An update on the current management of hyponatremia

Hyponatremia is the most common electrolyte disorder in hospitalized patients. According to the Edelman equation, hyponatremia usually develops due to a gain of free water, a loss of serum sodium or a combination of both. Investigating the causes of hyponatremia and consequent correction of the electrolyte disorder can be challenging. In this review we give an overview on the mechanisms leading to hyponatremia and in a further step, the correction of hyponatremia is discussed in detail with sections on: rate of correction, treatment with respect to volume state, risks of correction and a discussion of vasopressin receptor antagonists.

Night myopia studied with an adaptive optics visual analyzer

PURPOSE

Eyes with distant objects in focus in daylight are thought to become myopic in dim light. This phenomenon, often called "night myopia" has been studied extensively for several decades. However, despite its general acceptance, its magnitude and causes are still controversial. A series of experiments were performed to understand night myopia in greater detail.

METHODS

We used an adaptive optics instrument operating in invisible infrared light to elucidate the actual magnitude of night myopia and its main causes. The experimental setup allowed the manipulation of the eye's aberrations (and particularly spherical aberration) as well as the use of monochromatic and polychromatic stimuli. Eight subjects with normal vision monocularly determined their best focus position subjectively for a Maltese cross stimulus at different levels of luminance, from the baseline condition of 20 cd/m(2) to the lowest luminance of 22 × 10(-6) cd/m(2). While subjects performed the focusing tasks, their eye's defocus and aberrations were continuously measured with the 1050-nm Hartmann-Shack sensor incorporated in the adaptive optics instrument. The experiment was repeated for a variety of controlled conditions incorporating specific aberrations of the eye and chromatic content of the stimuli.

RESULTS

We found large inter-subject variability and an average of -0.8 D myopic shift for low light conditions. The main cause responsible for night myopia was the accommodation shift occurring at low light levels. Other factors, traditionally suggested to explain night myopia, such as chromatic and spherical aberrations, have a much smaller effect in this mechanism.

CONCLUSIONS

An adaptive optics visual analyzer was applied to study the phenomenon of night myopia. We found that the defocus shift occurring in dim light is mainly due to accommodation errors.

Binocular adaptive optics vision analyzer with full control over the complex pupil functions

We present a binocular adaptive optics vision analyzer fully capable of controlling both amplitude and phase of the two complex pupil functions in each eye of the subject. A special feature of the instrument is its comparatively simple setup. A single reflective liquid crystal on silicon spatial light modulator working in pure phase modulation generates the phase profiles for both pupils simultaneously. In addition, another liquid crystal spatial light modulator working in transmission operates in pure intensity modulation to produce a large variety of pupil masks for each eye. Subjects perform visual tasks through any predefined variations of the complex pupil function for both eyes. As an example of the system efficiency, we recorded images of the stimuli through the system as they were projected at the subject's retina. This instrument proves to be extremely versatile for designing and testing novel ophthalmic elements and simulating visual outcomes, as well as for further research of binocular vision.

Effects of different media on proliferation and differentiation capacity of canine, equine and porcine adipose derived stem cells

Adult stem cells are of particular interest for therapeutic use in the field of regenerative medicine. Adipose-derived mesenchymal stem cells (ASCs) are an attractive stem cell source for all fields of regenerative medicine because adipose tissue - and therewith cells - can easily be harvested from each donor. However, common expansion using fetal bovine serum (FBS) can not be used for clinical applications as xenogenic proteins must be avoided. Adipose tissue from equine, canine and porcine donors was digested with collagenase to isolate ASCs. ASCs were either expanded in a cell culture medium supplemented with FBS or in a serum-free medium (UltraCulture; UC) supplemented with a serum substitute (UltroserG). From all three animal species, the adipogenic and osteogenic differentiation potential of ASCs cultured with different media was analyzed in vitro. Cell proliferation analysis showed a population doubling time of 48-68 h for canine cells, 54-65 h for porcine cells and 54-70 h for equine cells, expanded in different media. Except for porcine ASCs, cells cultured in media supplemented with FBS grew faster than cells expanded in UC medium with UltroserG. Yet, all cells maintained their potential to differentiate into adipocytes and osteoblasts. UltraCulture medium containing UltroserG can for all examined species be recommended if FBS needs to be avoided in the expansion of donor-derived (stem) cells.

Binocular visual simulation of a corneal inlay to increase depth of focus

PURPOSE

To investigate binocular visual acuity and depth of focus when one eye forms images through a typical pupil diameter aperture (4 mm) and the other eye through a small pupil of 1.5-mm diameter.

METHODS

Using a recently developed adaptive optics binocular visual simulator, through focus monocular and binocular visual acuity were measured in three subjects under specially simulated visual conditions: right eyes had "small aperture" vision through a 1.5-mm pupil diameter and left eyes had normal vision through 4-mm pupil diameter. The measurements were performed in photopic and mesopic conditions.

RESULTS

An increase in binocular and monocular (for the small-aperture eye) depth of focus was measured with respect to the 4-mm pupil diameter eye. It ranged from 1 to 1.5 diopter (D) depending on the threshold requirement and the visibility conditions. For photopic conditions, the J2 visual acuity level was reached at 1 D of defocus for the 4-mm pupil diameter case, while for the 1.5-mm, the J2 level was reached at 2.5 D. Binocular summation occurred only in far vision conditions (no defocus added). For near vision, binocular visual acuity closely followed the values of monocular visual acuity for the eye with the smaller aperture.

CONCLUSIONS

The small-aperture effect to increase depth of focus in the human eye was successfully implemented in a binocular visual simulator. Although certain limitations exist, the small-aperture approach provided a simple but attractive solution to increase depth of focus in the human eye.

["Truth at the bedside"]

BACKGROUND AND RESEARCH QUESTION

Discussions with seriously ill patients are part of physicians' tasks. These discussions are very demanding with respect to communication skills. In this paper we present the concept of an obligatory postgraduate course for physicians on breaking bad news and the results of the course evaluation.

RESEARCH PARTICIPANTS AND METHODS

Physicians of 4 German hospitals in which the module was offered as an obligatory inhouse course. An interventional study without control group was carried out in which a questionnaire (closed-ended questions and Likert scales as well as open-ended questions) was distributed before and immediately after the course.

RESULTS

186 physicians (response rate: 88.6 %) participated in the study. 102 respondents (54.8 %) had broken bad news more than five times per month. 75 physicians (40.3 %) indicated that they had never participated in a teaching module on this topic prior to the course. Discussions about the end of life and disclosure about recurrence of the disease were rated most frequently as very difficult communication situations. Compared with the beginning of the course the respondents rated their communication skills significantly better at the end of the course. The course's relevance for clinical practice, teaching methods and the organisation of the course were rated positively.

CONCLUSION

The feedback of the participants indicates the practical relevance of professional training on difficult communication situations such as breaking bad news. The improved rating of communication skills may be interpreted as a positive effect of the course. In our view, observational studies as well as interprofessional teaching modules contribute to improved professional communication with patients about diagnosis, prognosis and treatment options.

Observation and Characterization of the Pseudomorphic to Stable Phase Transitions of Fe1-xSi on Si(111)

Pseudomorphic Fe1-x Si films have been grown on Si(111) by molecular beam epitaxy (MBE) at room temperature (RT). Structural investigations revealed that the phase crystallizes in the cubic CsCl structure with a lattice constant close to half that of Si. Upon annealing, films thicker than 15Å undergo a phase transition to the stable bulk ε-FeSi, either in epitaxial or in polycrystalline form at temperatures around 300°C. Thinner films do not transform to the ε-FeSi phase. Instead they exhibit a continuous increase of the Si content up to the stoichiometry of FeSi2 The CsCl symmetry persists, exept for prolonged annealing close to the transition to βFeSi2, where γ-FeSi2 (CaF2 ) forms as an intermediate phase.

Relationship between wave aberrations and histological features in ex vivo porcine crystalline lenses

Wave aberrations of isolated ex vivo porcine crystalline lenses were measured by using a point-diffraction interferometer. This method allowed us to gain greater insight into the detailed aberration structure of eye lenses showing systematic presence of some dominant aberrations. In order of significance, astigmatism together with spherical aberration, coma, and trefoil are the main aberrations present in all lenses. We found a high correlation between the axis of both astigmatism and trefoil with the Y-shaped suture planes of the lens, revealing a subtle relationship between the induced aberrations and the histological features.

[Intramedullary nailing of proximal tibial fractures. Complications and risk factors]

INTRODUCTION

We performed a consecutive study on patients with proximal tibial fractures without joint participation to determine the early clinical and radiological outcome.

PATIENTS

From January 2000 to December 2005, 22 fractures of the proximal and proximal diaphyseal tibia without joint participation were operated on using the new tibia nail. A total of 18 patients (82%) completed full follow-up after 6 weeks and 3 and 6 months.

RESULTS

Two primary and one secondary malalignment were observed Two of them were initially polytraumatised. Furthermore, two patients developed a delayed union, and one non-union occurred. Risk factors for limited bony consolidation were smoking and an open fracture. Screw or nail breakage did not occur, and no infection was observed.

Wavefront measurements of phase plates combining a point-diffraction interferometer and a Hartmann-Shack sensor

A dual setup composed of a point diffraction interferometer (PDI) and a Hartmann-Shack (HS) wavefront sensor was built to compare the estimates of wavefront aberrations provided by the two different and complementary techniques when applied to different phase plates. Results show that under the same experimental and fitting conditions both techniques provide similar information concerning the wavefront aberration map. When taking into account all Zernike terms up to 6th order, the maximum difference in root-mean-square wavefront error was 0.08 microm, and this reduced up to 0.03 microm when excluding lower-order terms. The effects of the pupil size and the order of the Zernike expansion used to reconstruct the wavefront were evaluated. The combination of the two techniques can accurately measure complicated phase profiles, combining the robustness of the HS and the higher resolution and dynamic range of the PDI.

Isotopic dependence of the nuclear caloric curve

The A/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of (124)Sn and radioactive beams of (124)La and (107)Sn at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects (DeltaT approximately 0.6 MeV) appear for residue production near the onset of multifragmentation.