Total parenteral nutrition in the newborn: impact of the quality of infused energy on nitrogen metabolism.

To separate the respective influence of the level and source of infused energy on nitrogen metabolism, 32 studies were performed in 16 appropriate-for-gestational-age newborn infants (birth weight 2150 +/- 115 g, means +/- SEM). In a cross-over design, each patient received two 6-d periods of isocaloric and isonitrogenous (450 mg.kg-1.d-1) infusions, differing only by the source of calories (high or low fat intakes). Half of the patients were studied at 60 kcal.kg-1.d-1, the other half at 80 kcal.kg-1.d-1. Nitrogen balance, urinary 3-methylhistidine excretion, glycemia, and insulin were compared. The results suggest that for an intravenous energy intake ranging from 60 to 80 kcal.kg-1.d-1, glucose and fat provide an equivalent nitrogen sparing effect in the newborn infant. At an energy level covering maintenance requirements, it is the infant's clinical condition rather than the source of energy which affects most the magnitude of amino acids participation in energy metabolism.

Total parenteral nutrition in the newborn: amino acids-energy interrelationships.

As part of an ongoing study on the influence of intravenous glucose and fat on nitrogen metabolism we evaluated the relationship between the source of infused energy and plasma amino acid levels. Thirty-two studies were performed in 16 appropriate-for-gestational-age newborn infants (birth weight, 2150 +/- 115 g; means +/- SEM). In a crossover design each patient received two 6-d periods of isocaloric and isonitrogenous infusions, differing only by the source of calories (high or low fat intakes). For an energy intake of 80 kcal.kg-1.d-1 (335 kJ.kg-1.d-1) there was a significant hypoaminoacidemia (2338 +/- 185 vs 2937 +/- 196 mumol/L, high fat vs low fat) under the high-glucose intake. These data suggest that above an energy intake of 60 kcal.kg-1.d-1 (251 kJ.kg-1.d-1) there is a threshold at which changes in plasma amino acid levels are triggered by variations in the source of infused energy. Careful examination of all variables, including energy sources, is essential when aminograms are compared.

Clinical and nutritional impacts of removing bisulfite from neonatal parenteral nutrition.

There is a general willingness to eliminate sulfites from the diet because of adverse reactions. Because little is known about the biological effects of these antioxidants in vivo, we compared clinical and nutritional parameters in newborn infants receiving two parenteral amino acid solutions containing either 300 mg/dl or no metabisulfite. The primary objective was to verify whether decreasing the sulfur content of parenteral nutrition would diminish the calciuria of newborn infants. In a crossover design, 18 newborn infants received two regimens differing only in their metabisulfite content. Nitrogen and mineral balances; clinical parameters such as mean heart and respiratory rates, body temperature, and transcutaneous PO2 and PCO2 (n = 7); and energy expenditure were similar in both regimens. Withdrawing bisulfites from the diet did not change calciuria, put an extra burden on the infant's metabolic adaptation, or cause short-term clinical repercussions.

Reliability of the twenty-four-hour nitrogen balance in parenterally fed newborn infants.

The reliability of shorter nitrogen balance determinations was evaluated in order to facilitate the nutritional assessment of parenterally fed infants. The intraindividual day-to-day variations of nitrogen intake, excretion, and retention were analyzed in 23 parenterally fed newborn infants (birth weight: 785-2630 g). Nitrogen retentions measured over 3 consecutive days were highly correlated (r = 0.90-0.96), and the reliability for a single 24-hr collection was estimated by r1 = 0.93. Nitrogen balance data obtained over a 24-hr period are reliable for the purpose of clinical investigations, provided the nutrient intake is constant.

Beneficial effect of coinfusing a lipid emulsion on venous patency.

The hypothesis that infused fat could prolong venous patency was tested in a paired crossover design. Parenterally fed newborn infants received, for a given level of energy, (60 vs 80 kcal/kg/day), two 6-day isocaloric and isonitrogenous (434 +/- 3.4 mg/kg/day, n = 32) regimens differing only by the fat intake (LF: 1.03 +/- 0.02, HF: 2.78 +/- 0.05 g/kg/day). Paired comparisons of osmolarities within isocaloric (60 or 80 kcal/kg/day) infusions showed that high fat regimens were associated with significantly lower osmolarities. A paired comparison of patency times showed that the drop in osmolarity produced by the high fat regimen at 60 kcal/kg/day led to a significantly longer venous patency time. The comparison of patency times between regimens (LF, 60 kcal/kg/day) and HF, 80 kcal/kg/day) with same osmolarities (702 mOsm/liter) and glucose intakes (11 g/kg/day) documented that the fat emulsion per se had a vascular protective effect. This observation demonstrates that the coinfusion of a lipid emulsion exerts a beneficial effect, whether biochemical or biophysical, on the vascular endothelium of peripheral veins.

Protecting solutions of parenteral nutrition from peroxidation.

BACKGROUND: Light exposure induces the generation of peroxides in solutions of total parenteral nutrition (TPN). Peroxide toxicity has been documented in cell, in tissue, and in isolated organs. To decrease the infused peroxide load and to protect the quality of the parenteral nutrients, we tested the photoprotective properties of different infusion sets. METHODS: Solutions of fat-free TPN and all-in-one total nutrient admixture (TNA) were run through sets of bags (clear and covered) and tubings (clear and colored: black, orange, and yellow) offering different levels of protection against light. Peroxide levels were determined by ferrous oxidation of xylenol orange, thiol functions by the 5,5,-dithiobis(2-nitrobenzoic acid) technique, and absorbance of tubings by spectroscopy. RESULTS: Protection of only the bag had little effect on peroxide generation. In fat-free TPN solutions kept in covered bags, peroxide concentrations were 1.5 to 2 times higher when run through clear compared with colored tubings. When exposed to phototherapy or in the presence of lipids, peroxides were two to three times higher with the clear compared with the black tubing; meanwhile, orange and yellow tubings offered varying levels of protection related to their light-absorbing properties. Colored tubings offered a greater protection against the disappearance of thiol functions. CONCLUSIONS: Covering bags and using orange and yellow tubings may be a practical solution to reduce infused peroxide loads from about 400 to 100 microM. This is especially relevant in patients with an immature or a compromised antioxidant capacity or when phototherapy or preparations of TNA are used.

Total parenteral nutrition in very low birth weight infants with Travasol 10% blend C.

Ten very low birth weight (VLBW) infants (birth weight: 994 +/- 66 g, gestational age: 27 +/- 0.5 wk) requiring total parenteral nutrition (TPN) were studied in order to evaluate their metabolic response to the amino acid solution Travasol 10% blend C. These patients received the solution at a constant rate, providing 2.61 +/- 0.02 g/kg/day of amino acids and 76 +/- 1 kcal/kg/day. Plasma amino acids analysis was performed after 4.6 +/- 0.3 day of infusion and compared to values reported previously with Travasol blend B. The new solution (blend C) showed a significantly lower (p less than 0.001) glycinemia (485 +/- 24 vs 993 +/- 69 mumol/liter), methioninemia (39 +/- 2 vs 114 +/- 12 mumol/liter) and phenylalaninemia (67 +/- 3 vs 92 +/- 5 mumol/liter) related to the lower intake of these amino acids. Despite the provision of 47.5 mmol/liter of serine with blend C no changes in plasma level (182 +/- 15 vs 196 +/- 41 mumol/liter) were noted. The increased molar arginine/glycine ratio (blend C: 0.48 vs blend B 0.22) could have contributed to keep ammoniemia within normal levels (55.1 +/- 4.2 mumol/liter). Wide variations in insulin response (9.9 to 26.4 microU/ml) allowed for a correlation between its plasma concentration and those of sensitive amino acids, underlining its role in protein metabolism. Despite the immaturity of the study population no short-term metabolic imbalance has been encountered with the Travasol blend C solution.

Classification of fatal occupational electrocutions.

The objective of this study was to describe fatal occupational electrocutions that occurred in Quebec between 1981 and 1988 and propose a classification suitable for setting up a prevention agenda. Of 63 fatalities, an investigation report was available in 57 (90.5%). They all occurred among males, 70.2% of whom were under the age of 35; 49.1% were performing a task related to the construction sector. A principal factor analysis allowed classification of 90.2% of the fatalities in two categories: victims assigned to electrical tasks indoors and those assigned to non-electrical tasks outdoors. The first group (56.5% of the cases) were electrocuted by direct contact with voltage less than 10 Kvolts and the second by the intermediary of a vector with voltage above 10 Kvolts. The identification of the two patterns of electrocutions provided an additional argument for shifting recommendations for prevention from educating the workers, to reducing the electrical hazards at the source.

[The importance of dietary sodium: the time has come for a public health intervention]. / L'apport alimentaire en sodium: le temps est venu pour une intervention de santé publique.

In recent years, many studies have been published regarding the link between sodium intake and high blood pressure. Canadian, American and WHO Guidelines on the treatment of hypertension all indicate salt reduction as an efficient non-pharmacologic recommendation. However, due to the lack of clear and specific Canadian legislation on food labelling, consumers are not able to make informed choices of food products on the basis of salt content. The time has come for public health experts to join this debate.

Fatal occupational injury rates: Quebec, 1981 through 1988.

OBJECTIVES: The purpose of the study was to estimate the death rates from occupational injuries in the province of Quebec for the period 1981 through 1988. METHODS: Worker's compensation files were used to ascertain numbers of deaths, which were used as the numerators in figuring the rates (it was estimated that these files reported 83% of the true number of deaths among men). Annual average estimates of the labor force were used as denominators. RESULTS: From 1981 through 1988, compensation was awarded for 1227 fatal work injuries. Among men (96% of the victims), rates declined from 1981 to 1988 (from 12.7 to 8.1 per 100,000); women's rates were stable (< or = 1.0 per 100,000). Compared with men, women had excess mortality from violent acts. Motor vehicle crashes accounted for 36% of all fatal injuries in 1984 and 1985 and declined thereafter. Fatal injury rates in forestry and mining rose to a 1987 maximum of 67.6 per 100,000. The construction sector had the largest number of deaths, despite a decline in rates from 1981 to 1988 (from 27.8 to 15.9 per 100,000). CONCLUSIONS: Except for construction and agriculture, reported fatal occupational injury rates in Quebec were similar to those in the United States. Motor vehicle crashes, falls, violent acts, and farming-related injuries were the most frequent causes of death.

Contribution of multivitamins, air, and light in the generation of peroxides in adult and neonatal parenteral nutrition solutions.

OBJECTIVE: To compare the concentrations of peroxides between adult and neonatal total parenteral nutrition (TPN) solutions in response to protection against inducers of peroxidation such as multivitamins and exposure to light or air. METHODS: Peroxide concentrations were measured in freshly prepared adult and neonatal solutions of fat-free TPN in four settings: with or without an air inlet, and protected or unprotected from ambient light. An oxygen washout was performed by exposing a fat-free neonatal TPN solution to a continuous flow of nitrogen. RESULTS: Globally, light was the main inducer of peroxides in adult and neonatal solutions. However, in adult solutions the concentration of peroxides remained <15 micromol/L, while in neonatal solutions the peroxide concentration was as high as 300 micromol/L in ambient light. Although the oxygen washout did prevent the generation of peroxides, avoiding air inlet was not as effective as was photoprotection in decreasing the important peroxide load in the neonatal TPN solution. CONCLUSIONS: The higher concentration of peroxides found in neonatal solutions compared with adult solutions is explained by the differences in nutrient composition between the two solutions. Contamination of parenteral solutions by air during compounding accounts for the photoinduced generation of peroxides in TPN solutions. It is more convenient to protect TPN solutions from light exposure after the admixture of the multivitamin solution than to avoid contact with oxygen.

Influence of energy substrates on respiratory gas exchange during conventional mechanical ventilation of preterm infants.

OBJECTIVE: The purpose of this study was to determine the optimal parenteral feeding regimen for infants with compromised respiratory function. METHODS: We studied the influence of varying the source of energy on respiratory gas exchange in 10 infants who were supported by mechanical ventilation and who received intravenous feedings. Two isoenergetic parenteral regimens were infused consecutively; the level of fat intake was varied inversely with that of glucose. Under similar ventilator settings, transcutaneous partial pressures of oxygen and carbon dioxide, as well as indirect calorimetry were measured during each regimen. RESULTS: Despite the higher carbon dioxide production during the glucose-rich regimen (8.9 +/- 0.7 vs 7.9 +/- 0.4 ml/kg per minute, p < 0.05 by analysis of variance), transcutaneous partial pressure of carbon dioxide remained unaffected, suggesting ventilatory compensation as documented by the increased (p < 0.002) alveolar ventilation. This was not associated with a detectable rise in oxygen consumption, but with a significant change in partial pressure of oxygen (77 +/- 5 vs 66 +/- 3 mm Hg, p < 0.05). CONCLUSIONS: Ventilator-dependent infants with early and mild bronchopulmonary dysplasia, who receive intravenous feedings of a moderate load of glucose-based energy, can compensate for enhanced carbon dioxide production by increasing their respiratory drive, with a beneficial effect on oxygenation compared with that observed when energy is derived from lipid-based solutions.

Role of the source of phosphate salt in improving the mineral balance of parenterally fed low birth weight infants.

Because the monobasic potassium phosphate salt (monobasic) improves the solubility of calcium and phosphorus in amino acid plus dextrose solutions, compared with the current mixtures of monobasic plus dibasic salts (dibasic), we tested the bioavailability and clinical effects of monobasic in 16 parenterally fed low birth weight infants at standard (n = 8) and high levels (n = 8) of mineral intakes. A constant infusion of macronutrients and vitamin D was provided in a crossover design of two four-day periods. With standard intakes of calcium (35 mg/kg/day, 0.9 mmol/kg/day) and phosphorus (30 mg/kg/day, 1 mmol/kg/day), there was no difference between monobasic and dibasic regimens on balance data or plasma biochemical monitoring (calcium, phosphorus, pH, carbon dioxide pressure, base excess, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin D). With the use of the monobasic regimen, the mineral intakes were doubled without precipitation in the infusate: calcium, 70 mg/kg/day (1.8 mmol/kg/day), and phosphorus, 55 mg/kg/day (1.7 mmol/kg/day). This led to increased apparent retention of both calcium (63 +/- 5 mg/kg/day, 1.58 +/- 0.12 mmol/kg/day) and phosphorus (52 +/- 4 mg/kg/day, 1.67 +/- 0.14 mmol/kg/day) compared with that for standard levels of mineral intake. The improvement of calcium-phosphorus balance was accompanied by more severe calciuria (9 +/- 2 mg/kg/day, 0.2 +/- 0.05 mmol/kg/day) and by metabolic compensation for an increased acid load. In addition to the possibility of exceeding the buffering capacity of the infant, this relative acidosis could also be evidence of improved bone mineralization.

[Comparison of the metabolic response of the premature child fed parenterally, and then with mother's milk of prematurity]. / Comparaison de la réponse métabolique du petit prématuré alimenté parentéralement, puis au lait maternel de prématurité.

The nitrogen retention and plasma amino acid concentration were determined in eight preterm infants (mean birth weight 970 +/- 130 g; mean gestational age 28 +/- 1 weeks) receiving successively total parenteral nutrition and their own mother's milk. The nitrogen retention during both regimens was comparable to the fetal accretion rate. Plasma amino acid concentrations were lower during the enteral phase of the study than during parenteral nutrition. The metabolic response of small preterm infants is related to the quality of amino acids as well as to the route of intake.

Effect of amino acid composition of parenteral solutions on nitrogen retention and metabolic response in very-low-birth weight infants.

To evaluate the influence of amino acid preparations on the metabolic response of parenterally fed immature newborn infants, nitrogen retention and plasma amino acid concentrations were compared in very-low-birth-weight infants given two parenteral regimens differing only by the composition of the infused amino acids (Travasol 10% blend B and Vamin 7%). The intakes of fluid, nitrogen, and calories were comparable. The nitrogen retention was 72% +/- 7% with Vamin and 65% +/- 6% with Travasol. The differences in plasma amino acid concentrations were consistent with the composition of the amino acid solutions. During the infusion of Vamin the increased intake of aromatic amino acids resulted in high plasma levels of tyrosine (256 +/- 233 mumol/L, range 67 to 894 mumol/L). The infusion of Travasol resulted in high plasma levels of methionine (114 +/- 39 mumol/L, range 53 to 260 mumol/L) and an elevated load of glycine, which was accompanied by an abnormally high urinary loss of this amino acid. Despite these metabolic imbalances, the growth rate over the whole study was adequate. These results emphasize the importance of the composition of amino acid solutions on the metabolic response of the very immature preterm infant.

Total parenteral nutrition in the newborn infant: energy substrates and respiratory gas exchange.

The hypothesis that a high-fat parenteral regimen was beneficial for respiratory gas exchanges, in comparison with a high-glucose regimen, was tested in a paired crossover design. Ten parenterally fed newborn infants with no respiratory problems received two 5-day isoenergetic and isonitrogenous regimens that differed in their nonprotein source of energy; the level of fat intake (low fat (LF) 1 gm.kg-1.day-1; high fat (HF) 3 gm.kg-1.day-1) varied inversely with that of glucose. Continuous transcutaneous PO2 (tcPO2) and PCO2 (tcPCO2), respiratory gas exchange (indirect calorimetry), and plasma arachidonate metabolites were measured at the end of each regimen. Oxygen consumption and resting energy expenditure were not affected by modification of the source of energy. However, carbon dioxide production (VCO2) was higher during LF than during HF (6.9 +/- 0.2 vs 6.2 +/- 0.1 ml.kg-1.min-1; p less than 0.01), as was the respiratory quotient (1.08 +/- 0.02 vs 0.96 +/- 0.02; p less than 0.001). Despite the differences in VCO2, the tcPCO2 was not affected, suggesting adequate pulmonary compensation during LF, as documented by the higher minute ventilation (160 +/- 7 vs 142 +/- 5 ml.kg-1.min-1; p less than 0.01). The lower tcPO2 during the HF regimen (73.8 +/- 2.8 vs 68.8 +/- 2.6 mm Hg; p less than 0.015) indicated a disturbance at the alveolocapillary level induced by the lipid emulsion. No differences were found in circulating levels of prostaglandins and thromboxanes. The substitution of glucose for lipid did not modify fat storage (2.1 +/- 0.3 vs 2.1 +/- 0.3 gm.kg-1.day-1). We conclude that the supposed beneficial effect of a fat emulsion on respiratory gas exchange is questionable.

Total parenteral nutrition in the newborn: energy substrates and plasma total fatty acids.

Carbohydrate and lipid intakes have both been found to modulate the metabolism of long-chain fatty acids. To define the respective influence of these two energy substrates on plasma fatty acid concentrations, 32 studies were performed in 16 parenterally fed newborn infants (mean +/- SEM, birth wt: 2.15 +/- 0.1 kg, age: 10 +/- 1 d). In a paired cross-over design, the infants received for a given level of energy (60 versus 80 kcal/kg/d) two 6-d isonitrogenous and isocaloric regimens constructed so that the level of fat intake, 1 or 3 g/kg/d varied inversely with that of glucose. Total plasma fatty acid levels did not reflect the composition of the emulsion and varied with energy substrates. Plasma levels of three fatty acids rose inversely to the lipid intake, during the high glucose regimen: 16:1w7, 20:3w9 biologic markers of essential fatty acid deficiency, and 20:3w6 a derivative of 18:2w6. Glucose intake could exert its influence on 20:3w9 and 20:3w6 via insulin, an activator of delta 6 desaturase. Both glucose and fat should be taken into account when evaluating plasma fatty acid profile.

Metabolic and clinical consequences of changing from high-glucose to high-fat regimens in parenterally fed newborn infants.

To evaluate the metabolic and clinical consequences of changing from high-glucose to high-fat regimens during initiation of parenteral nutrition, we performed 22 studies in 11 newborn infants (birth weight (mean +/- SD) 2.54 +/- 0.54 kg, gestational age 37 +/- 3 weeks, postnatal age 8 +/- 3 days) maintained in a constant thermal environment. In a paired design, two isoproteinic (2.4 +/- 0.2 gm/kg/day) and isocaloric (64 +/- 6 kcal/kg/day) regimens differing by source of energy (high glucose vs high lipid) were infused on consecutive days. Environmental and body temperatures were recorded during a 4-hour period, and 24-hour urinary excretions of catecholamines, nitrogen, and C peptide were measured. Despite constant incubator and average skin temperatures, the rectal and interscapular temperatures rose significantly when the high-glucose regimen was changed to a high-lipid regimen. The specific locations of these changes in body temperature suggested brown fat activation. A significant drop in nitrogen retention (63 +/- 9% vs 56 +/- 10%) during the lipid infusion could be further evidence of a metabolic adaptation to the rapid change in energy substrates.