Static respiratory compliance in the newborn. II: Its potential for improving the selection of infants for early surfactant treatment.

Static respiratory system compliance (Crs) and lecithin/sphingomyelin (L/S) ratios in tracheal aspirates were estimated in two independent groups of mechanically ventilated infants. Crs was measured rapidly at the cotside using a passive expiratory flow technique and L/S ratios were estimated in the laboratory by high performance liquid chromatography. In the reference group of 22 infants, Crs < 1.8 ml/cm H2O/m predicted surfactant deficiency with a positive predictive value of 100% and a negative predictive value of 92%. In the validation group of 23 infants, Crs < 1.8 ml/cm H2O/m predicted surfactant deficiency with a positive predictive value of 94% and a negative predictive value of 83%. Measurement of static Crs is a rapid, non-invasive technique which may usefully supplement current methods of selecting infants at high risk of respiratory distress syndrome.

Trace mineral balances in preterm infants fed their own mother's milk.

Balance studies were conducted on preterm infants (birthweight, 1,500 g or less) fed their own mother's milk or formula (SMA with iron) to compare the relative adequacy of these sources for copper (Cu), iron (Fe), and zinc (Zn). Urine and stools were collected for 72 h from infants aged 1, 2, or 4 weeks while they were fed milk or formula. Infants fed SMA 24 (but not SMA 20) received Cu, Fe, and Zn intakes within the recommended range. They did not, however, achieve estimated in utero retention rates for Fe, and were in negative Cu balance; they did approach in utero retention rates for Zn. Infants fed their own mother's milk received Cu and Zn, but not Fe, in recommended amounts. They achieved in utero retention rates for Cu at each age studied and approached the estimated in utero retention rates for Zn at 4 weeks, but they retained insufficient Fe throughout. Thus, neither the infant's own mother's milk nor this particular formula provides ideal amounts of all three minerals studied--Cu, Zn, and Fe--during the 1st month of life.

Zinc, copper and iron content of milk from mothers of preterm and full-term infants.

Complete 24-hour expressions of milk were collected over the first month of lactation from mothers giving birth at term (FT) and prematurely (PT). Samples were analyzed for Cu, Fe and Zn concentration. Composition of PT and FT milks was similar during the first 4 weeks of lactation, but the concentrations of each mineral were higher during the first week than during the fourth week. From these data, the intakes of premature infants fed their own mother's milk were estimated and the proportion which must be absorbed and retained in order to accumulate the amounts laid down in utero were predicted. On the basis of these estimates, preterm infants who retain 25% of the Zn and 35% of the Cu in PT milk would approximate in utero accumulations. However, the Fe content of PT milk is unlikely to provide for in utero accretion rates, even if 100% absorption as achieved.

Cysteine supplementation to cysteine-free intravenous feeding regimens in newborn infants.

To determine if cysteine is an essential amino acid for the intravenously fed newborn infant, growth parameters, nitrogen balance, plasma sulfur amino acid levels, and urinary amino acid excretion of premature and term infants were measured in the presence or absence of infused cysteine. Control intravenous formulations provided amino acids, including adequate methionine, carbohydrate, lipid, minerals, vitamins, and trace elements to all infants. Group and pair-matched comparisons showed that nitrogen retention, weight change, and growth in length and head circumference were not affected by cysteine supplementation of 77 mg/kg/24 h. The failure of cysteine supplementation to alter nitrogen retention was independent of postnatal age or gestational age. Plasma 1/2 cystine concentration was increased by 60% in the supplemented group with a concomitant 3-fold increase in urinary excretion of 1/2 cystine and taurine, but not of urinary methionine or cystathionine. Cysteine-supplemented infants exhibited a small increase in 3-methylhistidine excretion compared to pair-matched controls, suggesting that either an increase in muscle protein catabolism or an increase in muscle mass may have occurred.

Macro-mineral content of milk obtained during early lactation from mothers of premature infants.

Milk from mothers giving birth prematurely was analyzed for Na, Cl, K, Mg, Ca and P concentrations. The data presented are from analyses of milk samples representative of complete 24-hour expressions and collected serially over the first 29 days of lactation from mothers giving birth at term (FT) and mothers giving birth prematurely (PT). Mineral composition of FT and PT milks was similar during the first month lactation. With the exceptions of Mg and P, the concentrations of the minerals studied were higher initially than at the end of the fourth week of lactation. From these data, intakes of premature infants fed their own mothers' milk can be estimated and compared to predicted mineral requirements for the premature infant. On the basis of this comparison, we suggest that the quantities provided of Na, Cl, K and Mg, but not Ca and P, would be adequate to meet requirements of premature infants during the early weeks of life.

The effect of Intralipid on the estimation of serum bilirubin in the newborn infant.

After noting rises in measured serum billirubin in premature infants undergoing parenteral nutrition, a series of experiments was designed to ascertain the effect of the presence of Intralipid on the actual laboratory analysis. It has been shown that the most commonly used spectrophotometric analysis of bilirubin and the estimation of direct bilirubin by micromethods are affected by the presence of Intralipid in the specimens. Centrifugation of the blood samples at 15,000 rpm for 10 minutes and analysis of the aqueous layer overcomes, in both methods, the interference and error introduced by the presence of Intralipid chylomicrons in patient sera. Alternatively spurious bilirubin measurements due to hyperlipidemia may be avoided by using a bilirubinometer equipped with a filter which eliminates the effect of Intralipid interference.