A multi-lumen intravenous catheter comprising: an elongated body portion having an outer wall (301, 401) extending longitudinally between proximal and distal ends, wherein: two septa (304, 404) extend longitudinally through the elongated body portion, wherein the two septa (304, 404) and the outer wall (301, 401) define a central lumen (303, 403) and two side lumens (302, 404), and the central lumen has an oblong shape in cross section and is positioned between the two side lumens (302, 402); and a plurality of extension tubes, each having a first end and a second end, extending longitudinally away from the proximal end of the body portion, wherein the first ends of the extension tubes connect to the proximal end of the body portion, the central lumen (303, 403) and the two side lumens (302, 402) each form a fluid tight connection to a respective extension tube, characterized in that: the central lumen has planar side surfaces, a rounded top, a rounded bottom, each of the side lumens (302, 304) have a "D" shape in cross section, at least one of the side lumen (302, 304) is configured to receive a guide wire, each of the two septa (304, 404) are configured to flex when the central lumen (303, 403) is under pressure generated by injection of fluid there-through, whereby a cross sectional area of the central lumen (303, 403) resultantly increases to increase flow capacity through the central lumen (303, 403), each of the two septa (304, 404) have less mechanical strength than the outer wall (301, 401), whereby catheter rupture will occur in one or both of the septa (304, 404) prior to in the outer wall (301, 401), and when a breach in one or both septa (304, 404) occurs, the fluid within the central lumen (303, 403) therefore leaks into one of the two side lumen (302, 402). an elongated body portion having an outer wall (301, 401) extending longitudinally between proximal and distal ends, wherein: two septa (304, 404) extend longitudinally through the elongated body portion, wherein the two septa (304, 404) and the outer wall (301, 401) define a central lumen (303, 403) and two side lumens (302, 404), and the central lumen has an oblong shape in cross section and is positioned between the two side lumens (302, 402); and two septa (304, 404) extend longitudinally through the elongated body portion, wherein the two septa (304, 404) and the outer wall (301, 401) define a central lumen (303, 403) and two side lumens (302, 404), and the central lumen has an oblong shape in cross section and is positioned between the two side lumens (302, 402); and a plurality of extension tubes, each having a first end and a second end, extending longitudinally away from the proximal end of the body portion, wherein the first ends of the extension tubes connect to the proximal end of the body portion, the central lumen (303, 403) and the two side lumens (302, 402) each form a fluid tight connection to a respective extension tube, characterized in that: the central lumen has planar side surfaces, a rounded top, a rounded bottom, each of the side lumens (302, 304) have a "D" shape in cross section, at least one of the side lumen (302, 304) is configured to receive a guide wire, each of the two septa (304, 404) are configured to flex when the central lumen (303, 403) is under pressure generated by injection of fluid there-through, whereby a cross sectional area of the central lumen (303, 403) resultantly increases to increase flow capacity through the central lumen (303, 403), each of the two septa (304, 404) have less mechanical strength than the outer wall (301, 401), whereby catheter rupture will occur in one or both of the septa (304, 404) prior to in the outer wall (301, 401), and when a breach in one or both septa (304, 404) occurs, the fluid within the central lumen (303, 403) therefore leaks into one of the two side lumen (302, 402). the central lumen has planar side surfaces, a rounded top, a rounded bottom, each of the side lumens (302, 304) have a "D" shape in cross section, at least one of the side lumen (302, 304) is configured to receive a guide wire, each of the two septa (304, 404) are configured to flex when the central lumen (303, 403) is under pressure generated by injection of fluid there-through, whereby a cross sectional area of the central lumen (303, 403) resultantly increases to increase flow capacity through the central lumen (303, 403), each of the two septa (304, 404) have less mechanical strength than the outer wall (301, 401), whereby catheter rupture will occur in one or both of the septa (304, 404) prior to in the outer wall (301, 401), and when a breach in one or both septa (304, 404) occurs, the fluid within the central lumen (303, 403) therefore leaks into one of the two side lumen (302, 402).