Supraclavicular nerve block: anatomic analysis of a method to prevent pneumothorax.

Supraclavicular nerve blocks are technically easy to perform, but may be associated with pneumothorax. The objective of this study is to define the parasagittal anatomy important to our modified technique of supraclavicular nerve block designed to decrease the incidence of pneumothorax and to determine whether this technique is anatomically sound. Two cadaver specimens were studied. One embalmed specimen was dissected to establish the relationship of the brachial plexus to our modified needle entry site. The neck and upper thorax of an unembalmed cadaver were frozen, and parasagittal serial sections were made to establish the relationship of the brachial plexus to surface features and the chest cavity. Additionally, 12 volunteers underwent magnetic resonance (MR) imaging and anatomic measurements of their supraclavicular anatomy important to our modified block. MR imaging showed that in no instance using our modified technique was the lung contacted by the simulated needle before entering either the subclavian artery or contacting the brachial plexus. Our technique has been used in more than 110 patients without pneumothorax. The combination of our cadaver and magnetic resonance data suggests that our plumb-bob technique of supraclavicular nerve block is anatomically sound and may minimize the development of pneumothorax during supraclavicular block.