Non-invasive continuous arterial pressure and pulse pressure variation measured with Nexfin(®) in patients following major upper abdominal surgery: a comparative study.
BACKGROUND Standard non-invasive arterial pressure (AP) measurements are discontinuous. By providing non-invasive beat-to-beat AP measurements, Nexfin™ might limit duration of intraoperative hypotension and hypertension. We assessed the ability of Nexfin™ to detect AP variations by comparing its trending ability with invasive AP monitoring. METHODS Thirty-one subjects undergoing elective surgery under general anaesthesia were included. During induction, simultaneous pairs of AP measurements were collected every 5 s from the Nexfin™ finger sensor and a homolateral radial artery catheter. Magnitude and time lags of AP variations from baseline to nadir and peak were calculated for both methods. Concordance analysis was performed by the Bland-Altman method (for comparison of repeated measures when appropriate). RESULTS Nexfin™ detected 100% of AP changes with the median delays of 0 s (-13 to 7) and 0 s (-5 to 12) for nadir and peak, respectively. Bias [limits of agreement (LOA)] of systolic AP (SAP) variations was -0.5 mm Hg (-31.2 to 30.2) and -9.4 mm Hg (-31.3 to 12.6) from baseline to nadir and from baseline to peak, respectively. For 3479 analysed paired measurements, bias was -3.8 and -8.8 mm Hg for SAP and diastolic AP, with LOA of (-36.0 to 28.5) and (-29.8 to 12.3), respectively. CONCLUSIONS Nexfin™ detects AP variations accurately and can be a useful warning device during anaesthesia. However, it is not interchangeable with invasive monitoring, given the large LOA between the two measurements. CLINICAL TRIAL REGISTRATION NCT01658631.