For elbow surgery, the supraclavicular and infraclavicular brachial plexus blocks are similar on several parameters, including block effectiveness, onset and secondary outcomes.
According to study researcher Brigid Brown, MD, although supraclavicular and infraclavicular blocks are well-described regional anesthesia techniques for elbow surgery, there is still ongoing debate about their variation in speed of onset and need for block supplementation. “We looked at the literature and found there’s a paucity of evidence comparing these two blocks for surgeries of the elbow,” she said. Dr. Brown is a clinical fellow in anesthesia at Western University, in London, Ontario. “A recent meta-analysis compared the two techniques and also expressed that more research is needed” (Anesth Analg 2017;124:636-644).
Dr. Brown and her colleagues prospectively enrolled 150 patients into the single-blind randomized controlled trial. Each patient was scheduled for elective ambulatory elbow surgery, and randomly assigned to receive a supraclavicular or infraclavicular block. Both blocks were administered via a standardized protocol by a specialist anesthesiologist or supervised trainee. “All blocks were performed in our designated block room with monitoring sedation and assistance as required,” Dr. Brown said. “Regardless of block, all patients received 35 mL of 0.5% ropivacaine.”
Procedure time and complications during block insertion were noted; a blinded observer recorded the onset of sensory and motor block as well as postoperative pain scores. All blocks were completed under ultrasound guidance with nerve stimulation for assistance.
Timing Largely the Same
As Dr. Brown reported at the 2017 annual meeting of the Canadian Anesthesiologists’ Society (abstract 281186), the supraclavicular and infraclavicular blocks proved comparable in effectiveness. Indeed, conversion to general anesthetic due to block failure occurred in 4.0% of the infraclavicular patients and 5.3% of the supraclavicular group.
Similarly, supplemental blocks were required in 4.0% of the infraclavicular group and 5.3% of the supraclavicular group. “It was interesting to note that when we looked at rescue blocks, all three blocks in the supraclavicular group were of the ulnar nerve, while they were all different in the infraclavicular group,” she said.
Total sensory block onset was also studied, with supraclavicular blocks (20.6 minutes) working significantly faster than infraclavicular blocks (23.0 minutes). Similarly, the total motor block onset in the supraclavicular group (21.9 minutes) was significantly faster than in the infraclavicular group (24.8 minutes). Onset of motor block was similar for the two approaches, however.
“With respect to procedure time, we found there was no significant difference between the blocks,” Dr. Brown said. “An infraclavicular took an average of 284 seconds, while a supraclavicular block needed 307 seconds.”
An analysis of secondary outcomes showed that paresthesia during block insertion occurred in 17 patients undergoing supraclavicular block, compared with six patients receiving the infraclavicular block. “All other complications during block insertion, as well as postoperative complications, pain scores and overall patient satisfaction, showed no difference between the two groups,” she said.
Session co-moderator Ki Jinn Chin, MD, asked about the occurrence of side effects, such as phrenic nerve palsy and Horner syndrome. “These were not part of our secondary outcome analysis,” Dr. Brown replied. “It would be really nice to know about that, but it was not one of the outcomes on our charts.”
“Side effects are the main argument that I present for why I don’t use supraclavicular blocks,” said Dr. Chin, associate professor of anesthesia at the University of Toronto. “If you inject 35 mL of local anesthetic into the neck, chances are you are going to get phrenic nerve palsy and possibly hypoxemia as well. So for me, the distinction between these two blocks is not just about effectiveness, but also safety and complications as well.”