Prediction of early tolerance to enteral feeding by measurement of superior mesenteric artery blood flow velocity: appropriate- versus small-for-gestational-age preterm infants.

AIM: To evaluate whether serial Doppler measurements of superior mesenteric artery blood flow velocity could predict early tolerance to enteral feeding in preterm infants. METHODS: In a prospective study, 54 healthy preterm neonates were assigned to one of the following groups: neonates with birthweight appropriate for gestational age (group 1), neonates small for gestational age without (group 2) and with prenatal haemodynamic disturbances (group 3). We studied Doppler blood flow velocity and resistance index before and after the first feed. RESULTS: Contrary to patients of group 3, infants in groups 1 and 2 showed a significant increase in blood flow velocity and a significant decrease in resistance index from the preprandial values after the first feed. At each postprandial time, we found significant differences in all velocity and resistance measurements between patients of group 3 and patients of both groups 1 and 2. In all patients, we found that the value of mean velocity measured 30 min after the first feed was the most predictive of early feed tolerance, with 95% sensitivity and 94% specificity when mean velocity >0.38 m/s. CONCLUSION: Small-for-gestational-age preterm infants with prenatal haemodynamic disturbances have an unusual intestinal haemodynamic response to the first feed. In the whole group of preterm infants, the value of mean velocity measured 30 min after the first feed is a good tool for the clinician in predicting early enteral feeding.

Redox status in very-low birth-weight newborns.

Inborn metabolic diseases, such as disorders in pyruvate metabolism, in gluconeogenesis or in the respiratory chain, may present with lactic acidosis in newborn infants. A simple tool to screen for the efficacy of mitochondrial oxidation reduction activity is the detection of the redox status through simultaneous measurements of plasma lactate, pyruvate and ketone bodies, which are strongly influenced by feeding and stress. We present the redox status values of 55 very-low birth-weight infants under different nutritional conditions. We were able to demonstrate that the redox status values are not dependent on the type of nutrition (oral feeding or continuous enteral nutrition). Instead we observed a strong difference between newborns with intrauterine growth retardation and newborns with appropriate growth. Newborns with intrauterine growth retardation show lower preprandial values of glucose and ketone bodies than newborns with appropriate weight, but higher levels of lactate and pyruvate; nevertheless the lactate/pyruvate and beta-hydroxybutyrate/acetoacetate ratios are normal. The results of the redox status study could suggest the reduced activity of gluconeogenesis and, probably, of beta-oxidation in very-low birth-weight newborns with intrauterine growth retardation.

Is breastfeeding really favoring early neonatal jaundice?

OBJECTIVE: The purpose of this study was to evaluate the development of significant hyperbilirubinemia in a large unselected newborn population in a metropolitan area with particular attention to the relationship between type of feeding and incidence of neonatal jaundice in the first week of life. STUDY DESIGN: A population of 2174 infants with gestational age >/=37 weeks was prospectively investigated during the first days of life. Total serum bilirubin determinations were performed on infants with jaundice. The following variables were studied: type of feeding, method of delivery, weight loss after birth in relationship to the type of feeding, and maternal and neonatal risk factors for jaundice. Statistical analyses were performed using the z test for parametric variables and the t test for nonparametric variables. In addition, the multiple logistic regression allows for the estimation of the role of the individual characteristics in the development of hyperbilirubinemia. Data concerning serum bilirubin peak distribution in jaundiced newborns were analyzed using a single and a double Gaussian best fit at least squares. The t test was performed to compare 2 values (high and low) of the serum bilirubin peak in breastfed and supplementary-fed infants with those in bottle-fed infants. RESULTS: The maximal serum bilirubin concentration exceeded 12.9 mg/dL (221 micromol/L) in 112 infants (5.1%). The study demonstrated a statistically significant positive correlation between patients with a total serum bilirubin concentration >12.9 mg/dL (221 micromol/L) and supplementary feeding; oppositely, breastfed neonates did not present a higher frequency of significant hyperbilirubinemia in the first days of life. However, best Gaussian fitting of our data suggests that a small subpopulation of breastfed infants have a higher serum bilirubin peak than do bottle-fed infants. Newborns with significant hyperbilirubinemia underwent a greater weight loss after birth compared with the overall studied population, and infants given mixed feeding lost more weight than breastfed and formula-fed newborns, indicating that formula has been administered in neonates who had a weight loss beyond a predetermined percentage of birth weight. Significant hyperbilirubinemia was also strongly associated with delivery by vacuum extractor, some perinatal complications (cephalohematoma, positive Coombs' test, and blood group systems of A, AB, B, and O [ABO] incompatibility) and Asian origin. Multiple logistic regression analysis shows that supplementary feeding, weight loss percentage, ABO incompatibility, and vacuum extraction significantly increase the risk of jaundice, while only cesarean section decreases the risk. CONCLUSION: The present study confirms the important role of fasting in the pathogenesis of neonatal hyperbilirubinemia, although breastfeeding per se does not seem related to the increased frequency of neonatal jaundice but to the higher bilirubin level in a very small subpopulation of infants with jaundice. In fact, in the breastfed infants, there is a small subpopulation with higher serum bilirubin levels. These infants, when starved and/or dehydrated, could probably be at high risk of bilirubin encephalopathy.

Brain hemodynamic changes in preterm infants after maintenance dose caffeine and aminophylline treatment.

OBJECTIVE: To investigate the acute effects of low-dose caffeine and aminophylline on cerebral blood flow in preterm infants, using both near-infrared spectroscopy (NIRS) and cerebral Doppler ultrasonography. METHODS: Preterm infants with a gestational age of <32 weeks and birth weight of <1,500 g were randomized to receive either caffeine or aminophylline treatment for apnea of prematurity. The study period went from 30 min before to 60 min after the administration of the maintenance dose of pure caffeine (2.5 mg/kg once a day) or aminophylline (1.25 mg/kg twice a day). NIRS was used to measure changes in oxygenated hemoglobin (O(2)Hb), deoxygenated hemoglobin (HHb), oxidized-reduced cytochrome aa3 (CtOx), and mean cerebral oxygen saturation (SmO(2) = O(2)Hb/total Hb). Changes in cerebral blood volume (DeltaCBV) after caffeine or aminophylline administration were calculated. Cerebral blood flow velocity (CBV) in the pericallosal artery was evaluated by cerebral Doppler ultrasounds. RESULTS: Data collected by NIRS and cerebral Doppler ultrasounds did not show significant differences before and after caffeine treatment. We observed a significant increase in O(2)Hb and HHb concentration and in CBV at 30 min after the infusion of aminophylline, which tended to return to baseline at the end of the study period. CONCLUSION: Caffeine does not significantly affect brain hemodynamics, while aminophylline induces a significant transient increase in O(2)Hb and HHb concentration and CBV.

Porphyrins and related compounds as photoactivatable insecticides. I. Phototoxic activity of hematoporphyrin toward Ceratitis capitata and Bactrocera oleae.

The photodynamic sensitizer hematoporphyrin (HP) IX was efficiently accumulated by Ceratitis capitata (Mediterranean fruit fly) and Bactrocera oleae (olive fly) when the insects were fed with a sugar/protein bait containing micromolar amounts of porphyrin. Hematoporphyrin appeared to be mainly accumulated in the midgut, Malpighian tubes, adipose tissue and cuticle and was gradually cleared from the organism in a 24-48 h time interval. Exposure of the HP-fed flies to light mimicking the solar spectrum caused a decrease in the survival whose extent was modulated by the HP concentration in the bait, the irradiation fluence rate and the total light dose. For 8 mumol/mL HP in the bait 100% mortality during 1 h exposure to light was obtained using a fluence rate of 1220 microE s-1 m-2 for C. capitata and 2080 microE s-1 m-2 for B. oleae. The latter fly was somewhat less photosensitive than C. capitata possibly owing to the smaller amount of ingested HP and/or darker pigmentation. Studies are in progress in order to extend these investigations from the laboratory to the field scale.

Liposomes as models to study the distribution of porphyrins in cell membranes.

Unilamellar liposomes of dipalmitoylphosphatidylcholine (DPPC) have been chosen as suitable models of cell membranes in studies aimed at defining the influence of specific parameters on the distribution properties of selected hydrophobic photosensitizers, namely hematoporphyrin (HP) and protoporphyrin (PP), in normal and tumour tissues. To better mimic in vivo situations, DPPC liposomes were sometimes mixed with cardiolipin (Card) or cholesterol (Chol). Two techniques were mainly used: the quenching of porphyrin fluorescence by methyl viologen, which can discriminate different dye populations inside the vesicles as well as their degree of accessibility to the external medium, and the polarization of porphyrin fluorescence, which gives information on the dye microenvironment through its degree of rotational freedom. The nature of the porphyrin binding sites in each phospholipid monolayer is found to be a function of the degree of hydrophobicity and the concentration of the dye as well as the chemical composition of the liposomes. In DPPC and DPPC-Chol liposomes, all PP molecules are deeply embedded into very rigid, hydrophobic domains of the inner lipid monolayer. Only in the presence of cardiolipin, for [PP] greater than 2.5 microM, a partial shift of the dye molecules towards the outer lipid monolayer is observed. HP mostly localizes at the inner lipid/water interface in all liposomes: at very low concentrations ([HP] approximately equal to 0.5 microM) the dye is bound to the polar heads of the lipids through its carboxylate groups, leaving the rest of the molecule dissolved in the inner aqueous pool. At higher concentrations, HP molecules change their orientation: the ionized propionic chains still interact with the polar heads while the hydrophobic core lies in the lipid phase in DPPC and DPPC-Card vesicles. HP incorporated into DPPC-Chol mixed liposomes projects from the inner lipid phase into the aqueous compartment in all the concentration range studied by us. A very small fraction of HP population (corresponding to 5-10% of the overall fluorescence) is localized at the water/lipid external interface in DPPC and DPPC-Chol liposomes. This fraction increases in the presence of cardiolipin (up to 30% of the overall fluorescence). The possible implications of these findings for the nature of the targets of photosensitization in cell membranes are discussed.