PHARMACOKINETICS OF LIDOCAINE AND BUPIVAC AINE WITH HYALURONIDASE AFTER PERIBULBAR BLOCK

Objective: To assess the time course of plasma concentrations of lidoc aine and bupivacaine associated with hyaluronidase for peribulbar bloc k. Study design: Prospective study. Patients: Ten patients (mean age = 71 +/- 11 yrs, mean weight 63 +/- 10 kg) scheduled for cataract surge ry with lens implantation. Method: Lidocaine 2 % (5.5 mL = 110 mg) and bupivacaine 0.5 % (5.5 mL = 27.5 mg) associated with hyaluronidase (8 0 IU) were injected supra and infra-orbitally, in patients premedicate d with midazolam. Blood samples were collected at constant time interv als from the end of infiltration until the 6th hour. The plasma concen trations of local anaesthetics were measured with the HPLC technique. Results: The median plasma peak concentration was 1.74 mg . L(-1) afte r 10 min for lidocaine, and 0.52 mg . L(-1) after 7.5 min for bupivaca ine respectively. Conclusions: The similar delays of occurrence of pea k concentrations confirm that liposolubility is not the only factor of diffusion of local anaesthetics from the periocular fat into the bloo d stream. The peak concentrations are far below the alleged toxic conc entrations. When associated with hyaluronidase, the peak concentration s occur as rapidly as after endotracheal or paracervical administratio n.