A surgical system includes an ultrasonic surgical instrument and a cooling module. The instrument includes a waveguide defining a blade and having a lumen, an inflow conduit disposed in communication with the lumen and configured to supply fluid to the lumen, and a return conduit disposed in communication with the lumen and configured to receive fluid from the lumen. The cooling module includes a pump assembly operably coupled to the inflow and return conduits and configured to pump fluid through the inflow conduit, into the lumen, and back through the return conduit for cooling the blade. The cooling module also includes at least one sensor configured to sense a property of the fluid pumped into the inflow conduit and/or a property of the fluid returned from the return conduit, and a controller configured to control the pump assembly according to the sensed property(s).
