Continuous Noninvasive Arterial Pressure Monitoring Using the Vascular Unloading Technique (CNAP System) in Obese Patients During Laparoscopic Bariatric Operations

BACKGROUND: Increasing rates of obesity create new challenges for hemodynamic monitoring in the perioperative phase. Continuous monitoring of arterial pressure (AP) is important in severely obese patients who are at particular risk for cardiovascular complications. Innovative technologies for continuous noninvasive AP monitoring are now available. In this study, we aimed to compare continuous noninvasive AP measurements using the vascular unloading technique (CNAP system; CNSystems, Graz, Austria) compared with invasive AP measurements (radial arterial catheter) in severely obese patients during laparoscopic bariatric surgery. METHODS: In 29 severely obese patients (mean body mass index 48.1 kg/m2), we simultaneously recorded noninvasive and invasive AP measurements over a period of 45 minutes and averaged the measurements using 10-second episodes. We compared noninvasive (test method) and invasive (reference method) AP measurements using Bland-Altman analysis and 4-quadrant plot/concordance analysis (2-minute interval). RESULTS: We observed a mean of the differences (±SD, 95% limits of agreement) between the AP values obtained by the CNAP system and the invasively assessed AP values of 7.9 mm Hg (±9.6 mm Hg, −11.2 to 27.0 mm Hg) for mean AP, 4.8 mm Hg (±15.8 mm Hg, −26.5 to 36.0 mm Hg) for systolic AP, and 9.5 mm Hg (±10.3 mm Hg, −10.9 to 29.9 mm Hg) for diastolic AP, respectively. The concordance rate was 97.5% for mean AP, 95.0% for systolic AP, and 96.7% for diastolic AP, respectively. CONCLUSIONS: In the setting of laparoscopic bariatric surgery, continuous noninvasive AP monitoring with the CNAP system showed good trending capabilities compared with continuous invasive AP measurements obtained with a radial arterial catheter. However, absolute CNAP- and arterial catheter–derived AP values were not interchangeable. Accepted for publication September 27, 2017. Funding: CNSystems Medizintechnik AG (Graz, Austria) provided the technical equipment for the study. CNSystems Medizintechnik AG was not involved in the collection of the data, drafting of the manuscript, or decision to submit the manuscript for publication. Conflicts of Interest: See Disclosures at the end of the article. Reprints will not be available from the authors. Address correspondence to Dorothea E. Rogge, MD, Department of Anesthesiology, Centre of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany. Address e-mail to d.rogge@uke.de. © 2017 International Anesthesia Research Society

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