Parenteral nutrition and oxidant stress in the newborn: A narrative review.

There is strong evidence that oxidant molecules from various sources contaminate solutions of parenteral nutrition following interactions between the mixture of nutrients and some of the environmental conditions encountered in clinical practice. The continuous infusion of these organic and nonorganic peroxides provided us with a unique opportunity to study in cells, in vascular and animal models, the mechanisms involved in the deleterious reactions of oxidation in premature infants. Potential clinical impacts of peroxides infused with TPN include: a redox imbalance, vasoactive responses, thrombosis of intravenous catheters, TPN-related hepatobiliary complications, bronchopulmonary dysplasia and mortality. This is a narrative review of published data.

Determination of the concentration scaling law of the scattering coefficient of water solutions of Intralipid at 832 nm by comparison between collimated detection measurements and Monte Carlo simulations.

BACKGROUND AND OBJECTIVES: Intralipid (IP) is a scatterer extensively used in the building of phantoms for Biomedical Optics measurements. Recently, deviations from the linearity have been shown for the concentration scaling law of the scattering coefficient of IP water solutions at visible wavelengths. In this work this scaling law was determined at 832 nm. STUDY DESIGN/MATERIALS AND METHODS: Space resolved transmittance measurements of a laser beam at 832 nm through water solutions of IP and ink were performed and compared with the corresponding results of Monte Carlo simulations. RESULTS: The comparison provides a quadratic dependence of mu'(s) on the volume-to-volume scatterer concentration, C(IP), in the range of C(IP) values (0.0024

Simple peak shift analysis of time-of-flight data with a slow instrumental response function.

Analysis of time-of-flight (TOF) data is sometimes limited by the instrumental response function, and optical parameters are extracted from the observed response curve by several mathematical methods, such as deconvolution. In contrast to this, we demonstrate that a method using shifts of the peak time of the response curve with different source-detector separations can yield the average path length of the light traveling in a tissue-like sample without deconvolution. In addition, combining the intensity information allows us to separate the scattering and absorption coefficients. This simple method is more robust in signal-to-noise ratio than the moment analysis, which also does not require the deconvolution procedure, because the peak position is not significantly dependent on the baseline fluctuation and the contamination of the scattering. The analysis is demonstrated by TOF measurements of an Intralipid solution at 800 nm, and is applied to the measurements at 1.29 microm, where the temporal response of photomultiplier tubes is not sufficiently good.

The mode of delivery of parenteral multivitamins influences nutrient handling in an animal model of total parenteral nutrition.

BACKGROUND: Very low birthweight preterm infants receive early total parenteral nutrition (TPN) to optimize protein balance. Adding multivitamins (MVP) to the lipid emulsion (MVP+LIP) rather than to the amino acid+dextrose moiety of TPN (AA+MVP) limits the effects of light exposure on lipid peroxidation and vitamin loss. AIM: Compare the effects of the mode of delivery of MVP on nutrient handling and indices of oxidant stress. METHODS: Three-day old guinea pig pups were assigned to TPN containing MVP+amino acids+dextrose+heparin and electrolytes, with lipids provided separately (AA+MVP). Solutions were light exposed (LE, n = 8) or light protected (LP, n = 9). In a further group (n = 7), MVP was co-administered with the lipid moiety and light exposed (LIP+MVP). Variables measured in urine (creatinine, nitrogen, vitamin C) and in liver (protein, glutathione, isoprostane, vitamins A, E, C) were compared by ANOVA. RESULTS: Urinary nitrogen and vitamin C were higher (P<0.05) during LE, while hepatic levels of vitamin C were higher (P<0.05) with LIP+MVP. These results were not related to total peroxide levels in TPN or to markers of oxidant stress. CONCLUSION. Co-administration of MVP with lipid or light protected amino acids offers comparable beneficial effects on nitrogen and vitamin C metabolism.

Emission and absorption properties of indocyanine green in Intralipid solution.

Emission and absorption properties of indocyanine green (ICG) in Intralipid solution have been investigated. The study is focused on relatively low ICG concentration at a range of 0 to 20 microM. A diffusion model was used to analyze the emission properties of ICG solution at different concentrations. In the low-concentration region, the emission strength increases with the concentration of ICG, while in the high-concentration region, the emission decreases with the concentration. In general, a maximum of emission strength exists and its position (concentration) depends on the wavelength of the excitation light, the distance between the source and the detector, and the sample geometry and size. A so-called "inner-cell-effect" and re-absorption of emission photons are found to contribute to the decay of emission strength. Also, in the concentration range of 0 to 2 microM, ICG solution always has a higher absorption coefficient at wavelength 830 nm than that at 660 nm, which is quite different from the ICG in water case.

Measurement and analysis of light distribution in intralipid-10% at 650 nm.

A method for measuring the distributions of light in the biological tissue phantom Intralipid by use of an optical fiber is presented and measurements of distributions of light in Intralipid-10% suspensions at 650 nm are described. This approach is complementary to that in which an optical fiber with an isotropic tip detects the distribution of light in tissue phantoms. The characteristics of the distance-dependent intensity of scattering light in different directions were revealed by the experimental results; the effects of the optical parameters and of the radius of the incident beam on the distributions of light in tissue phantoms were given; and the experimental results were analyzed by the diffusion theory. These studies will help in further understanding of the scattering characteristics of tissue.

Lipid peroxide and hydrogen peroxide formation in parenteral nutrition solutions containing multivitamins.

BACKGROUND: Infusion of parenteral solutions containing peroxides may be detrimental to premature infants. Intralipid frequently contains lipid peroxides and undergoes further peroxidation when exposed to light. Peroxidation is inhibited by ascorbate, and we have proposed that administration of peroxides could be minimized by mixing multivitamins with the Intralipid. In contrast, others have reported that multivitamins generate peroxides and have advised against mixing them with lipid. Our objective was to assess whether light-dependent reactions in parenteral solutions containing MVI Pediatric (MVIP) generate hydrogen peroxide and establish whether addition of multivitamins to Intralipid is beneficial or detrimental. RESULTS: We were unable to make accurate peroxide measurements in MVIP using the ferrous oxidation of xylenol orange (FOX) assay, even though others have used it for this purpose, because of interference by ascorbate. Therefore oxygen release on adding catalase was measured to assay for hydrogen peroxide. Freshly reconstituted solutions contained 250 to 500 micromol/L hydrogen peroxide, and this increased dramatically in ambient light. This is presumably due to light-dependent, riboflavin-catalyzed reduction of oxygen by ascorbic acid. The rate of peroxide generation was less for MVIP diluted in Intralipid than in dextrose solution. CONCLUSIONS: Taken together with our previous findings, we conclude that multivitamins protect Intralipid against lipid peroxidation, but light-dependent hydrogen peroxide production and ascorbate loss occur. These latter changes are less than for multivitamins in other total parenteral nutrition solutions, so there is an advantage in mixing multivitamins with Intralipid. However, prevention of ascorbate loss and hydrogen peroxide formation in any multivitamin solution requires protection of the delivery system from light.

The photodegradation of vitamins A and E in parenteral nutrition mixtures during infusion.

BACKGROUND & AIMS: Vitamins A and E are the most light-sensitive vitamins. Vitamin A is degraded by photolysis, while vitamin E degrades by photo-oxidation. The composition of the parenteral nutrition mixture and the container could therefore influence degradation during daylight administration. The aim of this study was therefore to determine the influence of fat emulsion and the type of bag on the photo-degradation of vitamins A and E in Parenteral Nutrition (PN) mixtures during simulated infusion in daylight. METHODS: Representative adult PN mixtures, with and without fat emulsion, were prepared. Samples for analysis were taken from infusates and each bag during simulated infusion. Degradation of vitamins A and E was determined by stability-indicating HPLC analysis. RESULTS: Results indicated that vitamin A loss proceeded rapidly during infusion, resulting in up to 80% loss in 6 hours, even with light protection of the bag. The presence of fat emulsion did not provide significant light protection. Vitamin E degradation was substantial if mixtures were prepared in EVA bags but was largely prevented if PN mixtures were compounded and stored in multi-layered bags. CONCLUSIONS: It is recommended that all PN bags should be light-protected during infusion in daylight. The use of multi-layered bags will prevent vitamin E losses during infusion.

Oxidation of parenteral lipid emulsion by ambient and phototherapy lights: potential toxicity of routine parenteral feeding.

Vitamin E can be a prooxidant in isolated lipoprotein suspensions. Because lipid emulsions used in parenteral nutrition are lipoprotein-like suspensions rich in polyunsaturated fatty acids and vitamin E, we hypothesized that vitamin E may act as a prooxidant in lipid emulsions, as it is in lipoprotein suspensions. We therefore exposed an intravenously administered lipid emulsion (Intralipid) to a single spotlight commonly used in the treatment of neonatal jaundice, and measured the formation of triglyceride hydroperoxides by using high-performance liquid chromatography with postcolumn chemiluminescence detection. Concentrations of these hydroperoxides in different batches of fresh intralipid were usually approximately 10 mumol/L but increased up to 60 times after exposure to phototherapy light for a period of 24 hours, even though significant amounts of vitamin E were present at the end of the exposure. Triglyceride hydroperoxides were formed during phototherapy light exposure whether the intralipid was in plastic tubing used routinely for infusion or in glass containers. Ambient light also caused significant peroxidation of the formula lipids, although to a much lesser extent than observed with phototherapy light. For infants in the neonatal intensive care unit who were receiving intralipid but not phototherapy, solutions being infused at the end of 24 hours contained a mean of 40 mumol/L hydroperoxides. For infants receiving phototherapy, the mean was 97 mumol/L. Phototherapy light-induced formation of triglyceride hydroperoxides was prevented by covering the intralipid with aluminum foil or supplementation with sodium ascorbate before light exposure. We conclude that intralipid is highly susceptible to oxidation and that elevated levels of oxidized lipids can be formed during its clinical use, especially when intralipid infusion is combined with phototherapy. Because lipid hydroperoxides are cytotoxic and can cause adverse effects, inadvertent infusion of rancid intralipid may add to the numerous problems encountered by premature neonates.