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

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.

Indirect Calorimetry: History, Technology, and Application

Measurement of energy expenditure is important in order to determine basal metabolic rate and inform energy prescription provided. Indirect calorimetry is the reference standard and clinically recommended means to measure energy expenditure. This article reviews the historical development, technical, and logistic challenges of indirect calorimetry measurement, and provides case examples for practicing clinicians. Formulae to estimate energy expenditure are highly inaccurate and reinforce the role of the indirect calorimetry and the importance of understanding the strength and limitation of the method and its application.

Nutritional management in the critically ill child with acute kidney injury: a review

Acute kidney injury (AKI) in critically ill children is frequently a component of the multiple organ failure syndrome. It occurs within the framework of the severe catabolic phase determined by critical illness and is intensified by metabolic derangements. Nutritional support is a must for these children to improve outcomes. Meeting the special nutritional needs of these children often requires nutritional supplementation by either the enteral or the parenteral route. Since critically ill children with AKI comprise a heterogeneous group of subjects with varying nutrient needs, nutritional requirements should be frequently reassessed, individualized and carefully integrated with renal replacement therapy. This article is a state-of-the-art review of nutrition in critically ill children with AKI.

The challenge of developing a new predictive formula to estimate energy requirements in ventilated critically ill children

BACKGROUND

Traditionally, energy requirements have been calculated using predictive equations. These methods have failed to calculate energy expenditure accurately. Routine indirect calorimetry has been suggested, but this method is technically demanding and costly. This study aimed to develop a new predictive equation to estimate energy requirements for critically ill children.

METHODS

This prospective, observational study on ventilated children included patients with an endotracheal tube leak of < 10% and fractional inspired oxygen of < 60%. An indirect calorimetry energy expenditure measurement was performed and polynomial regression analysis was used to develop new predictive equations. The new formulas were then compared with existing prediction equations.

RESULTS

Data from 369 measurements were included in the formula design. Only weight and diagnosis influenced energy expenditure significantly. Three formulas (A, B, C) with an R² > 0.8 were developed. When we compared the new formulas with commonly used equations (Schofield, Food and Agriculture Organization/World Health Organization/United Nations University, and White equation), all formulas performed very similar, but the Schofield equation seemed to have the lowest SD.

CONCLUSIONS

All 3 new pediatric intensive care unit equations have R² values of > 0.8; however, the Schofield equation still performed better than other predictive methods in predicting energy expenditure in these patients. Still, none of the predictive equations, including the new equations, predicted energy expenditure within a clinically accepted range, and further research is required, particularly for patients outside the technical scope of indirect calorimetry.

Allometric Prediction of Energy Expenditure in Infants and Children

Predicting energy needs in children is complicated by the wide range of patient sizes, confusing traditional estimation equations, nonobjective stress-activity factors, and so on. These complications promote errors in bedside estimates of nutritional needs by rendering the estimation methods functionally unavailable to bedside clinicians. Here, the authors develop a simple heuristic energy prediction equation that requires only body mass (not height, age, or sex) as input. Expert estimation of energy expenditure suggested a power-law relationship between mass and energy. A similar mass-energy expenditure relationship was derived from published pediatric echocardiographic data using a Monte Carlo model of energy expenditure based on oxygen delivery and consumption. A simplified form of the equation was compared with energy required for normal growth in a cohort of historical patients weighing 2 to 70 kg. All 3 methods demonstrate that variation in energy expenditure in children is dominated by mass and can be estimated by the following equation: Power(kcal/kg/d) = 200 × [Mass(kg)^(−0.4)]. This relationship explains 85% of the variability in energy required to maintain expected growth over a broad range of surgical clinical contexts. A simplified power-law equation predicts real-world energy needs for growth in patients over a wide range of body sizes and clinical contexts, providing a more useful bedside tool than traditional estimators.

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.

The impact of enteral feeding protocols on nutritional support in critically ill children

BACKGROUND

Studies have shown that feeding protocols may assist in achieving optimal nutritional care in critically ill children. The present study aimed to assess the impact of enteral feeding protocols on nutritional support practices through a continuous auditing process over a defined period.

MATERIALS AND METHODS

A prospective audit on nutritional practice was initiated in 1994-1995 on all ventilated patients who were admitted for more than a complete 24-h period in the paediatric intensive care unit. The audit was repeated 1997-1998, 2001 and 2005. The collection of data on outcomes included the time taken to initiate nutritional support, the proportion of patients fed via the enteral versus parenteral route, and the proportion of children reaching 50% and 70% of the estimated average requirement (EAR) by day 3. Feeding algorithms and protocols were introduced after each audit with a view to improving practices.

RESULTS

Over the study period, time taken to initiate nutrition support was reduced from 15 h (1994-1995), 8 h (1997-1998), 5.5 h (2001) to 4.5 h (2005). The proportion of patients on parenteral feeds was reduced from 11% (1994-1995) to 4% (2005). An increase was also documented in the percentage of patients receiving a daily energy provision of 50% and 70% of the EAR by day 3 after the initiation of nutritional support (6% in 1994-1995 to 21% in 2005 for 70% of EAR).

CONCLUSION

The present study demonstrates that feeding protocols improve nutritional practices in a paediatric intensive care unit. However, protocol introduction needs to be monitored regularly through audit.

The pediatric multiple organ dysfunction syndrome

OBJECTIVES

To review the epidemiology of pediatric multiple organ dysfunction syndrome (MODS) and summarize current concepts regarding the pathophysiology of shock, organ dysfunction, and nosocomial infections in this population.

DATA SOURCE

A MEDLINE-based literature search using the keywords MODS and child, without any restriction to the idiom.

MAIN RESULTS

Critically ill children may frequently develop multisystemic manifestations during the course of severe infections, multiple trauma, surgery for congenital heart defects, or transplantations. Descriptive scores to estimate the severity of pediatric MODS have been validated. Young age and chronic health conditions have also been recognized as important contributors to the development of MODS. Unbalanced inflammatory processes and activation of coagulation may lead to the development of capillary leak and acute respiratory distress syndrome. Neuroendocrine and metabolic responses may result in insufficient adaptive immune response and the development of nosocomial infections, which may further threaten host homeostasis.

CONCLUSIONS

Over the last 20 yrs, there has been an increasing knowledge on the epidemiology of pediatric MODS and on the physiologic mechanisms involved in the genesis of organ dysfunction. Nevertheless, further studies are needed to more clearly evaluate what is the long-term outcome of pediatric MODS.

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.

Mitochondrial function in sepsis: acute phase versus multiple organ failure

OBJECTIVE

To describe temporal changes in mitochondrial function during the septic process, including the recovery phase.

DESIGN

Literature review.

SUBJECTS

Clinical studies and laboratory models.

MAIN RESULTS

Biochemical and ultrastructural mitochondrial abnormalities have been recognized in in vivo, ex vivo, and in vitro laboratory models of sepsis for >30 yrs. Short-term models show variable effects on mitochondrial function and structure; this is likely related to differences in model design, including species, organs studied, degree of septic insult, and degree of resuscitation. Longer-term models more consistently reveal mitochondrial dysfunction and damage. There is a rebound increase in oxygen consumption and resting energy expenditure in the recovery phase of sepsis. This could reflect mitochondrial recovery (biogenesis) that may restore the energy supply needed to fuel restorative metabolic processes and enable patient survival.

CONCLUSION

Mitochondrial dysfunction seems to be intrinsically involved in the pathogenesis of multiple organ failure. As a consequence of a progressive decrease in energy availability, metabolism must decrease or the cell will die. The interplay between adenosine 5'-triphosphate supply and demand, dictated by the degree of mitochondrial dysfunction and the level of metabolic shutdown (analogous to a hibernation-type response), seems to be crucial in determining outcome. Further studies are needed to confirm this hypothesis.

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.

Critical appraisal of the management of severe malnutrition: 2. Dietary management

In the dietary management of severe acute malnutrition in children, there is evidence to support the WHO Manual's protocol of cautious feeding of a low energy and protein formula with small frequent feeds in the initial phase of treatment, particularly in kwashiorkor. However, this initial milk diet (WHO F-75) might benefit from increasing the sulphur amino acid, phosphorus and potassium content and reducing the lactose content, but further studies are needed. Careful tube-feeding results in faster initial recovery and weight gain, but has a significant risk of aspiration in poorly supervised settings. Ready-to-use therapeutic food is an important recent advance in the dietary management of malnutrition in ambulatory settings, allowing more effective prevention programmes and earlier discharge from hospital where community follow-up is available. It should be included in future protocols. There is very good evidence on the use of micronutrients such as zinc, and preliminary evidence suggests that smaller doses of daily vitamin A are preferable to a single large dose on admission for severe malnutrition.

Laparoscopic surgery in children is associated with an intraoperative hypermetabolic response

BACKGROUND

Laparoscopic surgery is thought to be associated with a reduced metabolic response compared to open surgery. Oxygen consumption (VO2) and energy metabolism during laparoscopic surgery have not been characterized in children.

METHODS

We measured respiratory gas exchange intraoperatively in children undergoing 19 open and 20 laparoscopic procedures. Premature infants and patients with metabolic, renal, and cardiac abnormalities were excluded. Anesthesia was standardized. Unheated carbon dioxide was used for insufflation. VO2 was measured by indirect calorimetry. Core temperature was measured using an esophageal temperature probe.

RESULTS

We found a steady increase in VO2 during laparoscopy. The increase in VO2 was more marked in younger children and was associated with a significant rise in core temperature. Open surgery was not associated with significant changes in core temperature or VO2.

CONCLUSIONS

Laparoscopy in children is associated with an intraoperative hypermetabolic response characterized by increased oxygen consumption and core temperature. These changes are more marked in younger children.

C-Reactive protein-determined injury severity: length of stay predictor in surgical infants

BACKGROUND/PURPOSE

Serum C-reactive protein (CRP) levels reflect the severity of the metabolic response to injury in critically ill children. During this period, caloric overfeeding can increase complications and delay recovery. The authors hypothesized that by avoiding excessive caloric delivery, the effect of injury severity would be the major factor determining clinical outcome.

METHODS

Twenty-eight surgical infants who had indirect calorimetry measurements while in the Neonatal Intensive Care Unit between August 2000 and January 2002 were studied. Serum CRP concentrations, mean energy expenditure (MEE), respiratory quotient (RQ), length of hospital stay (LOS), and caloric intake (I) at the time of indirect calorimetry were recorded. Data were analyzed using the Pearson product-moment correlation.

RESULTS

Peak serum CRP was significantly correlated to LOS in all patients (r = 0.79, P < .0001). When net caloric balance (I-MEE) did not exceed 5 kcal/kg/d (n = 9), peak serum CRP was correlated positively with RQ (r = 0.66, P = .05). When I-MEE exceeded 5 kcal/kg/d (n = 19), the positive correlation of serum CRP with RQ was diminished (r = 0.23, P = .33).

CONCLUSIONS

CRP-measured injury severity is a major determinant of clinical outcome in surgical infants. In addition, overfeeding causes additional RQ elevation.

Nutritional support in 111 pediatric intensive care units: a European survey

OBJECTIVE

To study current strategies in nutritional management of pediatric intensive care units (PICUs) in Europe, focusing on energy requirements.

DESIGN AND SETTING

Survey by a 35-item questionnaire sent to representatives of 242 PICUs in 28 countries. Addresses were obtained from national PICU associations and the members' list of the European Society of Pediatric and Neonatal Intensive Care.

PARTICIPANTS

Staff members of 111 European PICUs (46%) from 24 countries.

MEASUREMENTS AND RESULTS

Predominantly physicians were reported to be responsible for nutritional support. In 73% of PICUs a multidisciplinary nutritional team was available. In most PICUs daily energy requirements were estimated using weight, age, predictive equations and correction factors. In 17% of PICUs energy expenditure was regularly measured by indirect calorimetry. Nutritional status was mostly assessed by weight, physical examination, and a wide range of biochemical blood parameters. Approximately 70% of PICUs used dedicated software for nutritional support. A similar percentage of PICUs regarded "nutrition" as a research topic and part of the residents' training program.

CONCLUSIONS

Most European PICUs regard nutritional support as an important aspect of patient care, as shown by the presence of nutritional teams, software, research, and education. However, energy requirements of pediatric intensive care patient were based predominantly on estimations rather than on measurements.

Body temperature and heat production in suckling rat endotoxaemia: beneficial effects of glutamine

BACKGROUND/PURPOSE

Sepsis is an important cause of neonatal mortality. The aim of the study was to investigate the metabolism of endotoxic neonatal rats and the potential beneficial effect of glutamine.

METHODS

Suckling rats received intraperitoneal saline (control; C), endotoxin (300 microg/g LPS; E), saline+glutamine (2 mmol/g; CG), endotoxin+glutamine (EG), saline+leucine (2 mmol/g; CL) or endotoxin+leucine (EL). Sepsis score (0-8) and rectal temperature were monitored. Hypothermia was defined as rectal temperature less than 32 degrees C. Oxygen consumption (VO2, mL/kg/h), a determinant of heat production, was measured by indirect calorimetry. Data (mean +/- SEM) were compared by analysis of variance (ANOVA), paired t test or Fisher's Exact test.

RESULTS

Endotoxic (E) rats had significantly lower VO2 than C rats from 90 minutes postinjection to the end of the experiment, 210 minutes (VO2 from 150 to 210 minutes: C 671 +/- 45; E 429 +/- 36, P <.0004; n = 8; paired t test). VO2 of CL or CG rats was elevated between 90 and 210 minutes compared with control, but significantly (P <.01) only in the L group (C 706 +/- 31; CG 871 +/- 63; CL 984 +/- 31; n = 7-9, ANOVA). VO2 was significantly higher (P <.05) in EG rats than E rats (E 460 +/- 29; EG 654 +/- 68; n = 9-10). In the EL group, VO2 was raised but was not significantly different from E (E 460 +/- 29; EL 637 +/- 52; n = 8-10). EG rats were significantly less hypothermic between 90 and 210 minutes (58 of 132 measurements) compared with E (95 of 147; P =.0007, Fisher's Exact test), whereas the EL group were similarly hypothermic (74 of 120) to E (P =.7). Sepsis score was significantly lower in the EG group than both E and EL groups (E 4.9 +/- 0.3; EG 3.6 +/- 0.3; EL 5.0 +/- 0.3; n = 40; P <.01; ANOVA).

CONCLUSIONS

Neonatal endotoxaemia lowers VO2, heat production, and body temperature. Glutamine and leucine both cause nutrient-induced thermogenesis in control animals and restore VO2 of endotoxic animals. Glutamine additionally increases rectal temperature, reduces incidence of hypothermia, and improves clinical signs of endotoxic rats. This suggests that glutamine may be beneficial for nutrition in neonatal sepsis.

Carbon dioxide elimination during laparoscopy in children is age dependent

The absorption of carbon dioxide (CO2) used for positive pressure pneumoperitoneum may lead to an increased CO2 load. CO2 elimination during laparoscopy has not been investigated previously in paediatrics. The aim of this study was to characterise the pattern of CO2 elimination during laparoscopic surgery in infants and children.

METHODS

Twenty children undergoing laparoscopy and 19 children undergoing laparotomy for elective abdominal operations were studied. Pneumoperitoneum was achieved using insufflation of unheated CO2. CO2 elimination (metabolically produced + absorbed; milliliters per kilogram per minute) was measured minute by minute during the operation by indirect calorimetry. End-tidal CO2 (kPa) was recorded every 10 minutes. The above variables were assessed before CO2 insufflation, during pneumoperitoneum, and after desufflation.

RESULTS

Before insufflation, CO2 elimination was 4.6 +/- 0.3 ml/kg/min and increased after 15 minutes of pneumoperitoneum to 5.2 +/- 0.3 (P <.001). Post desufflation, CO2 elimination decreased toward preinsufflation values, but did not return to baseline by the end of operation (5.8 +/- 0.3; P <.001). End-tidal CO2 was 4.7 +/- 0.2 preinsufflation, peaked at 1 hour (5.3 +/- 0.2; P <.001) and subsequently decreased in response to ventilatory adjustments. The total amount of CO2 insufflated was positively correlated with patient age (r2 = 0.27; P <.01). CO2 elimination was age related, as indicated by multilevel model analysis and by negative correlations between maximum increase in CO2 elimination and both age (r2 = 0.27; P <.01) and weight (r2 = 0.29; P <.01). These data suggest that the younger or smaller the child, the larger the increase in CO2 elimination. Seven patients (35%) responded to desufflation with a sharp transient increase in CO2 elimination, which did not appear to be related to patient age, length of pneumoperitoneum, abdominal pressure, or type of operation.

CONCLUSIONS

During pneumoperitoneum, younger children absorb proportionately more CO2 than older individuals. The short-lived increase in CO2 elimination postdesufflation may be related to an increase in venous return from the lower limbs after release of the abdominal pressure. These findings suggest that small children warrant close monitoring during laparoscopy and during the immediate postoperative period.

Effect of sepsis syndrome on neonatal oxygen consumption and energy expenditure

OBJECTIVE

To evaluate oxygen consumption (VO2), carbon dioxide production, and energy expenditure (EE) in full-term neonates with early-onset neonatal septicemia daily for 7 days beginning at the day of clinical diagnosis of sepsis.

METHODS

A total of 17 spontaneously breathing full-term neonates, 10 with clinical signs of sepsis and 7 healthy neonates (control group), were enrolled in the study. Age at first study day was 3 +/- 0.9 days in both groups. Sepsis syndrome was defined as a systemic response to a bacterial infection with clinical signs of infection, elevated values of interleukins 6 and 8 and C-reactive protein, and abnormal white blood cell count and positive blood cultures (9 group B streptococci, 1 Escherichia coli). Measurements of VO2 and carbon dioxide production were performed daily for 7 days by means of indirect calorimetry.

RESULTS

In the septic infants, VO2 and EE were increased by about 20% at days 1 to 3 and by 15% at day 4 when compared with the controls. From days 1 to 3, EE averaged 57 +/- 3 kcal/kg/d in the septic neonates and 47 +/- 2 kcal/kg/d in the controls. At day 4, EE was 55 +/- 2 and 47 +/- 2 kcal/kg/d, respectively. Energy intake was about the same in both groups, whereas weight gain during the 7 study days was significantly lower in the sick patients than in the control group (19 +/- 2 g/d vs 33 +/- 9 g/d and 5.4 +/- 0.5 g/kg/d vs 9.4 +/- 2.6 g/kg/d, respectively). Increased EE was associated with increased heart rate (126 +/- 4 vs 112 +/- 4 min(-1) at day 1) and respiratory rate (56 +/- 6 vs 40 +/- 4 min(-1) at day 1). There were no differences in rectal temperature (37.3 +/- 0.4 degrees C vs 37.4 +/- 0.2 degrees C), skin temperature (36.5 +/- 0.4 degrees C vs 36.6 +/- 0.3 degrees C), and oxygen saturation (96 +/- 3% vs 96 +/- 3%) between the 2 groups.

CONCLUSIONS

Neonates with sepsis syndrome have elevated VO2 and EE values that could explain impaired growth during the illness period and may make the infants vulnerable to insufficient calorie supply during the acute phase of septic disease.

Altered neutrophil function in the neonate protects against sepsis-induced lung injury

BACKGROUND/PURPOSE

Neutrophils (PMNs) are well known effectors of lung injury after sepsis. The accumulation of PMNs into the lung is dependent on a complex cascade of events that includes the local production of chemokines. Interestingly, neonates are protected from lung injury after zymosan-induced sepsis. The authors hypothesized that this protection was caused by either altered PMN function or diminished lung chemokine production compared with the adult.

METHODS

Sepsis was induced in neonatal and adult rats by an intraperitoneal injection of zymosan. Animals were killed 24 hours later and lungs examined for PMN accumulation and function, chemokine production, and lung injury.

RESULTS

Septic neonates (SN) were protected from pulmonary edema when compared with septic adults (SA). Lung PMN number and chemokine (MIP-2) production increased in both septic neonates and adults when compared with vehicle (V) treated animals. Conversely, PMN function was decreased significantly in neonates when compared with adults.

CONCLUSIONS

Despite equivalent lung PMN accumulation and chemotactic protein production, PMN function and lung injury in septic neonates was diminished when compared with that of adults. These findings suggest that neonates may be relatively protected from sepsis-induced lung injury caused by immature PMN function.

Effect of lipopolysaccharide and cytokines on oxidative metabolism in neonatal rat hepatocytes

BACKGROUND/PURPOSE

Lipopolysaccharide (LPS) and cytokines produced during neonatal sepsis trigger free radical production, which eventually results in inhibition of liver metabolism. Studies in adults have indicated a hypermetabolic response to sepsis; however, evidence for a hypermetabolic response in neonates is equivocal. This study was carried out to determine whether LPS and cytokines can cause liver hypermetabolism in neonates.

METHODS

The initial bacterial insult and cytokine cascade were mimicked by the addition of lipopolysaccharide (Escherichia coli 055:B5), tumour necrosis factor (TNF-alpha), and interleukin-6 (IL6) during the isolation of hepatocytes by collagenase digestion from 11- to 13-day-old Wistar rats. Hepatocyte oxygen consumption was measured polarographically with cells respiring on palmitate (0.5 mmol/L). Myxothiazol, a specific inhibitor of mitochondrial respiration, was used to distinguish extra- and intramitochondrial oxygen consumption. Morphologic changes were assessed by electron microscopy.

RESULTS

The addition of LPS, TNF-alpha and IL6 during hepatocyte isolation resulted in a 10% decrease in cell yield (P <.05) compared with untreated controls; however, cell viability was unchanged (n = 31). Both total and extramitochondrial oxygen consumption were significantly greater in treated cells compared with untreated controls (P <.05, Student's t test). Electron microscopy indicated that LPS, TNF-alpha, and IL6 did not cause ultrastructural changes to hepatocytes.

CONCLUSIONS

The increase in oxygen consumption was predominantly extramitochondrial and likely to be caused by increased oxygen requirement for cytosolic detoxification and repair purposes. This study shows that liver hypermetabolism metabolism can occur in response to LPS and cytokines. However, during in vivo neonatal sepsis, additional free radical damage may blunt this hypermetabolic response.