The efficacy and safety of 0.75% levobupivacaine vs 0.75% bupivacaine for peribulbar anaesthesia

Levobupivacaine, the S(-)-enantiomer of racemic bupivacaine, is associated with a similar efficacy but a reduced potential for cardiovascular and central nervous system toxicity than racemic bupivacaine. Thus, this prospective, randomised, double-masked study was undertaken to assess the efficacy and safety of 0.75% levobupivacaine vs 0.75% bupivacaine, each with hyaluronidase, for peribulbar anaesthesia.

A total of 60 patients undergoing elective anterior segment surgery were randomly allocated to receive either agent by a single, inferotemporal peribulbar injection technique, supplemented with a medial canthus injection if necessary. Ocular akinesia and orbicularis oculi function were assessed by scoring systems at 2 min intervals until satisfactory akinesia was achieved, and movements were reassessed on the day after surgery to confirm regression of the block.

The time taken to reach a state of satisfactory anaesthesia and akinesia was deemed to be the primary measure of efficacy. Both agents achieved this in a similar median time of 2 min after receiving 5 ml of the injectate, and the treatment difference was not statistically significant (P=0.24). Blood samples from the first 20 patients were taken at intervals up to 4 h. These were analysed for plasma levels and confirmed similar plasma concentration vs time profiles for the two agents. Seven patients in each group (23%) complained of pain on injection but the technique was generally well tolerated. Two patients in the levobupivacaine group experienced serious adverse events, but neither was considered related to the study medication. The most common minor post-operative adverse event was prolongation of the local anaesthetic block, which was reported by nine patients (four in the levobupivacaine group and five in the bupivacaine group).

Levobupivacaine and bupivacaine are equally successful in achieving clinically satisfactory peribulbar anaesthesia with few adverse effects.