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Background: This study was to estimate the predicted effect-site concentration of propofol administered by a target-controlled infusion (TCI) for maintenance of anesthesia based on the bispectral (BIS) index as a measure of hypnosis in laparoscopic surgery.

Method: One-hundred and sixty unpremedicated patients undergoing gynecologic laparoscopy were assigned randomly to receive one of the target effect-site concentrations of propofol 2.0, 2.5, 3.0, 3.5 and 4.0 μg/ml during TCI with propofol and sufentanil. The dose–response relationship of propofol for the maintenance of adequate anesthesia based on BIS, movement and hemodynamic response was investigated using a fixed effect-site concentration of sufentanil (0.2 ng/ml). The BIS values, hemodynamic variables, time course during emergence and intraoperative awareness were also assessed.

Results: The predicted effect-site propofol concentrations for adequate anesthesia at the skin incision in 50% (EC50) and 95% (EC95) of patients undergoing gynecologic laparoscopy were 2.2 and 3.7 μg/ml, respectively. The predicted propofol EC50 and EC95 to maintain adequate anesthesia in these patients were 2.6 μg/ml (95% CI 2.3–2.7 μg/ml) and 3.6 μg/ml (95% CI 3.3–4.0 μg/ml), respectively. The BIS values, effect-site concentration of propofol, hemodynamic data and time course during emergence and post-operative adverse events were comparable in each group. There were no reports of intraoperative awareness in the post-anesthetic care unit.

Conclusion: Based on the anesthetic depth assessed by the clinical signs and BIS monitoring, the predicted effect-site propofol concentrations for the maintenance of anesthesia in patients undergoing gynecologic laparoscopy were similar in those administered adequate anesthesia at the skin incision during TCI.