Feedback control of intracranial pressure using mannitol

A discrete-time model describing intracranial pressure (ICP) dynamics is extended to account for changes in blood osmolarity due to an i.v. injection of mannitol. It includes the effect of a blood osmolarity change on cerebrospinal fluid (CSF) formation and absorption. In order to maintain the ICP at a desired lowered level, a control algorithm is constructed. The controller is designed by minimizing a performance criterion, which consists of the mean squared error between the measured ICP and desired ICP, and the squared input. Minimizing the performance criterion specifies the controller. For on-line implementation, an approximately optimal controller is suggested. Simulation results show the feasibility of using this controller to regulate ICP.