 At the following times when plasma glucose will be measured, an additional 6 mL of blood will be drawn from indwelling routine arterial line catheter into EDTA tubes and immediately centrifuged: baseline following induction, once during cardiopulmonary bypass, at arrival in the intensive care unit, and the morning after surgery- totaling 24 mls of blood. The platelet rich plasma will be withdrawn and one half of the volume immediately frozen for subsequent HPLC measurement of BH2 and BH4. The remaining plasma will be subjected to progressive centrifugation steps in order to concentrate the platelet fraction that will then be suspended in buffer and frozen. VASP expression and phosphorylation will be determined by Western blot. 