Abstract:
Supraclavicular block of the brachial plexus was long regarded as the quintessential skill of the regional
anaesthetist: it was quick to perform, and effective at providing sensory and motor block of the arm, but
significant skill was required to manage the risk of pneumothorax. Indeed, for this reason, it was often
avoided by many practitioners for fear of both clinical and medicolegal consequences. More recently,
there has been a resurgence of interest in supraclavicular block: the introduction of ultrasound, with its
ability to visualize structures, in particular, improves the safety profile of the technique. This thesis
undertakes a comprehensive reappraisal of the applied anatomy of the supraclavicular area, and
evaluates how this knowledge might affect the complication/side effect profile of supraclavicular block.
Initially, the aim was restricted to trying to lessen the risk of pneumothorax by using the mathematical
principle of the tangent, with the anatomy of the area requiring a bend in the block needle, but the
project evolved into the more comprehensive task of also trying to alter the risk of blocking the phrenic
nerve, sympathetic chain, and recurrent laryngeal nerve. As secondary goals, the thesis aims to better
place the technique in terms of its clinical utility, and examines how detailed knowledge of the anatomy
can usefully be dovetailed with the emergent ultrasound technology. A number of anatomic and clinical
studies were performed. These included examining the relationships between the clavicle, brachial
plexus and chest wall, studying the block’s clinical profile, investigating the incidence of phrenic nerve
block and studying the mechanism for its avoidance, and reevaluating the anatomic structures which
surround the brachial plexus and influence flow and spread of injected solution. The results have added
to the knowledge base of applied anatomy: in particular, they afford new insights into the role of the
first rib, clavicle, and scapula. They have also challenged one of the traditional cornerstones of brachial
plexus regional anaesthesia, the ‘sheath’. The study technique evolved to incorporate the modern
technology, becoming ultrasound-guided axillary tunnel block. The clinical versatility of this technique
and its ability to avoid the phrenic nerve are clear advantages. Together, these observations enhance our understanding of the anatomic dynamics involved in brachial plexus blockade, and the thesis presents a
new model based on the rigid anatomy surrounding the plexus.