Comparison of Costoclavicular Block and Infraclavicular Block Effects on Tissue Oxygen Saturation in Upper Extremity Surgery: A Randomized, Assessor-Blinded Controlled Trial

Background/Objectives: Ultrasound-guided brachial plexus blocks are widely used in upper extremity surgery. The costoclavicular block (CCB) has been defined in recent years as an alternative to the infraclavicular block (ICB) and attracts attention due to its anatomical advantages. However, studies comparing these two techniques using objective physiological parameters are limited. This study aimed to compare the effectiveness of CCB and ICB techniques by measuring tissue oxygenation with near-infrared spectroscopy (NIRS) and evaluating the role of NIRS in demonstrating block success. Methods: Eighty patients undergoing upper extremity surgery were included in this prospective, randomized, comparative study, and the patients were randomly divided into two groups: CCB (n = 40) and ICB (n = 40). Block success was evaluated using tissue oxygen saturation (StO2) and its change (ΔStO2) measured by NIRS in addition to sensory and motor assessments. In addition, hemodynamic parameters were recorded. Results: A statistically significant increase in StO2 and ΔStO2 values was observed after block application in both groups. In the costoclavicular block group, the median StO2 increased from 78.5 [8.5] at baseline to 86.5 [9.75] at 20 min (p < 0.001), while in the infraclavicular block group, it increased from 75.0 [12.0] to 85.0 [9.0] (p < 0.001). Similarly, the ΔStO2 values increased from 0.0 [0.0] to 9.5 [8.25] in the costoclavicular group and from 0.0 [0.0] to 11.0 [9.0] in the infraclavicular group (both p < 0.001). This increase began in the early period and paralleled sensory-motor block findings, indicating that NIRS measurements objectively reflect block success. An isolated intergroup difference in StO2 was observed at t10 (83.92 ± 6.17 vs. 80.33 ± 7.31, p = 0.023), but no consistent intergroup superiority was demonstrated across the follow-up period. No statistically significant intergroup differences were found for ΔStO2 at any time point (p > 0.05). The block success rates were similar between groups. The hemodynamic parameters remained stable in both groups, and no clinically significant adverse events were observed. Conclusions: CCB and ICB techniques have similar efficacy and safety profiles in upper extremity surgery. NIRS-derived StO2 and ΔStO2 changes appear to be promising complementary physiological markers associated with block onset. However, the present study was not designed to establish diagnostic cut-off values or predictive accuracy; therefore, NIRS should be interpreted as an adjunct to, rather than a replacement for, conventional sensory and motor block assessment.