title: Propofol EC50 for inducing loss of consciousness is lower in the luteal phase of the menstrual cycle.
abstract: BACKGROUND
  Varying levels of female sex hormones during the menstrual cycle were found to influence the central nervous system. The goal of the present study was to investigate whether the median (50%) effective effect-concentration (EC50) of propofol inducing loss of consciousness (LOC) varies between the luteal and the follicular phases of the menstrual cycle.
  
  
  METHODS
  Twenty-two patients (follicular phase) and 20 patients (luteal phase) undergoing gynaecological procedures under general anaesthesia were enrolled on the study. Anaesthesia was conducted with a target-controlled infusion (TCI) of propofol. The initial target effect-site propofol concentration (Ceprop) was 3.5 µg ml(-1) and was adjusted stepwise by 0.5 µg ml(-1) at 4 min intervals by an up-down sequential method to reach LOC. Anaesthesia was maintained with a propofol TCI guided by the bispectral index. The correlation between female sex hormones and predicted Ceprop at the time of LOC was analysed and emergence time from anaesthesia was recorded.
  
  
  RESULTS
  Propofol EC50 to induce LOC was higher in patients in the follicular phase than those in the luteal phase (4.17 vs 3.58 µg ml(-1), P<0.05). Progesterone correlated significantly with Ceprop at LOC. Emergence time was also longer in the follicular group than in the luteal group (6.5 vs 5.0 min, P<0.05).
  
  
  CONCLUSIONS
  During general anaesthesia, patients in the luteal phase of the menstrual cycle had a lower propofol EC50 for LOC and a shorter emergence time compared with those in the follicular phase. Differences in progesterone levels between menstrual phases may contribute to these anaesthetic effects. Registry number of clinical trial ChiCTR-RCH-12002755.
authors.affiliation: Department of Anaesthesia, Women's Hospital , School of Medicine, Zhejiang University, Xueshi Road 1, Hangzhou, Zhejiang 310006, China.
authors.forename: F
authors.initials: F
authors.lastname: Fu
authors.forename: X
authors.initials: X
authors.lastname: Chen
authors.forename: Y
authors.initials: Y
authors.lastname: Feng
authors.forename: Y
authors.initials: Y
authors.lastname: Shen
authors.forename: Z
authors.initials: Z
authors.lastname: Feng
authors.forename: B
authors.initials: B
authors.lastname: Bein
mesh_terms: D000328:Adult; D000762:Anesthesia Recovery Period; D000771:Anesthesia, Intravenous; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000009:adverse effects; D056805:Consciousness Monitors; D003627:Data Interpretation, Statistical; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood; D013509:Gynecologic Surgical Procedures; D006801:Humans; D008183:Luteal Phase / Q000502:physiology*; D008597:Menstrual Cycle / Q000502:physiology*; D010149:Postoperative Pain / Q000453:epidemiology; D010880:Piperidines; D020250:Postoperative Nausea and Vomiting / Q000453:epidemiology; D011374:Progesterone / Q000097:blood; D015742:Propofol / Q000008:administration & dosage / Q000009:adverse effects; D000077208:Remifentanil; D014474:Unconsciousness / Q000139:chemically induced*; D055815:Young Adult
chemical_list: D018686:Anesthetics, Intravenous; D012739:Gonadal Steroid Hormones; D010880:Piperidines; D011374:Progesterone; D000077208:Remifentanil; D015742:Propofol
keywords: anaesthesia, general; anaesthetic i.v., propofol; hormones, progesterone; menstrual cycle