Abstract: The invention relates to a device that can be used to monitor the penetration of a penetration member into anatomical structures and, in particular, bone structures of a living body, the structures having at least two different electrical impedance areas. The device is characterized in that it comprises: at least one impedance meter which can be connected to at least two electrodes, at least one of the electrodes being located at a distal end of the penetration member; and at least one alert device which can produce an alert signal if the impedance meter detects an impedance variation. The invention also relates to a penetration member for the device and to an electronic board for the device.

Abstract: A method and apparatus for continuously sampling plasma are disclosed. The method of the present invention comprises removing blood from the patient, separating a substantially small portion of plasma, and returning the blood to the patient. The removing, separating, and returning steps are performed continuously and simultaneously with each other. The apparatus of the present invention relates to a double-lumen cannula or venipuncture needle for the removal and returning of blood to the patient at the same site.