Figure 50-31 Illustration outlining the essential features of a typical cardiopulmonary bypass circuit. Venous blood is drained into a venous reservoir by gravity (although vacuum assist devices can be added) from the right atrium by using either a single cannula or bicaval cannulation. Blood can also be salvaged from the surgical field and cardiopulmonary cavities and returned to the venous reservoir by cardiotomy suckers and appropriately placed vents, respectively, thus avoiding increases in left ventricular pressure and left ventricular distention resulting from collateral flow in the presence of aortic cross-clamping. Blood from the venous reservoir is pumped by a nonocclusive roller-head pump through the oxygenator to the patient. The content of the gas flow to the oxygenator determines the arterial blood gas and acid-base content. Various monitoring and safety devices are shown for these circuits. Cardioplegia can also be delivered by a roller-head pump and is monitored as shown. Both cardioplegia and the patient's blood can be heated-cooled by heat exchangers connected to a water-based heater-cooler device.