Accuracy of the T-Line® Tensymeter® (Continuous Non-Invasive Blood Pressure Management Device) Versus Conventional Invasive Radial Artery Tonometry in Surgical Cases with Induced Hypotension

Peter Szmuk, M.D., Evan Pivalizza, M.D., Ralf Gebhard, M.D., Didier Sciard, M.D., Robert D. Warters, M.D. (Anesthesiology, University of Texas Medical School at Houston and Outcome Research Institute, Houston, TX)

Presented at the American Society of Anesthesiologists 2004 Annual Meeting. Las Vegas, NV. Anesthesiology. 2004;101:A545.

Introduction:

Measuring blood pressure (BP) with either invasive (AL) or noninvasive (NIBP) methods has disadvantages. NIBP measurements are intermittent, which may lead to delayed intervention or to nerve damage during prolonged use, and are inaccurate at low pressures. AL measures may be associated with infection, thrombosis, pseudoaneurysms and distal embolization. The T-Line® Tensymeter continuous non-invasive BP device (Tensys® Medical, Inc.) circumvents the need for arterial cannulation, provided arterial blood samples are unnecessary. Pressures estimated by the T-Line® are similar to those from arterial catheters over a wide range of pressures and over time (1, 2). However, the system has yet to be formally evaluated during controlled hypotension. We thus tested the hypothesis that the T-Line® monitor is accurate during controlled hypotension.

Methods:

ASA I-III patients, age 18-70 years, scheduled for multilevel spinal surgery under general anesthesia were enrolled. We excluded patients without bilateral palpable radial pulses. The mean BP target was 55-65 mm Hg. Hypotension was induced with isoflurane or sevoflurane, nicardipine, and metoprolol and/or dexmedetomidine. An arterial catheter was inserted in one radial artery and the T-Line® positioned on the contralateral wrist. BP was recorded simultaneously before and after prone positioning. Data from both traces were sampled at 160 hz, imported into a Microsoft Excel database, and separated into 10-beat epochs for analysis. T-Line® data are expressed as mean error standard deviation for systolic, diastolic, and mean blood pressure (SBP, DBP, MBP) values for each epoch, then subjected to regression and Bland-Altman analyses compared to AL.

Results:

Fifteen patients (8 female, 7 male), were enrolled. Total recorded BP time was 1189 min (175 min per patient), with 471 min (31 min per patient) of deliberate hypotension. Mean pressures are presented in Table 2. Bland-Altman coefficient and regression pooled coefficient showed excellent correlation between the AL and T-Line® (Table 1). Mean error of SBP, DBP, and MBP were -0.5, 1.2, and 1.2 mm Hg for all measurements and 0.9, 0.3 and 0.4 mm Hg during hypotension.

Conclusions:

Our data confirms excellent correlation between BP measured by the T-Line® and arterial catheters in patients undergoing controlled hypotension.

References:

• Anesthesiology 2004;99: A-616.
• Anesth Analg 2004; 98; S-91
• Anesthesiology 2004; 101: A545

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