A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817.

GW170817 was the first gravitational-wave detection of a binary neutron-star merger. It was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of 40 megaparsecs. It has been proposed that the observed γ-ray, X-ray and radio emission is due to an ultra-relativistic jet being launched during the merger (and successfully breaking out of the surrounding material), directed away from our line of sight (off-axis). The presence of such a jet is predicted from models that posit neutron-star mergers as the drivers of short hard-γ-ray bursts. Here we report that the radio light curve of GW170817 has no direct signature of the afterglow of an off-axis jet. Although we cannot completely rule out the existence of a jet directed away from the line of sight, the observed γ-ray emission could not have originated from such a jet. Instead, the radio data require the existence of a mildly relativistic wide-angle outflow moving towards us. This outflow could be the high-velocity tail of the neutron-rich material that was ejected dynamically during the merger, or a cocoon of material that breaks out when a jet launched during the merger transfers its energy to the dynamical ejecta. Because the cocoon model explains the radio light curve of GW170817, as well as the γ-ray and X-ray emission (and possibly also the ultraviolet and optical emission), it is the model that is most consistent with the observational data. Cocoons may be a ubiquitous phenomenon produced in neutron-star mergers, giving rise to a hitherto unidentified population of radio, ultraviolet, X-ray and γ-ray transients in the local Universe.

A radio counterpart to a neutron star merger.

Gravitational waves have been detected from a binary neutron star merger event, GW170817. The detection of electromagnetic radiation from the same source has shown that the merger occurred in the outskirts of the galaxy NGC 4993, at a distance of 40 megaparsecs from Earth. We report the detection of a counterpart radio source that appears 16 days after the event, allowing us to diagnose the energetics and environment of the merger. The observed radio emission can be explained by either a collimated ultrarelativistic jet, viewed off-axis, or a cocoon of mildly relativistic ejecta. Within 100 days of the merger, the radio light curves will enable observers to distinguish between these models, and the angular velocity and geometry of the debris will be directly measurable by very long baseline interferometry.

Illuminating gravitational waves: A concordant picture of photons from a neutron star merger.

Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

Acute peritoneal dialysis as both cause and treatment of hypernatremia in an infant.

This report describes a 4-month-old infant with multisystem organ failure who developed severe hypernatremia (sodium 168 mEq/l) due to rapid free water removal associated with acute peritoneal dialysis instituted for fluid overload. The current report describes the pathophysiology of the hypernatremia, and its correction by low-sodium hypertonic peritoneal dialysis without compromising ultrafiltration or supplementing with free water. Although peritoneal dialysis can cause hypernatremia, a modified solute concentration in the dialysate can treat the hypernatremia successfully.

Relationship between arterial, mixed venous, and internal jugular carboxyhemoglobin concentrations at low, medium, and high concentrations in a piglet model of carbon monoxide toxicity.

OBJECTIVE: This study tested the hypothesis that mixed venous carboxyhemoglobin concentrations (V-COHb) and internal jugular carboxyhemoglobin concentrations (I-COHb) accurately predict arterial carboxyhemoglobin concentrations (A-COHb). In addition, this study tested the hypothesis that there is a high correlation at low (COHb, 0% to 10%), moderate (COHb, >10% to 40%), and high (COHb, >40%) concentrations between V-COHb, I-COHb, and A-COHb. DESIGN: The study was a prospective comparison of A-COHb, V-COHb, and I-COHb concentrations in piglets exposed to increasing concentrations of carbon monoxide over 6 hrs to achieve a concentration of > or =60% COHb. Carboxyhemoglobin measurements were evaluated by analysis of variance and correlation analysis. Agreement between V-COHb and A-COHb concentrations was examined by using a plot of arteriovenous differences against the mean of the two measurements. INTERVENTION: We simultaneously sampled arterial, mixed venous, and internal jugular blood every 30 mins over the 6-hr study period. RESULTS: Two hundred fifty arterial and mixed venous COHb concentrations were obtained, and 214 internal jugular COHb concentrations were obtained. One hundred additional arterial, mixed venous, internal jugular, and peripheral COHb concentrations were obtained. Correlation between samples at each concentration revealed r2 > = .94. CONCLUSION: Venous COHb concentrations predict arterial COHb concentrations with a high degree of accuracy and are correlated at low, moderate, and high concentrations of carbon monoxide exposure. Arterial or venous samples can be used to accurately measure COHb concentrations.

Effects of dantrolene on cooling times and cardiovascular parameters in an immature porcine model of heatstroke.

OBJECTIVE: To evaluate the effects of dantrolene on cooling times and cardiovascular parameters in an immature porcine model of heatstroke. DESIGN: Prospective, randomized, controlled, multigroup study. SETTING: Research animal laboratory. SUBJECTS: Yorkshire piglets (n = 16), 4 to 5 wks of age, 3.5 to 4.5 kg of body weight. INTERVENTIONS: Animals were slowly heated with a radiant heat source to 43 degrees C and then maintained at this temperature for 30 mins. The animals were then removed from the heat source and randomized into one of four groups to receive either conventional cooling methods consisting of fluid resuscitation with 0.9% sodium chloride solution, sponging with room temperature water, mechanical fanning, and gastric lavage with iced 0.9% sodium chloride solution (group 1), conventional cooling methods and dantrolene (group 2), conventional cooling methods and dantrolene's vehicle mannitol (group 3), or no treatment (group 4). Cooling times, defined as the time required to reach a core body temperature of 38.5 degrees C, and cardiovascular parameters for each group were then compared. MEASUREMENTS AND MAIN RESULTS: Animals in groups 1, 2, and 3 had significantly (p < .05) lower core body temperatures than animals that received no treatment at the conclusion of the experiment. Piglets in groups 2 and 3 had faster cooling times than piglets in group 1 (p < .05). However, there was no statistically significant difference in cooling times between the animals in groups 2 and 3. There were no statistically significant differences in heart rate, mean arterial pressure, central venous pressure, pulmonary artery occlusion pressure, or systemic vascular resistance index between animals in groups 1, 2, or 3. Group 3 piglets had higher cardiac indices and stroke indices than the piglets in the other groups (p < .05). CONCLUSIONS: Therapeutic interventions with conventional cooling or conventional cooling and dantrolene provided significant improvement in cardiovascular function in an immature porcine heatstroke model. Dantrolene, given with conventional cooling methods, offered no significant improvement in cardiovascular parameters compared with conventional cooling methods alone. Dantrolene significantly shortened the cooling time compared with conventional cooling but did not significantly shorten the cooling time compared with its vehicle, mannitol. Although dantrolene significantly shortened the cooling time, it did not appear to be superior compared with conventional cooling methods in treating heatstroke in this immature porcine heatstroke model.

Differentiation of sinus rhythms from supraventricular tachydysrhythmias by activation sequence and timing.

Implantable device detection of tachydysrhythmias remains unreliable and inexact. False responses may occur because of misinterpretation of sinus tachycardia (ST) as a supraventricular tachydysrhythmia (SVTD). Timing of atrioventricular (AV) activation and ventricular dispersion identified and discriminated between ST and SVTDs in 11 dogs. Three bipolar epicardial electrodes recorded left atrial and left and right ventricular depolarizations simultaneously during normal sinus rhythm (NSR) (mean of 5 beats in 11/11 dogs), ST produced by phlebotomy (50 beats in 10 episodes in 6/11) or isoproterenol infusion (105 beats in 21 episodes in 10/11), sinus bradycardia (SB) produced by vagal stimulation (140 beats in 29 episodes in 10/11), and during atrial flutter (AFL) (15 beats in 3 episodes in 3/11) and atrial fibrillation (AF) (152 beats in 31 episodes in 9/11) induced by programmed electrical stimulation. During lidocaine infusion, NSR (55 beats in 11 episodes in 10/11 dogs), SB (84 beats in 17 episodes in 7/11), AFL (10 beats in 2 episodes in 1/11), and AF (103 beats in 21 episodes in 7/11) were recorded. During isoproterenol infusion, SB (45 beats in 9 episodes in 5/11), AFL (15 beats in 3 episodes in 2/11), and AF (64 beats in 13 episodes in 5/11) were recorded in addition to ST. The interval between the left atrial and left ventricular intrinsic deflections (A-V1) and between the left and right ventricular intrinsic deflections (V1-V2) of each beat was measured. The mean value (msec) of A-V1 and V1-V2 in each episode was compared to NSR in the same dogs. A difference of greater than or equal to 16 ms was used for differentiation. In all cases except SB with first-degree AV block, V1-V2 in each episode was insignificant (0-14 msec), categorizing the rhythms as supraventricular. During NSR, ST and SB without AV block, delta A-V1 was small (0-15 msec). In contrast delta A-V1 was greater than or equal to 16 ms in 6/8 episodes of AFL. The remaining two episodes could be differentiated by the greater number of atrial versus ventricular beats. AF could be detected by the variability of A-V1.(ABSTRACT TRUNCATED AT 250 WORDS)

Complications of pediatric obstructive sleep apnea.

Obstructive apnea, especially OSA, is a common problem in pediatric practice. In young infants, craniofacial anomalies may be the most common contributor to OSA. Complications include failure to thrive, metabolic alkalosis, and respiratory distress which can be life-threatening. In children over the age of 2 years, adenoidal and tonsillar hypertrophy is more commonly the cause of upper airway obstruction. The complications of growth failure, cor pulmonale, and adult respiratory distress syndrome were discussed. Obstructive sleep apnea can cause significant complications in both infants and children. These problems can be life-threatening, cause delay in growth and development, or cause subtle long-term learning disabilities. Surgical management of the airway should correct the metabolic and cardiorespiratory disorders. The correction of learning disabilities has not yet been demonstrated.

Limb deficiency in an infant with Smith-Lemli-Opitz syndrome.

We describe a 46,XY newborn infant with Smith-Lemli-Opitz syndrome (SLOS) with multiple congenital anomalies including female external genitalia, a testis palpable in each labium majus, a cone-shaped cervix, and normal vagina. Additional anomalies included cleft palate, total anomalous pulmonary venous return, and striking limb defects (ectrodactyly of the left upper limb, radial aplasia, and monodactyly of the right upper limb). To our knowledge, this is the first report of SLOS associated with limb deficiency and the third associated with total anomalous pulmonary venous return. Our patient demonstrates that limb deficiencies may be a rare component manifestation in this syndrome of multiple congenital anomalies.

Differentiation of arrhythmias in the dog by measurement of activation sequence using an atrial and two ventricular electrodes.

Timing of atrioventricular activation and ventricular dispersion identifies and discriminates between beats of different origin. In eight dogs, three bipolar epicardial electrodes recorded left atrial and left and right ventricular depolarizations simultaneously during arrhythmias induced by programmed electrical stimulation and coronary artery occlusion and release. The interval between the left atrial and left ventricular intrinsic deflections (A-V1) and between the left ventricular and right ventricular intrinsic deflections (V1-V2) of each beat was measured. Recordings were of normal sinus rhythm (NSR) (mean of five beats in 8/8 dogs), atrial flutter (AFL) (five beats of one episode), atrial fibrillation (AF) (144 beats in 29 episodes in 7/8), monomorphic ventricular tachycardia (MVT) (24 beats with six morphologies in 2/8), polymorphic ventricular tachycardia (PVT) (63 beats in 15 episodes in 5/8) and premature ventricular contractions (PVC) (29 beats with 29 morphologies in 5/8). Supraventricular rhythms can be differentiated from ventricular rhythms by V1-V2 timing. The mean difference in V1-V2 during AFL and AF vs NSR was 1 ms (range of 0-3 ms). The change from sinus during MVT ranged from 18 to 43 ms (m 31 ms) and during PVC 10 to 75 ms (m 38 ms). Thirty-five of 35 of these ectopic ventricular morphologies exhibited 10 ms or more timing difference compared to corresponding beats of NSR. PVT was consistently distinguished from supraventricular rhythms and MVT by the variability of V1-V2. A-V1 intervals can be used to distinguish supraventricular arrhythmias from sinus rhythm; a 32 ms difference existed for AFL. AF could be detected by the variability in AV1.(ABSTRACT TRUNCATED AT 250 WORDS)

Trisomy 18 score: a rapid, reliable diagnostic test for trisomy 18.

We developed a bedside scoring system for diagnosis of trisomy 18 in the immediate neonatal period. Points are assigned for the presence of features known to occur in trisomy 18: five points for the presence of features previously reported in 50% or more of affected infants; three points for features reported to occur in between 10% and 50% of affected individuals; and one point for features known to occur in less than 10% of infants with the disorder. Using the scoring system, we evaluated two cohorts of patients: those in whom a diagnosis of trisomy 18 was previously established (retrospective group) and those in whom the diagnosis was suspected but not yet proved (prospective group). The average score in the retrospective series (n = 25) was 96.7, and no patient scored less than 70. Twenty-two patients were evaluated prospectively; in all cases the presence or absence of trisomy 18 was correctly predicted. The average score in the 11 patients without trisomy 18 was 41.4, and all patients scored 60 or less. In the 11 patients confirmed to have trisomy 18, the average score was 94.3, with a range of 70 to 113. This scoring system is an accurate, reproducible method for predicting trisomy 18 in neonates with multiple congenital malformations.