An electrosurgical instrument includes an elongated first shaft fabricated from thermally-conductive plastic material, an elongated second shaft, and opposing first and second jaw members each having a proximal end portion coupled to a distal end portion of the respective first and second shafts. One or both of the jaw members has a jaw frame and an electrically-conductive tissue sealing structure disposed over the jaw frame. The first shaft has a heat sink disposed therein configured to dissipate heat from the tissue sealing structure toward the thermally-conductive plastic material.
