The goal of this exploratory/developmental grant is to use novel technology to determine and differentiate the effects of maternal general anesthesia to those of regional anesthesia on fetal cerebral oxygenation. Maintaining an adequate supply of oxygen and nutrients to the fetal brain is of primary importance during manipulations of the gravid female. Prevailing medical practice encourages the use of general anesthesia for such procedures as non-obstetric related surgery and emergent cesarean section. However, relatively little is known about the effects of inhalational agents (e.g. isoflurane) upon fetal cerebral oxygen status. By extension, one could propose that regional techniques (e.g. epidermal anesthesia) might have reduced fetal effects because of the localization of anesthetic to the maternal CNS. However, this benefit could be counter-acted by the maternal hypotension and with respect to fetal effects, is the impracticability of measuring oxygen levels. To that end, we are developing a means (near infrared spectroscopy; NIRS) of continually measuring in utero fetal cerebral oxygenation in pregnant sheep. An NIRS device was designed specifically for in utero animal experimentation. Currently, we have validated our NIRS methodology by measuring changes in fetal sheep cerebral oxygenation in response to systemic decreases in oxygen levels produced by umbilical cord occlusion. With the present proposal, we plan to further optimize our technology by applying it to answer a clinically-relevant question: Does maternal anesthesia alter fetal cerebral oxygenation? Completion of this study will yield new information regarding the effects of maternal anesthesia on fetal cerebral oxygenation and well-being. In addition, this research will produce clinically relevant data that will be of significant interest to anesthesiologists, obstetricians, and general surgeons who are presented parturients with fetal or abdominal distress. It is expected that the results of these studies will be used to further develop and refine standards of care for anesthetic use during pregnancy. These results will also validate our NIRS methodology, and will allow us to refine-optimize the technology and to develop the appropriate analysis tools to quantitatively evaluate the resultant NIRS data. Finally, the results will serve as the basis for a long-term outcome study designed to identify the optimal anesthetic parameters to be used during an episode of fetal distress, maternal surgery, and eventually fetal surgery.