An In Vitro Analysis of the Effects of Intravenous Lipid Emulsion on Free and Total Local Anaesthetic Concentrations in Human Blood and Plasma

Figure 3

Comparison of the reduction in (a) total drug concentration of LAs in human plasma and (b) free drug concentration of LAs in whole human blood with the lipophilic index of each drug with linear regression lines included when all four local anaesthetics are displayed. With the removal of ropivacaine data, a linear correlation using linear regression analysis was observed between reduction of local anaesthetic concentration and for total drug concentration (c) and free drug concentration (d). There was no linear relationship between increasing and greater binding to lipid emulsion by the local anaesthetics. Bupivacaine showed the greatest reduction in total and free drug concentrations and has the highest lipophilic index. Ropivacaine showed unexpectedly low reductions of drug concentrations with ILE treatment despite having the second highest lipophilic index.

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