Levobupivacaine hydrochloride and sufentanil have no antimicrobial effect at 25°C in vitro

Background and objectives: Levobupivacaine in combination with sufentanil may be used for labour or postoperative regional analgesia. The risk of bacterial growth within these contained solutions for several hours at room temperature is unknown. We investigated the in vitro antimicrobial effect of levobupivacaine and sufentanil against common micro-organisms encountered during regional anaesthesia. Methods: Standardized suspensions of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli were incubated for 1, 3, 6 and 24h at 25 degrees C, with saline (as control), sufentanil 0.5 or 0.75 mu g mL(-1), levobupivacaine hydrochloride 5.6 mg mL(-1) and concentrations of 1.4, 2.8 and 5 mg mL(-1) of levobupivacaine hydrochloride with sufentanil 0. 5 mu g mL(-1) Colony counts were compared after 24 h incubation at 37 degrees C. Results: No bacterial growth was observed on any bacterial strain for any solution tested throughout the experiment. Conclusions: Our results suggest that solutions of levobupivacaine combined with sufentanil may be used for 24 h at room temperature during regional anaesthesia with no risk of bacterial growth.