Energy-based surgical instruments incorporating cooling features

An ultrasonic surgical instrument includes an ultrasonic waveguide defining a blade at a distal end portion thereof. The ultrasonic waveguide is configured to transmit ultrasonic energy therealong to the blade. The blade defines a plurality of surfaces. At least one lumen is defined at least partially through the blade. The at least one lumen establishes a flow path through the blade extending from a first open end on one surface of the plurality of surfaces to a second open end on a different surface of the plurality of surfaces. The at least one lumen is configured to urge fluid through the blade along the flow path from the one surface to the different surface.