Hayashida M, Sekiyama H, Orii R, Chinzei M, Ogawa M, Arita H, Hanaoka K, Takamoto S. Effects of Deep Hypothermic Circulatory Arrest With Retrograde Cerebral Perfusion on Electroencephalographic Bispectral Index and Suppression Ratio. Journal of Cardiothoracic and Vascular Anesthesia. 2007 Feb;21(1):61–7. doi: 10.1053/j.jvca.2006.02.029.