Comparison of NIBP with T-Line® Tensymeter (Continuous NIBP Device) for BP Concordance in ASA II-IV Patients

Leslie C. Jameson, M.D., Colleen K. Dingmann, R.N., Ph.D. (Anesthesiology, University of Colorado Health Science Center, School of Medicine, Denver, CO)

Presented at the American Society of Anesthesiologists 2004 Annual Meeting. Las Vegas, NV. Anesthesiology. 2004;101:A552.

Indications for continuous BP monitoring are unclear. An intraarterial catheter (A-line) is often not placed in low risk surgical procedures or ASA status II-IV patients even though a continuous BP may be a valuable management tool. In ASA II-IV patients, it is unknown whether there are significant perturbations in BP that go undetected by intermittent NIBP. T-Line® Tensymeter® (Tensys® Medical, Inc, San Diego, CA) has been shown to provide A-Line equivalent BP monitoring.¹ This study compares concordance (reporting physiologically equivalent values) of NIBP and T-Line® in detecting hypo/hypertension in middle aged patients receiving elective general anesthesia.

Methods:

With IRB approval and informed consent, 21 patients ≥45 years old with ≥ 1 co-morbid conditions who were to be monitored with a standard NIBP (Solar 9500, GE Medical) during general anesthesia provided ad lib by an anesthesia care team. T-Line® was placed in the OR prior to induction and beat to beat digital values recorded by a company provided proprietary program. NIBP values, iv drugs, and volatile anesthetics were simultaneously recorded into the computer (VAIO, Sony). The caregiver was blinded to T-Line® values. Hypo/hypertensive episodes were a BP change BP of ±20% of normal BP (average of 3 NIBP values on each arm preoperatively) or an absolute values of: Systolic - 160 mm Hg, 80 mm Hg; Mean -110 mm Hg, 50 mm Hg whichever was greater. Episodes of difference, [NIBP - T-Line®] were counted and total time for each recorded. All episodes were ≥ 1 min. Differences were categorized as Systolic: ±20-29, ±30-39, ±40+ mm Hg, Mean ±10-19, ±20-29, ±30+ mm Hg. Statistical analysis significance p≤0.05 using t-test.

Results:

Patient Demographics: gender 5M/16F; Age 58.9± 7.6 (50-79) yrs; surgical procedures: 14 General, 3 Orthopedic, 4 Other. Analysis was performed on 19 patients and 2 were withdrawn because of the unblinding of the caregiver due to critical hypotension and NIBP failure. Comorbidities included hypertension (62%), BMI>38 kg/m² (54%), CV (18%), DM (23%). Induction was recorded in 7%; 43.6 hrs of anesthesia were analyzed (2.3±1.0 hr/patient). Anesthetic technique included all volatile anesthetics, fentanyl, vecuronium, and O₂. T-Line® reported systolic BP (sBP) above NIBP 2.3±2.9 episodes/hr/pt [range 0.4-9.0] (ep/hr); 7.6±11.4 (range 0.7-40.6) min/hr/pt and below NIBP 12.2±13.6 [.8-42.9] ep/hr/pt, 22±27.7 [.8-47.8] min/hr/pt. Comparable mean BP values are above NIBP 4.4±8.5 [.2-25] ep/hr/pt; 11.5±12 [.9-22] min/hr/pt and 4.2±3.7 [3-45] ep/hr/pt; 13.7±12 [3-13.2] min/hr/pt. There was discordant data when either the T-Line® or the NIBP reported hypo or hypertension that did not occur in the other monitor. Concordant values were when both monitors reported BP change of similar magnitude and the same direction. There was significantly more discordant than concordant periods/patient and time/patient.

Reference:

• Anesthesiology 2004; 101: A552