A surgical instrument comprises: an elongated sheath, an energy probe, an elongated energy conductor, and an elongated cooling member. The energy probe is connected to the distal end portion of the sheath. The elongated energy conductor is contained within the sheath and arranged to transmit distally to the energy probe energy from an energy source. The elongated cooling member is reciprocally movable within the sheath and thermally coupled at its proximal portion to a cooler. The cooling member is movable between a proximal, non-cooling position and a distal, cooling position. In the non-cooling position, a distal end of the cooling member is displaced proximally from the energy probe so as to impede thermal conduction therebetween; in the cooling position, the distal end of the cooling member thermally contacts the energy probe so as to facilitate thermal conduction therebetween.