A vascular access device may comprise a thin polymer patch configured to be attached to a wall of a vein. The vascular access device may also include a main body including a first end and a second end. The main body may have an inner surface defining a cavity extending between openings at the first and second ends along an axis. The first end of the main body may be connected to the polymer patch, and the cavity may taper between the second end and the first end. The vascular access device may include a cap connected to the second end of the main body. The vascular access device may also include a fluid sealed within the cavity. When the vascular access device is implanted in a patient and a dialysis needle is received in the cavity, the needle may be guided by the inner surface toward the wall of the vein.