[Pharmacokinetics of lidocaine and bupivacaine after peribulbar block with additional hyaluronidase].

OBJECTIVE

To assess the time course of plasma concentrations of lidocaine and bupivacaine associated with hyaluronidase for peribulbar block.

STUDY DESIGN

Prospective study.

PATIENTS

Ten patients (mean age = 71 +/- 11 yrs, mean weight 63 +/- 10 kg) scheduled for cataract surgery with lens implantation.

METHOD

Lidocaine 2% (5.5 mL = 110 mg) and bupivacaine 0.5% (5.5 mL = 27.5 mg) associated with hyaluronidase (80 IU) were injected supra and infra-orbitally, in patients premedicated with midazolam. Blood samples wer0 collected at constant time intervals from the end of infiltration until the 6th hour. The plasma concentrations of local anesthetics were measured with the HPLC technique.

RESULTS

The median plasma peak concentration was 1.74 mg.L-1 after 10 min for lidocaine, and 0.52 mg.L-1 after 7.5 min for bupivacaine respectively.

CONCLUSIONS

The similar delays of occurrence of peak concentrations confirm that liposolubility is not the only factor of diffusion of local anaesthetics from the periocular fat into the blood stream. The peak concentrations are far below the alleged toxic concentrations. When associated with hyaluronidase, the peak concentrations occur as rapidly as after endotracheal or paracervical administration.