A catheter is described. In one embodiment, the catheter includes: a shaft segment including a shaft segment uptake lumen and a shaft segment return lumen; and a distal end segment coupled to the shaft segment, the distal end segment including a distal end segment uptake lumen and a distal end segment return lumen, where the distal end segment central axis forms a non-zero angle with the shaft segment central axis when the catheter is in its unstressed configuration. In a second embodiment, the catheter includes: a shaft segment; and a distal end segment coupled to the shaft segment; where the uptake lumen distal end is terminated by a closed surface, further where the uptake lumen distal segment includes only one side hole. In a third embodiment, the catheter includes: an uptake lumen; and a return lumen; where at least a portion of the return lumen distal segment is helically coiled around the uptake lumen distal end.