An extracorporeal blood heating and cooling system for a cardiopulmonary bypass system, the heating and cooling system comprising: an oxygenator a heater-cooler unit; a coolant flow circuit that is configured to pass coolant through the heater-cooler unit and the oxygenator; and a cardioplegia coolant circuit that is configured to pass coolant through the heater-cooler unit and a cardioplegia heat exchanger; wherein the oxygenator comprises a first plurality of coolant conduits that form part of the coolant flow circuit, and wherein when the heating and cooling system is in a coolant mode, blood passing through a first extracorporeal blood circuit contacts an exterior surface of the first plurality of coolant conduits; wherein the cardioplegia heat exchanger comprises a second plurality of coolant conduits that are part of the cardioplegia coolant circuit, and wherein when the heating and cooling system is in the coolant mode, blood passing through a second extracorporeal blood circuit contacts an exterior surface of the second plurality of coolant conduits; the heating and cooling system characterized in that when the heating and cooling system is in a purging mode, the coolant flow circuit and the cardioplegia coolant circuit contain temperature-controlled coolant having a trisodium phosphate concentration of about 1-35 millimole/liter; wherein when the heating and cooling system is in the coolant mode, the coolant flow circuit and the cardioplegia coolant circuit contain temperature-controlled water having a trisodium phosphate concentration of about 1-10 millimole/liter; and wherein when the heating and cooling system is in the coolant mode or the purging mode, the first and second plurality of coolant conduits are capable of maintaining a trisodium phosphate concentration ratio across the wall of each coolant conduit of at least 100:1, from the interior to the exterior of each coolant conduit. an oxygenator a heater-cooler unit; a coolant flow circuit that is configured to pass coolant through the heater-cooler unit and the oxygenator; and a cardioplegia coolant circuit that is configured to pass coolant through the heater-cooler unit and a cardioplegia heat exchanger; wherein the oxygenator comprises a first plurality of coolant conduits that form part of the coolant flow circuit, and wherein when the heating and cooling system is in a coolant mode, blood passing through a first extracorporeal blood circuit contacts an exterior surface of the first plurality of coolant conduits; wherein the cardioplegia heat exchanger comprises a second plurality of coolant conduits that are part of the cardioplegia coolant circuit, and wherein when the heating and cooling system is in the coolant mode, blood passing through a second extracorporeal blood circuit contacts an exterior surface of the second plurality of coolant conduits; the heating and cooling system characterized in that when the heating and cooling system is in a purging mode, the coolant flow circuit and the cardioplegia coolant circuit contain temperature-controlled coolant having a trisodium phosphate concentration of about 1-35 millimole/liter; wherein when the heating and cooling system is in the coolant mode, the coolant flow circuit and the cardioplegia coolant circuit contain temperature-controlled water having a trisodium phosphate concentration of about 1-10 millimole/liter; and wherein when the heating and cooling system is in the coolant mode or the purging mode, the first and second plurality of coolant conduits are capable of maintaining a trisodium phosphate concentration ratio across the wall of each coolant conduit of at least 100:1, from the interior to the exterior of each coolant conduit.