Pharmacokinetic Analysis of Bupivacaine in the Presence and Absence of Perineural Dexamethasone in Axillary Blockade

The investigators will conduct a prospective, randomized, double-blinded study using an axillary brachial plexus block in patients undergoing elective surgery of the distal forearm and hand to characterize and describe the pharmacokinetics of bupivacaine associated with perineural dexamethasone. The pharmacokinetic analysis will be performed by measuring bupivacaine plasma levels at different time intervals after the blockade (15, 30, 45, 60, and 90 minutes), allowing comparison between 2 different groups: Bupivacaine (B) and Bupivacaine-dexamethasone (BD). Thus, the hypothesis is that plasma levels of bupivacaine during the first 90 minutes after a blockade are lower in the presence of perineural dexamethasone, suggesting a decrease, at least initially, in systemic absorption from the injection site.