Metabolism and nutritional frontiers in pediatric surgical patients

The profile of inflammatory and metabolic response in children undergoing heart transplantation

Inflammatory and metabolic response is an important factor to determine clinical outcomes. However, it remains unknown in children undergoing heart transplantation (HTx). We examined the perioperative changes in the inflammatory and metabolic response markers C-reactive protein (CRP) and prealbumin (PA) in 38 heart-transplanted children. Data obtained prior to and within one month after HTx included CRP, PA, total and differential white blood cell counts, doses of inotropes and immunosuppressants, cultures of blood and body fluids, duration of cardiopulmonary bypass (CPB), aortic cross clamp and donor heart ischemia, and days in the intensive care unit (ICU) and hospital. CRP was 32±49 mg/L before HTx, increased to 130±55 mg/L on postoperative day 1-2, and decreased to 21±31 mg/L by one month after HTx. PA was 0.15±0.06 g/L before HTx, decreased to 0.12±0.03 g/L on postoperative day 1-2, and then gradually increased to 0.21±0.10 g/L by one month after HTx. Postoperative CRP positively correlated with epinephrine dosage and CPB duration. PA positively correlated with age. In conclusion, inflammatory and metabolic response is present before HTx and acutely intensified after HTx. It may be mainly influenced by CPB duration and cardiovascular function status.

Kt/V and nPNA in pediatric peritoneal dialysis: a clinical or a mathematical association?

The relationship between dialysis dose and nutrition is a field of particular interest in chronic pediatric dialysis (PD), and a positive correlation between ureaKt/V and nPNA has been published, suggesting a better nutritional status is associated with higher dialysis doses. However, this relationship has also been criticized as being the result of a mathematical coupling resulting from the same variables. The objective of the study was to establish the relationship between dialysis dose (Kt/V) and nutritional variables: daily protein intake (DPI), protein catabolic rate (PCR), protein equivalent of total nitrogen appearance (PNA) and nitrogen balance (NB) in dialyzed children. A cohort, prospective, observational study was carried out, for which 223 biochemical measurements were performed in 20 patients, ages 1 month to 14.3 years old (13 males), under PD for a 12-month period of follow-up. Monthly residual and total ureaKt/V, DPI, PCR, nPNA and NB were calculated, and the correlation between Kt/V and the nutritional parameters was evaluated. The Borah equation was used to calculate the nPNA. The data are reported as the mean plus or minus the standard error. All statistical comparisons were done with a paired t test, and two-way ANOVA for repeated measures was used to calculate correlations. A P <0.05 was considered significant. Mean total and residual Kt/V was 3.4+/-1.3 and 1.69+/-1.27, respectively; nPNA and PCR were 1.38+/-0.44 and 1.39+/-0.43 g/kg/day, daily protein intake (DPI) was 3.25+/-1.27 g/kg/day, and NB showed a value of 1.86+/-1.25 g/kg/day. A significant positive correlation was found between Kt/V and DPI, PCR, DPC and nPNA (all values P <0.0001), but no correlation was found between total and residual Kt/V vs. nitrogen balance ( P:ns). Total Kt/V showed a significant positive correlation with nPNA, but it did not show any correlation with nitrogen balance, suggesting that the relationship with nPNA is the result of a mathematical association calculated from the same variables.

Nutrition for the pediatric surgical patient: approach in the peri-operative period

Nutrition is essential for maintenance of physiologic homeostasis and growth. Hypermetabolic states lead to a depletion of body stores, with decreased immunocompetence and increased morbidity and mortality. The purpose of this paper is to provide an update regarding the provision of appropriate nutrition for the pediatric surgical patient, emphasizing the preoperative and postoperative periods. Modern nutritional support for the surgical patient comprises numerous stages, including assessment of nutritional status, nutritional requirements, and nutritional therapy. Nutritional assessment is performed utilizing the clinical history, clinical examination, anthropometry, and biochemical evaluation. Anthropometric parameters include body weight, height, arm and head circumference, and skinfold thickness measurements. The biochemical evaluation is conducted using determinations of plasma levels of proteins, including album, pre-albumin, transferrin, and retinol-binding protein. These parameters are subject to error and are influenced by the rapid changes in body composition in the peri-operative period. Nutritional therapy includes enteral and/or parenteral nutrition. Enteral feeding is the first choice for nutritional therapy. If enteral feeding is not indicated, parenteral nutrition must be utilized. In all cases, an individualized, adequate diet (enteral formula or parenteral solution) is obligatory to decrease the occurrence of overfeeding and its undesirable consequences.

Accuracy of an indirect calorimeter for mechanically ventilated infants and children: the influence of low rates of gas exchange and varying FIO2

OBJECTIVE

To test the accuracy and validity of the Deltatrac II MBM-200 metabolic monitor for use in mechanically ventilated infants and children in the pediatric intensive care unit.

DESIGN

Laboratory validation of an indirect calorimeter with a ventilated lung model. The influence of low tidal volumes and low levels of oxygen consumption (V(O2)) and carbon dioxide production (V(CO2)) in combination with different levels of inspired oxygen concentrations (F(IO2)) was investigated.

SETTING

University research laboratory.

SUBJECTS

Low tidal volumes were provided with two intermittent flow types of ventilators, a Servo 300 and a Servo 900C.

INTERVENTIONS

A butane flame with a V(O2) approximating 20 mL/min and 40 mL/min was ventilated. To investigate the effect of different levels of F(IO2) on the accuracy of V(O2), V(CO2), and respiratory quotient (RQ), measurements were performed at F(IO2) target values of 0.25, 0.40, and 0.60.

MEASUREMENTS AND MAIN RESULTS

No significant differences were found between the ventilators regarding V(O2), V(CO2), and RQ measurements. The mean deviation of V(O2) increased significantly with increasing F(IO2) to -7.98% with a V(O2) of 21.0 mL/min and to -8.46% with a V(O2) of 38.9 mL/min (F(IO2), 0.558) with a variability (2 SD) of +/- 4.86% and +/- 6.82%, respectively. The mean deviation and variability of V(CO2) in all tests remained within 8%. The mean deviation of RQ increased significantly with increasing F(IO2) to 5.5% with a V(O2) of 21.0 mL/min and to 5.69% with a V(O2) of 38.9 mL/min (F(IO2), 0.558) with a variability (2 SD) of +/- 5.62% and +/- 5.76%, respectively. The minute to minute delivered F(IO2) fluctuated significantly when increasing the level of F(IO2).

CONCLUSIONS

The Deltatrac II MBM-200 metabolic monitor appears accurate for low levels of V(O2) and V(CO2) during mechanical ventilation with F(IO2) levels up to 0.390. With increasing F(IO2) to 0.558, the increase in deviation of V(O2) for single measurements can be of clinical relevance for mechanically ventilated infants and children. The increased fluctuation of delivered F(IO2) on higher levels of F(IO2) is likely the cause of the inaccuracy.

Energy expenditure and substrate utilization in mechanically ventilated children

The objective of the study was to determine the value of indirect calorimetry and nitrogen balance (N balance) in order to evaluate the current feeding protocols of mechanically ventilated children. The study was designed as a cross-sectional prospective study. In 36 mechanically ventilated children energy expenditure was measured by indirect calorimetry, and total urinary nitrogen excretion (TUN) was determined. Substrate utilization and respiratory quotient (RQ) were calculated from the measured values of oxygen consumption (VO2), carbon dioxide production (VCO2), and TUN. The RQ was compared with the RQ of the macronutrients administered (RQmacr) according to the modified criteria of Lusk. In results, the total measured energy expenditure (TMEE) showed a wide variation (range 155-272 kJ.kg-1.d-1). The N balance was positive in 20 and negative in 16 patients. The ratio of caloric intake/TMEE was significantly higher in patients with a positive N balance (1.50 +/- 0.06) as compared with those with a negative N balance (0.8 +/- 0.1, P < 0.001). There was a significant relationship between the difference of RQ-RQmacr versus the ratio caloric intake/TMEE (r = 0.72, P < 0.001). Carbohydrate and fat utilization were not significantly different in patients with a positive or negative N balance. Protein utilization was significantly higher in those patients with a negative N balance. We concluded that measurement of TMEE with indirect calorimetry results in accurate determination of energy needs in critically ill mechanically ventilated children. Feeding according to or in excess of the TMEE is correlated with a positive N balance. A combination of the RQ and the RQmacr can be helpful in differentiating under- or overfeeding.

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.

Evolution of the nutritional support pattern in pediatric intensive care

OBJECTIVES

To evaluate patterns of usage and monitoring of nutritional support in a Pediatric ICU of a teaching hospital and the role of an education program in nutritional support given throughout the resident physician training.

DESIGN

In a historical cohort study, records from children who received nutritional support during the year 1992 were analyzed. Thereafter a continuing education program in Nutritional Support was conveyed to the residents. In a second phase of the study, the same parameters were reevaluated in children who received nutritional support throughout the year 1995.

SETTING

Pediatric Intensive Care Unit of Department of Pediatrics, Escola Paulista de Medicina.

PATIENTS

All the children who were given nutritional support during a period of five days or more. Based on this criteria 37 children were selected for the first phase of this study, and 35 for the second one.

INTERVENTION

The education program included theoretical lectures about basic themes of nutritional support and journal article reading sessions. It was given to successive groups of residents on a weekly schedule.

MEASUREMENTS

Daily records of fluid, protein, caloric and micronutrient supply, nutritional assessment and metabolic monitoring.

RESULTS

In the first phase of the study, an exclusively parenteral route was utilized for 80.5%, and a digestive route 19.5% of the time period. Nutritional assessment was performed on 3 children; no patient had the nutritional goals set. The nitrogen to nonprotein calories ratio and the vitamin supply were inadequate, whilst the supply of trace elements was adequate except for zinc. Nutritional monitoring was performed on almost all patients but without uniformity. In the second phase, the exclusive parenteral route was used for 69.7% and the digestive route for 30.3% of the time period; no significant increase in the use of the digestive route was detected. The nonprotein calories to nitrogen ratio and micronutrient supply were adequate. The frequency of nutritional assessment increased, but deficiency in nutritional monitoring and infrequent enteral feeding were still detected.

CONCLUSION

There were deficiencies in the implementation of nutritional support, which were partially corrected in the second phase of the study by the training of the residents. Reinforcement of the education program, which should be applied to the whole medical staff, and the organization of a multidisciplinary team in charge of coordinating the provision of nutritional support are suggested.

Relationship of metabolic indexes to postoperative mortality in surgical infants

Acute injury is known to evoke a metabolic stress response, characterized by cytokine release and reprioritization of hepatic protein synthesis to increase acute phase proteins at the expense of visceral proteins. The impact of these evolving, stress-induced, perioperative metabolic changes on clinical outcome in surgical infants has not yet been determined. The cytokine (tumor necrosis factor [TNF]), acute phase protein (C-reactive protein [CRP]), and visceral protein (prealbumin [PA]) responses to acute metabolic stress were evaluated in 41 infants (average age, 47 days) preoperatively and on postoperative days 1 through 7 (POD 1 to 7) following major surgery. Infants were retrospectively grouped according to whether they survived (group 1) or died within 30 days of surgery (group 2). Peak CRP values in the postoperative period were also included for both groups. Peak CRP levels (14.9 +/- 5.5 v 8.1 +/- 5.7 mg/dL) were significantly increased (P = .0056) and preoperative prealbumin levels (6.0 +/- 2.7 v 11.0 +/- 5.2 mg/dL) were significantly decreased (P = .0005) in group 2 (nonsurvivors) compared with group 1 (survivors). Though serum TNF levels were substantially increased in nonsurvivors compared with survivors, both preoperatively (16.5 +/- 35.2 v 0.6 +/- 2.6 pg/mL) and on POD 1 (3.6 +/- 6.8 v 0.6 +/- 2.7 pg/mL), these values did not reach statistical significance (P > .05). The most significant difference (P = .0001) was observed in persistently depressed late (POD 4 to 7) prealbumin levels in nonsurvivors relative to survivors (5.3 +/- 3.1 v 10.5 +/- 4.3 mg/dL), suggesting an increased risk of poor outcome if acute metabolic stress had not abated by this time.(ABSTRACT TRUNCATED AT 250 WORDS)