An ultrasonic surgical instrument includes a waveguide defining a blade at a distal end thereof and a lumen extending through a portion of the blade. The blade is configured to receive ultrasonic energy for treating tissue. The instrument further includes first and second conduits each defining a proximal end and a distal end. The second conduit is coaxially disposed about the first conduit. The distal ends of the first and second conduits extend into the lumen. The distal end of the first conduit extends further distally into the lumen than the distal end of the second conduit.