A method, technique and system is disclosed for the delivery of therapeutic agents and/or into the bulk brain tissues and other parts, tissues and organs of the body, including vasculature. A novel form of coaxial catheter provides a means for implanting an outer tube into the brain, then inserting an inner tube into the outer tube and aligning them such that port holes on both of the tubes will overlap and permit a flux of the therapeutic agent to flow into the brain in such a way as to minimize the effects of trapped air, virtually eliminate backflow of the agent, and avoid the potential for additional damage to the brain since only one surgical placement of the outer tube is needed. Similarly, the method, technique system may be utilized to remove fluids or other medium from the brain, tissues, and organs to minimize the effects of escaped air or negative pressure.