A catheter assembly (10) having an outer catheter (12) and an inner catheter (14) extending coaxially through the outer catheter, and a hub (16). The inner catheter (14) is axially movable within and with respect to the outer catheter (14) by use of an actuator assembly (130) such that the catheter assembly has an opened condition permitting fluid communication with vasculature of a patient, and a closed condition preventing fluid communication with the vasculature of the patient. The opened condition permits the intended use of the catheter assembly such as for hemodialysis of the patient. In the closed condition, locking solution may be maintained in the catheter assembly and later removed therefrom, with essentially no locking solution leaving the catheter assembly or entering the patient. The actuator assembly (130) is secured to a proximal end portion (128) of the inner catheter (14) as it protrudes proximally from the hub (16), where it is accessible to the practitioner. The actuator assembly (130) may comprise an adapter sleeve (90) fixed to the inner catheter (14), and a swivel sleeve (92) which is rotatable with respect to both the adapter sleeve (90) and the hub (16).