1. Department of Anesthesiology, Hebei Provincial Hospital of Traditional Chinese Medicine, Shijiazhuang, Hebei 050011, P.R. China
2. Department of Gynecology, Hebei Provincial Hospital of Traditional Chinese Medicine, Shijiazhuang, Hebei 050011, P.R. China
3. Department of Physiology, Hebei Medical University, Shijiazhuang, Hebei 050017, P.R. China