A system for accessing a patient's vascular system may have a tube with a wall that defines an exterior surface and lumen with a proximal end and a distal end, and a guidewire that is deployable, by sliding distally, from a retracted position in which the guidewire resides in the lumen, to a deployed position in which the guidewire extends beyond the distal end. The system may further have a retraction mechanism that can be actuated to retract the guidewire from the deployed position to the retracted position, or a protective shield that can be actuated to extend distally from the distal end of the tube to cover the guidewire in the deployed position.