Local anesthetic actions on thromboxane-induced platelet aggregation

Some local anesthetics (LA), in concentrations present in blood during IV o r epidural infusion, inhibit thrombus formation in the postoperative period . Studies on thromboxane A(2) (TXA(2)) signaling in a recombinant model sug gest that interference with TXA(2)-induced platelet aggregation may explain , in part, the antithrombotic actions of epidural analgesia and IV LA infus ion. In this study we investigated. the effects of clinically used LAs (lid ocaine, ropivacaine, and bupivacaine) on TXA(2)-induced early platelet aggr egation (1-5 s) by using quenched-flow and optical aggregometry. Our findin gs demonstrate that the LAs tested seem to have only a limited ability to i nhibit TXA(2)- induced platelet aggregation assessed at early times (1-5 s) . Therefore, the clinical effects of LAs on thrombi formation are unlikely to be explained by this manner alone. At large LA concentrations, moderate effects were obtained. Prolonged incubation with LA did not significantly i ncrease effectiveness, and the lack of an effect could not be explained by generation of secondary mediators. The results were independent of the anes thetic studied. Local anesthetic effects on TXA(2)-induced early platelet a ggregation (1-5 s) are unlikely to play a major role in the clinically obse rved antithrombotic effects of local anesthetics.