A blood processing apparatus (150; 250) comprising: a housing (152; 252) having a blood inlet (158; 258) and a blood outlet (160; 260), the blood inlet extending into an interior of the housing (152; 252); a heat exchanger core (166; 270) extending coaxially within the housing (152; 252) and having a core interior in fluid communication with the blood inlet (158; 258), the heat exchanger core (166; 270) including an outer surface and a plurality of elongate core apertures (176; 276) formed within the outer surface, the plurality of elongate core apertures (176; 276) configured to permit blood to pass from the core interior; heat exchanger hollow fibers disposed about the heat exchanger core (166; 270) such that a heat exchanger fluid may flow through the heat exchanger hollow fibers and blood passing from the plurality of elongate core apertures (176; 276) may flow radially outwardly across the heat exchanger hollow fibers; a cylindrical shell (170; 274) extending coaxially about the heat exchanger core, the cylindrical shell (170; 274) including a shell aperture (178; 282) configured to permit blood to pass to an exterior of the cylindrical shell (170; 274); and gas exchanger hollow fibers disposed about the cylindrical shell (170; 274) such that gases may flow through the gas exchange hollow fibers and blood passing from the shell aperture (178; 282) may flow across the gas exchanger hollow fibers and towards the blood outlet (160; 260), wherein the shell aperture (178; 282) comprises a radially disposed aperture disposed near an end of the cylindrical shell (170; 274) opposite that of the blood inlet (158; 258) such that blood exiting the radially disposed aperture flows over the gas exchanger hollow fibers in a longitudinal direction, wherein each elongate core aperture is part of a structure including a first elongate channel and a second elongate channel, wherein a dividing plate is disposed between the first elongate channel and the second elongate channel, wherein each of the first and second elongate channels (204; 206) are formed with a floor disposed at an angle with respect to a longitudinal axis of the core, such that as the floor extends longitudinally away from the blood inlet the depth of the channel decreases, and wherein the angle of said floor with respect to the longitudinal axis is between 5 and 30 degrees. a housing (152; 252) having a blood inlet (158; 258) and a blood outlet (160; 260), the blood inlet extending into an interior of the housing (152; 252); a heat exchanger core (166; 270) extending coaxially within the housing (152; 252) and having a core interior in fluid communication with the blood inlet (158; 258), the heat exchanger core (166; 270) including an outer surface and a plurality of elongate core apertures (176; 276) formed within the outer surface, the plurality of elongate core apertures (176; 276) configured to permit blood to pass from the core interior; heat exchanger hollow fibers disposed about the heat exchanger core (166; 270) such that a heat exchanger fluid may flow through the heat exchanger hollow fibers and blood passing from the plurality of elongate core apertures (176; 276) may flow radially outwardly across the heat exchanger hollow fibers; a cylindrical shell (170; 274) extending coaxially about the heat exchanger core, the cylindrical shell (170; 274) including a shell aperture (178; 282) configured to permit blood to pass to an exterior of the cylindrical shell (170; 274); and gas exchanger hollow fibers disposed about the cylindrical shell (170; 274) such that gases may flow through the gas exchange hollow fibers and blood passing from the shell aperture (178; 282) may flow across the gas exchanger hollow fibers and towards the blood outlet (160; 260), wherein the shell aperture (178; 282) comprises a radially disposed aperture disposed near an end of the cylindrical shell (170; 274) opposite that of the blood inlet (158; 258) such that blood exiting the radially disposed aperture flows over the gas exchanger hollow fibers in a longitudinal direction, wherein each elongate core aperture is part of a structure including a first elongate channel and a second elongate channel, wherein a dividing plate is disposed between the first elongate channel and the second elongate channel, wherein each of the first and second elongate channels (204; 206) are formed with a floor disposed at an angle with respect to a longitudinal axis of the core, such that as the floor extends longitudinally away from the blood inlet the depth of the channel decreases, and wherein the angle of said floor with respect to the longitudinal axis is between 5 and 30 degrees.