The hypotensive effects of propofol at different sampling sites in cardiopulmonary bypass model.

Background: Although propofol has been widely used the uncertainties about its pharmacokinetics and pharmacodynamics are still in existence especially on acute infusion model. This study was designed to observe the changes of the arterial and superior vena cava blood concentrations of propofol during cardiopulmonary bypass and to see whichever site is more appropriate for pharmacodynamic studies of propofol.

Methods: Eight patients undergoing cardiopulmonary bypass were infused rapidly with propofol. Samples were collected concurrently from bypass arterial side (Ca) and superior vena cava (Cv) side at 0, 0.5, 1, 1.5, 2, 5, 10, 20, 30, and 40 minutes after infusion and analyzed with high pressure liquid chromatography (HPLC). Arterial blood pressure was also recorded at the same time.

Results: After administration, the concentration at Ca side was significantly higher than that at the corresponding Cv side from 0.5 to 5 min. The concentration at Ca side peaked at 0.5 min, then decreased rapidly and crossed the Cv curve at approximately 10 min. Thereafter Cv side concentration was slightly higher than that of Ca side. The mean arterial blood pressure decreased significantly from 1 to 20 min after injection. The change in Cv side was significantly consistent with the blood pressure change in the distribution phase (r = 0.78, r2 = 0.61 P < 0.001) (0 to 5 min).

Conclusions: There was a significant arteriovenous concentration difference of propofol after a rapid infusion in the cardiopulmonary bypass model. The hypotensive effect of propofol in the distribution phase can be predicted better on Cv side.