Increasingly complex neonatal cardiac repairs are being performed on younger and younger infants with greater success. Yet as treatment runs closer to what is tolerable to the body, smaller details become major determinants of success. Two outstanding independent variables are associated with poorer outcome; excess hemorrhage and prolonged operative time, particularly cardiopulmonary bypass time. Excess hemorrhage requires excess blood transfusion with the risks of infectious agent transmittal and hemostatic and metabolic insult to the neonate. Long bypass times produce more pronounced inflammatory responses by the host with secondary organ dysfunction. The ability to minimize these factors will increase the safety of the operation and will significantly reduce expenses such as ICU, hospital stays and blood product costs. Recent advances in laser technology may provide this improvement in hemostasis and thereby reduce the operation time. This project will study the impact of laser activated hemostatic methods on conventional anastomotic techniques as well as laser welding methods developed previously by the research team. Phase I will include both in vitro and in vivo experiments. Spectroscopic measurements on neonatal tissue will guide the selection of the laser wavelength. Both temperature and optical feedback techniques developed under the CEE/LLNL CRADA will be used for controlling the laser to promote strong tissue bonds. Tissue solders or patches will be evaluated to enhance tissue welding and hemostasis. Phase II will focus on sensor control of the laser and will be based on neonatal tissue signature change at the welding endpoint. The subsequent development of a reliable tissue welding system will provide the bond strength and the ability to grow rapidly as required in the neonate.