A comparison of two techniques for ultrasound guided infraclavicular block

Background. There is some debate about the proper site and arm position and the direction of the needle for the performance of ultrasound guided infraclavicular block. Methods. Using ultrasound, we compared the ease and success rate of a medial or a lateral approach to the brachial plexus for performing infraclavicular block in two groups of patients (n=202). The proximity of the needle to the lung in each group was also measured with and without the arm abducted from the side. Results. The medial approach was quicker to perform compared with the lateral approach (9 min vs 13 min). The medial approach also had a faster onset. On average, the three cords were more readily imaged with the medial technique (92%) compared with the lateral technique (82%) and the medial technique prevented tourniquet pain more reliably (97%) vs the lateral technique (83%). In the medial technique, the plexus was also closer to the skin (3.7 cm) compared with the lateral technique (4.5 cm). The lateral approach more frequently avoided the chest wall (49%) compared with the medial technique (35%) but resulted in more frequent vascular puncture. Both approaches provided good anesthesia at the surgical site. Abducting the arm 110 degrees and externally rotating the shoulder moves the plexus away from the thorax and closer to the surface of the skin. Conclusion. For infraclavicular block using ultrasound guidance the medial approach is faster and easier to perform, has lower incidence of tourniquet pain and vascular puncture, and brings the plexus closer to the skin. We recommend abducting the arm 110 degrees to minimize the risk of pneumothorax. Externally rotating the shoulder also brings the plexus closer to the skin.