Overestimation of Blood Pressure from an Arterial Pressure Line

A 54-yr-old male (American Society of Anesthesiologists physical status 3) is scheduled to undergo an Automatic Internal Cardiac Defibrillator change under general anesthesia. His history is remarkable for coronary artery disease, hypertension, and insulin-dependent diabetes mellitus. He is 104 kg and 5′5″. You meet him in the catheterization laboratory. As usual, the place is in partial darkness. You place noninvasive monitors. A right radial arterial line is secured before induction of anesthesia (Transpac IV monitoring kit; 84″ disposable transducers with a 3-ml squeeze flush; Abbott Critical Care System; Abbott Laboratory, North Chicago, IL). A seemingly normal arterial waveform is present with a blood pressure of 149/116 mmHg and a mean of 129 mmHg. A simultaneous noninvasive blood pressure of 105/70 with a mean of 82 mmHg is obtained in the left arm. You change the non-invasive cuff to the right arm and get the same reading as in the left arm. The transducer is located in the midaxillary line and has been zeroed by you just before the arterial line was placed. Because you have just zeroed the transducer, you dismiss that as a cause for this difference in blood pressure reading. Furthermore, you did not see any off-set when the stopcock was opened to atmosphere?