Protein turnover, lipolysis, and endogenous hormonal secretion in critically ill children

Vitamin C Deficiency in Critically Ill Children: Prospective Observational Cohort Study

OBJECTIVES

To evaluate the presence of vitamin C deficiency in critically ill children admitted to the PICU.

DESIGN

Single-center prospective observational cohort study.

SETTING

A 28-bed PICU and a pediatric outpatient sedation room of a tertiary-care teaching hospital.

PATIENTS

Two pediatric patient groups 0-21 years old were studied: a PICU group and a group receiving deep sedation for elective outpatient procedures (noncritical care group).

INTERVENTIONS

Vitamin C level was drawn for the PICU group within 24 hours of admission. Vitamin C level was drawn prior to start of deep sedation for the noncritical group.

MEASUREMENT AND MAIN RESULTS

Vitamin C deficiency was present in 11/60 (18%) in the PICU group and 0/21 (0%) of the noncritical group (p < 0.05).

CONCLUSIONS

Vitamin C deficiency was prevalent in our patients admitted to PICU.

Less Is More?-A Feasibility Study of Fluid Strategy in Critically Ill Children With Acute Respiratory Tract Infection

Background: Fluid overload is common in critically ill children and is associated with adverse outcome. Therefore, restricting fluid intake may be beneficial. This study aims to study the feasibility of a randomized controlled trial (RCT) comparing a conservative to a standard, more liberal, strategy of fluid management in mechanically ventilated pediatric patients with acute respiratory tract infection (ARTI). Methods: This is a feasibility study in a single, tertiary referral pediatric intensive care unit (PICU). Twenty-three children receiving mechanical ventilation for ARTI, without ongoing hemodynamic support, admitted to the PICU of the Emma Children's Hospital/Amsterdam UMC between 2016 and 2018 were included. Patients were randomized to a conservative (<70% of normal intake) or standard (>85% of normal intake) fluid strategy, which was kept throughout the period of mechanical ventilation. Results: Primary endpoints were adherence to fluid strategy and safety parameters such as calorie and protein intake. Secondary outcomes were cumulative fluid intake (CFI) and cumulative fluid balance (CFB) on day 3. In the conservative group, in 75% of the mechanical ventilation days patients achieved their target fluid intake. Median [25th-75th percentiles] calorie intake over all mechanical ventilation days was 67.9 [51.5-74.0] kcal/kg/day in the conservative vs. 67.2 [58.0-75.2] kcal/kg/day in the standard group (p = 0.878). Protein intake was 1.6 [1.3-1.8] gr protein/kg in the conservative and 1.5 [1.2-1.7] gr protein/kg in the standard group (p = 0.598). No adverse effects on hemodynamics or electrolyte imbalances were noted. Mean (±SD) CFI on day 3 was 262.3 (±58.9) ml/kg in the conservative group vs. 360.5 (±52.6) ml/kg in the standard fluid group (p < 0.001), which did not result in a lower CFB. Conclusions: A conservative fluid strategy in mechanically ventilated children with ARTI seems feasible, without limiting metabolic needs. However, in our study a conservative fluid strategy surprisingly did not reduce the degree of fluid overload. This study aids the design and sample size calculation of a future larger multicenter RCT, in which we need to redefine the target fluid strategy, possibly by even further fluid restriction and early initiation of active diuresis. Clinical Trial Registration: ClinicalTrials.gov, identifier: NCT02989051.

Association between enteral macronutrient delivery and inflammatory response in critically ill children

BACKGROUND AND AIMS

An important goal of nutrition support in paediatric critical illness is minimising catabolism. While focussing on providing full energy requirements, macronutrient balance is often neglected. Studies suggest that there is interplay between nutrition and inflammation. We aimed to assess the amount of enteral macronutrients delivered compared to estimated requirements, and the association between delivered macronutrients and systemic inflammation in critically ill children.

METHOD

We prospectively evaluated energy and macronutrient intake in critically ill children who required at least 72 h of mechanical ventilation. Data on enteral energy and macronutrient intake was collected and expressed as a percentage of the estimated requirements. Circulating levels of inflammatory cytokines were measured by ELISA and association assessed with delivery of macronutrients from the previous 24 h.

RESULTS

A total of 87 children (0-16 years) were included in this study. By day 3 the median (IQR) intake of energy, fat, carbohydrate (CHO) and protein were 75% (50-103), 85% (43-120), 63% (42-102) and 45% (23-65) respectively. We have also shown that delivery of enteral fat and protein was associated with elevation in the levels of tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6).

CONCLUSION

The inflammatory response in critically ill children is influenced by the amount of enteral fat and protein delivered. Our data suggests that within the feed delivered, fat is often higher than protein and CHO. It is crucial to take into account the proportion of macronutrients required and not only aim to achieve the energy goal.

Nutrition and metabolism in the rehabilitative phase of recovery in burn children: a review of clinical and research findings in a speciality pediatric burn hospital

During the rehabilitation phase of burn injury, patient care transitions from critical care medicine to restorative treatment strategies that encompass physical and occupational therapies, nutrition repletion, and psychosocial support for community reintegration. As pediatric burn patients undergo rehabilitation, nutrition assessment remains ongoing to define nutritional status and any alterations in metabolism that may take place. For some, a persistent hypermetabolic state appears evident, and weight loss may continue. The severity and duration however varies among patients. Many patients enter their rehabilitative phase with visible lean body mass depletion, and the focus of nutritional therapy for them shifts to replenishing nutritional status, while supporting rehabilitative efforts. Over the past decade, we have conducted studies on energy and protein metabolism, body composition, including bone mineralization, and general wellness in over 130 patients to better understand changes in metabolism and nutritional status during the rehabilitative phase of recovery. This abstract summarizes our findings.

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.

Challenge of predicting resting energy expenditure in children undergoing surgery for congenital heart disease

OBJECTIVES

To determine pre- and postoperative predictors of energy expenditure in children with congenital heart disease requiring open heart surgery; and to compare measured resting energy expenditure with current predictive equations.

DESIGN

Prospective resting energy expenditure data were collected, using indirect calorimetry, for ventilated children admitted consecutively to the pediatric intensive care unit after surgery for congenital heart disease. A 30-min steady-state measurement was performed in suitable patients. Resting energy expenditure was compared to pre- and postoperative clinical variables, and to predicted energy expenditure, using currently used predictive equations.

SETTING

Pediatric intensive care unit at the Royal Brompton Hospital, London.

PATIENTS

Children ventilated in the pediatric intensive care unit post surgery for congenital heart disease.

INTERVENTIONS

Measurement of energy expenditure by indirect calorimetry.

MEASUREMENTS AND MAIN RESULTS

Twenty-one mechanically ventilated children (n = 17 boys, 4 girls) were enrolled in the study. Mean +/- sd measured resting energy expenditure was 67.8 +/- 15.4 kcal/kg/day. Most children had inadequate delivery of nutrients compared with actual requirements. Cardiopulmonary bypass had a significant influence on energy expenditure after surgery; in patients who underwent cardiopulmonary bypass during surgery, mean resting energy expenditure was 73.6 +/- 14.45 kcal/kg/day vs. 58.3 +/- 10.29 kcal/kg/day in patients undergoing nonbypass surgery. Children who were malnourished preoperatively had greater resting energy expenditure postoperatively. There was also a significant difference between measured energy expenditure and the Schofield (p = .006), World Health Organization (p = .002), and pediatric intensive care unit-specific formula (p < .0001). However, energy expenditure or a relative energy deficit in the early postoperative period was not associated with severity or duration of organ dysfunction.

CONCLUSIONS

Poor nutritional status preoperatively and cardiopulmonary bypass were associated with a greater energy expenditure post cardiac surgery. None of the current predictive equations predicted energy requirements within acceptable clinical accuracy.

Metabolic effects of intensive insulin therapy in critically ill patients

Our aim was to investigate the effects of glycemic control and insulin concentration on lipolysis, glucose, and protein metabolism in critically ill medical patients. For our methods, the patients were studied twice. In study 1, blood glucose (BG) concentrations were maintained between 7 and 9 mmol/l with intravenous insulin. After study 1, patients entered one of four protocols for 48 h until study 2: low-insulin high-glucose (LIHG; variable insulin, BG of 7-9 mmol/l), low-insulin low-glucose (LILG; variable insulin of BG 4-6 mmol/l), high-insulin high-glucose [HIHG; insulin (2.0 mU . kg(-1).min(-1) plus insulin requirement from study 1), BG of 7-9 mmol/l], or high-insulin low-glucose [HILG; insulin (2.0 mU.kg(-1).min(-1) plus insulin requirement from study 1), BG of 4-6 mmol/l]. Age-matched healthy control subjects received two-step euglycemic hyperinsulinemic clamps achieving insulin levels similar to the LI and HI groups. In our results, whole body proteolysis was higher in patients in study 1 (P < 0.006) compared with control subjects at comparable insulin concentrations and was reduced with LI (P < 0.01) and HI (P = 0.001) in control subjects but not in patients. Endogenous glucose production rate (R(a)), glucose disposal, and lipolysis were not different in all patients in study 1 compared with control subjects at comparable insulin concentrations. Glucose R(a) and lipolysis did not change in any of the study 2 patient groups. HI increased glucose disposal in the patients (HIHG, P = 0.001; HILG, P = 0.07 vs. study 1), but this was less than in controls receiving HI (P < 0.03). In conclusion, low-dose intravenous insulin administered to maintain BG between 7-9 mmol/l is sufficient to limit lipolysis and endogenous glucose R(a) and increase glucose R(d). Neither hyperinsulinemia nor normoglycemia had any protein-sparing effect.

Transthyretin (aka Prealbumin): why is it part of TPN labs?

AS IN OTHER NICUs, OUR PATIENTS on total parenteral nutrition (TPN) have routine labs done for monitoring. In our unit, these labs include electrolytes, hemoglobin, triglycerides, liver function studies, and transthyretin (TTR) (still called prealbumin). In polling the other neonatal nurse practitioners, I realized that none of us completely understood the utility of following the TTR level. That was the impetus for this column.

Synthesis of long-chain polyunsaturated fatty acids in preterm newborns fed formula with long-chain polyunsaturated fatty acids

BACKGROUND

Docosahexaenoic acid (DHA) and arachidonic acid (AA) are long-chain polyunsaturated fatty acids (LCPs) that play pivotal roles in growth and neurodevelopment.

OBJECTIVE

We aimed to quantify the synthesis of LCPs in preterm infants fed infant formula containing LCPs.

DESIGN

Twenty-two preterm infants were randomly assigned to either the no-LCP group (fed formula without LCPs; n = 11) or the LCP group (fed formula with LCPs; n = 11). Dietary LCPs had higher (13)C content than did the endogenously synthesized LCPs, which were derived from linoleic and alpha-linolenic acids. The (13)C content of major selected plasma fatty acids was measured by using gas chromatography-isotope ratio mass spectrometry at birth and at age 1, 3, and 7 mo. Absolute LCP synthesis and the percentage of LCP synthesis relative to dietary intake were calculated.

RESULTS

Percentage AA synthesis was 67.2 +/- 7.8%, 35.9 +/- 9.8%, and 29.0 +/- 10.3%, and that of DHA was 41.7 +/- 14.9%, 10.5 +/- 8.1%, and 7.4 +/- 6.2% at 1, 3, and 7 mo old, respectively. Absolute AA synthesis was 26.7 +/- 4.2, 14.4 +/- 3.9, and 11.6 +/- 4.1 mg x kg(-1) x d(-1) and that of DHA was 12.6 +/- 4.5, 3.2 +/- 2.5, and 2.3 +/- 1.9 mg x kg(-1) . d(-1) at 1, 3, and 7 mo old, respectively. AA and DHA synthesis decreased significantly (P < 0.01) with time, and AA synthesis was significantly (P < 0.01) greater than DHA synthesis.

CONCLUSIONS

By this novel approach, we measured endogenous LCP synthesis in infants receiving dietary LCPs over long periods. By age 7 mo, LCP synthesis was dramatically lower in preterm infants fed LCPs.

Insulin therapy in the pediatric intensive care unit

BACKGROUND & AIMS

Hyperglycemia is a major risk factor for increased morbidity and mortality in the intensive care unit. Insulin therapy has emerged in adult intensive care units and several pediatric studies are currently being conducted. This review discusses hyperglycemia and the effects of insulin on metabolic and non-metabolic pathways, with a focus on pediatric critical illness.

METHODS

A PubMed search was performed by using the following keywords and limits (("hyperglycemia"[MeSH terms] or ("insulin resistance"[MeSH major topic]) and ("critical care"[MeSH terms] or "critical illness"[MeSH terms])) in different combinations with ("metabolism"[MeSH terms] or "metabolic networks and pathways"[MeSH terms]) and ("outcome"[all fields]) and ("infant"[MeSH terms] or "child"[MeSH terms] or "adolescent"[MeSH terms]). Quality assessment of selected studies included clinical pertinence, publication in peer-reviewed journals, objectivity of measurements and techniques used to minimize bias. Reference lists of such studies were included.

RESULTS

The magnitude and duration of hyperglycemia are associated with increased morbidity and mortality in the pediatric intensive care unit (PICU), but prospective, randomized controlled studies with insulin therapy have not been published yet. Evidence concerning the mechanism and the effect of insulin on glucose and lipid metabolism in pediatric critical illness is scarce. More is known about the positive effect on protein homeostasis, especially in severely burned children. The effect in septic children is less clear and seems age dependent. Some non-metabolic properties of insulin such as the modulation of inflammation, endothelial dysfunction and coagulopathy have not been fully investigated in children.

CONCLUSION

Future studies on the effect of insulin on morbidity and mortality as well as on the mechanisms through which insulin exerts these effects are necessary in critically ill children. We propose these studies to be conducted under standardized conditions including precise definitions of hyperglycemia and rates of glucose intake.

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.

Insulin-like growth factor binding protein-1 and interleukin-6 are markers of fetal stress during parturition at term gestation

OBJECTIVE

Maintaining an adequate blood glucose level is essential for neuron integrity. The increased energy demand imposed on the fetus by the birth process in combination with a limited glucose production capacity therefore threatens brain function. It is logical to presume that mechanisms increasing glucose mobilization as well as decreasing peripheral glucose utilization has evolved to preserve brain function, even after complicated deliveries.

DESIGN

We studied umbilical cord levels of hormones involved in acute glucose regulation as well as insulin-like growth factor-I (IGF-I), modulating factors insulin-like growth factor binding protein (IGFBP)-1 and -3 as well as interleukin-6 (IL-6) in 149 infants born after different degrees of birth stress. We measured glucose, insulin, IGF-I, IGFBP-1, IGFBP-3, glucagon, growth hormone (GH), prolactin, adrenocorticotropin (ACTH), cortisol and IL-6 in umbilical cord blood of infants born at term gestation after: A) elective Cesarean-section (n = 37), B) normal delivery (n = 87) or C) complicated delivery (n = 25). All infants were of normal birth weight for gestational age. Arterial pH and lactate as well as S-100B, a marker of neuronal damage, were used as stress variables.

RESULTS

With increasing fetal stress, we found significant and generally progressive elevations in glucose, IGFBP-1, IL-6, ACTH, cortisol, glucagon, GH, prolactin and lactate. This was accompanied by significant decreases of IGF-I, insulin and arterial pH. S-100B and IGFBP-3 levels did not differ between groups. IGFBP-1 showed a significant positive correlation to IL-6 and lactate and a significant negative correlation to both IGF-I and arterial pH.

CONCLUSIONS

Increasing stress and energy demands during birth are accompanied by increasing fetal levels of glucose-mobilizing hormones in combination with depressed levels of insulin and IGF-I, despite increasing blood glucose. Furthermore, IGFBP-1 and IL-6 increase steeply, presumably aimed at diminishing insulin-like activity of IGF-I, thereby reducing peripheral glucose utilization. We believe that IGFBP-1 and IL-6 deserve evaluation as potential intrapartum indicators of fetuses at risk for asphyxia.

Pituitary function during severe and life-threatening illnesses

The catabolic state of prolonged critical illness is associated with a low activity of anterior pituitary functions. Before considering endocrine intervention in these conditions, a detailed understanding of the neuroendocrinology of the stress response is warranted. It is now clear that the acute phase and the later phase of critical illness behave differently from an endocrinological point of view. When the disease process becomes prolonged, there is a uniformly-reduced pulsatile secretion of anterior pituitary hormones with proportionally reduced concentrations of peripheral anabolic hormones. Apparently, there is a constant interaction between neuroendocrine and internal immunoregulatory mechanisms that assures the fine tuning of both the neuro-endocrine and the immune system, so that both are able to preserve homeostasis of patients during severe and life-threatening illnesses.

Hypoalbuminaemia in critically ill children: incidence, prognosis, and influence on the anion gap

AIMS

Hypoalbuminaemia has significance in adult critical illness as an independent predictor of mortality. In addition, the anion gap is predominantly due to the negative charge of albumin, thus hypoalbuminaemia may lead to its underestimation. We examine this phenomenon in critically ill children, documenting the incidence, early evolution, and prognosis of hypoalbuminaemia (<33 g/l), and quantify its influence on the anion gap.

METHODS

Prospective descriptive study of 134 critically ill children in the paediatric intensive care unit (ICU). Paired arterial blood samples were taken at ICU admission and 24 hours later, from which blood gases, electrolytes, and albumin were measured. The anion gap (including potassium) was calculated and then corrected for albumin using Figge's formula.

RESULTS

The incidence of admission hypoalbuminaemia was 57%, increasing to 76% at 24 hours. Neither admission hypoalbuminaemia, nor extreme hypoalbuminaemia (<20 g/l) predicted mortality; however, there was an association with increased median ICU stay (4.9 v 3.6 days). After correction for albumin the incidence of a raised anion gap (>18 mEq/l) increased from 28% to 44% in all samples (n = 263); this discrepancy was more pronounced in the 103 samples with metabolic acidosis (38% v 73%). Correction produced an average increase in the anion gap of 2.7 mEq/l (mean bias), with limits of agreement of +/-3.7 mEq/l.

CONCLUSION

Admission hypoalbuminaemia is common in critical illness, but is not an independent predictor of mortality. However, failure to correct the anion gap for albumin may underestimate the true anion gap, producing error in the interpretation of acid-base abnormalities. This may have treatment implications.

The role of visceral proteins in the nutritional assessment of intensive care unit patients

PURPOSE OF REVIEW

This review analyses the recently published literature focusing on nutritional assessment in intensive care unit patients. The metabolic response to nutritional intervention is difficult to evaluate in critically ill patients whose body weight is influenced largely by massive fluid administration or losses. Visceral protein plasma levels have been proposed for this purpose, because they reflect hepatic synthesis in response to nutrient supply. However, in acute inflammatory states, liver activity is converted to the synthesis of acute-phase response proteins, resulting in a dramatic drop in visceral proteins, despite nutritional support.

RECENT FINDINGS

The data regarding visceral protein levels were examined in relation to nutritional supplementation, and compared with other nutritional parameters and clinical outcomes. Transthyretin and retinol-binding protein levels seem to be the most sensitive to nutritional intervention. They are also the earliest to rise at the decrease of acute-phase protein levels, therefore representing a good index of the reversing reprioritization of hepatic protein synthesis. An inconsistent relationship was found between visceral protein plasma levels and clinical outcome in intensive care unit patients, probably because of the difficulty in demonstrating clearly a beneficial effect of nutritional supplementation in highly catabolic conditions.

SUMMARY

In the acute stage of critical illness, the bi-weekly measurement of transthyretin together with acute-phase response protein plasma levels seems to be a 'window' on the metabolic condition (anabolism versus catabolism). However, only in the presence of stable inflammatory parameters do transthyretin levels reflect the adequacy of nutritional coverage.