Increased farnesylation of p21-Ras and neonatal macrosomia in women with gestational diabetes.

Six of 22 mothers with gestational diabetes mellitus had infants with macrosomia, cord blood hyperinsulinemia, and increased amounts of a key mitogenic intermediate, farnesylated p21-Ras. The ability of fetal hyperinsulinemia to increase the availability of farnesylated p21-Ras may represent one mechanism of the growth-promoting action of insulin during fetal development.

Exchangeable zinc pool size at birth is smaller in small-for-gestational-age than in appropriate-for-gestational-age preterm infants.

BACKGROUND: Small-for-gestational-age (SGA) infants are susceptible to postnatal zinc deficiency, but whether this susceptibility is due to intrauterine factors or to high postnatal growth requirements is unknown. OBJECTIVE: We hypothesized that the size of the exchangeable zinc pool (EZP), which reflects metabolically available zinc, would be smaller in SGA than in appropriate-for-gestational-age (AGA) infants born prematurely. DESIGN: Intravenous 70Zn (45 microg/kg) was administered to 10 SGA infants (8 boys) with a mean (+/-SD) gestational age of 33.3 +/- 1.8 wk and to 11 AGA infants (8 boys) with a mean (+/-SD) gestational age of 32.4 +/- 1.2 wk within 24 h of birth. The EZP was determined from isotope enrichment in spot urine collections on days 3-7. RESULTS: The mean birth weight of the SGA infants was 1.30 +/- 0.2 kg and of the AGA infants was 1.84 +/- 0.3 kg (P = 0.0001). The EZP size was significantly smaller in the SGA than in the AGA infants on an absolute basis (13.3 +/- 2.8 and 25.2 +/- 8.1 mg; P = 0.0002) and relative to body weight (10.3 +/- 2.5 and 13.9 +/- 4.5 mg/kg; P = 0.02). The difference remained significant after adjustment for gestational age and birth weight. CONCLUSION: These data provide evidence for differential zinc status at birth between SGA and AGA infants born prematurely at similar stages of gestation and offer at least a partial explanation for the reported benefits of postnatal zinc supplementation.

Zinc homeostasis in premature infants does not differ between those fed preterm formula or fortified human milk.

The objectives of this study were to compare zinc homeostasis in premature infants enterally fed with either preterm infant formula or fortified human milk; to examine interrelationships of variables of zinc homeostasis; and to examine the findings in relation to estimated zinc requirements of preterm infants. Zinc homeostasis was studied in 14 infants (8 male), with mean gestational age of 31 wk and birth weight appropriate for gestational age, who were exclusively fed either preterm formula (n = 9) or own mother's milk with human milk fortifier (n = 5). Zinc stable isotopes were administered intravenously ((70)Zn) and orally as an extrinsic label ((67)Zn) over multiple feeds for determination of fractional absorption by dual isotope tracer ratio in urine; endogenous fecal zinc was determined by isotope dilution; and exchangeable zinc pool (EZP) size was estimated from linear regression of log-transformed urine (70)Zn enrichment data. Results indicated no significant differences in the variables of zinc homeostasis between the feeding groups; data for all subjects were thus combined. Mean (+/- SD) fractional absorption was 0.26 +/- 0.07; net absorbed zinc 0.43 +/- 0.25 mg/d (0.31 +/- 0.19 mg/kg/d). Mean EZP was 20 +/- 10 mg/kg, and was positively correlated with total absorbed zinc and with net absorbed zinc. Feeding type and total absorbed zinc were significantly related to daily weight gain (p = 0.003). Current zinc intakes from fortified human milk or formula are associated with acceptable weight gain, but whether the observed net zinc absorption was optimal in the human milk group cannot be definitively determined from these data.

Reliability of conventional and new pulse oximetry in neonatal patients.

OBJECTIVES: Pulse oximetry is widely used in the NICU, but clinicians often distrust the displayed values during patient motion, i.e., questionable oxygen saturation (SpO(2)) and pulse rate (PR) values. Masimo Corporation (Irvine, CA) has developed pulse oximetry with claims of resistance to sources of interference. To test this premise, we compared the performance of the Masimo SET pulse oximeter to a conventional device, Nellcor N-200, and then with three other new-generation pulse oximeters, Nellcor N-395, Novametrix MARS, and Philips Viridia 24C. STUDY DESIGN: We studied 26 nonsedated NICU infants who were on supplemental oxygen and/or mechanical ventilation. ECG heart rate (HR) from a bedside monitor and SpO(2) and PR from the two pulse oximeters were captured by a PC for a total of 156 hours. The ECG HR and pulse oximeter spectral waveform were analyzed at alarms for hypoxemia (SpO(2)< or = 85%) and/or bradycardia (HR< or = 80 bpm). We then compared the performance of the Masimo SET to three other new-generation pulse oximeters, Agilent Viridia 24C, Nellcor N-395, and Novametrix MARS, in a similar population of seven infants for a total of 28 hours. We added to the test criteria the ability of the various pulse oximeters to track acute changes in HR. RESULTS: Compared with Nellcor, Masimo SET had 86% fewer false alarms, which also were shorter in duration, resulting in 92% less total alarm time. Masimo SET also identified nearly all bradycardias versus 14% for the Nellcor. Compared with the new-generation pulse oximeters, false desaturations, data drop-outs, and false bradycardias were lowest for Masimo SET, as was the capture of true desaturations and bradycardias. Notably, the new-generation devices differed greatly in their ability to detect changes in HR (i.e., the frequency of frozen PR during times of ECG HR change was 0, 6, 11, and 46 for Masimo, Nellcor, Philips, and Novametrix, respectively). CONCLUSIONS: Masimo SET pulse oximetry recorded markedly fewer false SpO(2) and PR alarms and identified more true hypoxic and bradycardic events than either conventional or other new-generation pulse oximeters. Masimo SET also most closely reflected the ECG rate irrespective of accelerations or decelerations in HR. SPECULATION: Routine use of Masimo SET pulse oximetry in the NICU could improve clinician confidence in the parameter leading to more judicious titration of oxygen with possible reductions in hypoxic (e.g., pulmonary hypertension) and hyperoxic (e.g., retinopathy of prematurity) pathology. Additionally, a more trustworthy technology should equate with fewer confirmatory arterial blood gas analyses (less blood loss), and faster weaning from the mechanical ventilation (less chronic lung disease).