Circuitry and Priming : The cardio pulmonary bypass circuit consists of oxygenator, tubings, cannulae, cardiotomy reservoirs and cardioplegia attachments. The first step is to prime the circuit with either clear fluid or with addition of blood. The clear prime consists of crystalloids, colloids, albumin or plasma. Most of the adult patients do not need addition of blood in the prime. On bypass, the haematocrit is brought down to 18 or 20 (haemo dilution). In babies and children, blood and albumin added to the prime. By sophistication of the oxygenators, priming volumes have been brought down to a minimum (mini-prime).