Influence of different menstrual phases on the Bispectral Index during dexmedetomidine sedation

To investigate the influence of different menstrual phases on the Bispectral Index (BIS) during dexmedetomidine (Dex) sedation, 40 patients with regular menstrual cycle, American Society of Anesthesiologists I-II, aged 18-40 years, undergoing selective gynecologic laparoscopic surgery, were enrolled. According to different menstrual phases and the serum progesterone concentration, they were divided into two groups: the follicular phase group (Group F) and the luteal phase group (Group L), and each group had 20 patients. Before anesthesia induction, patients were infused with an initial loading dose of Dex (1 μg/kg) for 10 minutes and then 0.5 μg/kg/h for 20 minutes. BIS and the changes in hemodynamic and respiratory parameters were recorded within those 30 minutes. Time to lower BIS to 70 and 60 in Group L was shorter than that in Group F (9.4 ± 1.3 minutes vs. 11.3 ± 2.1 minutes, p = 0.005; 11.3 ± 2.4 minutes vs. 14.0 ± 3.6 minutes, p = 0.021). The number of patients whose BIS reached 50 in Group L was greater than that in Group F (15 vs. 8, p < 0.05). The lowest BIS value in the Group L was lower than that in Group F (46.8 ± 6.3 vs. 55.3 ± 5.5, p = 0.006), and the heart rate of patients in both groups showed a decrease (p < 0.05). The sedative effect of Dex was more significant in patients during the luteal phase than during the follicular phase.