title: The peak bispectral index time cannot predict early phase propofol pharmacodynamics with effect site-controlled infusion algorithm.
abstract: OBJECTIVE
  The plasma-effect site equilibration rate constant (ke0) of propofol was determined with peak bispectral index (BIS) time (T(PEAK)) in our previous study. The present study has been conducted to evaluate the ke0's performance with effect site-controlled infusion algorithm.
  
  
  METHODS
  Forty unpremedicated patients were randomized to group TE1 (Schnider's pharmacokinetic model with ke0 adapted to T(PEAK) = 74s) and TE2 (T(PEAK) = 96s). In stage 1, all patients received propofol with effect-site concentration (Ce) controlled infusion. Once the pump had injected the mass of propofol necessary to achieve pre-set Ce and while the infusion was stopped, target was reset at 0 μg/ml. When BIS returned to 80 or above, then, in stage 2, the patients received plasma concentration controlled infusion for 10 min. The time of loss of responsiveness (LOR) and BIS were recorded. The differences of Ce at the time of LOR, lowest BIS between stages 1 and 2, hysteresis loop were used to evaluate the performance of ke0.
  
  
  RESULTS
  In both groups, the calculated propofol Ce at the time of LOR in stages 1 and 2 differed significantly (P<0.01); the mean lowest BIS in stage 1 were significantly higher than those in stage 2 (P < 0.05).The relations of propofol Ce versus BIS revealed the apparent hysteresis loop.
  
  
  CONCLUSIONS
  The study cannot clinically validate the accuracy of application of ke0 derived from the T(PEAK) = 74 s of BIS with Schnider propofol pharmacokinetic model.
authors.affiliation: Department of Anesthesiology and Pediatric Clinical Pharmacology Laboratory, Shanghai Children's Medical Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Niu
authors.forename: Shan-Juan
authors.initials: SJ
authors.lastname: Wang
authors.forename: Ma-Zhong
authors.initials: MZ
authors.lastname: Zhang
authors.forename: Yong-Lei
authors.initials: YL
authors.lastname: Huang
authors.forename: Lin
authors.initials: L
authors.lastname: Song
authors.forename: Qing
authors.initials: Q
authors.lastname: Yu
authors.forename: Wen-Yin
authors.initials: WY
authors.lastname: Xu