The Cp₅₀ Of Propofol Required To Insert PLMA And The Influences Of Fentanyl On Propofol Pharmacodynamics

Objective To determine the effective target plasma concentration (Cp50)required to insert ProSeal laryngeal mask airway (PLMA)in patients anesthetized with propofol by TCI and to investigate the influences of fentanyl on propofol pharmacodynamics . Methods Forty-six ASAⅠorⅡpatients aged 20-50 yr undergoing elective gynecological laparoscopy were randomly divided into two groups (n=23): propofol group (P group) and propofol-fentanyl group (P-F group). Anesthesia was induced with target-controlled infusion of propofol. The initial target plasma concentration of propofol for propofol group was 4μg/ml, and was 2.5μg/ml for propofol-fentanyl group. When the effect-site calculated concentration of propofol was equal to the plasma concentration according to the computer simulation, PLMA insertion was attempted. Criteria for acceptable insertion were: Muzi's score≤2, and mean arterial blood pressure, heart rate variation<20% of the baseline values within 3min after insertion. According to Dixon's up-and-down method, if PLMA insertion of proceeding patient was fail, the target plasma concentration of following patient was increased by 0.5μg/ml; if PLMA insertion of proceeding patient was successful, the target plasma concentration of following patient was decreased by 0.5μg/ml. Results The Cp50PLMA of propofol and propofol-fentanyl groups were 4.52μg/ml (4.01-6.25μg/ml) and 2.73μg/ml (2.26-3.31μg/ml) respectively. Conclusion The Cp50 of propofol required to insert PLMA was 4.52μg/ml in female patients (20-50 yrs) anesthetized with propofol by TCI and fentanyl 1μg/kg significantly decreases it.