Lee JM, et al. - This inquiry was set up to determine the 90% effective concentration (EC₉₀) of remifentanil for blunting of cardiovascular responses to head fixation during neurosurgery via bispectral index (BIS) monitoring. Findings demonstrated that noxious cardiovascular responses could be abated by adjusting the effect-site target concentration (Ce) of remifentanil to approximately 6.5 ng/mL before head fixation in 90% of neurosurgical ASA I-II patients aged 20 to 65 years old during propofol target-controlled infusion titrated to maintain BIS between 40 and 50.