Local anesthetic drugs reduce endothelium-dependent relaxations of porcine ciliary arteries.

PURPOSE: During retrobulbar anesthesia ocular hemodynamics are altered. The purpose of this study is to investigate the effects of local anesthetics in isolated porcine ciliary arteries (diameter between 200 and 400 microns).

METHODS

Isolated porcine ciliary arteries were suspended in myograph systems filled with modified Krebs-Ringer solution for isometric tension recording.

RESULTS

In quiescent or serotonin-precontracted arteries, lidocaine, bupivacaine, or mepivacaine (10(-9)-10(-5)M) evoked no change in vascular tone. However, all local anesthetics (10(-5)M) and bupivacaine (10(-5)-10(-6)M) reduced endothelium-dependent relaxations to bradykinin (10(-9)-10(-6)M), whereas the endothelium-independent relaxations to the nitric oxide-donor 3-morpholino-sydnonimine (SIN-1; 10(-9)-10(-5)M) were unaffected by local anesthetics. The addition of L-arginine (10(-4)M) markedly reduced the inhibitory effects of bupivacaine on endothelial vasodilatation function.

CONCLUSION

These findings demonstrate that in porcine ciliary arteries, local anesthetics impair endothelial formation of nitric oxide from L-arginine after stimulation with bradykinin, which may contribute importantly to the reduction in blood flow to the eye during retrobulbar anesthesia.