A blood processing apparatus comprising: an outer housing having a blood inlet and a blood outlet; a heat exchanger core arranged within the housing and having a core interior in fluid communication with the blood inlet, the heat exchanger core including an outer surface and a single elongate core aperture or two elongate core apertures disposed generally parallel to each other and in close proximity to each other formed through the outer surface such that blood may exit from the core interior; heat exchanger hollow fibers disposed about the heat exchanger core such that a heat exchanger fluid may flow through the heat exchanger hollow fibers and blood exiting from the single or two elongate core aperture is directed by the single or two elongate core apertures to flow across the heat exchanger hollow fibers in a circumferential direction; a cylindrical shell arranged coaxially about the heat exchanger hollow fibers, the cylindrical shell including an elongate channel formed within an inner surface of the shell, at a circumferential location substantially diametrically opposed to the location of the single or two elongate core apertures, and a radially disposed annular shell aperture disposed near an end opposite the blood outlet, wherein the elongate channel and the annular shell aperture are in fluid communication, such that blood passing over the heat exchanger hollow fibers flows into the elongate channel and exits the cylindrical shell through the annular shell aperture; gas exchanger hollow fibers disposed about the cylindrical shell such that gases may flow through the gas exchange hollow fibers and blood passing from the cylindrical shell may flow across the gas exchanger hollow fibers towards the blood outlet in a longitudinal flow path. an outer housing having a blood inlet and a blood outlet; a heat exchanger core arranged within the housing and having a core interior in fluid communication with the blood inlet, the heat exchanger core including an outer surface and a single elongate core aperture or two elongate core apertures disposed generally parallel to each other and in close proximity to each other formed through the outer surface such that blood may exit from the core interior; heat exchanger hollow fibers disposed about the heat exchanger core such that a heat exchanger fluid may flow through the heat exchanger hollow fibers and blood exiting from the single or two elongate core aperture is directed by the single or two elongate core apertures to flow across the heat exchanger hollow fibers in a circumferential direction; a cylindrical shell arranged coaxially about the heat exchanger hollow fibers, the cylindrical shell including an elongate channel formed within an inner surface of the shell, at a circumferential location substantially diametrically opposed to the location of the single or two elongate core apertures, and a radially disposed annular shell aperture disposed near an end opposite the blood outlet, wherein the elongate channel and the annular shell aperture are in fluid communication, such that blood passing over the heat exchanger hollow fibers flows into the elongate channel and exits the cylindrical shell through the annular shell aperture; gas exchanger hollow fibers disposed about the cylindrical shell such that gases may flow through the gas exchange hollow fibers and blood passing from the cylindrical shell may flow across the gas exchanger hollow fibers towards the blood outlet in a longitudinal flow path.