RESUMEN
Background@#The depth of anesthesia is an essential factor in surgical prognosis. The neurotoxic effect of chemotherapeutic drugs affects the sensitivity to anesthetics. This study was conducted to determine whether the effect-site concentration (Ce) of propofol for loss of consciousness (LOC) differs in patients undergoing preoperative chemotherapy. @*Methods@#A total of 60 patients scheduled for surgery for colorectal cancer under general anesthesia were included in this study. Patients who had received chemotherapy comprised the experimental (C) group, and those without a previous history of chemotherapy comprised the control (N) group. Propofol was administered as an effect-site target-controlled infusion, and the Modified Observer’s Assessment of Alertness/Sedation (MOAA/S) scores were evaluated. When the plasma concentration and Ce were similar, and if the MOAA/S score did not change, the target Ce was increased by 0.2 μg/ml; otherwise, the Ce was maintained for 2 min and then increased. @*Results@#The Ce values of propofol for loss of verbal contact (LVC) in groups C and N were 2.40 ± 0.39 and 2.29 ± 0.39 μg/ml (P = 0.286), respectively, and those for LOC in groups C and N were 2.69 ± 0.43 and 2.50 ± 0.36 μg/ml (P = 0.069), respectively. No significant difference was observed in Ce values between the two groups. @*Conclusions@#Chemotherapy had no effect on the Ce of propofol for LVC and LOC in patients with colorectal cancer. We do not recommend reducing the dose of propofol for the induction of LOC in patients with colorectal cancer undergoing chemotherapy.