Chapter

Peripheral nerve location techniques

George Corner and Calum Grant

in Principles and Practice of Regional Anaesthesia

Fourth edition

Published on behalf of Oxford University Press

Published in print November 2012 | ISBN: 9780199586691
Published online November 2012 | e-ISBN: 9780191755507 | DOI: http://dx.doi.org/10.1093/med/9780199586691.003.0010

Series: Oxford Textbooks in Anaesthesia

Peripheral nerve location techniques

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Safe and effective peripheral block requires injection of an appropriate dose of local anaesthetic solution close to the target nerve, and the localization techniques described here allow the anaesthetist to position the needle tip correctly, either next to the nerve or in the correct fascial plane. Patient discomfort should be minimized and care taken to avoid trauma to surrounding structures (e.g. blood vessels and pleura) as well as to the nerves themselves. A wide range of methods, from the solely anatomical to the technologically complex, is now available, but it must be stressed that a thorough understanding of the relevant anatomy is fundamental to all of the nerve localization techniques described in this chapter. No technological aid, ultrasound included, is a surrogate for knowledge of both the relevant anatomy and the specific block technique, nor is it an excuse for ignoring the principles of patient selection and management during (and after) block performance. The possible localization techniques are: 1. Anatomical landmarks: surface anatomy is used in conjunction with knowledge of the standard course of the nerve to identify where the local anaesthetic should be injected (e.g. saphenous block below the knee). The correct depth of injection may be further refined using tactile sensation: a ‘pop’ is noted as a short bevel needle penetrates the deep fascia covering the correct myofascial plane (e.g. ilio-inguinal nerve). 2. Elicitation of paraesthesiae: gentle contact of needle tip with nerve will generate paraesthesiae in its distribution. 3. Electrical stimulation: low current stimulation of the motor component of a mixed peripheral nerve will generate a ‘twitch’ in the muscles supplied by it. 4. Ultrasound guidance: the preceding two techniques rely on a knowledge of standard anatomy to identify the initial needle insertion point, but real-time ultrasound scanning allows the relevant nerves (and surrounding structures) to be identified first. Thus individual variation can be allowed for, and (often) both needle position and local anaesthetic spread visualized. 5. Complex imaging: modern radiological techniques have a key role in chronic pain practice (see Chapter 23), but their lack of ‘portability’ means that they are rarely used in anaesthesia. However, developments in operating theatre design and advances in technology may mean that this changes in the future. The main focus of this chapter is on paraesthesiae, electrostimulation, and ultrasound guidance.

Chapter.  9099 words.  Illustrated.

Subjects: Anaesthetics ; Clinical Skills

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