Impact on Sensitivity and Motor Block Duration of an Intravenous Dexamethasone an Axillary Block With Mepivacaine.

Intravenous dexamethasone is used to increase the duration of analgesia of interscalene bloc for shoulder surgery: it extends from 11h to 23h the sensitivity block in shoulder area. However, the time of dexamethasone intravenous injection has not been studied. In all studies, dexamethasone was injected right after the achievement of loco regional anesthesia. The main objective is to demonstrate that intravenous injection of dexamethasone delayed at 90 minutes in patients who received an axillary block with mepivacaine prolongs the duration of the motor block by 40 minutes.