A surgical system includes a surgical instrument and a cooling module. The cooling module includes a fluid reservoir retaining a conductive cooling fluid, a pump configured to pump the conductive cooling fluid along a flowpath, first and second electrodes disposed at first and second positions along the flowpath and configured to sense an electrical property of the conductive cooling fluid at the first and second positions, and a controller configured to determine an impedance of the conductive cooling fluid between the first and second positions based upon the sensed electrical properties of the first and second electrodes. A method for cooling a surgical instrument includes detecting an electrical property of a conductive cooling fluid at first and second positions along a flowpath and determining an impedance of the conductive cooling fluid between the first and second positions based upon the detected electrical properties at the first and second positions.