An surgical instrument configured to concurrently dissect and coagulatetissue. In anembodiment, the surgical instrument comprises a handle and a shaft extendingdistally from thehandle. The shaft includes an outer hypotube, a lumen coaxially-disposedwithin the hypotubeand extending beyond a distal end thereof, a coaxial feedline coaxially-disposed within thelumen, and having an inner conductor and an outer conductor disposed coaxiallyabout the innerconductor, and a coolant tube coaxially-disposed between the lumen and thecoaxial feedline toform an inflow conduit and an outflow conduit. The instrument further includesa dissectinghead assembly coupled to a distal end of the shaft. The dissecting headassembly includes adielectric core having a substantially planar radiating surface and at leastone non-radiatingsurface, a reflective coating disposed on the at least one non-radiatingsurface of the dielectriccore, and a blade extending from the radiating surface.
