Background: The purpose of the study was to examine the previously reported finding that the addition of bicarbonate to lignocaine enhanced the antimicrobial effect of the local anaesthetic agent on a range of bacteria implicated in epidural infections and to determine if this would also hold true for bupivacaine.

Methods: Bupivacaine at a concentration of 0.25% and lignocaine at a concentration of 1% with and without an alkaline buffer was inoculated with suspensions of Staphylococcus epidermidis, Staphylococcus aureus or Escherichia coli. The mixtures were plated on 2% blood agar plates immediately and after 24 hours at room temperature, and numbers of colonies were recorded.

The difference in the number of colonies between T=0 and T=24 was expressed as a fraction of the T=0 value, giving a percentage inhibition of colony growth. Statistical testing was performed using Kruskal-Wallis non-parametric ANOVA followed by multiple comparisons of mean ranks between all groups.

Results: At concentrations of 0.25% bupivacaine and 1% lignocaine, these findings suggest that 1% lignocaine has no antibacterial activity. The addition of bicarbonate has no influence.

Conclusions: Bupivacaine has significant antibacterial activity, but the addition of bicarbonate has no influence.