A Pilot Study of Optic Nerve Ultrasound Following Cardiopulmonary Bypass

The purpose of the proposed study is to evaluate the incidence of subtle increases in intracranial pressure (ICP) following cardiopulmonary bypass (CPB) using optic nerve sheath diameter (ONSD), measured by non-invasive ultrasound. As direct measurements of ICP are not feasible following CPB, ONSD will be used as a correlate of ICP. ONSD has been shown to be effective in the ICU and emergency room setting for detecting increased ICP and is an accepted standard for such measurements. The primary hypothesis is that changes in ICP occur following CPB without clinically appreciable signs and symptoms. These changes in ICP will be reflected by changes in ONSD. If there is a significant incidence of sub-clinical cerebral edema and increased ICP postoperatively, these findings may impact postoperative hemodynamic and ventilation goals and techniques.