Episodic formation of refractory inclusions in the Solar System and their presolar heritage.

Refractory inclusions [Ca-Al-rich Inclusions (CAIs) and Amoeboid Olivine Aggregates (AOAs)] in primitive meteorites are the oldest Solar System solids. They formed in the hot inner protoplanetary disk and, as such, provide insights into the earliest disk dynamics and physicochemical processing of the dust and gas that accreted to form the Sun and its planetary system. Using the short-lived 26Al to 26Mg decay system, we show that bulk refractory inclusions in CV (Vigarano-type) and CR (Renazzo-type) carbonaceous chondrites captured at least two distinct 26Al-rich (26Al/27Al ratios of ~5 × 10-5) populations of refractory inclusions characterized by different initial 26Mg/24Mg isotope compositions (µ26Mg*0). Another 26Al-poor CAI records an even larger µ26Mg*0 deficit. This suggests that formation of refractory inclusions was punctuated and recurrent, possibly associated with episodic outbursts from the accreting proto-Sun lasting as short as <8000 yr. Our results support a model in which refractory inclusions formed close to the hot proto-Sun and were subsequently redistributed to the outer disk, beyond the orbit of Jupiter, plausibly via stellar outflows with progressively decreasing transport efficiency. We show that the magnesium isotope signatures in refractory inclusions mirrors the presolar grain record, demonstrating a mutual exclusivity between 26Al enrichments and large nucleosynthetic Mg isotope effects. This suggests that refractory inclusions formed by incomplete thermal processing of presolar dust, thereby inheriting a diluted signature of their isotope systematics. As such, they record snapshots in the progressive sublimation of isotopically anomalous presolar carriers through selective thermal processing of young dust components from the proto-Solar molecular cloud. We infer that 26Al-rich refractory inclusions incorporated 26Al-rich dust which formed <5 Myr prior to our Sun, whereas 26Al-poor inclusions (such as FUN- and PLAC-type CAIs) incorporated >10 Myr old dust.

Uranium isotope compositions of biogenic carbonates - Implications for U uptake in shells and the application of the paleo-ocean oxygenation proxy.

The application of U isotopes in carbonates as a paleo-ocean oxygenation proxy is based on the critical assumption that the calcareous shell-building organisms incorporate U into their shells without fractionation relative to the U isotopic composition of ambient seawater. Recent studies claim a small, but resolvable, isotopic offset during abiotic and biogenic aragonite precipitation, whereas no isotope fractionation has been recorded during calcite precipitation. Although aragonite is meta-stable and not preserved over geological timescales (>1 Myr) and U precipitates during diagenesis, the U isotope composition of biogenic aragonite is important because aragonite precipitation is an important U sink to carbonate sediments. In contrast, low-magnesium calcite (LMC) is preserved over geological timescales and may provide a reliable fingerprint of ancient ocean chemistry. Therefore, a more general study is needed that compares U isotope compositions of primary marine biogenic carbonate precipitates. We report the U isotope compositions of 32 modern samples from geographically distinct localities in the Atlantic Ocean including corals (Scleractinia, Octocorallia), brachiopods (Articulata), molluscs (Tellina Listeri, Codahia Obicularis) and barnacles as well as one fossil mollusc. These samples reflect variable primary minerals, water temperatures, water depths, pH-values of ambient water, and U concentrations. Several seawater samples have also been measured to compare our methods with those of previously published studies. The analyzed modern corals and brachiopods display U isotopic compositions that are indistinguishable from modern seawater. This suggests that these carbonates have the potential to faithfully record the U isotopic composition of the surrounding seawater in which they form. The analyzed brachiopods are of particular interest as they are composed of the calcium carbonate polymorph LMC that is stable over geological timescales. While this study shows for the first time that LMC phases are robust targets in ancient samples, their low U abundance presents analytical challenges for precise U isotope analyses. We also show that two barnacle shells collected with ambient seawater have U isotopic compositions that are both lighter and heavier than the ambient seawater. The mechanism to explain this offset is not determined, but it demonstrates that at least barnacle shells are not representative of the seawater in which they last lived. Two of three partially fossilized mollusc shells also show resolvable offsets from seawater, likely indicating secondary processes that are known to shift or fractionate U isotopes. Collectively, our new data indicate that: 1) aragonite delivers U with a seawater composition to carbonate sediments, and 2) LMC shells of brachiopods that are stable over geological timescales may be more suitable for reconstructing the U isotope composition of ancient oceans.

Pb-Pb ages and initial Pb isotopic composition of lunar meteorites: NWA 773 clan, NWA 4734, and Dhofar 287.

Constraining the duration of magmatic activity on the Moon is essential to understand how the lunar mantle evolved chemically through time. Determining age and initial isotopic compositions of mafic lunar meteorites is a critical step in defining the periods of magmatic activity that occurred during the history of the Moon and to constrain the chemical characteristics of mantle components involved in the sources of the magmas. We have used the in situ Pb-Pb SIMS technique to investigate eight lunar gabbros and basalts, including six meteorites from the Northwest Africa (NWA) 773 clan (NWA 2727, NWA 2700, NWA 3333, NWA 2977, NWA 773, and NWA 3170), NWA 4734, and Dhofar 287A. These samples have been selected as there is no clear agreement on their age and they are all from the dominant low titanium chemical group. We have obtained ages of 2981 ± 12 Ma for NWA 4734 and 3208 ± 22 Ma for Dhofar 287. For the NWA 773 clan, four samples (the fine-grained basalt NWA 2727 and the three gabbros NWA 773, NWA 2977, NWA 3170) out of six yielded isochron-calculated ages that are identical within uncertainties and yielding an average age of 3086 ± 5 Ma. The age obtained for the fine-grained basalt NWA 2700 is not precise enough for comparison with the other samples. The gabbroic sample NWA 3333 yielded an age of 3038 ± 20 Ma suggesting that two distinct magmatic events may be recorded in the meteorites of the NWA 773 clan. The present study aims to identify and assess all potential issues that are associated with different ways to date lunar rocks using U-Pb-based methods. To achieve this, we have compared the new ages with the previously published data set. The entire age data set from lunar mafic meteorites was also screened to identify data showing analytical issues and evidence of resetting and terrestrial contamination. The data set combining the ages of mafic lunar meteorites and Apollo rocks suggests pulses of magmatic activity with two distinct phases between 3950 and 3575 Ma and between 3375 and 3075 Ma with the two phases separated by a gap of approximately 200 Ma. The evolution of the Pb initial ratios of the low-Ti mare basalts between approximately 3400 and 3100 Ma suggests that these rocks were progressively contaminated by a KREEP-like component.

Hadean geodynamics inferred from time-varying 142Nd/144Nd in the early Earth rock record.

Tracking the secular evolution of 142Nd/144Nd anomalies is important towards understanding the crust-mantle dynamics in the early Earth. Excessive scatter in the published data, however, precludes identifying the fine structure of 142Nd/144Nd evolution as the expected variability is on the order of few parts per million. We report ultra-high precision 142Nd/144Nd data for Eoarchean and Palaeoarchean rocks from the Isua Supracrustal Belt (SW Greenland) that show a well-resolved 142Nd/144Nd temporal variability suggesting progressive convective homogenisation of the Hadean Isua depleted mantle. This temporally decreasing 142Nd/144Nd signal provides a direct measure of early mantle dynamics, defining a stirring timescale of <250 Myr consistent with vigorous convective stirring in the early mantle. The 142Nd/144Nd evolution suggests protracted crustal residence times of ~1000-2000 Myr, inconsistent with modern-style plate tectonics in the Archean. In contrast, a stagnant-lid regime punctuated by episodes of mantle overturns accounts for the long life-time estimated here for the Hadean proto-crust.

Pulmonary hypertension in preterm infants: results of a prospective screening program.

OBJECTIVE: Determine prevalence and associations with pulmonary hypertension (PH) in preterm infants. STUDY DESIGN: Prospective institutional echocardiographic PH screening at 36 to 38 weeks' corrected gestational age (GA) for infants born <32 weeks' GA who had bronchopulmonary dysplasia (BPD; group BPD), and infants without BPD who had a birth weight (BW) <750 g, or clinical suspicion for PH (group NoBPD). RESULTS: Two hundred and four infants were screened (GA 25.9±2 weeks, BW 831±286 g). The PH prevalence in group BPD was higher than in group NoBPD (44/159 (28%) vs 5/45 (11%); P=0.028). In group BPD, BW and GA were lower in infants with PH compared with NoPH. Following correction for BW and GA, necrotizing enterocolitis (NEC), severe intraventricular hemorrhage (IVH), atrial septal defect (ASD), and mortality were independently associated with PH in infants with BPD. In group NoBPD, NEC was the only identified factor associated with PH. Altogether, screening only those infants with NEC and infants with BPD who also had a BW <840 g would have yielded a 84% sensitivity for detecting PH, and reduced the number of screening echocardiograms by 43%. CONCLUSIONS: PH in prematurity is associated with NEC in infants with and without BPD. In infants with BPD, smaller GA and BW, severe IVH, ASD and mortality are also associated with PH. Infants without identified PH-associated factors may not require routine echocardiographic PH screening.

Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk.

The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al-26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ~ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of µ26Mg (µ26Mg*) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg* in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ~250,000 years of solar system formation from a hot (>~500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (~1-2 × 10-5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10-5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These 'non-carbonaceous' planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and undifferentiated chondritic crusts. In contrast, individual olivine crystals from Eagle Station pallasites record variable µ26Mg* excesses, suggesting that these crystals captured the 26Mg* evolution of a magmatic reservoir controlled by fractional crystallization processes during the lifespan of 26Al. Similar to previous suggestions based on isotopic evidence, we suggest that Eagle Station pallasites formed from precursor material similar in composition to carbonaceous chondrites from a cool outer protoplanetary disk region characterized by (26Al/27Al)0 ≥ 2.7 × 10-5. Protracted planetesimal accretion timescales at large orbital distances, with onset of accretion 0.3-1 Myr post-CAIs, may have resulted in significant radiative heat loss and thus efficient early interior cooling of slowly accreting 'carbonaceous' planetesimals.

Chromatographic speciation of Cr(III)-species, inter-species equilibrium isotope fractionation and improved chemical purification strategies for high-precision isotope analysis.

Chromatographic purification of chromium (Cr), which is required for high-precision isotope analysis, is complicated by the presence of multiple Cr-species with different effective charges in the acid digested sample aliquots. The differing ion exchange selectivity and sluggish reaction rates of these species can result in incomplete Cr recovery during chromatographic purification. Because of large mass-dependent inter-species isotope fractionation, incomplete recovery can affect the accuracy of high-precision Cr isotope analysis. Here, we demonstrate widely differing cation distribution coefficients of Cr(III)-species (Cr(3+), CrCl(2+) and CrCl2(+)) with equilibrium mass-dependent isotope fractionation spanning a range of ∼1‰/amu and consistent with theory. The heaviest isotopes partition into Cr(3+), intermediates in CrCl(2+) and the lightest in CrCl2(+)/CrCl3°. Thus, for a typical reported loss of ∼25% Cr (in the form of Cr(3+)) through chromatographic purification, this translates into 185 ppm/amu offset in the stable Cr isotope ratio of the residual sample. Depending on the validity of the mass-bias correction during isotope analysis, this further results in artificial mass-independent effects in the mass-bias corrected (53)Cr/(52)Cr (µ(53)Cr* of 5.2 ppm) and (54)Cr/(52)Cr (µ(54)Cr* of 13.5 ppm) components used to infer chronometric and nucleosynthetic information in meteorites. To mitigate these fractionation effects, we developed strategic chemical sample pre-treatment procedures that ensure high and reproducible Cr recovery. This is achieved either through 1) effective promotion of Cr(3+) by >5 days exposure to HNO3H2O2 solutions at room temperature, resulting in >∼98% Cr recovery for most types of sample matrices tested using a cationic chromatographic retention strategy, or 2) formation of Cr(III)-Cl complexes through exposure to concentrated HCl at high temperature (>120 °C) for several hours, resulting in >97.5% Cr recovery using a chromatographic elution strategy that takes advantage of the slow reaction kinetics of de-chlorination of Cr in dilute HCl at room temperature. These procedures significantly improve cation chromatographic purification of Cr over previous methods and allow for high-purity Cr isotope analysis with a total recovery of >95%.

Tungsten isotopes in bulk meteorites and their inclusions-Implications for processing of presolar components in the solar protoplanetary disk.

We present high precision, low- and high-resolution tungsten isotope measurements of iron meteorites Cape York (IIIAB), Rhine Villa (IIIE), Bendego (IC), and the IVB iron meteorites Tlacotepec, Skookum, and Weaver Mountains, as well as CI chondrite Ivuna, a CV3 chondrite refractory inclusion (CAI BE), and terrestrial standards. Our high precision tungsten isotope data show that the distribution of the rare p-process nuclide 180W is homogeneous among chondrites, iron meteorites, and the refractory inclusion. One exception to this pattern is the IVB iron meteorite group, which displays variable excesses relative to the terrestrial standard, possibly related to decay of rare 184Os. Such anomalies are not the result of analytical artifacts and cannot be caused by sampling of a protoplanetary disk characterized by p-process isotope heterogeneity. In contrast, we find that 183W is variable due to a nucleosynthetic s-process deficit/r-process excess among chondrites and iron meteorites. This variability supports the widespread nucleosynthetic s/r-process heterogeneity in the protoplanetary disk inferred from other isotope systems and we show that W and Ni isotope variability is correlated. Correlated isotope heterogeneity for elements of distinct nucleosynthetic origin (183W and 58Ni) is best explained by thermal processing in the protoplanetary disk during which thermally labile carrier phases are unmixed by vaporization thereby imparting isotope anomalies on the residual processed reservoir.

One size does not fit all: why universal decolonization strategies to prevent methicillin-resistant Staphylococcus aureus colonization and infection in adult intensive care units may be inappropriate for neonatal intensive care units.

The REDUCE MRSA Trial (Randomized Evaluation of Decolonization vs Universal Clearance to Eliminate Methicillin-Resistant Staphylococcus aureus), a large multicenter, randomized controlled trial in adult intensive care units (ICUs), found universal decolonization to be more effective than surveillance and isolation procedures with or without targeted decolonization for reducing rates of MRSA-positive clinical cultures. The Agency for Healthcare Research and Quality and the Centers for Disease Control and Prevention subsequently published protocols for implementing universal decolonization in ICUs based on the trial's methods. Caution should be exercised before widely adopting these procedures in neonatal intensive care units (NICUs), particularly strategies that involve bathing with chlorhexidine and mupirocin application due to the potential for adverse events in their unique patient population, especially preterm infants. Large multicenter trials in the NICUs are needed to evaluate the efficacy, short- and long-term safety, and cost effectiveness of these strategies prior to their widespread implementation.

Observations of nitrogen isotope fractionation in deeply embedded protostars.

CONTEXT: The terrestrial planets, comets, and meteorites are significantly enriched in 15N compared to the Sun and Jupiter. While the solar and jovian nitrogen isotope ratio is believed to represent the composition of the protosolar nebula, a still unidentified process has caused 15N-enrichment in the solids. Several mechanisms have been proposed to explain the variations, including chemical fractionation. However, observational results that constrain the fractionation models are scarce. While there is evidence of 15N-enrichment in prestellar cores, it is unclear how the signature evolves into the protostellar phases. AIMS: The aim of this study is to measure the 14N/15N ratio around three nearby, embedded low- to intermediate-mass protostars. METHODS: Isotopologues of HCN and HNC were used to probe the 14N/15N ratio. A selection of J = 3-2 and 4-3 transitions of H13CN, HC15N, HN13C, and H15NC was observed with the Atacama Pathfinder EXperiment telescope (APEX). The 14N/15N ratios were derived from the integrated intensities assuming a standard 12C/13C ratio. The assumption of optically thin emission was verified using radiative transfer modeling and hyperfine structure fitting. RESULTS: Two sources, IRAS 16293A and R CrA IRS7B, show 15N-enrichment by a factor of ~1.5-2.5 in both HCN and HNC with respect to the solar composition. IRAS 16293A falls in the range of typical prestellar core values. Solar composition cannot be excluded for the third source, OMC-3 MMS6. Furthermore, there are indications of a trend toward increasing 14N/15N ratios with increasing outer envelope temperature. CONCLUSIONS: The enhanced 15N abundances in HCN and HNC found in two Class 0 sources (14N/15N ~ 160-290) and the tentative trend toward a temperature-dependent 14N/15N ratio are consistent with the chemical fractionation scenario, but 14N/15N ratios from additional tracers are indispensable for testing the models. Spatially resolved observations are needed to distinguish between chemical fractionation and isotope-selective photochemistry.

Platinum stable isotope analysis of geological standard reference materials by double-spike MC-ICPMS.

We report a method for the chemical purification of Pt from geological materials by ion-exchange chromatography for subsequent Pt stable isotope analysis by multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS) using a 196Pt-198Pt double-spike to correct for instrumental mass bias. Double-spiking of samples was carried out prior to digestion and chemical separation to correct for any mass-dependent fractionation that may occur due to incomplete recovery of Pt. Samples were digested using a NiS fire assay method, which pre-concentrates Pt into a metallic bead that is readily dissolved in acid in preparation for anion-exchange chemistry. Pt was recovered from anion-exchange resin in concentrated HNO3 acid after elution of matrix elements, including the other platinum group elements (PGE), in dilute HCl and HNO3 acids. The separation method has been calibrated using a precious metal standard solution doped with a range of synthetic matrices and results in Pt yields of ≥90% with purity of ≥95%. Using this chemical separation technique, we have separated Pt from 11 international geological standard reference materials comprising of PGE ores, mantle rocks, igneous rocks and one sample from the Cretaceous-Paleogene boundary layer. Pt concentrations in these samples range from ca. 5 ng g-1 to 4 µg g-1. This analytical method has been shown to have an external reproducibility on δ198Pt (permil difference in the 198Pt/194Pt ratio from the IRMM-010 standard) of ±0.040 (2 sd) on Pt solution standards (Creech et al., 2013, J. Anal. At. Spectrom. 28, 853-865). The reproducibility in natural samples is evaluated by processing multiple replicates of four standard reference materials, and is conservatively taken to be ca. ±0.088 (2 sd). Pt stable isotope data for the full set of reference materials have a range of δ198Pt values with offsets of up to 0.4‰ from the IRMM-010 standard, which are readily resolved with this technique. These results demonstrate the potential of the Pt isotope system as a tracer in geochemical systems.

Temporal quantification of oxygen saturation ranges: an effort to reduce hyperoxia in the neonatal intensive care unit.

OBJECTIVE: To reduce exposure to hyperoxia and its associated morbidities in preterm neonates. STUDY DESIGN: A multidisciplinary group was established to evaluate oxygen exposure in our neonatal intensive care unit. Infants were assigned target saturation ranges and signal extraction technology implemented to temporally quantify achievement of these ranges. The outcomes bronchopulmonary dysplasia/death, retinopathy of prematurity (ROP)/death, severe ROP and ROP requiring surgery were compared in a pre- versus post-intervention evaluation using multivariate analyses. RESULT: A total of 304 very low birth weight pre-initiative infants were compared with 396 post-initiative infants. Multivariate analyses revealed decreased odds of severe ROP (adjusted odds ratio (OR): 0.41; 95% confidence interval (CI): 0.24-0.72) and ROP requiring surgery (adjusted OR 0.31; 95% CI: 0.17-0.59) post-initiative. No differences in death were observed. CONCLUSION: Significant reductions in severe ROP and ROP requiring surgery were observed after staff education and implementation of new technology to quantify success in achieving targeted saturations and reinforce principles and practices.

Late-onset Leclercia adecarboxylata sepsis in a premature neonate.

The epidemiology, etiology and outcome of neonatal sepsis are changing over time. While monitoring longitudinal trends in neonatal sepsis in our institution, we encountered a case of late-onset neonatal sepsis due to Leclercia adecarboxylata. A Gram-negative rod previously not encountered in the clinical setting, L. adecarboxylata has recently emerged as a human pathogen, primarily in immunosuppressed patients. This report describes the clinical and laboratory features of this case of late-onset L. adecarboxylata sepsis, and reviews significant features of infection associated with this emerging pathogen.

Dental caries in Rome, 50-100 AD.

Scarce information exists on the clinical features of dental caries in the Imperial Roman population and no structural data on caries lesions from this period have so far been published. We report on the findings of 86 teeth (50-100 AD) found during archaeological excavations of the temple of Castor and Pollux in the Forum Romanum. We found that nearly all teeth had large carious cavities extending into the pulp. The distribution and size of the caries lesions were similar to those found in contemporary adult populations in Africa and China living without access to dental care. Most lesions had a hypermineralized zone in the dentin at the advancing front of the carious cavities as revealed by micro-computed tomography. This biological dentin reaction combined with the morphology of the cavities might indicate that some temporary topical pain relief and intervention treatment slowed down the rate of lesion progression. This is indirectly supported by examination of cavities of similar size and depth from a contemporary population without access to dental health care. In contrast to the lesions in the Roman teeth, these lesions did not exhibit a hypermineralized dentin reaction. We investigated whether the Pb isotopic composition of enamel and/or dentin of a single tooth matched that of a sample of an ancient Forum water lead pipe. The Pb isotopic composition of the tooth did not match that of the tube, suggesting that the subjects were exposed to different Pb sources during their lifetime other than the lead tubes.

Complications associated with central and non-central venous catheters in a neonatal intensive care unit.

OBJECTIVE: The objective of this study is to compare complication rates between peripherally inserted central catheters (PICCs) and peripherally inserted non-central catheters (PINCCs) in the neonatal intensive care unit (NICU). STUDY DESIGN: A retrospective, observational study was conducted. The PICCs were catheters whose tip terminated in the vena cavae, and PINCCs were defined as those whose tip fell short of this location. Complication rates were assessed using generalized estimating equations modeling. RESULT: A total of 91 PINCCs and 889 PICCs were placed in 750 neonates. In all, 44.0% of PINCCs had a major complication compared with 25.2% of PICCs (P=0.0001). The unadjusted (unadj.) complication rate among PINCCs was 51.7 per 1000 line days and 15.9 for PICCs (unadj. rate ratio: 3.25; 95% confidence interval (CI): 2.32, 4.55). After adjusting for multiple confounders, the risk remained significantly higher for PINCCs (adjusted odds ratio: 2.41; 95% CI: 1.33, 4.37). CONCLUSION: The rate of associated complications with the use of PINCCs in the NICU population is more than twice that of the PICCs.

Risk factors for necrotizing enterocolitis totalis: a case-control study.

OBJECTIVE: The objective of this study was to compare demographic and clinical events in three groups of preterm neonates: those with necrotizing enterocolitis totalis (NEC-T), those with NEC non-totalis (NEC non-T) and in preterm patients without NEC. STUDY DESIGN: This retrospective case-control study was conducted at Yale New Haven Children's Hospital using patient data from January 1991 to December 2007. Study patients were less than 36 weeks of gestational age (GA) at birth, without gastrointestinal (GI) malformations. Cases (NEC-T) were diagnosed at operation or at autopsy with observation of >80% necrosis of the GI tract. Two control groups were assigned: Group 1 or NEC non-T and Group II or Non-NEC. Two to four controls per case were matched to cases by GA at birth±2 weeks. Demographic and clinical data for the day of diagnosis and retrospectively up to 7 days preceding diagnosis were recorded for those with NEC-T and NEC. Group II controls were matched for date of birth and day of life, in addition to GA at birth. RESULT: A total of 14 075 patients were admitted to the Newborn Special Care Unit during the study interval. Overall 328 patients (2.3%) developed NEC≥Bell's Stage II; 39 patients met inclusion criteria for NEC-T case status; 148 NEC non-T and 110 non-NEC controls were assigned. In the comparison of NEC T and NEC non-T neonates, use of breast milk was associated with decreased risk of NEC-T, adjusted odds ratio (OR)=0.26, 95% confidence interval (CI) of OR=0.08-0.085, P=0.03. When NEC T and non-NEC patients were compared, having reached full-enteral feeds before the date of diagnosis of the matched case (adjusted OR=28.5, 95% CI of OR=2.7-299, P=0.005) and use of breast milk (adjusted OR=0.09, 95% CI of OR=0.02-0.56, P=0.01) were significantly different between the two groups. CONCLUSION: Breast milk usage was significantly associated with decreased occurrence of NEC-T in our comparison of NEC-T, NEC non-T and non-NEC patients. Although there were some differences, the majority of demographic and clinical variables assessed were not shown to be significantly different between cases and controls. This highlights the need for more biological data in assessing risk of developing NEC-T.

Who is performing medical procedures in the neonatal intensive care unit?

OBJECTIVE: Owing to resident work-hour reductions and more permanent personnel in the newborn intensive care unit (NICU), we sought to determine if pediatric housestaff are missing learning opportunities in procedural training due to non-participation. STUDY DESIGN: A prospective, observational study was conducted at an academic NICU using self-reported data from neonatal personnel after attempting 188 procedures on 109 neonates, and analyzed using Fisher's exact and χ (2)-tests. RESULT: Housestaff first attempted 32% of procedures (P<0.001) and were less likely to make attempts early in the academic year (P<0.001). There was no significant difference in attempts based on urgency of situation (P=0.742). Of procedures performed by non-housestaff personnel, 93% were completed while housestaff were present elsewhere in the unit. CONCLUSION: Pediatric housestaff performed the minority of procedures in the NICU, even in non-urgent situations, and were often uninvolved in other procedures, representing missed learning opportunities.

Selective resuscitation in premature twins: an ethical analysis.

Selective resuscitation refers to the practice of providing resuscitative efforts to one or some (but not all) infants born in the setting of multiple gestation. When one fetus is known to have a severe anomaly or severe growth restriction, parents are sometimes offered this option. In the setting of extreme prematurity, in the absence of an anomaly or severe growth restriction, parents are generally expected to make one unified decision for all the infants involved. The introduction of the Outcome Estimator, a tool that provides the ability to make individual outcome predictions for each fetus in a multiple gestation at borderline gestational age, based on contributing variables such as weight and gender, has led to the ethical dilemma of whether parents in this setting should also be offered the option of selective resuscitation. No convincing ethical argument for denying the parents the right to decide for each individual infant is apparent.

Patient selection for neonatal extracorporeal membrane oxygenation: beyond severity of illness.

OBJECTIVE: To explore how neonates with respiratory failure are selected for extracorporeal membrane oxygenation (ECMO) once severity of illness criteria are met, and to determine how conflicts between ECMO providers and parents over the initiation of ECMO are addressed. STUDY DESIGN: A cross-sectional study was conducted using a data collection survey, which was sent to the directors of neonatal respiratory ECMO centers. RESULT: The lowest birth weight and gestational age at which respondents would consider placing a neonate on ECMO were frequently below recommended thresholds. There was wide variability in respondents' willingness to place neonates on ECMO in the presence of conditions such as intraventricular hemorrhage and hypoxic ischemic encephalopathy. The number of respondents who would never seek to override parental refusal of ECMO was equal to the number who would always do so. CONCLUSION: Significant variability exists in the selection criteria for neonatal ECMO and in how conflicts with parents over the provision of ECMO are resolved.