Binding of local anaesthetics to the lipid emulsion Clinoleic™ 20%

Lipid emulsions have been used to treat cardiovascular collapse due to local anaesthetic toxicity. However, there are few data available on the comparative efficiency of the partitioning properties of available lipid emulsions in clinical use. This in vitro study compared the buffering properties of the lipid emulsions Clinoleic (TM) 20% (Baxter, Old Toongabbie, NSW) and Intralipid (R) 20% (Fresenius Kabi, Pymble, NSW) using both bupivacaine (Marcain (R) 0.5%, AstraZeneca, North Ryde, NSW) and ropivacaine (Naropin (R) 1%, AstraZeneca, North Ryde, NSW). The concentration of anaesthetic in buffer before and after mixing with lipid was quantified using chromatographic analysis. Bupivacaine was more effectively bound by the lipid agents, with a 40% reduction in initial concentration. Ropivacaine demonstrated a 20% reduction in concentration with the addition of lipid agents. Importantly, there was no significant difference between Intralipid and Clinoleic in terms of their buffering behaviour, suggesting equivalent binding efficacy