An electro-chemical surgical knife is detailed that in a single instrument provides both a chemically assisted mechanical dissector and an electrical knife. The chemically assisted mechanical dissector: includes a conductive mechanical instrument, a source (7) of a cleavage solution, a pump (8) for feeding the cleavage solution to, a channel (2) for transporting the cleavage solution to an operating location, and a flow controller (8c) for controlling the feeding of the cleavage solution by the pump to an inlet of the channel. The electric knife includes a source of high frequency AC electrical power (5) for feeding AC current through an electric conductor (3) to, an electrode (6) formed by the conductive mechanical instrument and further comprises a second controller (5c) for controlling the feeding of the AC current to the electrode.