ClearSight™ finger cuff versus invasive arterial pressure measurement in patients with body mass index above 45 kg/m2

Background Measuring blood pressure in patients with obesity is challenging. The ClearSight™ finger cuff (FC) uses the vascular unloading technique to provide continuous non-invasive blood pressure measurements. We aimed to test the agreement of the FC with invasive radial arterial monitoring (INV) in patients with obesity. Methods Participants had a body mass index (BMI) ≥45 kg/m2 and underwent laparoscopic bariatric surgery. FC and INV measurements were obtained simultaneously every 5 min on each patient, following induction of anesthesia. Agreement over time was assessed using modified Bland-Altman plots and error grid analysis permitted clinical interpretation of the results. Four-quadrant plots allowed assessment of concordance in blood pressure changes. Results The 30 participants had a median (IQR) BMI of 50.2 kg/m2 (IQR 48.3–55.3). The observed bias (SD, 95% limits of agreement) for systolic blood pressure (SBP) was 14.3 mmHg (14.1, -13.4 – 42.0), 5.2 mmHg (10.9, -16.0 – 26.5) for mean arterial pressure (MAP) and 2.6 mmHg (10.8, -18.6 – 23.8) for diastolic blood pressure (DBP). Error grid analysis showed that the proportion of readings in risk zones A-E were 90.8, 6.5, 2.7, 0 and 0% for SBP and 91.4, 4.3, 4.3, 0 and 0% for MAP, respectively. Discordance occurred in ≤8% of pairs for consecutive change in SBP, MAP and DBP. Conclusions The vascular unloading technique was not adequately in agreement with radial arterial monitoring. Evaluation in a larger sample is required before recommending this technique for intraoperative monitoring of patients with BMI ≥45 kg/m2.

Abstract WP344: Vascular Unloading Technique for Continuous Non-invasive Blood Pressure Monitoring After Intravenous Thrombolysis in Acute Ischemic Stroke: Interim Analysis of a Prospective Method Comparison Study

Introduction: Elevated arterial blood pressure (BP) increases the risk of intracerebral hemorrhage after intravenous (IV) thrombolysis with tPA in acute ischemic stroke (AIS). While arterial BP is usually monitored using intermittent oscillometric measurements with an upper arm cuff, the vascular unloading technique (VUT) provides non-invasive continuous BP monitoring with a finger cuff. Hypothesis: We hypothesized that VUT monitoring is feasible in AIS patients receiving IV tPA, is comparable to the standard technique, and allows detection of BP peaks that might be missed in oscillometric BP monitoring. Methods: We performed an interim analysis of an ongoing prospective method comparison study. AIS patients were simultaneously monitored over 24 h following IV tPA bolus using VUT and contralateral oscillometric BP assessment every 30 min. Results: We present interim data from 15 out of 24 AIS (4 m, 11 f; aged 72.5±14.9 y, mean±SD) receiving IV tPA. Nominal significance level was set to 0.029 in accordance with Pocock’s rule. Missing data were less than 5% for both techniques. There was a positive correlation between VUT and oscillometric BP assessment (Pearson’s correlation coefficient r=0.91, p<0.001 for systolic BP; and r=0.88, p<0.001 for diastolic BP). Bland-Altman analysis confirmed this agreement (figure 1). The mean difference between VUT and oscillometric BP measurements was 9.4±6.1 mmHg for systolic, and 4.5±3.0 mmHg for diastolic BP (p=n.s.). Peaks (systolic BP>180 or diastolic BP>110 mmHg) were detected by VUT monitoring (at least one episode≥5 min) in 12 patients, and by oscillometric BP assessment (≥one time point of measurement) in 7 patients (p<0.01). Conclusions: Our interim data suggest that VUT-based BP monitoring is feasible in AIS patients receiving IV tPA, and might be more sensitive than intermittent oscillometric BP assessment in detecting potentially harmful blood pressure peaks. Figure 1: Bland Altman plot