Pharmacokinetics of bupivacaine after axillary brachial plexus block

Severe cardiovascular complications have been associated with regional anesthesia using bupivacaine. Furthermore, in our practice, axillary brachial plexus block is commonly used for surgical emergencies of the hand in out-patients. The pharmacokinetics parameters: peak height (Cmax), peak time (tmax), half life of plasma elimination (t1/2), total apparent clearance (Cl), mean time of plasma retention (t) were studied in 20 male and female patients (mean age 35 and 32 years) receiving axillary local anesthesia by bupivacaine (BU) only (A group = 100 mg), B group BU = 200 mg, or BU + lidocaine (LI) (C group = BU 100 mg + LI 200 mg), plasmatic BU and LI were simultaneously measured by HPLC method. There were no significant differences in the pharmacokinetic data observed in groups A, B and C; total apparent clearances and half times of plasma elimination of BU after brachial plexus block are similar compared to those observed after i.v. administration. Absorption of BU seems to be total while the value of Cmax are very low compared to usual neurotoxic plasma levels, but near that of plasma concentrations observed in cardiac complications. All the tmax observed were under 2 h and the dose independence of the kinetic of BU is not admissible in this study. The association of LI induce no modification of the kinetic of BU. This work concludes that in this way of administration, the absorption of BU seems to be total. Pharmacokinetics of BU is dose dependent and the association of LI induces no significant modification of BU kinetics.