Abstract: A method of extracorporeal treatment using a venous return catheter containing a stiffening member disposed therein is provided.

Abstract: A multilumen catheter comprises separate proximal IV tubes of substantially circular cross-section welded in fluid communication with each of the substantially eliptical-shaped lumens of the catheter. The weld, at the interface between the outer surface of each IV tube and the associated lumen sidewall, is continuous over the interface to provide for an integral fluid sealing connection between the catheter lumen and the IV tube.

Abstract: A device for welding an IV tube into fluid communication with a lumen of a catheter comprises a grounded metal adapter which is operatively associated with a dielectric collet to clampingly engage and hold a catheter in the collet. The device further comprises a metal mandrel which is partially inserted into an IV tube and positioned so that part of the IV tube and mandrel extend into a portion of a lumen of the catheter. With the IV tube and mandrel positioned in the lumen, the dielectric collet is further engaged to compressingly urge the lumen sidewall into contact with the outer surface of the IV tube. RF energy is then applied to the mandrel to weld the IV tube into the lumen.