Influence of Receptor Antagonists, Local Anesthetics, and Denervation on Microcirculation

OBJECTIVE Impaired microcirculation is one of the most important factors in delayed wound healing. The aim of the study was to investigate the influence of chemical and surgical interruption of sympathetic nerve fibers and α- and β-receptors blockers on muscular microcirculation. METHODS The experiment was performed on a standardized cremaster muscle model of male Wistar rats (n=51). Microcirculation was recorded via transillumination microscopy on each of the 4 test groups and in a control group before and after their respective treatments with one of the following: topical application of bupivacaine, metoprolol, phentolamine, or surgical denervation. The arteriolar diameter and functional capillary density (FCD) as parameter for tissue perfusion were assessed. RESULTS The α-blocker phentolamine was the only agent that caused a significant dilation of the arteriolar diameter (76.6 ± 6.9 vs 100.0 ± 12.0 µm). However, like bupivacaine, metoprolol, and the surgical sympathectomy, it did not improve FCD as a parameter for tissue perfusion. The strongest vasoconstriction (35.9 ± 4.3 vs 28.6 ± 4.0) and impairment of the FCD (10.0 ± 0.7 vs 4.1 ± 0.9) was induced by the β-blocker metoprolol. CONCLUSIONS This study shows that phentolamine could be an agent for dilating arteriolar diameter, but it did not improve FCD. Whereas the other agents, including sympathectomy, did not alter arteriolar diameter, the β-blocker worsened both investigated parameters. Our results raise the question whether β-blockers negatively influence microcirculation. Therefore, further studies are needed to investigate the potential adverse effects of β-blockers on wound healing.