The Cerebral Uptake Of Propofol Following Administration At A Constant Infusion Rate

The cerebral uptake of propofol following administration at a constant infusion rate Objects: The pharmacological effects of propofol have been investigated deeply in recent years, but it is not clear about details of brain uptake and mechanism in the target organ-brain. Whereas the cerebral uptake of propofol can be indicated by AUCa-v, the aim of this study were: I) To research the plasma concentrations of propofol at loss of consciousness varied with the rate of administration. 2) To study the rate- and time-course of the cerebral uptake during the intravenous continued infusion at a constant infusion rate. 3) To demonstrate the correlationship between the cerebral uptake of propofol and Spectral Edge Frequency (SEF). Methods: Twety-one adult patients were randomly allocated into three groups (A , B or C group) to receive a propofol constant administration at 6 , 9 and 12 mgkg抙?respectively for 3O~35 mm. The changes of SEF was recorded simultaneously during propofol infusion. Blood samples were taken simultaneously from radial artery and internal jugular bulb venous for measurement of propofol concentrations by high-performance liquid chromatography and then AUCaV can be calculated out. Results: There were no significant differences in the dose of propofol administered till the loss of consciousness (1.15 .. 1.10 and 1.20 mgkg?. However differences among the groups in the mean induction time were significant 4 (697 -. 441 and 313 see, P<0.05) Concentrations in arterial blood were 1.64 .. 2.24 and 2.78 ugmi1 (P<0.O1) and in venous blood were 1.18 1.40 and 1.69 ugmF?P<0.05, only between group A and C) There were no significant differences among the groups in AUCaV (4.56 -. 4.64 and 4.23 ugmf抦in?. There were no significant differences among the groups in the changes of 90%SEF at loss of consciousness (15. 58 15. 32 and 15. 05Hz, respectively). In arterial, the propofol concentrations increased progressively during the first 1 5mm and became stable later. in internal jugular bulb venous blood, propofol concentrations increased progressively during the first 30mm 30mm and 20mm in group A-. B and C, respectively. But C~b~ were lower than Ca and became stable and close to Ca. The accumulated AUCav were different at the same time-site before the equilibrium of cerebral uptake in three groups and different at the different time-site within every group, which shows the cerebral uptake of propofol is in a rate- and time-depengd.ing manner before equilibrum was achieved during propofol infusion at a constant rate. SEF bears a good negative correlations with arterial or venous blood concentrations and AUCaV during propofol administration at a constant rate. The correlation coefficients of them were rAUcav-. rCI~b~.. rca from the biggest one to the smallest in order and the average correlation coefficients were ?.948.. -0.909.. -0.809, respectively, which indicates that the cerebral uptake is the most accurate index in evaluation of the depth of anesthesia. Based on the equilibrium time of Ca and AUCa-v, the equilibrium half-life between the blood and the brain was 2.92 mm. 3 Conclusion: Both arterial and venous...