Transducer offset by electrocautery resulting in erroneous blood pressure measurement.

During a coronary artery bypass operation arterial blood pressure measured with a Bentley Trantec model 800 transducer increased erroneously while continuous electrocautery was being used. This phenomenon has recurred infrequently, with fictitious hypotension being observed in one patient. To reproduce the problem of pressure offset during electrosurgery a bench test demonstrated that with peak to peak voltage of 20 volts from the electrosurgical unit, three of seven Bentley transducers had offsets as much as +/- 50 mmHg. It is important for anaesthetists to determine if electrosurgery units are functioning before treating apparent pressure drifts.