RESUMEN
To evaluate the efficacy of adding a volume reservoir to reduce variability in ventilator-induced fluctuation in inspired oxygen concentration (FiO2) and to reduce oxygen consumption measurement error, we evaluated two ventilators (Puritan-Bennett 7200 and Bear 2) at three inspired oxygen concentrations ranging from 35% to 60%. Continuous sampling of oxygen concentration was conducted for each ventilator. The maximum variability in oxygen concentration was recorded at each minute and oxygen consumption error sensitivity was calculated for both ventilators at three different oxygen concentrations, with and without the use of a baffled 3-L reservoir placed into the inspiratory circuit between the ventilator and test lung. The use of a baffled 3-L reservoir reduced oxygen consumption error sensitivity with the Puritan-Bennett 7200 ventilator at all three oxygen concentrations (p < 0.01). Similar results were found with the Bear 2 ventilator except at the highest FiO2, at which oxygen consumption error sensitivity was not altered. Use of a baffled volume reservoir can significantly reduce ventilator-dependent errors in measuring oxygen consumption via indirect calorimetry. However, when the FiO2 is widely variable, the reservoir is not helpful in reducing error at higher FiO2 concentrations.
Asunto(s)
Consumo de Oxígeno/fisiología , Oxígeno/análisis , Ventiladores Mecánicos/normas , Calorimetría Indirecta , Metabolismo Energético/fisiología , Humanos , MétodosRESUMEN
Very low birth weight infants have little storage of hepatic retinol and are, therefore, highly dependent upon an exogenous supply. The recent association between low serum retinol level and bronchopulmonary dysplasia and the persistently low serum levels of retinol during total parenteral nutrition prompted a prospective study to evaluate serial changes in serum retinol levels during 1 month of total parenteral nutrition (retinol dose 455 micrograms/d) and again during 1 month of total enteral feeding (retinol dose 200 to 300 micrograms/d) in the same infants. Infants were divided into two groups. Group 1 consisted of infants weighing less than 1,000 g (n = 24) and group 2 consisted of infants weighing 1,000 to 1,500 g (n = 17). Although initial mean levels of retinol were similar in both groups (14.8 +/- 0.9 and 13.5 +/- 0.7 micrograms/dL), there was wide variation between infants. In group 1 infants, there was a significant (P less than .01) decline in retinol level by the second week of life (to 9.2 +/- 1 micrograms/dL), which persisted during total parenteral nutrition, but increased to 13.4 +/- 2 after 1 week of enteral feeding. This level was maintained throughout enteral feeding. In group 2 infants, there was no significant change in serum retinol level throughout the study. During total parenteral nutrition, several infants had retinol levels below 10 micrograms/dL, a level associated with signs of retinol deficiency in older children. Because losses of retinol are known to occur in smaller volume total parenteral nutrition solutions, it was speculated that losses of retinol in our patients were due to retinol losses in the total parenteral nutrition delivery system.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Nutrición Enteral , Emulsiones Grasas Intravenosas , Recién Nacido de Bajo Peso/sangre , Nutrición Parenteral Total , Vitamina A/sangre , Estabilidad de Medicamentos , Alimentos Formulados , Humanos , Alimentos Infantiles , Recién Nacido , Estudios Prospectivos , Vitamina A/administración & dosificaciónRESUMEN
The effect of chemically-induced acute diabetes mellitus on the intestinal transport of 5-methyltetrahydrofolate, the predominate dietary form of folate, was examined using an in vivo perfusion technique in unanesthetized restrained rats and the in vitro everted sac technique. Diabetes was induced by an intraperitoneal injection of 70 mg/kg of streptozotocin. Transport experiments were performed 4 days after the induction of diabetes and results were compared to appropriate controls. The amount of 5-methyltetrahydrofolate transported in vivo and in vitro was significantly higher in the diabetic group as compared to controls. The kinetic parameters of the in vitro transport of 5-methyltetrahydrofolate showed an increase in the Vmax value for the diabetic rats as compared to controls (1.52 and 0.80 nmol/g initial tissue wet wt/30 min, respectively) with no change in apparent Kt (1.62 and 1.80 microM, respectively). These observations suggest that the increase in the transport of 5-methyltetrahydrofolate observed in the diabetic rats is due to an increase in the activity and/or the number, but not the affinity, of the transport carriers involved. We conclude that chemically-induced acute diabetes mellitus is associated with an enhancement in folate absorption.
Asunto(s)
Diabetes Mellitus Experimental/metabolismo , Absorción Intestinal , Yeyuno/metabolismo , Tetrahidrofolatos/metabolismo , Animales , Técnicas In Vitro , Mucosa Intestinal/metabolismo , Cinética , Masculino , Ratas , Ratas EndogámicasRESUMEN
This study represents the first attempt to evaluate the response to the only intravenous vitamin preparation (MVI Pediatric) for infants and children receiving total parenteral nutrition. Eighteen preterm infants (group 1), 26 term infants and children receiving total parenteral nutrition for 2 to 4 weeks (group 2A), and eight infants and children receiving total parenteral nutrition for 3 to 6 months (group 2B) were studied. Term gestation infants and children up to 11 years of age received daily vitamin doses that approximated the 1974 Recommended Dietary Allowances and coincided with the 1975 American Medical Association Nutrition Advisory Group total parenteral nutrition dosage guidelines for children weighing more than 10 kg. Preterm infants received 65% of these dosages. RBC transketolase (vitamin B1), glutathione reductase (B2), and glutamic oxaloacetic transaminase (B6) activities were maintained at normal levels, and niacin levels were maintained within the reference range (7.1 +/- 0.32 micrograms/mL) in all study patients. Pantothenate, biotin, and ascorbate were maintained at reference levels in groups 2A and 2B. In group 1, ascorbic acid was increased significantly during treatment from 1.53 +/- 0.16 to 3.60 by seven days and to 2.54 +/- 0.62 by day 28 of treatment (reference normals = 0.99 +/- 0.1 mg/dL). RBC folate was maintained within the reference range of 411 +/- 76 pg/mL; however, pantothenate and biotin levels increased significantly to more than 2 SD above reference values during treatment, and vitamin B12 levels, which were above the reference range initially, were maintained at more than 2 SD above the reference range throughout treatment. The elevation in vitamin B12 was seen in both group 1 and 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Recien Nacido Prematuro , Nutrición Parenteral Total , Nutrición Parenteral , Vitaminas/administración & dosificación , Niño , Preescolar , Eritrocitos/enzimología , Humanos , Lactante , Recién Nacido , Compuestos Orgánicos , Vitaminas/sangreRESUMEN
This study represents the first attempt to evaluate the American Medical Association Nutrition Advisory Group (NAG) recommendations for intravenous vitamin A, D, and E dosages for infants and children. Patients studied included 18 preterm infants (group 1) and 26 term infants and children (group 2A) receiving total parenteral nutrition for 2 to 4 weeks and eight infants and children receiving total parenteral nutrition for 3 to 6 months (group 2B). Term gestation infants and children up to 11 years of age all received the same dosages (those that were recommended by the NAG for children weighing more than 10 kg). Preterm infants received 65% of these doses. In group 1, cord blood alpha-tocopherol levels were less than 0.22 mg/dL in seven preterm infants (reference value = 0.29 +/- 0.04), but mean levels increased to 1.65 +/- 0.17 mg/dL after four days of treatment. Eight infants consistently received additional vitamin E orally (80 to 150 mg daily), and their levels increased to 2.18 +/- 0.26 mg/dL by four days of study and to 3.49 +/- 0.57 mg/dL after 3 weeks. Oral supplementation in the preterm infants appeared to be unnecessary because intravenous vitamins alone maintained levels above 1.1 mg/dL. In group 2, alpha-tocopherol levels were maintained within the reference range. Patients receiving lipid emulsions containing substantial quantities of alpha-tocopherol had significantly higher blood levels than patients receiving lipid emulsions containing little alpha-tocopherol (P less than .01). Mean 25-OH vitamin D levels were maintained above or within the reference range in groups 2A and 2B.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Recien Nacido Prematuro , Nutrición Parenteral Total , Vitaminas/administración & dosificación , Niño , Preescolar , Emulsiones Grasas Intravenosas/administración & dosificación , Humanos , Hidroxicolecalciferoles/sangre , Lactante , Recién Nacido , Necesidades Nutricionales , Compuestos Orgánicos , Vitamina A/sangre , Vitamina E/sangre , Vitaminas/sangreRESUMEN
Recent observations suggest an inverse relationship between folic acid intake and zinc nutriture and indicate an interaction between folic acid and zinc at the intestinal level. To define that interaction, we designed in vivo and in vitro transport studies in which folic acid transport in the presence of zinc, as well as zinc transport in the presence of folic acid was examined. These studies show that zinc transport is significantly decreased when folate is present in the intestinal lumen. Similarly folic acid transport is significantly decreased with the presence of zinc. To determine whether this intestinal inhibition is secondary to zinc and folate-forming complexes, charcoal-binding studies were performed. These studies indicate that zinc and folate from complexes at pH 2.0, but that at pH 6.0, these complexes dissolve. Therefore, our studies suggest that under normal physiological conditions a mutual inhibition between folate and zinc exists at the site of intestinal transport.
Asunto(s)
Cloruros , Ácido Fólico/metabolismo , Absorción Intestinal/efectos de los fármacos , Compuestos de Zinc , Zinc/metabolismo , Animales , Radioisótopos de Carbono , Carbón Orgánico , Ácido Fólico/farmacología , Concentración de Iones de Hidrógeno , Mucosa Intestinal/metabolismo , Yeyuno/metabolismo , Ratas , Zinc/farmacología , Radioisótopos de ZincRESUMEN
Developmental aspects of the intestinal transport of 5-methyltetrahydrofolate (5-CH3H4-PteGlu) were studied in suckling (14-day-old), weanling (22-day-old), and adult (90-day-old) rats by use of the intestinal everted-sac technique. Mucosal-to-serosal transport of 0.5 microM 5-CH3H4PteGlu was linear with time for 40-min incubation and occurred at a rate of 0.035, 0.032, and 0.010 nmol X g initial tissue wet wt-1 X min-1 for suckling, weanling, and adult rats, respectively. The transport of 5-CH3H4PteGlu in all age groups was pH dependent (maximal at pH 6) and was higher in the jejunum than in the ileum. In all age groups the transport of 5-CH3H4PteGlu occurred by an active carrier-mediated system. The system was saturable; energy, temperature, and Na dependent; inhibited by structural analogues; and capable of accumulating the substrate against a concentration gradient. Kinetic parameters of the transport process, however, showed some difference. A progressive decrease in Vmax was observed from suckling to weanling to adult rats (5.1, 3.7, and 0.8 nmol X g initial tissue wet wt-1 X 30 min-1, respectively), while apparent Kt was similar (2.2, 1.73, and 1.79 microM, respectively). This study demonstrates that the transport system of 5-CH3H4PteGlu in the rat is fully developed at the suckling age. The results also suggest that the activity and/or the number, but not the affinity, of the transport carriers decrease with maturation.