Effect-site target-controlled infusion of propofol: comparison of Schnider and modified Marsh models

BACKGROUND: We investigated effect-site concentrations of propofol, changes in blood pressure and heart rate, time to loss of consciousness, time to loss of eyelid reflex and awakening time during anesthesia using effect-site target-controlled infusion, to compare the differences between Schnider and modified Marsh model. METHODS: Forty American Society of Anesthesiologists (ASA) physical status I or II patients between the ages of 18 and 55 years old and who were scheduled for elective surgery under general anesthesia were enrolled in this study. The patients were randomized into two groups: one group using modified Marsh model (Group 1) and the other group using Schnider model (Group 2). Effect-site concentrations of propofol, blood pressure, heart rate and BIS at each anesthetic stage were recorded. Time to loss of consciousness, time to loss of eyelid reflex and awakening time were measured. RESULTS: Group 1 showed shorter time to loss of consciousness and eyelid reflex at the lower effect-site concentration of propofol than Group 2 (P < 0.05). The effect-site concentrations of Group 1 were higher than those of Group 2 at eye opening and extubation (P < 0.05). CONCLUSIONS: Induction of anesthesia is achieved at lower effect-site concentration of propofol and more rapidly in the modified Marsh model than in the Schnider model. However the effect-site concentrations of propofol for awakening are higher in the modified Marsh model than in the Schnider model.

Target Effect-site Controlled Infusion of Propofol by Schnider Model: Comparison of Gender and Age / 대한마취과학회지

BACKGROUND: We investigated effect-site median effective concentration (EC50) of propofol for loss of consciousness and effect-site concentration at each anesthetic stage and awakening time to compare the differences by gender or age of patients using Schnider model. METHODS: Total 91 patients were allocated into 4 groups: male patients aged 18-34 year (Group 1), male patients aged 35-55 years (Group 2), female patients aged 18-34 years (Group 3) and female patients aged 35-55 years (Group 4). The effect-site EC50 for loss of consciousness was calculated and the effect-site concentration of propofol at each anesthetic stage and the awakening time of each group were recorded. RESULTS: The effect-site EC50 of propofol for loss of consciousness was 4.53 +/- 0.30microgram/ml, 4.60 +/- 0.25microgram/ml, 4.13 +/- 0.39microgram/ ml and 4.47 +/- 0.65microgram/ml in group 1, 2, 3, and 4, respectively. The effect-site concentrations in male patients aged 18-34 years were significantly higher than those in female patients. The awakening time of female patients aged 35-55 years was shorter than that of male patients. CONCLUSIONS: There were no significant differences of effect-site EC50 for the loss of consciousness of propofol with target effect-site controlled infusion by Schnider model among the groups. However the effect-site concentrations and the awakening time of propofol by Schnider model showed differences in patients' gender and age.