Methods and devices for vascular access

Abstract

Methods and devices to facilitate positioning of a catheter into a vessel. Devices include axially concentric assemblies of a piercing needle and a dilator that guides an outer catheter into a vessel, such as a blood vessel. The assemblies described herein can include retraction mechanisms and/or lock mechanisms to control needle positioning during catheterization processes as well as improved valves that prevent leakage of fluid from the proximal end of the devices. The devices and method include the use of novel valves to prevent undesired leakage of fluids through the proximal end of the catheter.

1 . A needle assembly comprising:
 a housing having a projection located therein;   a first tubular member having a first hub slidably engaged with the housing;   a needle having a needle hub, the needle extending through the first tubular member, the needle hub positioned within the assembly housing, the needle hub including a stop material positioned in a fluid path of the needle hub such that fluids passing through the needle into the needle hub contacts the stop material;   a biasing element in contact with the needle hub applying a biasing force against the needle hub;   where the needle assembly comprises an unloaded configuration where the stop material and the projection are adjacent without the biasing force acting therebetween;   where the first hub and needle hub are moveable relative to each other to assume a loaded configuration where the biasing force drives the needle hub proximally to force the stop material against the projection such that the stop material prevents further proximal movement of the needle hub; and   wherein when fluid in the needle hub contacts the stop material, the stop material weakens causing proximal movement of the needle hub such that a distal end of the needle retracts within the first tubular member.