Finite element simulation of nonlinear wave propagation in thermoviscous fluids including dissipation.

A recently developed finite element method (FEM) for the numerical simulation of nonlinear sound wave propagation in thermoviscous fluids is presented. Based on the nonlinear wave equation as derived by Kuznetsov, typical effects associated with nonlinear acoustics, such as generation of higher harmonics and dissipation resulting from the propagation of a finite amplitude wave through a thermoviscous medium, are covered. An efficient time-stepping algorithm based on a modification of the standard Newmark method is used for solving the non-linear semidiscrete equation system. The method is verified by comparison with the well-known Fubini and Fay solutions for plane wave problems, where good agreement is found. As a practical application, a high intensity focused ultrasound (HIFU) source is considered. Impedance simulations of the piezoelectric transducer and the complete HIFU source loaded with air and water are performed and compared with measured data. Measurements of radiated low and high amplitude pressure pulses are compared with corresponding simulation results. The obtained good agreement demonstrates validity and applicability of the nonlinear FEM.

[Pneumothorax in vertical infraclavicular block of the brachial plexus. Review of a rare complication]. / Pneumothorax bei der Vertikalen Infraklavikulären Blockade des Plexus brachialis. Fallbericht einer seltenen Komplikation.

A 50 year old female patient received anaesthesia of the arm by the vertical infraclavicular blockade of the plexus brachialis (VIP). Postoperatively an ipsilateral pneumothorax occurred complicated by pleural effusion and a contralateral bronchopneumonia, which resolved completely after treatment. The blockade of the plexus was performed correctly, failures in determining the correct point of needle insertion could be excluded. Therefore a pneumothorax has to be regarded as a specific complication of the VIP, which might occur despite correct technique, and requires that the patient be informed of this eventuality. Nevertheless, the VIP is an important method due to its high success rate concerning blockade of the musculocutaneous nerve and tolerance of tourniquet. The risk of a pneumothorax is about 0.2 to 0.7%.

[Vertical infraclavicular brachial-plexus blockade. A clinical study of reliability of a new method for plexus anesthesia of the upper extremity]. / Vertikale infraklavikuläre Plexus-brachialis-Blockade. Klinische Studie zur Anwendbarkeit einer neuen Methode der Plexusanästhesie der oberen Extremität.

We examined the efficacy of the vertical infraclavicular block for plexus brachialis anaesthesia using a nerve stimulator after introducing the method (VIP1) and after three years of clinical experience (VIP2). In two prospective studies we compared the results with each other as well as with the efficacy of the axillary block (AX). At VIP1, we found a complete analgesia in 88% of the patients, whereas in 9% a supplementation was needed. In group AX the results were significantly worse (complete: 70%, supplementation: 24%; p < 0.001). No increase of the rate of efficacy could be found when having some clinical experience with the VIP (VIP2: complete 87%, supplement: 11%). In general, the results of the VIP depended on the motoric answer to the nerve stimulation. There were no complications of the VIP such as nerve lesions or pneumothorax. The VIP using a nerve stimulator is a simple, reliable and uncomplicated method for plexus-brachialis-anaesthesia, which is easy to learn.

Acral persistent papular mucinosis.

Acral persistent papular mucinosis has recently been proposed as a distinct form of cutaneous mucinosis. We describe a patient and review the literature. We conclude that acral persistent papular mucinosis is a distinct clinical entity, clearly separable from most other forms of cutaneous mucinosis except for one variant of lichen myxedematosus, from which it is less easily distinguished.