A large number of physiological and clinical studies were conducted that better characterized brain physiology and function during cardiac surgery and cardiopulmonary bypass (CPB). The physiological variables were investigated as possible causes of perioperative brain injury included mean arterial pressure (MAP), body temperature, hematocrit (HCT), bypass pump flow rate, the use of pulsatile flow and CO2 management. CPB may affect cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMRO2), but these changes are qualitatively no different from those that would occur under non-CPB conditions; they are simply quantitatively greater. Stroke is one of the most devastating complications following adult cardiac surgery. Stroke rates vary greatly in cardiac surgical reports depending on the patient population and the type of surgery. Peel and colleagues looked at stroke timing in on-pump and off-pump CABG patients and found that on-pump CABG was associated with earlier events than off-pump CABG.