MONDAY, July 27, 2026 (HealthDay News) -- Multimodal pain testing data reveal no post-axillary brachial plexus block hypersensitivity in healthy controls, according to a study published in the August issue of Anesthesiology.
Yun-Yun Chen, M.D., from the Brigham and Women's Hospital in Boston, and colleagues examined nociceptive processing after a single-injection axillary brachial plexus block in healthy volunteers to detect whether a previously blocked arm displayed objective hypersensitivity in the absence of surgical pain. Forty healthy adult volunteers received a single-injection axillary brachial plexus block, with their contralateral unblocked arm serving as a control. Pain sensitivity was compared between the arms using a range of quantitative sensory testing, comparing punctate, pressure, and heat pain. The primary outcome was a heat pain threshold to 1 of 10 pain compared at 60 minutes after motor resolution (MR).
The researchers found that a heat pain threshold to 1 of 10 pain was not significantly different between the arms at 60 minutes after MR (block, 40.8 ± 2.2 degrees Celsius; control, 41.2 ± 2.6 degrees Celsius; P = 0.160). In the block versus the control arm, only a slightly lower temperature was needed to reach 5 of 10 heat pain on testing of several other sensory modalities. The control arm showed greater sensitivity in some tested modalities (punctate pain threshold and painful after sensations) but not others (heat and pressure pain thresholds and tolerances, temporal summation of pain) when examining the maximally sensitized values, including three hours after MR.
"Our study provides reassurance that nerve blocks are safe and effective for pain control after surgery," Chen said in a statement.
