Study Of The Time Course Of The Clinical Effect Of Propofol Compared With The Predicted Effect-Site Concentration:Performance Of Two TCI Models

Objective:We aimed to study which of the two pharmacokinetic-pharmacodynamic models better maintains the clinically observed effect of propofol, as assessed by the BIS monitoring with a constant effect-site concentration over time.Methods:Forty American Society of Anesthesiologists physical status Ⅰ-Ⅱ,female patients,who were scheduled for surgery with general anesthesia, were randomized to receive propofol administered by Marsh (Group M) or Schnider model (Group S), using a view model. At any given time, the researcher was able to switch this TCI model to an effect-site-controlled TCI setting, using the same pharmacokinetic-pharmacodynamic parameters as defined by the randomization process. All patients were asked to relax for10min before starting the drug administration, then received propofol at a constant rate of12mg/kg/h until loss of response to name calling. The corresponding effect-site concentration of propofol as calculated by the respective models, was set as a target for effect-site-controlled TCI. BIS was derived from the frontal EEG and calculated by a BIS monitor using a BIS-Sensor electrode thougout the entire study period. Results:Steady state in BIS value was found after, respectively,14.0min in group M and18.0min in group S, at a clinically relevant lighter level of hypnotic drug effect than the time of LORNC. Additionally, between14.0-22.0min, BIS and MOAA/S of group M was significantly lower compared with that in group S.Conclusions:Targeting effect-site concentration at LORNC with effect-site-controlled model, Schnider or Marsh, did not translate into a corresponding constant effect immediately. Infusion with Marsh model was easier to abtain BIS steady-state, while infusion with Schnider model maintained lighter level of hypnotic drug effect.