Characterizing Pressure and Flow Rate for Aqueous Immersion Surgery.

Hemorrhage control during surgery remains a major clinical challenge for surgeons. Bleeding can affect the safety and efficacy of any surgical procedure. There are well-established methods to address this side-effect of surgery, but all current technologies require the surgeon to direct attention to hemostasis rather than the continuance of the procedure. We have developed a novel surgical method, titled aqueous immersion surgery (AIS), that is able to sustain a bloodless surgical field by providing a controlled hydraulic pressure (immersion pressure) on the bleeding site. Together with the replenishment of an immersion fluid (immersion flow rate), AIS maintains optical clarity of the surgical field. This numerical study was undertaken to investigate the influence of the rate exchange of the immersion fluid on the concentration of blood, hence optical clarity therein. A 3-dimensional multicomponent simulation was performed to evaluate the mixing of blood from an idealized arterial bleeding vessel under pulsatile conditions. With an increase in immersion pressure, bleeding was reduced and increased perfusion was observed. Additionally, the magnitude and direction of the flow field affected the deflection of the bleeding trajectory and, in turn, affected the removal rate of blood from the surgical field. For an idealized case, an optimal immersion flow rate was found for immersion pressures of 100 and 110 mm Hg. From this study, fluid dynamic guidelines are postulated to support future development of AIS.