A catheter assembly comprises a catheter including a catheter wall and a lumen extending lengthwise of the wall. The wall has inner and outer surfaces. The wall includes plural openings that extend through the wall and communicate with the lumen. An elongated hollow needle includes a proximal end portion and a distal end portion. The needle is movable in the lumen to move the distal end portion between the openings. The distal end portion is directed radially outward so as to extend into an adjacent opening. The distal end portion has a configuration that stores potential energy when in the lumen. The potential energy is converted to kinetic energy to produce movement of the proximal end portion as the distal end portion moves from the inner surface of the catheter wall across an edge of an opening. The movement of the proximal end portion is haptically perceptible.