Impaired fat utilization in parenterally fed low-birth-weight infants suffering from sepsis

Hypertriglyceridemia in Preterm Infants

Preterm and critically ill infants are at risk for hypertriglyceridemia (HTG). Common risk factors for HTG include prematurity, intravenous lipid emulsion dose and oil composition, reduced lipoprotein lipase activity, fetal growth restriction, sepsis, and renal failure. Despite these risk factors, clinicians lack a universally agreed upon definition for HTG and evidence-based approach to HTG management. This review provides a detailed overview of triglyceride and intravenous lipid emulsion metabolism and how this relates to specific HTG risk factors, along with some practical considerations for managing HTG in the neonatal population.

Intravenous lipids for preterm infants: a review

Extremely low birth weight infants (ELBW) are born at a time when the fetus is undergoing rapid intrauterine brain and body growth. Continuation of this growth in the first several weeks postnatally during the time these infants are on ventilator support and receiving critical care is often a challenge. These infants are usually highly stressed and at risk for catabolism. Parenteral nutrition is needed in these infants because most cannot meet the majority of their nutritional needs using the enteral route. Despite adoption of a more aggressive approach with amino acid infusions, there still appears to be a reluctance to use early intravenous lipids. This is based on several dogmas that suggest that lipid infusions may be associated with the development or exacerbation of lung disease, displace bilirubin from albumin, exacerbate sepsis, and cause CNS injury and thrombocytopena. Several recent reviews have focused on intravenous nutrition for premature neonate, but very little exists that provides a comprehensive review of intravenous lipid for very low birth and other critically ill neonates. Here, we would like to provide a brief basic overview, of lipid biochemistry and metabolism of lipids, especially as they pertain to the preterm infant, discuss the origin of some of the current clinical practices, and provide a review of the literature, that can be used as a basis for revising clinical care, and provide some clarity in this controversial area, where clinical care is often based more on tradition and dogma than science.

Analysis of risk factors for lipid intolerance of intravenous fat emulsion in very low birth weight infants

In order to prevent fatty acid deficiency and to supply enough energy, intravenous fat emulsion is necessary for parenteral nutrition in preterm neonates. However, parenteral administration of intravenous fat emulsion can induce lipid intolerance. The purpose of this study was to analyze risk factors for lipid intolerance in very low birth weight infants. This retrospective study included 80 preterm neonates whose birth weight was less than 1,500 g. Subjects were divided into 2 categories: those with a serum triglyceride level of ≥ 200 mg/dl (n = 33, 41%) and those with a serum triglyceride level of < 200 mg/dl (n = 47, 59%). We conducted logistic regression analysis using variables which were significant in univariate analysis. All statistical analyses were processed in SPSS version 19.0. Four risk factors for lipid intolerance were obtained through analysis of the electronic medical record. Lipid intolerance occurred more frequently in neonates with sepsis; those with a birth weight less than 1,000 g; those who was administered intravenous fat emulsion more than 2.6 g/kg/day; and those whose gestational age was less than 28 weeks. It is suggested that serum triglyceride levels should be closely monitored to prevent lipid intolerance in preterm neonates with the aforementioned characteristics.

Unbound free fatty acids from preterm infants treated with intralipid decouples unbound from total bilirubin potentially making phototherapy ineffective

Extremely low birth weight (ELBW; <1,000 g) infants have poor outcomes, often compromised by bilirubin neurotoxicity. We measured unbound bilirubin (Bf) and unbound free fatty acid (FFAu) levels in 5 ELBW infants in a trial examining the effects of pharmacologic ductal closure on infants treated with Intralipid infusion (3 g/kg/day). The levels for all infants (mean ± SD) were: total serum bilirubin (TSB) 4.6 ± 1.7 mg/dl, FFAu 376 ± 496 nM, and Bf 42 ± 30 nM. Of the 3 infants who died, 2 had TSB <5.9 mg/dl but FFAu >580 nM and Bf >75 nM. Multiple regression revealed a major effect on Bf levels due to FFAu, indicating that Intralipid elevated levels of FFAu and Bf. Indomethacin or ibuprofen reduced Bf levels, most likely by reducing FFAu levels through lipase inhibition. Because displacement of Bf by FFAu decouples Bf from TSB, phototherapy may not reduce the risk of bilirubin or FFAu toxicity in Intralipid-treated ELBW infants.

Dose of intravenous lipids and rate of bacterial clearance in preterm infants with blood stream infections

BACKGROUND

Intravenous lipid emulsion (IVLE) is an integral part of the total parenteral nutrition (TPN) regimen in neonates. The use of IVLE during sepsis is the subject of controversy because it may interfere with phagocytosis of microbes by macrophages and may lead to significant hypertriglyceridemia.

OBJECTIVE

This paper aims to study the rate of clearance of bacteria in relation to dose of IVLE administered to preterm infants with blood stream infections (BSIs).

METHODS

Preterm infants (mean gestational age ± SD, 32.0 ± 2.5 weeks) with culture-proven BSI and receiving TPN were randomized to two groups. The first group (n = 22) was given the usual dose of IVLE according to a standard protocol (starting from 0.5 g kg(-1) day(-1) and gradually increased by 1 g kg(-1) day(-1) to a maximum of 3.5 g kg(-1) day(-1)); in the second group (n = 20), IVLE were restricted at a dose of 1 g kg(-1) day(-1). Samples for blood cultures were withdrawn every 24 h until a negative culture was obtained. CRP was measured daily until its normalization. Serum triglycerides were monitored daily.

RESULTS

The rate of bacterial clearance was significantly more rapid in the restricted-dose IVLE group compared to the standard-dose group [72 (48-120) versus 144 (72-168) h, p = 0.001]. Daily weight increment was significantly greater in the standard-dose IVLE group compared to the restricted-dose IVLE group [25 (6.9-31.9) versus 0.9 (-3.3-11.7) g, p = 0.0001]. The duration of antibiotic use was significantly reduced in the restricted-dose IVLE group compared with the standard-dose IVLE group (10.0 ± 4.5 vs 14.9 ± 5.1 days; p = 0.003). The durations of TPN, mechanical ventilation, and hospitalization were not significantly different between groups.

CONCLUSIONS

Restriction of the dose of IVLE to 1 g kg(-1) day(-1) in preterm infants with BSI is associated with earlier negative blood cultures and reduced duration of antibiotic therapy but was associated with a lower daily weight increments.

Incidence of hypertriglyceridemia in critically ill neonates receiving lipid injectable emulsions in glass versus plastic containers: a retrospective analysis

OBJECTIVE

To evaluate plasma clearance of lipid injectable emulsions packaged in either glass or plastic containers in neonates from 2 7-month periods, 1 year apart.

STUDY DESIGN

Clinical records from June 1 to December 31, 2003 (glass [G] period) and the same months in 2004 (plastic [P] period) were assessed. Neonates who received lipid injectable emulsions were studied. Lipid container (glass vs plastic) was the independent variable.

RESULTS

Of the 197 patients studied, 122 (G, 50/81; P, 72/116) had evaluable triglyceride (TG) levels, for an overall rate of 62%. Only birth weight (G, 1.09 +/- 0.32 kg vs P, 1.23 +/- .45 kg) and birth length (G, 36.4 +/- 3.5 cm vs P, 37.9 +/- 3.5 cm) were significantly different between the 2 groups (P = .047 and .028, respectively). There were no differences in the day of life on which lipid injection was started, the lipid dose, or the timing of TG measurements. The incidence of hypertriglyceridemia was significantly higher in the P period (G, 3/50 vs P, 19/72; P = .004).

CONCLUSIONS

Administration of the same lipid formulation in plastic bags compared with glass containers is associated with higher rates of hypertriglyceridemia. The poorer clearance of lipids could be due to a higher proportion of large-diameter fat globules in plastic bags compared with those in glass containers.

Effect of oestradiol and progesterone replacement on bronchopulmonary dysplasia in extremely preterm infants

OBJECTIVE

To study whether postnatal replacement of oestradiol and progesterone may help to prevent bronchopulmonary dysplasia (BPD).

METHODS

This randomised placebo-controlled double-blind study enrolled 83 infants of <29 weeks gestational age and 1000 g birth weight requiring mechanical ventilation within 12 h after birth. Oestradiol (2.5 mg/kg/day) and progesterone (22.5 mg/kg/day) were given by continuous intravenous infusion of a standard lipid emulsion (15 ml/kg/day) in the replacement group (ESTRA-PRO). The placebo group received the same lipid emulsion without oestradiol or progesterone. A replacement period of at least 2 weeks but not >4 weeks was strived for and defined as "according to protocol". The primary outcome variable was the incidence of BPD or death.

RESULTS

The median birth weight was 670 g (min-max 400-990 g) and the gestational age 25 weeks (23.1-28.1 weeks). The incidence of BPD or death was 48% in the placebo group and 44% in the ESTRA-PRO group (p = 0.38, one-sided testing, intention to treat analysis). In infants treated according to protocol, 32% (9 of 28) in the placebo group and 14% (3 of 21) in the ESTRA-PRO group developed BPD (p = 0.08).

CONCLUSION

Replacement of oestradiol and progesterone was not effective for prevention of BPD or death in extremely preterm born infants. Better-powered trials are needed to evaluate this new approach.

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.

Computer Assisted Total Parenteral Nutrition for Pre-term and Sick Term Neonates

INTRODUCTION

Over the past few years, the use of total parenteral nutrition (TPN) has been established for pre-term and sick term neonates. At 'IASO' Hospital, a series of protocols implemented through the use of a computer programme has been developed to assist in the time consuming task of prescribing and preparing TPN in neonates. The algorithms used for neonates of a different gestational age are based on the protocols created through screening of literature and personal experience. This is important because it heralds a uniformity of the prescription of TPN at IASO and other hospitals where these protocols have been implemented.

OBJECTIVE

The objective is to determine the extent of error occurrence of the manual method as opposed to the new computerized procedure of TPN formulation, and to assess the immediate benefits stemming from the computer programme's use, in terms of personnel time reduction. Furthermore, the usefulness of the automated compounder in the computer driven process of TPN solution formulation was also assessed.

SETTING

Gynaecology Hospital 'IASO'.

METHOD

For a period of 6 months, sick and prematurely born babies were included in the study. Calculations regarding the composition of TPN solutions were conducted both by computer and manually.

MAIN OUTCOME MEASURE

The time needed to complete the procedure and the results' accuracy were measured and compared.

RESULTS

Implementation of the protocols into practice via this computer programme has been found to reduce the time spent by the physician and the pharmacist on TPN solution preparation, but the most important contribution is the virtual elimination (no errors in computerized calculation) of errors in the complex task of prescribing and formulating TPN solutions. For example, the average time taken to prepare the individual TPN solutions was 5.2 min while the computerized procedure took 15.4 min.

CONCLUSION

Use of this system can optimize pharmacists' and physicians' work and help prevent prescription and preparation errors.

Tyrosine nitration of carnitine palmitoyl transferase I during endotoxaemia in suckling rats

Heart carnitine palmitoyl transferase I (CPTI) is inhibited in vivo during endotoxaemia and in vitro by peroxynitrite but the biochemical basis of this inhibition is not known. The aim of this study was to determine which isoform of CPT I is inhibited during endotoxaemia and whether the inhibition is due to increased tyrosine nitration. Cardiac mitochondria were isolated from endotoxaemic suckling rats. To determine whether M- or L-CPTI was inhibited, we carried out titrations with DNP-etomoxir-CoA. Slopes of the titration curves with DNP-etomoxir-CoA were no different between control and endotoxaemia, suggesting that M-CPTI was specifically inhibited. Immunoprecipitation was carried out using an anti-nitrotyrosine antibody. Immunoprecipitated proteins were identified by Western blotting with L- and M-CPTI specific antibodies. L-CPTI was nitrated both in control and in 2- and 6-h endotoxaemia mitochondria but there was no significant difference in the level of nitration. M-CPTI was also nitrated in control mitochondria but nitration was significantly increased at both 2- and 6-h endotoxaemia. Either 10 mM 3-nitrotyrosine plus 40 microg nitrated-albumin or 0.5 M dithionite, during immunoprecipitation, greatly decreased immunopositivity for M- and L-CPTI on WB. M-CPTI appears to be a novel target for peroxynitrite during endotoxaemia, which would alter myocardial substrate selection.

Metabolic effects of infection and postnatal steroids

Optimal development of the newborn depends on rapid accretion of substrate in the neonatal period, particularly in the premature infant. Steroids and infection not only induce catabolism, but associated endogenous responses reprioritize crucial substrate to restore homeostasis. The result is a protein/energy deficit and concomitant delay in growth and development. Innovative feeding strategies and novel therapies are needed to reduce the impact of catabolism in this population.

Early aggressive nutrition in preterm infants

Increasingly, neonatologists are realizing that current feeding practices for preterm infants are insufficient to produce reasonable rates of growth, and earlier and larger quantities of both parenteral and enteral feeding should be provided to these infants. Unfortunately, there is very little outcome data to recommend any particular nutritional strategy to achieve better growth. Instead, the rationale for feeding regimens in many nurseries has been quite variably extrapolated from animal data and human studies conducted in gestationally more mature and/or stable neonates. Additionally, there are no well-controlled, prospective studies that validate any nutritional regimen for the very preterm and or sick, unstable neonate. The goal of this review is to present available data to help define the risks and benefits of early parenteral and enteral nutrition, particularly in very preterm neonates, concluding with a more aggressive approach to feeding these infants than has been customary practice.

13C breath tests: visions and realities

Breath tests have been used in research laboratories for over 25 y. Originally, the tests were based on the use of (14)C, rather than on the nonradioactive isotope, (13)C. When (13)C became widely available at a reasonable cost, research groups in the United States and Europe developed methodologies to measure (13)C abundance in samples of CO(2). The tests used a variety of substrates and measured pancreatic function, fat absorption, bacterial overgrowth and P(450) mixed-function oxidase. Thus far, the only test to be approved by the Food and Drug Administration is the (13)C-urea breath test. This manuscript describes the process by which approval is gained, and indicates the steps necessary for other tests to receive Food and Drug Administration approval.

Lipid clearance and total parenteral nutrition: the importance of monitoring plasma lipids

Lipid provides two major advantages for total parenteral nutrition (TPN). First, it provides essential fatty acids, thus avoiding essential fatty acid deficiency, and secondly, it is a useful energy source, providing 9 kcal/g. However, we describe a patient who had TPN containing Intralipid, where problems of lipid clearance developed. We also review the literature of lipid clearance problems in TPN patients and suggest ways by which such problems can be managed. We suggest that patients taking TPN should have their plasma lipids (triacylglycerols) measured before and during TPN initiation. This is particularly important in patients who are at high risk of impaired fat clearance, such as those who are hyperlipidemic, diabetic, septic, or with impaired renal or hepatic function, or those who are critically ill.

Intravenous nutrition and postnatal growth of the micropremie

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

Metabolism of parenterally administered fat emulsions in the rat: studies of fatty acid oxidation with 1-13C- and 8-13C-labelled triolein

To reassess the hypothesis that fatty acid catabolism occurs to completion via beta-oxidation, male Sprague-Dawley rats receiving continuous total parenteral nutrition (TPN) including 43% energy as fat were infused with [1-(13)C]- or [8-(13)C]triolein. Expired CO2 was collected continuously for 4 h and its 13C:12C ratio determined by isotope-ratio mass spectrometry. Bicarbonate retention was also assessed over 4 h by infusion of NaH14CO3 and measurement of the expired 14CO2. A possible loss of label from [8-(13)C]oleic acid from the citric acid cycle via labelled acetyl-CoA without oxidation to CO2 was assessed by infusing further animals with acetate labelled with 14C either at C atoms 1 or 2 and determination of its conversion to expired 14CO2. At isotopic steady state, 63.2 (SE 1.6)% (n 8) of the infused [1-(14)C]acetate and 46.0 (SE 1.2)% (n 8) of [2-(14)C]acetate was recovered as expired 14CO2. After correction for bicarbonate retention and non-oxidative isotope loss, 37.3 (SE 1.2)% (n 20) of the [1-(13)C]triolein was found to have been oxidized, whereas 32.6 (SE 1.0)% (n 20) of the [8-(13)C]triolein was oxidized (P < or = 0.01). The lower oxidation of the C atom at position 8 of oleic acid than that at position 1 indicates incomplete oxidative breakdown of the fatty acid after entering beta-oxidation.

Effect of lipid emulsion on IL-2 production by mononuclear cells of newborn infants and adults

The in vitro effect of a lipid emulsion (intralipid) on interleukin-2 (IL-2) production by cord blood mononuclear cells (CBMC) of preterm and term newborn infants was examined and compared to that of peripheral blood mononuclear cells (PBMC) of adults. Intralipid, added at concentrations accepted in clinical practice, caused a dose-dependent inhibition of IL-2 activity tested by bioassay. IL-2 levels, tested by radioimmunoassay (RIA), were found to be reduced only in supernatants derived from CBMC of term infants and not in those derived from MC of preterm infants or adults. The capacity of the IL-2 dependent cell line CTLL-2 to respond to IL-2 was abolished in the presence of intralipid, suggesting an interference with the binding of IL-2 to its receptor on these cells. It is conceivable that administration of intralipid to preterm infants may interfere with the binding of IL-2 to the specific receptors on their activated lymphocytes, with a possible subsequent suppression of their immune response.

Early postoperative lipid administration after neonatal surgery

The ability of neonates to eliminate and utilize lipid emulsions after surgery was investigated in 12 patients. All were subjected to major surgery within 29 h of birth. All neonates were given 10% glucose iv intraoperatively. Six patients continued with 10% glucose iv for 24 h postoperatively and 6 patients received a combination of 5% glucose and soy bean emulsion (Intralipid 20%). Both regimes provided equal amounts of fluid and energy. Blood glucose, lactate, triglycerides, free fatty acids, fractions of fatty acids in triglycerides, 3-hydroxybutyrate and arterial blood gases were measured at predetermined intervals throughout this period. Administration of a lipid emulsion early after neonatal surgery was well tolerated and utilized, with some latency. Concentrations of triglycerides, free fatty acids and 3-hydroxybutyrate were higher in the lipid group, but no accumulation of these substances was found. Palmitinic and linoleic acid were also higher in the lipid group.

Nutrition considerations in the neonatal extracorporeal life support patient

Extracorporeal life support (ECLS) is a type of heart-lung bypass commonly used to support neonates with life-threatening respiratory or cardiac failure. These patients are among the most critically ill patients in the neonatal intensive care unit and are at significant nutritional risk. Unfortunately, there is a paucity of literature regarding guidelines for nutrition support of the neonatal ECLS patient. The purpose of this article is to provide an overview of the indications, techniques, and complications of ECLS and to address the approach to nutrition support of these patients. Emphasis will be placed on issues unique to the neonatal ECLS patient.

Introduction of intravenous lipid administration on the first day of life in the very low birth weight neonate

OBJECTIVE

To investigate lipid tolerance in sick, ventilator-dependent, very low birth weight infants from the first day of life and the effects of early introduction of intravenously administered lipid (IVL) on glucose homeostasis.

METHOD

Twenty-nine infants in the neonatal intensive care unit with birth weight less than 1500 gm received isocaloric, isonitrogenous parenteral feedings from day 1 with either IVL, 1 gm/kg from day 1 to 3 gm/kg from day 4 (group I; n = 16), or IVL added only from day 8 (group II; n = 13). Possible adverse clinical effects were monitored. Blood metabolites, nonesterified fatty acids, serum triglycerides, and insulin levels were determined daily. Arterial blood gases were measured and changes in partial pressures of oxygen and of carbon dioxide in arterial blood were compared between the two groups.

RESULTS

Early lipid infusion did not appear to have deleterious effects on blood gas tensions or to increase respiratory morbidity. The incidence of other adverse clinical effects that may be associated with IVL was not increased by earlier introduction of lipid. Serum lipid values were comparable to those of preterm infants receiving IVL at a later postnatal age. Blood glucose concentrations were higher in group II (mean, 7.50 (SEM 0.43) mmol/L) than in group I (mean, 6.01 (SEM 0.28) mmol/L; p less than 0.05). There was no evidence of increased gluconeogenesis in infants in group I and no correlation between blood glucose concentrations and serum nonesterified fatty acid concentrations.

CONCLUSION

When given infusion rates not exceeding 0.15 gm/kg/hr, sick, very low birth weight infants can tolerate IVL with stepwise dose increases from the first day of life without an increased incidence of possible adverse effects.

Low-fat, high-carbohydrate diets improve wound healing and increase protein levels in surgically stressed rats

The specific effects of omega 3 and omega 6 polyunsaturated fatty acids on wound healing, nutrition status, or immune function are controversial. Therefore, we investigated the effects of fatty acid supplementation on wound healing and nitrogen retention in a surgically stressed rat model. Male Sprague-Dawley rats (weighing 250 g) were placed into three isocaloric, isonitrogenous feeding groups (controls [standard Vivonex]; 30% safflower oil [omega 6]; or 30% fish oil [omega 3]) for 8 days prior to receiving subcutaneous vascular graft wound cylinders in their dorsal midline. Nitrogen balance was monitored daily. Wounds healed for 10 days, animals were then euthanized, serum was drawn, and wound cylinders were harvested for analyses. The low-fat, high-carbohydrate control group had higher serum albumin levels at 10 days than either fatty acid-supplemented group (3.5 +/- 0.4 g/dL v 2.9 +/- 0.3 g/dL and 2.7 +/- 0.2 g/dL, omega 3 and omega 6, respectively; both P less than .05) and had better nitrogen balance (8.6 +/- 0.8 mg N/d v -2.6 +/- 0.9 mg N/d and 0.8 +/- 1.2 mg N/d, omega 3 and omega 6, respectively; both P less than .05). They also had better healed wounds at 10 days (450 +/- 290 micrograms 5-hydroxyproline [OHP]/cm of wound cylinder v 150 +/- 40 micrograms OHP/cm and 145 +/- 90 micrograms OHP/cm, omega 3 and omega 6, respectively). Surgically stressed rats had higher protein levels, better nitrogen balance, and improved wound healing when fed a diet high in carbohydrates and low in fat.

Lipid tolerance in the very low birth weight infant on intravenous and enteral feedings

Nutrition is of critical importance to very low birth weight (VLBW) survival. Intravenous (iv) lipid tolerance has been studied using a soybean or safflower-based lipid emulsion. We studied lipid levels in a group of VLBW infants on both intravenous lipids (soybean-safflower emulsion) and on enteral feedings (24 cal/oz premature formula). Levels were obtained on 1, 2, and 3 g/kg/day of iv lipid and after 3 and 10 days of feeding. Triglyceride (TG) and free fatty acid (FFA) proved the most sensitive indicator of both iv and enteral tolerance. The higher the lipid dose, the more likely there would be elevated lipid levels, especially FFA. Mean lipid levels for the group of enteral-fed infants were normal. Comparison of lipid levels on iv to those on enteral feedings showed significant differences in trough iv levels of TG compared to preprandial TG. FFAs tended to be significantly higher on iv feedings. Monitoring lipid levels on iv and enteral feedings is appropriate to document tolerance.