An apparatus for selectively measuring central venous pressure and effecting hyperalimentation through a single catheter inserted into a central vein of the patient. The apparatus includes a manometer, a first selector valve connected to an upper portion of the manometer tube, a hyperalimentation fluid supply connected to the valve, a sterile air supply connected to the valve, a second selector valve connected to a lower end portion of the manometer tube, a waste container connected to the second selector valve, and a catheter connected to the second selector valve. The first selector valve is arranged to connect alternatively the hyperalimentation fluid supply or the sterile air supply to the upper end portion of the manometer tube, and the second selector valve is arranged to connect alternatively the lower end portion of the manometer tube selectively to the waste container or the catheter. A check valve may be connected between the waste container and the second selector valve and an isolation valve may be connected between the catheter and the second selector valve. A lock is provided for locking the catheter to the connection to the second selector valve. The selector valves in the illustrated embodiment are defined by two-way stopcocks. The apparatus is completely closed at all times relative to the ambient atmosphere.