A medical catheter assembly includes a catheter hub, an elongate catheter member extending from the catheter hub and having at least one longitudinal lumen for passage of fluids, an extension tube extending from the catheter hub and defining an internal lumen in fluid communication with the at least one longitudinal lumen of the catheter member and a clamp positionable about the extension tube. The catheter hub defines a reduced profile to facilitate passage of the catheter hub through a surgical tunnel. The clamp includes first and second clamp sections and defines a longitudinal clamp axis. The clamp has a longitudinal opening for passage of the extension tube and a movable member adapted to move from a first position to a second position to substantially close the internal lumen. The first and second clamp sections are separable to facilitate transverse positioning of the clamp sections about the extension tube.