A surgical instrument comprises, in accordance with the present invention, an elongate probe, a sleeve, a sleeve extension and at least one cauterization electrode. The probe is an ultrasonic element, serving to convey ultrasonic vibrations (as standing waves) to organic tissues at a surgical site. The probe has a working tip and a longitudinal axis. The sleeve surrounds the probe with the working tip of the probe projecting from a distal or free end of the sleeve. The sleeve extension is disposed at the distal or free end of the sleeve and defines a multiplicity of apertures having respective axes oriented at least substantially parallel to the longitudinal axis. The electrode has a distal or free end removably inserted through one of the apertures.