Propofol and remifentanil effect-site concentrations estimated by pharmacokinetic simulation and bispectral index monitoring during craniotomy with intraoperative awakening for brain tumor resection

Different anesthetic techniques have been suggested for craniotomy with intraoperative awakening. We describe an a sleep-awake-a sleep technique with propofol and remifentanil infusions, with pharmacokinetic Simulation to predict the effect-site concentrations and to modulate the infusion rates of both drugs, and bispectral index (BIS) monitoring. Five critical moments were defined: first loss of consciousness (LOC1), first recovery of consciousness (ROC1), final of neurologic testing (NT). second loss of consciousness (LOC2), and second recovery of consciousness (ROC2). At LOC1, predicted effect-site concentrations of propofol and remifentanil were, respectively, 3.6 +/- 1.2 mu g/mL and 2.4 +/- 0.4 eta g/mL. At ROC1, predicted effect-site concentrations of propofol and remifentanil were, respectively, 2.1 +/- 0.3 mu g/mL and 1.8 +/- 0.3 eta g/mL. At NT, predicted effect-site concentrations of propofol and remifentanil were, respectively, 0.9 +/- 0.3 mu g/mL and 1.8 +/- 0.2 eta g/mL. At LOC2 predicted effect-site concentrations of propofol and rennfentanil were, respectively, 2.1 +/- 0.2 mu g/mL and 2.5 +/- 10.2 eta g/mL. At ROC2 predicted effect-site concentrations of propofol and remifentanil were. respectively, 1.2 +/- 0.5 mu g/mL and 1.4 +/- 0.2 eta g/mL (data are mean SE). A significative correlation was found between BIS and predicted effect-site concentrations of propofol (r(2) = 0.547 P < 0.001) and remifentanil (r(2) - 0.533. P < 0.001). Multiple regression analysis between BIS and propofol and remifentanil predicted effect-site concentrations at the different critical steps of the procedure was done and found also significative (r(2) = 0.7341, P < 0.001).