Background: Mechanism of remote ischemic conditioning (RIC) remain not fully understood yet. Thus, a clinical trial was performed to assess the neuronal influence on its signal induction.
Methods: RIC was conducted on 45 patients who were randomized into 3 groups. Group A and B underwent brachial plexus anesthesia while RIC was performed on the blocked (A) and non-blocked side (B), respectively. In group C, RIC was conducted before regional anesthesia, thus serving as control group. All measurements were taken contralateral to RIC. The relative increase of microcirculatory parameters compared to baseline was evaluated and compared between the groups.
Results: Superficial blood flow (sBF) significantly increased in group A and C but values were higher among group C. Compared to group A, group C showed a significant increase of sBF during the initial 5 minutes of reperfusion (1.75; CI 1.139 - 2.361 vs. 0.97, CI 0.864 - 1.076, p < 0.05). Deep blood flow, tissue oxygen saturation and relative hemoglobin content were marginally influenced by RIC irrespectively of the presence of regional anesthesia.
Conclusion: Despite regional anesthesia a significant RIC stimulus can be induced although its microcirculatory response is attenuated compared to control. Hence, RIC induction does not merely depend on neuronal signaling.
Keywords: Remote ischemic conditioning; microsurgery; neuronal signaling; plexus anesthesia; reperfusion.