A surgical instrument includes a pair of jaw members moveable between a spaced-apart and an approximated position. A drive bar is translatable between a distal and a proximal position for moving the jaw members between the spaced-apart and approximated positions. A lever is moveable between an initial position and an actuated position for translating the drive bar between the distal and proximal positions. A sleeve disposed about the drive bar includes an annular track having a substantially radial segment(s) and a substantially longitudinal segment(s). A collar interdisposed between the sleeve and the drive bar includes a stop member(s) extending radially outwardly therefrom. The stop member(s) is engaged within the track and is translatable from a first position, wherein the stop member is positioned within the longitudinal segment, to a second position, wherein the stop member is engaged within the radial segment, to lock the lever in the actuated position.