The use of dye surrogates to illustrate local anesthetic drug sequestration by lipid emulsion: a visual demonstration of the lipid sink effect.

Background And Objectives: We hypothesized that by substituting a dye surrogate in place of local anesthetic, we could visually demonstrate dye sequestration by lipid emulsion that would be dependent on both dye lipophilicity and the amount of lipid emulsion used.

Methods: We selected 2 lipophilic dyes, acid blue 25 and Victoria blue, with log P values comparable to lidocaine and bupivacaine, respectively. Each dye solution was mixed with combinations of lipid emulsion and water to emulate "lipid rescue" treatment at dye concentrations equivalent to fatal, cardiotoxic, and neurotoxic local anesthetic plasma concentrations.