Urea for hyponatraemia due to the syndrome of inappropriate antidiuretic hormone secretion.

BACKGROUND: Hyponatraemia due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH) can pose a therapeutic challenge. After fluid restriction, urea is recommended as a second-line treatment by Dutch and European treatment guidelines. Data on this practice are still scarce. We introduced urea for the treatment of SIADH in our hospital and prospectively collected data on its effectiveness and tolerability. METHODS: In hospitalised patients with a serum sodium level ≤ 129 mmol/l due to SIADH, urea in a dosage of 0.25-0.50 g/kg/day was indicated if prescribed fluid restriction had no effect or could not be applied. Measurement of serum sodium was performed at baseline, after the first and second day of urea therapy and at the end of the first inpatient treatment episode (EIT). The primary outcomes were normonatraemia (serum sodium level 135-145 mmol/l) at EIT and discontinuation of urea due to side effects. RESULTS: Thirteen patients were treated with urea over a median of 5 days (range 2-10 days). The median serum sodium level at baseline was 124 mmol/l (IQR 122-128), which increased to 128 mmol/l (IQR 123-130) (p = 0.003) after the first dose of urea and to 130 mmol/l (IQR 127-133) (p = 0.002) after the second dose of urea. Normonatraemia at EIT was observed in 8 (62%) patients. Seven (54%) patients reported distaste. In one of these patients, urea was discontinued because of nausea. Overcorrection was not observed. CONCLUSION: Our data show that urea is an effective treatment for hospitalised patients with SIADH. Distaste was a frequent side effect, but usually did not lead to early treatment discontinuation.

[A man with black blood]. / Een man met zwart bloed.

A 71-year-old man was admitted to the emergency room after high-energy trauma. He suddenly deteriorated several hours after an epidural providing local anaesthetics. At that time, his blood was black and the methaemoglobin level was 69 percent. After administration of methylene blue, he made a full clinical and biochemical recovery.

Probing microelectromechanical systems in an environmentally controlled chamber using long working distance interferometry.

It is well known that the environment in which micromechanical systems operate significantly affects their performance. It is, therefore, important to characterize micromachine behavior in environments where the humidity, pressure, and chemical composition of the ambient can be precisely controlled. Achieving such a level of environmental control presents significant challenges in view of the required instrumentation. To that end, a custom micromachine characterization system is built that allows for full environmental control (pressure, humidity, and gas composition) while retaining full micromachine characterization techniques (long working distance interferometry, electrical probe connectivity, actuation scripting capability). The system also includes an effective in situ surface cleaning mechanism. As an example of the system's utility, a microcantilever crack healing experiment is conducted and surface adhesion energy measurements are tracked over time after a step change in humidity is applied.

Insulin's microvascular vasodilatory effects are inversely related to peripheral vascular resistance in overweight, but insulin-sensitive subjects.

OBJECTIVE: The mechanisms underlying obesity-related hypertension are incompletely understood. Microvascular dysfunction might play a role by increasing peripheral vascular resistance (PVR). Metabolic and microvascular effects of insulin are impaired in obesity, but how these impairments contribute to disturbed blood pressure homeostasis is unclear. Specifically, it is unknown whether local microvascular vasoactive effects of insulin play a role in determining systemic vascular resistance. The aim of this study was to investigate the association between PVR and local microvascular effects of insulin. DESIGN AND METHODS: Thirty-seven healthy, overweight subjects (age 25-55 years, BMI 25-30 kg/m(2) ) were cross-sectionally studied. Local insulin-mediated vasodilation was measured using skin laser Doppler fluxmetry combined with transcutaneous iontophoresis of insulin. For comparison, local vasodilatory effects of acetylcholine and sodium nitroprusside were measured. PVR was calculated from mean arterial pressure and cardiac output, assessed by pulse-dye densitometry. RESULTS: PVR was inversely correlated with insulin-mediated vasodilation (r = -0.50; P < 0.01). This finding was maintained after adjustment for age, sex, blood pressure, and smoking. PVR was not associated with local microvascular effects of acetylcholine. CONCLUSIONS: Our study in overweight subjects suggests that insulin's role in the microvasculature may contribute to blood pressure control.

Rupture work of pendular bridges.

Capillary bridging can generate substantial forces between solid surfaces. Impacted technologies and sciences include micro- and nanomachining, disk drive interfaces, scanning probe microscopy, biology, and granular mechanics. Existing calculations of the rupture work of capillary bridges do not consider the thermodynamics relating to the evaporation that can occur in the case of volatile liquids. Here, we show that the occurrence of evaporation decreases the rupture work by a factor of about 2. The decrease arises from heat taken from the surroundings that is converted into work. The treatment is based on a thermodynamic control-volume analysis of the pendular bridge geometry. We extend the mathematical formulation of Orr et al., solving the meniscus problem exactly for non-wetting surfaces. The extension provides analytical results for conditions at the rupture point and at a possible inflection point and for the rupture work. A simple equation (eq 32) is shown to fit the rupture work for the two cases over a meniscus curvature range of 3 orders of magnitude. Coefficients for the equation are given in tabular form for different contact angle pairs.

Thermodynamics of capillary adhesion between rough surfaces.

According to the Dupré equation, the work of adhesion is equal to the surface energy difference in the separated versus the joined materials minus an interfacial energy term. However, if a liquid is at the interface between two solid materials, evaporation or condensation takes place under equilibrium conditions. The resulting matter exchange is accompanied by heat flow, and can reduce or increase the work of adhesion. Accounting for the energies requires an open-system control volume analysis based on the first law of thermodynamics. Depending on whether evaporation or condensation occurs during separation, a work term that is negative or positive must be added to the surface energy term to calculate the work of adhesion. We develop and apply this energy balance to several different interface geometries and compare the work of adhesion to the surface energy created. The model geometries include a sphere on a flat with limiting approximations and also with an exact solution, a circular disc, and a combination of these representing a rough interface. For the sphere on a flat, the work of adhesion is one half the surface energy created if equilibrium is maintained during the pull-off process.

Complications after mandibular third molar extraction.

The records of 1,797 patients were retrospectively examined to analyze the possible relationships between postoperative complications following mandibular third molar extraction and parameters such as age, sex, indication for surgery, position of the molar, surgical experience, surgical technique, and postoperative care. Older patients tended to suffer more often from complications. Surgery performed while there were signs of pericoronal inflammation also resulted in more complications. There was no statistically significant difference in the mean complication rate arising from surgery performed by staff members and the rate when surgery was performed by residents. There seems to be no reason for patients to return routinely for removal of resorbable sutures or other postoperative care because this practice does not result in a decrease in postoperative symptoms.

Second-harmonic generation of femtosecond pulses: observation of phase-mismatch effects.

We observe new effects in frequency doubling of colliding-pulse, mode-locked dye-amplified pulses (300 fsec, 620 nm, up to 1 mJ of energy) due to phase mismatch. If the second-harmonic generation in the nonlinear crystal (30-mm KDP crystal) is phase matched, the output is a square pulse. In contrast, when a phase mismatch is introduced, the generated pulse contains two peaks. We observe that the time profile is affected by depletion and chirp of the fundamental. The experimental results agree well with our numerical calculations.