Anatomical basis for ultrasound-guided regional anaesthesia at the junction of the axilla and the upper arm.

PURPOSE: Ultrasound (US) has emerged in the field of regional anaesthesia in the past few years, as it allows physicians to simultaneously see the needle, the targeted nerves, and the vessels to avoid. Nevertheless, anatomical knowledge is essential for identifying all of the structures seen on the US screen. US also allows an in vivo approach to the variations of nerves and vessels. The aim of this study was to describe the anatomical structures of the axilla through a dissection, an anatomical section and US images performed during daily regional anaesthesia. This work will also discuss the usefulness of US in studying anatomical variations of vasculonervous structures. METHODS: The axillary region of an embalmed adult cadaver was dissected in the department of Anatomy, and anatomical sections of another embalmed and frozen cadaver were also performed. During the same period, fortuitous anatomical variations discovered during daily routine axillary US-guided nerve blocks were recorded in the department of Anaesthesiology. RESULTS: The anatomical dissection and sections allowed correlations to be made and structures to be identified on the US images. The most frequent anatomical variations found were double axillary artery, numerous axillary veins, variant location of the musculocutaneous nerve and posterior location of the brachial plexus in relation to the axillary artery. CONCLUSION: Anatomical knowledge is of major importance for US-guided regional anaesthesia. US scan offers a new approach to anatomical variations of the vasculonervous bundle at the junction of the axilla and the upper arm.

Selective radiosensitization by nitric oxide in tumor cell lines.

The radiosensitizing effect of nitric oxide (NO) on mouse and human tumor cells with different degrees of malignancy was evaluated. Cells pre-treated with the NO donor diethylenetriamine-NO (DETA-NO), were irradiated with gamma rays. Survival curves were obtained by clonogenicity and fitted to the linear-quadratic model. Results demonstrated an association between radiosensitization and degree of malignancy. The more malignant the cell line, the higher the degree of radiosensitization by DETA-NO. In conclusion, the differential radiosensitizing effect of DETA-NO shown here is of great interest for the potential use of NO in radiotherapy, due to an enhanced radiation effect on tumor vs. normal tissue.

Microperoxidase 8 catalysed nitrogen oxides formation from oxidation of N-hydroxyguanidines by hydrogen peroxide.

Nitric oxide (NO) is a potent intra- and intercellular messenger involved in the control of vascular tone, neuronal signalling and host response to infection. In mammals, NO is synthesized by oxidation of l-arginine catalysed by hemeproteins called NO-synthases with intermediate formation of Nomega-hydroxy-l-arginine (NOHA). NOHA and some hydroxyguanidines have been shown to be able to deliver nitrogen oxides including NO in the presence of various oxidative systems. In this study, NOHA and a model compound, N-(4-chlorophenyl)-N'-hydroxyguanidine, were tested for their ability to generate NO in the presence of a haemprotein model, microperoxidase 8 (MP8), and hydrogen peroxide. Nitrite and nitrate production along with selective formation of 4-chlorophenylcyanamide was observed from incubations of N-(4-chlorophenyl)-N'-hydroxyguanidine in the presence of MP8 and hydrogen peroxide. In the case of NOHA, the corresponding cyanamide, Ndelta-cyano-L-ornithine, was too unstable under the conditions used and l-citrulline was the only product identified. A NO-specific conversion of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide to 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl and formation of MP8-Fe-NO complexes were observed by EPR spectroscopy and low-temperature UV/visible spectroscopy, respectively. These results clearly demonstrate the formation of nitrogen oxides including NO from the oxidation of exogenous hydroxyguanidines by hydrogen peroxide in the presence of a minienzyme such as MP8. The importance of the bioactivation of endogenous (NOHA) or exogenous N-hydroxyguanidines by peroxidases of physiological interest remains to be established in vivo.