Supraclavicular block: a review of the methodology of blocking the brachial plexus.

Three methods of blocking the brachial plexus with a supraclavicular approach are presented. The pros and cons of using this technique, as well as its usefulness, are discussed. The four most commonly used drugs for blocks also are examined. A 270% increase in blood flow to the arm is achieved by this block but, with the addition of epinephrine, it can be increased to 430%. The permeability of the anterior scalenus fascia is offered as a possible reason for a significant incidence of phrenic nerve paralysis. A greater success rate is possible if paresthesias of the index, middle and ring fingers can be elicited. A little more than 100 years ago, in 1884, Halsted first anesthetized the brachial plexus using cocaine.' Three years later, Crile disarticulated a shoulder using 0.5% cocaine injected into the brachial plexus under direct vision. But it was not until 1911 that Kulenkampft and Hirschel described percuta-neous injection and Kulenkampft, in association with Persy, first described a classical supraclavicular block of the brachial plexus. 2 Various modifications of the brachial plexus block have come into existence simply because of the anatomy of the plexus itself, which allows intervention at five locations-interscalene, parasca-lene, supraclavicular, infraclavicular and axillary. 1 The brachial plexus is formed by the convergence of the anterior rami of the lower cervical nerves (C5, C6, C7, C8) and the greater part of the anterior division of the first thoracic nerve. The fourth cervical and the second thoracic nerves frequently will send a small branch into the plexus which, together with the subclavian artery, emerges from the neck between the anterior and middle scalenus muscles. These rami form three trunks, which split into anterior and posterior divisions as they pass under the clavicle and over the first rib (Figure 1). These divisions reunite to form cords near the second part of the axillary artery. 8 The function of the brachial plexus is to supply almost all of the motor and sensory functions of the arm. However, the anesthetist must be aware that the skin of the shoulder and the posterior medial aspect of the upper arm is supplied by other nerves. The skin of the shoulder is supplied by the descending branch of the cervical plexus, and the back of the upper arm is innervated by the intercostobrachial nerve, a branch of T-2. The supraclavicular approach causes the plexus to be blocked where it is arranged …