Search

Background: Perioperative disorder of magnesium, an important cation in the human body, may affect clinical anesthesia. The pharmacological data of propofol use, which is popularly used in the anesthesiology department and intensive care unit, is incomplete in Chinese patients. This study aimed to assess the effect of magnesium sulfate on the calculated plasma medial effective concentration (Cp50cal) of propofol at loss of response to command in Chinese females., Methods: Fifty patients undergoing gynecological laparoscopic surgery were randomly divided into the control group and the magnesium group. Before induction, magnesium sulfate (30 mg/kg) or placebo (equal volume of 0.9% saline) was given to patients in the magnesium group or the control group, respectively. Propofol was infused using a target-controlled infusion system, with a target concentration for each patient decided by up-and-down sequential allocation. After the equilibration between target plasma concentration and effective-site concentration, the state of consciousness was assessed. For determination of serum magnesium and calcium concentration, blood samples were taken before induction, after induction and at the end of surgery., Results: The Cp50cal was 2.52 µg/ml (2.47 - 2.57 µg/ml) for patients in the control group, and 2.46 µg/ml (2.41 - 2.51 µg/ml) for those in the magnesium group. A significant reduction of Cp50cal was observed (P = 0.021). There was a significant difference between the serum magnesium concentrations after induction and at the end of the surgery (P < 0.05). In the magnesium group, there was a trend toward decreasing after surgery, while in the control group, Cp50cal decreased significantly (P < 0.01)., Conclusions: Cp50cal of propofol at loss of response to command was 2.52 µg/ml (2.47 - 2.57 µg/ml) for Chinese female adults in this study. Infusion of 30 mg/kg magnesium sulfate may reduce the Cp50cal of propofol at loss of consciousness, which implies that magnesium may enhance the pharmacological effects of propofol.

Background: Although the performance of target-controlled infusion (TCI) have been studied extensively, the accuracy and safety of a TCI system that targets the effect site remains to be demonstrated. This study was to investigate the relations of TCI of propofol to its concentrations in cerebral spinal fluid (CSF), the effect-site concentrations and bispectral index (BIS)., Methods: Twelve mongrel dogs were used for investigations. The target effect-site concentration was set at 3 microg/ml and the infusion was lasted for 15 minutes. CSF and blood samples were then collected and propofol concentrations were determined by using high performance liquid chromatography with fluorescence detection. BIS and hemodynamic data were monitored continuously., Results: The predicted plasma concentrations were generally overestimated. Median performance error (MDPE) and absolute median performance error (MDAPE) were -10.0% and 29.9% respectively. Propofol CSF concentrations were much lower than its effect-site concentrations. Changes in BIS were consistent with propofol concentrations in CSF, both of which changed direction at 5 minutes while the effect-site concentrations relatively lagged behind. Better correlation (r(2) = 0.9195) was found between BIS and CSF concentrations, when compared with that between BIS and effect-site concentrations (r(2) = 0.554)., Conclusion: With 1% enflurane inhaled, the inconsistency of drug effect to the effect-site concentrations may result from inaccuracy of pharmacokinetic parameters. CSF may show effect-site concentrations more accurately than plasma when using target effect-site concentration infusion.