Computed tomographic study of parascalene block.

Parascalene block is a technique of blocking the brachial plexus at the lateral border of the anterior scalene muscle superior to the clavicle. The objective of this study was to define the position of the needle in parascalene block with relationship to the brachial plexus and the dome of the pleura, which is important in determining whether this technique minimizes the incidence of pneumothorax. In the first group, 10 patients scheduled for minor upper extremity surgery agreed to parascalene block, which was performed in the computed tomographic examination room. In the second group, 10 volunteers agreed to have markers placed at the point where a needle would be inserted for parascalene block. The computed tomographic study at the level of the needle insertion or the marker revealed that this level was superior to the dome of the pleura. The distances from the skin to the interscalene groove and the interscalene groove to the first rib at the level of the needle insertion or the marker in both groups were measured to be 17 +/- 4 mm and 15 +/- 3 mm, respectively. This study suggests that the level of the parascalene needle entry is superior to the dome of the pleura. At this level, the incidence of pneumothorax should be minimized.