Infraclavicular Block Attenuates Tourniquet-Induced Ischemia-Reperfusion Injury and Preserves Endothelial Function...

Background: Tourniquet application during upper extremity surgery induces ischemia-reperfusion (IR) injury, generating oxidative stress and impairing endothelial function. Whether infraclavicular block (IB) or general anesthesia (GA) differentially modulates these responses remains uncertain. Methods: In this prospective randomized controlled trial, 124 patients were assessed for eligibility; 112 were randomized to IB (n = 60) or GA (n = 52). Following per-protocol exclusions (9 from IB, 3 from GA), 100 patients were analyzed (IB n= 51, GA n = 49). The primary outcome was change in brachial artery flow-mediated dilatation (FMD) from baseline at 24 h (FMD2) and 6 days (FMD3) postoperatively. Secondary outcomes included serum malondialdehyde (MDA), protein carbonyl (PC), total nitric oxide (NO), and xanthine oxidase (XO) measured at four perioperative time points (T0-T3). Analysis of covariance (ANCOVA) with baseline values as covariates was the primary analytical approach. Results: Baseline FMD was comparable between groups (IB: 6.33% vs. GA: 6.11%, p = 0.478). Both groups exhibited significant postoperative FMD reduction compared with the baseline; however, the magnitude of this decline was significantly smaller in the IB group than in the GA group at 24 h (ΔFMD: -1.44% vs. -1.69%, p = 0.004) and at 6 days (ΔFMD: -0.77% vs. -1.01%, p = 0.003). ANCOVA confirmed a significant independent group effect for FMD at both time points (FMD2: F = 13.95, p = 0.0003, η²p = 0.126; FMD3: F = 16.45, p = 0.0001, η²p = 0.145). Regarding oxidative stress biomarkers, baseline differences were observed in MDA and PC between groups. Following ANCOVA adjustment, no consistent group effect was identified for MDA or PC. Isolated significant group effects were noted for NO at T3 (p = 0.004) and XO at T1 (p = 0.036), but these were not sustained across time points and are considered exploratory. A sensitivity intention-to-treat analysis including all randomized patients yielded directionally consistent FMD findings, supporting the robustness of the primary results. Conclusions: Infraclavicular block significantly attenuated the postoperative decline in endothelial function compared with general anesthesia following tourniquet-induced IR injury, as reflected by ANCOVA-adjusted FMD outcomes with large effect sizes. The effect on oxidative stress biomarkers was inconsistent after baseline adjustment and should be considered hypothesis-generating. These findings suggest that regional anesthesia may offer endothelioprotective benefits in upper extremity surgery; however, the absence of consistent oxidative stress biomarker effects after baseline adjustment precludes conclusions regarding broader attenuation of ischemia-reperfusion injury. Confirmation in future adequately powered studies is warranted.