In the case of an instrument (10) for coagulation and fusion as well as for severing vessels, provision is made for two shanks (19, 20), between which a vessel is to be gripped and fused. A blade (21) for severing the coagulated and fused vessel is provided with an isolator (40), which isolates the blade (21) against at least one of the electrodes or shanks (19, 20), respectively. On the other hand, the blade (21) is preferably in mechanical contact with at least one of the electrodes or shanks (19, 20), respectively, so that a safe separation of the fused biological tissue or vessel, respectively, is attained. This concept can be used to increase the safety of surgery and to miniaturize the tool (18) towards smaller sizes.
