An infusion system comprising: a fluid source; a double action infusion pump in communication with the fluid source, the double action infusion pump including: a cylinder, a reciprocating piston received within the cylinder, the reciprocating piston separating a first pump chamber from a second pump chamber of the cylinder, each of the first and second pump chambers (300, 302) having a variable volume, a reciprocating motor coupled with the reciprocating piston, and the first and second pump chambers (300, 302) alternate between filling and evacuating conditions with reciprocation of the reciprocating piston through operation of the reciprocating motor, and the speed of reciprocation is varied to provide a continuous output of fluid between the first and second pump chambers (300, 302); and a catheter coupled with the double action infusion pump, the catheter including one or more infusion ports near a catheter distal portion (500; 600), and the one or more infusion ports (112; 508; 604) receive and expel the continuous output of fluid from the double action infusion pump, wherein the piston is reciprocated along an intermediate segment of the cylinder and through top and bottom zones (406, 408), and along the intermediate segment of the cylinder the reciprocating motor moves the piston at a first piston speed, the infusion system being characterized in that within the top and bottom zones (406, 408) the reciprocating motor moves the piston at a second piston speed greater than the first piston speed, such that the continuous output of the double action pump provides or approaches a static flow rate, and the continuous infusion flow from the one or more infusion ports similarly provides or approaches a static flow rate. a fluid source; a double action infusion pump in communication with the fluid source, the double action infusion pump including: a cylinder, a reciprocating piston received within the cylinder, the reciprocating piston separating a first pump chamber from a second pump chamber of the cylinder, each of the first and second pump chambers (300, 302) having a variable volume, a reciprocating motor coupled with the reciprocating piston, and the first and second pump chambers (300, 302) alternate between filling and evacuating conditions with reciprocation of the reciprocating piston through operation of the reciprocating motor, and the speed of reciprocation is varied to provide a continuous output of fluid between the first and second pump chambers (300, 302); and a catheter coupled with the double action infusion pump, the catheter including one or more infusion ports near a catheter distal portion (500; 600), and the one or more infusion ports (112; 508; 604) receive and expel the continuous output of fluid from the double action infusion pump, wherein the piston is reciprocated along an intermediate segment of the cylinder and through top and bottom zones (406, 408), and along the intermediate segment of the cylinder the reciprocating motor moves the piston at a first piston speed, the infusion system being characterized in that within the top and bottom zones (406, 408) the reciprocating motor moves the piston at a second piston speed greater than the first piston speed, such that the continuous output of the double action pump provides or approaches a static flow rate, and the continuous infusion flow from the one or more infusion ports similarly provides or approaches a static flow rate. a cylinder, a reciprocating piston received within the cylinder, the reciprocating piston separating a first pump chamber from a second pump chamber of the cylinder, each of the first and second pump chambers (300, 302) having a variable volume, a reciprocating motor coupled with the reciprocating piston, and the first and second pump chambers (300, 302) alternate between filling and evacuating conditions with reciprocation of the reciprocating piston through operation of the reciprocating motor, and the speed of reciprocation is varied to provide a continuous output of fluid between the first and second pump chambers (300, 302); and a catheter coupled with the double action infusion pump, the catheter including one or more infusion ports near a catheter distal portion (500; 600), and the one or more infusion ports (112; 508; 604) receive and expel the continuous output of fluid from the double action infusion pump, wherein the piston is reciprocated along an intermediate segment of the cylinder and through top and bottom zones (406, 408), and along the intermediate segment of the cylinder the reciprocating motor moves the piston at a first piston speed, the infusion system being characterized in that within the top and bottom zones (406, 408) the reciprocating motor moves the piston at a second piston speed greater than the first piston speed, such that the continuous output of the double action pump provides or approaches a static flow rate, and the continuous infusion flow from the one or more infusion ports similarly provides or approaches a static flow rate.