Prevention of hypotension after spinal anaesthesia for caesarean section: a systematic review and network meta-analysis of randomised controlled trials.

Spinal anaesthesia for caesarean section commonly causes maternal hypotension. This systematic review and network meta-analysis compared methods to prevent hypotension in women receiving spinal anaesthesia for caesarean section. We selected randomised controlled trials that compared an intervention to prevent hypotension with another intervention or inactive control by searching MEDLINE and Embase, Web of Science to December 2018. There was no language restriction. Two reviewers extracted data on trial characteristics, methods and outcomes. We assessed risk of bias for individual trials (Cochrane tool) and quality of evidence (GRADE checklist). We assessed 109 trials (8561 women) and 12 different methods that resulted in 30 direct comparisons. Methods ranked by OR (95%CI) from most effective to least effective were: metaraminol 0.11 (0.04-0.26); norepinephrine 0.13 (0.06-0.28); phenylephrine 0.18 (0.11-0.29); leg compression 0.25 (0.14-0.43); ephedrine 0.28 (0.18-0.43); colloid given before induction of anaesthesia 0.38 (0.24-0.61); angiotensin 2, 0.12 (0.02-0.75); colloid given after induction of anaesthesia 0.52 (0.30-0.90); mephentermine 0.09 (0.01-1.30); crystalloid given after induction of anaesthesia 0.78 (0.46-1.31); and crystalloid given before induction of anaesthesia 1.16 (0.76-1.79). Phenylephrine caused maternal bradycardia compared with control, OR (95%CI) 0.23 (0.07-0.79). Ephedrine lowered umbilical artery pH more than phenylephrine, standardised mean difference (95%CI) 0.78 (0.47-1.49). We conclude that vasopressors should be given to healthy women to prevent hypotension during caesarean section with spinal anaesthesia.

Theoretical estimates of spherical and chromatic aberration in photoemission electron microscopy.

We present theoretical estimates of the mean coefficients of spherical and chromatic aberration for low energy photoemission electron microscopy (PEEM). Using simple analytic models, we find that the aberration coefficients depend primarily on the difference between the photon energy and the photoemission threshold, as expected. However, the shape of the photoelectron spectral distribution impacts the coefficients by up to 30%. These estimates should allow more precise correction of aberration in PEEM in experimental situations where the aberration coefficients and precise electron energy distribution cannot be readily measured.

Light propagation and interaction observed with electrons.

We discuss possibilities for a microscopic optical characterization of thin films and surfaces based on photoemission electron microscopy. We show that propagating light with wavelengths across the visible range can readily be visualized, and linear and non-linear materials properties can be evaluated non-invasively with nanometer spatial resolution. While femtosecond temporal resolution can be achieved in pump-probe-type experiments, the interferometric approach presented here has typical image frame times of ~200 fs.

Stabilization of HIF-2α through redox regulation of mTORC2 activation and initiation of mRNA translation.

Hypoxia inducible factor-2α (HIF-2α) has a critical role in renal tumorigenesis. HIF-2α is stabilized in von Hippel-Lindau (VHL)-deficient renal cell carcinoma through mechanisms that require ongoing mRNA translation. Mammalian target of rapamycin (mTOR) functions in two distinct complexes: Raptor-associated mTORC1 and Rictor-associated mTORC2. Rictor-associated mTORC2 complex has been linked to maintaining HIF-2α protein in the absence of VHL; however, the mechanisms remain to be elucidated. Although Raptor-associated mTORC1 is a known key upstream regulator of mRNA translation, initiation and elongation, the role of mTORC2 in regulating mRNA translation is not clear. Complex assembly of the mRNA cap protein, eukaryotic translation initiation factor 4 (eIF4)E, with activators (eIF4 gamma (eIF4G)) and inhibitors (eIF4E-binding protein 1 (4E-BP1)) are rate-limiting determinants of mRNA translation. Our laboratory has previously demonstrated that reactive oxygen species, mediated by p22(phox)-based Nox oxidases, are enhanced in VHL-deficient cells and have a role in the activation of Akt on S473, a site phosphorylated by the mTORC2 complex. In this study, we examined the role of Rictor-dependent regulation of HIF-2α through eIF4E-dependent mRNA translation and examined the effects of p22(phox)-based Nox oxidases on TORC2 regulation. We demonstrate for the first time that mTORC2 complex stability and activation is redox sensitive, and further defined a novel role for p22(phox)-based Nox oxidases in eIF4E-dependent mRNA translation through mTORC2. Furthermore, we provide the first evidence that silencing of p22(phox) reduces HIF-2α-dependent gene targeting in vitro and tumor formation in vivo. The clinical relevance of these studies is demonstrated.

Simultaneous and independent adaptive correction of spherical and chromatic aberration using an electron mirror and lens combination.

We present a theoretical analysis of an electrostatic triode mirror combined with an einzel lens for the correction of spherical and chromatic aberration. We show that this device adaptively corrects spherical and chromatic aberration simultaneously and independently. Chromatic aberration can be compensated over a relative range of -38% to +100%, and spherical aberration over ±100% range. We compare the analytic calculation with a numerical simulation and show that the two descriptions agree to within 5% in the relevant operating regime of the device.

Aberrations in asymmetrical electron lenses.

Starting from well established knowledge in light-optics we explore the question if electron-optical aberration can be improved in asymmetrical electron lenses. We show that spherical as well as chromatic aberration coefficients are reduced in asymmetric electrostatic einzel lenses when the center electrode is moved away from the center position towards the entrance electrode. Relative improvements up to 40% for both the chromatic and the spherical aberration coefficients can be obtained. We use analytical and numerical calculations to confirm this result for exemplary cases of a lens with fixed length and working distance. The agreement of the two calculation methods is very good. We then derive an estimate for the electron-optical aberration coefficients from light-optics. The derived expressions for chromatic and spherical aberrations are somewhat simpler than the ones derived from electron-optics as they involve integrals only over the electrostatic potential, not over the electron paths. The estimated formulas still agree well with the electron optical calculations. Overall, we are tempted to suggest that the enormous knowledge base of light optics can provide considerable guidance for electron-optical applications.

Adaptive aberration correction using a triode hyperbolic electron mirror.

A converging electron mirror can be used to compensate spherical and chromatic aberrations in an electron microscope. This paper presents an analytical solution to a novel triode (three electrode) hyperbolic mirror as an improvement to the well-known diode (two electrode) hyperbolic mirror for aberration correction. A weakness of the diode mirror is a lack of flexibility in changing the chromatic and spherical aberration coefficients independently without changes in the mirror geometry. In order to remove this limitation, a third electrode can be added. We calculate the optical properties of the resulting triode mirror analytically on the basis of a simple model field distribution. We present the optical properties-the object/image distance, z(0), and the coefficients of spherical and chromatic aberration, C(s) and C(c), of both mirror types from an analysis of electron trajectories in the mirror field. From this analysis, we demonstrate that while the properties of both designs are similar, the additional parameters in the triode mirror improve the range of aberration that can be corrected. The triode mirror is also able to provide a dynamic adjustment range of chromatic aberration for fixed spherical aberration and focal length, or any permutation of these three parameters. While the dynamic range depends on the values of aberration correction needed, a nominal 10% tuning range is possible for most configurations accompanied by less than 1% change in the other two properties.

Distribution of oxygen across the surface of the human cornea during soft contact lens wear.

PURPOSE: To determine whether tear mixing occurs beneath soft contact lenses, we examined the effect of blinking on the oxygen distribution across the corneal surface beneath a nonuniform thickness lens. METHODS: A custom-designed twin polarographic oxygen sensor assembly was used to simultaneously measure the equivalent oxygen percentage (EOP) at central and peripheral corneal locations of 10 human subjects beneath a -6.00 D thin-design hydroxyethyl mathacrylate (HEMA) lens. A -0.25 D lens served as a control. Each lens was worn for 5 min under static (no blinking) and dynamic (12 and 60 blinks/min) conditions. RESULTS: A significantly greater EOP (p = 0.006) was observed at the central (vs. peripheral) cornea during static and dynamic lens wear; central and peripheral oxygenation were unaffected by blinking. CONCLUSIONS: Tear mixing is insignificant beneath thin-design HEMA lenses; therefore, oxygenation across the corneal surface beneath such lenses is best predicted from the lens thickness profile rather than average thickness.

An evaluation of the nasolabial angle and the relative inclinations of the nose and upper lip.

The purpose of this study was to develop a consistent and reproducible method of constructing a nasolabial angle that would also permit an evaluation of the relative inclination of the lower border of the nose and the upper lip, as well as their relationship to each other. Comparison of repeated individual measurements of soft tissue profile landmarks on 15 subjects, as completed by four orthodontists, revealed that the proposed method of constructing the nasolabial angle was consistent and reproducible by the same orthodontist and among different orthodontists. Normative data for the three nasolabial parameters were produced from a sample of 104 young white adults determined by the authors to have well-balanced faces. Mean and standard deviation values from this pooled sample demonstrated a lower border of the nose to Frankfort horizontal plane angle at 18 degrees +/- 7 degrees, upper lip to Frankfort horizontal plane angle 98 degrees +/- 5 degrees, and nasolabial angle 114 degrees +/- 10 degrees. No statistically significant difference was demonstrated between the values for men and women in this study, but the women did have a slightly larger nasolabial angle. A linear comparison of the three nasolabial parameters with six skeletal measurements revealed no significant relationship between the soft tissue profile of the nasolabial region and the underlying skeletal relationships.

Distraction resection arthroplasty of the wrist.

Proximal row carpectomy should not be done if wrist degeneration includes cartilage destruction of the capitate or lunate fossa of the radius; yet total wrist arthroplasty has been disappointing for treatment of osteoarthritis. We have used a technique we call distraction resection wrist arthroplasty in such cases. We retrospectively reviewed distraction resection wrist arthroplasty in 14 wrists and compared them to nine patients who had PRC; average follow-up was 32 months. Three patients had spastic contractures and 20 had operation for painful osteoarthritis. Patient satisfaction was high but there were four failures requiring arthrodesis (1 PRC, 3 DRA). Average postoperative wrist motion was 41 degrees of extension, 38 degrees of flexion, 11 degrees of radial deviation, and 13 degrees of ulnar deviation. Static strength averaged almost two thirds of the uninvolved side and dynamic power more than half. Differences between the DRA and PRC patients were not statistically significant in single or aggregate analysis. We believe that distraction technique extends the indications for biologic arthroplasty to patients whose only prior option was wrist arthrodesis.

Determinants of the initial comfort of hydrogel contact lenses.

A double-masked, randomized study was conducted to determine the effects of power and water content on the initial comfort of hydrogel contact lenses in 10 unadapted subjects. Three lens powers (-0.50, -5.00, and -10.00 D) were used in each of three water contents (38, 55, and 70%). A significant negative correlation (p less than 0.05) was found between lens comfort and lens water content; that is, lower water content lenses of lesser bulk were more comfortable than higher water content lenses. These data will allow practitioners to predict patient awareness to various lens types. When fitting hydrogel lenses to an apprehensive patient who has not worn contact lenses previously, it may be advisable to insert a thin, low water content lens initially, thereby maximizing lens comfort.