Chapter

Spinal anaesthesia

Jonathan Whiteside and Tony Wildsmith

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/9780199586691.003.0013

Series: Oxford Textbooks in Anaesthesia

Spinal anaesthesia

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Spinal anaesthesia is induced by the injection of local anaesthetic into the subarachnoid space, and is generally regarded as one of the most reliable of regional block methods. It has the particular advantage that very small doses of local anaesthetic produce profound effects so that systemic toxicity is not a problem. However, other drugs, such as opioids, co-administered by the same route to produce more prolonged pain control may have systemic effects. The second major advantage is that needle insertion is relatively straightforward with cerebrospinal fluid (CSF) providing both a clear indication of successful needle placement and a medium through which local anaesthetic solution usually spreads readily. The popularity of the technique has waxed and waned since its introduction by August Bier in 1898. Widespread use in the 1930s and 1940s was followed by a sharp decline in the 1950s, coinciding with improvements in general anaesthetic techniques (notably the introduction of the neuromuscular blocking drugs) and the adverse publicity regarding neurological sequelae in the Woolley and Roe case (Cope 1954, Hutter 1990). However, the technique has regained a significant place in anaesthetic practice over the last four decades, having been used in all age groups from premature neonates to the most elderly, and in a wide range of clinical situations. Lumbar puncture is usually performed below the termination of the spinal cord, which is at or about L1 in the adult, the subarachnoid space ending at the level of the second sacral vertebra (Chapter 12). The tough dura mater and flimsy arachnoid are closely applied to each other, but there remains a potential (subdural) space between them. If the whole bevel of the spinal needle is not within the subarachnoid space, some of the solution may be deposited within the subdural space and this can account for some failures (Fettes et al. 2009). The posterior subarachnoid space contains several membranous structures (see Figure 12.7) and, in the lumbar region particularly, the septicum posticum may be well developed. These structures can lead to maldistribution of solutions, and account not only for failure to achieve adequate block, but also for neurotoxicity and the development of the cauda equina syndrome (CES). The site of action is primarily the nerve roots, but the dorsal root ganglia and the superficial parts of the cord may be affected also (Greene & Brull 1993). Differential effects may result in wide differences in the rostral levels of different types of block: up to seven segments between sympathetic and sensory block (Chamberlain & Chamberlain 1986), and 2.5 segments between sensory and motor block (Freund et al. 1967).

Chapter.  10892 words.  Illustrated.

Subjects: Anaesthetics ; Clinical Skills ; Anatomy

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