In spite of dramatic advances in surgery, management of hemostasis remains a consistent problem across all specialties of the endeavor. Current hemostasis management strategies are inefficient, and sometimes ineffective, involving significant loss of blood. To counter these limitations, a novel technique has been proposed employing an external hydrostatic pressure to reduce or staunch bleeding while still allowing sufficient tissue perfusion. The objective of the proposed program is to develop a surgical device based on the aqueous immersion principal that can be applied to a variety of surgical procedures. The specific focus of the Applicant's project will be for neurosurgical procedures in which the system is envisioned to consist of two main components: (1) a sterile kit containing an optically clear, hermetically sealed dome applied to the surgical site through which instruments may be passed, and (2) a regulated purge system consisting of a pump, cannulae, sensor, and feedback controller to apply pressure and maintain a clear visual field. Preliminary experiments have provided initial demonstration of feasibility. The current task is to translate these results into a practical system through the following two specific aims: (1) characterize the hydro- and hemodynamics of the AIS system with computational techniques, and (2) further design and evaluate the aqueous surgery system in-vitro. The first specific aim is to be accomplished with lumped-parameter modeling to couple the hydro- and hemodynamics of the isovolumetric cerebral space;and further by coupled finite-element and computational fluid dynamics analysis to more realistically describe the pressurized compartment and tissue perfusion. The second aim is to be accomplished with a simplified simulator (phantom) comprised of a cylindrical chamber, collapsible vessels, and cannula that will both validate the models of Aim 1 and enable development of a prototype of the fluid flush system and hermetic feed-through ports. When applied to surgical procedures requiring general anesthesia, successful completion of these aims has the potential to benefit between 35 and 53 million patients annually. Bleeding during surgery is an unsolved problem. In addition to the dangers associated with blood loss, bleeding causes the surgeon to divert his attention and spend extra time to stop the leaks. This project will develop a novel surgical device that will allow surgery to be performed under a slight water pressure that will control (or eliminate) bleeding. This device could help improve outcomes of tens of millions of surgical procedures annually.