Detection of large vessels during parenchymal dissection using a smart blade

An ultrasonic surgical instrument comprising:

• an ultrasonic electromechanical system comprising a clamp arm and an ultrasonic blade coupled to an ultrasonic transducer via an ultrasonic waveguide;
• and
• a generator configured to supply power to the ultrasonic transducer, wherein the generator comprises a control circuit having a memory circuit and is configured to:
• apply energy to the ultrasonic blade at a first power, current, or voltage via the ultrasonic transducer coupled to the ultrasonic blade;
• measure a complex impedance of the ultrasonic transducer;
• receive a complex impedance feedback data point;
• compare the complex impedance feedback data point to a reference complex impedance characteristic pattern disposed in the memory circuit;
• and
• determine that the ultrasonic blade is contacting a vessel based on the comparison,
• wherein the reference complex impedance characteristic pattern comprises a complex impedance characteristic pattern of a chamois subject to a sub-therapeutic ultrasonic energy.