Abstract:Objective To investigate the application of ultrasound-guided costoclavicular space brachial plexus block (BPB) in anesthesia for patients undergoing upper limb fracture surgery, and to study its effects on block efficacy, immune function, and postoperative pain. Methods Eighty patients undergoing upper limb fracture surgery at Anqing First People ‘ s Hospital Affiliated to Anhui Medical University from May 2021 to October 2024 were selected and randomly divided into a control group (n=40) and an experimental group (n=40). Both groups received ultrasound- guided BPB and open reduction internal fixation surgery. The control group adopted the coracoid approach, while the experimental group adopted the costoclavicular space approach. The anesthetic block efficacy, brachial plexus block status at 5, 10, 20, and 30 minutes after drug injection respectively, Visual Analog Scale (VAS) score at rest and during movement at 12, 18, 24, and 36 hours postoperatively, immune function markers (CD3+, CD4+, CD8+) before and after surgery, and perioperative side effects were compared between the two groups. Results Compared with the control group, the experimental group had shorter block operation time [ (6.14±1.35) min vs (7.94±1.17) min, t=6.373, P<0.01], longer block maintenance time [ (434.51±20.31) min vs (412.47±19.63) min, t=4.935, P<0.01], and shallower needle insertion depth [ (2.58±0.22) min vs (3.36±0.27) min, t=14.164, P<0.01]. Compared with the control group, the experimental group showed higher sensory block rates of the musculocutaneous, ulnar, radial, and median nerves at 5 and 10 minutes after durg injection (P<0.05), and higher motor block rates of the musculocutaneous, radial, and ulnar nerves at 10 minutes ofter injection (P<0.05). The inter-group effect, time effect, and interaction effects of VAS scores at rest and during movement at 12, 18, 24, and 36 hours postoperatively were statistically significant in both groups (P<0.05). Postoperatively, immune function levels decreased in both groups, and the control group had lower levels of CD3+, CD4+, CD8+ compared to the experimental group (t=4.762, 7.106, 2.152, P<0.05). There was no statistically significant difference in the incidence of perioperative side effects between the two groups [10.00% (4/40) vs 15.00% (6/40), χ²=0.457, P=0.499]. Conclusion Ultrasound-guided costoclavicular space BPB demonstrates significant block efficacy in patients undergoing upper limb fracture surgery, with rapid onset of sensory and motor blockade, lower postoperative pain levels, reduced impact on immune function, and good safety.