In this research the design of a Model Predictive Controller (MPC) is investigated for regulating Mean Arterial Pressure (MAP) by infusing the Sodium Nitro-Prusside (SNP) drug to the mathematical model of human patients during surgical operations where the blood pressure suffers from sudden rises due to multiple causes. The MPC is designed and compared with digital Proportional-Integral (PI) controller. MPC is chosen due to its known ability of estimating an optimal control action and dealing with input, state constraints and with disturbances. Simulation results for three patients' MAP models controlled by MPC and PI controllers that are designed for a sensitive patient model are analyzed and compared. Both controllers give a satisfactory response but MPC is preferred due to its optimally estimated actions.