarding the role of intestinal barrier functions and the intestinal microbiome on organ dysfunction and outcomes of critical illness present exciting opportunities to improve patient outcomes. Nutrition should be considered a primary rather than supportive therapy for pediatric ARDS. Precise nutritional therapies, which are titrated and targeted to preservation of intestinal barrier function, prevention of intestinal dysbiosis, preservation of lean body mass, and blunting of the systemic inflammatory response, offer great potential for improving outcomes of pediatric ARDS. In this review, we examine the current evidence regarding dose, route, and timing of nutrition, current recommendations for provision of nutrition to children with ARDS, and the current literature for immune-modulating diets for pediatric ARDS. We will examine emerging data regarding the role of the intestinal microbiome in modulating the response to critical illness.

Effect of laparoscopy and laparotomy on energy and protein metabolism in children: a randomized controlled trial

OBJECTIVE

To compare the effects of surgery on energy and protein metabolism in children randomized to undergo laparoscopic and open surgery.

STUDY DESIGN

We randomized 41 patients to open or laparoscopic Nissen fundoplication. Anesthesia and postoperative management were standardized. We recorded core temperature, respiratory gas exchange preoperatively, intraoperatively, and 4 and 24 hours postoperatively and calculated resting energy expenditure (REE). Protein breakdown was measured by using stable isotopic leucine infusion preoperatively and 4 hours postoperatively.

RESULTS

Intraoperative core temperature and oxygen consumption increased in the laparoscopic group compared with the open group. REE decreased in the early postoperative period in the open group, but did not decrease after laparoscopy. REE at 4 hours was higher after laparoscopy. Protein breakdown also decreased in the early postoperative period; the pattern of change between open and laparoscopic groups was of borderline significance.

CONCLUSIONS

Laparoscopy in children may alter the changes in energy metabolism observed after open surgery. These differences may be partially caused by alterations in intraoperative thermoregulation and protein breakdown during laparoscopy in children.

[Monitoring oxygen consumption in energy metabolism in pediatric anesthesia: clinical utility]

OBJECTIVES

To determine changes in oxygen consumption as a marker of energy metabolism during general inhaled anesthesia in pediatric patients and to identify factors that might influence consumption.

MATERIAL AND METHODS

Prospective, observational, double-blind study in children under inhaled anesthesia in spontaneous ventilation. We monitored heart rate electrocardiogram, noninvasive blood pressure, respiratory frequency, carbon dioxide (CO2) end-expiratory pressure, oxygen saturation by pulse oximetry, state entropy, response entropy, esophageal temperature, and (by indirect calorimetry) oxygen consumption and the respiratory quotient. Capillary blood was extracted every 5 minutes to determine lactate concentration.

RESULTS

Thirty-six patients (ASA 1-2) between 5 and 11 years old were included. Mean (SD) oxygen consumption was 0.6 (0.12) mL x kg(-1)min(-1) at baseline, 5.3 (03) mL x kg(-1) min(-1) during maintenance of anesthesia, and 8.1 (1.1) mL x kg(-1) min(-1) on awakening. A progressive increase was detected in lactic acid concentration, from a baseline mean of 0.8 (0.1) mmol/L to 2.2 (0.9) mmol/L half an hour later; the change was unrelated to oxygen consumption. After correcting the flow of normal saline solution to 0.9%, a significant increase in oxygen consumption (P < .05) was detected. Factors that were significantly correlated (P < 0.1 and r of +/- 0.95) were temperature (oxygen consumption decreased > 10% for each degree centigrade decrease), inspired oxygen fraction > 0.8; sharp changes in the expired CO2 fraction exceeding 2 standard deviations (+/- 6), use of nitrous oxide in the gas mix (inspired nitrous oxide fraction > 20%), the length of the sampling line, and increased respiratory frequency. A model with 3 factors was constructed to explain the kinetics of oxygen consumption during anesthesia.

CONCLUSIONS

Oxygen consumption monitoring may provide an indirect indicator of homeostatic changes during surgery. The ideal system for carrying out such monitoring during anesthesia remains to be found, and the values to guide the anesthesiologist in deciding whether or not to intervene immediately still need to be determined.

Is Energy Expenditure of Infants Predictable After Surgery?

Infants undergoing surgery have unique metabolic demands. The stress of an operation and recovery combined with expectations for growth and development imply elevations in energy expenditure beyond that of healthy, free-living infants. In contrast, surgery may trigger a diversion of energy utilization from tissue accumulation and growth toward the catabolic stress response and cytokine production. Predictive equations are commonly used in clinical settings to estimate basal or resting energy expenditure because measurement techniques such as indirect calorimetry may not be feasible or available. Investigations of measured energy expenditure in surgical infants have portrayed mixed results, however, and estimation equations may not consistently lead to accurate assessment of actual energy needs. Studies are limited in number and quality and often involve a heterogeneous, small population. Grouped outcomes may conceal the wide variability frequently observed in these studies. Measurement of energy expenditure is therefore preferable to the use of predictive equations to customize nutrition intervention for individual infants undergoing surgery.

Age-related changes of muscle and plasma amino acids in healthy children

The aim of the study was to explore if changes in muscle and plasma amino acid concentrations developed during growth and differed from levels seen in adults. The gradient and concentrations of free amino acids in muscle and plasma were investigated in relation to age in metabolic healthy children. Plasma and specimens from the abdominal muscle were obtained during elective surgery. The children were grouped into three groups (group 1: < 1 year, n = 8; group 2: 1-4 years, n = 13 and group 3: 5-15 years, n = 15). A reference group of healthy adults (21-38 years, n = 22) was included in their comparisons and reflected specific differences between children and adults. In muscle the concentrations of 8 out of 19 amino acids analysed increased with age, namely taurine, aspartate, threonine, alanine, valine, isoleucine, leucine, histidine, as well as the total sums of branched chain amino acids (BCAA), basic amino acids (BAA) and total sum of amino acids (P < 0.05). In plasma the concentrations of threonine, glutamine, valine, cysteine, methionine, leucine, lysine, tryptophane, arginine, BCAA, BAA and the essential amino acids correlated with age (P < 0.05). These results indicate that there is an age dependency of the amino acid pattern in skeletal muscle and plasma during growth.

Laboratory validation of the M-COVX metabolic module in measurement of oxygen uptake

A practical method of breath-by-breath monitoring of metabolic gas exchange has previously been developed by GE Healthcare and can now be easily incorporated into existing anaesthetic and critical care monitoring (M-COVX). Previous research using this device has shown good accuracy and precision between the M-COVX measurements and a traditional measurement of gas uptake at the mouth and also against the reverse Fick method during cardiac surgery and critical care, but its accuracy in the paediatric situation and across a range of ventilatory settings awaits validation. We tested the M-COVX metabolic monitor in the laboratory comparing its measurement to a traditional Haldane transformation across a wide range of oxygen consumption values, from 50 ml/minute to just under 300 ml/minute, typical of those expected in anaesthetised adults and children. The M-COVX device showed acceptable accuracy with an overall mean bias of -3.3% (range -15.1 to +4.2%, P = 0.21). Excellent linearity was found, by y = 0.96x + 0.5 ml/minute, r = 0.99. The device showed acceptable robustness to ventilatory changes examined, including changes in respiratory rate, I:E ratio, FiO2 up to 75% and simulated spontaneous breathing. However any induced leak from around the simulated endotracheal tube caused a significant error in paediatric scenarios.

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.

[Evaluation of energy expenditure in children. Physiological and clinical implications and measurement methods]

The present article reviews the importance of the study of energy metabolism and its methods of assessment in children. Classically, energy requirements have been assessed by predictive equations based on anthropometric data. However, there are several physiologic and pathogenic states that may cause discrepancies between estimated and real values and consequently direct measurements of energy expenditure should be used. The gold standard to assess total energy expenditure during prolonged periods is the doubly labeled water method, which is mainly used for research studies. The best approach for resting energy expenditure determination in the clinical setting is indirect calorimetry. However, this method does not provide data on energy consumption under free-living conditions and its use in some critical care patients is restricted by technical limitations. Several other approaches to assess activity have been developed, based on heart rate, body temperature measurements, motion sensors and combined methods.

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 effect of insulin infusion upon protein metabolism in neonates on extracorporeal life support

OBJECTIVE

Critically ill neonates on extracorporeal life support (ECLS) demonstrate elevated rates of protein breakdown that, in turn, are associated with increased morbidity and mortality. This study sought to determine if the administration of the anabolic hormone insulin improved net protein balance in neonates on ECLS.

METHODS

Twelve parenterally fed neonates, on ECLS, were enrolled in a randomized, prospective, crossover trial. Subjects were administered a hyperinsulinemic euglycemic clamp and a control saline infusion. Protein metabolism was quantified using ring-D5-phenylyalanine and ring-D2-tyrosine stable isotopic infusions. Statistical comparisons were made by paired sample t tests (significance at P < 0.05).

RESULTS

Serum insulin concentration increased 20-fold during insulin infusion compared with saline infusion control (P < 0.0001). Protein breakdown was significantly decreased during insulin infusion compared with controls (7.98 +/- 1.82 vs. 6.89 +/- 1.03 g/kg per day; P < 0.05). Serum amino acid concentrations were significantly decreased by insulin infusion (28,450 +/- 9270 vs. 20,830 +/- 8110 micromol/L; P < 0.02). Insulin administration tended to decrease protein synthesis (9.58 +/- 2.10 g/kg per day vs. 8.60 +/- 1.20; P = 0.05). For the whole cohort, insulin only slightly improved net protein balance (protein synthesis minus protein breakdown) (1.60 +/- 0.80 vs. 1.71 +/- 0.89 g/kg per day; P = 0.08). In neonates receiving > or =2 g/kg per day of dietary amino acids insulin significantly improved net protein balance (2.17 +/- 0.34 vs. 2.40 +/- 0.26 g/kg per day; P < 0.01).

CONCLUSIONS

Insulin effectively decreases protein breakdown in critically ill neonates on ECLS. However, this is associated with a significant reduction in plasma amino acids and a trend toward decreased protein synthesis. Insulin administration significantly improves net protein balance only in those ECLS neonates in whom adequate dietary protein is provided.

The pragmatics of feeding the pediatric patient with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) represents the ultimate pulmonary response to a wide range of injuries, from septicemia to trauma. Optimal nutrition is vital to enhancing oxygen delivery, supporting adequate cardiac contractility and respiratory musculature, eliminating fluid and electrolyte imbalances, and supporting the proinflammatory response. Research is providing a better understanding of nutrients that specifically address the complex physiologic changes in ARDS. This article highlights the pathophysiology of ARDS as it relates to nutrition, relevant nutritional assessment, and important enteral and parenteral considerations for the pediatric patient who has ARDS.

Resting energy expenditure and respiratory quotient in adolescents following spinal fusion surgery

STUDY DESIGN

Prospective, 2-factor design. The first factor was the group with 2 levels, spine surgery and control. The second factor was timing with 3 levels, baseline, 1-week follow-up, and 6-week follow-up.

OBJECTIVES

The purpose of this study was to assess changes in caloric requirements and the body's nutritional substrate utilization following spinal surgery in adolescents.

SUMMARY OF BACKGROUND DATA

In an effort to optimize recovery from and assure best possible outcomes after spinal surgery in adolescents, the nutritional requirements of spine surgery patients were evaluated.

METHODS

Indirect calorimetry was used to measure resting energy expenditure, a measure of caloric requirements, and respiratory quotient, an indication of percentages of fat, protein, and carbohydrate utilization. Twenty-three patients undergoing spinal fusion surgery were evaluated immediately before surgery, at an average of 4.8 days after surgery, and at an average 53 days follow-up. A control group of 15 patients completed the same series of 3 tests: baseline, 1-week later, and 6-weeks later.

RESULTS

Resting energy expenditure increased significantly by 150 kcal/day (2.7 kcal/kg/day) following spinal fusion surgery in adolescents. By 6 weeks postoperation, patient's caloric requirements returned to baseline level. No changes in resting energy expenditure occurred in the control group between the 3 test periods. Anterior/posterior surgeries and single surgeries had similar kcal/kg/day requirements after surgery. Respiratory quotient decreased significantly following surgery (0.79 to 0.70), indicating a shift to fat oxidation after surgery. At 6 weeks postoperation, the respiratory quotient returned to baseline level. The control group demonstrated no change in the respiratory quotient during the 3 testing periods.

CONCLUSIONS

Substrate utilization shifts to fat oxidation in adolescents following spinal surgery, indicating lipids would be the alimentation of choice immediately after surgery. Caloric requirements increase 9% above the baseline measurements. Anterior/posterior surgeries and single surgeries (anterior or posterior alone) have the same increase in kcal/kg/day. Because of the substrate utilization change by the body after surgery, a preponderance of these calories should initially be given as lipids. After approximately 6 weeks, both resting energy expenditure and respiratory quotient returned to preoperative levels following spinal surgery in adolescents, indicating special nutrition is not required beyond 6 weeks.

Predicted versus measured energy expenditure by continuous, online indirect calorimetry in ventilated, critically ill children during the early postinjury period

OBJECTIVE

Compare the energy expenditure, predicted by anthropometric equations, with that measured by continuous on-line indirect calorimetry in ventilated, critically ill children during the early postinjury period.

DESIGN

Prospective, clinical study.

SETTING

Pediatric intensive care unit of a pediatric university hospital.

PATIENTS

A total of 43 ventilated, critically ill children during the first 6 hrs after injury.

INTERVENTIONS

An indirect calorimeter was used to continuously measure the energy expenditure for 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Clinical data collected were age, gender, actual and ideal weight, height, and body surface. Nutritional status was assessed by Waterlow and Shukla Index. Severity of illness was determined by Pediatric Risk of Mortality, Physiologic Stability Index, and Therapeutic Intervention Scoring System. Energy expenditure was measured (MEE) by continuous on-line indirect calorimetry for 24 hrs. Predicted Energy Expenditure (PEE) was calculated using the Harris-Benedict, Caldwell-Kennedy, Schofield, Food and Agriculture/World Health Organization/United Nation Union, Maffeis, Fleisch, Kleiber, Dreyer, and Hunter equations, using the actual and ideal weight. MEE and PEE were compared using paired Student's t-test, linear correlation (r), intraclass correlation coefficient (pI), and the Bland-Altman method. Mean MEE resulted in 674 +/- 384 kcal/day. Most of the predictive equations overestimated MEE in ventilated, critically ill children during the early postinjury period. MEE and PEE differed significantly (p<.05) except when the Caldwell-Kennedy and the Fleisch equations were used. r2 ranged from 0.78 to 0.81 (p<.05), and pI was excellent (>.75) for the Caldwell-Kennedy, Schofield, Food and Agriculture/World Health Organization/United Nation Union, Fleisch, and Kleiber equations. The Bland-Altman method showed poor accuracy; the Caldwell-Kennedy equation was the best predictor of energy expenditure (bias, 38 kcal/day; precision, +/- 179 kcal/day). The accuracy in the medical group was higher (pI range,.71-.94) than in surgical patients (pI range,.18-.75).

CONCLUSIONS

Predictive equations do not accurately predict energy expenditure in ventilated, critically ill children during the early postinjury period; if available, indirect calorimetry must be performed.

Nutritional support of the critically ill child

The pediatric metabolic response to injury and operation is proportional to the degree of stress and causes an increase in the turnover of proteins, fats, and carbohydrates. Thereby, substrates are made readily available for the immune response and wound healing. Because this process requires energy, the resting energy expenditure of ill patients increases. Whole-body protein degradation rates are elevated out of proportion to synthetic rates, and negative protein balance also ensues. Neonates and children are particularly susceptible to the loss of lean body mass and its attendant increased morbidity and mortality caused by an intrinsic lack of endogenous stores and greater baseline requirements. An appropriately designed mixed fuel system of nutritional support replete in protein does not quell this metabolic response but can result in anabolism and continued growth in ill children. In addition, the use of adequate analgesia and anesthesia is a readily available and proven means of reducing the magnitude of the catabolism associated with operation and injury. Finally, as hormonal- and cytokine-mediated metabolic alterations are better understood, therapeutic interventions may become available to directly modulate the metabolic response to illness, thus potentially further improving clinical outcome in pediatric surgical patients.

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.

Effective and efficient nutritional support for the injured child

This article discusses the critical points in nutritional support of the injured child. Each applies currently understood basic science information to practical bedside care.

Estimating energy expenditure in critically ill adults and children

Designing effective nutrition support regimens for critically ill patients requires an understanding of the energy needs of each patient. Many disease processes result in elevated caloric requirements, whereas some clinical procedures and medications may diminish the metabolic response. Experienced clinicians are unable to predict the extent to which trauma or injury will affect energy requirements for an individual. Both under- and overfeeding a critically ill patient may prolong hospitalization and increase morbidity and mortality. Applying equations that were originally developed for healthy nonhospitalized individuals to predict the energy requirements of critically ill patients will often result in significant errors and may lead to provision of inappropriate nutritional support. The measurement of resting energy expenditure by indirect calorimetry is a valuable tool and can be used to predict energy requirements for most spontaneously breathing critically ill patients, but may lead to spurious results in mechanically ventilated pediatric patients. In the complex and rapidly changing context of critical illness, individualized assessment of energy requirements is crucial. Whichever technique is used initially to assess energy requirements, sequential monitoring and constant reassessment of each patient is essential to provide the appropriate nutritional care regimen. The purpose of this article is to review the equations for estimating and the techniques, practical aspects, and interpretation of measuring energy expenditure in critically ill patients.

The metabolic needs of critically ill children and neonates

The pediatric metabolic response to injury and operation is proportional to the degree of stress and causes an increase in the turnover of proteins, fats, and carbohydrates. Thereby, substrates are made readily available for the immune response and wound healing. Because this process requires energy, the resting energy expenditure of ill patients increases. Whole-body protein degradation rates are elevated out of proportion to synthetic rates, and negative protein balance also ensues. Neonates and children are particularly susceptible to the loss of lean body mass and its attendant increased morbidity and mortality caused by an intrinsic lack of endogenous stores and greater baseline requirements. An appropriately designed mixed fuel system of nutritional support replete in protein does not quell this metabolic response but can result in anabolism and continued growth in ill children. In addition, the use of adequate analgesia and anesthesia is a readily available and proven means of reducing the magnitude of the catabolism associated with operation and injury. Finally, as hormonal- and cytokine-mediated metabolic alterations are better understood, therapeutic interventions may become available to directly modulate the metabolic response to illness, thus potentially further improving clinical outcome in pediatric surgical patients.

The determinants of protein catabolism in neonates on extracorporeal membrane oxygenation

BACKGROUND/PURPOSE

Protein catabolism appears to be markedly elevated among neonates on extracorporeal membrane oxygenation (ECMO). The aim of this study was to determine the effect of dietary caloric intake on protein catabolism in neonates on ECMO to help construct therapies that may promote anabolism.

METHODS

Twelve total parenteral nutrition (TPN)-fed (88.1 +/- 5.0 [SE] kcal/kg/d; range, 60 to 113 kcal/kg/d; 2.3 +/- 0.2 g/kg/d protein) neonates were studied on ECMO at day of life 7.2 +/- 0.8 d. Protein kinetics were determined using infusions of NaH13CO3 and 1-[13C]leucine.

RESULTS

As expected, C-reactive protein levels were significantly elevated compared with normal controls (44.0 +/- 7.6 mg/L v 1.9 +/- 1.1 mg/L; P < .001). Negative protein balance (-2.3 +/- 0.6 g/kg/d; range, 1 to -6.4 g/kg/d) highly correlated (r = -0.88, P < .001) with total protein turnover. Increased dietary caloric intake correlated with increased amino acid oxidation (r = 0.85, P < .001), increased total protein turnover (r = 0.73, P < .01), continued negative protein balance (r = 0.72, P < .01), increased whole-body protein breakdown (r = 0.66, P < .05), and increased CO2 production rate (r = 0.73, P < .01).

CONCLUSIONS

A surplus of dietary caloric intake does not improve protein catabolism and merely increases CO2 production in these highly stressed neonates. Thus, judicious caloric supplementation is warranted.

Metabolic response to neonatal surgery

The energy and protein metabolism of newborn infants differs from that of older individuals. Although energy expenditure and protein turnover are higher in newborn infants than in adults, the metabolic response to surgery in neonates has not been fully characterized. Preliminary studies indicate that metabolic response to operative stress is different in infants and adults: infants have an increased metabolic rate postoperatively for only 6 to 12 hours and do not have increased protein catabolism. More studies are needed in "stressed" newborn infants to further characterize substrate use and the metabolism of single organs.

Characteristics of protein and energy metabolism in neonates with necrotizing enterocolitis--a pilot study

BACKGROUND/PURPOSE

It is assumed that neonates with necrotizing enterocolitis (NEC) are hypermetabolic. However, the dynamics of protein and energy metabolism in neonates with NEC have not been characterized. The purpose of this study was to test the hypothesis that protein turnover and energy expenditure are increased during the acute stage of NEC and later return to normal values.

METHODS

A pilot study was performed on six neonates with proven NEC (Bell's stage II or III). Patients were studied in two phases: (1) in the acute stage of their disease and (2) when their clinical condition had stabilized. Whole-body protein turnover was calculated using an intravenous infusion of [1-13C] leucine and by measuring the isotopic enrichment of plasma [13C]alpha-ketoisocaproic acid and 13CO2. Respiratory gas exchange was measured simultaneously by computerized indirect calorimetry.

RESULTS

Median gestational age was 36 weeks (range, 28 to 40) with a median postnatal age of 21 days (range, 6 to 47). All patients recovered from the acute episode, although three patients died after recovering from the acute disease from other conditions. The patients studied showed marked variability in protein metabolism kinetics. However, there was no difference in whole-body protein flux between the acute phase (7.6 g/kg/d; range, 5.6 to 18.2) and the recovery phase (7.0 g/kg/d; range, 6.9 to 12.2; P = .89). Furthermore, there was no difference in any of the component parts of wholebody protein turnover. Resting energy expenditure did not change between the acute phase (42.8 kcal/kg/d; range, 34.4 to 52.5) and the recovery phase (51.0 kcal/kg/d; range, 34.9 to 55.3; P = .18).

CONCLUSIONS

This pilot study shows that the rates of protein and energy metabolism in neonates with NEC are comparable with reported values in stable neonates. There was no difference in protein or energy dynamics between study phases. The authors speculate that neonates with NEC may divert the products of protein synthesis from growth to tissue repair.

Of flux and flooding: the advantages and problems of different isotopic methods for quantifying protein turnover in vivo: I. Methods based on the dilution of a tracer

The advantages and problems, both practical and theoretical, of isotope dilution approaches to the determination of whole-body and tissue protein turnover are discussed. It was concluded that: (1) measurements made on the basis of the labelling of plasma and breath are well suited to the measurement of body amino acid oxidation and balance, but because of the problem of inhomogeneity of the body amino acid pools, this approach generally underestimates protein turnover; (2) in investigations of nutritional effects on whole-body amino acid turnover, closer attention should be paid to first-pass splanchnic amino acid metabolism; (3) the trans-organ tracer balance method, particularly if combined with the measurement of tissue amino acid labelling, is a potentially useful approach to the simultaneous and dynamic measurement of both protein synthesis and degradation; (4) leucine may be the most generally useful label for tracer level studies of both whole-body and muscle protein synthesis, as recent studies have shown quite close isotopic equilibrium between muscle-free and tRNA-bound leucine pools.