The key determinants of organ perfusion are (a) generation of a blood pressure within the range that allows end-organs to maintain constant blood flow and (b) delivery of oxygen at values exceeding the current rate of consumption. Deliberate evaluation of these physiologic relationships throughout cardiac surgery and postoperatively can be used to define an individual's risk for organ dysfunction and to establish end points of resuscitation. A consistent focus on these parameters is relevant to all patient conditions regardless of whether the patient is in or out of the operating room, or whether receiving extracorporeal support. While the focus of this issue of SCVA is on cardiopulmonary bypass, optimizing oxygen delivery is relevant to all high-risk operative patients and their postoperative care. The reader will note that some of the monitoring modalities are more appropriate for use in the operating room than intensive care unit, and vice versa. Matching key patient problems to the different performance characteristics and anatomical constraints of each monitoring modality demands a focused yet flexible mindset.