A Comparison of the T-Line® Tensymeter Device vs Direct Radial Arterial Pressure during Major Surgery

Thomas Bellehumeur, M.D., James Ramsay, M.D. (Department of Anesthesiology, Emory University School of Medicine, Atlanta, GA)

Presented at the American Society of Anesthesiologists 2004 Annual Meeting. Las Vegas, NV. Anesthesiology. 2004;101:A536.

Continuous blood pressure monitoring has traditionally required a fluid-filled intra-arterial catheter connected to a transducer. A noninvasive transcutaneous sensor-transducer system has recently been introduced (the T-Line® Radial Artery Sensor; Tensys® Medical Inc., San Diego, CA). We compared the continuous blood pressure data from this new device to the invasive arterial pressure from the contra-lateral radial artery during a variety of major surgical procedures at risk for significant perioperative hemodynamic instability.

Methods:

With Human Investigations Committee approval and informed consent, patients undergoing procedures where placement of a radial arterial catheter was anticipated were studied. The wrist was examined before sensor placement, immediately after removal, and one hour after removal. Simultaneous signals from the study device transducer and the invasive transducer were sampled at 160 Hz into a laptop computer and processed identically. Systolic, diastolic and mean (S, D & M) values were passed through a 7-beat median filter to exclude single beat artifact. Data were then grouped into 10-beat epochs, and sampled for two consecutive minutes every 5 min, giving 24 min. of data per hour of sampling. Paired error values for all 3 pressures during each 10-beat epoch were analyzed using linear regression and Bland-Altman analysis.

Results:

Informed consent was obtained from 27 patients; in one the arm was not accessible during surgery and in 5 no arterial catheter was placed. Mean monitoring time in the remaining 21 patients was 137 min (range 20 to 242 min). The mean number of 10-beat epochs analyzed per patient was 319 (range 58 to 672). Mean and standard deviations for the paired error measurements for S, D & M were -0.6±5.4, 0.4±6.2 and -3.5±6.9 mm Hg respectively. Pooled linear regression R2 values from these data are 0.993, 0.953 and 0.929 for S, D & M respectively. The overall statistical performance and a Bland-Altman plot for mean pressure for all 21 patients are shown. Apart from mild indentation of the skin which resolved less than 1 hour after sensor removal, there were no adverse effects.

Discussion:

The noninvasive study system reliably provides an arterial waveform, S, D, & M pressures that compare very favorably to those obtained from a radial artery catheter without the attendant potential risks associated with arterial cannulation. No adverse events were evident after up to 242 min. of placement during surgery. Specifically noted was the ability of the T-Line® to track the intra-arterial reference during periods of significant hemodynamic instability without requiring external calibration. This novel device is a useful addition to perioperative blood pressure monitoring where arterial blood gas analysis is not required.

Copyright © 2005, American Society of Anesthesiologists. All rights reserved.