Ultrasound-Guided Infraclavicular Block

To the Editor Although we applaud the continued investigation by Fredrickson et al.1 of a single infraclavicular injection in comparison with the triple-injection technique, we question the validity of their conclusion that both groups have the same success rate when both the triple-injection success rate of 55% and the single-injection rate of 49% are much less than the published results of others (70%–100%), when a successful block is defined as the surgical anesthesia without either complete sensory blockade or the need for supplementation.2–8 We suggest that the low success rates may be the result of inadequate visualization combined with the absence of a true single injection. Fredrickson et al. visualized 3 cords in 12% (6 of 49) of the patients, 2 cords in 65% (32 of 49) of patients, and 1 or no cord in 22% (11 of 49) of patients. In the majority (88%) of their patients, local anesthetic was injected at 1 or more arbitrary points. For the single-injection group, Fredrickson et al. did not attempt visualization of the cords. Instead, they relied on the best image of the second part of the axillary artery and injected posterior to it by moving the needletip in a cephalad–caudad direction. Thus, their “single” injection was manipulated to involve up to 50% circumference of the artery. However, a periarterial injection technique is a significant limitation because there is variability in the arrangement of the cords and septa can influence the spread of local anesthetic.9,10 In our experience, all 3 cords are visualized in greater than 99% of infraclavicular blocks.2–4 Thus the finding that single-injection technique was not significantly inferior to the triple-injection technique reflects that both groups had unacceptably low success rates secondary to inadequate visualization of the cords and lack of a true single injection. In conclusion, although we believe that the multiple-injection technique is preferable, the question of whether a single-injection technique guided by ultrasound after locating the cords can achieve comparable efficacy and efficiency to a multiple-injection technique remains open. Anthony Machi, MD Joseph Soo, MD Preetham Suresh, MD Ching-Rong Cheng, MD Michael L. Bishop, MD Vanessa Loland, MD Navparkash S. Sandhu, MD, MS Department of Anesthesiology University of California, San Diego La Jolla, California [email protected]