Antenatal Bartter Syndrome: A Review

Antenatal Bartter syndrome (ABS) is a rare autosomal recessive renal tubular disorder. The defective chloride transport in the loop of Henle leads to fetal polyuria resulting in severe hydramnios and premature delivery. Early onset, unexplained maternal polyhydramnios often challenges the treating obstetrician. Increasing polyhydramnios without apparent fetal or placental abnormalities should lead to the suspicion of this entity. Biochemical analysis of amniotic fluid is suggested as elevated chloride level is usually diagnostic. Awareness, early recognition, maternal treatment with indomethacin, and amniocentesis allow the pregnancy to continue. Affected neonates are usually born premature, have postnatal polyuria, vomiting, failure to thrive, hypercalciuria, and subsequently nephrocalcinosis. Hypokalemia, metabolic alkalosis, secondary hyperaldosteronism and hyperreninaemia are other characteristic features. Volume depletion due to excessive salt and water loss on long term stimulates renin-angiotensin-aldosterone system resulting in juxtaglomerular hyperplasia. Clinical features and electrolyte abnormalities may also depend on the subtype of the syndrome. Prenatal diagnosis and timely indomethacin administration prevent electrolyte imbalance, restitute normal growth, and improve activity. In this paper, authors present classification, pathophysiology, clinical manifestations, laboratory findings, complications, and prognosis of ABS

Postnatal growth and short-term complications in very low birth weight neonates receiving total parenteral nutrition

Objective: To study the postnatal growth and short-term complications in very low birth weight preterm neonates receiving totalparenteral nutrition (TPN). Methods: This prospective, observational study was conducted in the neonatal intensive care unit ofa tertiary care hospital in South India. All neonates with birth weight <1250 g and <32 weeks of gestation who received TPNand survived at least 7 days were studied prospectively. Amino acid infusion was started at 1 g/kg/day on day 1 and graded up to4 g/kg/day. Lipids were started on the day 2 of life at 1 g/kg/day and graded up to 3 g/kg/day. Enteral feeds were introduced within3 days of life. TPN was stopped once enteral feeds reached 100 ml/kg/day. Postnatal growth and biochemical and hematologicalparameters were also monitored. Results: Time to reach full enteral feeds was 11.3±4.5 days, cumulative weight loss proportion(in %) was 8.5±4.7, and number of days to regain birth weight was 11.1±4.5 days. Mean growth velocity (GV) at 30 days of lifeand 40 weeks of postmenstrual age (PMA) was 16.37±4.8 g/kg/day and 20.03±5.8 g/day, respectively. Mean GV of appropriatefor gestational age (AGA) infants was 3.13 g/kg/day, lower compared to small for GA (SGA) infants at 30 days PMA (p=0.01).However, there was no statistical difference in GV between AGA and SGA infants at 40 weeks of PMA. There was no correlationbetween energy intake on the day 7 and weight and head circumference at 40 weeks of PMA. Hyponatremia was observed in 40.6%infants receiving TPN, and there were no other significant complications. Conclusion: Conventional TPN was associated withfavorable postnatal growth until 30 days of postnatal life. However, catch-up growth at 40 weeks of PMA was not satisfactory. MeanGV of AGA infants was found to be lower compared to that in SGA infants at 30 days of postnatal life. Besides hyponatremia, therewas no major complication due to TPN in this study

Antenatal Bartter Syndrome: A Review

Antenatal Bartter syndrome (ABS) is a rare autosomal recessive renal tubular disorder. The defective chloride transport in the loop of Henle leads to fetal polyuria resulting in severe hydramnios and premature delivery. Early onset, unexplained maternal polyhydramnios often challenges the treating obstetrician. Increasing polyhydramnios without apparent fetal or placental abnormalities should lead to the suspicion of this entity. Biochemical analysis of amniotic fluid is suggested as elevated chloride level is usually diagnostic. Awareness, early recognition, maternal treatment with indomethacin, and amniocentesis allow the pregnancy to continue. Affected neonates are usually born premature, have postnatal polyuria, vomiting, failure to thrive, hypercalciuria, and subsequently nephrocalcinosis. Hypokalemia, metabolic alkalosis, secondary hyperaldosteronism and hyperreninaemia are other characteristic features. Volume depletion due to excessive salt and water loss on long term stimulates renin-angiotensin-aldosterone system resulting in juxtaglomerular hyperplasia. Clinical features and electrolyte abnormalities may also depend on the subtype of the syndrome. Prenatal diagnosis and timely indomethacin administration prevent electrolyte imbalance, restitute normal growth, and improve activity. In this paper, authors present classification, pathophysiology, clinical manifestations, laboratory findings, complications, and prognosis of ABS

Prophylactic Methylxanthines for Preventing Extubation Failure in the Preterm Neonates with the Gestational Age of ≤30 Weeks: A Randomized Controlled Trial

Background: Preterm neonates are at a high risk of respiratory depression at birth. Incidence of respiratory distress is reported in 60-80% of the neonates born with the gestational age of less than 28 weeks and 15-30% of the neonates with the gestational age of less than 32-34 weeks. The present study aimed to compare the incidence and risk of failed extubation in using caffeine and aminophylline in the preterm neonates with the gestational age of ≤30 weeks in the periextubation period.Methods: This single-centered, parallel, open-label, randomized controlled trial was conducted in a tertiary care referral hospital in India during June 2014-2016. Neonates with the gestational age of ≤30 weeks who were intubated for a minimum of 24 hours were enrolled in the study. Neonates with major anomalies, heart disease, and sepsis were excluded from the study. After the random allocation of the infants to treatment with the standard dose of caffeine citrate and aminophylline methylxanthine, intubation continued for seven consecutive days with or without non-invasive ventilatory support. As the primary objective, the incidence and risk of failed extubation were assessed. Secondary objective of the research was to compare the relative incidence of acute adverse effects, persistent apnea, and the associated morbidities.Results: Neonates treated by caffeine were at a higher risk of extubation failure (1.09 times) adjusted with birth weight (31.5% versus 21.4%; RR=1.09; 95% CI: 0.81-1.46; P=0.55), which was not statistically significant. In addition, risk of apnea within seven days and after seven days of methylxanthine therapy was 1.57 (95% CI: 0.95-2.61) and 1.10 (95% CI: 0.95-2.61) times higher in the neonates with caffeine treatment. Also, rate of tachycardia was high in the neonates treated by aminophylline, which was statistically significant (RR=0.27; 95% CI: 0.13-0.56;

Multifrequency Observations of Radio Pulse Broadening and Constraints on Interstellar Electron Density Microstructure

We have made observations of 98 low-Galactic-latitude pulsars to measure pulse broadening caused by multipath propagation through the interstellar medium. Data were collected with the 305-m Arecibo telescope at four radio frequencies between 430 and 2380 MHz. We used a CLEAN-based algorithm to deconvolve interstellar pulse broadening from the measured pulse shapes. We employed two distinct pulse broadening functions (PBFs): PBF$_1$ is appropriate for a thin screen of scattering material between the Earth and a pulsar, while PBF$_2$ is appropriate for scattering material uniformly distributed along the line of sight from the Earth to a pulsar. We found that some observations were better fit by PBF$_1$ and some by PBF$_2$. Pulse broadening times ($\tau_d$) are derived from fits of PBFs to the data, and are compared with the predictions of a smoothed model of the Galactic electron distribution. Several lines of sight show excess broadening, which we model as clumps of high density scattering material. A global analysis of all available data finds that the pulse broadening scales with frequency, $\nu$, as \taud \propto\nu^{-\alpha} where $\alpha\sim 3.9\pm 0.2$. This is somewhat shallower than the value $\alpha=4.4$ expected from a Kolmogorov medium, but could arise if the spectrum of turbulence has an inner cutoff at $\sim$300--800 km. A few objects follow particularly shallow scaling laws (the mean scaling index \meanalpha \sim 3.1 \pm 0.1 and $\sim 3.8 \pm 0.2$ respectively for the case of PBF$_1$ and PBF$_2$), which may arise from large scale refraction or from the truncation of scattering screens transverse to the Earth--pulsar line of sight.Comment: Accepted for publication in the Astrophysical Journal; 32 pages, 11 figure

Pulsar Scintillation in the Local ISM: Loop I and Beyond

Recent pulsar scintillation measurements from Ooty, in conjunction with those from Parkes and other large radio telescopes, are used for a systematic investigation of the Local Interstellar Medium (LISM) towards the general direction of the Loop I Bubble. For several pulsars, clear evidence is found for an enhanced level of scattering which is over and above what can be accounted for by the enhanced scattering model for the Local Bubble. These results are interpreted in terms of enhanced scattering due to turbulent plasma associated with the Loop I shell. Useful constraints are obtained for the scattering properties of the shell. The inferred value for the scattering measure for the Loop I shell is found to be ~0.3 pc m^{-20/3}. Assuming a shell thickness ~5-10 pc, this implies an average strength of scattering in the shell that is ~100-200 times larger than that in the ambient ISM. An alternative explanation, where the enhanced level of scattering is due to a possible "interaction zone" between the Local Bubble and the Loop I Bubble, is also considered; it is found to be somewhat less satisfactory in explaining the observations. The best fit value for the scattering measure for such an interaction zone region is estimated to be ~1.1 pc m^{-20/3}. Further, several pulsars beyond ~1 kpc are found to show enhanced levels of scattering over and above that expected from this "two-bubble model." For some of the low-latitude pulsars, this is found to be due to enhanced scattering from plasma inside the intervening Sagittarius spiral arm. We discuss the implications of our results for the interpretation of scintillation data and for the general understanding of the LISM.Comment: 20 pages, 4 figures, Accepted for publication in AP

An all-sky search for continuous gravitational waves in the Parkes Pulsar Timing Array data set

We present results of an all-sky search in the Parkes Pulsar Timing Array (PPTA) Data Release 1 data set for continuous gravitational waves (GWs) in the frequency range from 5 × 10−9 to 2 × 10−7 Hz. Such signals could be produced by individual supermassive binary black hole systems in the early stage of coalescence. We phase up the pulsar timing array data set to form, for each position on the sky, two data streams that correspond to the two GW polarizations and then carry out an optimal search for GW signals on these data streams. Since no statistically significant GWs were detected, we place upper limits on the intrinsic GW strain amplitude h0 for a range of GW frequencies. For example, at 10−8 Hz our analysis has excluded with 95 per cent confidence the presence of signals with h0 ≥ 1.7 × 10−14. Our new limits are about a factor of 4 more stringent than those of Yardley et al. based on an earlier PPTA data set and a factor of 2 better than those reported in the recent Arzoumanian et al. paper. We also present PPTA directional sensitivity curves and find that for the most sensitive region on the sky, the current data set is sensitive to GWs from circular supermassive binary black holes with chirp masses of 109  M☉ out to a luminosity distance of about 100 Mpc. Finally, we set an upper limit of 4 × 10−3 Mpc−3 Gyr−1 at 95 per cent confidence on the coalescence rate of nearby (z ≤ 0.1) supermassive binary black holes in circular orbits with chirp masses of 1010  M☉

Wide-band profile domain pulsar timing analysis

We extend profile domain pulsar timing to incorporate wide-band effects such as frequencydependent profile evolution and broad-band shape variation in the pulse profile. We also incorporate models for temporal variations in both pulse width and in the separation in phase of the main pulse and interpulse. We perform the analysis with both nested sampling and Hamiltonian Monte Carlo methods. In the latter case, we introduce a new parametrization of the posterior that is extremely efficient in the low signal-to-noise regime and can be readily applied to a wide range of scientific problems. We apply this methodology to a series of simulations, and to between seven and nine years of observations for PSRs J1713+0747, J1744-1134 and J1909-3744 with frequency coverage that spans 700-3600 Mhz. We use a smooth model for profile evolution across the full frequency range, and compare smooth and piecewise models for the temporal variations in dispersion measure (DM). We find that the profile domain framework consistently results in improved timing precision compared to the standard analysis paradigm by as much as 40 per cent for timing parameters. Incorporating smoothness in the DM variations into the model further improves timing precision by as much as 30 per cent. For PSR J1713+0747, we also detect pulse shape variation uncorrelated between epochs, which we attribute to variation intrinsic to the pulsar at a level consistent with previously published analyses. Not accounting for this shape variation biases the measured arrival times at the level of ~30 ns, the same order of magnitude as the expected shift due to gravitational waves in the pulsar timing band