The Significance of Lipoproteins in Serum Binding Variations of Propofol

The protein binding of propofol was investigated in vitro in isolated lipoprotein fractions (very low-density lipoprotein [VLDL], low-density lipoprotein [LDL], and high-density lipoprotein [HDL]) and in serum samples from the following subjects: healthy normolipemic volunteers (n = 16), hyperlipidemic subjects diagnosed with familiar polygenic hypercholesterolemia (n = 26) showing high levels of cholesterol, and elderly subjects (n = 15). Protein binding was determined by using ultrafiltration, and the concentration of unbound propofol was measured by using liquid chromatography. Levels of total cholesterol, triglycerides, VLDL cholesterol, LDL cholesterol, HDL cholesterol, albumin, and alpha1-acid glycoprotein were also measured. Propofol was extensively bound to the three lipoprotein fractions (88% +/- 2% to VLDL, 93% +/- 1% to LDL, and 91% +/- 4% to HDL). The percentage of unbound propofol was significantly decreased (P < 0.0001) in hyperlipidemic (0.88% +/- 0.20%) individuals whose levels of cholesterol and triglycerides were increased versus healthy subjects (1.26% +/- 0.22%), whereas no significant difference was found in the elderly group (1.12% +/- 0.23%). A positive relationship was found between serum protein binding of propofol and lipid levels. Multiple regression analysis, including all subjects, showed that changes in the levels of total cholesterol and triglycerides explained approximately 62% of the variability in the serum protein binding of propofol. These results stress the importance of triglycerides and cholesterol in the serum protein binding of propofol. We therefore suggest that these variations in lipid levels, and consequently in protein binding, may influence anesthetic practice with propofol. Implications: We investigated the effect of serum lipids in the protein binding of propofol. We found that propofol binds extensively to all lipoprotein fractions. Propofol binding showed a significant relationship with the serum levels of cholesterol and triglycerides. (Anesth Analg 1998;87:1147-51)