  The process of anesthesia is nonlinear with time delay and also there are
some constraints which have to be considered in calculating administrative drug
dosage. We present an Extended Kalman Filter (EKF) observer to estimate drug
concentration in the patient's body and use this estimation in a state-space
based Model of Predictive Controller (MPC) for controlling the depth of
anesthesia. Bispectral Index (BIS) is used as a patient consciousness index and
propofol as an anesthetic agent. Performance evaluations of the proposed
controller, the results have been compared with those of a MPC controller. The
results demonstrate that state-space MPC including the EKF estimator for
controlling the anesthesia process can significantly increase the robustness in
encountering patients' delay deviations in comparison with the MPC.
