Effects of the menstrual cycle on bispectral index and anesthetic requirement in patients with preoperative intravenous dexmedetomidine following propofol induction

Several studies have suggested that the menstrual cycle has the impact on sedation. No previous study has evaluated the effects of the menstrual cycle on sedation level and propofol requirement with preoperative intravenous dexmedetomidine. Sixty-four adult fertile women receiving general anesthesia for elective gynecologic surgery were included in the study. Patients were classified into four groups on the basis of the phase of menstrual cycle and whether infused dexmedetomidine preoperatively: Group FS: the follicular phase (days 8-12) and preoperative intravenous normal saline; Group FD: the follicular phase (days 8-12) and preoperative intravenous dexmedetomidine; Group LS: the luteal phase (days 20-24) and normal saline; Group LD: the luteal phase (days 20-24) and dexmedetomidine. The patients were infused respectively dexmedetomidine at 0, 1.0, 0 and 1.0 μg/kg over 10 min, and then propofol TCI, which was administered with target plasma concentration at 4.0 μg/ml. BIS, heart rate, MAP were recorded until BIS to 50. In the LD group, the descent range of the BIS values was significantly sharpest among the four groups at loss of eyelash reflex. From propofol administered to loss of eyelash reflex and BIS values reach to 50, propofol requirements were significantly least and duration were shortest in the LD group among the four groups. Menstrual cycle phases affect the sedation of propofol induction with preoperative intravenous dexmedetomidine, which is deeper in the luteal phase. We should cautious of excessive sedation by propofol anesthesia with preoperative dexmedetomidine in the luteal phase.